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Title: Influence of burnup on heat-rating-to-melting for UO/sub 2/-PuO/sub 2/ fuel

Conference ·
OSTI ID:6515714

This paper summarizes the results of an irradiation test (HEDL-P-20) conducted to evaluate the influence of burnup on the linear heat rating to incipient fuel melting, Q'/sub m/, for 75% UO/sub 2/-25% PuO/sub 2/ fuel. The very short term irradiation was conducted in Row 1 of the EBR-II to simulate 115% of FTR full power using an irradiation history similar to that used for the HEDL-P-19 test. Prototypic FTR fuel pins (0.230 in. O.D., type 316, 20% cw stainless steel) were included that were pre-irradiated to 0% BU, 0.3% Bu, 0.7% BU, and 1% BU at a simulated 100% FTR power. One 0.250 in. O.D. pin (PNL-2-5) clad with type 304 stainless steel was also included that was preirradiated to approx. 7% BU. Fuel-cladding diametral gap sizes were varied from 3.5 to 7.5 mils (the FTR range) by centerless grinding the pellets to different diameters, helium and 80He + 20 Xe fill gases were used, and as-built fuel microstructure was also a test variable. The preirradiation of the 0.230 in. O.D. pins was done in Row 3 of the EBR-II for one reactor cycle and one-half reactor cycle, respectively. All seven of the 0.230 in. O.D., ''fresh'', pins had extensive fuel melting, but fuel melting was indicated in only one of the preirradiated pins. This pin was fabricated with a 3.5 mil gap and preirradiated to approx. 0.3% BU. Similar pins preirradiated to 0.7% BU and 1% BU showed no melting. The high burnup PNL-2-5 pin (0.250 in. O.D.) also had fuel melting, but this is believed to be due to the 20% higher heat generation rate in this larger pin, rather than to a reduction in thermal performance at very high burnup.

Research Organization:
Westinghouse Hanford Co., Richland, WA (United States)
DOE Contract Number:
EY-76-C-14-2170
OSTI ID:
6515714
Report Number(s):
HEDL-SA-737; CONF-7411116-1
Resource Relation:
Conference: ANS winter meeting, Washington, DC, USA, Nov 1974
Country of Publication:
United States
Language:
English