ML20148T139
| ML20148T139 | |
| Person / Time | |
|---|---|
| Site: | Oyster Creek |
| Issue date: | 04/25/1974 |
| From: | Manning J JERSEY CENTRAL POWER & LIGHT CO. |
| To: | |
| References | |
| NUDOCS 8102190783 | |
| Download: ML20148T139 (3) | |
Text
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CY6. 3R CPIEX NUCLEAR GENERATING ST,-.
ON
. J FORKED. RIVER, NEW JERSEY 08731'
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. 5 IDENTIFICATION.
. Cracking of torus to drywell vacuum breaker valve V-26-2 disc.
OP OCCURRENCE:
'Ihis failure completely:
'at junction of disc body and stem, separated the stem from the disc body and would'have rendered
, the vacuum breaker valve inoporative had it occurred-under no2ual.. operating conditions. -
'Ihis ovent is considered to be an abnormal occurrence as de-fined in.the Technical Specifications', paragraph 1.15D.
.t CONDITIONS PRIOR
_ Steady State Power Routine Shutdown TO OCCURRENCE:
Hot Standby Operation Cold Shutdown Load Changes During X
Refueling Shutdown Routine Pa.ter Operation Routine Startup-Other (Specify)
P
. Operation The reactor modo switch was in the REFUEL pos5 tion and reactor coolant ter.perature was approximately' 103 F..
c DESCRIPTION At approximately 1100 on April 24, 1974, while contractor OF OCCURRENCE:-
i personnel were disascorbling torus to drywell vacuum breaker valve V-26-2 for inspection and maintenance work', the valvo disc cracked at the junction of the disc body and stem.
Th o.
disc body and stem are made of cast aluminum and cast as one-j
. piece.
'Ihis failure co:pletely separated the st' m from the e
j dis c. body. At the time of the failure, the contractor
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punormel were tapping the' associated disc nut in an effort t
to fico and ultirately remove the nut from the dihc stcc.
Ris; tapping was also used to free disc nuts on nine. pro-ylously 'discssechled torus to drywell vacuum breaker valves.
i APPAREhT CAUSE-Design t
1 Procedure OP OCCURRENCE
Manufacture Unusual Service Condition
~ Installation / -
Inc. Environmentcl Construction-Component Failure Operator
_ Other (Specify) i 4
" Initial visual exaninaticin of the crack surfaces revealed that
,most of this area was cican, flowever, some darkened (dirty) areas woro observed around the edges of the crack surfaces.
his would indicate that the cracking started sor.etime before the coglete disc failure on April 24, 1974. 1hc apparent.
cause cf this occurrence is under investigation at this time.
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ANALYSIS OF-Ris valve disc failure is considered to have minical safety OCCUTENCE:
significance. Although the valvo (V-26-2) would have been rendered inoperative had the failure occurred under normal operating conditions, the applicable requirements for torus to drywell vacuum breaker valve operability specified in paragraph 3.5. A.3 of the Technical Specifications would have been satisfied. Ilowever, the drywell-torus vacuum breaker valves are also r5 uiriid~to Ue closed:during pipe break acci-1 dents (particularly small breaks) to assure proper stoam condensation and prevent torus overpressure. The safety significance of this event is that valvo V-26-2 might not have perfomed thi-function had the disc failure occurred
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v dur.. ; norcal operating conditions a the disc been'.subse-e quently repaved from its seat (by. torus overprassure, weekly i
operebility testing, etc.).
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CORRECTIVE.'.'
.'%e discs of the other thirteen torus to drywell vacuum 1.
i ACTION:
breakar valves will-be inspected for cracking in the area i
of the disc body-stem junction.
Additional itens of cor-rective action will be determined follwing review of this l
i incident 'by the Plant Operations Review Cocnittee.
FAILURB DATA:
. Basic yalvo data are as follows:
s...
c Manufacturor: Atwood.6 Morrill
. I 9.d Typa: Check Valvo
' 4;.
Disc Material: Cast Aluminura Vent Area:
1.75 square foot per valve
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Prepared by.
-_- b b, Date:
'4 /25/74.' '
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