Headquarters Daily Report JULY 17, 1998 *************************************************************************** REPORT NEGATIVE NO INPUT ATTACHED INPUT RECEIVED RECEIVED HEADQUARTERS û REGION I û REGION II û REGION III û REGION IV û PRIORITY ATTENTION REQUIRED MORNING REPORT - HEADQUARTERS JULY 17, 1998 MR Number: H-98-0109 NRR DAILY REPORT ITEM SIGNIFICANT EVENTS Subject: FLOODING OF ECCS PUMP ROOMS AT WNP-2 CLASSIFIED AS A SIG EVENT The NRR/AEOD/RES Events Assessment Panel on July 1, 1998, classified the flooding of the ECCS pump rooms at Washington Nuclear Power, Unit 2, (WNP-2) as a Significant Event for the Performance Indicator Program. The significant event classification was based on the loss of the fire water system which rendered redundant ECCS systems inoperable and could have caused a significant reduction in safety margins if the plant had been operating at the time of the rupture. At the time of the event, approximately 1:45 P.M. on June 17, 1998, the reactor was shut down in Mode 4 with the reactor coolant system at 133 degree F. Smoke from welding in an emergency diesel generator room initiated multiple fire alarms in the control room and also caused the opening of some pre-action valves in the fire protection system. This caused a normally dry sprinkler header to fill with water and resulted in an auto start of all 4 fire pumps. The start of the fire pumps caused a water hammer in the system which ruptured a fire protection system valve in the fire main riser in the northeast stairwell of the reactor building. The stairwell was flooded to a depth of 19 feet before the operators could secure the pumps. Water from the stairwell entered the Division II residual heat removal pump room C (RHR-C) through an open watertight door and eventually submerged the RHR-C pump motor as well as the keepfill pump for RHR-B and RHR-C. RHR-C was rendered inoperable. Water from RHR-C pump room flowed into the adjacent Division I LPCS pump room through a floor drain system valve which had failed in the open position. The room was flooded to a level 1 foot below the base of the LPCS pump motor. The keepfill pump for LPCS and RHR-A was submerged. A total of approximately 163,000 gallons of water was introduced into the stairwell and ECCS pump rooms. The licensee declared an unusual event based on the loss of RHR-C, LPCS and the normal fire suppression system. The nearby Hanford fire department dispatched engines to the site as a compensatory measure. The root cause of the flooding was determined to be an inadequate design of the fire protection system. As an immediate corrective action, the licensee pumped the water from the flooded areas and returned the fire protection system to an operable (but degraded) status by isolating the ruptured valve and returning the pre-action piping to its normal dry condition. Subsequently the licensee repaired or replaced all affected components. As an interim corrective HEADQUARTERS MORNING REPORT PAGE 2 JULY 17, 1998 MR Number: H-98-0109 (cont.) action they will keep two fire pumps running continuously to mitigate the initial depressurization associated with fire protection actuations and to prevent further water hammer events. The licensee briefed NRC management on their corrective actions at a public meeting in the Region IV offices in Arlington, Texas on July 2, 1998. The licensee committed to long term corrective actions which included reviews to determine if the flooding analysis in the FSAR is adequate and whether the floor drain valves and door seals meet design requirements. Additionally, the licensee is reviewing potential design changes for the fire protection system to eliminate the susceptibility to water hammer. The licensee restarted the unit on July 3, 1998. An NRC augmented inspection team (AIT) was onsite from June 17 to June 23, 1998. The results of the AIT were presented at a public exit meeting onsite on July 8, 1998 and will be documented in NRC Inspection Report 50-397/98-16. Preliminary Notification PNO-IV-98-026, which described this event, was issued on June 18, 1998, and updated on June 19 and again on June 23, 1998. The Events Assessments Branch presented Operating Reactors Events Briefing 98-05 on July 1, 1998, which addressed this event. An Information Notice is being prepared which will describe details of this event for the benefit of other licensees. Contacts: Jeffrey Shackelford, Region IV 817-860-8144 E-mail: jls2@nrc.gov Phillip Qualls, NRR 301-415-1849 E-mail: pmq@nrc.gov Charles Petrone, NRR 301-415-1027 E-mail: cdp@nrc.gov _