ML20064F069

/03L-0 on 781018:isolation Valve V-7-31 Had Damaged Rubber Seat & Drain Valve V-7-29 Obstructed by Piece of Cork & Filter F-1-58 Medium Disintegrated.Cause of V-7-31 & F-7-58 Degradations Due to Detonations in Sys

ML20064F069
Person / Time
Site:	Oyster Creek
Issue date:	11/16/1978
From:	Ross D JERSEY CENTRAL POWER & LIGHT CO.
To:
Shared Package
ML20064F067	List: ML20064F063 ML20064F069
References
LER-78-024-03L, LER-78-24-3L, NUDOCS 7811280196
Download: ML20064F069 (3)

Text

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7 8 61 ET NUVS E R 69 REPORT DATE EVENT DESCRIPTION AND PROB ABLE CONSEQUENCES h 10121 l While performing maintenance on the Off Gas System to satisfy a commit- l l o 13 ] I ment made in R.O. No. 50-219/77-21, it was discovered that isolation  !

l o 141 I valve V-7-31 had a damaged rubber seat which affected its capability to l 10151 I seal, and drain valve V-7-29 was obstructed by a piece of cork like ma- l 1016 I I terial which most_likely was in the pipe from plant const ruct ion. In I l o 17 l l addition. the absolute filter F-1-58 medium was found disintegrated. l 8F . 9 I

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35 36 31 40 41 42 43 44 47 CAusE DESCRIPTION AND CORRECTIVE ACTIONS h l i 101 l The cause of the V-7-31 and F-1-58 dearadations is attributed to the 1 li li j l detonations that occurred in the system during operation of the AuOment- l ed Off Gas System. A new seat was installed in V-7-31 and the blockage

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(201)4554200 OYSTER CREEK NUCLEAR GENERATING STATION

- Forked River, New Jersey 08731 Licensee Event Report Reportable Occurrence No. 50-219/78-24/3L-0 Report Date November 16, 1978 Occurrence Date October 18, 1978 4 .

Identification of Occurrence Degradation of the Off Gas System capability to properly isolate and filter the gaseous effluent from the plant. As a result, the radioactive off gases could not have been fully contained in the off gas piping. This event is considered to be a reportable occurrence as defined in the T-chnical Specifi-cat ions, paragraph 6.9.2.b. (4) .

Conditions Prior to Occurrence The plant was shut down for a scheduled refueling / maintenance outage.

Reactor subcritical.

Reactor mode switch locked in refuel.

All control rods fully inserted, i Source range monitors <40 cps. ,

Cavity flooded.

Reactor coolant 93*F.

Description of Occurrence During the period of October 18, 1978, through October 24, 1978, while per-forming maintenance on the Off Gas System, it was discovered that:

(1) The off gas isolation valve V-7-31 had a damaged rubber seat which affected the capability of the valve to obtain a leak tight seal.

Signs of discoloration and " wire drawing" type damage were observed.

A new seat ring was Installed in V-7-31.

(2) The off gas drain valve V-7-29 was found obstructed with a piece of cork type material which most likely was in the pipe as a result of plant construction. This obstruction prevented the full closure of I

the valve. The blockage was removed from V-7-29.

Both valves V-7-31 and V-7-29 were cleaned, lubricated, tested and reinstalled.

Jersey Central Power & Light Company rs a Member of the General Pub'. Utilit es System

1 f- s :

Reportable Occurrence No. 50-219/78-24/3L-0 Page 2 November 16, 1978 All (3) The off gas abolute filter F-1-58 medium was found disintegrated.

that remained of the filter material was a small layer of ashes in the filter housing. A new absolute filter cartridge was installed in F-1-58. .

Apparent Cause of Occurrence The cause of the V-7-31 and F-1-58 degradations are attributed to the detonations that occurred in the system as a result of the Augmented Off Gas System oper-ation. The first detonation occurred at 4:40 p.m. on August 9, 1977; the second occurred at 2:03 a.m. on March 17, 1978. The cause of the V-7-29 obstruction is attributed to maisrlal lef t in the pipe during the construction phase of the plant.

Analysis of Occurrence The safety significance of this event is considered to be minimal. Signals which would call for the automatic closure of these two valves, namely high radiation in the main steam line or high radiation in the air ejector off gas, have not been r'eceived during the time interval between the first det-onation and the discovery of damage. The quantity of off gas leaking past V-7-31, in the event of an isolation, would have been considerably less than that released during normal operations. The failure of V-7-29 to close would result in leakage of off gas into the vicinity of the 1-12 sump. An~ explosive gas monitor is installed at this sump and would instantly alarm such leakage.

Also, the atmosphere in this sump area is processed through the radwaste ventilation system, whereby, it passes through roughing and absolute filters prior to exhausting to the stack which is monitored. Stack particulate samples, which are obtained and analyzed twice weekly, Indicate that the filter damage occurred in the detonation on August 3, 1977 Although the

- subsequent stack particulate release rate increased an order of magnitude

( over that observed during normal operation, no violations of release limits resulted from the damage to F-1-58.

Corrective Action At present, modifications are being incorporated into the new Augmented Off Gas System which will include a hydraulic flane arrester.. These changes, a result of an investigation into the cause of the detonations, are hoped to be effective in precluding future malfunctions in this system.

Failure Data Previous Reportable Occurrence No. 50-219/77-21/3L, September 23, 1977, (corrective action outlined in that reportable occurrence to disassemble and repair V-7-29 and V-7-31 as appropriate.)

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