ML20069N487

Station Blackout Evaluation, Final Technical Evaluation Rept

ML20069N487
Person / Time
Site:	Davis Besse
Issue date:	08/17/1990
From:	SCIENCE APPLICATIONS INTERNATIONAL CORP. (FORMERLY
To:	NRC
Shared Package
ML20069N490	List: ML20069N487
References
CON-NRC-03-87-029, CON-NRC-3-87-29 SAIC-90-1056, TAC-68536, NUDOCS 9008230016
Download: ML20069N487 (23)

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TECHNICAL EVALUATION REPORT DAYl$ BES$E NUCLEAR POWER STATION STATION BLACK 0UT EVALUATION TAC No. 68536 SA1C:

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EcienceApplicatkwsshiemationalCcwps ' ion An Employee Owned Company i

Final August 17, 1990

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Prepared fort i

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TABLE OF CONTENTS

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1.0 BACKGROUND

-2.0 REVIEW PRJCESS 3

3.0- -EVALUATION 6

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3.1. Proposed Station Blackout Duration 6

3.2-_ Alternate AC (AAC) Power fource.................

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3.3 Station Blackout Coping Cspability Il 1

3.4' Proposed = Procedures and Training.................

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3.5 Proposed Modifications 16 f

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3.6-Quality Assurance and Technical Specifications..

17 4.0. CONCLUSIONS.

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5.0 REFERENCES

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e TECHNICAL EVALUATION REPORT DAVIS BESSE NUCLEAR POWER STATION STATION BLACK 0UT EVALUATION

1.0 BACKGROUND

On July 21, 1988, the Nuclear Regulatory Commission (NRC) amended its regulations in 10 CFR Part 50 by adding a new section, 50.63, " Loss of All Alternating Current Power" (1).

The objective of this requirement is to usure that all nuclear power plants are capable of withstanding a station blackout (SBO) and maintaining adequate reactor core cooling and appropriate containment integrity for a required duration.

This requirement is based on information developed under the commission study of Unresolved Safety Issue A 44, ' Station Blackout" (2 6).

The staff issued Regulatory Guide (RG) 1.155, " Station Blackout," to provide guidance for meeting the requirements of 10 CFR 50.63 (7). Concurrent with the development of this regulatory guide, the Nuclear Utility Management and Resource Council (NUMARC) developed a document entitled, " Guidelines and Technical Basis for NUMARC Initiatives Addressing Station Blackout at Light Water Reactors," NUMARC 87-00 (8).

This document provides detailed guidelines and procedures on how to assess each plant's capabilities to comply with the SB0 rule. The NRC staff reviewed the guidelines and analysis methodology in NUMARC 87 00 and concluded that the NUMARC document provides an acceptable guidance for addressing the 10 CFR 50.63 requirements.

The application of this method results in selecting a minimum acceptable 580 duration capability from two to sixteen hours depending on the plant's characteristics and vulnerabilities to the risk from station blackout.

Th plant's characteristics affecting the required coping capability are:

the redundancy of the onsite emergency AC power sources, the reliability of onsite emergency power sources, the frequency of loss of offsite power (LOOP), and the probable time to restore offsite power.

1

In order to achieve a consistent systematic response from licensees to the SB0 rule and to expedite the staff review process, NUMARC developed two generic response documents.

These documents were reviewed and endorsed by the NRC staff (19) for the purposes of plant specific submittals.

The documents are titled:

1.

' Generic Response to Station Blackout Rule for Plants Using Alternate AC Power," and 2.

" Generic Response to Station Blackout Rule for Plants Using AC Independent Station Blackout Response Power."

A plant-specific submittal, using one of the above generic formats, provides only a summary of results of the analysis of the plant's station blackout coping capability.

Licensees are expected to ensure that the baseline assumptions used in NUMARC 87 00 are applicable to their plants and to verify the accuracy of the stated results.

Compliance with the SB0 rule requirements is verified by review and evaluation of the licensee's submittal and audit review of the supporting documents as necessary.

Follow up NRC inspections assure that the licensee has implemented tha necessary changes as required to meet the SB0 rule.

In 1989, a joint NRC/SAIC team headed by an NRC staff member performed audit reviews of the methodology and documentation that support the licensees' submittals for several plants.

These audits revealed several deficiencies which were not apparent from the review of the licensees' submittals using the agreed upon generic response format.

These deficiencies raised a generic question regarding the degree of licensees' conformance to the requirements of the SB0 rule.

To resolve this question, on January 4, 1990, NUMARC issued additional guidance as NUMARC 87-00 Supplemental Questions / Answers (14) addressing the NRC's concerns regarding the deficiencies.

NUMARC requested that the licensees send their supplemental responses to the NRC addressing these concerns by March 30, 1990.

2 1

2.0 REVIEW PROCESS i

The review of the licensee's submittal is focused on the following areas consistent with the positions of RG 1.155:

A.

MinimumacceptableSB0 duration (Section3.1),

l B.

SB0 coping capability (Section 3.2),

C.

Procedures and training for SB0 (Section 3.4).

D.

Proposed modifications (Section 3.3), and E.

Quality assurance and technical specifications for SB0 equipment 1

(Section3.5).

r-For the determination of the proposed minimum acceptable 580 duration, the following factors in the licensee's submittal are reviewed:

a) offsite powerdesigncharacteristics,b)emergencyACpowersystemconfiguration,c) determination of the emergency diesel generator (EDG) reliability consistent with NSAC-108 criteria (9), and d) determination of the accepted EDG target reliability.

Once these fat. tors are known, Table 3 8 of NUMARC 87 00 or Table 2 of RG 1.155 provides a matrix for determining the required coping duration.

For the SCO coping capability, the licensee's submittal is reviewed to assess the availability, adequacy and capability of the plant systems and components needed to achieve and maintain a safe shutdown condition and recover from an SB0 of acceptable duration which is determined above. The review process follows the guidelines given in RG 1.155, Section 3.2, to assure:

a.

availability of sufficient condensate inventory for decay heat

removal, 3

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adequacy of the class IE battery capacity to support safe

shutdown, c.

availability of adequate compressed air for air operated valves necessary for safe shutdown, d.

adequacy of the ventilation systems in the vital and/or dominant areas that include equipment necessary for safe shutdown of the

plant, e.

ability to provide appropriate containment integrity, and f.

ability of the plant to maintain adequate reactor coolant system inventory to ensure core cooling for the required coping duration.

The licensee's submittal is reviewed to verify that required procedures (i.e., revised existing and new) for coping with SB0 are identified and that appropriate operator training will be provided.

The licensee's submittal for any proposed modifications to emergency AC sources, battery capacity, condensate capacity, compressed air capacity, appropriate containment integrity and primary coolant make up capability is reviewed. Technical specifications and quality assurance set forth by the licensee to ensure high reliability of the equipment, specifically added or assigned to meet the requirements of the SB0 rule, are assessed for their adequacy.

The licensee's proposed use of an alternate AC power source is reviewed to determine whether it meets the criteria and guidelines of Section 3.3.5 of RG 1.155 and Appendix B of NUMARC 87 00.

l This SB0 evaluation is based on the review of the licensee's submittals I

dated April 17, 1989 (10), and March 30, 1990 (12), and the information j

available in the plant Updated Safety Analysis Report (USAR) (11); it does not include a concurrent site audit review of the supporting documentation.

Such 4

t an audit may be warranted as an additional confirmatory action.

This determination would be made and the audit would be scheduled and performad by the NRC staff at some later date 5

3.0 EVALUATION 3.1 Proposed Station Blackout Duration Licensee's submittal The licensee, Toledo Edison (TE) Company calculated (10 and 12) a minimum acceptable station blackout duration of four hours for the Davis Besse Nuclear Power Station (DBNPS) site.

The licensee stated th:t no_ modifications are required to attain this coping duration.

The plant factors used to estimate the proposed SB0 duration are:

1.

Offsite Power Design Characteristics The plant AC power design characteristic group is "P1" based on:

a.

Independence of the plant offsite power system characteristics of "!!/2 "

b.

Expected frequency of grid related LOOPS of less than one per 20 years, c.

Estimated frequency of LOOPS due to extremely severe weather (ESW) which places the plant in ESW group "2,"

and d.

Estimated frequency of LOOPS due to severe weather (SW) which places the plant in SW group "2."

2.

Emergency AC (EAC) Power Configuration Group The EAC power configuration of the plant is "C."

DBNPS is equipped with two emergency diesel generators. One EAC power supply is necessary to operate safe shutdown equipment following a loss of offsite power.

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_ 3.

Target Emergency Diesel Generator (EDG) Reliability r

The licensee has selected a target EDG reliability of 0.95.

The 3

1 selection of this target reliability is based on having an average EDG reliability of greater than 0.95 for the last 100 demands l

consistent with NUMARC 87 00, Section 3.2.4.

i Review of 1.icensee's Submittal a

Factors which affect the estimation of the SB0 coping duration are:

the independence of the offsite power system grouping, the estimated frequency of LOOPS due to ESW and SW conditions, the expected frequency i

of grid related LOOPS, the classification of EAC, and the selection of EDG target reliability.

Using Table 3 2 of NUMARC 87 00, the expected frequency of LOOPS due to ESW conditions place the DBNPS site in ESW group "2."

Using Table 3 3 of NUMARC 87 00, the expected frequency of LOOPS at DBNPS due to SW condition is group "3" for offsite power transmission lines en one right of way, or group "2" for offsite power transmission lines on two or more rights of way.

The licensee submits an SW group of "2."

A review of the plant USAR (11) indicates that th:

plant has three transmission lines, and the liner, can be considered to traverse on two rights of-way.

The licensee stated that the independence of the plant offsite power system (Figure 1) grouping is "11/2." A review of the DBNPS USAR indicates that:

i

- 1.

All offsite power sources are connected through a single switchyard; 2.

During_ normal power operation, the essential buses are powered from the unit main generator, through the auxiliary power transformer; 7

3.

Uponlosspowerfromthemaingenerator(preferredpowersource),

there is 'an automatic transfer of all essential buses to two Start up Transformers; t

4.

Each transformer powers one division of essential buses; 5.

Each of the Start up Transformers has sufficient capacity to serve as a complete reserve power source for the station auxiliarieb in the event of failure of the Unit Auxiliary Power Transformer supply; and P

6.

Upon loss of_ power from one of the Start up Transformer both 4.16 kV essential buses will be powered from the other Start up Transformer by a manual transfer.

Based on these and the criteria stated in Table 5 of RG 1.155, the plant independence of offsite power system group is "12."

The EAC classification of DBNPS is 'C."

We are unable to verify the assignment of the EDG target reliability at this time.

However, based on the information in the NSAC 108, which gives the EDG reliability data at U. S. nuclear reacters for calendar years 1983 to 1985, the EDGs at DBNPS experience an average reliability of 0.963 per diesel per year.

Using this data, it appears that the target EDG reliability.(0.95)

I' selected (10)andcommitted(12)tobythelicenseeisappropriate.

However, an audit may be required to ensure compliance, and to identify whether the DBNPS has any formal EDG reliability program consistent with the guidance of the RG 1.155, Section 1.2,-and NUMARC S7 00, Appendix D.

With' regard:to the expected frequency of grid related LOOPS at the site, p_

we can n'ot confirm the stated results. The available information in l

NUREG/CR 3992 (3), which gives a compendium of information on the loss

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of offsite power'at' nuclear power plants in U.S., indicates that DBNPS did not have any symptomatic grid related LOOP prior to the calendar 8

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year 1984.

In the absence of any information, we agree with the licensee's statement.

Based on the above the offsite power design characteristic of the DBNPS site is 'P1' with a minimum required SB0 coping duration of four hours.

3.2 Alternate AC (AAC) Power Source Licenseo's Submittal The licensee proposes to install a diesel generator (DG) as an AAC power source, see figure 1 (10).

The licensee stated that, once the modifications are completed, the AAC power source will meet the criteria specified in Appendix B to NUMARC 87 00.

The AAC power source will be available within ten minutes of the onset of an SB0 event, and will have sufficient capacity and capability to operate systems necessary for coping with an SB0 for a four hour duration.

Review of Licensee's Submittal Although the licensee is committed to install a non class lE diesel which meets the criteria specified in Appendix B of NUKARC 87 00, the licensee did not provide any technical information to evaluate the AAC power source.

Since the AAC is available within 10 minutes and no AC-independent coping has been performed, it is assumed that the AAC source will power all the required functions during an 5B0 event.

Our estimate of the SB0 loads indicate that the 'roposed AAC power source should have approximately the same capacity

'e present EDGs.

If the proposed AAC power source is of less capacity than the prestnt EDGs, then the licensee needs to provide analysis of the required loads for the SB0 event.

In addition, in the interest of safety it is preferred that the proposed AAC power source be capable of being connected to both essential division buses. The present configuration shows that the proposed AAC is only capable of being connected to one division.

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e 3.3 Station Blackout Coping Capability The licensee stated that since the proposed AAC power source will be availio within 10 minutes, the coping evaluations for class lE battery capacity, compressed air, and containment isolation need not to be addressed in acenrdance with 10 CFR 50.63(c)(2). We consider the licensee's statement to mean that the functions needed to cope with an SB0 are available, and they are adequately powered from the proposed AAC power source for the required 9uration. The plant coping capability with an SB0 event for the-required duration of four hours is assessed based on the following results:-

1, Condensate Inventory for Cecay Heat Removal Litex;ee % Submittal The licensee's. submittal stated that -62,000 gallons of water are required for the decay heat removal during the four hour coping period.

The minimum permissible condensate storage-tank level per technical specificatione provides 250,000 gallons of water, which

-exceeds the required quantity for coping with a 4-hour SB0 event.

Review of Licensee's Submittal The icensee stated that -62,000 gallons of water are needed for decay heat removal during a 4-hour SB0 event.

Using the expression provided-in NUMARC 87-00, we have estimated that t*

- water required for removing decay heat would be ~62,600 gallou This estimate is based on a maximum licensed core thermal rating of 2827 MWt, or 1027. of 2772 MWt (Table 15.2.5-1 of the plant USAR).

Based on the above, the site would need a minimum of -62,600 gallons of condensate water to provide assurance of decay heat rem'/ral during an SB0 event.

The licensee stated that the plant te xiical specifications require a minimum condensate level of 11

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25s,000 gallons be available in the condensate storage tanks.

Therefore, we agree with the licensee that the site has sufficient condensate to cope with an SB0 of four hours duration, 2.

Class lE Battery capacity Licensee's submittal Since the AAC power source will be available within 10 minutes of the onset of an SB0 event, no analysis of class IE battery capacit, calculation is provided.

Review of Licensec's submittal According to the USAR, DBNPS is equipped with four station betteries which are arranged to form two independent DC systems.

Ea'ch of the two-station-battery system; has been sized to supply the anticipated DC and Instrument AC supply for one hour after the loss of the battery charger supply.

The loads and operating requirements during the worst case accident, (a LOOP, and a LOCA)

. With no AC power available, require a battery with a one hour capacity of GOO Ampere Hours (AH) and a one minute rating of 1360

' Amperes (the capacity and ampere = rating of all four batteries is based ~on the' battery with the largest load). The station batte inve-a one-hour capacity of 750 AH, and a one minute ratir,, of-1600 Amperes, which appears to have. sufficient capacity to satisfy the SB0 load for the first 10 minutes prior to the powering of the battery chargers.

With the proposed AAC power l

source available and powering the necessary battery chargers within 10 minutes, the operating station-battery will-have L

. sufficient capacity to carry the intermediate time for the 4-hour-l SB0 load.

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Compressed Air Licensee's. Submittal Since the AAC power source will be available within 10 minutes and pcwer the plant air system, no analysis of the compressed air system is provided.

Review of Licensee's Submittal A review of the EDG Load Tables (USAR Table 8.3-1) indicates that the emergency instrument air (EIA) compressor will be powered.

This means that the compressor is connected to an essential bus and it is, therefore, expected to be powered from the proposed AAC

_ power source during an SB0 event.

Since the present configuration of_ the-proposed AAC power source is on1y capable of being-connected to one division of emergency buses, the licensee needs to verify that EIA is' powered.

4.

Effects of Loss of Ventilation Licensee's Submittal The licensee stated that the AAC power source provides power to heating,ventilationandcirconditioning(HVAC)systemsserving-the dominant areas of-concern.

Therefore, consistent with the NUMARC 87-00, Sections 7.2.4 and 7.1.2, the effects-of loss of ventilation were not assessed. The licensee added that no modifications and/or procedures are required to provide reasonable assurance-for operability of ventilation equipment.

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Review of Licensee's submittal The licensee's action is consistent with the-guidance provided by NUMARC and NRC. We would like to empu: size that'the dominant areas of concern should not be limited to those identified in NUMARC 87-00.

The licensee needs to ensure that other areas which have heat generation sources, i.e., operating equipment, are provided with appropriate area cooling.

1 5.

Containment Isolation Licensee's Submittal The licensee stated that the AAC power source will be available within 10 minutes.

Therefore,

.9 analysis of the containment isolation valves (CIVs) is necessary for the_SBO.

Review of Licensee's Submittal The licensee's action is consistent with the guidance of NUMARC 87-00, Section 7.1.2.

This is based on the assumption that the proposed AAC power source is available to CIVs requiring closure capability during an SB0 event.

The single line diagram, see Figure 1, indicates that the proposed AAC power source will be available to power one-division of essential buses.

The licensee needs to determine if appropriate containment integrity can be assured with the AAC power source available only to one division.

6.

Reactor Coolant Inventory Licensee's submittal The licensee stated that the,AAC source powers the necessary make-up systems to maintain adequate reactor coolant system (RCS) 14

e inventory to ensure that the core is cooled for the required coping duration.

Review of Licensee's-Submittal Reactor coolant make up is necessary to replenish the RCS inventory losses due to the reactor coolant pump seal leakage (25 gpm per puin.q per NUMARC 87-00 guideline) and the technical specifications maximum allowable leakage (estimatad to be 25 gpm).

The make-up,-or the charging, system at DBNPS has two centrifugal pumps.

Each pump has a design flow capacity of 150 gpm.

Therefore, one charging pump would be able to replenish the assumed 125 gpm RCS leakage without loss of inventory, assuming that no shrinkage occurs.

3.4 Proposed Procedures and Training Licensee's Submittai The licensee stated that the following plant procedures have been reviewed per guidelines in NUMARC 87-00, Section 4:

1.

Station blackout response guidelines,

-2.

AC power restoration,_and p

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3.

Severe weather.

The licensee-listed the name(s) of the plant procedures in each of the-L above-categories _ in the plant SB0 submittal'. The licensee stated that these procedures will be revised, if necessary, to meet NUMARC 87-00 guidelines.

Review of. Licensee's h bmittal We neither received nor reviewed the affected SB0 procedures. We consider these procedures as plant specific actions concerning the 15

4 required activities to cope with an SB0.

We believe that it is the licensee responsibility to revise and implement these procedures, at needed, to mitigate _an SB0 event and to assure that these procedures are complete 'and correct, and that the associated traine; needs are carried out accordingly.

3.5 Proposed Modifications Licensee's Submittal The licensee has proposed to install an AAC power source consisting of a non class lE diesel generator and required support systems with indications and controls to allow remote operation from the control room.- The modifications are currently planned to be completed during seventh refueling scheduled to begin September 1, 1991.

The licensee stated that, once modifications are completed, this proposed AAC power source will meet the criteria specified in Append,x B to NUMARC 87-00.

Procedures for operation, maintenance, surveillance, and testing of the AAC power source will be revised or created as necessary.

Review of Licensee's submittal The licensee did not provide technical information on the proposed modifications to review. -We believe the. proposed modifications enhance the plant ability to cope with an SB0 event.

We have one concern, however.

-Although neither NUMARC 87-00 nor RG 1.155 specifies that the AAC power source be connectible to both divisions of essential buses, we believe this connectiblity provides a flexibility that would not be-available otherwise. -It is true that we_ should not consider any other equipment failures'during an SB0 event.

However, should one of the-required equipment on one division be out for maintenance the redundant equipment can be made operational _ on the other division only if such connectiblity exists.

The present configuration shows that the proposed AAC is only capable of being connected to one division.

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3.6 Quality Assurance and Technical Specifications The licensee did not provide any information on how the plant complies with the requirement of RG 1.155, Appendices A and B.

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4.0 CONCLUSION

S Based on our review of the licensee's submittals and the information available in the USAR for Javis-Besse Nuclear Power Station, we find that the submittal conforms with the requirements of the SB0 rules and the guidance of RG 1.155 with the following exceptions:

1.

Emergency Diesel Generator Reliability Program The licensee's submittal does not document the conformance of the plant's EDG reliability program with the guidance of the RG 1.155, Section 1.2 and NUMARC 87 00, Appendix 0.

However, it is committed to maintain the targeted EDG reliability of 0.95.

2.

AAC Power Source Although the licensee is committed to install a non-class lE diesel which meets the criteria specified in Appendix B of NUMARC 87-00, the licensee did not provide any technical information to evaluate the AAC power source.

Since the AAC is available within 10 minutes and no AC-independent coping has been performed, it is assumed that the AAC source will power all the required functions during an SB0 event.

Our estimate of the SB0 loads indicate that the proposed AAC power source should have approximately the same capacity of the present EDGs.

If the proposed AAC power source is of less capacity than the present EDGs, then the licensee needs to provide analysis of the required loads for the SB0 event.

In addition, in the interest of safety it is preferred that the proposed AAC power source be capable of being connected to both essential division buses. The present configuration shows that the proposed AAC is only capable of being connected to one

division, 18 l

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Effects of Loss of Ventilation The licensee states that the AAC power source will be available I

within 10 minutes and provides power to HVAC systems serving the dominant-areas of concern.

We would like to emphasize that-the dominant areas of concern should not be limited to those identified in NUMARC 87 00.

The licensee needs to ensure that other areas which house operating systems are provided with appropriate cooling.

4.

Proposed Modification The licensee did not provide technical information on the AAC power source, therefore no review can be performed (see also item

2. above).

5.

Quality Assurance and Technical Specifications The licensee's submittal does not document the conformance of the plant's SB0 equipment with the guidance of RG 1.155, Appendices A, and B.

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5.0 REFERENCES

1.

The Office of Federal Register, " Code of Federal Regulations Title 10 Part 50.63," 10 CFR 50.63, January 1, 1989, 2.

U.S. Nuclear Regulatory Commission, " Evaluation of Station Blackout Accidents at Nuclear Power Plants Technical Findings Related to Unresolved. Safety Issue A 44," NUREG 1032, Baranowsky, P. W., June 1988.

3.

U.S. Nuclear Regulatory Commission, " Collection and Evaluation of Complete and Partial losses of Offsite Power at Nuclear Power Plants,"

NUREG/CR-3992, February 1985.

4.

U.S. Nuclear Regulatory Commission, " Reliability of Emergency AC Power System at Nuclear Power Plants," NUREG/CR 2989, July 1983.

5.

U.S. Nuclear Regulatory Commission, " Emergency Diesel Generator Operating Experience, 1981 1983," NUREG/CR 4347 December 1985.

6.

U.S. Nuclear Regulatory Commission, " Station Blackout Accident Analyses (PartofNRCTaskActionPlanA44),"NUREG/CR3226,May1983.

7.

U.S. Nuclear Regulatory Commission Office of Nuclear Regulatory Research, " Regulatory Guide 1.155 Station Blackout," August 1988, i

8.'

Nuclear Management and Resources Council, Inc., " Guidelines and

. Technical Bases for NUMARC Initiatives Addressing Station Blackout at Light Water Reactors," NUMARC 87-00, November 1987.

+

9.

Nuclear Safety Analysis Center, "The Reliability of Emergency Diesel Generators at-U.S. Nuclear Power Plants," NSAC 108,' Wyckoff, H.,

-September 1986.

20

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10.1 Shelton, D. C., letter to the Document Control Desk of the U.S. Nuclear Regulatory Commission, " Response to Station Blackout Rule," Docket No.

50-346, License No. NPF-3, Serial No.1651, dated April 17, 1989.

11.

Davis Besse Nuclear Power Station Updated Safety Analysis Report.

12.

Shelton, D. C., letter to the Document Control Desk of the U.S. Nuclear Regulatory Commission, " Supplemental Station Blackout Response for Davis-Besse," Docket No. 50-346, License No. NPF 3, Serial No.1651, dated April 2, 1990.

13.

Thadani, A. C., Letter to W. H. Rasin of NUMARC,-" Approval of NUMARC DocumentsonStationBlackout(TAC 40577),"datedOctober7,1988.

14.-

Thadani, A; C., letter to A. Marion of NUMARC, " Publicly-Noticed Meeting December 27, 1989," dated January 3,1990 (confirming "NUMARC 87-00 Supplemental Questions / Answers," December 27,1989).

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