Abstract
The combined fission matrix theory is a recently-developed hybrid neutron transport method. It features high efficiency, fidelity, and resolution whole-core transport calculation. The theory is based on the assumption that the fission matrix element ai,j is dominated by the property of the destination cell i. This assumption can be well explained in thermal reactors, and the combined fission matrix method has been validated in a series of thermal neutron system benchmarks. This work examines the feasibility of the combined fission matrix theory in fast reactors. The European Sodium Fast Reactor is used as the numerical benchmark. Compared to the Monte Carlo method, the combined fission matrix theory reports a 64 pcm keff difference and 8.3% 2D RMS error. The error is much larger than that in thermal reactors, and the correction ratio cannot significantly reduce the material discontinuity error in fast reactors. Overall, the combined fission matrix theory is more suited for thermal reactor transport calculations. Its application in fast reactors needs further developments.
Highlights
The high-fidelity neutron transport method is a key technique in reactor design and safety analysis
This paper examines its application in fast reactors
The mechanism of combining database fission matrices by the destination cell property is more suited for a thermal neutron system
Summary
The high-fidelity neutron transport method is a key technique in reactor design and safety analysis. There have been many such methods developed, including the deterministic MOC (Liu et al, 2011) method; the VNM method (Zhang et al, 2013, 2018); and the stochastic Monte Carlo method Other than these traditional methods, the hybrid neutron transport method is gaining popularity in recent years. It pre-calculates a series of response functions and solves for the neutron transport deterministically relying on response functions. Such methods feature the combination of high accuracy from the Monte Carlo method and the high efficiency from the deterministic method. The fission matrix from the neutron transport eigenmode equation can be written as: Fi
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