ML20091C377

Provides Response to NRC Request for Addl Info Re SE on Conformance of Plant W/Station Blackout Rule.Licensee Will Provide Addl Info on Proposed Changes by 920529

ML20091C377
Person / Time
Site:	Browns Ferry
Issue date:	03/27/1992
From:	Baron R TENNESSEE VALLEY AUTHORITY
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
TAC-M68517, TAC-M68518, TAC-M68519, NUDOCS 9204030202
Download: ML20091C377 (10)

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l ItAR271992 U.S. Nuclear Regulatory Commission ATTH: Document Control Desk Washington, D.C. 20555 j Centlement In the Matter of ) Docket Nos. 50-259 Tennessee Valley Authority ) 50-260 50-296 BROWNS FERRY NUCLEAR PLANT (BFN) - NRC REQUEST : 'l ADDITIONAL INFORMATION REGARDING TVA'S RESPONSE TO NRC'S SAFETY EVALUA'440N (SE) ON Tile CONFORMANCE OF BFN PLANT WITil Tile STATION BIACK0UT RULE (S110)

(10CFR50.63)(TACN0s.p)8517,p685184ANDkB519) f

Reference:

1) HRC Letter to TVA dated July 11, 1991, "Sofety Evaluation on the Conformance of IlFN with the Station Blackout Rule (TAC N0a. 68517, 68518, and 68519)"

2) HRC Letter to TVA dated March 5, 1992, " Request for Additional Information on Station Blackout for Browns Ferry (TAC Nos. 68517, 68518, and 68519)"

This letter provides IVA's response to NRC requesta for additional information on Station Blackout for BMi made during a January 8,1992 TVA/NRC teleconference and by Reference 2. As dJscussed during a March 19, 1992 TVA/NRC teleconference, TVA plans to implement a more realistic coping strategy for SB0 during multi-unit operation, lleating, ventilating, and air-conditioning (HVAC) (quipment vill be powered from the non-blached out unit's emergency diesel generators (EDG) to provide cooling in some areas. Also, as discussed in the March IV, 1992 teleconference, TVA plans to request a change to BFN's Emergency AC (EAC) group classification. TVA vill provide additional information on these proposed changes by May 29, 1992. These changes vill require a supplemental safety evaluation report (SER) to address SB0 compliance for multi-unit operation. They do not affect SB0 conpliance for single unit operation. Therefore, no changes to the SER provided by Reference 3, as it relates to Unit 2, are required. As previously committed, BFN vill be in compliance with the SB0 rule for single unit operation by May 30, 1992. )

9204030202 920327 PDR p

ADOCK 05000259 PDR 3 ))[- I

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U.S., Nuclear Regulatory Conniasion MAR 2 71992 Enclosures 1 and 2 restate the Je.nuary 8,1992 teleconference questions and the March 5, 1992 Request for Additional Information questions, respectively, and provide TVA's response to each. TVA requests that a supplemental SER that addressen multi-unit operation be provided by December 31, 1992.

A punnary liut of connitments contained in this letter is provided in Enclosute 3. If you have any questions, please contact me at (205) 729-7570.

Sincerely,

'(2 bW R. R. Barcu Enclosures

.cc (Encionstes):

.NRC Resident Inspector Browns Ferry Nuclear Plant Route 12. Box _637 Athens, Alabama 35611 Mr. Thierry M. Ross, Project Manag0r U.S. Nuclear Regulatory Connission One White Flint, North 11555 Rockville Pike Rockville, Maryland 20852 Mr. B. A. Wilson, Project Chief U.S. Nuclear Ret,ulatory Commission Region 11 101 Marietta Street, NW, Suite 2900 Atlanta, Georgia 30323 i

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e s ENCLOSURE 1 Page 1 of 3 l

TENNESSEE VALLEY A11THORITY Bh0WNS FERRY NUCLEAR PLANT r TVA Dt6PONSE TO NRC QUESTIONS ,

The NRC's safety Evaluation (SE) for BFN's compliance to the Station Blackout (8bO) rule was provided to TVA by letter dated July 11, 1991. TVA provided a response for DFN Unit 2 by letter dated August 13, 1991 and for DFN Units 1  :

and 3 by letter dated December 2, 1991. Additional information was requested by the NRC during a January 8, 1992 teleconferenck held between TVA DFH '

representatives and Thierry Ross (NRR) regarding DFN's Unit 2 response. TVA originally agreed to provide a response to this request by March 6, 1992; however, the NRR Project Hansger for BrN requested that TVA withhold this response and provide it concurrent with the March 5, 1992 RAI response.

The following dlcuments the verbal responses provided by TVA on January 8, 1992. TVA's responses to NRC Questions a through 3h below apply to Unit 2 only. The responses to Questions 3C and 3D apply to all three DFN units.

With the exception of TVA's responses to NRC Question 3A, Concern #1 and Question 3D, Concerns #1 and #2, these are the same responses provided verbally on January 6, 1992. For these chree questions, TVA considered the additional clarification provided an the January 8 teloconference and has provided a revised response and/or additional clarification.

• NRC QUESTION 1 In TVA's August 13, 1991 response to St Section 2.2.4, TVA stated a re-evaluation of the Effects of Loss of Ventilation wan expected to be completed by December 6, 1991. NRR needs a copy of the calculation.

BFN RESPONSE TVA extended the completion date for the Unit 2 calculation to March 6, 1992 per telecon with NRR on December 3, 1991. The Unit 2 calculation package la available for FRR review at TVA's Rockvillo, Maryland office.

• NRC QUESTION 2 In TVA's August 13, 1991 response to SE Secticn 2.2.5, TVA stated a re-evatus, tion of containment isolation valves was expected to be completed by December 6, 1991. NRR needs a copy of the evaluation.

BrN RESPOWWE TVA extendvd the completion date for the Unit 2 calculation to March 6, 1992 par telecon with NHR on December 3, 1991. The Unit 2 calculation

package is available for NRR-review at TVA's Rockville, Maryland office. ,

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A ENCLOBURE 1 Page 2 of 3 e NRC QUESTION 3A NRR neede a response to concerns #1 and 2 on page 4 of SE Section 7.2,J, Class 1E Battery Capacity, the Safety Evaluation.

. Concern #1 - The licensee has taken an exception to the IF^ - ,dard 405 cell sizing method in its calculatione by breaking t!.* saa step siae into smaller than one-minute intervals. This results in a smaller not average current and, theref ors, is non-conservative.

BrN Response - The Unit 2 esiculations have been revised to use the 1 minute rate as recommended by IEEE Standard 485. This calculation is available for NRR revier at TVA's Rockville, Maryland office.

. Concern #2 - The licensoe assumed that only two circuit breakern wrrnd be closed at the end of the SB0 event and that 5 ampere would be required to close each breaker. A review of the plant electrical

1. letributien drawings indicates that more than two circuit breakers are required to connect the emergency buses to the of f site power source.

BrN Response - The Unit 2 calculation includes over 300 amp f or one minute to close switchyard breakerus this is more than adequata to close any number of switchyard breakers.

e NRC QUESTION 3D Respond to the following additional concerns:

. Concern #1 - For the battery roon. temperature, the licennec assumed an initial temperature of 76'F. The licensee needs to ensura that the room ambient air temporature will not drop below tnis temperature under any circumstances or if it does, there is an alarm in the control room to alert the operators to take appropriate action (See TER page 13 &

25)(Refer to NttHARC 87-00 Section 7.2.2 page 7-7 & 7-9 for electrolyte temperature)

BrN Hosponse - The 76 degrees F temperature used 'J bulk average temperature for control bay elevation 593. Based on the control systems for the cooling / heating systems and the air flow patterna this is the temperature that would be expected during normal conditione. TVA has revised the battery capacity calculation for BfN Unit 2 using an initial tempnrature of 69'F based on an evaluation of measured temperaturcs.

This to the lowest electrolyte temperature anticipated under normal operating conditione. Since TVA's calculation uses the lowest anticipated electrolyte temperature, there is no need to provide an alarm in ti.e control room. These calculations are available for review at TVA'o Rockville, Maryland office.

. Concern #2 - The licensee used a design margin of 1.00 in its battery calculation. This in not consistent with the guidance provided in ,

IEEE Standard 485, which recammends a design margin of 1.10-1.15 be used. (See TER page 14, 25, & 26) This margin is required for lose-than-optimum operating conditions of the battery due to improper maintenance, recent discharge or ambient temperature lower than expected.

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9 ENCLOSURE 1 Page 3 of 3 BrH Response - The design margin for the Unit 2 battery calculation was in terms of voltage in excess of e.he minimum required to support loads. The battery calculation has been revised to show design margin as e percent of battery capacity.

BFN was lice, sed prior to the issuance of IEEE Standard 485. The dusign margin for which the plant was licensed is defined as any capacity in excess of that required to support design basis load conditions at BFN.

• VP. considers this design margin (currently 1.02-1.03) adequate for use in the 500 battery calculation. This design margin may also be used for future load additions. NUKARC 07-00 trefor to section 7.2.2, page 7-10) states that DC power requirements for a required SBO may be estimated using the same methodology for which the plant was licensed.

e NRC QUERTION 3C NRR needs the duration of emergency bearing oli pump and generator seal oil pump loado for all 3-units on non-1R battery.

BrN RESPONSE These pumps are not ussd for recovery from an SB0 at BrN. Thorofore, no calculation for $B0 is required. (See TVA'u response to NRC Question 3D below.)

e NRC QVERTION 3D NRR needs a copy of the EDO battery calculation.

BTN RESPONSE The diese? generator batteries are not adequate to lart 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />. The SBO analysis assumes tho batteries were depleted early in the event trying to start the diesels. No credit is taken for dissol batteries in analysis therefore no calculation for SB0 is required.

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RNCLOBURE 2 Page 1 of 4 TEWNESSEE VALLEY AUTHORITY BROWN 5 FERRY NUCLEAR PLANT TVA Rosponse to NRC Request. f or Additional Information Dated March 5, 1992 This enclosure restates the Request for Additional Information items in NRC's letter dated March 6, 1992 and provides TVA's response to anch. In thoso ,

cases where the RA! items below are similar to the January 8, 1992 teleconference questions, TVA refera to tne response made for the teleconference question in Enclosure 1.

e NRC Iten A.1 Provide completion schedule for DC-power system modifications.

BrH Response DC-power system modifications required for $bo compliance during multi-unit operation will be completed pilor to Unit 3 restatt. Some of these modifications are also being performed to support Unit 2 operations and will be completed prior to restart from the Unit 2 Cycle 6 outage. +

e NRC ften A.2 Provide results from the modified battery capacity calculations for multi-unit operation using the t.ew safuty-related batteries (actual calculations shoeld be made available at the TVA Acckv111e offica). Justify all assumptions, and address any applicable ncn-conservations or concerns identified in the staff's safety evaluation (SE) (e.g., Section 2.2.2).

BFN Response As stated in TVA's December 2, 1991 responen, the multi-unit calculation

-for battery capacity will be revised usino field verified walkdown data for Unite 2 and 3 by March 31, A992. This r.'1culation will be made available to NRR for review at TVA's Rockviale, Ma*yland office by April 7, 1992.

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e NRC Itee A.3 In Enclosure 1 (on page 1 of 3) of TVA'n responso dated December 2, 1991, "the 120V AC Reactor Core Isolation Cooling (RCIC) system controls... will be transferred to an appropriate source." Identify this source and verify that it will be available during the four-hour duration of SDO.

y.

BrN Response t-l The 120V AC Reactor .aolation Cooling (RCIC) system controle will be powered by a Class . DC power supply system and will be available during the four-hour duracton of SBO.

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i ENCLOSURE 2 Page 2 of 4

• NRC Item A.4 Following the four-hour SBO event, power will be restored from either offsite or onsite (i.e., emergency diesel generators (EDG)) sources, Sinca EDO testart and switchyard circuit breaker closure are powered from different sources, TVA should consider both scenarios in order to properly bound the end of the postulated Sbo event. TVA is requested to verify that Browns Ferry can accommodate the most limiting power restoration scenario (e.g., calculations that confirm adequate DC power supplies to restart ED0s).

BrN Response TVA stated in the August 13 and December 2, 1991 responses that TVA's SB0 analysis (Unit battery capacity calculation) does not constder that ac power will be restored by the diesel generatorn, therefore, de power is not needed for the control and fleid flashing of the EDGs. TVA explained during the January 8, 1992 teleconference that the SB0 anelysis assumes the EDG batteries a.ro depleted early in t;.e event trying to start the diesels and that no credit was taken fer diesel batteries in the SBO analysis, therefore, an EDG battery capacity calculation with respect to SEO was not required. The HRC agreed with this conclusion during the telaconference. After iesuing this RAI, the TVA BFN NRR Project Manager determined, and advised TVA on March 10, 1992, that Item A.4 abova was not an explicit requirement and that TVA's current coping strategy was acceptable. TVA's ac power restoration strategy is clarified below.

BFN procedure 0-AoI-57-2, Station Blackout, directs the operator to reattte ac power via the EDCs or offolte power. In relation to the EDGs, the procedure directs specific individuals to assist in restoring diesel generators to operable status. This includes determining and correcting tha cause of EDG start and/or loading failures.

If troubleshooting fails to correct EDG problemd or the EDG Latteries are depleted during this effort, the only method available for restoring ac power is by offsite power. It is not possible to determine when this will occur since it would be dependent upon the type of problem and how long it takea to address. Each EDG has a dedicated 125V de battery that provides control and field flsehing. The batteries are sized to carry the control load and provide three starts within a thirty minute period. After the three attempts, the battery is considered depleted and, as a result, the EDGs are no longcr available tor reatoring AC power.

BFN's SB0 battery capacity calculation was performed for the Unit battery that provides de pc.er for required SBO loads for the four hour coping period. *: 10 EDG is not powered from the Unit battery, therefore power requiremert.s for utarting the EDG are not considered in thic calculation.

e NRC Item A.5 TVA used a design margin of 1.00 in its battery calculations. This is inconsistert with the guidance of IEEE Standard 4BS, which recommends 1.10

- 1.]5. 1; ovide justification for using an apparently non-conservative design margin.

ENCLO8U3E 2 Page 3 of 4 4 BFN Responso See renponNe to NRC Question 3B, Concern #2 in Enclosure 1.

e KRC Itaa A.6-TVA assun.ed ar. initial battery room temperature of 767. 'this in inconsistent with the guidance in NUKARC 87-00 (Section 7.2.?i I' rov ide rationale far deviating from accepted NuaARC g,ptance.

BFH Response See response to NRC Quhstion 3D, Concern #1 in Enclosure 1. 7 e NRC Item B.1 In letters dated August 13 and December 2, 1991, TVA committed to re- ,

evaluate the containment isolation valveJ (CIV) in accordanca with the exclusion criteria of Regulatory Guide (RG) 1.155. List all CIVs, j indichting those that can be excluded (opecify.ing applicable RG 1.155 exclusion criteria) and those that can not.

BFN Responsn i

See response to NRC Question 2 in Enclosure 1. Also, the Units 1 and 3 CIV re-evaluation will be completed by March 31, 1992 and made available to NRR for review at TVA's Rockville, Maryland office by April 7, 1992.

• NRC Ttem C.1 In letters dated ,%. gust 13 and December 2, 1991, TVA committed to revise its heat-up calculations based upon otaff recommended input data (section 2.2.4 of staff SE). TVA is requested to provide the results of its modified haat-up calculations (hetual calculations to be made available at ,

g the TVA Rockville office) for areas containing SBO equipment (e.g.,

HPCI/RCIC rooms, the control room, drywell, etc.). Initial inputs, annumptions, and computer codes used in these calculations are to be identified. Equipment qualification temperatures for each area also need to be provided.

BFN Response

_ As committed in TVA lettere dated August 13 and December 2, 1991, TVA has evaluated the racommended input data and utili?ed it in arooelated calculations as applicable. For singlo unit operation, refer to the lh. response to NRC Question 1 in Enclosure 1. For multi-unit operation, heat-up calculations or the HPCI, RCIC, Steam Tunnel and Drywell areas will be completed by March 31c 1992.

For a.ulti-unit operation, TVA plans to make ac power available to HVAC for cooling the other dominant areas of concern from the non-blacked out units' EDGu. Therefore, heat-up calculationo will not be performed for these areas,

ENCLOSURE 2 Page 4 of 4 J

• NRC Itean D.3 ,

confirm that all of the equipment and compostents needed riuring an SB0 event.are specifically identified and covrfed by a quality assurance program consistent with the guidance of kG 1.155.

BFN Response 5B0 equipment is covered by n quality aamurance program consi. stent with the guidance of RG 1.155.

a ENCLOSURE 3 TENNESSE8 VALLEY AUTHORITY BROWNS FERRY NUCLEAR PLANT

SUMMARY

.OF COMMITMENTS

1. TVA will make a copy of the BFN 'Jnita 1 and 3 evaluation package for containment Isolation Valves available for NRR review at TVA's Rockville, Maryland office by April 7, 1997..

2. TVA sill make copies of the calculation packages for Unit Unttery Capacity, Heatup and EDGs that support multi-unit operation available for NRR review at TVA's Rockville, Maryland office by April 7, 1992.

3. DC power system modifications required for $50 compliance during multi-unit operation will be completed prior to Unit 3 rectart.

4. TVA .ill provide additional information on proposed changes in SBO coping strategy and EAC group classification by May 29, 1992.

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