Accelerated sampling of the free gas resonance elastic scattering kernel

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• 作者：Jonathan A. Walsh ; ^{walshjon@mit.edu" class="auth_mail} ; Benoit Forget ^{bforget@mit.edu" class="auth_mail} ; Kord S. Smith ^{kord@mit.edu" class="auth_mail}
• 关键词：Resonance scattering ; Doppler broadening ; Rejection sampling ; Monte Carlo ; OpenMC
• 刊名：Annals of Nuclear Energy
• 出版年：July, 2014
• 年：2014
• 卷：69
• 期：Complete
• 页码：116-124
• 全文大小：717 K

文摘

In this work, we present the derivation and investigation of a new Doppler broadening rejection sampling approach for the exact treatment of resonance elastic scattering in Monte Carlo neutron transport codes. Implemented in OpenMC, this method correctly accounts for the energy dependence of cross sections when treating the thermal motion of target nuclei in elastic scattering events. The method is verified against both stochastic and deterministic reference results in the literature for U resonance scattering. Upscatter percentages and mean scattered energies calculated with the method are shown to agree well with the reference scattering kernel results. Additionally, pin cell and full core k_eff results calculated with this implementation of the exact resonance scattering kernel are shown to be in close agreement with those in the literature. The attractiveness of the method stems from its improvement upon a computationally expensive rejection sampling procedure employed by an earlier stochastic resonance scattering treatment. With no loss in accuracy, the accelerated sampling algorithm is shown to reduce overall runtime by 3-5% relative to the Doppler broadening rejection correction method for both pin cell and full core benchmark problems. This translates to a 30-40% reduction in runtime overhead.