ML20244C552

Responds to Station Blackout Rule 10CFR50.63.Review of Existing Battery Capacity Calculations Verifies That Batteries Have Sufficient Capacity to Meet Station Blackout Loads for 1 H

ML20244C552
Person / Time
Site:	Yankee Rowe
Issue date:	04/13/1989
From:	Drawbridge B YANKEE ATOMIC ELECTRIC CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
RTR-REGGD-01.155, RTR-REGGD-1.155 BYR-89-70, NUDOCS 8904200269
Download: ML20244C552 (6)

Text

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YANKEEATOMICELECTRIC COMPANY 'fy"yo* g*]o','o";*g'"

g 580 Main Street, Bolton, Massachusetts 01740-1398 m.

April 13, 1989 BYR 89-70 Un'ited States Nuclear Regulatory Commission Document Control Desk

' Washington, DC 20555

References:

(a) " License No. DPR-3 (Docket No. 50-29)

(b) 10CFR50.63, " Loss of All Alternating Current Power"

Subject:

Response to Station Blackout Rule 10CFR50.63

Dear Sir:

On July 21, 1988, the Nuclear Regulatory Commission (NRC) amended its regulations in 10CFR, Part 50. A new section, 50.63, was added which requires that each light water-cooled nuclear power plant be able to withstand and recover from a Station Blackout (SBO) of a specified duration. Utilities are expected to have the base line assumptions, analyses, and related information used in their coping evaluation available for NRC review. It also identifies the factors that must be considered in specifying the SB0 duration.

Section'50.63 requires that, for the SB0 duration, the plant be capable of maintaining core cooling and appropriate containment integrity. Section 50.63 further requires that each licensee submit the following information:

1.- A proposed SB0 duration, including a justification for the selection based on the redundancy and reliability of the on-site emergency ac power sources, the expected frequency of loss of of f-site power, and the probable time needed to restore off-site power;

2. A description of the procedures that will be implersented for SB0 events for the duration (as determined in Item 1 abave) and for recovery therefrom; and

3. A list and proposed schedule for any needed modifications to equipment and associated procedures necessary for the specified SB0 duration.

The NRC has issued Regulatory Guide 1.155, " Station Blackout," which ~

describes a means acceptable to the NRC staff for meeting the requirements for 10CFR50.63. Regulatory Guide 1.155 states that the NRC staff has determined that NUMARC 87-00, " Guidelines and Technical Bases for NUMARC Initiatives MT l gr2ggggggg, i 1 j

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United States Nuclear Regulatory Commission- April 13,.1989 Attention: Document Control Desk Page 2 BYR 89-70 Addressing ~ Station Blackout at' Light Water Reactors," also provides guidance that is, in large part, identical to the Regulatory. Guide 1.155_ guidance and-is acceptable to the NRC staff for meeting these requirements.

Table:1 to Regulatory Guide 1.155 provides a. cross-reference'between Regulatory Guide 1.155 and NUMARC 87-00 and notes where the regulatory guide takes precedence.

Yankee has evaluated the-Yankee Nuclear Pcwer Station (YNPS) against'the requirements of the SB0 rule using guidance from NUMARC 87-00 except where Regulatory Guide 1.155 takes precedence. The results of this evaluation are detailed below. (Applicable NUMARC 87-00 sections are shown..in parenthesis.)

A. Proposed Station Blackout Duration NUMARC 87-00, Section 3, was.used to determine a proposed SB0 duration of four hours.

The following plant factors were identified in determining the proposed SB0 duration:

1. The ac power design characteristic group is P2 based on:

a. Expected frequency of grid-related Loss of Off-Site Power (LOOP) - does not exceed once per 20 years (Section 3.2.1, Part 1A.,Page 3-3);

b. Estimated frequency of LOOP due to extremely severe .k weather places the plant in ESW Group 1 (Section 3.2.1, Part 1B, Page 3-4);

c. Estimated frequency of LOOPS due to severe weather places the plant in SW Group 3 (Section 3.2.1, Part IC, Page 3-7):

d. The Off-Site Power Syster is in the II/2 group (Section 3.2.1, Part 1D, Page 3-10).

2. The emergency ac power configuration group is C, based on the following (Section 3.2.2, Part 2C, Page 3-13):

a. There are two emergency ac power supplies not credited as alternate ac power sources (Section 3.2.2, Part 2A, Page 3-15);

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b. One emergency ac power supply is necessary to operate safe shutdown equipment following a LOOP (Section 3.2.2, Part 2B, Page 3-15).

3. The target Emergency Diesel Generator (EDG) reliability is .975.

a. A target EDG reliability of .975 was selected based on Items 1, ii, and lii below, consistent with NUMARC 87-00, Section 3.2.4:

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, United States Nuclear Regulatory Commission Aprili13, 1989 Attention: Document ~ Control Desk' Page 3-g.a BYR 89-70 n l1. Having a nuclear unit average EDG' reliability for the -;

last 20 demands greater than 0.90;

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ii. Having a nuclear unit average EDG reliability for the

=last 50 demands' greater than 0.94; iii. Having a nuclear' unit average EDG' reliability.for the

'last 100 demands greater than 0.945.

4. An Alternate.AC (AAC) power source will be utilized at YNPS which meets the' criteria specified in Appendix B to NUMARC y 87-00. The 1.30 source is an EAC power. source which meets the assumptions in Section 2.3.1 of NUMARC 87-00.'

The AAC power source is available within one hour of the onset of.the,SB0' event, and has sufficient capacity and capability to operate systems necessary~for coping with a'SB0 for.the required SB0 duration of four hours to bring and maintain the plant in safe. shutdown. An ac independent coping ~ analysis was

. performed for.the one hour required to bring the AAC power

" source on-line.

AAC

Description:

YNPS utilizes one'of three installed 400 kW Emergency Diesel Generators as an alternate ac source.. Each-

, unit supplies'a. separate 480 volt emergency bus which can be aligned through electrical switching, both inside and'outside.

l the Control Room to power all required. safe shutdown loads in less than'one. hour. (Refer to the enclosed simplified one-line diagram of the YNPS Electric Power System).

B.. -Procedure Description j B.1 Plant procedures have been reviewed and modified as required to meet the guidelines in NUMARC 87-00,~Section 4, in the following areas: j i

a. AC power restoration per NUMARC 87-1 Section 4.2.2. l

b. Severe weather per NUMARC 87-00, Section 4.2.3.  !

B.2 Plant procedures have been reviewed and changes necessary to meet SB0 response per NUMARC 87-00, Section 4.2.1 will be implemented by July 1, 1989.

C. Proposed Modifications and Schedules There are no plant modifications required to utilize the AAC power source. As noted in Item B2 above, procedure modifications will be  ;

made to address the use of a single EDG to provide power to all required safe shutdown equipment for the required four-hour coping

' duration.

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United States Nuclear Regulatory Commission ' April 13, 1989 Attention: Document Control Desk Page 4 BYR 89-70 AAC source has the capacity and capability to power the equipment necessary to cope with a SB0 in accordance with NUMARC 87-00, Section 7, for the required coping duration determined in accordance with NUMARC 87-00, Section 3.2.5.

1. Condensate Inventory for Decay Heat Removal (Section 7.2.1)  ;

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It has been determined from Section 7.2.1 of NUMARC 87-00 that 13,272 gallons of water are required for decay heat removal for four hours. The minimum permissible condensate storage tank level, per Technical Specifications, provides 85,000 gallons of

- water, which exceeds the required quantity for coping with a four-hour SBO.

2. Class'1E Battery (ies) Capacity (Section 7.2.2)

Review of existing battery capacity calculations verifies that the batteries have sufficient capacity to meet SB0 loads for one hour.

3. Compressed Air (Section 7.2.3)

Air-operated valves relied upon to cope with a SB0 for one hour ,

can either be operated manually or have sufficient back-up sources independent of the preferred and blacked-out unit's  ;

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Class 1E power supply. Valves requiring manual operation, or that need back-up sources for operation, are identified in plant procedures.

4. Effects of Loss of Ventilation (Section 7.2.4)

The calculated steady-state ambient air temperature for the steam-driven Emergency Feedwater (EFW) Pump Room (the dominant area of concern for a Pressurized Water Reactor (PWR)) during a SB0 induced loss of ventilation is 140*F.  !

Reasonable assurance of the operability of SB0 response equipment in the above-dominant area has been assessed using Appendix F to NUMARC 87-00 and/or the Topical Report. The following procedure change is required to provide reasonable assurance for equipment operability: The turbine-driven emergency feedwater pump is located in the Auxiliary Boiler Room at YNPS. This room contains a large overhead door which opens to the outside. Although not credited in determining the maximum area temperature during the SB0 transient, the plant procedure has been revised to identify opening the door as a means to limit the temperature.

The assumption in NUMARC 87-00, Section 2.7.1, that the Control Room will not exceed 120*F during a SB0 has been assessed. The Control Room at YNPS does not exceed 120*F during a SB0.

Therefore, the Control Room is not a dominant area of concern; however, ventilation will be restored to the YNPS Control Room complex in one hour.

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' United States l Nuclear Regulatory Commission April 13, 1989 a Attention: Document Control Desk Page 5

-BYR 89-70

' 5. Containment Isolation (Section 7.2.5)

. The plant list of containment isolation valves has been reviewed to verify that valves which must be capable of being closed or that must be operated (cycled) under SB0 conditions can be positioned (with indication) independent of the preferred and blacked-out unit's Class 1E ac power supplies.

No plant modifications and/or associated procedure changes were determined to be required to ensure that appropriate containment integrity can be provided under SB0 conditions.

7. Reactor Coolant Inventory (Section 2.5)

The AAC source powers the necessary make-up systems to maintain adequate Reactor Coolant System inventory to ensure that the core is cooled for the required coping duration.

-The procedure changes identified in Part B.1 above have been implemente.d

' for SB0 events for the' duration of four hours in accordance with 100FR50.63(c)(1)(ii). The procedure changes identified in Part B.2 will be implemented by July 1, 1989.

We trust this information is satisfactory; however, if you.have any questions, please contact us.

Very truly ours, YANKEF/ATOMICELE RIC COMPANY g a b k./

Bruce L. Drawbh d Vice President and Manager of Operations BLD/b11/0213v Enclosure COMMONWEALTH OF MASSACHUSETTS)

)ss MIDDLESEX COUNTY )

Then personally appeared before me, Bruce L. Drawbridge, who, being duly sworn, did state that he is a Vice President and Manager of Operations of Yankee Atomic Electric Company, that he is duly authorized to execute and file l the foregoing document in the name and on the behalf of Yankee Atomic Electric I Company and that the statements therein are true to the best of his knowledge and belief.

KA/~b Ibbert H. Groce Notary Public My Commission Expires August 29, 1991 I

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