Abstract
The removal of decay heat is a significant safety concern in nuclear engineering for the operation of a nuclear reactor both in normal and accidental conditions and for intermediate and long term waste storage facilities. The correct evaluation of the decay heat produced by an irradiated material requires first of all the calculation of the composition of the irradiated material by depletion codes such as VESTA 2.1, currently under development at IRSN in France. A set of PWR assembly decay heat measurements performed by the Swedish Central Interim Storage Facility (CLAB) located in Oskarshamm (Sweden) have been calculated using different nuclear data libraries: ENDF/B-VII.0, JEFF-3.1, JEFF-3.2 and JEFF-3.3T1. Using these nuclear data libraries, VESTA 2.1 calculates the assembly decay heat for almost all cases within 4% of the measured decay heat. On average, the ENDF/B-VII.0 calculated decay heat values appear to give a systematic underestimation of only 0.5%. When using the JEFF-3.1 library, this results a systematic underestimation of about 2%. By switching to the JEFF-3.2 library, this systematic underestimation is improved slighty (up to 1.5%). The changes made in the JEFF-3.3T1 beta library appear to be overcorrecting, as the systematic underestimation is transformed into a systematic overestimation of about 1.5%.
Highlights
Isotopic characterisation of irradiated fuel via depletion and decay calculations is essential in reactor core neutronics and safety calculations
This is especially important for the calculation of the temporal evolution of the power distribution and the reactor kinetics parameters and for the evaluation of the residual decay heat produced by the fuel assemblies in the core of a nuclear reactor as a function of time
The experiments that have been selected for this work are PWR assembly decay heat measurements performed by the Swedish Central Interim Storage Facility (CLAB) located in Oskarshamm (Sweden) [4]
Summary
Isotopic characterisation of irradiated fuel via depletion and decay calculations is essential in reactor core neutronics and safety calculations This is especially important for the calculation of the temporal evolution of the power distribution and the reactor kinetics parameters and for the evaluation of the residual decay heat produced by the fuel assemblies in the core of a nuclear reactor as a function of time. Ti,1/2 the half life of nuclide i given in seconds; Ni the concentration of nuclide i for the irradiated material in atoms·gHM−1 For depletion codes such as VESTA [1] that are used for decay heat estimations, experimental validation is paramount. We will further illustrate this aspect in this paper by comparing the results for the decay heat measurements from the VESTA experimental validation database using four nuclear data libraries, namely JEFF-3.1, JEFF3.2, JEFF-3.3T1 and ENDF/B-VII.0. The experiments that have been selected for this work are PWR assembly decay heat measurements performed by the Swedish Central Interim Storage Facility (CLAB) located in Oskarshamm (Sweden) [4]
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