PNO-I-89-021, 890310,unusual Event Declared Due to Loss of Reactor Water Level Beginning on 890309.Caused When RHR Loop Pump Suction Valve a Stroked Open for Maint Testing.Level Returned to Normal Using CRD Sys Pump
| ML20236A516 | |
| Person / Time | |
|---|---|
| Site: | Vermont Yankee File:NorthStar Vermont Yankee icon.png |
| Issue date: | 03/10/1989 |
| From: | Grant G, Haverkamp D NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| To: | |
| References | |
| PNO-I-89-021, PNO-I-89-21, NUDOCS 8903170326 | |
| Download: ML20236A516 (1) | |
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DCS No:
05000271890310' Date:/
March 10, 1989 PRELIMINARY NOTIFICATION OF EVENT OR UNUSUAL OCCURRENCE--PNO-I-89-021 This preliminary notification constitutes EARLY notice of events of POSSIBLE safety or public interest significance.
The information is as initially received without verification or evaluation, and is basically all that is known by the Region I staff on this date.
Facility:
Licensee Emergency Classification:
Vermont Yankee Nuclear Power X
Notification of Unusual Event Corporation Alert Vermont Yankee Nuclear Power Station Site Area Emergency Vernon, Vermont General Emergency Docket No. 50-271 Not Applicable
Subject:
LOSS OF REACTOR VESSEL WATER LEVEL An Unusual Event was declared and immediately terminated at 12:40 a.m. on March 10, 1989 based on a slow loss of approximately six feet of reactor vessel water level that had occurred beginning about 11:15 p.m., March 9.
The reactor was in a shutdown and cooldown condition with the vessel open for a refueling outage. Vessel level was approximately 290 inches above the top of active fuel (TAF) at the start of the event and reached a low level of approximately 220 inches above TAF.
Loss of level control occurred when "A" RHR loop pump suction valves were stroked open for maintenance testing.
One of the "A" RHR loop minimum flow valves had also been released for maintenance and was found to be open. This provided a flow path from the reactor vessel to the torus, driven by static head differential pressure.
Loss of reactor vessel level was halted when the manual isolation valve for the RHR pump minimum flow valve was shut.
Level was subsequently returned to normal using the control rod drive system pump.
Reactor shutdown cooling was in operation using the "B" RHR loop.
Both core spray systems were out of service for maintenance.
The "B",RHR loop was available to pump water from the torus to the reactor if required.
I The resident inspectors are monitoring the licensee actions onsite.
The licensee has issued a press release.
i The State of Vermont has been informed.
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CONTACT: Geoffrey Grant Donald Haverkamp l
(802) 257-5319 (215) 337-5120 DISTRIBUTION:
OWFN MNCB H-St.
NL Mail: ADM:DMB l
Chairman Zech AEOD ACRS TIES D0T:Trans only Comm. Roberts ARM PDR Comm. Carr OGC NRC Ops Ctr Comm. Rogers l
Comm. Curtiss INP0----
l SECY NMSS NSAC----
l CA NRR OGC OIA Regional Offices GPA 01 RI Resident Office gg3k
'J#g k
(Reactor Licensees) l ['
Region I Form 83 g;o 317o33, posto l
(Rev. April 1988)
Pon I&E F N O - I - 8 - 0 2 1 FDC
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