ML20206G486

SER Supporting Employee Concern Element Rept EN 232.9(B), Freezing of Condensate Lines

ML20206G486
Person / Time
Site:	Sequoyah
Issue date:	11/04/1988
From:	NRC OFFICE OF SPECIAL PROJECTS
To:
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References
NUDOCS 8811220296
Download: ML20206G486 (2)

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%, n. s ;r SAFETY EVALUAT10'; oEo0RT PV THE OFFICE OF SPECIAL PC0JECTS EMPLOYEE CONCERN ELEMENT REPORT EN 232.9(G?

FREEZlhG OF CONDEN! ATE LINES TELLESSEE VALLEY AUTHORITY ,

i SECUrvAu NUCLEAR POWER PLANT, llNITS 1 AND 2  !

l 00CKET NOS. 50 327 AND 50-328 1.0 INTCCDUCTION .

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This ccncern was raised at Watts Bar Nuclear Plant ir. regard to free:ing ef the concensate drair Idres which ccrnect to the air handling unit (AHU) drip pans resultirg ir ciegging of the aHUs with frost buildue, in the corcern it was balieved that this resultad fren proxirity of tha s.O glycol supply linas to the ccedersate drain lines. This concern was considered potentially applicatie to SCN because cf the sir.ilari yt nf tra VEN and SCN ica condansar design.

2.0 EVALUAT!0" l i

Catecery: Engineering '

Subcatagory: Pipirg and Valve Design E1erent: Free 2 ire of Condensate Lines Erployee (cncern: IN-E5-7?2-005 The basis for Elerart Depert EN 232.9(B) - SON Rev. O dated Decerber 30, ISS6, it Secuoyah Employee Cercern IN 85-772-005 which states: "Condensate line and plycol lira running ncyt to each cther is not a Gcod design. Air handlers in July /Auscst 1984 were filled with ice, causir.g icing cf draine, and clogging.

Lccatter: Ira Cordensars (32 air handlers) locatec at the Head ? circular stairway up from elevatirn 755'-0" in Reacter Buildine bott units."

The TVA evaluetion program for this cercern included:

(a) a review of the gareral arrargerent drawing for locat on i and operating ervironrent ef ice conder.cer AHU's at both WBS a-d SCN, It} a review of tys+en firw diagrans and FSAR text te determire systet furctional requirersets and design parareters at both WEN act SQN,

! (c) e revie. of Nuc' ear Dawa" F*carience reperts en ice concenser AHU icdre ce:rk s et i.'. v c et*** ice cercense" p'er*e 'ce gereric prer'r-t.

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• F. 3 e . c ' ; ; ; ' r. ; ce!v.gs ice chysic.Al p*0'dr'ty of AHU crains ard l glycol ;1 ping a t SC'..

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' (e) a comparison of the results of the non-restart justification report with this evaluation in regard to the employee concern to the SQN, and l i

(f) an eveluation of the specifics and generic implicatiens of the cencern as (

i tFey relate to SCN.

Exanination of the SCN drawings shows that in the AHU area, all of tht glycol  ;

lines are above the AHUs and all the ccedensate crains are below the AHUs with the mininur distance between glycol and drain piping being rore than 6 feet.

Hence, fren a review of the SON drawing, TVA concluded that freezing of the condensate drain lines as a result of proximity of the cold glycol lines is not  ;

a credible event.

A review of the event reports in Nuclear Power Experience indicated recurrent problems with AHU condensate drains. Examples cited by TVA included 4 everts

' at Sequoyah and one at Donald C. Cock. TVA concluded that all of these events ,

could have bear caused by heat tracing failures. Each AHU drair has an 4

indivicual loo; seal ir:ediately below the flanged drain connection to the AHU.

loss of heat tracing, ever 'or short periods of tire is likely to result in freazing at the loep seal. l TVA also deternired that portions of the cendensate drain line insulation was ,

j either nissing or severely degraded at SON.

i TVA has propoW to corecct the problen by adding irt ulation behind vent l curtains and rr the racial beams in tha upper bay. S.is is expected to greatly i

reduce the condensatien which certributes to ice bui' dup by reducing the supply i n' warn roist air. In eddition TVA has a surveillarce instruction which i J reouires weekly inspection for ice buildup. Any ice buildup found is recoved, i

i 3.0 CONCLL'S!0N ,

The conce m that condensate drain lires can freeze ar.d cause clogging of the

Ahu's is valic as observed at Sequoyah and Conalo C. Cook. However, the l proxinity ef cold glycol lines to condensate drain lines is not likely to cause i this freezing because of the separation distance of ever 6 feet. TVA's i preprsed fix consisting of capping off of the moist rir inflow anc repa; ring l 4 the insulation on the drain lines should reduce ice Nildup. The surveillance l 1

instruction assures that ary ice buildup that does occur will be identified and i i reroved without affecting plart sa'ety.  !

The MC staf' cercludes tr,at TVA's investigatien and resolution of the concerns described in Eierent Repert EN .32.9(B}

1 were adequate. No further NRC review i is requirec.

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