Pneumatic Sample Transfer System

The pneumatic transfer (rabbit) system is our most frequently used experimental facility. It is used to rapidly transfer samples to and from the reactor core. It consists of three rabbit tubes, one of which is cadmium lined to allow for only high energy neutrons to pass through. The rabbit tubes fit into the grid plate in a manner similar to that of a fuel element and are positioned near the edge of the core. Two of the transfer tubes terminate in a glove box next to the reactor pool where samples are loaded and removed from the system. The remaining tube extends to shielded enclosures (referred to as “hot cells”) in the basement experiment area. One of the shielded enclosures contains a revolver to load and can exchange multiple samples, while the other may be used as part of a spectroscopy facility. The rabbit system is controlled by a digital control system in the control room to allow for precise irradiation amounts.

Thermal Column

Our thermal column is a large (3.5ft x 3.5ftx x5.75ft) graphite block that protrudes through the pool wall and sits behind the reactor core. It serves two main functions at the reactor. First, it acts as a reflector for the core. Given a specific core configuration, there are two modes of operation - "W-mode" and "T-mode". In "T-mode", the reactor core is moved closer to the thermal column, allowing for an increased excess reactivity without changing the core layout. The second function of the thermal column is as an experimental facility. The thermal column provides a readily accessible field of thermal neutrons for experimental purposes. On the back of the thermal column, the assembly consists of a door that opens into the basement experimental level, a graphite assembly, and a shield. Total shielding from the reactor core through the thermal column to the outer biological wall face is roughly equivalent to that which would be provided by the intervening water and biological pool wall.

Experiment Fuel Assemblies

Our reactor features two different in-core fuel assemblies for experimental use: The Isotope Production and Core Access Element. These unfueled assemblies are similar in shape to the fuel elements and can be placed in various grid plate locations in the core.

The isotope production element is used to provide access to the inner and outer parts of the core. It is filled with graphite and has a hole passing through it to permit a neutron start-up source or an experiment to be inserted into the core. The graphite is entirely clad in aluminum, with the inner cladding forming an aluminum tube. The element may be used as a wet or dry irradiation facility.

The core access element is also used to provide access to the inner and outer parts of the reactor core and is a dry irradiation facility. The assembly consists of a hollow piece of graphite clad entirely in aluminum. The top portion of the assembly accommodates an aluminum tube which projects upwards above the pool water level. Samples for irradiation are lowered down the pipe on the end of a leader.

Beam Port

A stepped beam port provides a beam of reactor neutrons for experimental purposes. The beam port protrudes through the pool wall and extends into the reactor pool near the core, with the open end of the beam tube ending in the basement experimental area. Operations required to remove or install equipment from the beam port are performed from the basement experimental area. A shutter assembly is used to achieve a collimated beam of neutrons. It consists of a plug containing a beam guide and a shutter which provides an extension to the beam guide in the "Open" position and a radiation shield in the "Closed" position, with both positions being controlled remotely in the control room. The beam tube is constructed of aluminum and is closed at the reactor end, with stainless steel and lead linings to protect against radiation.