Simulation of adjuster withdrawal in Darlington Unit 4

Physics simulations in safety analyses are generally performed using a bundle irradiation distribution that is consistent with an approximate time-average configuration. In this paper, three assessments of a spurious adjuster withdrawal event at Darlington are performed with RFSP. The simulations are performed using a time-average irradiation distribution and the SORO predicted irradiation distribution just prior to the actual event. In all three of the assessments it is shown that the results are quite insensitive to the assumed irradiation distribution. This supports the approach of assuming a time-average irradiation distribution in safety analyses. (author)