ML20042C099

Evaluates Proposed Design Changes Listed in NUREG/CR-1659, Vol 4 Reactor Safety Study Methodology Applications Program:Grand Gulf 1 BWR Power Plant, in Response to NRC Telcon.Design Changes to Facility Not Warranted

ML20042C099
Person / Time
Site:	Grand Gulf
Issue date:	03/25/1982
From:	Dale L MISSISSIPPI POWER & LIGHT CO.
To:	Harold Denton Office of Nuclear Reactor Regulation
References
RTR-NUREG-CR-1659 AECM-82-109, NUDOCS 8203300197
Download: ML20042C099 (4)

Text

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• MISSISSIPPI POWER & LIGHT COMPANY BeMMMME

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March 25, 1982 NUCLEAR PRooVCTioN DEPARTMENT

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Office of Nuclear Reactor Regulation Washington, D. C. 20555

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Mr. liarold R. Denton, Director Attention:

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Dear Mr. Denton:

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SUBJECT:

Grand Gulf Nuclear Station Units 1 and 2 Docket Nos. 50-416 and 50-417 File: 0260/L-860.0/16684 RSSMAP Study AECM-82/109 Mississippi Power & Light Company (MP&L) has, in response to a telephone requent from Dean llouston and Sarah Davis (NRC) to Sam Hobbs (MP&L), evaluated the " proposed design changes" listed in the last paragraph of page 6-36 of NUREC/CR-1659 Volume 4 of 4 Reactor Safety Study Methodology Applications Program: Grand Gulf #1 BWR Power Plant (RSSMAP).

These items and our comments are listed below:

ITEM COMMENT

1. Ilydrogen control devices - The Grand Gulf Nuclear Station (CGNS) design incorporates a hydrogen Ignition System (llIS) in response to NRC requests initiated in October 1980. Attachment One lists the information provided with regard to system design and evaluation of design adequacy.

2. Containnent venting - There is a containment vent path which can be used for venting. The containment isolation valves receive a permissive to open 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> after the initial isolation and can be opened by operator action from the control room.

The auxiliary building isolation valves (i.e., the filter train exhaust valves) must be electrically bypassed and can then be opened by operator action from the control room. Such venting would only be undertaken under extreme condi-tions with appropriate management consultation (in accordance with the GGNS Emergency Plan) and with due consideration given to conditions in the plant and the surrounding area.

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AECM-82/109

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MlIIZIPPI POWER O LIGHT COMPANY

3. Automatic restart of the - As discussed in FSAR Section 18.1.30.2 RCICS and LPCIS in response to TM1 concern II.K.3.13 identified as a requirement in NUREG-0737, RCIC automatic restart is being incorpo-rated into the GGNS design.

The "LPCIS automatic restart" referred to on RSSMAP page 6-36 is also a NUREG-0737 concern (II.K.3.21) and for GGNS, the relevant system is the HPCS.

According to recent discussions with Mr.

Collins of the NRC Reactor Systems Branch, HPCS automatic restart is not required for CGNS.

4. ATWS 3A Implementation - The NUREG-0460 ATWS alternates are not yet required. Current requirements are for recirculation pump trip and an ATWS procedure as discussed in the March 4, 1981 letter to MP&L from Mr. Robert Tedesco of the NRC. The recirculation pump trip for ATWS protection has been a long standing design feature of GGNS as described in FSAR Section 7.7.1.3.3.2.

The procedure for ATWS reactivity control was transmitted to the NRC on July 31, 1981 by letter AECM-81/255.

The RSSMAP study on GGNS was reviewed extensively by MP&L during its development as a draft. During this review process, extensive information was provided to the report authors informally during meetings and phone calls and formally by submission of information directly to Sandia National Laboratories.

During this period of time, MPEL repeatedly suggested areas of improvement where the approach being used in RSSMAP was conservative and unrealistic. We formally documented these concerns in letter AECM-81/184 to Dr. Robert Bernero of the NRC on July 23, 1981.

Following this correspondence, RSSMAP was published with essentially no technical changes from the drafts then existing. On September 3, 1981, in letter AECM-81/346 to Mr. Frank Rowsome of the NRC, MP&L formally documented their major concerns with RSSMAP as it was finally published in October 1981.

At this time, we believe note should be taken of the cautionary statements nade in the second paragraph of the Foreword (RSSMAP p. iii) and of RSSMAP Section 6.3.1 Conclusions and Section 6.3.2 Limitations where there is general concurrenca with many of the MP&L concerns.

In addition, the MP&L concerns were discussed extensively at the CGNS ACRS subcommittee on September 17, 1981.

During the lengthy process of reviewing and commenting on the draft version of RSSMAP, MP&L reviewed the dominant accident sequences in RSSMAP several times. We do not believe that there are simple or straightforward design modifications which would significantly reduce the risk of the RSSMAP dominant sequences. In this regard, we believe that the following items should be identified:

AECM-82/109

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1. Success criteria used in RSSMAP are generally conservative FSAR success criteria and Icad to an overestimate of core melt frequency.

2. In several areas the WASH-1400 Reactor Safety Study gave credit for

- BWR features which were not allowed in the GGNS RSSMAP study.

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3. Nevertheless, core melt frequency was estimated in RSSMAP to be similar for GCNS and the WASH-1400 BWR. ,

4. The RSSMAP core melt frequency meets currently proposed safety goals despite the conservatisms.

5. MP&L has identified sufficient areas to the NRC to require re-evalua-tion of the dominant accident sequences prior to making use of such ir'ormation for design evaluations. L Based on the above considerations, design changes to GGNS as a result of RSSMAP are not warranted.

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Yours truly.

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/ L. F. Dale Manager of Nuclear Services ,

SHH/JDR:rg ,

1 Attachment i J

cc: Mr. N. L. Stampley (w/a)

Mr. R. B. McGehee (w/a)

Mr. T. B. Conner (w/a) i Mr. G. B. Taylor (w/a)

Mr. Richard C. DeYoung, Director (w/a)

Office of Inspection & Enforcement U. S. Nuclear Regulatory Commission '

Washington, D. C. 20555  ;

r Mr. J. P. O'Reilly, Regional Administrator (w/a) '

Office of Inspection and Enforcement ,

U.S. Nuclear Regulatory Commission '

Region 11  ;

l 101 Marietta St., N.U., Suite 3100 Atlanta, Georgia 30303' P

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.I Attachment One .

GGNS. Hydrogen Control Submittals to the NRC DATE NUMBER SUBJECT .

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. March 2, 1982 AECM-82/60 liydrogen Test Program March 2, 1982 AECM-82/25 Report on " Study of 11ydrogen Control in the Grand Gulf Nuclear Station" January 21, 1982 AECM-82/32 Report on the effects of Hydrogen Detonation as the Result of a Hydrogen Generation Event.

January 19, 1982 AECM-82/26 Report on Equipment Survivability for a >

Hydrogen Generation Event January 15, 1982 AECM-82/24 Ilydrogen Control - Containment Response  !

Sensitivity Analysis ,

l December 21, 1981 AECM-81/505 Response to NRC !!ydrogen Review Questions -

discussing: HIS Surveillance Testing j i and Inspection, CLASIX-3 Input data,  ;

Actuation of Safety Systems, Ilydrogen  !

Ignitor placement and operation, and l Base Case discussion i September 11, 1981 AECM-81/353 Ilydrogen Action Items identified in AECM-81/298. Discussing: Ignitor  ;

location, operation, and design, equipment survivability, and a review  ;

of industry testing programs August 31, 1981 AECM-81/336 Hydrogen Control discussions including

Bounding analyses. for Containment  ;

l Response, base case scenario, burn l i parameters, HIS Description, HIS  :

i component qualification, Containment i Ultimate Capacity, Equipment Survivability, and Industry Testing.

4 o August 18, 1981 AECM-81/298 Hydrogen Action Status Report. l

! June 19, 1981 AECM-81/221. Description of Hydrogen Control j Measures - updated by AECM-81/336 l v

April 9, 1981 AECM-81/139 Preliminary description of Hydrogen  !

Control Measures including

.an  !

evaluation of potential Hydrogen  !

, Control concepts, preliminary design i-and evaluation, and preliminary  :

hydrogen control evaluations.  !

i i  !

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