Testing of full-sized reduced-enrichment elements in the ORR

Experimental high-density, reduced-enrichment fuel elements were irradiated in the Oak Ridge Research Reactor (ORR) to confirm their expected satisfactory performance in this medium-powered research reactor. This expectation of good performance was based on previous irradiations of miniature-sized plates in this and other reactors. A total of 21 elements were irradiated as described in the paper. These elements were fabricated by commercial manufacturers and, except where noted, were identical in appearance to the standard highly enriched ORR element that contains 19 curved plates. The elements were shuffled to several positions in the reactor during the course of their irradiation, similar to the handling of regular elements. The 13 plate elements were placed in low-flux positions during their initial testing due to their higher metal/water ratios. All of the elements were irradiated to the burnup normally achieved by typical ORR elements of ∼ 50% depletion of the original 235U in the element. Some elements of each type were extended beyond this burnup to average depletions of 72 to 82%. The elements were periodically inspected for coolant channel thickness between irradiation cycles to provide early detection of excessive plate swelling or warpage. No problems were detected. The elements underwent postirradiation examination (PIE) at the High Radiation Level Examination Laboratory at Oak Ridge National Laboratory. All of the elements were judged to have performed satisfactorily during irradiation based on the PIE