Systemic administration of intact, bacterially derived minicells results in rapid accumulation of the minicells in the microenvironment of a brain tumor, in therapeutically significant concentrations, without requiring endothelial endocytosis/transcytosis across the blood brain barrier or any other mechanism by which, pursuant to conventional approaches, nanoparticles have entered into that microenvironment. Accordingly, a wide variety of brain tumors, both primary and metastatic, can be treated by administering systemically a therapeutically effective amount of a composition comprised of a plurality of such minicells, each minicell being a vehicle for an active agent against the tumor, such as a radionuclide, a functional nucleic acid or a plasmid encoding one, or a chemotherapeutic agent.

Primary brain tumors consist of a diverse group of neoplasms, derived from various different cell lineages. Pursuant to a World Health Organization categorization (Louis et al., 2007), tumors of the central nervous system are classified as astrocytic, oligodendroglial, or mixed (oligoastrocytic). These tumors are further classified by subtypes and are graded, based on histology, from I to IV, with grade IV being the most aggressive. Glioblastoma multiforme (GBM), the most aggressive form of primary malignant brain tumor, accounts for approximately 45% to 50% of all primary brain tumors (Wrensch et al., 2002; Behin et al., 2003) and represents the second largest cause of cancer death in adults under 35 years of age (Allard et al., 2009).
Despite numerous therapeutic efforts, including cytoreductive surgery, radiation therapy and chemotherapy, the prognosis for glioma patients remains very poor (Stewart, 2002; Stupp et al., 2005). A majority eventually develop recurrent and progressive disease, after which the median survival is approximately 6 months (Wong et al., 1999; Lamborn et al., 2008). Median survival for GBM patients is about 12-14 months (Stupp et al., 2005).
In addition, brain metastasis from primary tumors such as breast, lung, and skin (melanoma) is a significant and growing public health problem. An estimated 250,000 patients in the United States were diagnosed with brain metastases in 2009 (Fox et al., 2011), which is more than 10-fold greater than the incidence of primary brain tumors (Jemal et al., 2009). The prognosis for patients with brain metastases is very poor, and most patients live only 4-6 months after diagnosis. Current treatment regimens provide marginal survival benefits (Eichler and Loeffler, 2007).
Complete surgical resection of gliomas is almost impossible, due to their diffusely infiltrative nature and proximity to vital brain structures. Systemic therapy also is limited, by virtue of the so-called blood brain barrier (BBB). See, generally, Cecchelli et al. (2007).
This barrier resides within the brain's capillary endothelium, and it has been an object of study for over 100 years. Indeed, the fact that most drug candidates for brain tumors never make it to the clinic (Pardridge, 2007) is attributable largely to their inability to cross the BBB and reach levels having a therapeutic effect (Groothuis, 2000).
Despite extensive efforts over several decades, the curative rates in the treatment of brain cancers remain abysmal. Brain cancer treatment thus represents one of the biggest challenges in oncology. Furthermore, the prevailing consensus is that the BBB is the major limiting factor in drug delivery into brain tumors.
Accordingly, considerable effort is directed globally to discovering and developing new drugs that are small enough to cross the BBB and improve the survival outcome for GBM patients. In addition, techniques are under development to transport drugs past the BBB and into the brain tumor microenvironment.
Among the approaches that have been studied, in an attempt to circumvent the BBB limitation, are the following.                Hyperosmotic BBB disruption (Kroll and Neuwelt, 1998).        Chemical barrier modification (Black et al., 1997).        Attempts to link therapeutic agents to compounds that have transporters across the BBB (Bickel et al., 2001; Zhang and Pardridge, 2007).        Direct administration of drugs into and around brain tumors (Hassenbusch et al., 2002; Hau et al., 2002; Reardon et al., 2002; Weber et al., 2002). This approach entails placement of drug-loaded wafers around a tumor resection bed, infusion of agents into or around a tumor resection cavity, or direct infusion of drugs into the tumor mass.        Convection-Enhanced Delivery or "CED" (Bobo et al., 1994; Morrison et al., 1994; Hadjipanayis et al., 2008; Hadjipanayis et al., 2010). In CED a small hydrostatic pressure differential is imposed by a syringe pump to distribute infusate directly to regions of the central nervous system (CNS). CED is a minimally invasive surgical procedure that provides fluid convection in the brain by a pressure gradient, which bypasses the BBB. Therapeutic agents can be delivered into the brain with a minimum of the toxicity, therefore, as well as to normal tissue and to organs commonly accessed by systemic delivery.

This patent is subject to a terminal disclaimer.

Bacterially derived, intact minicells for delivery of therapeutic agents to brain tumors


A method for treating an outdoor article, wherein a surface treating agent comprising a medium (B) containing a tetraalkoxysilane or a silane compound having a silanol group obtained by hydrolyzing an oligomer of such a tetraalkoxy silane (A), wherein the content of (A) is from 0.01 to 100 parts by weight per 100 parts by weight of (B), is used, and a thin film is formed by treating a hydrophobic synthetic resin coating film surface of the outdoor article with such a surface treating agent. It is thereby possible to prevent formation of a streak soils which are likely to form at a portion where rain water collects and runs down, such as below a window frame of a building.

Heretofore, it has been common to apply surface coating such as coating with a synthetic resin coating material to articles such as metals, inorganic materials, plastics, wood materials, papers, leathers or fibers to form a hydrophobic synthetic resin coating film on their surface for the purposes of their protection, imparting an artistic effect, imparting a functional property, etc.
Recently, as a coating material excellent in weather resistance, a fluoropolymer coating material is used in many cases. Such a fluoropolymer coating material shows a remarkably high weather resistance as compared with prior synthetic resin coating materials. However, soils deposited on its surface are of the same level as in the case of other synthetic resin coating materials, and an improvement in this respect is desired as a high performance commercial product.
Especially, with an article having a hydrophobic synthetic resin coating film, which is used outdoor (hereinafter referred to as an outdoor article), spot-like soils due to rain water are likely to form on the hydrophobic synthetic resin coating film surface exposed to rain. Further, streak-like soils (hereinafter referred to as rain streak soils) are likely to form at a portion where rain water collects and runs down, such as below a window frame of a building. Such rain streak soils can easily be removed by cleaning. However, not only repeated cleaning is cumbersome, but also the cleaning operation is not easy in the case of a large size outdoor article such as a building. Accordingly, a coated outdoor article is desired which has a surface less susceptible to formation of rain streak soils.
Heretofore, to solve the formation of the soils on the surface of a coated article, a composition for a coating material has been proposed wherein a polymer having a polyfluorinated carbon chain and a hydrophilic group, is incorporated (Japanese Unexamined Patent Publication No. 198653/1989). However, the coating surface obtained by this composition for a coating material was not adequate with respect to the point of preventing formation of rain streak soils, although some effects for suppressing formation of spot-like soils due to rain water are observed.
The present inventors have found a surface treating agent which is effective particularly for preventing formation of rain streak soils on the surface of an outdoor article having a hydrophobic synthetic resin coating film surface. The present invention provides a method for treating the surface of the above mentioned outdoor article by means of such a surface treating agent and an outdoor article having the surface treated by such a method.

Method for treating the surface of an outdoor article


A method for processing parts for kitchen tools in order to protect the parts from scratches, includes sequentially: a nitridation step, optionally including a nitrocarburizing step, between 592 and 750° C. in order to promote the formation of a nitrogen austenite layer; and a processing step for promoting the conversion of at least a portion of the nitrogen austenite into a phase with reinforced hardness.

It is known to use different materials, or stacking of materials, to produce kitchen utensils: steel (alloyed or not), aluminum, stainless steel (that is to say, generally containing more than 11% chromium), copper or silver alloys in particular, with or without surface coatings such as polymer layers based on polytetrafluoroethylene (PTFE, distributed in particular under the trademark Teflon). Each material has its own advantages and drawbacks for this type of application.
Aluminum is very resistant to corrosion during steps of washing the utensils, including in a dishwasher with detergents, but on the other hand can easily be scratched and its non-stick properties are mediocre. For this reason it is often associated with a coating of polytetrafluoroethylene type.
Austenitic stainless steel (containing approximately 18% chromium and 10% nickel) also has good corrosion resistance and slightly better scratch resistance than aluminum. On the other hand, it is a poor heat conductor which does not facilitate the homogenization of temperature for cooking utensils such as woks, frying pans, griddles, casserole dishes, pots, broiler plates, fryers, grills (barbecues), molds or saucepans.
Copper is a very good heat conductor which is recognized for providing good quality cooking. However, it is an expensive material reserved for top of the range utensils.
Non-stainless steels have a great advantage over all the other aforementioned materials, which is their price. To be precise, steels, especially unalloyed steels (those without any added component) or weakly alloyed steels (that is to say in which no added component exceeds 5% by weight), are easily and abundantly available, their price is low and varies little relative to that of stainless steels or copper. It is for this reason that non-stainless steels are very widely used as the basic material for bottom of the range utensils.
However, these steels have very low corrosion resistance, especially on cleaning the utensils with detergents (washing in a dishwasher is ruled out), their surface is easily scratched and their non-stick properties are mediocre.
The teaching of patent US 2008/0118763 A1 shows that ferritic nitrocarburizing may be applied to kitchen utensils at a temperature of 1060° F. (571° C.) for 3 h in an atmosphere of 55% nitrogen, 41% ammonia and 4% CO2. Carried out next are gaseous oxidation (post-oxidation) at a temperature of 800° F. (˜427° C.) and temporary protection by baking at 500° F. (260° C.) for 45 minutes using a cooking oil. According to this document, the treated surfaces have increased hardness and improved corrosion resistance.
The treatments of nitriding, nitrocarburizing, oxinitriding and oxinitrocarburizing (the prefix oxi- means that after the nitriding or nitrocarburizing, an oxidizing step is carried out) are used in the mechanical industry (in the automotive sector: valves, gas struts, ball joints; in construction equipment: articulations, hydraulic jacks, etc.)
These treatments are carried out industrially either using gas (ammonia-based atmospheres) or using plasma (glow discharge at low pressure), or using liquid (ionic liquid media, see for example the document US2003084963).
In industry, the treatments of nitriding, nitrocarburizing, oxinitriding and oxinitrocarburizing are conventionally carried out in the ferritic phase (in the iron-nitrogen diagram), that is to say at temperatures less than 592° C.
A layer of iron nitride is formed, and the layer below is referred to as diffusion layer.
Beyond 592° C., the γN phase forms (nitrogen-containing austenite, generally named γN) between the nitride layer and the diffusion layer. Nitrogen-containing austenite is a microstructure that is particular to steel. The precise temperature beyond which the γN phase forms depends on the exact composition of the steel. If the latter contains a lot of alloying components, this temperature limit value may shift up to 600° C.
This nitrogen-containing austenite layer transforms into nitrogen-containing braunite, another microstructure particular to steel, under the effect of temperature at the oxidation step which is conventionally carried out after the nitriding or nitrocarburizing step. However, in the field of mechanical parts, the oxidation step is generally carried out since it is desired that the parts be corrosion resistant, nitriding increasing wear resistance and the oxidation increasing the corrosion resistance.
This retransformation into braunite is not generally desired since for the mechanical applications for which nitrocarburizing is generally destined, the presence of a nitrogen-containing braunite layer gives rise to fragility in case of impact.
More particularly, the typical mechanical stresses whose effect it is usually sought to limit by nitrocarburizing are cyclic stresses and/or alternating stresses which will recur with a high number of cycles, such as for example superficial fatigue or impact.
The presence of a braunite layer is thus generally ruled out since the fragility of that layer may lead to flaking or splitting of the nitride layer under the effect of impact (high energy transfer which is brief and localized between two parts moving relative to each other). Nitrocarburizing and nitriding are thus conventionally carried out in ferritic phase. When austenitic nitriding is carried out, the post-oxidation step is then generally performed at a temperature below 200° C. to avoid the retransformation of the nitrogen-containing austenite into braunite (see for example patent EP1180552).
Furthermore, with regard to the teaching of patent US 2008/0118763 A1, the applicant has noted that at the post-oxidation step carried out just after the nitrocarburizing, the high temperatures used (greater than 200° C.) give rise to tempering in the diffusion zone. The consequence of this annealing is a drop in the hardness of the diffusion zone which is detrimental to the scratch resistance of the kitchen utensils treated.
Consequently, when a load is applied which stresses the material in its core and not just the hard surface layer, the substrate deforms and the hard surface layer splits and flakes.
The same applies to the step of baking the temporary protective agent which is carried out between 150 and 260° C., as well as during the life of the utensils, at each utilization above 200° C. of those kitchen utensils.
This is in particular detrimental in the case of the low carbon steels which are generally used for kitchen utensils.
It is moreover to be noted that nitrocarburizing methods require a high energy input, and that it is desirable to control the treatment time, to limit the final costs. One of the drawbacks of the treatment range presented by document US 2008/0118763 A1 is its duration which is long (3 hours).
In this context, the problem which the invention sets out to solve is to give improved non-stick, scratch resistant and corrosion resistant properties to the surface of kitchen utensils made of steel (not alloyed or weakly alloyed), with improved production costs.

Method of treating parts for kitchen utensils


Embodiments in accordance with the present invention relate to the fabrication of packages for semiconductor devices, and in particular to the use of electroplating techniques to form features on the surface of a metal lead frame. In accordance with one embodiment, electroplating is used to fabricate non-integral pin portions shaped to remain securely encapsulated within the plastic molding of the package. In accordance with another embodiment, electroplating may be used to fabricate protrusions on the underside of the lead frame for elevating the package above the PC board, thereby preserving the rounded shape of solder balls used to secure the diepad to the PC board. In accordance with yet another embodiment, electroplating may be used to fabricate raised patterns on the upper surface of the diepad for ensuring uniform spreading of adhesive used to secure the die to the diepad, thereby ensuring level attitude of the die within the package.

FIG. 1A shows an underside plan view of a conventional quad flat no-lead (QFN) package utilized to house a semiconductor device. FIG. 1B shows a cross-sectional view taken along line B-B′, of the conventional QFN package of FIG. 1A, positioned on a PC board.
QFN package 100 comprises semiconductor die 102 having electrically active structures fabricated thereon. Die 102 is affixed to underlying diepad 104a portion of lead frame 104 by adhesive 106. The relative thickness of the die and lead frame shown in FIG. 1B, and all other drawings of this patent application, is not to scale. Lead frame 104 also comprises non-integral pin portions 104b in electrical communication with die 102 through bond wires 108. Bond wires 108 also allow electrical communication between die 102 and diepad 104a.
Plastic molding 109 encapsulates all but the exposed portions 104a′ and 104b′ of the lead frame portions 104a and 104b, respectively. For the purposes of this patent application, the term "encapsulation" refers to partial or total enveloping of an element in a surrounding material, typically the metal of the lead frame within a surrounding dielectric material such as plastic.
Portions of the upper surface of lead frame 104 bear silver Ag 105 formed by electroplating. The lower surface of lead frame 104 bears a layer of Pd/Ni or Au/Ni 107 formed by electroplating.
QFN package 100 is secured to traces 110 of underlying PC board 112 by solder 114 that preferably has the rounded shape indicated. The electrically conducting properties of solder 114 allows electrical signals to pass between lead frame portions 104a and 104b and the underlying traces 110.
FIG. 1C shows a plan view of only the lead-frame 104 of QFN package 100 of FIGS. 1A–B. Lead frame 104 is typically formed by etching a pattern of holes completely through a uniform sheet of copper. FIG. 1D shows one example of such a pattern of holes 116 in a copper roll 118. These patterns of holes define a proto-lend frame 122 comprising proto-diepad 124 and proto-non-integral portions 126. Proto-diepad 124 is secured to the surrounding metal frame by tie bars 120. Proto-non-integral pin portions 126 are secured to the surrounding metal frame by tabs 128.
The patterned metal portion shown in FIG. 1D is processed into a package by gluing a die to the diepad, and connecting bond wires between the die and non-integral portions and/or the diepad. While the diepad and non-integral portions are still attached to the surrounding metal, the bond wires and a portion of the diepad and non-integral lead frame portions are encapsulated within a dielectric material such as plastic. Fabrication of an individual package is then completed by severing the tabs and tie bars to singulate an individual package from its surrounding metal frame and other packages associated therewith.
While adequate for many purposes, the conventional QFN package just described offers some drawbacks. One drawback is the difficulty of forming raised features on the lead frame.
For example, FIG. 1B shows that non-integral lead frame pin portions 104b exhibit a thinned region 104b″ proximate to the diepad. Thinned pin region 104b″ is surrounded on three sides by the plastic encapsulant 109 of the package body, thereby physically securing non-integral pin portion 104b within the package.
Moreover, FIG. 1B also shows that diepad portions 104a exhibit a thinned region 104a″ proximate to the non-integral pins. Thinned diepad region 104a″ is surrounded on three sides by the plastic encapsulant of the package body, thereby physically securing the diepad within the package.
FIGS. 1E–1H show cross-sectional views of the conventional process steps for fabricating a lead frame having a thinned portion. In FIG. 1E, the inverted Cu sheet 118 is electroplated on its bottom surface with an Au/Pd/Ni combination or an Ag/Ni combination to form layer 107. For the Au/Pd/Ni combination, the Au is between about 0.01–0.015 μm in thickness, the Pd is between about 0.02–0.2 μm in thickness, and the Ni is between about 0.5–2.5 μm in thickness. For an Ag/Ni electroplated coating, Ag and Ni are each between about 0.5–2.5 μm in thickness.
In FIG. 1F, photoresist mask 150 is patterned over layer 107 to expose the regions 152 that are to be thinned. Exposed regions 152 are then exposed to an etchant for a controlled period, which removes Cu material to a predetermined depth Y.
In FIG. 1G, the photoresist mask is removed, and Cu roll 118 is then reoriented right side up. The upper surface of the Cu roll 118 is then selectively electroplated to form silver layer 105. The silver may be electroplated only in specific regions over the substrate utilizing a mask (not shown) during this step.
In FIG. 1H, the backside of partially-etched Cu sheet 118 is patterned with a photoresist mask 119 leaving exposed areas 121 corresponding to the thinned regions. The partially-etched Cu sheet 118 is then etched completely through in the exposed areas 121 to form a pattern of holes 116 separating diepad 104a from non-integral pins 104b.
Fabrication of the QFN package is subsequently completed by affixing the die to the diepad, attaching bond wires between the die and diepad and non-integral pin portions, and then enclosing the structure within plastic encapsulation, as is well known in the art.
The etching stage of the QFN package fabrication process shown in FIG. 1F is relatively difficult to control with precision. Specifically, the accuracy of etching the Cu lead frame in small areas is about 20–25% of the total lead frame thickness. This is due to inability to rapidly and reproducibly halt the progress of chemical etching reaction once it is initiated. Etching outside the above tolerance range can result in the scrapping of many lead frames, elevating package cost.
Moreover, the conventional approach of partial etching to shape thinned features limits the pitch of the lead, and thus the number of pins available for a given QFN package body size. This limitation in lead pitch results from the at least partially isotropic character of the etching process, which removes material in the lateral, as well as vertical, direction.
Therefore, there is a need in the art for improved techniques for fabricating semiconductor device packages.

Semiconductor device package diepad having features formed by electroplating


A computer-implemented method includes: monitoring, by a computing device, communication flows within an industrial processing system; identifying, by the computing device, a hazardous command based on monitoring the communication flows, wherein identifying the hazardous command includes running a simulation with the communication flows as an input to the simulation; generating, by the computing device, a set of one or more mitigating commands based on identifying the hazardous command; and outputting, by the computing device, the set of one or more mitigating commands to components within the industrial processing system, wherein outputting the set of the one or more mitigating commands reduces a level of hazard caused by the hazardous command.

The present invention generally relates to industrial process systems, and more particularly, to mitigating hazardous conditions caused by malicious or unintentional commands in industrial process systems.
Modern large scale industrial processes are controlled by a hierarchy of systems, starting with master compute systems, which in turn communicate with industrial controllers (e.g., Programmable Logic Controllers (PLCs)), which then communicate with specific devices, such as machine controls, environmental sensors, valve motors, etc. Examples of complex industrial processes include nuclear, hydro and fossil fuel power plant generation, petroleum extraction and refining, chemical manufacturing, pharmaceutical manufacturing, water supply and water treatment systems, flood control systems, etc. Very little security exists between the master compute systems and the industrial controllers and between the industrial controllers and the physical devices controlled by the industrial controls and from which readings are obtained. Altering, inserting, or disrupting communications in industrial processing systems is accomplished relatively easily (e.g., by hackers), and can cause significant physical damage or injury. Also, certain commands can be unintentionally or accidentally injected into an industrial processing system. Instances of failures in industrial processing systems have become relatively frequent. For example, malicious commands may be injected into industrial processing systems through an internal network or via external networks (e.g., cloud networks).
Currently, individual commands from controllers are checked for their individual validity. As an example, checks are implemented to determine whether a command to set the temperature of a reaction vessel between two pre-established points or no more than a pre-established threshold. However, failures, both minor and catastrophic, can be created in a complex system using only legitimate (individual) values. For example, certain values, which when, taken in their entirety, the set of values (each of which is legitimate in and of itself) is applied to one or multiple components in the system. That is, even a malicious command could be "valid" in that the command may control a device within specified parameters (e.g., a command may open or close a valve within normal operating conditions or angles). However, even a valid command, could cause a failure, potentially hours from the application of the command. Although a master control system may not send a failure set of values or commands, the controllers and their communications networks are susceptible to hacks resulting in alteration of the communications packets and/or the industrial controllers themselves.
This issue affects modern industrial processes, and is especially acute in critical infrastructure systems, in which failures may cause loss of life and/or significant property damage. The impact of a malicious command may not be apparent for hours or days. For example, a command to calibrate a reaction vessel pressure limit set point by one pound per square inch (PSI) increase every hour may take two weeks before the reaction vessel explodes. Since hackers can compromise the master compute system and/or industrial controller, an outside observation and correction system may prevent the catastrophic effects of malicious attacks on industrial processing systems.

Monitoring communications flow in an industrial system to detect and mitigate hazardous conditions

INTERNATIONAL BUSINESS MACHINES CORPORATION


A three-phase filter has first, second, and third power source connectors and first, second, and third load connectors. A separate phase line filter is connected between each pair of power source and load connectors. Each phase line filter includes a line winding connected between the power source and load connectors for a phase line and includes a first shunt winding, resistor and capacitor connected in series between that load connector and the load connector for another phase line. The line and shunt windings for a given phase line filter are wound on a core in directions so that one winding produces magnetic flux having an opposite polarity to the magnetic flux produced by the other winding. The magnetic coupling of those windings, mitigates harmonic currents that otherwise flow in either direction between the power source and load connectors.

1. Field of the Invention
The present invention relates to electrical power distribution systems, and more particularly to filters for mitigating harmonic currents in such systems.
2. Description of the Related Art
Electrical loads are commonly controlled by power converters, such as adjustable speed drives for operating large electric motors, which convert AC power at one frequency to another frequency. Power converters for electric motors often are bidirectional so that when the motor is being driven by the mechanical load in a regenerative mode, the motor acts as a generator sending electrical current back through the power converter into the utility lines.
Non-linear electrical loads produce various levels of harmonic currents in the power distribution system with the harmonic frequency spectrum depending upon the nature of the load. The harmonic currents create many problems in the power distribution system, including increased total harmonic distortion voltage level, reduced power distribution equipment reliability, reduced electromagnetic compatibility of the loads, increased power losses, reduced power factor, and other problems which are well known to those skilled in the art.
Many apparatus have been proposed for mitigating harmonic currents. For example, filters were placed at the utility line connections to reduce the transmission of harmonics from the utility lines to the electrical load in the motoring mode and from the electrical load to the utility lines in the regenerative mode. However, conventional filters added an undesirable amount of reactance between the supply lines and the load.

Three-phase harmonic reduction filter for bidirectional power converters


The present invention provides a bi-directional catheter with nearly double the throw in its catheter tip deflection. In particular, the travel path of each the puller wire includes a U-turn or doubling-back around a pulley which minimizes the offset angle between the puller wire and the longitudinal axis of the control handle while maximizing the travel distance of that puller wire for any given distance traveled by the pulley drawing the puller wire. In one embodiment, the catheter has an elongated catheter body, a catheter tip section with first and second diametrically-opposed off-axis lumens, and a control handle which includes a steering assembly having a lever structure carrying a pair of pulleys for simultaneously drawing and releasing corresponding puller wires to deflect the tip section of the catheter.

Electrode catheters have been in common use in medical practice for many years. They are used to stimulate and map electrical activity in the heart and to ablate sites of aberrant electrical activity. In use, the electrode catheter is inserted into a major vein or artery, e.g., femoral artery, and then guided into the chamber of the heart which is of concern. Within the heart, the ability to control the exact position and orientation of the catheter tip is critical and largely determines how useful the catheter is.
Bidirectional catheters have been designed to be deflectable in one direction by one puller wire and in the opposite direction within the same plane by a second puller wire. In such a construction, the puller wires extend into opposing off-axis lumens within the tip section of the catheter. So that the tip section can bend in both directions in the same plane, the puller wires and their associated lumens must be located along a diameter of the tip section. For ablation catheters, electrode lead wires must also be provided within the distal end. Typically, an additional lumen is used to contain the electrode lead wires. For example, U.S. Pat. No. 6,210,407, the disclosure of which is incorporated herein by reference, is directed to a bi-directional catheter comprising two puller wires and a control handle having at least two moveable members longitudinally movable between first and second positions. The proximal end of each puller wire is connected to an associated movable member of the control handle. Proximal movement of a movable member relative to the catheter body results in proximal movement of the puller wire associated with that movable member relative to the catheter body, and thus deflection of the tip section in the direction of the lumen in which that puller wire extends.
As another example, U.S. Pat. No. 6,171,277, the disclosure of which is incorporated herein by reference, is directed to a bidirectional steerable catheter having a control handle that houses a generally-circular spur gear and a pair of spaced apart rack gears. Each rack gear is longitudinally movable between first and second positions, whereby proximal movement of one rack gear results in rotational movement of the spur gear, and correspondingly distal movement of the other rack gear. Two puller wires extend from the control handle whose the distal ends are fixedly attached to the tip section, and whose proximal ends are each anchored to a separate associated rack gear in the control handle. Proximal movement of a rack gear and its associated puller wire relative to the catheter body results in deflection of the tip section in the direction of the off axis lumen into which that puller wire extends.
Also known is U.S. Pat. No. 6,198,974, the disclosure of which is incorporated herein reference, is directed to a bi-directional electrode catheter comprising a control handle. At their proximal ends, two pairs of puller wires are attached to movable pistons in the control handle. Each piston is controlled by an operator using a slidable button fixedly attached to each piston. Movement of selected buttons results in deflection of the tip section into a generally planar "U"- or "S"-shaped curve.
Further known is U.S. Pat. No. 5,891,088, the disclosure of which is incorporated, directed to a steering assembly with asymmetric left and right curve configurations. Proximal ends of left and right steering wires are adjustably attached to a rotatable cam housed in a control handle. The rotatable cam has first and second cam surfaces which may be configured differently from each other to accomplish asymmetric steering.
While the aforementioned catheters provide bi-directional steering, the mechanical efficiencies of the steering or deflection mechanism can be improved upon. Because the control handle has limited interior space in which to house the steering mechanism, a need exists for a compact yet mechanically-efficient design to accomplish bi-directional steering. Moreover, a greater degree of deflection in the catheter tip is also desirable, particularly if it can be accomplished without requiring greater exertion on the part of the user. The steering assembly of aforementioned U.S. Pat. No. 5,891,088 employs a configuration whereby the puller wires extend to the cam surfaces of the rotatable cam at a greater than generally desirable angle from the longitudinal axis of the catheter shaft, which decreases the efficiency of the steering lever and increases friction losses in the operation of the steering assembly. In addition, the steering assembly therein generally limits the amount of longitudinal movement of the puller wires for deflecting the catheter tip to only the circumference of the rotatable cam. An improved catheter with bi-directional deflection is therefore desired.

Steering mechanism for bi-directional catheter


A dispersion compensator exhibiting low polarisation mode dispersion is constructed from a polarisation beam-splitter, a .pi./4 rotation Faraday rotator, and a matched pair of polarisation maintaining fibres provided with a matched pair of chirped Bragg reflection gratings. The waveguides are oriented with respect to the beam-splitter so that light reaching the waveguides from the beam-splitter via the rotator is launched into both waveguides with a polarisation state aligned with the same polarisation axis (i.e. both fast or both slow).

The use of Bragg reflective gratings in optical fibre waveguides for waveguide dispersion compensation in optical fibre transmission systems has been described in GB 2 161 612 B. The dispersion compensator uses a chirped Bragg reflective grating in an optical waveguide connected to one port of a 3-port circulator or of a 2.times.2 3 dB directional coupler. Light is directed into one port of the circulator or 3 dB coupler from which it is launched into the waveguide with the chirped Bragg grating. The reflected light is launched back into the circulator or (3 dB coupler) to emerge from a different port. Conventional transmission fibre typically exhibits a dispersion zero at a wavelength in the region 1.3 .mu.m, and therefore, for transmissions in the region of 1.5 .mu.m, this fibre exhibits anomalous dispersion (i.e. longer wavelengths in the region of 1.5 .mu.m suffer a longer transit time through the fibre than shorter wavelengths in this region). Accordingly, to achieve a measure of dispersion compensation, the Bragg grating should delay shorter wavelengths more than longer wavelengths, this by reflecting the longer wavelengths at distances closer to the circulator (or 3 dB coupler) than those at which the shorter wavelengths are reflected. In other words the large pitch end of the chirped Bragg grating reflector should face the circulator (or 3 dB coupler). The Bragg reflective grating based dispersion compensator that employs a 3-port circulator is depicted in FIG. 1A, while its counterpart that employs a 2.times.2 fused fibre 3 dB directional coupler is depicted in FIG. 1B. Referring to FIG. 1A, a 3-port circulator 10 has ports 10a, 10b, and 10c. Ports 10a and 10c constitute respectively the input and output ports of the dispersion equaliser. Port 10b is optically coupled with a chirped Bragg reflective grating 12. The dispersion equaliser of FIG. 1B is distinguished from that of FIG. 1A in that the place of the circulator 10 of the dispersion equaliser of FIG. 1A is taken by a 2.times.2 fused fibre 3 dB coupler 14 provided with ports 14a, 14b, 14c and 14d. Ports 14a and 14c constitute respectively the input and output ports of the dispersion equaliser. Port 14c is optically coupled with the waveguide 11, while port 14d is not used.
The dispersion equaliser of FIG. 1A may be preferred to that of FIG. 1B because the circulator 10 does not introduce the same intrinsic loss as the 3 dB coupler 14. When power is launched into output port 14a of coupler 14, there is a minimum of 3 dB loss because half of this power is directed to output port 14d, instead of to output port 14b, and so is wasted. Similarly, a further minimum of 3 dB loss occurs because half of the power reflected by the Bragg grating, instead of being direct into the output port 14c, is directed out of the input port 14a, and so is wasted. On the other hand a 3-port circulator is liable to be much more costly than a 3 dB fused fibre coupler.
The problem of the 6 dB extra loss involved in the use of the 3 dB coupler has been addressed by M J Guy et al in a report entitled, `Low-loss fibre Bragg grating transmission filter based on a fibre polarisation splitter`, Electronics Letters, Sep. 1, 1994, Volume 30, Number 18 pages 1512-3. In particular this report describes a way of avoiding the 6 dB loss penalty by a method involving the use of an optical fibre polarisation beam-splitter instead of a 3 dB coupler, the use of a second Bragg reflector optically coupled with the fourth port of the polarisation beam-splitter, and the use of two quarter wave birefringence elements. This arrangement is depicted in FIG. 2. Referring to FIG. 2, a polarisation beam-splitter 20 has ports 20a, 20b, 20c and 20d. Ports 20a and 20c constitute respectively the input and output ports of the dispersion equaliser. Light of any arbitrary state of polarisation (SOP) applied to input port 20a is resolved into orthogonal linearly polarised components respectively emerging by way of ports 20b and 20d. From these ports the light is launched via respective quarter-wave birefringence elements 21 and 21' into respective fibres 11 and 11' provided with identical chirped Bragg reflectors 12 and 12' optically substantially equidistant from the polarisation beam-splitter 20. The quarter-wave birefringence elements 21 and 21' are aligned such that the linearly polarised light from each of the ports 20b and 20d is launched into their respective fibre 11 and 11' as circularly polarised light. The light that is reflected by the respective gratings 12 and 12' is also circularly polarised, but now has the opposite handedness. Accordingly, after transmission back through birefringence element 21, the light being launched back into polarisation beam-splitter 20 by way of port 20b from fibre 11 is polarised orthogonally with respect to the SOP of the light that was launched from port 20b into fibre 11. Therefore this reflected light passes back through the polarisation beam-splitter 20 to emerge exclusively by way of port 20c. Similarly, after transmission back through birefringence element 21', the light launched back into polarisation beam-splitter 20 by way of port 20d from fibre 11' is polarised orthogonally with respect to the SOP of the light that was launched from port 20d into fibre 11'. Therefore this reflected light also passes back through the polarisation beam-splitter 20 to emerge exclusively by way of port 20c.
The foregoing analysis has failed to take any account of any birefringence that may be present in either of the fibres 11 and 11'. If there is any such birefringence, this will make the `optical pitch`, by which term is meant the product of the physical pitch with the effective refractive index, of any pair of Bragg reflecting elements of a Bragg grating different for the two different principal SOPs. The physical pitch is the same in both instances, but the presence of birefringence means that their effective refractive indices are necessarily different. This means that any particular part of the chirped grating will reflect a waveband centred on one wavelength for one of the principal SOPs, and will reflect a waveband centred on a slightly different wavelength for the other principal SOP. In other words, in the presence of birefringence in the waveguide in which the Bragg reflection grating is created, the reflection produced by that grating produces polarisation mode dispersion (PMD).
Polarisation maintaining optical waveguide has fast and slow axes defining, together with the waveguide axis, an orthogonal set of axes. The two planes that contain the waveguide axis and either the fast axis or the slow axis define principal planes, these having the property that light of a single wavelength plane polarised in a principal plane propagates in the waveguide with a single velocity. The velocity is greater for light propagating plane polarised in the principal plane containing the fast axis than for that plane polarised in the other principal plane (containing the slow axis). For light propagating with any other state of polarisation (SOP), this light is resolved into its principal plane components which, on account of their propagation with different velocities, give rise to the phenomenon of polarisation mode dispersion (PMD).
An idea of the scale of the problem of PMD in the Bragg reflection grating type dispersion compensators of an optical transmission system can be arrived at by considering a 10 Gbit/s system. The pulses in such a system are 100 ps wide. If there are a number of dispersion compensators in cascade along the transmission path, their PMD will be cumulative, and so the PMD of each may typically be required to be less than 1.0 ps. In a typical optical fibre, light will travel about 1 mm in 5 ps, and so, if Bragg grating of a dispersion compensator is written in birefringent fibre, the point along the grating at which one principal plane component of light of any chosen freespace wavelength is reflected should, taking into account the folded path, be separated by less than 0.1 mm from that at which the other principal plane component is reflected. If the grating is 2 meters long, is centred on a free-space wavelength of 1.5 .mu.m, and covers a (freespace) spectral range of 30 nm, then the rate of change of pitch is 15 pm per mm. Under these conditions the proportional change in reflected wavelength over a 0.1 mm distance along the grating is 1 part in 10.sup.6. Therefore, for the Bragg grating not to induce more than 1.0 ps PMD, the proportional difference between the effective refractive indices of the two principal planes should not exceed 1 part in 10.sup.6.
As a practical matter, to make an optical fibre with a birefringence as low as this is not always an easy task because unintentionally introduced departures from perfect circular symmetry are very liable to introduce significant birefringence. With the exercise of due care, it is possible to make conventional transmission type optical fibre with birefringence lower than this. An example of a very low birefringence fibre of this sort may typically have a PMD in the region of 0.0005 ps/m, which corresponds to a birefringence index difference of about 1 part in 10.sup.7. However optical fibre designed for high photosensitivity suitable for having Bragg gratings written into it typically has a core/cladding index difference (.DELTA.n) greater than that of conventional transmission fibre (typically .DELTA.n.apprxeq.0.01 instead of .DELTA.n.apprxeq.0.005), and the greater index difference is found to exacerbate the non-circularity problem. Moreover there can be good reason for wanting to use fibre with an even higher .DELTA.n, typically fibre for which .DELTA.n.apprxeq.0.05. A reason for this is that increasing .DELTA.n provides a `blue-shift` to the short wavelength loss exhibited by chirped Bragg reflective gratings. If .DELTA.n is large enough, the blue-shift may be sufficient to take this loss, or at least a significant proportion of it, outside the operative wavelength band of the transmission system in which the dispersion compensator is to be located.
A fibre whose .DELTA.n is about 0.05 is typically found to exhibit a birefringence of about 0.05 ps/m, making it a medium birefringence fibre with a beat length of about 10 cm. This corresponds to a birefringence index difference of about 1 part in 10.sup.5.
According to a theory developed by R Ulrich, `Fiber-Optic Rotation Sensors & Related Technologies, Proceedings of the First International Conference` page 67, the phase shift per meter .beta. introduced by bending an optical fibre of radius r into a curve of radius R.sub.c is given by EQU .beta.=0.565.times.10.sup.6 (r/R.sub.c) rads/m
at a free-space wavelength .lambda.=1.5 .mu.m. From this it can be shown that, for 125 .mu.m diameter fibre, a bend radius of about 6 mm or less is required to cancel the birefringence of a fibre with a beat length of 10 cm, and so such fibre is polarisation maintaining fibre under normal operating conditions.
It is now seen that, though the dispersion equaliser of FIG. 2 does offer a way around the 6 dB loss penalty, it does this in a manner that ensures that any birefringence in fibres 11 and 11' is certain to introduce PMD into the system because light is propagating in these fibres as circularly polarised light.

Dispersion compensation with low polarization mode dispersion


A magnetic transducer is provided which has two coils wound in opposite directions on a core. The transducer coils are connected to a direct current power supply via two switches respectively. A write control circuit applies a binary write control signal, representative of digital information to be recorded, to the switches thereby causing the same to be alternately turned on and off. A reactor is connected in series with the power supply, so that each transducer coil is excited not only from the power supply but also from the reactor. An alternate embodiment is disclosed in which the transducer has only one coil connected to a power supply via a bridge circuit of four switching transistors. The transducer coil is alternately excited in opposite directions from a power supply and a reactor connected in series therewith.

This invention relates generally to magnetic recording systems for digital information, and more specifically to such a system capable of driving a magnetic transducer with a current higher than that due only to a power supply of a given voltage, in order to make possible the recording of high frequency digital signals.
Magnetic transducers are inductive, so that they offer high impedances when recording high frequency digital information. Correspondingly high drive voltages are therefore required. It might be contemplated to provide inductance capacitance resonance networks in order to obtain sufficiently high voltages. This solution is unsatisfactory because it would be difficult to maintain LC resonance in cases where the information being recorded varies in a wide range of frequencies.
Another solution is found in an article entitled "Overwriting Technologies of Magneto-optical Disks by Magnetic Field Modulation Method" in pp. 63-70 of the Vol. 14, No. 17, issue of Television Gakkai Technical Reports published February 1990 by Television Gakkai of Japan. This article teaches the connection of two inductive reactors between magnetic transducer and power supply. Two switches are alternately turned on and off to cause the transducer to be excited from the power supply via one of the reactors and then the other. Energy is stored on one of the reactors when the transducer is being excited via the other reactor. Accordingly, when the transducer is subsequently excited via said one reactor, the energy that has been stored thereon is also utilized to energize the transducer. A net current flowing through the transducer is therefore of greater magnitude than the current offered solely by the power supply.
This prior art transducer drive system is objectionable for several reasons. First, it requires two reactors, making the system bulky and expensive. Second, constant current flow through the two reactors involves considerable power loss because of their resistivity. Third and finally, as the current flows through each switch after flowing through both reactors, power loss also occurs at the two switches.

Low voltage, high current magnetic transducer drive system for digital recording


A method for trading a pair of securities is provided and includes the step of retrieving a previously configured pair trade request and the previously configured pair trade request is submitted to a pair trade fulfillment module.

The following invention relates to a system and method for trading securities and, in particular, for a system and method of submitting pair trade requests.
A recognized strategy for trading securities is known as pair-trading. Pair-trading is a non-directional investment strategy in which the investor identifies two securities having similar characteristics and the securities are currently trading at a price relationship that is out of their historical trading range. The investor exploits the price relationship between the securities by buying the undervalued security while short-selling the overvalued security. Because pair-trading is a market-neutral strategy, it is a particularly desirable strategy for investing in volatile markets.
One context in which pair trading is useful is where an investor desires to take advantage of an arbitrage opportunity resulting from a merger between two companies. For example, Company A has announced a definitive agreement to acquire Company T in which case Company T shareholders will receive 0.5 shares of Company A stock for each share of Company T stock they own. The investor desires to capture the "spread" between the offered consideration (0.5 shares of A) and the price of T stock. To do this, the investor buys shares in T stock and sells shares of A stock.
For instance, if stock T is trading at $28 per share and stock A is trading at $60 per share, then the investor may execute a trade for 200,000 spreads by buying 200,000 shares of T stock and selling 100,000 shares of A stock. After the merger takes place, the investor will cover the short position in stock A with the 100,000 shares of A stock the investors receives in exchange of the 200,000 shares the investor held of stock T. Thus, by executing the pair trade, the investor locks in a $400,000 profit (assuming that the merger goes through).
An investor desiring to execute a pair trade first formulates a pair trade request. A pair trade request is characterized by a plurality of parameters including, for example, a spread quantity, a buy ticker, a sell ticker, a buy trading ratio, a sell trading ratio, whether to trade oddlots, whether to execute a short sale, whether to work the bid side of a spread (i.e., buy stock first and take short-sale execution risk), a minimum wave size (i.e., the minimum share amount per tranche), a maximum wave size (i.e., the maximum share amount per tranche), a slippage factor, a wave stop loss unit, a nuisance cancel amount, an improve cancel unit, a minimum order distance, an order limit type (e.g., dollar difference, percent premium or discount, sell over buy or buy over sell, cash-adjusted) and order limit parameters (e.g., buy calculation ratio, sell calculation ratio, cash offset). Once a pair trade request is formulated, the investor typically presents the pair trade request to a broker affiliated with a financial institution for execution.
Because the formulation of a pair trade request requires that the investor specify numerous parameters, it takes time for the investor to prepare and submit a pair trade request to exploit a particular market condition. This time required may cause an investor to miss a potentially profitable trading opportunity, especially in fast-moving markets.
Accordingly, it is desirable to provide a system and method for submitting pair trade requests.


Digital data signals at a variable input frequency are converted by a numerically controlled oscillator and an interpolator to a signal at a fixed output sampling frequency. The conversion of the variable input frequency to the fixed output sampling frequency may be by a factor other than an integer. The interpolated digital data signals at the fixed output sampling frequency are then modulated into a pair of trigonometric signals at a programmable carrier frequency, one signal having a cosine function and the other signal having a sine function. The modulated signals at the fixed output sampling frequency are then combined to create a modulated signal at a carrier frequency determined by the frequency of the sine and cosine signals. The modulated signal is sampled at the fixed output sampling frequency and converted to a corresponding analog signal using a digital-to-analog converter.

This invention relates to a system including a variable rate modulator for (1) varying the rate at which signals are modulated in accordance with variations in the rate of introduction of digital data to the system and (2) for processing the modulated signals to provide output signals at a fixed sampling frequency.
In recent years, a number of different applications have arisen in which digital signals representing data are processed and the processed signals are then converted to analog signals. For example, such applications have included the transmission of television signals through coaxial lines to homes. In such systems, the digital data is converted to analog signals and the analog signals are then transmitted through coaxial lines to homes of subscribers. Other applications are in microwave links and satellite communications.
In a number of the different applications involving the processing of digital data and the conversion of the processed digital data to analog signals, the digital data is provided at a variable input frequency or rate and the analog signals are provided at a fixed sampling frequency different from the variable input frequency or rate. For example, the digital data may be provided in the range of approximately 0.1-20 megabits per second and the analog signals may be sampled at a fixed frequency in the range of approximately 100-200 megahertz.
In the above example, the variable rate digital signals in the range of 0.1-20 megabits/second are converted to a modulated analog intermediate frequency signal having a fixed sampling frequency. For example, the digital signals in the range of 0.1-20 megabits/second may be converted to signals at a fixed sampling frequency of approximately 100-200 megahertz. The signals at the sampling frequency are then modulated onto a programmable carrier frequency in the range of approximately 5-65 MHz. at the fixed sampling frequency of approximately 100-200 megahertz.
As will be seen from the above discussion, a considerable range of frequencies (e.g. 0.1-20 megabits/second) have to be converted to a single fixed frequency (e.g. 120 megahertz). This is not easy. If the conversion is not accurate, the signals at the fixed sampling frequency jitter. When the signals illustratively provide television information, the jitter produces a significant deterioration in the quality of the television image.
This invention provides a system for, and method of, converting digital data signals variable through a wide range of frequencies or rates into signals at a fixed sampling frequency. This conversion occurs without any jitter in the signals at the fixed sampling frequency. When the system of this invention is illustratively used to provide television images, the television images have a high resolution.
In one embodiment of the invention, digital data signals at a variable input frequency are converted by a numerically controlled oscillator and an interpolator to a signal at a fixed sampling frequency. The conversion of the variable input frequency to the fixed output sampling frequency may be by a factor other than an integer.
The interpolated digital data signals at the output sampling frequency are then modulated onto a pair of trigonometric signals at a programmable carrier frequency, one signal having a cosine function and the other signal having a sine function.
The modulated pair of trigonometrically related signals at the fixed sampling frequency are then combined to create a modulated signal at a carrier frequency determined by the frequency of the sine and cosine signals. The modulated signal is sampled at the fixed sampling frequency and converted to a corresponding analog signal using a digital-to-analog converter.


Environmentally protective Method of treating an aqueous radioactive fluid (AF) in a nuclear reactor cycle or radwaste system to selectively capture or remove radioactive isotopes in a reduced quantitative package to minimize radwaste generated and revitalize neutron absorption capacity of nuclear reactor coolant by separately carrying away boron constituents, when B10 is later added. The method includes: demineralizing the (AF) by rough ion exchange and lowering the pH of salts, boron and non-radioactive substances so that the boron can later pass through an RO; polishing by reverse osmosis; dividing the (AF) into a permeate liquid volume and a reject liquid volume, each having certain characteristics; recycling the reject liquid volume back into demineralizing step for removing generally most of the radioactive isotopes to generate a demineralizer effluent; and conveying the permeate liquid volume to the outside ambient environmental release point for liquid effluents of the (AF); dividing the demineralizer effluent into a further permeate liquid volume and a further reject liquid volume having certain characteristics; and conveying the further permeate liquid volume to the outside ambient environmental release point of the invention.

1. Field of the Invention
The present invention relates to a Method, Process or System for processing and treating an aqueous radioactive liquid in a nuclear reactor for the purpose of removing radioisotopes or radioactive metal ions and particulate so as to significantly reduce the volume of the radwaste for use, disposal or storage, and to generate only one additional stream containing the water, salts and non-radioactive components in a form that can safely be returned to the environment separate and apart from the nuclear reactor site to protect ground and ground waters.
2. Background Information
The liquid radwaste (LRW) systems in commercial nuclear power plants and utilities have used conventional demineralization to provide discharge wastewater that attempts to meet both NRC and waste quality requirements for radioactive isotopes and RCRA elements. Plants have attempted to stay below regulatory discharge requirements by using demineralizer (ion exchange) technology where the principal components have included conventionally positioned demineralizing systems consisting of tanks, essential piping, pumps and valves. Liquid wastes generated in using such past conventional setups have required further cleanup or treatment before other use in a different area of the plant and were not capable of effectively treating or processing radwaste liquids to quality grade water permitting discharge back to the outside environment.
More recently other factors have come into play. The potential contamination of rivers, lakes, bays and estuaries by plant discharges has resulted in increased nuclear insurance rates, and attention by industry peer review and audit groups, and public attention by various activist groups, has motivated utilities to continually improve environmental performance. The emphasis has therefore been on reducing releases of the main or primary gamma, beta and alpha activity contributors of cesium, cobalt iodine and others substantially below regulatory level for liquid releases to the environment.
As discharge of radioisotope emitters was reduced, secondary isotopes such as antimony and iron, previously masked or difficult to detect, became more focused. It was found that Iron isotopes 55 and 59 were not readily removed by filtration and ion exchange. Therefore, a need for a more effective removal processing before discharge became necessary.
Tritium isotopes were more readily detected but virtually impossible to separate from the process stream. Therefore, plants have been evaluating the possibility of recycle of liquid streams back to the plant for further use instead of being discharged with tritium to the environment.
Prior to the present invention, mechanical filtration and ion exchange technology were only marginally capable of meeting reduced gamma discharges, effective removal of secondary isotopes for discharge, or production of the high quality water required for recycle to allow retention of tritium.
Additionally, aspects of the past technology in dealing with RCRA wastewaters, and recycle applications containing regulated chemicals being permitted only to be discharged in limited amounts, have been sorely missing and urgently needed.
In recent decades various membrane separation processes have been developed and utilized in the field of potable water purification; and more recently in the treatment of various process and waste liquors. Some of the membrane processes are capable of removing both dissolved and particulate contaminants. The best known and most utilized membrane processes in the field of water and wastewater treatment are those utilizing pressure gradients as the process driving force. These processes include reverse osmosis, nanofiltration, ultrafiltration and microfiltration.
Conventional reverse osmosis or RO has been used in the past in certain industrial settings; having been applied to separation, concentration of product streams, and wastewater treatment. More specifically, the past conventional RO technology setups have been used for removal of radionuclides from low level liquid wastes such as waste streams at nuclear power plants. In this regard, conventionally placed RO systems have been used in the nuclear industry as a part of an overall liquid waste treatment system.
Importantly, in its conventional use and positional placement, RO was set up and placed in a position in a system or process ahead or in front of a polishing demineralization treatment, in a configuration referred to as RO-IX. In this configuration, the RO separated the raw process stream into two distinct streams: 1) the permeate (clean) and 2) the reject (dirty) stream. The clean stream, containing reduced concentrations of impurities after one or two passes, still often required polishing with downstream ion exchange media to meet quality requirements for either recycle or discharge. The reject stream, containing a high fraction of the raw stream constituents, was then conventionally subject to further processing, for example, evaporating or drying to dried solids. In this configuration, 90% to 99.9% of the waste stream contaminants were rejected by the RO and the balance removed by the downstream IX polisher.
A number of problems and deficiencies in this process setup and positional configuration have been identified. When presented with a high concentration of contaminants in the raw waste stream, a higher than desirable concentration of contaminants pass through the membrane, often requiring multiple RO passes and extensive ion exchange polishing to produce an acceptable permeate, thus resulting in increased capital equipment and operating costs and increased consumption of ion exchange resin to polish the permeate. In some instances, the RO concentrated raw stream contaminants to near their solubility limits. The volume of the reject had to be increased to preclude precipitation on the membrane and their fouling. The need for these process conditions, to effect adequate cleanup, resulted in increased equipment and operating costs, larger equipment footprint and increased resin consumption and further processing of increased reject volumes.
Additional problems in this past technology setup were found to occur with respect to utilization of the reject stream, which generally represented 2-15% of the feed stream volume. It was found that it was required to deal with such a waste stream because it contained a number of undesirable elements. In non-nuclear applications these waste streams could often be discharged to sanitary sewers or even returned to the original body of water. However, in nuclear applications, as preferred in the present invention, the reject contained radioactive isotopes that were required to be sent to special disposal facilities in a stabile or non-mobile form. Since water or substantially aqueous volumes were not regarded as an acceptable form, the water had to either be solidified or evaporated to leave dry or dirt-like solids. Since these volumes were significant the cost was found to be high, and sometimes prohibitive. As was the case before and now, often suitable locations to provide drying or solidification are not easily found in nuclear plants. In this regard, it is important to note that the present invention and method totally eliminates or substantially minimizes the need to dispose and treat the reject stream by evaporation, solidification or off-site transportation. The ion exchange media, as positioned in the invention steps removes the concentrated ions in the reject which are captured in the polishing phase or step of the invention. This prevents the osmotic pressure from increasing and the efficiency of the RO in the invention from decreasing. This means that potentially no dry solids will be generated. Therefore, this reduces the overall waste volume to be disposed in light of the fact that greater than 99% of the waste is typically boron salts when dry solids are produced. Previous systems in the past technology all generated continuous reject streams that had to be retreated. At best, these could only be recycled a short period of time prior to the results of the system deteriorating or degrading below acceptable levels. Likewise, the reject stream suffered shortcomings from this conventional processing configuration. The reject stream, generally representing 2-15% of the feed stream volume, contained 90% to 99% of the contaminants presented to the RO in the raw waste stream. Some constituents may have been near their solubility limits, and thus could not be reprocessed through the RO a second time. If the reject was returned to the plant, the high concentration of contaminants was undesirable. In the past, in the instance and application of radioactive waste, if the reject was further processed for disposal, the high concentration of contaminants might cause elevated radiation doses to personnel. In other instances, the high concentration of specific isotopes might cause an increase in waste classification from the desirable low Class A classification to Class B and C, resulting in more onerous packaging, shipping and disposal requirements. In past occurrences, the concentration of certain radioactive constituents caused the classification to be greater than Class C (GTCC), which precluded or denied disposal by any means.
Additionally, in instances where the reject volume was increased to preclude exceeding the solubility of raw waste stream constituents to prevent membrane fouling, the greater volume of reject resulted in increased secondary processing costs for such treatment processes as evaporation, drying or solidification. The increased reject volumes and secondary processing costs reduced the economic viability of the conventional RO-IX positional setup and process configuration.
Also, in non-nuclear applications these concentrated reject constituents precluded normal discharge to sanitary sewers, or return to the original body of water. If these existing permeate and reject stream problems could be solved, substantial operational and economical benefits would be realized, thus enhancing the value and utility of RO as a purifying method, including RO treatment of nuclear waste or process streams. Therefore, the teachings of the present invention were developed to overcome the problematic issues in the past technology regarding these matters, particularly with regard to processing and treatment of heat transfer and other radioactive liquids the subject of chemical change and reaction in a nuclear reactor.
Further, in this regard, in distinguishing over the past technology in this area, the present invention treats nuclear reactor cooling water or a heat transfer water from nuclear reactor cycles to remove radioactive metal ions. The present invention is designed to pass through as many of the nonradioactive components in the water as possible for the purpose of minimizing the quantity of radwaste generated for evaluation and other uses. By utilizing the gross demineralizer means of the present invention for active processing by ion exchange of the (AF) in front of the invention's polishing reverse osmosis (RO) step, the ionic exchange media of the gross demineralizing step of the invention accumulates more radioactive metals and the following (RO)-polishing step and means is protected from accumulating greater amounts of radioactive dose and emitting greater amounts of gamma emissions from such radiation to personnel working in the area.
Utilizing the ion exchange or ion capture of demineralization of the present invention in front of the RO also maximizes the utilization of the ion exchange media as the loading of as much radioactive metal ion as possible occurs. Using the ion exchange media after the RO, as done in prior art technology, often meant less than 60-70% utilization of the media and much lower loading of radioisotopes.
Additionally, Boron passage is maximized utilizing the present invention while past technology, such as Dagard (U.S. Pat. No. 5,082,618) entitled "Method and Device For Modifying the Concentration of the Soluble Poison Contained in the Cooling Fluid of the Primary Circuit of a Nuclear Reactor", decreased the passage of Boron. Importantly, Salts and nonradioactive metals are passed on through the present invention as much as possible to reduce the volume of radwaste generated. In this regard the present invention is utilized as the sole release point for liquid effluents from a nuclear power plant. Liquids must be released as a license condition for the operation of the plant. B10 (also referenced herein as B10 and boron-B10) is consumed as a neutron absorption agent to control the nuclear reaction and is converted to B11 (B11). While references such as the Dagard patent teach retaining B11 the present invention's method functions to remove the B11 and assist revitalization of the neutron absorption capacity (poison) of the reactor coolant with the addition of fresh B10.
To restate, though Dagard relates to PWR nuclear plants, its teachings clearly address the removal of boric acid (which it places within part of its definition or terminology as "poison") from the primary water of the plant. Distinguishably, the present invention addresses the passage of boric acid (the Dagard 'poison') through the membranes so as little as possible of the boric acid is removed. The clear intention of the present invention is not to modify the concentration of the boric acid, but to assure its element form as Boric Acid and pass it through along with salts and other non-radioactive components through the method's system as part of the environmentally protective quality water to be released to the environment as the sole aqueous waste stream; and, in so doing, to reduce the radwaste volume for use, storage or disposal without the need of past practices of drying and/or solidification to do so. Dagard addresses ion exchange, but only for the removal of boric acid regarding which the present method emphasizes minimization and elimination for so doing. Dagard also teaches the use of ammonia which would be detrimental to the present method because it causes decreased efficiency of the RO and demineralizers. Also, one of the express primary purposes of the present method and invention in removing radioisotopes or radioactive metal ions is not addressed in Dagard in any manner; nor would it be correct to assume in their disclosure that it would be obvious to address such a purpose.
Further, in non-analogous technology in relation to that of nuclear reactor liquid treatment, the Al-Samadi patent (U.S. Pat. No. 6,113,797), entitled "High Water Recovery Membrane Purification Process" utilizes a two stage RO process with pretreatment limited to filtration to deal with scaling elements such as calcium and magnesium. Distinguishably, the present invention does not have to deal with scaling issues since it utilizes, as a part of it's demineralization step, ion exchange to remove scaling metals and filtration to remove solids prior to the polishing RO step of the invention, along with serving the other purposes in the invention of aiding reduction of the amount of radioactive isotopes passing therethrough. The present invention further distinguishes over Al-Samadi in discharging 100% of the influent water entering the present method in the aqueous radioactive liquid as purified water, without the need for a separate waste liquid stream which could not be released to the environment.
Also, the Rosenberger invention (U.S. Pat. No. 7,067,057), entitled "Fluid Conveyed Material Collection System", discloses a device which does not teach the use of ion exchange in advance of RO, as the present invention does. It also teaches the use of further processing of RO concentrate to either dry solids or other solidification methods in great distinction to the present invention. Rosenberger also appears to require the use of precipitants. Rosenberger also teaches 'backflushing" which is not present and would achieve no purpose in the present invention in that it causes much additional 'tankage' and process interruptions that is unneeded and would be a great disadvantage if used in the present invention. Rosenberger also teaches that one or more streams from membrane processes require additional outside processing to bring the final materials to a disposable and dischargeable state. Also, in relation to the teachings of the present invention, the Rosenberger device's use of evaporation, electrode coagulation, centrifugation and precipitating agents makes the use of this device a more complex and capital intensive process. In this regard, at least two membrane systems are required for most applications set forth for the Rosenberger device.
Further in divergent and non-analogous technology in relation to treatment of a nuclear reactor liquid, the Mukhopadhyay patent (U.S. Pat. No. 6,537,456) entitled "Method and Apparatus For High Efficiency Reverse Osmosis Operation", does not disclose use of any recycle of its subject reject stream. Mukhopadhyay simply sets forth a process employing a very standard approach to RO which would not address the problems of seeking to emit a single waste stream of quality water to the environment as does the present invention and method. Though it appears that the Mukhopadhyay process employs the use of ion exchange media both in front and after the RO disclosed the reference does not in any way provide for recycle of any reject stream to the front of the system, as the present invention does to achieve the important purpose of improving the filtration of radioactive contaminants and allowing the salts and non-radioactive components to move through to ultimate clean water environmental disposal while allowing the volume of the radwaste to be significantly less for storage, use or disposal. In a similar regard, this patent reference teaches use of the RO as a gross separator rather than the specific relegation and limitation as in the present invention method to a "polisher" and sole use in a "polishing" capacity. Also, very importantly, Mukhopadhyay teaches the 'minimization' and strict limitation of boron and silica passage through its process, where the method of the present invention seeks to 'maximize' the passage of these substances for important object and purpose of the present invention as indicated to uniquely and significantly minimize the radioactive waste volume for later use, storage or disposal. Mukhopadhyay makes no attempt to address this problem and must be considered significantly non-analogous to the operation and chemical processes of a nuclear reactor for this reason among others. In dealing with chemical nuclear reactor processes in the past technology the reject volume issuing from a nuclear reactor posed a significant waste volume problem that had to normally be disposed in a nuclear application setting through either drying or solidification. The present invention uniquely and importantly provides a novel method, which might normally be unexpected by simply looking at the alignment of elements utilized in the present method and invention, to significantly solve the radioactive waste volume problem while still providing only one aqueous stream to be returned to the environment rather than to another location at the nuclear reactor site or for logistical placement, storage or disposal at a non-environmental location.
Each of the references above; or those like them, but also distinguishable; fail to teach important aspects of the method of the present invention. For example, each of the analogous or non-analogous references in the past technology failed to recognize the usefulness of using a more broad spectrum ion exchange media in front of the RO to capture all of the ions in a concentrated form such that the RO could be subsequently used as a polishing method step rather than as a primary separator. All of the references in the past technology in this or any remotely related area used the RO as a primary separator rather than as a polisher where the RO reject was then at a concentration that the primary ion exchange beds could remove it to reasonable levels. All of the other references also required significantly more equipment to provide the same permeate results, and all had a secondary waste other than membranes or media regarding which they had to account for and dispose.
Accordingly, it is an object of the present invention to provide a permeate stream or first liquid volume and a reject stream or second liquid volume, so that the reject stream is recycled back to the front of it's own system process of which it is a part of, or back to the nuclear reactor plant source, so that the repetitive effect of the invention's non-conventional gross demineralizer step in the present invention can be achieved; i.e., the removal percentage of demineralizers employed in such a system is great enough; to prevent excess buildup of most all isotopes and other fouling chemicals.
It is also an object of the invention, in preferred embodiments, to utilize a method and system in proximate location to the end of its novel gross demineralizer of (AF) processing step to specifically polish radwaste or radioactive wastewater from a radwaste system of a nuclear reactor of the remaining isotopes and other dissolved and colloidal materials, when present.
It is a further object of the invention to maximize boron control. In the present invention this is accomplished by passage or recycle through the invention's non-conventional polishing RO process step. This is done to meet the requirements necessary for discharge of an aqueous wastestream directly to the environment apart from the nuclear reactor site or recycle within the steps of the present method. This is accomplished, in part within the present method, by raising or lowering the pH for the purpose of altering the characteristics of the aqueous wastestream to assure formation and passage of boric acid with the waste stream of the invention released to the ambient environment outside a nuclear reactor site.
A further object exists in facilitating the periodic use of a chemical treatment system to precipitate the silica in the system, or capture the silica by selective ion exchange when required.
Further objects and advantages of the present invention include utilizing the RWRO post IX polisher therein of the invention; the advantageous use of carbon filters and ion exchange resins as good removal media for TOC found in the feed water; the reduction of TOC fouling of RO membranes; the use of deep bed carbon filtration ahead of demineralizers to reduce fouling as compared to mechanical filters conventionally used ahead of RO systems; the reduction of TSS fouling of RO membranes; the reduction of dose rate on RO system and membranes; the quality of the water discharged to the environment; and the maximization of resin utilization by exposing the resin to higher influent activity concentration and retaining resin until completely depleted; and the utilization of acid conditions by cation resin (i.e., hydrogen form cation resin before the RWRO) to reduce pH adjustment and improve BA passage.
Additional objects and benefits include: the reduction of volume rejected and returned to the nuclear reactor plant; the reduction in the waste classification of concentrates and/or resulting dried solids; the maximization of resin utilization by exposing resin to a higher influent activity concentration; the prevention of the return to the nuclear reactor plant, or environmental discharge, of difficult to remove isotopes; the facilitation of scavenging for and selective capturing or removal of targeted isotopes, such as antimony, Cobalt, Cesium, Iodine, Tellurium, Manganese, Iron, Silver, Chromium, and Niobium, and those related thereto in the nuclear cooling fluid and radwaste processes.
In a smaller waste stream, then provided as a result of the present process; and the decrease on osmotic load through the use of increased reject flow rate.
It is a further object of the invention to more effectively and efficiently provide for reduced radioisotope discharges, removal of secondary isotopes for discharge, and production of high quality water for recycle within the invention's process and release to the environment to allow retention of tritium.
It is a further object to provide effective boron recycle or for recycle of other non-radioactive elements for further processing within the invention's system.
A further object exists in providing a system which has application in dealing with RCRA wastewaters and recycle of regulated chemicals that can be discharged only in limited quantities.
It is the object of the present invention to provide a methodology of applying RO and ion exchange (IX) in such a functional and positional manner as to create more favorable operating conditions and performance of the RO and demineralizer (IX) by situating the demineralizer system ahead of the RO in a configuration referred to as IX-RO. In so doing, the RO acts as a polisher in follow-up to the gross demineralization step in the system. In the IX-RO configuration, often 90% to 99% of the contaminants will be removed by the IX system in advance of the RO polisher. A secondary configuration provides demineralization of the reject stream to further strip undesirable species from the reject before recycling or processing of the reject stream. These configurations result in improved RO performance and improved permeate and reject stream quality and conditions.
Another object and advantage of the invention includes IX scavenging of raw waste stream constituents that, when concentrated in the RO, could precipitate and foul the RO membranes. Reduction of such agents permits controlling the reject flow rates to meet the hydraulic needs of the membranes instead of adjustment to control internal RO precipitation, where such adjustments would result in reduced reject flow rates and volumes that must be recycled or treated.
A further object and advantage is served by IX scavenging of raw waste stream constituents, resulting in reduced concentration of contaminants in the reject stream. This favorable condition reduces the inventory of contaminants recycled within the process system itself. The lower concentration of reject contaminants permits reprocessing through the IX-RO system with reduced concern of precipitation.
Another object and advantage of the invention is set forth by IX scavenging of raw waste stream constituents, including reduction in the concentration of key isotopes that affect waste classification for waste packaging, shipping and burial. Reduction of these isotopes in the raw waste stream, results in advantageous and supportive reduction in the reject stream subject to secondary processing for disposal.
A further object and advantage of the invention is served by IX scavenging of raw waste stream constituents, including radioactive isotopes, to reduce mechanical entrapment of isotopes in the RO membranes and process equipment system.
Accordingly, the lower radioactive dose rates achieved through using the present method in nuclear reactor liquids to change their chemical makeup, volume and packaging reduce exposure to operating personnel. This also reduces the frequency of, or need for, cleaning RO membranes, which would normally be needed to address and lower accumulated substances causing radioactivity. This facilitates avoidance of exposure to personnel, which would otherwise be necessary for handling and packaging of expended membranes. Further objects and advantages of the invention are served by IX scavenging, i.e., gross demineralizing of contaminants from the reject stream to reduced isotopic content, resulting in reduced dose buildup during secondary processing within the present invention of the reject stream or volume. Particular isotopes; for example, cesium 137, cobalt 60, carbon 14, iron 55, nickel 63 and antimony 125, when present in elevated concentrations, may result in elevated waste classification imposed by the Nuclear Regulatory Commission and other governmental and regulatory bodies. This results in more onerous packaging, shipping and burial requirements. Scavenging, by IX-gross demineralizing, for these and other select isotopes from the reject stream enables maintenance of Class A classification, resulting in reduced handling and disposal costs.
Additional objects and advantages of the invention include IX scavenging of raw waste stream constituents, to reduce the concentration of contaminants presented to the RO. Lower RO influent contaminates results in reduced contaminant concentrations in the RO permeate. This reduces or eliminates the need for additional RO passes to effect cleanup of the process stream; or, in turn, reduces or eliminates the need for post-RO IX polishing of the permeate for discharge or recycle.
Other objects and advantages of the invention are served by IX scavenging of raw waste stream constituents to reduce the concentration of contaminants presented to the RO. This results in contaminants being affixed or captured by the IX-gross demineralizing step or being affixed or captured by the IX system of the invention. This is a more favorable and efficient waste form for handling, packaging and disposal.
An additional object of the invention, and advantage served, includes IX scavenging of raw waste stream constituents, where the RO acts as a polisher. This maximizes IX resin utilization by permitting IX beds to remain in service well beyond normal chemical depletion. Ionic leakage from partially or fully chemically depleted IX bed is either captured by downstream IX bed; or when passed to the RO, is rejected to the reject stream. This contribution to the reject stream, in this case, is sufficiently small, often 1% -2% of the influent stream contaminate total. This does not materially or adversely affect the quality and secondary processing of the reject stream.
A further object, and advantage, of the invention lies in maximizing resin utilization and consumption reduction wherein the IX beds are exposed to the maximum concentration of contaminants of the raw process stream. This results in a more complete utilization of the exchange capacity of the resin and higher exchange equilibrium. All of these things result in higher waste loading and reduced resin consumption, compared to IX performance when positioned in the dilute contaminant stream of the RO permeate as was the case in the past conventional technology.
Another object of the invention is to set forth IX positioning in advance of the RO to enhance boron passage through the RO membranes. This enhanced passage is affected by pH reduction as the process stream passes through hydrogen form cation resin or by addition of acids, such as sulfuric or hydrochloric, to the process stream. Passage of a greater fraction of the boron to the permeate permits recovery of boron in the permeate and reduces the concentration in the reject stream. This avoids RO operating limitations imposed by the potential for precipitation of boron; and also reduces the resulting dried waste volumes due to reduced boron content. In the alternative, when minimizing boric acid in the permeate; the pH can be increased by passing the process stream through a hydroxide form anion resin or by addition of a basic solution such as sodium hydroxide.
A further object includes setting forth a system where the IX position is placed in advance of the RO, in facilitating the periodic use of a chemical treatment system to precipitate silica in the IX system, or for capturing the silica by selective ion exchange when required or appropriate. An additional object is to set forth in the present method and system where the IX position is placed in advance of the RO in facilitating improved TOC removal from carbon filters downstream. When employed such carbon filters have the primary purpose in filtration and TOC removal. The use of IX aids in removal of that fraction of TOC that successfully transits the carbon filter. This protects the downstream RO from TOC contamination (a primary membrane fouling mechanism).
Yet a further object of the invention includes presenting a system and process that provides the further advantage of utilizing the RWRO as a post IX polisher in the invention. Other related advantages, in this regard, include the advantageous use of carbon filters and ion exchange resins as removal media for TOC found in the feed water; the reduction of TOC fouling of RO membranes; the use of deep bed carbon filtration ahead of demineralizers to reduce fouling as compared to mechanical filters conventionally used ahead of RO systems; the reduction of TSS fouling of RO membranes; the reduction of dose rate on RO system and membranes; the reduction of activity returned to the plant or discharged to the environment; the maximization of resin utilization by exposing the resin to higher influent activity concentration and retaining resin until completely depleted; and the utilization of acid conditions when needed.
It will, therefore, be understood by those skilled in these technologies that substantial and distinguishable device, process and functional advantages are realized in the present invention over the past conventional technology with regard to processing, treating, packaging and chemically affecting a radwaste liquid in a nuclear reactor. It will also be appreciated that the efficiency, flexibility, adaptability of operation, diverse utility, and distinguishable functional applications of the present invention all serve as important bases for novelty of the invention, in this field of technology.

Method of rendering a radioactive and aqueous heat transfer liquid in a nuclear reactor to a reduced radwaste quantitative state and returning the remaining waste water volumes to an environmental release point for liquid effluents