which is a pin-type Low Enriched Uranium natural circulation driven LWR, with a very strong negative temperature coefficient. As such, it is impossible to overheat the reactor, even in the case of a sudden reactivity insertion. Irradiation facilities Irradiation facilities include equipment that is used to place, move, and organize samples that are to be irradiated. Pneumatic transfer system The pneumatic transfer system (known colloquially as the "rabbit system") consists of an irradiation chamber in the outer ring of the core with its associated pump and piping. This allows samples to be transferred in and out of the reactor core very rapidly, while the reactor is at power. Routine use of the pneumatic transfer system involves placing samples into vials, which in turn are placed in special capsules known as "rabbits." The capsule is loaded into the system in the radiochemistry laboratory next to the reactor and is then transferred pneumatically into the core-irradiation position for a predetermined time. At the end of this period, the sample is transferred back to the receiving terminal, where it is removed for measurement. The transfer time from the core to the terminal is less than seven seconds, making this method of irradiating samples particularly useful for experiments involving radioisotopes with short half-lives. The flux in the core terminal is approximately 5x1012 n/cm2/s when the reactor is at full power. Rotating specimen rack The rotating specimen rack (lazy susan) is located in a well on top of the graphite reflector which surrounds the core. The rack consists of a circular array of 40 tubular receptacles. Each receptacle can accommodate two TRIGA-type irradiation tubes, so that up to 80 separate samples may be irradiated at any one time. Vials holding up to ( internal diameter, long) are routinely used in this system. Depending upon its geometry, a sample up to about could be irradiated by joining two vials. Samples are loaded in the specimen rack prior to the start-up of the reactor. The rack automatically rotates during irradiation to ensure each sample receives the same neutron flux. Typically, the rotating rack is used by researchers when longer irradiation times (generally greater than five minutes) are required. The average thermal neutron flux in the rotating rack position is approximately 2×1012 n/cm2/s with a cadmium ratio of 6.0 at full power. The specimen rack can also be used for gamma irradiations when the reactor is shut down.