ML20064B633

Safety Evaluation Re Licensee Response to Station Blackout Rule.Advises That Addl Analyses & Confirmation Described in Recommendations Need to Be Completed

ML20064B633
Person / Time
Site:	Point Beach
Issue date:	10/03/1990
From:	Office of Nuclear Reactor Regulation
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ML20064B632	List: ML20064B631 ML20064B633
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NUDOCS 9010180224
Download: ML20064B633 (9)

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UNITED STATES

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g NUCLEAR REGULATORY COMMISSION

[.E' WASHINGTON, D. C, 20555 l

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r SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO STATION BLACK 0UT WISCONSIN-ELECTRIC POWER COMPANY POINT BEACH NUCLEAR PLANT, UNITS 1 AND 2 L

DOCKET NOS. 50-266 AND 50-301

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INTRODUCTION:

On July 21, 1988, the Code of Federal Regulations 10 CFR Part 50, was amended i

to include a new Section 50.63 entitled " Loss of All Alternating Current Power," (Station Blackout). The station blackout (SBO) rule requires that each light-water-cooled nuclear power plant be able to withstand and recover from an SB0 of specified duration, requires licensees to submit information as defined in 10 CFR 50.63 and requires licensees to provide a plan and schedule for conformance to the SB0 rule. The-SB0 rule further requires that the baseline l'

assumptions, analysis and related information be available for NRC review.

L Guidance for conformance to the rule is provided by (1) Regulatory Guide (RG)

L 1.155, " Station Blackout," (2) NUMARC 87-00, " Guidelines and Technical Bases L

for NUMARC Initiatives Addressing Station Blackout at Light Water Reactors,"

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and'(3) NUMARC 87-00, " Supplemental Questions / Answers and Major Assumptions,"

dated December 27,1989 (issued to the industry by Nuclear Management and Resources Council, Inc. (NUMARC)--January 4,1990).

To facilitate the NRC staff's review of licensee responses to the SB0 rule, the staff endorsed two generic response formats. One response format is for use by plants proposing to use an Alternate AC (AAC) power source and the other format is for use by plants proposing an AC independent response. The generic response formats provide the staff with a summary of the results from the licensee's analysis of the plant's SB0 coping capability. The licensees are s

expected to verify the accuracy of the results and maintain documentation that supports the stated results. Compliance to the SB0 rule is verified by a review of the licensee's submittal, an audit review of the supporting docu-mentation as deemed necessary, and possible follow-up NRC inspections to ensure that the licensee has implemented the appropriate hardware and/or procedure modifications that will be required to comply with the SB0 rule.

Staff's review does not necessarily include a concurrent site audit review of the supporting documentation.. However, a limited number of concurrent site audit reviews were performed to obtain a benchmark for licensee conformance with the documentation requirements of the SB0 rule. The Point Beach Nuclear

, Plant was one of the plants selected by the NRC for a site audit review.

9010180224 901003 PDR ADOCK 05000266 s

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Wisconsin Electric Power _ Company (WEPCO) has proposed using an existing gas turbine as an AAC power source and has submitted its response in the applicable generic response format. The licensee's original response was provided by a letter from C. W. Fay, WEPCO, to the Document Control Desk of the U.S. Nuclear Regulatory Commission (NRC), dated April 17, 1989.

A site audit was performed by a joint NRC/SAIC team headed by an NRC staff member on August 15-18, 1989.

On September 26, 1989, WEPC0 submitted a letter to the NRC that provided additional information about the status of the gas turbine generator as an alternate AC (AAC) power source for the Point Beach Nuclear Plant.

In ad-dition, the licensee provided supplemental responses with respect to the effects of loss of ventilation and gas turbine testing and reliability infor-mation by letters from C. W. Fay to the Document Control Desk, Nuclear

-Regulatory Commission, dated March 30 and June 29, 1990, respectively. The licensee did not specifically respond to the NUMARC 87-00 Supplemental Questions / Answers, stating that this information had been made available during the staff audit, i

- The licensee responses were reviewed by Science Applications International Corporation (SAIC) under contract to the NRC. The results of the review and the site audit are documented by a SAIC Technical Evaluation Report (TER),

l SAIC-89/1153, " Point Beach Nuclear Power Plant, Units 1 and 2, Station Blackout Evaluation," dated July 31,1990(AttachmentNo.1).

2.0 EVALUATION

After reviewing the licensee's SB0 submittals and the SAIC TER and in considera-tion of the information obtained by the NRC staff during the site audit review and the supplemental information provided by the licensee, the staff concurs with the conclusions as identified in the SAIC TER (refer to Attachment No. l'for details of the review).

Based on this review, the staff findings and recomenda-4 tions-are sumarized as follows.

2.1 Station Blackout Duration The licensee has calculated a minimum acceptable station blackout duration of 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> based on an offsite power design characteristic group of "P2," an Emer.

gency AC configuration group "D," and an EDG reliability target of 0.975.

After reviewing the available information from the site audit and in the 11cen-I see's submittals, RG 1.155, NUMARC 87-00 and SAIC's TER, the staff agrees with the 11censee's evaluation of an 8-hour SB0 coping duration.

2.2 Alternate'AC (AAC) Power Source The licensee has proposed to use an existing gas turbine as an AAC power source to operate systems necessary for the required SB0 coping duration of 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> and recovery therefrom.

2.2.1 General staff position on AAC power sources The definition in 10 CFR 550.2,)RG 1.155 and NUMARC 87-00, define AAC power sour in terms of four attributes: (1 connections to the offsite or the onsite AC power systems (2) minimum potential for common cause failure with offsite power or the onsite emergency AC power sources, (3) timely availability, and (4) re-quired capacity and reliability. More specifically, in regard to the fourth attribute, the SB0 rule reads as follows:

(4) Has sufficient capacity and reliability for operation of all systems required for coping with station blackout and for-the time required to bring and maintain the plant in safe shutdown (non-designbasisaccident).

In view of the-variety of types, capacities and capabilities of power sources proposed as AAC sources by various licensees, the staff has characterized pro-posed AAC power sources as being either optimum, fully capable or partially capable. This characterization, which relates only to the capacity attribute cited above, was necessary in order to facilitate the staff review of licensee responses to the SB0 rule.

It does not invalidate or revoke-any of the require-ments or guidance applicable to AAC power sources.

An optimum AAC power source design is one that is capable of powering simultan-

.cously both safety trains of normal safe shutdown systems and equipment.

Such a: design, following actuation of the AAC source, would provide completely re-dundant normal safe shutdown capability during an SB0 and recovery therefrom from the main control room.

A fully capable AAC power source design is one that is capable of powering at least one complete safety train of normal safe shutdown systems and equipment.

This includes decay-heat removal, battery charging, HVAC (heating, ventilation and air conditioning), w rgency lighting, and the associated controls and in-strumentation. Thus, although redundant capability is not available, a fully capable AAC source would enable attainment of safe shutdown during an SB0 and recovery therefrom from the main control room.

L A minimally capable AAC power source design is one that is not capable of power-ingall(orany)normalsafety-train-relatedsafeshutdownequipment;butitis capable of powering specific equipment that, in conjunction with extensive manual operator actions both inside and outside of the control room, is critical for attaining safe shutdown during an SBO. Appendix R diesels proposed as an AAC source are examples of minimally capable AAC sources. With this design, oper-ability of the main control room could not be assured unless the batteries were sized to operate for the SB0 duration, or battery charging capability was provided by the AAC source.

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.2.2.1.1 Connectability of AAC power sources The basic criteria governing the connectability of an AAC power source are con-tained in 10 CFR 50.2 (The AAC source should be connectable to but normally not l

connected to the offsite or onsite emergency AC power systems), and 10 CFR 50.63 l

(SB0 should not assume a concurrent single failure or design basis accident).

Therefore, in a two-unit site as a minimum an AAC source need only be connect-l able to one set of safe shutdown equipment for each unit, regardless of whether L

.that equipmelt is part of a safety train or not.

2.2.2 Procosed AAC power source The licensee proposes to make modifications to an existing gas turbine generator

-(GTG) and use it as an AAC source to power the safe shutdown loads of both blacked-out units.

Point Beach has only two emergency diesel generators (EDG) shared i

between two units, and a loss of all.AC power (loss of offsite power and two-EDGs) therefore results in an SB0 of both units. The 20 MW GTG has more than adequate capacity to power the safe shutdown loads of both units. The AAC power source would be available to power the loads within-1 hour following an SBO. The

. licensee stated in its letter dated June 29, 1990, that on June 15, 1990, an 8-hour SB0 duration gas turbine test was successfully performed. However, the licensee did not state in its letter whether or not the AAC source was avail-able'to power the SB0 loads within I hour after the onset of the SBO. The staff finds that the proposed AAC power source meets the guidelines of RG 1.155 l

and NUMARC 87-00,~ Appendix 0, except for the required reliability of 0.95, or better. As discussed in the attached TER, past historical data pertaining to the reliability of the GTG suggests that the GTG may not be able to obtain an acceptable reliability level of 0.95 or better.

~ Recommendation: The licensee should demonstrate using actual test data that L

the GTG can obtain and maintain a reliability of 0.95 or better. This demon-stration should be completed within a reasonable time period (approximately 2 years).

If the demonstration does not indicate an acceptable reliability of 0.95 or better, the licensee should propose an alternative or install:another AAC source to meet the guidelines of RG 1.155 and NUMARC 87-00. (By letter dated August 3, 1990 WEPC0 advised NRC that two additional EDGs would be installed. That letter did not indicate how the installation would relate to planning for station blackout.)

.The licensee should also complete the test to show that the AAC source (GTG) can

. power the SB0 loads within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> after the onset of the SBO.

2.3 Station Blackout Coping Capability I

The characteristics of the following plant systems and components were reviewed l

to assure that the systems have the availability, adequacy and capability to l

achieve and maintain a safe shutdown and recover from the SB0 for the required 8-hour coping duration.

2. 3. 1 Condensate inventory for decay heat removal The licensee stated in its SB0 submittal that the minimum permissible con-densate storage tank inventory of 10,000 gallons per unit (the minimum technical

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4 specification (TS) requirement) along with the initial steam generator fluid inventory is adequate to maintain steam generator decay heat removal capability.

for the 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> required to align the AAC power source. The licensee also stated that after 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />, service water from Lake Michigan would be available to provide water to the section of the auxiliary feedwater pumps, if required.

After reviewing the supporting documentation, technical specifications and i

'SAIC's TER, the staff concludes, for the reasons discussed in the attached TER, that the 10,000-gallon TS requirement may not be adequate considering the other priorities that the operators may be engaged in at the end of I hour.

Recommendation: The licensee should revise the TS to specify a minimum conden-sate tank storage inventory of 13,000 gallons per unit to )rovide assurance that adequate water is available to cope with an SB0 for t1e required 1-hour

duration, i-2.3.2 Class 1E battery capacity t

Initial calculations by the licensee indicate that the Class IE batteries have sufficient capacity to cope with an SB0 for the 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> prior to the availabil-ity of the AAC power source.

However, as noted in the attached.TER, the licen-see is in the process of updating the battery capacity calculations for all four i

batteries. Calculations or tests are also needed to assure that the battery voltages-are adequate to power the needed equipment after the I hour discharge of the batteries.

Recommendation: The licensee should complete the battery capacity calculations L

in conformance with RG 1.155, Section 3.2, and include the calculations and re-suits in the documentation package supporting the SB0 analyses. The licensee should develop and implement any modifications that are required to assure adequate battery capacity to power the needed equipment for an SB0 event.

2.3.3 Compressed air i

The licensee stated that no air-operated valves are needed to cope with an SB0

-during the first hour because the decay heat removal system (auxiliary feed-water system) operation is independent of both AC and instrument' air systems and because other air operated valves will fail in safe conditions.. Based on l-the statement, the staff agrees with the licensee that the compressed air is not L

needed to cope with an SB0 for 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> and, after 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />, the AAC power l

source will supply the compressed air.

i 2.3.4 Effects of loss of ventilation l

L The licensee does not expect the temperature rises in the areas of concern to adversely effect equipment operability because all ventilation systems will be restarted within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> after the onset of the 5B0. However, the licensee l

has calculated temperature rises that will occur in I hour for the computer, control, cable spreading, auxiliary feedwater pump and smallest vital switchgear

rooms, h-L

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These calculations showed that heat-up would not become excessive during the 1-hour period prior to the availability of the AAC source for any of these rooms except for the control and computer rooms. The licensee therefore decided to remove a sufficient number of ceiling tiles in these rooms to limit the heatup to an acceptable value by permitting circulation between the air volumes below L

and above the " drop ceilings." These modifications have been completed.

However, as noted in the attached TER, the licensee's heat-up calculations are based on methods other than those identified in NUMARC 87-00. The information provided is not sufficient to assure the NRC staff that the methodology used has been verified as to its ac:uracy, or that it has been found acceptable for the purpose for which it has been used. Also, more information is needed regarding the assumptions and initial conditions used in the calculations.

. In particular, the licensee needs to address the concerns expressed in the attached TER regarding the basis for selecting the: number and location of the ceiling tiles that have been removed in the control and computer rooms, and the basis for assuming that cabinet. doors do not need to be opened in the control room.

Recommendation:

1) The licensee should document additional information to demon-strate the acceptability of the methodology, assumptions, adjacent room effect, and initial conditions used in the heat-up calculations.

2) The-licensee also should confirm that the assumed initial room temperatures for the control and computer. rooms are maximum allowable values and not just typical values, and if necessary, the room heat-up calculations for these two rooms should be reanalyzed based on the higher initial temperature. 3) The licensee should document addi-tional justification as to why it is not necessary to open cabinet doors in the computer room, and the basis used for determining the number of and location of ceiling tiles that were removed in the control and computer rooms.

4) The licensee should describe the controls that are to be used to assure that the ceiling tiles are not replaced or reconfigured in the future. The licensee should maintain the additional information and any analyses performed as a result of these recommendations in the documentation supporting the SB0 submittal.

2.3.5 Containment isolation The licensee stated that the plant list of containment isolation valves needed.

for containment isolation was reviewed to verify that containment isolatdon is attainable and maintainable during an SBO. After-reviewing the available-documentation and the SAIC TER, the staff finds that the licensee's analysis is-in conformance with RG 1.155, Section 3.2.7.

The staff therefore concludes that the appropriate containment integrity can be maintained during an SB0 for the' required duration.

2.3.6 Reactor coolant inventory The licensee stated that reactor coolant system (RCS) inventory would be reduced by reactor coolant pump (RCP) seal leakage, but adequate initial RCS inventory is available for the 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> prior to bringing the AAC power on line.

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1 A review of reactor coolant inventory shows that the initial RCS inventory'is adequate for the 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> prior to the availability of the AAC power source, i

After the AAC power source becomes available, full RCS make-up ca)acity is l

established. The staff therefore agrees with the licensee that tie reactor coolant inventory will be adequately maintained to ensure core cooling for the required coping duration, u

2.4 Procedures and Training The licensee. currently has Emergency Operating Procedures (EOPs) for loss of l

all AC. power including the use of the GTG as an alternate source of AC power.

The staff concludes that the current procedures are applicable for an SBO, exce)t that they should be reviewed after modifications currently being made to tie 13.8 kV distribution system are completed, to assure that these changes are taken into account.

An additional EDG is also being considered and the pro-l cedures may need to be modified to reflect this addition if it is made. The licensee has committed to a review and revision of the procedures if the new EDG

.is installed.

Recommendation: The E0Ps should be reviewed and modified accordingly if neces-sary to acccunt for any changes made to the EDG/GTG configuration or the associ-ated 13.8 kV system, and appropriate training should be implemented to ensure an effective response to the SBO, 2.5 Proposed Modification The licensee is currently modifying the 13.8 kV distribution system to improve its reliability and-to separate the Unit 1 and Unit 2 offsite power sources.-

These modifications are not considered to be SB0 modifications.

By letter dated August 3, 1990, WEPC0 stated they are purchasing two additional emergency

-diesel generators.

If the EDGs are added to complement the-existing-EDGs, then

.they may be-used to change the emergency AC configuration group from "D" to "C"

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and.thereby reduce the required SB0 coping duration for the Point Beach plant.

If they are installed as independent AAC sources, they would need to be sized to have sufficient capacity for powering the SB0 loads of both units; or if installed as a supplementary AAC source to the existing GTG they may be used for justifying a lower GTG reliability requirement than 0.95, depending on how

.the EDG is electrically connected and used in the plant.

Recommendation:

Installation of additional EDG capacity. The SB0 coping duration-and evaluation would have to be re-evaluated subsequent to the licen-see providing information on the installation.

1 2.6 Quality Assurance and Technical Specifications The licensee has committed to incorporate equipment used to cope with an SB0 and not covered by current QA programs into a QA program that meets the guidance of RG 1.155, Appendix A.

The staff finds this to be an acceptable commitment.

- _. Thetechnicalspecifications(TSs)forthe.5B0equipmentarecurrentlybeing considered generically by the NRC in the context of the TS Improvement Program and remins an open item at this time.

However, the staff would expect that the plant procedures will reflect the appropriate testing and surveillance requirements to ensure the operability of the necessary SB0 equipment.

If the staff later determines that TS regarding the SB0 equipment is warranted, the licensee will be notified of the implementation requirements.

2.P EDG Reliability Program The licensee's submittal on SB0 did not specifically address the commitment to implement an EDG reliability program to conform to the guidance of RG 1.155, Position 1.2.

However, during the site audit review, the licensee stated that their reliability program would meet these guidelines. The staff finds this to be an acceptable commitment toward meeting the requirements of the SB0 rule.

2.8 Scope of Staff Review The station blackout rule (10 CFR 50.63) requires licensees to submit a response containing specifically defined information.

it also requires utilities "...

to have baseline assumptions,. analyses, and related information used in their coping evaluations available for NRC review." The staff or its contractor (SAIC) did not perform a detailed review of the proposed hardware and pro-cedural modifications which are scheduled for later implementation.

There-fore, based on its' review of the licensee supporting documentation and SB0 audit, the staff has identified the following areas for focus in any follow-up inspection or assessment that may be undertaken by the NRC to verify confor-mance with the SBO rule.

a.

Hardware and procedural modifications, b.

SB0 procedures in accordance with RG 1.155, Position 3.4, and NUMARC 87-00, Section 4, c.

0)erator staffing and training to follow the identified actions in tie SB0 procedures,

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d.

EDG reliability prcgram meets, as a minimum, the guidelines of RG 1.155, e.

Equipment and components required to cope with-an SB0 are incorpo-rated in a-QA program that meets the guidance of RG 1.155, Appendix A, f.

AAC power source (Gas Turbine Generator and associated systems necessary for operation) meets the guidelines of RG 1.155, C.3.3.5.5, and reliability test data indicates that the AAC source can realis-tically obtain and maintain a reliability of 0.95 or better, r

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Heating and ventilation calculations for the areas of concern daring an SB0 show that the systems and equipment therein are operable under_

r the SB0 conditions, h.

Class-IE battery and DC voltage drop calculations show that the J

batteries are adequate for the 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> prior to the availability.of the AAC power source, i.

Test data shows that the GTG can power the SB0 loads within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> of-the onset of the SB0; and j.

Actions taken pertaining to the specific recomendations noted in this SE.

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SUMMARY

AND CONCLUSIONS The staff has. reviewed the licensee's response to the station blackout (SBO) rule (10 CFR 50.63) and the Technical Evaluation Report (TER) prepared by the staff's consultant, Science Applications International Corporation (SAIC).

The staff and SAIC also-jointly conducted a site audit review of some of the supporting documentation for the SB0 response.- Based on the staff's review.

additional analyses and confirmations described in the recomendations pro-

- vided in this SE need to be completed. These include obtaining test data to

- establish that the GTG can realistically obtain a 0.95 reliability index, establishing testing and surveillance procedures to assure the GTG reliability 3

is maintained at an acceptable level, a test to demonstrate that the GTG can power SB0 loads within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> following an SBO, condensate storage tank (CST) technical specification revision,. battery capacity calculations, and additional

-l information and bases for heat-up calculations in the identified areas con-l

-taining equipment and systems needed to cope with'an-SB0 for 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />. The

.l licensee should maintain these analyses'and other documentation supporting the 1

SB0 submittal available for further inspection and assessment as may be under-taken by the NRC to further verify conformance with the SBO. Rule.

Based on its review of the submittal'and site audit, the staff' finds the licensee's design i

' and proposed method of dealing with an SB0 to be in conformance with the SB0'

rule contingent upon-receipt of confirmation from the licensee within 30 days that the recomendations identified in this SE will be implemented. The schedule for implementation should also be provided in accordance with 10 CFR 50.63(c)(4).

Attachment:

Technical Evaluation Report SAIC-89/1153

' Principal Contributor:

A. Toalston

. Date:

L 0

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