Validation of ALEPH2 burn-up code using benchmarks from SFCOMPO

Abstract

Spent Nuclear Fuel (SNF), irradiated nuclear fuel, is highly radioactive and dangerous when not handled correctly. An accurate characterization of SNF, in terms of nuclide composition, gives the possibility to accurately quantify integral responses such as decay heat, neutron and gamma emission, and criticality for its safe handling, transport, and storage. So-called depletion codes are used to predict these nuclide compositions. ALEPH2 is a Monte-Carlo depletion code developed by SCK CEN since 2004. In the past, ALEPH2 has been validated to solve a limited number of light water reactor (LWR) cases. As a part of its maintenance and verification process, a continuous work of validation against experimental measurements is needed. In this Master’s thesis, a validation exercise was performed by simulating several LWR SNF benchmark cases using the experimental assay data available in SFCOMPO, a database developed and maintained by the OECD/NEA. Experimentally measured nuclide compositions were compared against ALEPH2 predictions. Initially, a simple model was developed for each case, which, after analysis, was refined. A good agreement between calculated nuclide concentrations and measured data was found, hence validating ALEPH2 capabilities to provide good representation of the actual nuclide composition.