A simple implicit coupling scheme for Monte Carlo neutronics and isotopic depletion

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Parks, GT 

The stochastic implicit Euler scheme and its variants can be used to prevent non-physical behaviour that may emerge when coupling Monte Carlo neutron transport and isotopic depletion solvers for spatially-decoupled reactor problems. However, stochastic implicit methods tend to require many iterations to obtain a stable solution. This paper demonstrates that this is due to using a sub-optimal relaxation scheme: rather than using a variable relaxation factor, a fixed relaxation factor can give a more stable solution in fewer iterations. Furthermore, like stochastic implicit schemes, even though multiple transport solutions are required, using a fixed relaxation factor allows computational effort to be reduced by lowering the number of particles simulated during the corrector step while still providing stable results. This shows that using a fixed relaxation factor to stabilise Monte Carlo burn-up calculations can be more effective than applying the stochastic approximation.

Depletion, Neutron transport, Monte Carlo, Stability
Journal Title
Annals of Nuclear Energy
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Elsevier BV
EPSRC (1818942)
Engineering and Physical Sciences Research Council (EP/L015900/1)
This work was carried out with the financial support of the UK Engineering and Physical Sciences Research Council (EPSRC) through the Imperial College, University of Cambridge and Open University Centre for Doctoral Training in Nuclear Energy under grant EP/L015900/1.