The objective of this paper is to present the methodological orientations to determine accurately the uncertainty associated with the DARWIN2.3 decay heat calculation. It has also been validated for decay heat calculations on a more limited number of experimental programs based on elementary fission burst experiments and two integral calorimetric experiments, the MERCI-1 and CLAB experiments. The package has been extensively validated on a large number of experimental programs based on spent fuel chemical analyses that have been carried out in France since 1993. This package is being developed by the CEA with the support of its French partners (EDF, Orano and Framatome) it is the French reference for fuel cycle studies. The parameters required for fuel cycle applications – decay heat but also fuel inventory, activity, neutron, gamma, alpha and beta sources and spectra, radiotoxicity – are provided by the DARWIN2.3 calculation package. Therefore, accurate control of the decay heat calculation is essential for all the PWRs in the French reactor infrastructure (UOX and MOX fuels with 235U enrichments ranging from 1.0 to 5.0 wt.% and average plutonium contents ranging from 4.0 to 11.0 wt.%) over a wide range of cooling times (starting immediately with the moment after reactor shutdown and lasting up to more than 300 000 years). It also imposes delays before the different stages of fuel unloading, storage and transportation (from 5 days to 10 years) until reaching the reprocessing steps or vitrification processes and final storage (ranging from 4 years to more than 300 000 years). Indeed, decay heat is a dimensioning parameter for normal and emergency cooling systems of the nuclear core after shutdown (up to 8 days) for a reactor in operation. Decay heat is thus an important parameter for the safety demonstration of reactor operation under normal or accidental conditions and back-end nuclear cycle. Heat removal is one of the 3 key reactor safety functions, the other two being radioactivity containment and nuclear chain reaction control. 40 MW for a 900 MW e Pressurized Water Reactor (PWR). Decay heat reaches about 7% of the nominal power one second after reactor shutdown and is still about 1.5% of the nominal power one hour later, i.e. The delayed fissions caused by delayed neutrons contribute significantly to the decay heat up to 100 seconds after reactor shutdown. Nuclear decay heat is released by both radioactive decay of unstable fuel and material structure isotopes after reactor shutdown. ![]() This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( ), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. This paper focuses on the strategy that could be used to resolve this issue with the complement and the exploitation of the DARWIN2.3 experimental validation. Therefore, the uncertainty quantification step is of paramount importance in order to increase the reliability and accuracy of decay heat calculations. ![]() ![]() The experimental validation currently covers PWR UOX fuels for cooling times only between 45 minutes and 42 days, and between 13 and 23 years. For the parameter “decay heat”, there are few integral experiments available to ensure the experimental validation over the whole range of parameters needed to cover the French reactor infrastructure (fissile content, burnup, fuel, cooling time). The VVUQ ensures that the parameters of interest computed with the DARWIN2.3 package have been validated over measurements and that biases and uncertainties have been quantified for a particular domain. The DARWIN2.3 package benefits from a Verification, Validation and Uncertainty Quantification (VVUQ) process. An accurate computation of its value has been carried out at the CEA within the framework of the DARWIN2.3 package. Jordan Huyghe 1 *, Vanessa Vallet 1, David Lecarpentier 2, Christelle Reynard-Carette 3 and Claire Vaglio-Gaudard 1ĬEA, DEN, DER Cadarache, 13108 Saint Paul-lez-Durance, FranceĮDF Research and Development, 7 Boulevard Gaspard Monge, 91120 Palaiseau, FranceĪix Marseille Univ., Université de Toulon, CNRS, IM2NP, Marseille, Franceĭecay heat is a crucial issue for in-core safety after reactor shutdown and the back-end cycle.
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