Slow source convergence has long been a challenge in some loosely coupled neutronics problems, ranging from the Whitesides "criticality of the world" problem identified in 1971 to some very recent burn-up credit vbenchmark calculation comparisons under the auspices of the OECD Nuclear Energy Agency (NEA). in Monte Carlo calculations, slow convergence and statistical fluctuations can combine to produce unreliable source distributions and fission rates as well as underestimates of keff and its uncertainty. this problem is especially important when no symptoms of non-convergence are apparent to the analyst.
1 Argonne National Laboratory, USA
2 SERCO Assurance, UK
3 NAIS Co. Inc, JP
4 Japan Atomic Energy Agency, JP
5 IRSN, FR.