Irradiation testing of miniature fuel plates for the RERTR program

An irradiation test facility, which provides a test bed for irradiating a variety of miniature fuel plates miniplates) for the Reduced Enrichment Research and Test Reactors (RERTR) program, has been placed into operation. The objective of these tests is to screen various candidate fuel materials as to their suitability for replacing the highly enriched uranium fuel materials currently used by the world's test and research reactors with a lower enrichment fuel material, without significantly degrading reactor operating characteristics and power levels. The use of low uranium enrichment of about 20% 235U in place of highly enriched fuel for these reactors would reduce the potential for 235U diversion. Fuel materials currently being evaluated in this first phase of these screening tests include aluminum-base dispersion-type fuel plates with fuel cores of 1) high uranium content U3)8-Al being developed by ORNL, 2) high uranium content UAIx-Al being developed by EG and G Idaho, Inc., and 3) very high uranium content U3Si-Al- being developed by ANL. The miniplates are 115-mm long by 50-mm wide with overall plate thicknesses of 1.27 or 1.52 mm. The fuel core dimensions vary according to overall plate thicknesses with a minimal clad thickness requirement of 0.20 mm. Sixty such miniplates (thirty of each thickness) can be irradiated in one test facility. The irradiation test facility, designated as HFED-1 is operating in core position E-7 in the Oak Ridge Research Reactor (ORR), a 30-MW water-moderated reactor. The peak neutron flux measured for this experiment is 1.96 x 1018 neutrons m-2 s-1. The various types of miniplates will achieve burnups of up to approximately 2.2x1027 fissions/m3 of fuel, which will require approximately eight full power months of irradiation. During reactor shutdown periods, the experiment is removed from the reactor, moved to a special poolside station, disassembled, and inspected for dimensional changes, blisters, or any other visible defect. After inspection the experiment is reassembled and reinserted into the reactor for further irradiation. At completion of the specified in reactor exposure of the miniplates, the experiment will be disassembled, and the irradiated samples will be returned to the respective fuel plate fabricators for detailed postirradiation examination. Ultimately, fuel plate types with suitable characteristics will be manufactured into full-sized plate-type fuel elemental suitable for testing in the ORR. (author)