INVENTORY AND DECAY HEAT CALCULATIONS FOR 4.0 % VVER-440 FUEL ASSEMBLY USING THE CODES SERPENT AND SNF
24th Symposium of AER on VVER Reactor Physics and Reactor Safety (2014, Sochi, Russia)
Nuclear fuel cycle perspectives and sustainability and intermediate storage of spent fuel, decommissioning and rad waste
Abstract
INVENTORY AND DECAY HEAT CALCULATIONS FOR 4.0 % VVER-440 FUEL ASSEMBLY USING THE CODES SERPENT AND SNF
Tuukka Lahtinen
Fortum Power and Heat Ltd, Espoo, Finland
tuukka.lahtinen@fortum.com
ABSTRACT
As accurate as possible computational information on decay heat power of irradiated nuclear fuel is of essential importance in various applications at NPP. The approach of not only examining the decay heat power as an integral quantity but also modeling the composition of the fuel elaborately on a nuclide-specific level provides valuable information which is, in addition to pure decay heat analyses, also applicable in various other areas.
In this study, a single 4.0 % enriched VVER-440 fuel assembly is modeled in a 2D geometry. The assembly is irradiated up to 50 MWd/kgU burn-up using a simplified irradiation history by keeping the parameter values of the fuel and coolant properties constant. The study aims at comparison of the decay heat powers and nuclide inventories resulting from the simulations that are carried out using the Serpent and SNF codes.
In addition to comparison of results in the nominal conditions case, also variation cases are examined. In these cases, irradiation parameter values are deviated from the nominal ones and the impact on the time-dependent decay heat power on a nuclide-level is examined.
The current version of the SNF code is capable of modeling 357 radionuclides that are important decay heat contributors at least during some limited decay-time period. On the other hand, the nuclear data libraries applied in the Serpent Monte Carlo code, include neutron interaction data for over 400 and radioactive decay data for over 3800 nuclides. The comparison of the results between the two codes provide data which, among other things, can be used to verify that the full depletion calculation chain behind the utilization of the SNF code, is capable to model all the relevant decay heat nuclides.