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Title: Westinghouse Fuel Assemblies Performance after Operation in South-Ukraine NPP Mixed Core

The evaluation of WWER-1000 Westinghouse fuel performance was done using the results of post–irradiation examinations of six LTAs and the WFA reload batches that have operated normally in mixed cores at South-Ukraine NPP, Unit-3 and Unit-2. The data on WFA/LTA elongation, FR growth and bow, WFA bow and twist, RCCA drag force and drag work, RCCA drop time, FR cladding integrity as well as the visual observation of fuel assemblies obtained during the 2006-2012 outages was utilized. The analysis of the measured data showed that assembly growth, FR bow, irradiation growth, and Zr-1%Nb grid and ZIRLO cladding corrosion lies within the design limits. The RCCA drop time measured for the LTA/WFA is about 1.9 s at BOC and practically does not change at EOC. The measured WFA bow and twist, and data of drag work on RCCA insertion showed that the WFA deformation in the mixed core is mostly controlled by the distortion of Russian FAs (TVSA) having the higher lateral stiffness. The visual inspection of WFAs carried out during the 2012 outages revealed some damage to the Zr-1%Nb grid outer strap for some WFAs during the loading sequence. The performed fundamental investigations allowed identifying the root cause of gridmore » outer strap deformation and proposing the WFA design modifications for preventing damage to SG at a 225 kg handling trip limit.« less
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Resource Relation:
Conference: 10th International Conference on WWER Fuel Performance, Modelling and Experimental Support, September 7-14, 2013, Sandanski, Bulgaria , Paper No. INIS-BG--1602
International Atomic Energy Agency, Vienna, Austria.
Research Org:
Pacific Northwest National Laboratory (PNNL), Richland, WA (US)
Sponsoring Org:
Country of Publication:
United States
Westinghouse fuel assembly (WFA), Lead Test Assembly (LTA), Rod cluster control assembly (RCCA), fuel rod (FR), ZIRLO, burnup, spacer grid (SG), drag force; drag work; assembly distortion; beginning-of-cycle (BOC); end-of-cycle (EOC)