ML18038A073

Submits Results of Addl Studies Re Consideration of Quantities of Standing Roof Water Due to Rainfall in Installation of Screenwell Bldg Scupper Drains Before & After 6 H PMP

ML18038A073
Person / Time
Site:	Nine Mile Point
Issue date:	10/28/1985
From:	Mangan C NIAGARA MOHAWK POWER CORP.
To:	Butler W Office of Nuclear Reactor Regulation
References
(NMP2L-0519), (NMP2L-519), NUDOCS 8511010277
Download: ML18038A073 (6)

Text

t REGULAT INFORMATION DISTRIBUTION TEM (RIDS)

ACCE'FUSION NBR;8511010277 DOC ~ DATE: 85/10/28 NOTARIZED: NO DOCKET ¹ FACIL:50-410 Nine Mile Point Nuclear S'tation~ Unit 2~ Niagara Moha 05000410 AUTH, NAME AUTHOR AFFILIATION MANGANiCeV~ Niagara Mohawk Power Corp.

RECIP ~ NAME RECIPIENT AFFILIATION BUTLERiW ~ Licensing Branch 2

SUBJECT:

Submits results of addi studies re consideration of quantities of standing roof water due to rainfall in installation of screenwell bldg scupper drains before after 6 h PMP, DISTRIBUTION CODE: B001D COPIES RECEIVEDsLTR ENCL SIZE:

TITLE: Licensing Submittal; PSAR/FSAR Amdts 8, Related Correspondence.

NOTES:

RECIPIENT COPIES RECIPIENT COPIES ID CODE/NAME LTTR ENCL ID CODE/NAME LTTR ENC NRR/DL/ADL 1 NRR LB2 BC 1 NRR LB2 LA 1 HAUGHEYiM 01 1 I INTERNALS ACRS 41 6 ADM/LFMB ELD/HDS3 1 IE FILE IE/DEPER/EPB 36 1 1 IE/DQAVT/QAB21 NRR ROEiM ~ L 1 1 NRR/DE/AEAB NRR/DE/CEB 11 i 1 NRR/DE/EHEB NRR/DE/EQB 13. 2' NRR/DE/GB 28 NRR/DE/MEB 18 NRR/DE/tlTEB 17 NRR/DE/SAB 24 1. NRR/DE/SGEB 25 NRR/DHFS/HFEB40 1 NRR/DHFS/LQB 32-NRR/DHFS/PSRB 1 NRR/DL/SSPB NRR/DSI/AEB ?6 1 NRR/DS I/ASB NRR/DSI/CPB 10 1 NRR/DSI/CSB 09 NRR/DSI/ICSB 16 1 NRR/DSI/METB 12 NRR/DSI/PSB 19 1 AB 22 NRR/DSI/RSB 23 1 REG F 04 RGN1 RM/DDAMI/MIB EXTERNAL; 24X 1 j BNL(AMDTS ONLY)

DMB/DSS (AMDTS) 1 LPDR 03 NRC PDR 02, 1 NSIC 05 PNL GRUEL"iR 1 TOTAL NUMBER OF COPIES REQUIRED: LTTR 52" ENCL

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= ~UMQHA~K NIAGARA MOHAWK POWER CORPORATION/300 ERIE BOULEVARD WEST, SYRACUSE, N.Y. 13202/TELEPHONE (315) 474-1511 October 28, 1985 (NMP2L 0519)

Dr. Walter Butler, Chief Licensing Branch No. 2 U.S. Nuclear Regulatory Commission Washington, DC 20555

Dear Dr. Butler:

Re: Nine Mile Point Uni't 2 Docket No. 50-410 This letter is a followup to Niagara Mohawk letter NMP2L-0484 transmitted on September 3, 1985 which provided information on scupper drains to be installed on the Screenwell Building. That letter stated that the maximum roof loading for other safety-related buildings was equal to 145 lbs/ft2 based on a 27 .1 inch water buildup resulting from the 6-hour Probable Maximum Precipitation (PMP) at the Unit 2 site. Subsequent to that submittal, the staff reviewer has requested consideration of additional quantities of standing roof water due to rainfall before and after the 6-hour PMP. This letter transmits the results of the additional studies.

The Screenwell Building has an asphalt roof over structural steel and has a load limit of 112 lbs/ft2. Hence there is a need for the previously described scupper drains to preclude water accumulation over 20 inches. The Reactor Building also has an asphalt roof, but it has a load limit of 145 lbs/ft2 which is equivalent to 27 inches of water . To assure the structural integrity of that roof, the following steps will be taken:

l. During the first refueling outage, sections of Reactor Building parapet on both the north and south faces wi 1.1 be removed to permit excess water accumulation to drain from the roof. Preliminary calculations indicate that a section at least 2 feet wide starting no higher than Elevation 426'approximately 19" above the roof low point) will have to be removed at both the north and south faces.

2. In order to assure safe operation during the first cycle, the existing reactor. building roof drains will be cleared of any debris at the time of fuel loading. Subsequent checks and clearings will be made in the fall of each year until the parapet modifications are completed. Since access to the roof during operation involves

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Page 2 secondary containment integrity considerations, Niagara Mohawk believes the timing and frequency of our proposed checks provide reasonable assurance of the operability of the roof drains during the winter season, while minimizing the operational impact.

It is the understanding of Niagara Mohawk that this commitment to install additional Reactor Building drainage capability, along with the previous September 3, 1985 commitment, completes all necessary y Unit 2 facility modifications necessitated by the imposition of Hydro-meteorological Reports Nos. 51 and 52.

Very truly yours, C. V. Mangan Senior Vice President JM/rl a 1041G xc: R. A. Gramm, NRC Resident Inspector Project File (2)

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