ML20042F444

Forwards Response to Generic Ltr 89-19 Re USI A-47, Safety Implications of Control Sys in LWR Nuclear Power Plants. Plant Has Adequate Automatic Reactor Vessel Overfill Protection,Procedures & Tech Specs

ML20042F444
Person / Time
Site:	Grand Gulf
Issue date:	05/04/1990
From:	Cottle W SYSTEM ENERGY RESOURCES, INC.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
REF-GTECI-A-47, REF-GTECI-SY, RTR-NUREG-1217, RTR-NUREG-1218, TASK-A-47, TASK-OR AECM-90-0067, AECM-90-67, GL-89-19, NUDOCS 9005080330
Download: ML20042F444 (5)

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William T. Cottle May 4, 1990- Do$fI$bs U.S. Nuclear Regulatory Commission Mail Station P1-137 Washington, D.C. 20555 i

Attention: Document Control Desk 1 Gentlemen:

SUBJECT:

Grand Gulf Nuclear Station-Unit 1. i Docket No. 50-416 I License No. NPF-29 Response to Generic Letter 89-19;  ;

Request for Action Related to J

. Resolution of Unresolved Safety l Issue A-47  ;

AECM-90/0067 j

Generic Letter 89-19 requested action related to Unresolved Safety Issue (USI) A-47, " Safety. Implications of Control Systems in LWR Nuclear Power Plants."- System Energy Resources, Inc. (SERI) has reviewed the information contained in the generic letter and in the NUREG-1217 and NUREG-1218 analyses conducted for USI A-47. Our conclusions and response is provided herein, This response was originally due March 20, 1990. A 45-day extension for utilities in the BWR Owners' Group-(BWROG) was approved via a March 20,-1990 NRC letter by Mr. J. G. Partlow to the BWR Owners' Group chairman.

l- SERI has concluded that Grand Gulf Nuclear Station (GGNS) has adequate l- automatic reactor vessel overfill protection, procedures, and technical specifications to mitigate main feedwater overfeed events during power operation.

Also, operating procedures and_ operator training provide adequate assurance that the operators can mitigate reactor vessel overfill events that i

i may occur via the condensate booster pumps during reduced system pressure operation.

Supplemental information prepared by the BWROG supports the design

! adequacy of the existing GGNS overfill protection system. This information was submitted to the NRC by their letter BWROG-9048 of April 2,1990, i

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9005080330 900504 PDR P ADOCK 05000416 PDC

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'In accordance with'10CFR50.54(f), SERI is submitting this. response under.

the enclosed affirmation. If you need additiona1'information, please advise.

Yours truly,.

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WTC:mtc. .

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Attachment:

SERI Response to GL 89-19 Recommendations i'

Enclosure:

Affirmation-cc: Mr. D. C. Hintz (w/a) 1 Mr. T. H. C10ninger,(w/a)

Mr.lR. B. McGehee (v/a)

Mr. N. S. Reynolds (w/a)

Mr. H. L. Thomas (w/o)'

Mr. H. O. Christensen (w/a)

Mr. Stewart D. Ebneter (w/a)

Regional Administratar  ;

U.S. Nuclear Regulatory Commission Region II. .

101 Marietta St., N.W., Suite 2900

-Atlanta, Georgia 30323 l Mr. L. L. Kintner, Project Manager (w/a)-

l Office of Nuclear Reactor Regulation l U.S. Nuclear Regulatory Commission Mail Stop 14B20 Washington, D.C. 20555 t

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-Enclosure to AECM-90/0067. - '

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BEFORE THE UNITED STATES NUCLEAR REGULATORY COMMISSION 1

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, LICENSE NO. NPF-29 i

DOCKET NO. 50-.416 IN THE' MATTER OF L

MISSISSIPPI POWER & LIGHT COMPANY.

and SYSTEM ENERGY. RESOURCES, INC.

and SOUTH MISSISSIPPI ELECTRIC. POWER ASSOCIATION l ' AFFIRMATION l

l I, W. T. Cottle, being duly sworn, state that I am Vice President,

i. Nuclear Operations of System Energy Res'ources, Inc.; that on behalf of System Energy Resources, Inc., and South Mississippi Electric Power Association I am -

authorized by System Energy Resources, Inc. to; sign and~ file'with the Nuclear Regulatory Commission, this response to Generic Letter 89-19; that'I signed ,

this response as Vice President, Nuclear.0perati_ons~of System Energy-Resources, :nc.; and that the statements made and.the matters set forth therein are true and correct to the best of my knowledge, information and belief. ,

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-W. T. Cottle STATE OF MISSISSIPPI COUNTY OF CLAIBORNE ,

SUBSCRIBED AND SWORN TO before me, a-Notary Public, in and for the County and State above named, this k day of th ,.1990.

(SEAL)

J kch O mbng Notary'Public y ]'  ;

My commission expires:

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Attachment to AECM-90/0067

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-j SERI RESPONSE TO GENERIC LETTER 89-19 RECOMMENDATIONS GRAND GULF NUCLEAR STATION 3

-l The System Energy Resources, Inc. (SERI) response to each of the recommendations of Generic Letter (GL) 89-19, Enclosure 2 are provided below:

GL Recommendation (1)(a). Part 1 - Provide automatic reactor vessel overfill protection to mitigate main feedwater (MFW) overfeed events. .

SERI Response - GGNS currently has automatic overfill protection as part of the MFW Control System, which was approved by the NRC Staff in the GGNS SER, Appendix C pending final resolution of USI A-47. The'GGNS system includes 2-out-of-3 RPV Level 8 trip logic and three transmitters shared between vessel overfill-protection and MFW control. Each of the shared tr m mitters is on a different instrument rack, and is served by a sensor line and-a pwer supply ,

which is independent of those for the other two shared transmitters. The logic is " fail-safe", i.e., a loss of power to the overfill protection control circuit -

initiates a feedwater pump trip and a main turbine trip. This configuration is similar to the Group A plants discussed in the BWROG April 2, 1990 submittal to the NRC,-except that the GGNS transmitters are. located on separate racks.

GL-Recommendation (1)(a). Part 2 - Provide separation between the overfill protection system and the MFW control system as discussed in the GL -

Enclosure P, Paragraph (1)(a).

SERI Response - The GGNS overfill protection system does.not meet all' aspects.

of the separation criteria recommended in the GL, Enclosure 2 - paragraph (1)(a). However, potential common-mode failures (such as fire) would change the' i overfill event classification from an event of moderate frequency to an infrequent incident-or a limiting fault. Infrequent. incidents and limiting faults are not required to maintain the Minimum Critical Power Ratio (MCPR) above the_ Technical Specification safety limit MCPR.' Consequently, they are beyond the scope and intent of the UFSAR Chapter 15 transient analysis which are used to establish the operating limit'MCPR. In consideration of the NRC analysis in Nt; REG-1217 which addresses the value of upgrading an existing, commercial nonsafety-related overfill protection system with 2-out-of-3 high level trip logic, adequate protection is provided without additional system modifications. Section 4.1.1 of NUREG-1217 states, in part: " safety benefits i gained by providing_ additional reactor vessel water-level redundancy and i

independence to-some' existing feedwater systems are not significant."

l The separation of overfill protection from the MFW control system described in the GL could be implemented at GGNS only with extensive modifications. Due to the lack of any significant safety benefit, SERI has therefore determined not to I, implement this recommendation. This determination is consistent with the NRC l conclusions provided in NUREG-1217 and NUREG-1218.

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3 Attachment to AECM-90/0067 SERI RESPONSE TO GENERIC LETTER 89-19 RECOMMENDATIONS  !

GRAND GULF NUCLEAR STATION  ;

Supporting justification regarding this' position is provided in the BWROG . '

submittal to the NRC of April 2,1990. GL 89-19, the NRC analyses, and various BWR plant-specific documents (including information from GGNS) were reviewed by the BWROG to identify potential safety benefits due to the modification of existing overfill protection systems. No significant safety benefit or risk- 6 reduction was identified. Costs were then estimated for modifications required t to fully implement -the separation criteria recommended by GL 89-19. Consi stent '

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-with SERI's determination, the BWROG concluded that "the cost to make plant modifications to provide additional redundancy and independence is substantial '

and therefore modifications-are not cost beneficial."

GL Recommendation (1)(a). Part 3 - Reassess operating procedures and operator i training (and modify them if necessary) to assure operators can mitigate reactor vessel overfill events that may occur via the condensate booster pumps during reduced pressure operation of the system.

SERI Response - Reviews of the GGNS operating procedures and the GGNS training program related to the GL recommendations were conducted. . The Emergency Operating Procedures provide guidance to the operator by requiring a band for level control with both an upper and lower limits. The upper limit provides adequate assurance that the operator will reduce feed into the Reactor Pressure' '

Vessel (RPV) as required to maintain RPV level iselow the~ upper limit thus mitigating overfill concerns. Alarm Response Instructions were found to provide-proper directions to the operator in the event of " Failure of Reactor Water Level Signal", "RPV Hi/Lo Water Level", "RFPT Control Signal Failure", and "RFPT/ Main Turbine Level 8 trip". Overfill has been considered in developing simulator scenarios used for-operator training. One specific GGNS simulator scenario, which has been used for requalification training, is based upon an overfeed-related incident described in an INPO Significant Event Report. The reviews concluded that the current procedures and training program provide adequate assurance of appropriate operator actions in response to potential overfill conditions.

GL Recommendation (1)(b) - Include provisions in plant procedures and Technical Specifications to periodically verify the operability of overfill protection and ensure that automatic overfill protection to mitigate MFW overfeed events is operable during power operation.

SERI Response - A review of existing GGNS Surveillance Procedures and the Technical Specifications was performed. Specifically, Surveillance Procedures for the reactor feedwater pump turbine high level trip as required by the Technical Specifications were verified to be in place. The associated LCO was also verified. Based on this review, SERI confirmed that adequate requirements in existing procedures and the Technical Specifications (including appropriate LCOs) are present to periodically verify that the GGNS automatic overfill protection is operable during power operation.

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