ML20198C208

Significant Deficiency Rept SD 414/85-11 Re Unconsidered Effects of Radiation Streaming Through Reactor Bldg Penetrations from post-LOCA Atmospheric Activity.Initially Reported on 850924

ML20198C208
Person / Time
Site:	Catawba
Issue date:	10/24/1985
From:	Tucker H DUKE POWER CO.
To:	Grace J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
References
SD-414-85-11, NUDOCS 8511120019
Download: ML20198C208 (3)

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DUKE POWER GOMPAhT r.o. nox amas CMARLOrTE, N.O. 28242 HAL B. TUCKER q, retmyseown Q * ~ "

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i Dr. J. Nelson Grace, Regional Administrator U. S. Nuclear Regulatory Commission Region II 101 Marietta Street, NW, Suite 2900 Atlanta, Georgia 30323 Re: Catawba Nuclear Station, Unit 2 Docket No. 50-414T Significant Deficiency No. 414/85-11

Dear Dr. Grace:

~Purement!to10:CFR750.55(sh. please find , attached-Significact Deficiency '

, Report.No.-414/85-11.

Very truly yours.

Hal B. Tucker l-h LTP: sib Attachment cc: Mr. Jesse L. Riley NRC Resident Inspector Carolina Environmental Study Group Catawba Nuclear Station 854 Henley Place Charlotte, North Carolina 28207 Director Office of Inspection and Enforcement U. S. Nuclear Regulatory Commission Washington, D. C. 20555 Robert Guild, Esq.

P. O. Box 12097 Charleston, South Carolina 29412 Palmetto Alliance 2135 Devine Street Columbia, South Carolina 29205 INPO Records Center Suite 1500 1100 Circle 75 Parkway Atlanta, Georgia 30339 I I

k B511120019 851024 DR ADOCK 050 4 , .g g

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DUKE POWER COMPANY CATAWBA NUCLEAR STATION Report Number: SD 414/85-11 Report Date: October 24, 1985 Facility: Catawba Nuclear Station, Unit 2 Identification of Deficiency: Unconsidered effects of radiation streaming through Reactor Building penetrations from post-LOCA atmospheric activity could result in an increased total integrated radiation dose to electrical equipment located in electrical penetration rooms as shown on Attachment No. 1. These areas were previously mild environments with a total inte-grated radiation dose of less than 1x103R. This could possibly preclude safety-related components from performing their intended safety function during the one year period following a LOCA event.

Initial Report: On September 24, 1985, Mr. Virgil Brownlee and Mr. Hugh Dance, NRC/ Region II, Atlanta, Georgia, were notified by telephone of the subject deficiency by L. M. Coggins, R. G. Eble and J. K. Ray of Duke Power Company, Charlotte, N.C. 28242.

Component and/or Supplier: Duke Power Company is responsible for the environmental radiation analysis in question.

Description of Deficiency: The previous radiation analysis assumed simple bulk shielding geometrics, i.e., a cyclindrical concrete wall of 36" thickness to represent the Reactor Building. However, cable openings in the Reactor Building wall are filled with a high density fire retardant foam of 30 lbs per cubic foot. This material does not provide the radiation attenuation equivalent to 36" of concrete. Radiation streaming from these penetrations could cause overexposure of sensitive safety equipment if the components are located in the radiation streaming path.

Analysis of Safety implications: The preliminary reanalysis was complicated by the number of penetrations and safety-related components. As a result, this problem was reported to the NRC based on coarse models of the actual problem geometries. The results of this preliminary analysis indicated that eight (8) electrical cabinets containing safety-related equipment would be overexposed during the one year post-LOCA. Subsequent analysis refined the radiation streaming model and resulted in total one year integrated doses of less than 1x10 R 4 to the equipment. Ihe refined model more accurately describes the radiation source available to stream through the penetrations. In the coarse model, source points located at the centerline of the penetrations represented large volumes of source in the containment atmosphere of which only a small fraction is available for line-of-sight streaming. The refined model describes a finer source mesh around penetrations of greatest influence on the detector locations.

The same isotopic release and resultant airborne concentrations are assumed as in the previous analysis. No decay credit is taken for transport time into the Reactor Building Annulus due to containment leakage. The

, penetrations are assumed to be filled with air. However, realistically,

! these are filled with 30 lbs/ft3 high density fire-retardant foam and varying amounts of armored cable. The values obtained in the refined r f

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analysis are below the qualified dose of all the electrical components in question. Therefore no electrical equipment qualification problems exist due to these potential radiation streaming paths.

Corrective Action: A Nuclear Station Modification has been implemented to fill these electrical penetrations with a high density material equivalent to that provided by 36" of concrete. In this way, the original normal operating and post-LOCA radiation dose of less than 1x103 R will apply for the entire area. The modification will also climinate the need to administratively control personnel access in the affected area. Ill work will be complete prior to fuel loading.

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