On May 4, 2011, at approximately 1325 Eastern Daylight Time (EDT), with H. B. Robinson Steam Electric Plant (HBRSEP), Unit No. 2, in Mode 1 at 100% power, it was determined that over the last 40 years, HBRSEP, Unit No. 2 periodically performed cleanup of the Refueling Water Storage Tank (
RWST) by aligning the non-seismically qualified refueling water purification system to the safety related and seismically qualified
RWST without recognizing that the action rendered the
RWST inoperable. As a result, on multiple occasions, the
RWST was inoperable for a period longer than allowed by Technical Specification (TS) Limiting Condition for Operation 3.5.4,
Emergency Core Cooling Systems Refueling Water Storage Tank.
'The cause of this event was that regulatory requirements for the separation of seismically qualified and non-qualified systems, structures, and components were not adequately incorporated into the Design Basis Document (DBD) and Updated Final Safety Analysis Report (UFSAR).
A clearance order has been placed in effect to ensure restrictions for piping that could affect the operability of the RWST remain in place.
This event was described in Licensee Event Report 2011-001-00 and was initially reported in accordance with 10 CFR 50.73(a)(2)(i)(B), any operation or condition which was prohibited by the plant's Technical Specifications. However, further reviews determined at 0800 on June 11, 2012, that the event is also reportable under 10 CFR 50.72(b)(3)(v)(D), Event or Condition that could have prevented fulfillment of a safety function.
During the three year period prior to May 4, 2011, it is estimated that the purification loop was in service aligned to the RWST while on-line nine times, totaling 297 days.
The licensee has notified the NRC Resident Inspector.
