Catawba-1 rod withdrawal event and analysis with SIMULATE-3K

On March 23, 1995, Catawba unit 1 was in startup physics testing for cycle 9. During a rod-swap measurement between the reference bank shutdown bank B (SB) and shutdown bank A (SA) at hot zero power (HZP), an erroneous reactivity meter indication led to excessive withdrawal of SB. Before operator action returned the plant to the initial condition, power was measured on the ex-core detectors and the loop thermocouples. The rod motion transient with feedback was analyzed with the SIMULATE-3K code, using both best-estimate and conservative assumptions. The purposes of the analysis were to determine the calculated in-core power and reactivity response during the transient, to assess the implications of actual and postulated operator actions, and to assess the performance of SIMULATE-3K against measured data.