PNO-III-87-066, on 870509,during Process of Heating Up Unit Following Refueling Outage,Water Hammer Damaged Main Steam Line 1B Outside Containment.Cause Unknown.Msivs & Bypass Valves Taken Out of Svc & Repairs Started

PNO-III-87-066:on 870509,during Process of Heating Up Unit Following Refueling Outage,Water Hammer Damaged Main Steam Line 1B Outside Containment.Cause Unknown.Msivs & Bypass Valves Taken Out of Svc & Repairs Started

ML20213G834
Person / Time
Site:	Byron
Issue date:	05/11/1987
From:	Forney W, Warnick R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
To:
References
PNO-III-87-066, PNO-III-87-66, NUDOCS 8705180476
Download: ML20213G834 (1)

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Dme PRELIMINARY NOTIFICATION OF EVENT OR UNUSUAL OCCURRENCE--PNO-III-87-66 Data May 11, 1987-

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This preliminary n:tification constitut:s EARLY. notice of ev:nts of POSSIBLE safety cr public interest significance. The information is as initially received without [

v3rification or evaluation, and is basically all that is known by the Region III

. staff cn this date.

Facility: Commonwealth Edison Company Licensee Emergency Classification:

Byron Unit 1 Notification of an Unusual Event Byron, IL 61010 Alert Site Area Emergency Docket No. 50-454 General Emergency X Not Applicable

Subject:

WATER HAMMER IN MAIN STEAM LINE The licensee was in the process of heating up the unit following a refueling outage when a water hamer damaged the IB Main Steam Line outside containment.

Damage included six broken pipe supports (embed plates pulled out of the ceiling) and two broken snubbers (shock absorbers). The snubbers are on the IC Main Steam Line. It is assumed that they were damaged when the 18 steam line fell on them. Approximately 300 feet of ths 1B steam line was affected by the water hamer.

The licensee does not know exactly when the water hamer occurred, but believes it happened after personnel began warming the main steam lines about 3 a.m. (CDT), May 9,1987. The

unit was at 340 degrees F. Operators warmed the lines using the Main Steam Isolation Yalve bypass valves, with steam generator pressures at approximately 50 psig.

The MSIVs and bypass valves have now been taken out of service and the unit is presently in l h:t standby.

' Walkdowns of the IA, 1C and ID main steam lines have been completed. No structural damage was discovered, though some minor hanger repairs will be completed. The licensee will perform nondestructive testing on all IB steam line welds.

The licensee estimates the repairs will add about one week to the present refueling outage.

Region III (Chicago) and the resident inspectors will monitor the licensee's course of action.

The State of Illinois will not be notified.

The resident inspector was first informed of this event at 8:30 a.m. (CDT), May 9,1987. This information is current as of 11 a.m. (CDT), May 11, 1987.

CONTACT: W orney (FTS 388-5590) pR. arnick(FTS 388-5575)

DISTRIBUTION:

H. St. ED0 NRR E/W Willste Mail: ADM:DMB Chairman Zech PA IE NMSS DOT:Trans only Com. Roberts ELD OIA RES Com. Asselstine AEOD NRC Ops Ctr 3. %

Com. Bernthal Com. Carr SP 2!$D Regional Offices ACRS SECY INPO $ 5 4 NSAC3,'06 CA RIII Resid nt Office PDR Licensee: 3'. / 7 (Corp. Office - Reactor Lic. Only) g51so476870511 I&E

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p O-III-87-066 PDR Region III Ol Rev. November 1986 7 Y