ML19350E538

LER 81-045/03L-0:on 810522,two Snubbers Found Inoperable on Main Steam Pipe Leading from Steam Generator 1B to 40-inch Mainfold.Caused by Loose Nut on Snubber 1-SHP-HSS-226 & Missing Stud Bolt on Snubber 1-SHP-HSS-229

ML19350E538
Person / Time
Site:	North Anna
Issue date:	06/18/1981
From:	Cartwright W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML19350E533	List: ML19350E532 ML19350E538
References
LER-81-045-03L, LER-81-45-3L, NUDOCS 8106230245
Download: ML19350E538 (2)

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LICENSEE EVENT REPORT fCONTROL BLOCK / / '/ / / / / '(1) 5(PLEASE PRINT'OR TYPE ALI, REQUIRED INFORMATION) -

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LICENSEE CODE-. LICENSE NUMBER  : LICENSE TYPE CAT 0  ; RE UR E /L/ (6) /0/5/0/0/0/3/3/8/.-(7)' ./0/5/2/2/8/1/ (8) /0/6/1/8/8/1/ (9)

REPORT DATE.

DOCKET NUMBER EVENT DATE.

' EVENT: DESCRIPTION'AND PROBABLE CONSEQUENCES (10)-

/ On May 22,'1981, with the' Unit.in Mode I two snubbers were found inoperable on- /.

/0/2/'

/0/3/ / main steam pipe 32"-SHP-58-601'which leads from Steam Generator 1B to the 40" /'

L/0/4/- J/ manifold. Snubber 1-SHP-HSS-226' had a loose nut on the connecting stud bolt and /

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, /0/5/ f/ snubber 1-SHP-HSS-229 had_the stud bolt missing from the front eye of=the-snubb- /

L-/0/6/- ~/ er. This-is contrary to T.S. 3.7.10 and reportable pursuant to T.S. 6.9.1.9.b. /-

/0/7/' L/'Since these snubbers were downstream of the Main Steam trip and Non-return /

l/0/8/: / valves, the ~ health an'd safety of the general publit- were not affected. /

SYSTEM CAUSE CAUSE COMP. VALVE CODE CODE SUBCODE ' COMPONENT CODE SUBCODE SUBCODE

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_. SEQUENTIAL OCCURRENCE = REPORT REVISION

.LER/R0 ' EVENT YEAR REPORT NO. CODE TYPE NO. ,

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_ NUMBER [8/1f, /-/ /0/4/5/ /\/ /0/3/ /L/ /-/ 'g/

.- ACTION - FUTURE EFFECT SHUTDOWN ATTACHMENT NPRD-4 PRIME COMP. COMPONENT TAKEN ACTION ON PLANT METHOD-- HOURS SUBMITTED FORM SUB. SUPPLIER MANUFACTURER-

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CAUSE DESCRIPTION AND CORRECTIVE ACTIONS (27)

/1/0/ / Tha causes of the loose nut on 1-SHP-HSS-226 and the missing stud bolt on 1-SHP- /'

'/1/1/ / HSS-229 are unknown. Within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> of discovery, the loose nut was tightened /

/1/2/ ./ and the stud bolt was replaceo. /

/1/3/ / /

/1/4/ '/ /

FACILITY METHOD.0F

-STATUS  % POWER OTHER STATUS DISCOVERY DISCOVERY DESCRIPTION (32)

/1/5/- ]E[ (28)- /1/0/0/ (29) / NA / (30) [B[ (31) / Personnel Observation /

ACTIVITY CONTENT RELEASED OF. RELEASE AMOUNT OF ACTIVITY (35) LOCATION OF RELEASE (36)-

. /1/6/.: -[Z[ (33) /Z/ (34) /' NA / / NA /,

PERSONNEL EXPOSURES NUMBER- TYPE DESCRIPTION (39)

- /1/7/ ~ /0/0/0/ (37) [Z/_ (38)' /

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PERSONNk.i INJURIES

.. . NUMBER b2SCRIPTION (41)

/1/8/- /0/0/0/-(40) / NA /

LOSS 0F OR DAMAGE '10 FACILITY TYPE d '

DESCRIPTICN 3)-

/1/5/ -[Zf[(42)~/- NA /

PUBLICITY ISSUED' -DESCRIPTION i45) NRC USE ONLY

/2/0/- /N/L(44): / NA /////////////

l NAME OF PREPARER W. R. CARTWRIGHT PHONE (703) 894-5151 8106'28'OM h

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Virginia Electric and PowerfCompany

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. North - Anna. Power Station, Unit 1

Attachment:

Page 1 of 1

-Docket:No. 50-338L .

Report No. LER 81-045/03L Description of ~ Event On May 22, 1981, with the Unit in Mode I, two snubbers were found inoperable on- Main Steam pipe 32"-SHP-58-601 which leads from Steam Generator-1B to the 40" manifold. Snubber 1-SHP-HSS-226 had a loose nut on the connecting stud bolt and snubber'l-SHP-HSS-229 had the stud bolt missing from the-front eye of the snubber. . Snubber 1-SHP-HSS-226 was-changed:from a 2 " to a 5" snubber on March 24,.1981 and 1-SHP-HSS-229 was changed from a 2k" to a 5" snubber on March 23, 1981 to comply with a recent design' change.

Probable' Consequences of Occurrence' ,

. Both snubbers are located downstream of the main steam trip and non-return valves in the Unit 1 Mechanical Equipment room. If a design basis earthquake had occurred and the steam piping had ruptured in the vicinity of these snubbers the plant and containment would be protected by the non-return valves. Hence, the' health and safety of the general public were not affected.

~ Cause of Event It is not known how the nut became loose on 1-SHP-HSS-226 between March 24, 1981 atd May 23, 1981 nor how the stud bolt was removed from 1-SKP-HSS-229 between March 23, 1981 and May 22, 1981.

Immediate Corrects.ve Action Upon discovery of the incorrect mounting of these snubbers, Emergency Maintenance Requests were submitted and the corrections were made within the same day. All snubbers in Environmental Zone 4 (Service Building) were visually inspected and no additonal problems were found. ,

Scheduled Corrective Action The next surveillance interval for Hydraulic Snubbers Accessible for Visual Inspection during Reactor Operation will not be updated to reflect the inoperability of these snubbers since the snubbers themselves were operable but not capable of performing their intended function as a i result o.' connection deficiencies. Vibration was determined not to be the cause.

Actions Taken to Prevent Reccurrence I No further action is required.

Generic Implications I

There are no generic implications associated with this event.

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