A finding of very low safety significance (Green) and associated violation of 10 CFR, Part 50, Appendix B, Criterion III, Design Control was identified by the licensee for the failure to ensure the
ECCS mode of operation of
RHR would be capable of performing its mitigating function in mode 3 following
RHR realignment from its
shutdown cooling mode of operation. Specifically, the operability requirements of
RHR in mode 3, as defined by
TS 3.5.1, were not translated into applicable procedures or specifications of the system in that neither the procedures nor the design prevented the condition that would
lead to steam void formation during a loss of coolant accident that initiates at this mode resulting in steam binding of the systems pumps and/or an adverse
water hammer. The performance deficiency was determined to be more than minor because it was associated with the
Mitigating Systems Cornerstone attribute of equipment performance and affected the cornerstone objective of ensuring the capability of systems that respond to
initiating events to prevent undesirable consequences. A Phase II
SDP was conducted using
IMC 0609, Appendix G. The finding screened as very low safety significance. The licensee entered this concern into its corrective action program as CARD 12-24503 and initiated a Condition Evaluation for
TS 3.5.1 ECCS Operating may be non-conservative. In the interim, the licensee has implemented actions to declare the division of
RHR inoperable when used in the
shutdown cooling mode of operation in mode 3. The safety function is maintained by the other division of
RHR. The licensee plans to evaluate the
BWR Owners Group analysis of the postulated mode 3 loss of coolant accident scenario and implement permanent procedural, design, and/or licensing basis changes as necessary.
