ML19211A948

Forwards Proposal for Interim Auxiliary Bldg Secondary Containment Enclosure

ML19211A948
Person / Time
Site:	Sequoyah
Issue date:	03/29/1976
From:	Gilleland J TENNESSEE VALLEY AUTHORITY
To:	Kniel K Office of Nuclear Reactor Regulation
Shared Package
ML19211A944	List: ML19211A943 ML19211A948
References
NUDOCS 7912210356
Download: ML19211A948 (3)

Text

• ENCLOSURE 4 ORIGINAL TRAd3MITTAL ON ABSCE MAR 291976 Director of Nuclear Reactor Regulation ACT: Mr. Karl Kniel, Chief l Light-Water Reactor Branch, 2-2 '

Division of Reactor Licensing '

U.S. Nuclear Regulatory Co:::=ission Washington, DC 20555

Dear Mr. Kniel:

i In the lhtter of the } Docket Nos. 50-327 i Tennessee Valley Authority ) 50-328 '

i Enclosed for your review is TVA's proposal for an interim auxiliary building secondary containment enclosure (ABSCE) i to te used during construction of unit 2 of the Sequoyah Nuclear Plant.

Very truly yours, J. E. Gilleland i

, Assistant thcager of Power  :

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l D"': LL:G'M '

"nclosures: h l

CC: I'r. ?f. A. Siano, Project Manager TVA Projects PTR Syste=s Division Westinghouse Electric Corporation j P.O. Box 355 Pittsburgh, Pennsylvania 15230 l A. W. Crevasse, 207 PRB-C R. H. Dunhan, 505 UB-K l H. S. Fox, 716 EB-C (Attn: J. R. Calhoun) ._

G. H. Ki==ons, 607 UB-K  ;

Dr. P. A. Krenkel, 268 401B-C '

H. G. Parris, h03 FRB-C '

H. S. Sanger, 629 NSB-K \ '

P. A. S::c:epanski, 210 PRB-C k Godwin Williams, Jr., 830 PRB-C ,

G. E. Wolfe, 1003 CBB-C ,

C00EDINATED: JUil/DPP & CRM/DED -

a 7972210.356' ,.-

.1 ENCLOSURE h INTERIM AUXILIARY BUILDING SECO.'DARY COI.'TAIIC'EUT E:! CLOSURE

_Back2round The auxiliary building secondary containment enclosure (AESCE) is that portion of the auxi.11ary building which serves to maintain an effective barrier for airborne radioactive contaminants released in the auxiliary building during abnormal events. Mechanical and electrical penetrations --

of this enclosure are provided with seals to minimize infiltration; airlock-type doors are provided.at all portals. A negative pressure is maintained within the AESCE to ensure that no contaminated air is released to the en-virons follouing an abnormal event uithout first being proces, ed by an air cleanup unit, the Auxiliary Building Gas Treatment System (ADGTS). The ABSCE is outlined in FSAR figures 6.2-4 through 6.2-8.

The present construction schedule indies.tes that an eight-month interval will exist between startup of unit 1 and completion of unit 2. During this ti::e period, construction activity will continue on the unit 2 porti.on of the plant. Consequently, it cannot be assured that the AESCE boundary is complete or that all penetrations of the boundary are installed and sealed during the interim period. Thus an interim AESCE has been defined for the interval between completion of unit 1 and completion of uni.t 2. This will permit operation of uni.t 1 uhile unit 2 is still under construction by ensuring that O aa uxilt r7 butlat=c =eccaec=7 coat tu=eut c=radtlit7 ic ==t= tat"ea-

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".e' The interim AESCE is shoun as diagonally striped areas on the attached ~

drawings. The enclosure includes the fuel handling area and other areas in which significant airborne contamination =ay ' originate. The vaste Eas decay tanks and certain other ecuipment which may handle radioacti.ve gases are not included wi. thin the interim AESCE since filtration by the AEGTS would have little effect on the gases released by this equipment. Additionally, the concentration of iodices in the gases is expected to be quite lo'.i since the probability of having significant amounts of failed fuel present in unit 1 during the initial phases of operation is small.

All doors and penetrations of the interim ABSCE perimeter are provided with ceals to reduce infiltration. Doors entering the area are ci.ther locked or under administrative control during all reactor unit 1 operations .in the interim period.

Redundant isolation dampers are provided in ducts which pass from arcas inside the interim AESCE to areas outside of the enclosure. These permit isolation of the interin ABSCE and allcw the Auxiliary Building Gas Treat-ment System to maintain a negative pressure in the arca following an abnormal event.

P00RORGNIL .

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Ooeration The interim ABSCE has no effect on the normal operation of the ventilation system in the auxiliary building. The ventilation cyutem utll be balanced to maintain a slightly negative pressure uithin the interim AESCE during nomal operation. Portions of the ventilation syctem serving areac cutcide of the interim AFSCE win also be balanced to maintain a slightly negative preccure in those peripheral areas. The capability to accomplich this may be limited for short periods of time in certain peripheral arcas still under constructi.cn due to the presence of construction openings.

In' addition, redefining 'the 15C5 for the interim period has no effect on operation of the AEGTS. The AR TS =aintains a.negati.ve pressure in the interim ABSCE during emergency operation and procesces all auxi.liary building exhaust just as it would in the AESCE defined for 2-unit operation of the plant. Either train of the ABGTS may be used to maintain the negative pressure and treat air exhatt;ted frca the interim. ABSCE.

Isolation of the interim APSCE is initiated by the came signalc uhich ini.tiate isolation of the ABCCE defined for 2-unit operation. These signals are a phase A containment isolation signal, a high radiation signal from the fuel handling area radiation moniterc, or a high radiation signal from the auxiliary building exhaust vent. Any one of these signals will autonc.tically cause

. the ABGTS to begin operation and all isolatica dampers in the i.nterin ABSCE boundary to close.

O Proper actuation of the isolation dampers associated with the interim A3SCE and operation of the itEGTS uill be confined during preoperational testing of unit 1. Tects uin be similar to those planned to verify proper isolation of the AESCE defined for 2-unit operation of the plant and will verify the capability to maintain a negative prescure in the isolated area.

Recovery to 2-Unit Occration The interim ABSCE will be utilined only during the interval between ec=pletion of unit 1 and co pletion of unit 2. Prior to startup of unit 2, preoperational tests uin be conducted to verify proper isolation of the ABSCE defined for 2-unit operation and to verify the capability to maintain a negative preccure within the ABSCE. Fon owing the unit 2 preoperational tests, isolation daapers rc.ctc.lled in the . interim ABSCE boundary win be disconnected frcm their pour source and locked in the open position or removed from the duct system. Seals provided in electrical and piping penetrations of the interim boundary will remain in place. At no time in the recovery activities will the auxiliary building secondary containment capability for uni.t 1 be degraded. ,

o ?0.0R ORGINAL ..

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