ELV-00432, Responds to Station Blackout Rule.Blackout Start Procedure & Restoration of Offsite Ac Power for Shutdown Added to Existing Procedures for Coping W/Station Blackout.Mods Required to Obtain 4 H Coping Duration Listed

Responds to Station Blackout Rule.Blackout Start Procedure & Restoration of Offsite Ac Power for Shutdown Added to Existing Procedures for Coping W/Station Blackout.Mods Required to Obtain 4 H Coping Duration Listed

ML20244D122
Person / Time
Site:	Vogtle
Issue date:	04/12/1989
From:	Hairston W GEORGIA POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
ELV-00432, ELV-432, NUDOCS 8904210159
Download: ML20244D122 (6)

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w. c. naimon in ELV-00432 Senor Vme Pmedem 1396n Nx!w Oueranons April 12, 1989 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D. C. 20555 PLANT V0GTLE - UNIT 1 AND 2 NRC DOCKET 50-424, 50-425 OPERATING LICENSES NPF-68, NPF-81 RESPONSE TO STATION ~ BLACK 0UT RULE Gentlemen:

Pursuant to 10 CFR 50.63(3), Georgia Power Company (GPC) hereby submits the conclusions of the station blackout analysis for Plant Vogtle Units 1 and 2.

Included in this letter are:

A. A proposed station blackout (SB0) duration - including a justification for the selection based on the redundancy and reliability of the onsite emergency AC power sources, the expected frequency of loss of offsite power, and the probable time needed to restore offsite power; B. A description of the procedures that will be implemented for station blackout events for the duration (as determined in 1 above) and for recovery therefrom; and C. A list and proposed schedule for any needed modifications to equipment and associated procedures necessary for the specified SB0 duration.

Regulatory Guide 1.155 " Station Blackout" describes a means acceptable to the NRC staff for meeting the requirements of 10 CFR 50.63. Regulatory Guide (RG) 1.155 states that the NRC Staff has determined that NUMARC-8700 " Guidelines and Technical Bases for NUMARC Initiatives Addressing Station Blackout At Light Water Reactors" provides guidance that is in large part identical to the RG 1.155 guidance and is acceptable to the NRC Staff for meeting these requirements. GPC has evaluated Plant Vogtle Units 1 and 2 against the requirements of the SB0 rule using the guidance from NUMARC-8700 for "AC Independent" plants, except where RG 1.155 took precedence. The results of this evaluation are detailed below. Applicable NUMARC-8700 sections are shown in parenthesis, go,9 1 l 8904210159 890412  ;

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U. S. Nuclear Regulatory Commission ELV-00432 Page Two~

A. Proposed Station Blackout Duration A. Regulatory Guide 1.155 and NUMARC-8700, Section 3 were used to determine a proposed SB0 coping duration of four hours. The following plant factors were identified in determining the proposed station blackout duration:

1. AC Power Design Characteristic Group is P1 based on:

a. Expected frequency of grid-related Loss of Offsite Power (LOOPS) does not exceed once per 20 years; (Section 3.2.1, Part 1 A, p. 3-3)

b. Estimated frequency of LOOPS due to extremely severe weather places the plant in ESW Group 2; (Section 3.2.1, Part 1B, p. 3-4)

c. Estimated frequency of LOOPS due to severe weather places the plant in SW Group 1; (Section 3.2.1, Part 1C, p. 3-7)

d. The offsite power system is in the I 1/2 Group; and (Section 3.2.1, Part 1D, p. 3-10)

e. The severe weather recovery factor was evaluated and did not affect the AC Power Design Characteristic Group determination.

(Regulatory Guide 1.155 Table 7)

2. The emergency AC power configuration group is C based on:

(Section 3.2.2. , Part 2C, p. 3-13)

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

b. Only one emergency AC power supply is necessary to operate safe shutdown equipment following a loss of offsite power.

(Section 3.2.2, Part 2B, p. 3-15)

3. The target Emergency Diesel Generator (EDG) reliability is 0.95.

A target EDG reliability of 0.95 was selected based on having a nuclear unit average EDG reliability for the last 20 demands greater than 0.90. (Section 3.2.4)

The modifications required to attain this proposed coping duration category are discussed in Section "C" below.

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U. S. Nuclear Regulatory Commission ELV-00432 Page'Three l

l B. Procedure Description Procedural requirements for coping with a station blackout have been reviewed by GPC. For offsite actions by those personnel charged with responsibility for control of the Southern Company transmission system, grid restoration .

procedures have been updated to meet the requirements of the Station Blackout j Rule. Specifically, the # allowing two documents are being added to those  ;

procedures:

o Black Start Procedure for Plant Vogtle; and l o Restoration of Offsite AC Power for the Shutdown of Plant Vogtle.

Onsite actions are addressed principally by three procedures: I l

o Loss of All AC; )

o Severe Weather; and $

o System Operating Procedures for Diesel Generator Operation.  ;

These procedures are being evaluated against the criteria of NUMARC 8700 for SB0 considerations. If necessary, changes to the procedures will be made to support the response to a SB0. The SB0 related procedure review and update '

are scheduled to be implemented within one year of receipt of approval by the NRC of this Station Blackout letter.  ;

C. Proposed Modifications and Schedule 1 The ability of Yogtle Electric Generating Plant, Units 1 and 2 to cope j with a station blackout for four hours was assessed using NUMARC-8700, l Section 7 with the following results: l

1. Condensate Inventory For Decay Heat Removal (Section 7.2.1) l It has been determined by application of the processes described in Section 7.2.1 of NUMARC-8700 that 203,000 gallons of water are required for decay heat removal for a four hour station blackout.  ;

The minimum permissible condensate storage tank level per technical i specifications provides 340,000 gallons of water, which exceeds the required quantity for coping with a four hour station blackout. l

2. Class IE~ Batteries Capacity (Section 7.2.2) l A battery capacity calculation was performed pursuant to NUMARC-8700, l Section 7.2.2 which verified that the Class IE batteries have '

sufficient capacity to meet station blackout loads for four hours.

It was noted, however, that lighting in the main control rooms will require augmentation to assure sufficient light after the initial 90 minutes of lighting provided by self-contained, gel-cell battery packs.

. s-U. 'S. Nuclear Regulatory Commission ELV-00432 Page Four

3. Compressed Air (Section 7.2.3)

No air-operated valves are relied upon to cope with a station i blackout for four hours.

4. Effects of^ Loss of' Ventilation (Section 7.2.4)

a. .The calculated steady state ambient air temperature for the steam driven AFW pump room (the dominant area of concern for a PWR) during a station blackout induced 1oss of ventilation is 1210F.

b. The assumption in NUMARC-8700, Section 2.7.1 that the control room will not exceed 1200F during a station blackout has been assessed. The control room at Plant Vogtle Units 1 and 2 does not exceed 1200F during a station blackout. Therefore, the control room is not a dominant area of concern.

c. The bulk ambient temperature in two of the class IE 125 VDC/120 VAC equipment rooms may approach 1270F during a station blackout, resulting in a derating of the trip setpoint of five molded case circuit breakers (each unit) below their potential current loading.

Reasonable assurance of the operability of station blackout response equipment in the above dominant areas of concern was assessed using the October 1988 Revision 1 to Appendix F of NUMARC 87-00 and/or the October 1988 NUMARC 87-00 Topical Report, " Guidelines and Technical Bases for NUMARC Initiatives Addressing Station Blackout At Light Water Reactors". In order to provide reasonable assurance for equipment operability, five circuit breakers (each unit) will be replaced with larger size circuit breakers to avoid the potential of spurious tripping.

5. Containment Isolation (Section ~ 7.2.5)

The plant li-t of containment isolation valves was reviewed, and it was verified that valves which must be capable of being closed or that must be operated (cycled) under station blackout conditions can be positioned (with indication) independent of the preferred and blacked-out unit's Class IE power supplies. It was determined that no plant modifications and/or associated procedure changes are required to ensure that appropriate containment integrity can be provided under SB0 conditions.

U. S. Nuclear Regulatory Commission ELV-00432 Page Five'

6. Reactor- Coolant' Inventory (Section 2.5)

The ability to maintain adequate reactor coolant system inventory for four hours under SB0 conditions was assessed to ensure that core cooling could be sustained. The generic analyses listed in~Section 2.5.2 of NUMARC-8700 were used for this assessment and are applicable to the specific design of Yogtle Electric Generating Plant Units 1 and 2. This assessment employed an assumption of a seal leakage rate of 25 gpm per Reactor Coolant Pump (RCP) in accordance with the referenced guidance. However, this assumption is currently the subject of a resolution program (NRC Generic Issue 23). If the resolution of Generic Issue 23 indicates that modifications are necessary in order to maintain RCP seal leakage below a value that is consistent with the coping duration they will be implemented following development and acceptance of the modification. Based on current assumptions, make-up systems beyond those currently available under SB0 conditions are not required to maintain core cooling under natural circulation.

In summary, the following modifications will be required to attain the proposed four hour coping duration category:

1. Lighting in the common main control room will be augmented to assure sufficient lighting after the 90 minutes of initial lighting provided by self-contained, gel-cell battery packs.

2. Five circuit breakers (each unit) will be replaced with larger size circuit breakers to avoid the potential of spurious tripping, due to temperature induced shift in tripping characteristics at elevated ambient temperatures.

3. If the resolution of Generic Issue 23 indicates that modifications to RCP seals are required, they will be implemented according to our current RCP maintenance schedule after the appropriate modifications are available.

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U. S. Nuclear Regulatory Commission ELV-00432 Page Six The modifications and associated procedure changes identified in Sections B and C above, with the exception of modifications to the RCP seals, will be completed one year from the time that notification of acceptance of this letter (and proposed actions) is provided by the Director, Office of Nuclear Reactor Regblation in accordance with 10 CFR 50.63(3).

Sincerely, (A/.b. llf+ X W. G. Hairston, III HWM/gm xc: Georgia Power Company Mr. P. D. Rice Mr. C. K. McCoy Mr. G. Bockhold, Jr.

Mr. J. P. Kane Mr. J. A. Bailey NORMS U. S. Nuclear Regulatory Commission Mr. Stewart Ebneter, Regional Administrator Mr. J. B. Hopkins, Licensing Project Manager, NRR (2 copies)

Mr. J. F. Rogge, Senior Resident Inspector - Operations, Yogtle i

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