PNO-II-93-018, on 930424,manual Reactor Tripped Due to Oscillations & Water Hammer in Feedwater Sys.There Were No Feedwater Sys Ruptures or Leaks,No Injuries to Personnel & No Releases of Radioactivity in Excess of NRC Requirements
| ML20036A198 | |
| Person / Time | |
|---|---|
| Site: | North Anna  |
| Issue date: | 04/26/1993 |
| From: | Sinkule M NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| To: | |
| References | |
| PNO-II-93-018, PNO-II-93-18, NUDOCS 9305100200 | |
| Download: ML20036A198 (3) | |
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.. __ - - April 26, 1993 PRELIMINARY NOTIFICATION OF synnT OR UNUSUAL OCCURRENCE PNO-II-93-018 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 II staff on this date.
i Facility Licensee Emercancy Classification Virginia Power Co.
Notification of Unusual Event North Anna 2 Alert Richmond, Virginia Site Area Emergency i
Dockets: 50-339 General Emergency l
X Not Applicable l
1
Subject:
MANUAL REACTOR TRIP DUE TO OSCILLATIONS AND WATER HAMMER IN FEEDWATER SYSTEM j
On April 24, 1993, at 5:30 a.
m.,
North Anna Unit 2 was manually tripped 4
when operators observed oscillations of the C Main Feedwater regulating valve and flow in the C and B main feedwater. A rupture of the main
)
feedwater piping was suspected. After the manual reactor trip, the main feedwater and condensate systems were isolated and the reactor was cooled i
down using the auxiliary feedwater system and the atmospheric relief valves on the steam system. All reactor safety systems functioned as designed. The licensee declared an ALERT at 6:02 a.m. on 4/24/93. The ALERT was downgraded to an NOUE at 8:16 a.m. on 4/24/93. The NOUE was terminated at 10:45 on 4/24/93. There were no.feedwater system ruptures or leaks, there were no injuries to personnel and no releases of t
radioactivity in excess of NRC requirements.
i The NRC entered the monitoring mode with Region II's Incident Response Center (IRC) being activated at 7:50 a.m. on 4/24/93. The IRC was deactivated the same day at 11:30 a.m.
In addition to the two resident
. inspectors on site, two region based inspectors and Region II's Section Chief for Virginia Power Plants were dispatched to the site.
The initial damage assessment conducted by the licensee and confirmed by the NRC inspectors on site indicates that no damage has occurred to the feedwater piping. Snubber damage and a broken yoke was observed on the regulating valve in the six-inch-by-pass line for the C main'feedwater valve. Insulation damage was also evident on main feedwater piping.
The licensee is conducting a damage assessment and a root cause analysis of the event. The licensee thought the oscillation and water hammer incident could have been caused by a severed feedwater ring in the C steam generator, however, an inspection of the feedwater ring and its
'J' tubes showed it to be intact. The licensee is still in the process of doing further inspections and analysis.
The State of Virginia was informed and news release were issued by the NRC and the Licensee.
9305100200 930426 PDR I&E
[f9 PNO-II-93-018 PDR
l The IRC received initial notification of this event by telephone from the licensee at 6:13 a.m. on 4/24/93.
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I PNO-II-93-018 2-This information is current as of 4:15 p.m. on 4/26/93.
Contact:
Marvin Sinkule (404)331-5506 l
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