	Introduction

A "pit" is the core of the primary stage of a thermonuclear weapon. Detonating the pit provides the energy to detonate a weapon's secondary stage. During the Cold War, the Rocky Flats Plant (CO) made up to 2,000 pits accepted for use in the stockpile per year. Since then, the United States has made 29 such pits in total. Yet the Department of Defense (DOD) stated it needed the National Nuclear Security Administration (NNSA), the separately organized agency within the Department of Energy (DOE) that maintains the U.S. nuclear stockpile, to have the capacity to produce 50 to 80 pits per year (ppy). Pits are to be made at Los Alamos National Laboratory (LANL, NM) in the PF-4 building, potentially in proposed smaller structures called modules connected to PF-4 by tunnels, or in both. Producing 80 ppy requires enough "Material At Risk" (MAR) and space. Space is laboratory floor space available for plutonium operations. There are figures for available space and MAR, but figures for space and MAR required to produce 80 ppy have never been calculated rigorously , so this report cannot determine what options would provide enough margin for producing 80 ppy. Nor can it address whether certain options could meet the 2027 date because time to implement them cannot be determined. Instead, the report presents 16 options that increase the feasibility of producing at a rate of 80 ppy rate by 2027. Improve Modeling of Atmospheric Dispersion of Plutonium

NNSA calculates dose to an MEOI from an accident at PF-4 using computer models. Harmonizing MAR and time of day would reduce calculated dose. That reduction, if incorporated into PF-4's safety documents, would permit more than doubling the MAR permitted in PF-4. Yet an increase in the MAR ceiling in PF-4 by a factor of less than ten, and perhaps less than two, would probably permit enough MAR for production of 80 pits per year in PF-4. Yet a substantial amount of plutonium on PF-4's lab space is in process. One way to reduce space and MAR required for AC is to analyze fewer samples per pit. That would enable fewer pieces of equipment to support a given rate of production, reducing space requirements and cost and increasing throughput; would make it more likely that RLUOB could perform most AC needed, which would reduce the amount of AC that would have to be done in PF-4; and would reduce waste generated per pit, reducing the load on AC and on waste processing. A process ("salt scrub") can remove most of the rest of the plutonium from the calcium chloride-plutonium mixture. Remove Americium from Plutonium

Weapons-grade plutonium (WGPu) consists of several plutonium isotopes. Since Pu-241 decay is the only source of Am-241, after passing aged plutonium through a final run of metal chlorination to remove Am-241, so little Pu-241 would remain that even if it all decayed to Am-241, the latter would never reach the level in 30-year-old WGPu, and the weapons laboratories have certified weapons with pits that old and older as acceptable for use in the stockpile. This final run would greatly reduce worker exposure. To increase MAR, reduce potential dose, and reduce the risk of collapse, LANL is taking steps to strengthen PF-4 seismically. Build One Module for Plutonium-238 Work

Plutonium-238 (Pu-238) is highly radioactive. On the other hand, some lessons from building a module might increase cost. One option by itself will not suffice to meet that requirement. As a result, NNSA faces the prospect of assembling a package of options, and Congress faces the prospect of evaluating, perhaps amending, and approving it. Any package would need to optimize among such goals as margin, cost, worker safety, and throughput. Using a different wind model and more realistic assumptions could reduce calculated dose by more than half in a major accident at PF-4, permitting more than doubling the MAR allowance for PF-4 quickly and at essentially no cost. What is the risk-benefit balance? In sum, while arriving at a satisfactory package will require complex analyses, many options offer the potential to boost U.S. pit production capacity toward, if not to, the congressionally mandated requirement of 80 pits per year by 2027.
A pit is the plutonium core of a thermonuclear weapon. Imploding it with conventional explosives provides the energy to detonate the rest of the weapon. The Rocky Flats Plant made up to 2,000 pits per year (ppy) through 1989; since then, the United States has made 29 pits for the stockpile. Yet the FY2015 National Defense Authorization Act requires the National Nuclear Security Administration (NNSA), which manages the nuclear weapons program, to produce at a rate of 80 ppy for 90 days in 2027. How can that requirement be met?
Pits are to be made at Los Alamos National Laboratory's main plutonium facility, PF-4. To manufacture pits, a facility must have enough laboratory floor space and a high enough limit for Material At Risk (MAR), the amount of radioactive material a worst-case accident could release. Producing 80 ppy requires enough "margin," the space or MAR available to produce pits minus space or MAR required for that production rate. While space and MAR available have been calculated, amounts required to produce 80 ppy have never been calculated rigorously, leaving space and MAR needs undefined. Although CRS cannot address whether certain options could meet the 2027 date because time to implement them cannot be determined, this report presents 16 options that seek to increase the feasibility of producing 80 ppy by 2027, including:
The radiation dose an individual would receive from a worst-case accident determines MAR permitted in PF-4. A ten-factor equation calculates dose as a function of MAR. NNSA uses worst-case values in this equation, yet median values may provide sufficient conservatism. Median values reduce calculated dose by orders of magnitude, permitting a large increase in PF-4 MAR. Yet merely doubling permitted MAR might suffice for producing 80 ppy. Providing this increase through construction at PF-4 could be costly and take years. In determining MAR for PF-4, the closest offsite individual is at a nearby trailer park. Relocating it would place the next closest individual farther away. The added distance would reduce dose, permitting increased MAR in PF-4. Using a different meteorological model and different assumptions would greatly reduce the currently calculated dose, perhaps permitting doubling PF-4 MAR. Plutonium decays radioactively, creating elements that various processes remove to purify plutonium. One process generates byproducts; plutonium is recovered from them with processes that take space and MAR. Since the United States has tons of plutonium surplus to defense needs, byproducts could be dispositioned as waste. Pits use weapons-grade plutonium (WGPu). U.S. WGPu is about 50 years old. About nine-tenths of plutonium-241, a WGPu isotope, decays to americium-241 in that time. Since plutonium-241 is the source of americium-241 in WGPu, removing the current americium-241 would prevent WGPu from ever reaching its americium-241 limit, permitting reduction in equipment for that process and reducing worker radiation exposure. A plutonium isotope used in space probes, plutonium-238, is extremely radioactive. It accounts for a small quantity of PF-4 plutonium but a quarter of PF-4's MAR. Building a "module" near PF-4 for plutonium-238 work would free MAR and space in PF-4, so one module might suffice instead of two or three. To reduce risk of collapse, loss of life, and radiation release from an earthquake, NNSA increased the seismic resilience of PF-4. More steps are planned; more could be taken.
Many options may boost U.S. pit production capacity, but none by itself could meet capacity and schedule requirements. NNSA therefore faces the prospect of assembling a package of options, and Congress faces the prospect of evaluating, perhaps amending, and approving it. Arriving at a satisfactory package will require complex analyses to optimize among such goals as margin, cost, worker safety, and throughput. At issue for Congress: What are the risks, costs, and benefits of the options? What is the optimum package?
This report is a condensed version of CRS Report R44033, Nuclear Weapon "Pit" Production: Options to Help Meet a Congressional Requirement, by [author name scrubbed].