ML17223B340

Forwards Responses to NRC 910912 Ltr Transmitting Safety Evaluation on Station Blackout Rule (10CFR50.63(a)). Commitment for Required Blackout Duration Revised to Target Reliability Level of Equal to or Greater than 0.975

ML17223B340
Person / Time
Site:	Saint Lucie
Issue date:	11/26/1991
From:	Sager D FLORIDA POWER & LIGHT CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
L-91-311, NUDOCS 9112040019
Download: ML17223B340 (16)

Text

ACCELERATED DI UTION DEMONS TION SYSTEM REGULATORY INFORMATION DISTRIBUTION SYSTEM (RIDS)

ACCESSION NBR: 9112040019 DOC. DATE: 91/11/26 NOTARIZED: NO DOCKET FACIL:50-335 St. Lucie Plant, Unit 1, Florida Power & Light Co. 05000335 50-389 St. Lucie Plant, Unit 2, Florida Power & Light Co. 05000389 AUTH. NAME AUTHOR AFFILIATION SAGER,D.A. Florida Power & Light Co.

RECIP.NAME RECIPIENT AFFILIATION Document Control Branch (Document Control Desk)

SUBJECT:

Forwards responses to NRC 910912 ltr transmitting safety evaluation on station blackout rule (10CFR50.63(a)).

Commitment for required blackout duration revised to target D reliability level of equal to or greater than 0.975.

DISTRIBUTION CODE: A050D COPIES RECEIVED:LTR ENCL SIZE:

TITLE: OR Submittal: Station Blackout (USI A-44) 10CFR50.63, MPA A-22 NOTES:

RECIPIENT COPIES RECIPIENT COPIES D ID CODE/NAME LTTR ENCL ID CODE/NAME LTTR ENCL PD2-2 PD 1 1 NORRIS,J 1 1 D INTERNAL: ACRS 1 1 AEOD/DS P/TPAB 1 1 NRR PD2-4PM TAM 1 1 NRR/DET/ESGB 8D 2 2 NRR/DST/SELB NRR/DST/SRXB8E 3

1 3

1 N /. - PLB8Dl 01 3 3 G 1 1 EXTERNAL: NRC PDR 1 1 NSIC D

NOTE TO ALL "RIDS" RECIPIENTS:

PLEASE HELP US TO REDUCE WASTE! CONTACT THE DOCUMENT CONTROL DESK, ROOM Pl-37 (EXT. 20079) TO ELIMINATEYOUR NAME FROM DISTRIBUTION LISTS FOR DOCUMENTS YOU DON'T NEED!

TOTAL NUMBER OF COPIES REQUIRED: LTTR 17 ENCL 17

4 P.O. Box c, Ft. Pierce, FL 34954-0120 L-91-311 November 26, 1991 10 CFR 50.63 U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, D.C. 20555 Gentlemen:

Re: St. Lucie Units 1 and 2 Docket Nos. 50-335 and 50-389 Safet Evaluation on Station Blackout Rule By letter dated September 12, 1991 (J. A. Norris to J. H.

Goldberg), the NRC forwarded to Florida Power & Light Company (FPL) a Safety Evaluation (SE) on the Station Blackout (SBO) rule for St.

Lucie Units 1 and 2. By letter L-91-282, dated October 17, 1991, as required by 10 CFR 50.63(c)(4), FPL provided its commitment schedule for implementing equipment and associated procedure modifications necessary to meet the requirements of 10 CFR

50. 63 (a) .

In its letter of October 17, 1991, FPL committed to provide responses to the "Requests" of, as well as comments on, the NRC's SBO SE. Enclosed are FPL's Request responses and comments on the subject SBO SE. Additionally, as discussed in the enclosure, FPL has revised its commitment, for the required SBO duration. FPL will maintain the St. Lucie Unit 1 EDGs at a targeted reliability level equal to or greater that 0.975. As a result, FPL considers the required coping duration for St." Lucie Unit 1 as four hours.

FPL requests written NRC acknowledgement of the acceptability of FPL's responses to the NRC Requests of the SBO SE as .well as the positions delineated in the FPL Comments section of the enclosure.

If you have any additional questions on the enclosed, please contact us.

Very truly yours, D. A. ger Vice esident St. L ie Plant Enclosure DAS/PSL N570-91 cc: Stewart D. Ebneter, Regional Administrator, Region Senior Resident Inspector, USNRC, St. Lucie Plant II, USNRC 9ii20400i9 9ilI,26 05000335 PDR ADOCK P PDR an FPL Group company

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Enclosure St. Lucie Units 1 and 2 Docket Nos. 50-335 and 50-389 Safet Evaluation on Station Blackout Rule Requests Safet Evaluation Section 2.3e4

~Re uest: The licensee should complete the ventilation studies and include the studies and the results in the documentation supporting the SBO submittal that is maintained by the licensee. The licensee should implement any procedure changes and modifications that are required to assure adequate ventilation is maintained, in the areas containing SBO equipment, for the required coping duration.

FPL Res onse: FPL will complete SBO ventilation studies on a schedule sufficient to support the implementation of any procedure changes and modifications that may be required to a'ssure adequate ventilation is maintained in the areas containing safe shutdown equipment for the required coping duration.

The St. Lucie Unit 1 ventilation, studies will include the following:

1) Control Room FPL will calculate the peak Control Room temperature assuming that, a single train of heating, ventilation, and air conditioning (HVAC) is available and powered by the Alternate AC (AAC) source. The single HVAC train consists of an air handler and its respective compressor (i.e., HVA-3A with ACC-3A, HVA-3B with ACC-3B, or HVA-3C with ACC-3C) The peak temperature will be calculated and confirmed acceptable with respect to the availability of safe shutdown equipment and Control Room habitability during the SBO event.

2) Reactor Containment Buildin The peak containment temperature will be calculated assuming:

a) A Reactor Coolant System (RCS) leak rate consistent with the RCS inventory analysis performed to address the Request of Safety Evaluation Section 2.3.6, Reactor coolant inventor b) No containment heat removal systems are operating throughout the SBO event.

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St. hucie Units 1 and 2 Docket Nos. 50-335 and 50-389 Safet Evaluation on Station Blackout Rule(cont) c) Normal containment heat removal system is restored (i.e., the containment fan coolers) following termination of the SBO event.

The calculated peak containment temperature will be used to confirm the availability of SBO safe shutdown equipment during the SBO event.

3) Reactor Auxiliar Buildin Char in Pum Room FPL will calculate the peak temperature in the charging pump room assuming only one Reactor Auxiliary Building (RAB) main supply fan (i.e.,

HVS-4A or HVS-4B) and no RAB main exhaust fan operating.

The supply fan will be assumed to be operating once the AAC source is available to the blacked-out unit. The charging pump room peak temperature will be evaluated with respect to the SBO event charging system availability.

RAB Electrical E ui ment and Batter Room FPL will calculate the peak temperature in safety-,related electrical equipment rooms. It will be assumed that one train of the electrical equipment room supply fans (HVS-5A or HVS-5B) and exhaust fans (train "A" fans RV-2, RV-3, RV-4, HVE-11 or train "B" fans RV 1g and HVE-12) will be powered from the AAC source.

Other RAB Areas FPL will evaluate the effects of reduced ventilation capability in the remainder of the RAB with respect to the SBO event safe shutdown equipment availability. Peak temperatures and equipment availability will be analyzed accordingly.

4) Auxiliar Feedwater'FW S stem The steam-driven AFW pump and other AFW system components necessary to provide feedwater to the steam generators rely on natural ventilation. As a result, the AFW system operating conditions would not be affected by special SBO event environmental conditions and no ventilation evaluations nor analyses will be performed.

The evaluations and analyses described above will be included in the St. Lucie Unit 1 Updated Final Safety Analysis Report (UFSAR).

Any recpxired procedure changes identified as a result of these evaluations and analyses will be in the procedures developed to deal with a SBO event at St. Lucie Unit 1.

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St. Lucie Units 1 and 2 Docket Nos. 50-335 and 50-389 Safet Evaluation on Station Blackout Rule(cont)

Safet Evaluation Section 2.3.6 Receuest: The licensee should evaluate and confirm that there will be adequate reactor coolant system inventory to ensure continued core cooling for the required 8-hour SBO duration and recovery therefrom with an assumed leakage rate of 112 gpm, and include this information in the documentation supporting the SBO submittal that is maintained by the licensee.

FPL Res onse:

As noted below in Station Blackout Duration of FPL Comments, FPL has reconsidered its commitment for the required SBO duration. FPL revises its commitment conservatively and will maintain the St.

Lucie Unit 1 EDGs at a reliability level equal to or greater than 0.975. As a result, FPL will consider the required duration for St. Lucie Unit 1 as four hours. Therefore, the coping FPL evaluation and confirmation of adequate reactor coolant system inventory to ensure continued core cooling will be conducted for a four hour SBO event duration.

In accordance with NRC SE Section 2.3.6, Reactor coolant inventor FPL will evaluate and confirm that adequate RCS inventory will remain at the termination of the SBO event. However, the evaluation will not consider the effects on the non-blacked-out (NBO) unit's EDG load profile of the hypothetical 112 gpm RCS leak rate.

Similarly, the St. Lucie Unit 1 SBO Emergency Operating Procedures (EOPs) will not assume that operator actions are required to mitigate the effects of a small break loss of coolant accident (SBLOCA) (i.e., due to the 112 gpm RCS leak rate) in conjunction with an SBO event. The evaluation will verify that the assumed 112 gpm RCS leak rate, which FPL will assume decreases throughout the course of the event as RCS pressure decreases, will not result in the loss of core coverage, that sufficient core cooling is available for the SBO event duration, and that recovery from the event is analytically achievable.

The St. Lucie Unit 1 RCS inventory evaluation and confirmation will be completed by FPL using RETRAN03 MODOOO and assuming a decay heat load in accordance with ANS 1979 (times a 1.05 uncertainty factor).

The inventory loss evaluation will assume a pressure-dependent leak rate which decreases over the duration of the SBO event; RCS inventory makeup via a charging pump will be assumed at some time following the completion of the AAC intertie. Auxiliary Feedwater (AFW) initiation will be assumed in accordance with system design and safety injection will be assumed to be unavailable for the 4 hour4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> SBO event.

"St. Lucie Units 1 and 2 Docket Nos. 50-335 and 50-389 Safet Evaluation on Station Blackout Rule(cont)

The evaluation and confirmation will be completed by September 12, 1993, and the results of the evaluation will be included in the St.

Lucie Unit 1 Updated Final Safety Analysis Report (UFSAR).

Safet Evaluation Section 2.5 Receuest: The licensee should provide a full description, including the nature and objectives, of the required procedure changes identified in 2.4 and 2.5 above in the documentation supporting the SBO submittals that is to be maintained by the licensee.

i FPL Res onse: FPL will complete the SBO procedure changes by September 12, 1993. These procedures will give detailed instructions on the method for cross-tying the St. Lucie Unit 2 EDGs to Unit 1 as well as the Unit 1 EDGs to Unit 2. The revised procedures will not consider multiple event scenarios such as a small break loss of coolant accident (SBLOCA) resulting from Reactor Coolant Pump (RCP) seal 'failure(s). Existing EOPs would be used for multiple event accident management.

The full description, including the nature and objectives, of the required procedure changes identified in Sections 2.4 and 2.5 of the SE, will be included in the St. Lucie Unit 1 Updated Final Safety Analysis Report (UFSAR).

Safet Evaluation Section 2.7 Receuest: The licensee should confirm that an EDG reliability program which meets the guidance of RG 1.155, Section 1.2, will be implemented. Confirmation that such a program is in place or will be implemented should be included in the documentation supporting the SBO submittals that is to be maintained by the licensee.

FPL Res onse: FPL will confirm, by September 12, 1993, that an EDG reliability program has been implemented to attain and maintain the St. Lucie Unit 1 targeted EDG reliability. Confirmation that such a program is in place will be included in the St. Lucie Unit 1 Updated Final Safety Analysis Report (UFSAR).

Safet Evaluation Section 3.0

~Re uest: The licensee is expected to maintain the reliability of the Unit 2 EDGs at 0.974 or greater in accordance with the licensing basis for Unit 2 in regard to the SBO issue. The licensee

St. "Lucie Units 1 and 2 Docket Nos. 50-335 and 50-389 Safet Evaluation on Station Blackout Rule(cont) is also encouraged to update the SBO coping procedures for Unit 2 to incorporate the enhanced capability provided by the AC intertie between Units 1 and 2.

FPL Res onse: FPL will maintain the reliability of the St. Lucie Unit 2 EDGs at 0.974 or greater in accordance with the licensing basis for Unit 2 in regard to the SBO issue by implementation of an EDG reliability program which attains and maintains the St. Lucie Unit 2 targeted EDG reliability.

As discussed above in the FPL Res onse to the NRC Request related to Safety Evaluation Section 2.5, FPL will complete the SBO procedure changes by September 12, 1993. Consistent with FPL philosophy on the operation of St. Lucie Units 1 and 2, these procedure changes will implement a similar strategy for operationally coping with an SBO at either St Lucie Unit 1 or 2.

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St: ?ucie Units 1 and 2 Docket Nos. 50-335 and 50-389 Safet Evaluation on Station Blackout Rule(cont)

FPL Comments Station Blackout Duration In the St. Lucie units 1 and 2 Safety Evaluation on Station Blackout, the NRC staff, in Section 2.1 Station Blackout Duration, observes:

During the May 21, 1991, meeting with the NRC staff, the licensee agreed to...an 8-hour coping duration.

FPL has reconsidered its commitment for the required SBO duration.

FPL revises its commitment conservatively and will maintain the St.

Lucie Unit 1 EDGs at a targeted reliability level equal to or greater that 0.975. As a result, FPL considers the required coping duration for St. Lucie Unit 1 as four hours.

Pro osed AAC ower source In Section 2.2.2, Pro osed AAC ower source, of the NRC's SE, the NRC states,

...(T)he licensee provided (during the site audit review) the NBO loads (Unit 2) as 1954 kW and SBO loads (Unit 1) as 897 kW...The...(SAIC TER) documents the LOOP loads of the Unit 2 (NBO unit) as 2802.5 kW...and the corrected SBO loads of the Unit 1 (SBO unit) as 1133.5 kW. This tabulation indicates a total load of 3936 kW for the NBO and SBO unit...

FPL notes that the NBO loads of 1954 kW and the SBO loads of 897 kW were identified as conceptual values and provided as informational loadings during the St.Lucie Plant SBO site audit to qualitatively demonstrate that the St. Lucie Units 1 and 2 EDGs have sufficient capacity to qualify as AAC sources. Subsequent to that audit, FPL has conducted detailed task analyses and completed engineering calculations for the SBO event which have concluded that the St.

Lucie Unit 2 EDGs have sufficient capacity to operate equipment which may be required under SBO conditions. These load calculations and task analyses resulted in somewhat different equipment alignments from those of the NRC's SE.

Nonetheless, FPL will analyze plant response to the SBO event assuming that a maximum of 3936 kW is available to both units from the operating St. Lucie Unit 2 EDG. This analysis will be used to

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St. Lucie Units 1 and 2 Docket Nos. 50-335 and 50-389 Safet Evaluation on Station Blackout Rule(cont) conclude that acceptable plant response to an SBO event can be confirmed considering the St. Lucie Unit 2 UFSAR LOOP EDG load profile concurrent with the St. Lucie Unit 1 required SBO loads.

The analysis will confirm that these combined loads do not exceed 3936 kW and will include the blacked-out unit's (i.e., Unit 1) components considered in the NRC SE which FPL determines may be required during an SBO event. The ventilation studies described in FPL's response to the NRC Request for SE Section 2.3.4 above will determine which ventilation loads are required. Additionally, FPL will assume calculated running kW loads for each required component during the SBO event in liew of the worst-case design basis accident LOOP/LOCA EDG load values of the NRC's SBO SE.

These loads, and the plant response analyses to support their acceptability, will be included in the St. Lucie Unit 1 Updated Final Safety Analysis Report (UFSAR).

SBO Submittal Documentation In the staff's SE, various Requests state that FPL "...should...

include this information in the documentation supporting the SBO submittal that is maintained by the licensee." FPL intends to meet this aspect of the NRC's SBO SE for St. Lucie Unit 1 by incorporating the SBO evaluations and/or confirmations in the St.

Lucie Unit 1 Updated Final Safety Analysis Report (UFSAR).

As FPL has committed to meeting 10 CFR 50.63 by September 12, 1993, all SBO evaluations and/or confirmations will be included in the first annual UFSAR update subsequent to September 12, 1993 (i.e.,

July 21, '1994).

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