Fission source stationarity diagnostics using the Fourier fundamental mode coefficient

Improving source convergence diagnostics sensitivity using the complex components of Fourier fundamental mode

“…Then, for each fission generation or MC cycle, the value of FFMC is tallied from the fission site, which is given by: where 𝑐 Re and 𝑐 Im are the real and imaginary components of FFMC. At each MC cycle, the values of the components are obtained by [7]:…”

“…In general, the computational cost of the FFMC method is lower than the Shannon entropy method. In terms of the number of memory allocations, the FFMC method requires two memory allocations for the two tallies 𝑐 Re and 𝑐 Im while the Shannon entropy method requires 𝐵 memory allocations according to equation ( 6) and is determined by users [7]. On the other hand, the computational time can be calculated from the exported source locations.…”

“…The feature of both indicators is that only one single scalar metric is used to represent the 𝑁-dimensional distribution quantities. The advantage of the FFMC indicator is that it is mesh-free, which reduces the user's subjectivity to the meshing scheme as required by the Shannon entropy [7].…”