Nondestructive evaluation of transient fission gas release from a pulse-irradiated PWR segment fuel by counting krypton 85

Abstract

An experimental study was made in the Nuclear Safety Research Reactor at JAERI to evaluate transient fission gas release (FGR) from high burn-up PWR type fuel rods using a nondestructive technique, the counting of radioactive 85Kr in the fuel plenum. Within the scope of this experiment, the following results were obtained: (1) By using the pulse irradiation technique, the radioactivity of 85Kr in fuel plenum became measurable. (2) Data from 85Kr counting correlated well with those from gas obtained from puncturing; where the gas obtained by puncturing resulted from transient FGRs ranging 0.6 to approximately 12%. (3) The significant increase of FGR detected following pulse irradiation is considered to result from the development of microcracks in the peripheries of the fuel pellets.