Development of a Production MCNP CANDU 3D Full-Core Model With Practical Remedies to the Issues in Deriving Reliable Tally Results

Abstract of the technical paper:
PHYSOR 2016 – Unifying Theory and Experiments in the 21st Century
May 1–5, 2016

Prepared by:
Wei Shen
Canadian Nuclear Safety Commission

J. Hu
Candu Energy

Abstract:

This paper documents the development of a production MCNP model that is equivalent to the production WIMS-AECL/DRAGON/RFSP model for a CANDU full-core problem. The MCNP simulations confirm that issues such as huge computing resource and large memory requirements, slow fission-source convergence, and fission-source correlation remain challenging in the Monte Carlo calculation of the CANDU 3D full-core problem with higher dominance ratio. These issues are more challenging for the prediction of tally results (such as channel-power and bundle-power distributions) than the prediction of the k-effective values.

To obtain a reliable MCNP full-core result, especially the power distributions, new approaches are proposed to remedy the above issues in the MCNP modelling and simulation of the CANDU 3D full-core problem.

Numerical results demonstrate that the new approaches proposed in this paper are practical in deriving reliable power distributions for the realistic CANDU 3D full-core problem from MCNP with limited computing resources. With the enhanced batch method proposed in this paper, CANDU full-core channel-power distributions are obtained from the MCNP simulations, with the relative standard deviation less than 0.3% in the central high-power region and less than 1.2% in the peripheral low-power region.

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