Resolution of Generic Safety Issues: Item B-70: Power Grid Frequency Degradation and Effect on Primary Coolant Pumps ( NUREG-0933, Main Report with Supplements 1–34 )
Offsite power system frequency decay, depending on the rate of decay, could provide an electrical brake on the reactor coolant pump motors that could slow the pumps faster than the assumed flywheel coastdown flow rates normally used in analyzing loss of flow accidents. Item A-35, "Adequacy of Offsite Power Systems," will determine a maximum credible frequency decay rate to be used in this task. This NUREG-04713 task will determine if any additional measures are necessary to protect against a frequency decay event.
BTP ICSB-15, which addressed this issue, was deleted in Revision 2 to SRP11 Appendix 8A in July 1981. A PSB memorandum83 was issued to GIB on July 31, 1981 describing the basis for this resolution. Based on this SRP change, DSI concluded that no further action on this issue was required.378,382 Thus, this issue has been RESOLVED.