Experimental Fission Gas Release Determination at High Burnup by Means of Gamma Measurements on Fuel Rods in OL2

摘要

In February 2008, gamma measurements for Fission Gas Release were performed on a selection of rods from two Westinghouse SVEA96S-Optima/L fuel assemblies in Olkiluoto unit 2. In total, 22 fuel rods were measured from two assemblies which had been loaded into the Olkiluoto unit 2 core in 2002 and 2003 and discharged in May 2007, after four and five annual cycles. Assembly average burnups were 50.3 and 50.8 MWd/kgU, respectively. Rods were chosen for measurement in order to be representative of as many combinations of conditions as possible in fuel rod design, predicted fission gas release in percent (FGR), operating history, etc. The measurements were carried out by Westinghouse Electric Sweden AB (WSE) and funded by Teollisuuden Voima Oyj (TVO). The measurements are part of TVO's high burnup research program for fuel types currently used at Olkiluoto units I and 2 to support an increase in the licensed burnup. The emphasis in TVO's high burnup program is to quantify the key phenomena that may become limiting at high burnup, such as cladding oxidation, fission gas release, and dimensional changes of fuel components.