Abstract
In coupled calculations with Monte Carlo neutronics and thermal hydraulics the Monte Carlo code is used to produce a power distribution which in practice means tallying the energy deposition. Usually the energy deposition is estimated by making a simple approximation that energy is deposited only in fission reactions. The goal of this work is to study how the accuracy of energy deposition modelling affects the results of steady state coupled calculations. For this task an internal coupling between Monte Carlo transport code Serpent 2 and subchannel code SUBCHANFLOW is used along with a recently implemented energy deposition treatment of Serpent 2. The new treatment offers four energy deposition modes each of which offers a different combination of accuracy and required computational time. As a test case, a 3D PWR fuel assembly is modelled with different energy deposition modes. The resulting effective multiplication factors are within 30 pcm. Differences of up to 100K are observed in the fuel temperatures.
Highlights
In the recent years with the increase in the available computational resources, there has been a strong interest to develop high definition approaches to tackle coupled neutronics/thermal hydraulics problems
It should be noted that with all energy deposition modes normalization to total power was used in Serpent which means that only the power distribution varied between the different modes and the total power produced in the problem geometry was the same with all modes
A stochastic approximation based relaxation scheme [9] was used for the power and all Serpent calculations were run with ENDF/B-VII.1 based cross section library
Summary
In the recent years with the increase in the available computational resources, there has been a strong interest to develop high definition approaches to tackle coupled neutronics/thermal hydraulics problems. The thermal hydraulics part of these problems is usually solved with CFD or subchannel codes and neutronics with Monte Carlo codes. To be more specific in the coupled calculations the Monte Carlo code is used to produce a power distribution which in practise means tallying the energy deposition. This task can be achieved using different methods having varying accuracy. Radiative capture reactions usually contribute a non-negligible amount to the total energy release
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