ML20091C832

Forwards Attachment & Encl Omitted from Re Safety Evaluation & Request for Addl Info Concerning Station Blackout Analysis for Facility

ML20091C832
Person / Time
Site:	Comanche Peak
Issue date:	04/01/1992
From:	Bergman T Office of Nuclear Reactor Regulation
To:	TEXAS UTILITIES CO.
Shared Package
ML20091C836	List: ML20091C832
References
NUDOCS 9204060238
Download: ML20091C832 (1)

Text

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i April 1,

1992 I

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Recipients of February 27, 1992 Letter to TU Electric

Subject:

SAFETY EVALUATION AND REQUEST FOR ADDITIONAL INFORMATION CONCERNING STATION BLACKOUT ANALYSIS FOR COMANCHE PEAK ELECTRIC STATION, UNIT 1 (TAC NO. M68530)

In the distributton of the subject letter, the attachment to the Safety Evaluation was inadvertently not distributed.

Attachrd is a copy of the let t er with the appropriat e enclosures.

We are sorry for any inconvenience this may have caused.

Mtomasll.

GA Project Manager Le gaa,

Project Direc or te IV-2 Division of Rea or Projects llI/IV/V Office of Nuclear Reactor Regulation 3)Fo i 9204060238 920401

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Mpa aseg'o, UNIT cD ST ATES l

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NUCLEAR REGULATORY COMMISSION

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february 27, 1992

. Docket Nos. 50-445-and 50-446 Mr. William J. Cahill, Jr.

Group Vice-President, Nuclear LTU Electric Company

-400-North Olive Street, L.B. 81 Dallas, Texas 75201

Dear Mr. Cahill:

SUBJECTr SAFETY EVALUATION AND REQUEST FOR ADDITIONAL INFORMATION CONCERNING STATION BLACK 0UT ANALYSIS F,0R COMANCHE PEAK STEAM ELECTRIC STATION, UNIT _l (TAC NO.-M58530)

The TU Electric-Company responses-to _the requirements of the Station Blackout

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(580) rule,_-10 CFR 50,63, were provided by letters dated November 5, 1990 and November-22,: 1991. The information provided by these responses has been

reviewed by the NRC staff-and Science Applications International Corporation

-(SAIC);funder contract to th'e NRC. The enclosure provides the staff's preliminary safety evaluation -(SE) and the-SAIC Technical. Evaluation Report

-(TER).SAIC-91/1803, " Comanche Peak Steam Electric Station, Unit 1. Station Blackout Evaluation," (Attachment'to Enclosure).. The SE contains recommendations which include a request for additional information (revised response) to be submitted for NRC review.

This response, which is limited to Lthe. values and justification-of input parameters used in the control room Etemperature transient analysis,.should be submitted no later than March 31, 1992.

ilniaddition, the following areas may require followupfinspection by the NRC to-

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verify that the requirements of the SB0 rule have been satisfied. The staff i

is developing guidance for this followup inspection to verify the_following:

a.1 Hardware and: procedural modifications;

b. iSB0 procedures in-accordance with R.G. 1.155, Position 3.4, and

<NUMARC 87-00, Section 4; c.; Operator staffing and-training to follow the identified actions in the procedures;;

id! - Emergency Diesel Generator (EDG) reliability program meets',- as a minimum,-

the guidelines of R.G. I.155;-

e. -Equipment and components required to cope with an-SB0 are incorporated in

-a-QA program 1that meets the guidance of R.G. 1.155, Appendix A, and;

f. ~ Actions taken pertaining to the specific recommendations noted in the SE.

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-w LMr. William'J, Cahill,-Jr. 1

-The guidance provided on Technical Specifications (TS) related to S00 states that the TS should be' consistent with the Interim Commission-Policy Statement-on Technical. Specifications.. The staff has taken the position that TS are required for SB0 res ponse equipment. - However, the question of how specificati_ons for--tie SB0 equipment will be applied is currently being considered generically by the NRC in-the context of the' Technical Specification improvement-Program and remains an open item at this time. 'In

' s the interim,- the staff expects: plant procedures to reflect the appropriate testing and surveillance requirements to ensure the operability of the necessary-SB0 equipr.ient, ilf the staff later determines that TS regarding the 580 equipment is war, anted, licensees will be notified of the implementation requirements.

The reporting requirements contained in this letter affect fewer than ten respondents:--therefore, DMB clearance.is not required under Public Law 96-511.

Sincerely, Original Signed By ThomasA. Bergman,Proje}c/ Manager Project Directorate IV'?

- Division of Reactor Projects lll/IV/V Office of Nuclear Reactor Regulation -

Enclosure:

Q111RJBUT103:

Safety Evaluation-Docket File EPeyton NRC/PDR

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Local.PDR

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PDIV-2-Reading File EJordan-

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II Mr. William J. Cahill, Jr.

• cc w/ enclosure:

Senior Resident inspector Jack R. Newman, Esq.

U.S. - Nuclear Regulatory Commission Newman & Holtzinger P. 0._ Box 1029 16.5 L Street, N.W.

G-anbury, lexas-76048 Suite 1000 Washington, D. C.

20036 Regional Administrator, Region IV U.S. Nuclear Regulatory Commission Chief, Texas Bureau of Radiation Control 611 Ryan Plaza Drive, Suite 1000 Texas Department of Health Arlington, Texas -76011 1100 West 49th Street Austin, Texas 78756 Mrs. Juanita Ellis, President Citizens Association for Sound Energy Honorable Dale McPherson 1426 South Polk

. County Judge Dallas, Texas 75224

'P. O. Box 851 Glen Rose, Texas 76043 Owen L. Thero, President Quality Technology Company Lakeview Mobile Home Park, Lot 35 4793 East Loop 820 South fort Worth, Texas 76119 Mr. Roger D, Walker Manager, Nuclear Licensing Texas Utilities-Electric Company 400 North Olive-Street, L.B. 81

-Dallas, Texas 75201.

Texas Utilities Electric Company c/o Bethesda Licensing

- 3 Metro Center, Suite 610 Bethesda,-Maryland 20814

. William A. Burchette, Esq.

Counsel for Tex-La Ele:tric Cooperative of Texas Jorden, Schulte, & Burchette 1025_Themas Jefferson Street, N.W.

Washington, D.C.

20007 GDS Associates, Inc.

Suite 720.

1850 Parkway P1 ace-Marietta, Georgia 20067-8237

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UNITED STATES

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NUCLE AR REGULATORY COMMISSION

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_t W ASHINGTON. O C. 20555 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR PEGULATION STATION BLACKOUT PULE (10 CFR 50.63)

TEXAS UTILITIES ELECTRIC COMPANY, ET AL.

COMANCHE, PEAK STEAM ELECTRIC STATION, UNIT 1 DOCLET NO. 50-445 1.0 INTRCDUCfl0N On July 21, 1988, the Code of Federal Regulations (CFR),10 CFR Part 50, was amended to include a new Section 50.03 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 a spe ified duration. The SB0 Rule also requires licensees to submit information as defined in 10 CFR 50.63 and to provide a plan and schedule for confomance to the 560 Rule. The SB0 Rule further requires that the t,aseline assumptions, analyses, and related information be available for hRC review. Guidance for conformance to the SB0 Rule is provided by:

(1) Regulatory Guide (RG) 1.155, *St' tion Blackout," (2) the Nuclear Managenent and Resources Council, Inc.,

1. ARC) 87-00, " Guidelines and Techrical Bases for NUMARC Initiatives

.essing Station Blackout at Light Water Reactors," and (3) NUMARC 87-00, '. pplemental Questions / Answers and Major Assumptions,' dated December 27,

'9, (issued to the industry by NUMARC on January 4, 1590).

To facilitate the NRC staff's (hereafter referstd to as staff) 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 fomats prcvide the staff with a sumary of the results from the licensee's analysis of the plant's SB0 coping capability.

The licensees are expected to verify the accuracy of the results and maintain documentation that supports the stated re sults.

Compliance to the SB0 Rule is verified by a review of the licensee's submittal, an audit review of the supporting documentation as deemed necessary, and possible followup NRC inspections to ensure that the licensee has i@leinented the appropriate hardware and/or procedure nKrjifications that will be required to comply with the SB0 Rule, s.

The licensee's respctses to the SB0 Rule were provided by letters from W. J.

Cahill, Jr. on hovember S.1990, and hovember 22, 1901, to the U.S. Nuclear Regulatory Conrnission Docurent Control Desk. Also, there was a teleconference between representatives of the licensee and thr NRC staf f or November 1,1991.

Corporation (SAIC)ponses were reviewed by Science Applications International The lics.nsee's res urder contract to the NkC. The results of the review are docunented by an $A!C Technical [ valuation Report (TER) SAIC-91/1603, " Comanche Pest Steam Electric Station, Unit 1, Station Blackout Evaluation," (Attachment).

C.0 CVALVATION Af ter reviewing the licersee's submittals and the SAIC 1ER the staf f concurs with the SAIC an61 ses and conclusions as identifieu in the SAIC TER (refer to 7

th,ttachmeht for details). The staff findings and recorrendations are surrist izee as follows:

2.1, Station Blackout Duration The licerisee has calculated a mint.num acceptable 580 duration of 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> based on a plant of fsite AC power design characteristic Group "Pl." an emergency AC (CAC) power configuration Group "C," and a target Emergency Diesel Generator (EDG) reliability of 0.95. The licensee confirmed that the AC power design characteristic Group is "Pl."

The Group "C" EAC configuration is based on two EDUs per i;1t. One UC powcr supply per unit is required to oparate safe s

shutdown equipment fellowing a loss of offsite power.

The *arget EDG reliability was based on Comanche Peak Steam Electric Stetion (CPSES), Unit 1 having an avez age erg reliability greater than 0.90 and 0.94 over the last 20 and 50 demands. Usf 19 this hta, the target EDG reliability (0.95) selected by l

the licenset is appropriate and meets the criteria specified in RG 1.155 and WUMARC 87-00. However, the licensee r,hould also include the EDG reliability calculations for the last 100 demands, provided the EDGs have experienced 100 demands. This documentation should be retained by the licensee in support of the 500 sobrittals. The "P1" grouping is based en an independence of offsite power clar.sification of Group "I 1/2,* a severe weather (SW) classification of Group "1," and an extremely severe weather (ESW) classification of Groap "1."

Af ter reviewing the available information in the licensee's submittals, RG 1.155, NtMARC 87-00, and SAIC's TER, the staff agrees with the licensee's j

evt.1cLtion of a 4-hour 580 coping duration, j

2.2 Station, Blackout Copinu, Capability l-The characteristics of the following plant systems and compownts were reviewed to assae that the systems nave the availability, adequacy, and capability to l

achieve and maintain a safe shutdown and to recover from an SB0 for a 4 hour4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> I

coping duration.

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?.2.1 Condensato invent ry ror Decey Ptat Retoval The licensee stated tht tw d on a plant-specific analysis. FJ7,200 gallant of wa+er would be required ior cooldown, decay heet reroval and restoring the steem generator le.(15 during a 4-hour 590 event. The Ccc.anche Peak Technical Specifications ('S) reovirt a mini:num aermissible condensate storage tank level of 78?,540 gallons of wa*.er whica exceeds the quantity required for coping with a 4-hour $80 event.

?o nd cn its review, the staff concludes that the licensee will have sufficient redensatt. inventory to cope with a 4-hour SB0 event at the Comanche Peak pirnt.

2.1.? Class IE Battery capacity The licensee stated that a battery capacity calculation has been perfond

>ursuant to Section 7.2.2 of NUMARC 87-00 te verify that the Class IE batteries nave sufficient capacity te supply the conr.ected loads continuously during a 4-hour 500 event. The licensee states that this calculetien took no credit for load sheddine and was perfomed in accordance vith IEEE-485.

In its HVAC calculation for the battery room, the licensee calculated a minin.um battery roor temperature of 67'F. The licensee performed a battery sizing calculatien that assured an electrolyte temperatero of 65F and concluded that, even the hetviest loaded battery would nave sufficient without load shedding, load for a 4-hour period and provide suffit.ient DC power capacity to carry its for EDG field flashint.

During the November 1,1991, teiephoae conference, the licensee stcted the follcwing:

A temperaturc cerrection factor of 1.08 based on a minimum expected electrolyte temperature of 65'F was used.

A 25 percent aging factor was used.

A design margin of 25 percent to 35 percent was used for all batteries.

No load shedding was considered.

The DC powered ventilation fans for the inverter rooms (proposed SB0 modification) will not be loaded frca Class 1E buses. The licensee intends to use either the existing non Class 1E batteries or install a new battery to support this load.

The Class 1E battery loads in the FSAR bound the SB0 loads.

Ito licensee further states that the SEO battery load was bounded by the FSAR load, and that each Class 1E 125 VDC system has the capacity to continuously supply all essential loads for a period of 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />.

The staff agrees with the licensee that the Class 1E battery capacity is adequate to supply the required SB0 loads for a 4-hour event.

. 2.2.3 CoLpressed Air The licensee stated that air operated valves relied ur;n to cope with an SB0 for 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> can either be aperated unually or have sufficient backup sources independent of the preferred Class IE power supply.

Based on its review, the staff concludes that the licensee has provided cdequate assurance that air operated valves relied upon to ccpe with an SEO of 4-hours duration either have Sufficient backup sources or can be operated manually.

2.2.4 Effects of Loss of Ventilation Thelicenseehasidentifiedthedominantareasofconcern(DACs)atthe Comanche peak plant (see SAIC TER for the list of DACs and their associated calculated temperatures) and performed plant-specific analyses in accordance witn the guidance described it. NUMARC 87-00 to determine the effects of loss of ventilation in these OACs during a 4-hour SB0 event. The licensee concluded that, with the exception of the ventilation fans to be instelled to the uninterruptable power supply (UpS) inverter rooms, no plant modification or procedure change is required to provide reasonable assurance for equipment operability in these D8.C5.

The staff's evaluation of the effects of loss of ventilation in each of these areas is provided below.

l 2.2.4.1 Control Room. Electrical Equipment Areas. Containtent Ground Floor Valve-Rooms, Pressurizer Compartment. Main Steam g

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FenHration Area. Main SteamTenetration Platform,and Turbine-briven AFW Pump Room The licensee provided the calculated peak temperatures during a 4-hour SB0 event in the above areas (see SAIC TER). However, with respect to the temperature transient analyses, the licensee has not provided the detailed information for the **aff to review, therefore, the staff has not been able to l

conclude that the calculated peak tempetatures in these areas are acceptable.

Recomenda tion: The licensee should document all of the input parametars Ti.e., equipGnt heat loads, personnel heat loads, thermal conductivity for structures, room free air volumes, initial temperatures, etc.) 6nd provide the justification for each of these input parameters used in the temperature transient analyses. The licensee should arovide input parameters and justifi-l cations to the NRC staff for review for tie control room analysis. The input parar.eters and justification for the other rooms should be included with the documentation that is to be maintained by the licensee in support of the SB0 tubmittals.

2.2.4.2 UpS and Distribution Rooms l

With an assumption of 104'F for the initial room temperature, the licensee l

calculated a peak temperature of approximately 154.5'T for the U/S ano distribution rooms. The licensee stated that since operability of the 1

inverters located in these rooms cannot be assured at tht; maximum temperatures expected during a station blackout, a hardware modification is planned to reduce these temperatures. The modification will install DC-powered ventilation fans that will supply a sufficient capacity of outside air to the UpS rooms to maintain the room temperatures below the temperature at which inverter operability can be assured.

If necessary, this modification will also include the installation of additional battery capacity.

Based on its review, the staff finds the above cited inodification acceptable.

However, the licensee needs to reevaluate the temperature rise calculations for these rooms taking into account the installation of the DC powered ventilation fans.

Recomendation: The licensee should reevaluate the temperature rise calculations for the UPS and distribu' tion rooms taking into accouat the installation of the DC powered ventilation fans and verify that the maximur temperatures expected during a 4-hour SB0 event are lower than the temprature limit for the operability of the inverters.

2.2.4.3 Containnent The Comanche peak plant containment is a typical large dry containment.

Basco on its review of similar larp dry containments designed for Westinghouse reactors, the staff concludes that the loss-of-coolant accident / main steam line break (LOCA/MSLB) temperature profile at the Comanche peak plant will bound the temperature profile resulting from a 4 hour4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> SB0 event.

2.2.5 Containnent Isolation The licensee states that tha >1antlistofcontainmentisolationvalves(CIVs) has beth reviewed to verify t1at valves which must be capable of being closed of that must be operated under station blackout conditions can be positioned with indication independent of the preferred and blacked-out unit's Class lE power supplies. The licensee further states that no plant modifications and associated procedure changes are required.

Based on its review, the staff concludes that the containinent isolation valve design and operation at the Comanche Peak plant have met the intent of the guidance described in RG 1.155 and are, therefore, acceptable.

2.2.6 Reactor Coolant Inventory The licersee stated thet the ability to maintain adequate reactor coolant system (RCS) inventory to ensure that the core is cooled has been assessed for 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />. A plant-specific analysis was useri for this assessment. The licensee stated that the expected rates of reactor coolant inventory loss under SB0 conditions do not result in core uncovery.

Therefore, RCS makeup systems under SB0 conditions are not required to maintain core cooling under natural circulation conditions.

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i 6-1.xpected neximum losses from the RCS are 25 gpm from each of the four RCS pumas at 'dSO psia and 12 gpm allowed by the TS for a total of 112 gpm f or r

L each unit.

It was assured that the reactor was not depressurized below the accumulator infection pressure of 785 psi..The licentee concluded that the i

core.would remain covered in excess of 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />. Based on the above perameters, in the the staff's consultant calculated that the volume of water remaining's core at the end of a 4. hour SB0 would be 6313 cubic feet.

The staff consultant concluded, based on expericr.ce with similar 4-loop Westinghouse pressurized water ree : tors (NRs), that the core would not be uncovered during

'd 4 hour4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> $BO event. Thereiere, the staff considers that there Is reasorable assurance th6t the. reactor coolant inventory will be adequate during a 4-hour

. SBO.

t The reacter coolant inventory evaluatio$ as described atove was based on the-I guidance provided in NVSARC 87-00 of 25 gpm per reactor coolent pump (PCP) staff per61ng resolution of Generic Issut (GI)greea to between NOHARC ano seel leakage for PkRs. The 25 gpm value was a 23.

If the final resolution of

- Gl43 definen higher RCP leakage rates than assuned for this evaluation, the.

licendee should:te aware of the potential impact of this resolution on their analyses and-actions addressing conformance to the SP0 Pule.

. 2.3, propnsed Procedures and Training The -licensee stated that plant procedures have been reviewed and that changes necessary to meet the guioellnes in NUMARC 87-00 Section a, will be 1

implemented in thc following areas:

- Station tlackout response - Procedure ECA-0.0A, ioss of All AC Power" AC power restcration - Procedure ECA-0.0A, "Less of All AC Power" Severe weather - Procedure ABN-907A, " Acts of Nature

• The licensee also stated that procedure changes associated with its proposed u

~ modification in the UPS inverter room will be identified, developed, and implehented coincident with the installation of the modification. The staf f did not review the procedures or proposed procedure modifications. The staff expects the licensee to;1giement and maintain these procederes including any _

ot1ers that may be required to ensure an appropriate response to an SB0 event.

Although personnel training requirements for an 5B0 response were not specifically addressed by the licensee's submittel, the staff expects the licensee to implement the appropriate training to ensure an effective response to:an'$B0 event.

2.4 Peposed Vodification The licensee states that. based on the HVAC analysis, the operability of the_ UPS inverters (in rooms 119 and 121) could not be tssured at the maximtsn temperatures expected during an SBO. As a result, a hardware modification-is planned to reduce these temperaturas.

DC-powered ventilation fans will be E

installed to supply a sufficient capacity of cutside air to the UPS rcoms to maintain tne room temperatures below the temperature at which inverter operability can be aswred.

During the telephone conference on November 1, L

. 1991, with the staf f, the licensee stated that this additional capacity would l,

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not ccme from the cristing Class 1E batteries.

If necessary, this modification will incluoe the installation of additional battery capacity.

Tbc new ventilation fars will draw prgwer from either the existing non-Class IE hatteries or frcr a new dedicated battery. The lictnsee stated that the UDS tootus hardware trodificatient are planned for a refueling outage at least 120 days af ter receipt of the hRC Safety Evaluation Report, lhe staff finds the litersee's proposed trodifications to be acceptable provided they are properly implemented.

Recomenda tico: The licensee should include e full description, including the ricture and objectists of the proposed nodifications idtntified above, in the documentatier. trat is to be maintained by the 11cersce in support of the Sb0 subaittals.

2.5 Ovality Assurance and Technica'l Sr4cifications The licensee stated that all equipr.cnt required to cope with er 580 is sefety-related and included in Jthe plant's OA prograr, pursuant to 10 f rR 50, Apperdin U, except for the turbine stop valves.

The licensee states that in the 500 scenario, the turbine stop valves are relied upon for irrediate steen isolatier.. These valves are non-raiety related, but are surveilled and maintained p'er plant Technical Specification 3/4.3.4, " Turbine Overspeed Protection.

The licensee did not specifica11) address Ouality Assurance (@) programs or TS for the SB0 equipment. The TS for the SB0 equipment are currently being considered generi: ally by the NRC in the context of the Technical Specifica-tions Improvement Program and remains an open item at this time.

However, the staff expects plant procedures to reflect the apprcpriate testing and surve114nce requirerents to ensure the operability of the necessary SB0 equipN nt.

If the staff later detemines that TS regarding the WO equipment h warranted, the licensee will be notified of the implemer.tation requirerents.

Recomendation: The licensee should verify and confim that the ventilation Tans and the additional batteries, if required, as discur, sed in Section P.4, are covered by their QA progrcm consistent with the guidance of Appe:. dix A, RG 1.155. Verification that such a program is in picce should be included as part of the docmentation supporting the SB0 Rule responses.

2.6 EDG Reliability p rogram The licensee stated that Comanche Peak Unit 1 is committed to Safety Guide 9 (3/10/'/1) and the TransAmerica Delaval, Inc., EDG Reliability Program.

The n

if censee further states that they will reevaluate this program upon resolution of Generic issue B-56, " Emergency Diesel Generator Reliability," end issuance of Regulatory Guide 1.9, Revision 3. " Selection, Design, Qualification,.

Testing, and Reliebility of Dfesel Generator Units Uted as Onsite Ele:trical Power Systems a t fluclear Power Plants," consistent with the reporting requi*enents of Regulatory Guide 1.9.

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.I h correndation:

% licensee should provide confirmation and include in the documentation 5.upforting the SB0 slinittals that a program meetirg as a mininn the guidance of RG 1.155, 0 sition 1.2, is in place or will be implerented.

0 2.7 Store cf Staf _' Revity The $80 Rule (10 CFR 50.63) rtquires licensees to subn.it a resper.se containing sp6cifically defit t d information.

It also requires utilities "...to have

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baselitie assurptkns, atialyses, and related infomation used in their :oping evaluations avv.lable for NRC review. The staf f and its contrarter (SAIC) cid not perform a deteiled review of tht proposed hardwr.re and procedural modifintions which are scheuuled for later implementetion.

However, based on our review of the licenset's supporting docunentation, we have identified the following areas for focus in any followpp itspection or essesscent that may be undertaltr ty the NRC to verify contortrance with the SB0 Rule. Additional r

iterus vay be added es a result of the staf f review of the actions talen by the j

lictr,ste in response to this SE.

a.

Hardware and procedural modifications, b.

5B0 rocedures in accordance with Ff 1.155, Position 3.4, and NWARC 07-00, tection 4, c.

Operator staf fir:t end training to f ollow the identified actions in the SED procedure, d.

EDG reliability program meets, as a mininum, the guic'elines of RG 1.155, e,

facipent end componects required to core with an SB0 are incorporated in a OA prograu that meets the guidance of RG 1.155, Appendix A, and f.

Actions taken pertaining to the specific reconr.endation; noted above in the SE.

3.0

SUMMARY

AND CONCt.USION The staff has reviewed tht. licensee's responses to the SB0 Rule (10 CFR 50.63) ar.d the TER prepared by the staff's cor sultant, SAIC. Based on our review, several confirmations and ccrNnitrents need to be made af described in the recomendations itemized herein. These include the provision of detailed infermation regarding the temperatum transient analyses for the Control Room and other equipment areas identified in Section 2.2.4.1 for staff review, reevaluation of temperature rise calculations end equipment operability for the UPS and distribution rooms, description of the proposed modifications, and vort-fication of a QA program for the proposed ventilation fans arti battery associ-ated with UPS and Distribution Rooms consistent with RG 1.155, Appandix A, and an EDG relitt.ility program that neets, as a minimurr, the guidelines of PG 1.155, Section 1.2.

The licensee should incivde the documentation associato! with the above actions and verifications *rith the other documentation supporting the SB0

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9

$bbmittal, ar.d naintain this documentation f or further inspection and assessment as ray be undertuken by the imC to further verify conformance with the 5B0 Rule.

Based on cur review of the submittals. We find the lice:nsee's responses and proposed rethod of dealing with an 500 to be incomplete and the staf f cannot assest confortance with the 580 Rule.

The licensee should provide for staff review the input p. 4cters used in the temperature transient analyses (see Suction 2.I.4.1 cf this SE) and provide justification for each of these input paraneters. The licensee should also continn within 60 days that the recorra rdations identified within this SE will be implemented. Upon receipt of the infunnation and confirn.ations, the staff will provide its assessment cn Comanche Peak's confonnancc to the SB0 Rule. The schedule for impicmentation sbculd also be provided in accordance with 10 CFR 50.63(c)(4).

Attachnent:

SAIC.91/1803, technical Evaluation Report, Comanche Peak Steam Electric Station, Unit 1, Station Bleckout Evaluation Dett: February 27, 1992 P

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SAIC-91/1803 I

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i TECHNICAL EVALUATION REPORT i

COMANCIIB PEAK STEAM ELECTRIC STATION l

UNIT I

,i STATION BLACKOUT EVALUATION

?

TAC No. 68530-SAIE' Science AppIlcationsInternstlanalCorporation l

An Ernobyee Owned L,owny L

Tinal December 13,1991 Prepared fon U.S. Nuclear RMgulatory Commission Washington, D,C,20555 Contract NR ' 03-87-029

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Task Order No.116

.ye

-p30 oj (p..

Post Ottee Box 1303,1710 Goodidge Ortve. M-sean, Vrginia 22102 (703) 871400

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TABLE OF CONTENTS Section Eiss 1.0 D A C KG R OUN D....................................................................... 1 2.0 RE V I EW P ROC ESS................................................................ 3 3.0 E V A LU ATI ON...................................................................... -. 5 3.1 Proposed Station Blackout Duration......................... 5 3.2 Station Blackout Coping Capability.......................... 8 3.3 Proposed Procedt'.res and Tr aining............................ 21 3.4 Proposed M odifica tions.............................................. 21 3.5 Quality Assurance and Technical Specifications..... 22 4.0 C ON C LU SI ON S.......................................................................... 23 5.0 RF FE R EN C ES............................................................................ 2 6 4

-__.__-------_.-_-_m_

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Th( MNICAL EVALUATION REPORT COM ANCHE PEAK STEAh! ELECTRIC STATION UNIT 1 STATION BLACKOUT EVALUATION

1.0 BACKGROUND

On July 21,1988, the Nuclear Regulatory Commission (NRC) amended its regulations in 10 CFR l' art 50 by adding a new section,50.63, " Loss of All Alternating Current Power" (1). The objective of this requirement is to assure that all nuclear power plants are capable of withstandin5 a station blackout (SBO) -nd maintaining adequate reactor core cooling and appropriate containment integrity for a required duration. This requirement is bitsed on information developed under the commission study of Unresolved Safety Issue A-44, " Station Blackout" (2-6).

The staff issued Regulatury 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 ar.d Technical Basis for NUMARC Initiatives Addressing Station Blackout at Light Water Reactorr," MUMARC 87 00 (8). This document provides detailed guidelines and procedures on how to assess each plant's capabilities to comply with the SBO

. 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 SBO duration capability from two to sixteen hours depending on the plant's charreteristics and L

vulnerabilities to the risk from station blackout. The plant's characteristics affecting L

the required coping capability are: the redundancy of the onsite emergency AC power sources, the reliability of onsite emergency power sources, the frequency of Inss of offsite power (I.OOP), and the probable time to restore offshe power.

In order to achieve a consistent systematic responva from licensees to the SBO rule and to expedite the staff review process, NUMARC developed two generic L

1.

I 4

response documents. These documents were re. viewed and endorsed (10) by the NRC staff 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 SBO rule requirements i:: verified by review and evehation of the licensee's submittal and audit review of the supporting documents.c necessary. Follow up NRC inspections assure that the licensee has implemented the necessary changes as required to meet the SBO 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 pneric question regarding the degree of licensees' cor formance to the requirements of the SBO rule. To resolve this question, on January 4,1990, NUMARC issued additional guidance as NUMARC 87-00 Supplemental Questions / Answers (11) addressing the NFC3 concerns regarding the deficiencies. NUMARC requested that the licensees send their supplemental responses to the NRC addressing these concerns by March 30, 1990.

2

l 2.0 REVIEW PROCESS The review of the licensee's submittal is focused on the following areas consistent with the positions of RG 1.155:

A.

Minimum acceptable SBO duration (Section 3.1)

B.

SBO ropfng capability (Section 3.2),

C.

Procedures and training for SBO (Section 3.4),

D.

Proposed modificat.ans (Section 3.3), and E.

Quality assurance and technical specifications for SBO equipment (Section 3.5).

For the determination of the proposed minimtun acceptable SBO duration, the folicwing factors in the licensee's submittal are reviewed: a) offsite power design characteristics, b) emerge.tcy AC power system configuration, c) determination of the emergency diesel generator (Etd) reliability consistent with NSAC-108 criteria (9), and d) determination of the accepted EDG target reliability.

Once these factors 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 SBO coping capability, the licensee's submittal is reviewed to asess the availability, adequacy and capability of the plant systems and compor w needed to achieve and maintain a safe shutdown condition and recover fro... an SBO of acceptable duratien which is determined above. The review process follows the guidelines given in RG 1.155, Section 3.2, to assure:

availability of sufficient condensate inventory for decay heat removal, a.

b.

adequacy of the Class-1E battery capacity to support safe shutdown, 3

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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 tne plant, e

ability tc provide appropriate containnient integrity, and c.

f.

ability of the plant to mrJntain adequate reactor coolant system inventory to ensure core cooling for the required coping du' ration.

The licensee's submittal is reviewed to verify that required procedure.s (i.e.,

revised existing and new) for ec, ping with SBO are identified and that appropriate operator training will be provided.

The licensee's :ubmittal for any proposed modifications to emergency AC sources, battery capacity, condensate capacity, compresseo air capacity, ventilation system for equipment operab!!ity, containment isolation valves for providing appropriate containment integrity and primary coolant make-up capability is reviewed. Technical specifications and quality assurante set forth by the licensee to ensure high reliability of the equipment, specifically added or assigner' va meet the requirements of the SBO rule, are assessed for their adequacy.

This preliminary SBO evaluation is based upon the review of the licensee's submittal dated November 5,1990 (13), the licensee's written response (la) to questions discussed during the November 1.1991 telephone conference, and the information available in the plant Final Safety Analysis Report (FSAR) (12);it does not include a concurrent site audit review of the supporting documentation. Such an audit may be warranted as an additional coniirmatory action. This determination would be made and the audit would be scheduled and performed by the NRC staff at some later date.

l

l 3.0 EVALUATION 3.1 Proposed Station Blackout Duration Licensee's Submittal The licensee, Texss Utilities (TU) Electric Company, calculated (13) a minimum acceptable station blackout duration of four hours for the Comanche Peak Steam Electric Station (CPSES) Unit 1 site. The licensee stated that no modifications are required to attain this coping duration.

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

1.

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

a.

Iridependence of the plant effsite power system chau.cteristics of "A /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 "1," and d.

Estimated frequency of LOOPS due to severe weather (SW) which places the plant in SW Group "1."

2.

Emergency AC EAC) Power Configuration Group i

The EAC power configuration of the plant is "C." CTSES is equipped l

with two emergency diesel generators per unit. One EAC power supply per unit is necessary to operate safe-shutdown equipment fellowing a lots of offsite power.

L 5

3.

Target Emergency Diesel Generator (EDG) Reliability The licensee has selected target EDG teliability of 0.95 for the CPSES EDCs. This target reliability was selected based on having a unit average EDG reliability for the last 20 demands greater than 0.90, and for the last 50 demands greater than 0.94.

Review of Licensee's Submittal Factors which affect the estimation of the SBO coping duration are: the estimated frequency of LOOPS due to ESW and SW conditions, the independence of the offsite power system groupirg, the expected frequency of grid related LOOPS, the class!fication 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 places the CPSES site in ESW Group "1," which is in agreement with what was stated in the licensee's submittal (13).

Using data from Table 3 3 c - NUMARC 87-00, the expected frequency of LOOPS due to SW conditions place the CNES site in SW Gmup "1," which is in agreement with what was stated in the licensee's submittal (13). This calculation was performed with the condition that there are multiple rights of way among the incoming transmission lines, consistent with information provided in the FSAR (12).

The licensee stated that the independence of the plant offsite power system grouping is "I1/2." A review of the CPSES FSAR (12) shows that:

i Th as 345 kV and 138 kV switchyards that are physically and electrically independent; l

2.

During normal operation,345-kV power is provided to the CPSES Unit 1 j

emergency bu.;es from the 345 kV switchyard and the Startup i

transformer (SUT), XST2; 6

/

3.

In the event that the Unit 1 SUT becomes uaavailable to its normally fed Class 1E buses, power is made available from the Unit 2 SUT (XSTT) by an comatic transfer. According to the FGAR '12), each SUT bas the capacity to carry the required Class 1E loads for both unita during all modes of operation.

Based on the above and the criteria stated in Table 5 of RG 1.155,;he plant independence of offsite power system group is classified as "12 "

Establishment of the proper Emergency AC (EAC) Configuration Group is based on the number of available EAC sources and the number of EAC sources required to operate safe shutdown equipment following a LOOP.

Each unit has two dedicated EAC sources, one of which is required after a

. LOOP. We agree with the licensee's assessment which places the plant in E AC Group "C."

The licensee selected (13) the EDG target reliability of 0.95 based upon having an everage reliability for the last 20 demands greater than 0.90 and for the last 50 demands greatter than 0.94. Althcugh this is an acceptable criterion for choosing an EDG target reliability, the guidance of RG 1.155 requhes that the EDG e,tatistics for the last 100 demands also be calculated. Without this i

infermatian, we are unable to adequately judge how well the RDGs have performed in the past and if there chould be 4my concern. We are unable to verify the demonstrated start and load run reliability of the plant EDGs. This Information is only available onsitt as part of the submittal's supporting documents Reliabihty data from NSAC 108 was not available in this cas.3, as L

CPSES Unit I was not licensed until August,1990 and NSAC-108 covers the years 1983-1985. Nevertheless, the licensee needs to here an analysis showing the EDG reliability statistics for the last 20,50 and 100 demands in its SBO submittal suppcrting documents, L

The licensee stated (13) that TU Electric ir committed to Safety Guide 9 (3/10/71) and the TransAmerica DeLaval, L.:., EDG Rollability Program. The

'lleensee stated that it will reevaluate this program upon resolution of Generic Issue B-56, " Emergency Diesel Generator Reliability," and the issuance of Regulatory Guide 1,9, Revision 3, " Selection, Design, Qualification, Testing, 7

and Reliability of Diesel Generator Units Used as Onsite Electrical Power Systems at Nuclear Power Plants," consistent with the reporting requirement 3 of Regulatory Guide 1.9.

i 1

With regard to the expected frequency of grid related LOOPS at the site, we can l

not confirm the stated results. The historical data with regard to 1.OOP events in the U.S. contained in NUREG/CR-3992 (3) is not applicable to CPSES, as it only covers the years 19731980. In the absence of any adverse information, we agree with the licensee's statement.

Based on the above, we agree with the licensee's claim that the offsite power design characteristic of the CPSES Unit I site is "P1" with a minimum required SBO coping duration of four hours.

3.2 Sta!'on Blackout Coping Capability The plant coping capability with an SBO event for a required duration of four hours is assessed with the following results:

1.

Condensate Inventory for Decay Heat Removal Licensee's Submittal The licensee stated (13) that a site-specific calculation determined that 187,200 g ~.lons of water would be required to cooldown the reactor 4

coolant system, remove decay heat, and restore steam generator levels during a four hour SBO event. The licensee stated (13) that the minimum permissible condensate storage tank (CST) level per technical specifications provides 282,540 gallons of water, which exceeds the quantity required for coping with a four hour SBO event.

Review of Licensee's Submittal Using the expression provided in NUMARC 87-00, we estimated that 75,451 gallons of water would be required to remove decay heat during a four-hour SBO ovent, assuming that no primary system cooldown is 8

attempted. This estimate is based on the maximum licensed core thermal rating of 3411 MWt listed in the CPSES FSAR (12). Tlw 4

licensee stated that it has considered the effect of RCS cooldown and steam generator blowdown in its calculation. We didn't repeat the licen>ee's calculations, llowever, based on our experience whh similar PWRs we concur with the licensee that, based on a minimum condensate level of 282,540 gallons, the site has sufficient condensate to cope with a four hour SBO event.

2.

Class 1E Battery Capaelty Licensee's Submittal The licensee stated (13) that a battery captcity calculation has been performed pursuant to Section 7.2.2 of NUMARC 67-00 to verify that the Class 1E batteries have sufficient capacity to supply the connected loads continuously during a for hour SBO event. This calculation took no credit for load shedding and was performed in accordance with IEEE Std 485. In its HVAC calculation for the battery room the licensee calculated a minimum battery room te'mjierature of 67'F. The licensee performed a battery sizing calculation that assumed an electrolyte temperature of 65'F and concluded (13) that, even without load shedding, the heaviest loaded battery has sufficient capacity'tc, carry its load for a four hour period and provide sufficient DC power for Diesel Generator field flashing.

l In response to questions raised at the November 1,1991 telephone conference, the licensee stated (14) the following assumptions used in the battery capacity calculation:

• A temperature correction factor of 1.08 based on a minimum l

expected electrolyte temperature of 65'F was used;

• A 25% aging factor was used; 1

1

• A design margin of 25% to 35% was used for all batteries; i

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• No load shedding was considered:

• The DC pow;ed ventilation fans for the inverter rooms (proposed SBO modificat'on) will not be loaded from the Class 1E buses. The licensee inten Js to use either the existing non Class 1E batteries or it will install a new battery to support this load.

• The Class 1E battery loads in the FSAR bound the SBO loads.

Review of Licensee's Submittal The licensee's battery calculations were neither received nor reviewed.

Using an aging factor of 1.25 e.nd temperature correction factor of 1.08, the licensee stated that a design margin o! 25% to 35% exists for each Class 1E battery during a four hour SBO event. The licensee further stated that the SBO battery load was bounded by the FSAR load. The CPSES FSAR states (12) that each Class 1E 125 VDC system has the capacity to continuously supply all essentialloads for a period of four hours. Since the SBO battery load will be smaller than the design basis load considered in the FSAR, we agree with the licensee assertion that the existing Class 1E battery capacity is adequate to supply the required SBO loads for four hours.

3.

Compressed Air Licensce's Submittal The licensee stated (13) that air-operated valves relied upon to cope with an SBO for four hours can either be operated manually or have sufficient backup sources independent of the preferred and Class 1E power supply.

With regard to AFW flow control, the licensee stated (13) that the ARV throttling valves have accumulators which are sized for 30 minutes of operation. ECA 0.0A specifically cautions the operators about this 10

l limitation, and identifies the valves which operators must locally operate to throttle ARY flow after the air accumulators ere depleted.

These valves are located in the ARV pump room which is calculated to reach a maximum temperature of 131.1*F during an SBO. During the telephone conference on November 1,1991, the licensee stated that although the capability exists to control ARV flow from the control room,it intends to follow the guidelines of ECA 0.0A, The licensee stated that it considers 30 minutes to be sufficient for starting the ARY pump and providing flow to a steam generator, and that aiter 30 minutes only intermittent operator mamtal actions are required.

Further, the licensee stated (14) the following: accessibility and habitability of the ARV pump room were evaluated based on the expected ambient temperature conditions, adequate communications equipment exists in the form of portable radio communications (walkie-talkies), and adequate lighting in the area is provided by Fire Safe Shutdown battery powered lights with capacity in excess of the A

four hour coping analysis requirement.

With regard to steam relief to the atmosphere, the licensee stated (13) that the atmospheric relief valves (ARVs) have accumulators which are of sufficient size to enable a controlled cooldown of the RCS from hot standby to hot shutdown over the four hour SBO period, in addition, during the telephone conference the licensx stated that the ARVs will be throttled from the control room during an SBO event and that contingencies exist to operate the ARVs locally,if required.

Review of Licensee's Submittal Based on the information provided in the licensee's submittal and the licensee's response to questions raised during the November 1,1991 telephone conference, we conclude that the licensee has provided adequate assurance that all air operated valves relied upon to cope with an SBO of four hours duration have sufficient backup sources and can be operated in a manner that is consistent with the guidance.

11 I

_ _ _ _ _ _ _ _ _ _ _ _ ~

4.

Effects of I.oss of Ventilation Licensee's Submittal The licensee stated (13) that as part of its HVAC analysis, all of the areas containing SBO equipment required to cops with an SBO are considered to be dominant areas of concern (DACs), and that all of the equipment has been evaluated for optrability in accordance with NUMARC 87-00 guidelines.

CPSES-specific calculations identified the following areas as DACs:

Area / Room Mar. SBO Number Description Temp PD 119 UPS & Distribution Room Train B 154.6 121 UPS & Distribuhon Room Train A 154.5 154 Containment Gmund Door 150 4 155 Valve Room 1504 161A Prenurirer Comtattment 150.4 23 Valve Room 150.4 108 Main Stearn Penetration Area 141.6 109 Main Steam Penetration Platform 141.6 74 Turbine-Driven AFW Pump Room 131.1 83 E ectric Equipment Area 120.7 135 Controf Room 1203 The licensee stated (14) that the Systerns Improved Numerical Differencing Analyzer (SINDA) computer code was used for all of its room analyses, except for containment where CONTEMPT LT26 was used. Both codes determine temperatures as a function of room volumes and how they interact with other rooms, concrete, metal and natural convection airflow. Analyses are organized by building / room and also take into account the affect of the temperature outdoors as it varies diurnally. Heat addition from electrical equipment, mechanical 12

ll equipment, piping and lighting where applicable, was considered and quantified for each room.

The licensee provided (14) a list of the major assumptions made in its heatup calculations. (In many cases there was no clear reference to which room (s) the assumption applied or how the calculation was carried out.) The licensee's assumptions are listed below:

AC powered electrical cables associated with the EDGs were considered to be energized. His is conservative since, during an SBO, these cables would not be energized.

Piping heat loads were based on the most conservative modes of operation such as LOCA in one unit with the other unit in cooldown. This is conservative since most of these heat sources (i.e.

residual heat removal, containment spray, component cooling water) would not be in operation during an SBO.

The maximum room design temperatures (104,120 and 122*F as stated in Table 9.4.2 of the FSAR) for CPSES were used as initial temperatures for all rooms except the control room. These initial temperatures are based on 110 F outside air and equipment operating prior to an SBO with an ultimate heat sink temperature of 102*F. Analyses showed that the peak temperatures occurred beyond the four hours assumed for the SBO event, except in the case of the UPS rooms.

With regard to the control room, the licensee assumed an initial temperature of 80*F (maximum normal temperature per FSAR Table 9.4.2), an outside temperatures of 193'F on the control room roof,125'F cn the south wall, and 120*F on the north wall.

The licensee assumea the surrounding concrete in the control room (including the ceiling) to be used as heat sinks. The licensee justified the use of the concrete ceiling as a heat sink by stating that there is a five inch " snake space" around the perimeter of the 13

-.-.~.- - -

ceiling and " egg crate" material over the horseshoe area. No credit was taken for the heat sink capacity of the massive metal seismic ceiling supports in the control rcom. No credit was taken for mechanical equiprntnt or piping heat in the control room.

Credit is taken for cipening ts and/or cabinets in the control room, battery charger and inverter rooms to initigate the effects of internal heating of electrical equipment. Procedure ABN 601,

" Response to a 138/346 kV System Malfunction," governs these actions.

Inverter efficiencies of 77% for the 7.5 KVA units and 85% for the 10 MVA units were assumed.

For the containment the licensee assumed an initial temperature of 120'F, a heat addition rate of 666 Bru/hr from piping and equipment and thermal conductivities of 26 UTU/hr ft *F for steel and 0.854 BTU /hr ft 'F far concrete. Decay heat rate and seal leakage were determined to be unnecessary based on a LOCA/MSLB temperature profile provided in the licensee's submittal.

In addition, the licensee provided (14) a tabular list of the material properties used as SINDA input.

The licensee has determined that the final calculated temperature of 120.5"F for the control room does not prevent the operators from performing necessary actions, nor does it affect the operability of control room equipment and instrumentation, l

j The licensee calculated (13) a minimum temperature for the battery L

room of 67'F. In its battery sizing calculation, the licensee conservatively assumed an electrolyte temperature of 65'F.

The licensee stated (13) that a Westinghouse calculation of the temperature response of a large dry containment like Comanche Peak's indicates that temperatures inside containment, resulting from the loss 14 l

l

of ventilation during an SBO, are enveloped by the loss-of coolant accident (LOCA) and high-energy line break (HELB) temperature profiles.

The licensee concluded (13) that no modification or associated procedure changes were Tequired to provide reasonable assurance of equipment operability for any of the equipment except the uninterruptable-power supply (UPS) inverters located in rooms 119 and 121. Since operation of the inverters cannot be essured at the maximum temperatures expected during an SBO, a hardware modification is planned to reduce these temperatures (see Section 3.4).

Review of Licensee's Submittal The licensee's calculations were neither received nor reviewed. The information provided by the licensee is inadequate to make a judgement on the accuracy of the calculated final temperatures. The licensee stated that it has assessed equipment operability at the reported final temperatures and has concludeddhat equipment operability would not be degraded in any of the rooms examined, with the exception of the UPS inverter rooms.

We have reviewed the information provided by the licensee and j

categorized our response according to the evel of information available with regard to the heatup calculation for each room. Our review will be divided into three parts. The first part provides a general comment with regard to one of the quantifying assumptions used by the licensee in all of its heatup calculations. The second part will address those areas where there is insufficient information for comment. The third part will individually address each area where the l

licensee has provided specific information with regard to its heatup

(_

calculations.

l 15

General Comment:

Throughout the calculations, the licensee assumes a concrete thermal conductivity of 0.854 and 0.92 (Bru/hr ft *F). These values have previously been considered too high and therefore non conservative for SBO analysis. A more appropriate and acceptable value of 0.7 needs to be used.

Areas with insufficisnUnformation to comment:

Assumi.sg that the calculated temperatures provided by the licensee I

conservatively represent the room conditions auring an SBO and taking into account the licensee's assessment of equipment operability at the calculated temperatures, we consider the licensee's analysis to conform with the SBO rule pending future review of the licensee's heatup calculations (including the quantifying assumptions, initial temperatures, heat loads, room areas, any other supporting information used as input to the SINDA computer code and the SINDA program qualification package) for the fol!owing rooms:

Containment Ground Floor (154)

Valve Rooms (23 and 155)

Pressurizer Compartment (164A) hiain Steam Penetration Area (108) hiain Steam Penetration Platform (109)

Turbine-driven AFW Pump Room (74)

Comrngnis related to specific rooms:

• Control Room and Electrical Equipment Area The licensee's calculated temperature for the Control Room of 120.5'F and for the Electrical Equipment area of 120.7 are of concern.

Without knowledge of the total heat loads, room areas and quantifying assumptions use d in the SINDA computer code used by the licensee, we do not have any confidence that these are 16 3

conservative results. The licensee needs to provide additional information (including the quantifying assumptions, initial temperatures, heat loads, room areas and any other supporting information used as input to the SINDA remputer code) to verify that the Control Room and Electrical Equipment Area heatup calculations were based en a conservative analysis.

4 The licensee used the maximum operating temperature of 80'F as an initial Control Room temperature in its temperature rise calculation. This value is non-conservative unless there exists administrative controls to verify that this temperature will not be euceded during normal operttion of the plant. Otherwise, the licensee needs to use as an initial temperature the maximum temperature allowed by technical specifications.

UPS and Distribution Rooms The licensee assumed inverter efficiencies of 77% for the 7.5 KVA units and 85% for the 10 KVA units. We Delieve these efficiencies are non conservative. Based on our experience, a more realistic efficiency assumptions for 7.5 KVA and 10 KVA inverters are 75%

and 80% respectively. The licensee needs to use the inverter efficiencies recommended above, or provide technical justification for the use of higher inverter efficiencies in its analysis. In addition, the licensee must verify that the heat loss associated with the inverters is based on the rated load for each inverter and as the I

inverters are considered constant heat loss equipment (i.e.

independent of actualload).

The licensee concluded that the operation of the inverters in the UPS and Distribution rooms cannot be assured at the maximurn temperatures expected during an SBO. The licensee is planning to install DC powered ventilation fans in these rooms that will supply a sufficient capacity of outside air to these rooms to maintain the room temperature below the temperature at which inverter operability can be assured. We accept the licensee's resoNtion to 17

this problem. However, the licensee needs to re-evaluate the temperature rise calculations for these rooms taking into account the above considerations regarding inverter efficiencies and heat loads.

Battery Rooms We agree with the licensee's approach to calculating the minimum expected temperature in the battery room and selecting a temperature lower than the minimum expected tempera.tre as the electrolyte temperature in the battery sizing calculation.

Containment Essentially, for a large dry containment, the LOCA/MSLB mperature profile bounds an SBO event. However, the licensee's usponse does not soundly support this conclusion. Although the containment heat load assumed by the licensee (5E+6 Blu/hr) appears to be reasonable, the licensee did not consider the heat loads associated with decay heat rate and the assumed serl leakage of 111 gpm, consistent with the reactor coolant inventory analysis.

Bwause of the variability among plants, the licensee cannot use a generle analysis without justifying its applicability to the plant in question. The licensee needs to provide additional information to verify that the.LOCA/MSLB temperature profile bounds an SBO event.

Thus, the licensee needs to address each of the comments described above that were specific to individual rooms in its heatup calculations, assume a more conservative value for concrete thermal conductivity

(

of (0.7 Btu /hr ft 'F) in its calculations, and provide additional information for future review (as describmi above) for those rooms that were identified as having insufficient information.

18

)

5.

Containment Isolation Licensee's Submittal The licensee stated (13) that the plant list of containment isolation valves (CIVs) has been reviewed to verify 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-1E power supplies. The licensee stated that no plant modificttions and associated procedure changes were determined to be requ' ired.

Review of Licensee's Submittal Uchig information contained in FSAR Tables 6.2.4-1, 6.2.4-2 and 6.2.4-3 (12) we reviewed the list of plant CIVs to determine those which could not be excluded from consideration using the five criteria of R.G.1.155.

Our review did not identify any valves which could not be excluded using the five exclusion criteria of R.G.1.155. Thus, we conclude that all 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-1E powet supplies.

6.

Reactor Coolant Inventory Licensee's Submittal The licensee stated (13) that a plant-specific analysis of RCS inventory assumed that reactor coolant pump leakage is initially 25 gpm/ pump and_ decreases with decreasive RCS pressure. This analysis shows tFM the expected rates of RCS inventory loss under SBO conditions do not result in core uncovery in four hours. Therefore, makeup systems, in addition to those currently available under SBO conditions, are not required to maintain core cooling under natural reci cu:stion.

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The licensee stated (M) that an additional 12 gpm technical specification leakage was assumed in its calculation. The licensec assumed RCP leakabe to be a function of RCS pressure with an initial RCP sealleakage of 25 gpm/ pump at 2250 psia RCS pressure. It was assunted that the reactor was not de-pressurized below the accumu]ator injection pressure of 785 psi. Further, the licensee stated that the calculation was performed in two segments. During the first 2900 seconds of the SBO event, the licensee evaluated the RCS inventc.ry losses using the RETRAN-02 trans! mt analysis code and a two-loop model of the RCS. The code we oW :.3 accurately account for the numerous perturl'lom vhich u._.;r in the system (i.e. reactor trip, RCS coastdown, AFW initiation, RCS depressurization). After 2900 seconds, the licemee performed a hand calculation to determine the approximate time until core uncovery. The lia nsee stated that this was possible because after 2900 seconds the system is relatively stable with no major perturbations occurring. The licensee concluded that the core would remained covered in excess of eigl.t hours.

Review of Licensee's Submittal Using the information provided in the CPSES FSAR (12), assuming a total leak rate of 112 gpm and reactor depres>urization in the accumulator injection pressure of 785 psi, we calculated the volume of water remaining in the core at the end of a four hour SBO,o be 6313 3

ft. Based on our expericace with similar 4-loop Westinghouse PWRs, this exceeds the required volume of to cover the core.

ts,we conclude that the core will not be uncovered during a four hour SBO event.

NOTE:

The 25-gpm RCP seal leak rate was agreect to between NUMARC and the NRC staff pending resolution of Generic Issue (GI) 23. If the final resolution of GI-23 defines higher RCP seal leak rates than assumed for the RCS inventory evaluatic.a, the licensee needs to be aware of the potential impact of this resolution on its analyses and actions addressing conformance to the SBO rule.

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a 3.3 Proposed Procedure and Training Licensee's Submittal i

The licensee rtated (13) that plant procedures have been reviewed and that changes necessary to meet the guidelines in NUM ARC 87 00, Section 4 will be implemented in the following' areas:

Station blackout response - Procedure ECA-0.0A," Loss of All AC Power";

AC power restoration - Procedure ECA-0.0A, " Loss of Ah AC Power";

a Severe weather - Procedure ABN-907A, " Acts of Nature";

[

The licensee added that procedure changes associated with its proposed modification in the UPS inverter rooms will be identified, developed and implemented coincident with the instellation of the mcdification.

Review of Licensee's Submittal We neither received nor reviewed the affected procedures, although several procedure changes have been identified as being required to maintain containment integrity under SBO conditions. We consider theseT>rocedures to be plant specific actions concerning the recuired activities to cope with an S00. It is the licensee's responsibility to revise and implement these procedures, as needed, to mitigate an SBO event and to assure that these procedures are complete and correct, and that the associated t aining needs are carried out accordingly.

3.4 Proposed Modification Licensee's Submittal In its HVAC analysis, the licensee determined (13) that the operability of the UPS inverters (rooms 119 and 121) could not be assured at the maximum twnperatures expected during an SBO. As a result, a hardware modification is 21 I

planned to redu w these temperaturcs. The modification will install DC-powered ventih ion fans that will supply a sufficient capacity of outside air to the UPS rooms to maintain the room temperatures below the temperature at which inverter operability can be assuied. If necessary, this modific: tion will also include the installation of additional battery capacity. In the telephone conference on November 1,1991, the licensee stated that this additional capacity would nct come frora the existing Class IE batteries. The new ventilation fans will draw power from either the existir.g non Class 1E batteries or from a new dedicated battery. The licensee stated (13) that the UPS rooms hardware modifications are planned for a refueling outageit least 120 days after receipt of the NRC Safety Evaluation Report.

Review of Licensee's Submittal We accept the licensee's proposed modification to redu:e the temperature in the UPS inverter rooms. The licensee needs to provide assurance that this modification will not impact the capability of the Class IE batteries to supply SBO loads during a four hour SBO event.

In addition, our evaluation found several areas where the licensee may need to perform re-evaluations, some of these may result in modifications /

changes to the exi3 ting equipment.

3.5 Quality Assurance and Technical Specifications The licensee stated (14) that all equipment required to cope with an SBO is safety-related and included in the CPSES QA program, pursuant to 10CFR50, Appendix B, except for the turbine stop valves. In the SBO scenario, the turbine stop valves are relied upon for immediate steam isolation. These valves are non-safety related, but are surveilled and maintained per CPSES Technical Specification 3/4.3.4, " Turbine Overspeed Protection."

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4.0 CONCLUSION

S Based on our review of the licensce's submittals and the information available in 'he FSAR for CPSES Unit 1, we find that the submittal conforms with the requirements of the SBO rule and the guidance of RG 1.155 with the following exceptions:

1.

Effects of Loss of Ventilation We concider tlie licensee's analysis to conform with the SBO rule pending future review of the licensee's heatup calculations (including the quantifying assumptions, initial temperatures, heat loads, room areas, any other supporting information used as input to the SINDA computer code and the SINDA program qualification packt.ge) for the following. rooms:

-6 Containment Ground Floor (154)

Valve Rooms (23 and 155)

Pressurizer Compartment (164 A)

Main Steam Penetration Arez (108)

Main Steam Penetration Platform (109)

Turbine-driven AFW Pump Room (74)

Based upon a review of the information provided by the licensee, we have concerns in the following areas:

General Throughout the calculations, the licensee assumes a concrete thermal conductivity of 0.854 and 0.92 (Stu/hr ft F). These values have previously been considered too high and therefore non-conservative for SBO analysis. A more appropritate and acceptable value of 0.7 needs to be used.

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Control Room and Electripl Ecuipment Arn e

The licensee needs to provide additional information (as described in Section 3.2) to verify that the Control Room and Electrical Equipment Area heatup calculations were based on a conservative analysis. The licensee used the maximum operating temperature of 80'F as an initial Control Room temperature in its temperature rise calculation. This value is non-conservative unless there exists administrative controls to verify that this temperature will not be exceeded during normal operation of the plant. Otherwice, the licensee needs to use as an initial temperature the maximum tempe.ature allowed by technied specifications.

UPS and Distribution Rooms The inverter efficiencies assumed by the license in its calculation are l

non conservative. The licensce needs to use more conservative inverter efficiencies (as recommended in Section 3.1), or provide tecnnical justification for the use of higher inverter efficiencies in its analysis. The licensee needs to verify that the inverter heat loads are based on design loads rather th n SBO loads which are expected to be much less. The licensee is planning to install DC powered ventilation fans in these rooms reduce the temperature during an SBO and insure inverter operacility. We accept the licenseW resolution to this problem. However, the licensee needs to re-evaluate the temperature rise calculations for these rooms taking into account the above considerations regarding inverter effidencies and heat loads.

Containment L

l-Because of the variability among plants, the licensee cannot use a generic analysis without justifying its applicability to the plant in question. The licer.see needs to provide additional information to verify that the LOCA/MSLB temperature profile bounds an SBO event.

l 24 1

2 Preposed Modification The 11censee needs to provide assurance that its proposed modification to reduce the temperature in the UPS inverter rooms will not impact the capability of the Class 1E batteries to supply SBO loe.ds during a four hour SBO event.

In addition, our evaluation found several areas where the licensee may need to perform re-evaluations, come of these may result in modifications / changes to the existing equipment.

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! 5.0 REFERENCEE m

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 Acddents at Nuclear Power Plants - Technical Findings Related to UnresolvM Safety Issue A-44," NUREG-1032, Baranowsky, P.W., June 1988.

3.

U.S. Nuclear Regulatory Cummission, " 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 t

System at' Nuclear Power Plants," NUREG/CR 2989, July 1983.

5.

U.S. Nuclear. Regulatory Commission, " Emergency Diesel Generator -

' Operaing Experience,1981a1983," NUREG/CR-4347, December 1985,

- 6.

U.S. Nucli.ar Regulatory Commission, " Station Blackout Accident Analyses (l' art of NRC Task Action Plan A-44)," NUREG/CR-3226, May 1983.

7.

U.S. Nuclear Regulatory Currmission Office of Nuclear Regulatory Research, J

(

1" Regulatory Guide 1.155 Staticn Blackout," August 1988.

8.

' Nuclear Management and Resources Council, Inc., "Gt.?delines and Technical

-Bases for NUMARC Initiatives Addressing Sta-

ackout at Light Water

~

~ Reactors,".NUMARC 87-00, November 1987..

9.

Nuclear Safety Analysis Center, "The Reliability of Emergency Diesel.

g

- Generators at U.S. Nuclear Powcr Plants," NSAC-108, Wyckoff, H., September -

4 1986.

.- 10.

- Thadani, A. C., Letter to W. H. Rasin of NUMARC, " Approval of NUMARC Documents on Station Blackout (TAC-40577)," dated Octot er 7,1988.

26 4.

g L.

.. +

-..4

-m

~.

11.

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

12.

Comanche Peak Steam Electric Station, Final Sdety Analysis Report (FSAIO.

13.

Cahill, William J., letter to NRC Document Control Desk, " Response to Station Blackout Rule," Docket No. 50-445, dated November 5,1990, 14.

Cahill, William J., letter to NRC Document Control Desk, " Response to NRC Request for Additional Informatior. Regarding CPSES Station Blackout Submittal" Docket No. 50-445, dated. wember 22,1991.

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