Limited linear source approximation with edge detection for convergence stability of method of characteristics

ABSTRACT

A new implementation of the limited linear source approximation (LLSA) is proposed. The LLSA was previously proposed to eliminate local negative source in flux regions to mitigate numerical instability of the method of characteristics (MOC) with linear source approximation (LSA). In the present LLSA implementation, the convex edges of flux regions are used to check the local negative source to decrease the computational load. The present method is implemented in the transport code GENESIS, and its effectiveness is verified through the two dimensional C5G7 benchmark problem and the simplified two-dimensional high-temperature engineering test reactor core. The calculation results indicate that the present LLSA implementation efficiently mitigates the numerical instability of MOC with LSA. Additional computational time is less than 1% of total computation time.

KEYWORDS:

• Numerical instability
• MOC
• limited linear source approximation
• negative-flux zero fix up
• high-temperature gas-cooled reactor

Acknowledgments

The authors are sincerely thanks to Dr. S. Choi and Prof. B. Kochunas of University of Michigan for the discussion on the implementation of LLSA in the MPACT code.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

The author(s) reported there is no funding associated with the work featured in this article.