ML20151A543
| ML20151A543 | |
| Person / Time | |
|---|---|
| Site: | Yankee Rowe |
| Issue date: | 12/03/1977 |
| From: | Case E Office of Nuclear Reactor Regulation |
| To: | Groce R YANKEE ATOMIC ELECTRIC CO. |
| References | |
| NUDOCS 8011030779 | |
| Download: ML20151A543 (2) | |
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i DEC 3 ' I97I N
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Docket t. 50-29 7
Yankee Atomic Electric Company
' ATTN: Mr. Robert H. Groce 5
Licensing Engineer
,a 20 Turnpike Road i@
Westboro, Hassachusetts 01581 f:
Gentlemen:
4 9
On or about tiovember 22,1977, you should have received IE Bulletin No.
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77-06 on Containment Electrical Penetrations from the Regional Office
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of the NRC Office of Inspection and Enforcenent (copy enclosed). This F
Bulletin requests that you provide infomation on whether your Yankee-
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Rowe Plant utilim containment electrical penetrations that depend on 6
i, an epoxy sealant and a dry nitrogen environment to ensure functional
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i Due to the safety significance of this matter, the staff also conducted
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5 a telephone survey of all operating plants to obtain preliminary infor-i mation on the adequacy of qualification testing of containment electrical i
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Based on.our discussions with your staff, it was determined that additional I
documentation.(e.g., test reports, analyses) is required to establish r
the extent of environmental qualification applicable to the penetration assecblies at the Yankee-Rowe Plant.
["t Therefore, pursuant to 10 CFR 50.54(f) of the Comission's regulations, E
you are hereby requested to deliver to the Office of Huclear Reactor IL Regulation, Nuclear Regulatory Comission, Washington, D.C.
20555, not L:
later than Decerber 12, 1977, infomation which establishes the required 0
environmental qualification of the penetrations used in your facility.
THIS DOCUMENT CONTAINS I
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p Yankee Atomic Electric Company DEC 3 1977 ji le tr eI IV J
fj If you are not able to provide complete documentation of the required b
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environmental qualif! cation of all applicable connectors, you should L
f submit plans and programs for qualifying existing equipment of plans 2
for replacing unqualified penetrations with qualified equipment.
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this case, you must also include with your response a justification that continued operation of the facility, for whatever period t1 will M
take to environmentally qualify the penetrations in accordance with pl NRC regulations, would not create undue risk to the health and safety d
of the public.
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j Please advise us if you have any questions relative to this matter.
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Sincerely, i
a fj Edton G. Case, Acting Director Office of Nuclear Reactor Regulation.
Pt W
Enclosure:
g IE Bulletin lio. 77-06 j
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N Pf f!UCLEAR REGULATORY CD:' MISSION N
OFFICE F0P. IllSPECTIO:' A!!D El:FORCMENT 4
UASHINGTON, D. C.,
20555 ca November 22, 1977 d
IE Bulletin f;o. 77-06 m
A inR "0TEi:TIAL PROBLEMS WITH CON 1Ali: MENT ELECTRICAL PEllETRATI0fl. ASSEMBLIES R
Description of Circumstances:
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h.e On October 3,1977, Northeast Nuclear Energy Company reported to the Y
!!RC Region 1 Office that tuo control valves installed inside conteinmnt f
at Millstone Unit No. 2 demonstrated abnormal operational characteristics.
The licensee reported that an unexpectcd closure of a letdown flow stop valve occurred.
While investigating this prcblem, the normally closed q
safety injection recirculation return line drain valve was found to be h
in the open position.
Investigation of*t'hese events revealed the cause i
for failure to be electrical shorts between conductors within a contain-ment low voltage penetration assembly.
7 The licensee subsequently determined that the wiring for both of the d
valves shared the same low voltage module in an electrical penetration.
Electrical tests by the licensee revealed that 15 of the 85 conductors 1
in the suspect connector module exhibited decreased insulation resistance between conductors.
Based on this finding, it is believed that an clet--
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trical path between adjacent circuits in the connector module was established.
This resulted in spurious operation cf the valves.
Similar resistance checks performed on the remaining low voltage modules within the affected penetration assembly revealed 17 additional conductors with j
reduced insulhtion resistances.
All conductors with resistances less i
than 20 megohms were disconnected and their circuits were reconnected 1
through spare conductors.
Exemination of the three remaining low voltage penetration assemblies, identified 7 additional conductors with resistances of less than 20
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6 mecohms.
Each of these circuits were also reconnected through a spare
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conductor.
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Inveuiption shr!ed thal. the reduced irisulation resistar.ce r:5s prcbably M
f caused Ly rivi:ture accu n!ation within the pt:,etration asseubiv tor:.he'r L
uith small fissurcs in the epoxy seals surrounding each conduclor in iil
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the r2odule.
ihe licensae believes that moisture penetrating these cracks 4*
reduced the insulation resistance betricen adjacent conductors.
To prevent k
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further degradation from moisture buildup v!ithin the' penetration assc~blies, h
6 the licensee re-established a dry nitrogen pressure of 24 P,SIG in the ai penetrations.
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Subsequently the licensee reported that a second event of a similar p
nature occurred on October 14, 1977.
In this instance'the sanple iso-L lation valve for the pressurizer surge line failed to close on corwand.
E Investigt. tion ir.to this event indicated that Electrical shorts betrictn conductors due to a noisture accumulation probica vtas the probatle cause h
for valve miscperation.
The shorted v/ ires tiere disconnected and the valve was de-energized in the closed position.
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G In discussions on the issue viith the licensee and the electrical b
penetration vendor, General' Electric Company,,!!RC staff deternined that maintenance of nitrogen pressure is essential to the integrity of both
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high and 10.! voltEge penetration assemblies. The General Electric Company specifies in its penetration assex.bly maintenarice and operatic:
q manual that a 15 PSIG dry nitrogen pressure shotqd be raintair.cd on 10.l voltage units vthile 30 PSIG should be maintained on high voltag? units.
Action To Be Taken.By Licensees Of All Porter Reactor Facilities With Aq Operating License:
Containrcent Electrical Penetrations - For safety related systems 1.0 Do you have containment electrical penetrations that are of the T
G. E. Series 100, or are otherwise similt.r in that they dagend upon an epoxy sealent and a dry nitrocen pressure environr.ent j?.
to ensure that the electrical and pressure characteristics are raintair.cd so as to ensure the functional capability as required Y
j) by the plant's safcty analysis report; namely, (1) to ensure j
adequate functicning of electrical safety-related en,uipment and (2) to ensure containment leak tightness?
H 1.1 Have ycu experienced any electricci failures with'this t.yp2 of penetration?
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r IE Bulletin lio. 77-06 llovem.ber 22, 1977 1
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I 2.0 For thosc pcnetrations referenced in Itea 1 cbove, nave y:u paintained the manufacturer's prc{:ribed nitregcn pressure a.
4 all tines?
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k 2.1 If you have operated the penetrations a.hout maintainir.c c 4;j nitregen pressure was any degradation of insulation resistance G
h cr anomolous corponcnt operaticn detected?
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2.2 If no measurements were taken during periods when nitrogen f
pressure was not i..aintained, how were you assured that the h
A, insulation resistance was not degrcding or degraded?
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1 2.3 Hew do you deterr,ine thet circuit insulation resista>' ices values I
R are satisfactorily maintained?
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j 3.0 1s there a need, as determined by either the vendor or yourself,
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to naintain penetrations pressurized,during a LOCA?
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6 3.1 L' hat reasures have you taken to ensure that penetrations of this p.
j type v:ill perform their design function Onder LOCA conditions?
f' (design reviews, analyses or tests)
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3.2 Are the r;easures that provide this assurance adequate to satisfy a
the Coc",ission's regulations (GDC 4,' Appendix l, to Vart 50; ~M
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Criteria, Appendix B to Part 50) 4W 4.0 Provide your response to Itcms 1.0 through 3.2 above in writing within 10 '.ays.
In addition, provide an ort.1 response by 4:00 p.n.
T (Local Tina) ;;ovember 25, 19i7.
Responses shot'ld be subnitted to d
the Directpr of the appropriate l RC Regional Officc.
A copy of written responses should be forwarded to the U. S. I:uclear Regulator,"
4 i
Commission, Office of Inspection and Enforcc c,t, Division of Reactor Operatioris Inspection, L'ashington, D. C.
20:55.
Approved by G1.0, B180225 (R0072); ciecrance expir:, 7-31-80.
Aporovel.
I was given under a blanket clearance specifically for identified generic l
problcns.
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