ML19241A771

First Interim Deficiency Rept Re Lack of Design Considerations of Sum of Static,Thermal & SSE Deflections for Rigid & Variable Spring Pipe Supports.Potentially Deficient Piping Supports Reviewed

ML19241A771
Person / Time
Site:	Sequoyah
Issue date:	06/21/1979
From:	TENNESSEE VALLEY AUTHORITY
To:
Shared Package
ML19241A751	List: ML19241A749 ML19241A771
References
NUDOCS 7907090369
Download: ML19241A771 (2)

Text

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ENCLOSURE SEQUOYAH NUCLEAE v._ ANT LNITS 1 AND 2 PIPE SUPnCRT DE:.lGNERS D D .OT I'.

SUME CASES CColDEL dL SC OF DEFLECTIuS5

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Descr:ption of Deficinncy The cesign of sc e rigid and some variable spring pire supports a:

Sequoyal Nuclear Plant did not consider tne sum of static, thernal, a .1; safe shutdown earthquake (SSE) deflections. In most of these caseo, :ne designers sclected tne largest of the 'hree deflectient mentionec a::ve.

• e; gners centributing to thi> de: :ciency are both at TVA and a: Ea3 :

Eno:ncera in Pittsourgh, PA (a div.sion of Dravo), wna performed sote ;;;e nan 3 er aesign work cn contract from TVA.

sai.2caen deflection during an Sri not i;gured in;s t s. e ces.g .m..

rt,vli ir. e::ner insufficient clearance available to prevent contact be:-cen the pipe and its support or the available deflection ci variarle sprano suppor:s being insufficient :o prevent over-extension. Once ecn-tac *. Dc: ween pipe and support or over-extension of a spring pipe suppcr:

occura, a hign stress point results which could possibly lead to over-3;ressing of the piping and/or the affected support.

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sert ei the pipes supported by celecteve supper:s are safetv-relatua.

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. we;.clene. was cascovered by m.. A engineers investigcting anc::.or

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.u us . ;v.))te) 1:ea (S _.un Cc.s ,9-17/ ,ea.,ing < . wit.n covencn c: :ne stee.

c o n t a irm.u n t vessel (SCV) following a design basis acciden: inside cen-ta.naen anc resulting effects on piping wnich penetrates :ne S C'. ' 's A sa.11-era :nis deficiency to be recortable because of :ne poss;b. 2: ic:

n ;;;n stress areas and possible subsequent failure due to overstress.n;

n saiet;.-rclated piping and supports during an SSL event.

L.e cause of this deficiency is the fal;ure of sote engineers at I'.' A anc at basie Engineers to follow a design criteria document which spec;;;es that deflec: ions due to thermal, dead weight, and S3E be succed in designing pipe supports.

Safet :rnlic.it ion s

.. t...a oe: . c . e n ;. had remained uncorretteJ. an e di. evi n: Jur; . ,.e operat.va 13 nt have leu to overstres31a nw; n subw que: : :a;.urs : r- .- .-

so: 4 ~ tty-relattd piping anJ sup ort, ( e . >; er ane Au.u 11a r . r e e ,. . a : <r As auch, the possible over s t ress Ani; wit h suomegaent tallure n sa: u. -re.a:eu p;p a r.s arid suppor t s ::ght nave i= paired ne ab;1;;v of the p; ant t. r<a.

a sJ1e andtdOwn Condition.

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Corrective Act:ons

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The ap p r c >. ama t e ly 330] potent;all- ce: 2c;en: ,; rang suppor: 3 ha.e retr rev;t-ed and checked to verify correctne w a: tne Jesign. As a r t :. . . . af

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. .13 design revtes, . hangers . .u s e- beta 1:entified as requiring ma;.;;a-

• on, e2ther ~.a hari.are or in sett'ng

  ne spring on variable sprir.g-: pe suppor: 2.

Pipe supports at other TVA nuclear plants are presen:1j bein; investi;;sted to ensare tha: this deficiency does not exist at those planta.

1eans laken To Prevent Recurrence Ta la , resenti. Investiga:Ing :.. teans tha: s;11 be taken to pre.tr:

<mm=eme ,: :nis y, cet1:1 enc :he,e me_,m,e s ..... ; ce.a1.e; ., ,

blUsequer: repor on this defiClenC)

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