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The Random Ray Method Versus Multigroup Monte Carlo: The Method of Characteristics in OpenMC and SCONE

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The Random Ray Method (TRRM) is a recently developed approach to solving neutral particle transport problems based on the method of characteristics. While the method previously has been implemented only in closed-source or limited-functionality codes, this work describes its implementation in two open-source Monte Carlo codes, OpenMC and SCONE. The random ray implementations required small modifications to the existing multigroup Monte Carlo (MGMC) solvers, offering a rare venue for redundant, fine-grained, “apples-to-apples” speed and accuracy comparisons between transport methods. To this end, TRRM and MGMC solvers are evaluated against each other using each code’s native capabilities on reactor eigenvalue problems with different degrees of energy discretization. On the C5G7 benchmark (featuring only seven energy groups), TRRM achieves a maximum pin power error comparable to or lower than that of MGMC for a given runtime. On a problem with 69 energy groups, MGMC is found to scale more efficiently, obtaining a lower pin power error for a given runtime. However, the defining difference between the two transport methods is found to be their vastly different uncertainty distributions. Specifically, TRRM is found to maintain similar levels of accuracy and uncertainty throughout the simulation domain, whereas MGMC can exhibit orders of magnitude greater errors in areas of the problem that feature low neutron flux. For instance, TRRM provided up to a 373× speed advantage compared with MGMC for computing the flux in low-flux regions in the moderator surrounding the C5G7 core.



40 Engineering, 4019 Resources Engineering and Extractive Metallurgy, 7 Affordable and Clean Energy

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Nuclear Science and Engineering

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Informa UK Limited
EPSRC (EP/W037165/1)
EPSRC (EP/T022159/1)