TY - GEN
T1 - Hybrid technique in scale for fission source convergence applied to used nuclear fuel analysis
AU - Ibrahim, A. M.
AU - Peplow, D. E.
AU - Bekar, K. B.
AU - Celik, C.
AU - Scaglione, J. M.
AU - Ilas, D.
AU - Wagner, J. C.
PY - 2013
Y1 - 2013
N2 - For some criticality safety applications, reliably achieving convergence in the Monte Carlo eigenvalue simulations can be challenging. Inadequate source convergence typically corresponds to an underestimation of the effective neutron multiplication factor (keff) - a very troublesome possibility in the field of criticality safety. To reduce the likelihood of this possibility, a new automated source convergence sequence (Sourcerer) has been developed in SCALE to deterministically compute the fission distribution and to use it as the starting source in the Monte Carlo eigenvalue calculation. In addition to decreasing the probability of underpredicting keff due to inadequate source convergence, the sequence eliminates the guesswork associated with defining an appropriate, problem-dependent starting source. Furthermore, Sourcerer can increase the efficiency of the overall simulation by decreasing the number of generations (cycles) that must be skipped prior to keff accumulation. To evaluate its effectiveness, Sourcerer was applied to an actual used nuclear fuel canister that had previously demonstrated source convergence difficulties due to significant variation in loaded assembly burnup values and significant neutronic decoupling between assemblies. Compared to the common use of a starting source distributed uniformly in all fissionable regions, the use of Sourcerer increased the reliability of the keff calculation for all cases in which the number of skipped cycles was below ∼350; for cases with higher numbers of skipped cycles the reliability was essentially equivalent. Additionally, for a fixed uncertainty objective, the use of Sourcerer increased the efficiency of the keff calculation by 71% compared to a Monte Carlo calculation with a uniform starting source.
AB - For some criticality safety applications, reliably achieving convergence in the Monte Carlo eigenvalue simulations can be challenging. Inadequate source convergence typically corresponds to an underestimation of the effective neutron multiplication factor (keff) - a very troublesome possibility in the field of criticality safety. To reduce the likelihood of this possibility, a new automated source convergence sequence (Sourcerer) has been developed in SCALE to deterministically compute the fission distribution and to use it as the starting source in the Monte Carlo eigenvalue calculation. In addition to decreasing the probability of underpredicting keff due to inadequate source convergence, the sequence eliminates the guesswork associated with defining an appropriate, problem-dependent starting source. Furthermore, Sourcerer can increase the efficiency of the overall simulation by decreasing the number of generations (cycles) that must be skipped prior to keff accumulation. To evaluate its effectiveness, Sourcerer was applied to an actual used nuclear fuel canister that had previously demonstrated source convergence difficulties due to significant variation in loaded assembly burnup values and significant neutronic decoupling between assemblies. Compared to the common use of a starting source distributed uniformly in all fissionable regions, the use of Sourcerer increased the reliability of the keff calculation for all cases in which the number of skipped cycles was below ∼350; for cases with higher numbers of skipped cycles the reliability was essentially equivalent. Additionally, for a fixed uncertainty objective, the use of Sourcerer increased the efficiency of the keff calculation by 71% compared to a Monte Carlo calculation with a uniform starting source.
KW - Canister-specific analysis
KW - Fission source convergence
KW - Hybrid Monte Carlo/deterministic
KW - Monte Carlo eigenvalue
KW - Used nuclear fuel
UR - http://www.scopus.com/inward/record.url?scp=84902268380&partnerID=8YFLogxK
M3 - Conference contribution
AN - SCOPUS:84902268380
SN - 9781629938165
T3 - Topical Meeting Held by the ANS Nuclear Criticality Safety Division, NCSD 2013 - Criticality Safety in the Modern Era: Raising the Bar
SP - 87
EP - 98
BT - Topical Meeting Held by the ANS Nuclear Criticality Safety Division, NCSD 2013 - Criticality Safety in the Modern Era
PB - American Nuclear Society
T2 - Topical Meeting Held by the ANS Nuclear Criticality Safety Division - Criticality Safety in the Modern Era: Raising the Bar, NCSD 2013
Y2 - 29 September 2013 through 3 October 2013
ER -