ML20040B217

Revised Final Deficiency Rept Re Concrete Voids Around Primary Containment Equipment Hatches.Addl Investigation Required for Verification of Design Calculations. Investigation Will Be Completed by 820416

ML20040B217
Person / Time
Site:	Nine Mile Point
Issue date:	01/05/1982
From:	Rhode G NIAGARA MOHAWK POWER CORP.
To:	Starostecki R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
References
10CFR-050.55E, 10CFR-50.55E, NUDOCS 8201250276
Download: ML20040B217 (2)

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. NUMOHAWK NIAGARA MOHAWK POWER CORPORATION / ' ; i P ! IC :E. Er S f rACUf. N Y 1r02/in EPHONE l3151474-1511 January 5,1982 Office of Inspection and Enforcenent .

Region I Attention: Mr. R.W. Starostecki, Director Q [b, g gk(.< g Division of Resident and Project Inspection Q;' s l U.S. Iluclear Regulatory Connission A l.. ,,

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631 Park Avenue ' l i -. ,

King of Prussia, PA 19406 Re: lline flile Point Unit 2 Docket flo. 50-410 l I

Dear fir. Starostecki:

The final report in accordance with 10 CFR 50.55(e) for voids in concrete found adjacent to the prinary contaiment equipnent hatches was submitted to your office on August 28, 1981. This report stated that a detailed verification of design calculations bad to be conpleted. The attached report indicates that additional investigation will be required. The additional investigation will be completed by April 16, 1982. If repair is dotemined to be required, your office will be notified.

Very truly yours, llIAGARA ft0LAUK P0llEP CORPORATION

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Vice President Systen Project lianagement GKR:hd Enclosure cc: Director of Inspection and Enforcenent ll.S. Nuclear Regulatory Connission Washington, D.C. 20555 8201250276 820105 PDR ADOCK 05000410 s PDR f6%T

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ilIAGARA f10 HAUK POUER CORPORATI0ll illllE IIILE POIllT Uti!T 2 DOCKET P10. 50-410 DEFICIEllCY REGARDIllG C0tlCRETE VOIDS .

AROUllD PRIfiARY C0!!TAltlftEllT EQUIPf tEllT HATCHES f r

Description of the Deficiency l The potential deficiency regarding concrete voids has been described in our l report subnitted on August 28, 1981. This report addresses an open iten in  !

the earlier report regarding the effect of the voids suspected to exist behind l the liner. A sounding nothod was used to initially find the suspect areas. i This nethod did not provide a deternination of the (epth of the voids or i uhether an actual void existed versus a slight lack of contact between the l liner and concrete surface. There are 21 regions of sounding data: 11 near  !

the hatch at azinuth 315* and 10 near the hatch at azinuth 135*. Suspect i

areas were found on the containnent vall near the hatch and on the thickened ,

portion of the wall around the hatches. The suspect areas vary in size fron i approxinately 8 to 9 inches in dianeter to an irrequiar shape of approximately i 12 by 24 inches. Also, around the top of the thickened regions, a 20-foot by i 18-inch suspect area pas found.  ?

I Analysis of Safety Inplications ,

It has been concluded that even if voids were to exist at their naxinun assuned sizes, no hazard vould exist which would endanger the public, because ,

analysis has shown that the containnent liner will not rupture. Thus the '

leaktightness function of the liner vould not be inpaired.  !

It has been deternined that a postulated 12 by 24-inch void based on the  ;

sounding data, vould be the nost critical fron a stress behavior vietpoint. l Tuo cases were investigated: one where it was assuned that the liner ctudh l were not anchored in concrete and the other where the void is assuned to be i shallow enough that the heads of the studs were encased in concrete. The results of the investigation showed that the allovable stresses would be exceeded for the case where the studs were assuned to be unanchored. For the case where the studs were assumed to be anchored, further evaluation would be  :

required to conclusively deten.11ne (1) whether the allowable stresses would be exceeded ar.d (2) the allowable depth of the postulated void if the allowable I stresses were not exceeded. In either case if the assumed void in fact exists, the liner will not rupture. The liner stresses in the 20-foot by 18-inch region of suspected void area vere deternined to be within the allouable stress limits. -

Corrective Action .

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In order to ensure that calculated stresses renain below the code allouables,  !

a further investigation will be conducted to provide a nore accurate approxination of size and depth of the suspected areas. Based on the results ,

of this investigation, the appropriate corrective action will be deternined.

This investigation will be conpleted by April 16, 1982. If it is deternined  !

that repair is required, your office will be so notified.

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