ML20012E868

Submits Supplemental Response to Station Blackout Rule Per NUMARC 900104 Request.One Change to Coping Assessment Calculation Was Necessary & Deviations from NUMARC 87-00 Methodology Identified

ML20012E868
Person / Time
Site:	Brunswick
Issue date:	03/30/1990
From:	Cutter A CAROLINA POWER & LIGHT CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
NLS-90-070, NLS-90-70, NUDOCS 9004060478
Download: ML20012E868 (3)

Text

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M b O LI$hl M y I P O. Bos 1661 w Haleegh, N C. 27s02 SERIAL NLS-90-070 MAR 3 0 990 JOCFR50.63 A. B CUTTER ,

vic. President l Nuclear Services Department  ;

United Stated Nuclear Regulatory Commission .;

ATTENTION: Document Con rol Desk Washington, DC 20555 BRUNSWICK STEAM ELECTRIC PLANT, UNIT NOS. 1 AND 2 i DOCKET NOS. 50-325 & $0-324/ LICENSE NOS. DPR-71 & DPR-62 ,

SUPPLEMENTAL. RESPONSE TO STATION BLACKOUT RULE Centlemen On March 3, 1989, Carolina Power & Light Company (CP&L) submitted a response to the Station Blackout (SBO) Rule (10CFR50.63) based on the guidelines provided in NUMARC 87-00, " Guidelines and Technical Bases for NUMARC i Initiatives Addressing Station Blackout at Light Water Reactors."

Representatives from the NRC Staff conducted a review of the background documents which supported the rule response during a visit to our facilities from June 27 to June 30, 1989. Based on the information exchanged during the review discussions, CP&L submitted a revised response to the SB0 Rule on  !

October 10, 1989. On January 4, 1990 NUMARC issued a letter request ing each utility to supplement the SB0 submittals to the NRC with a letter indicating ,

that either the previous response was based on use of the NUMARC 87-00 guidance, including the clarifications in the attachment to the January 4, 1990 NUMARC letter, or any deviation from the accepted NUMARC 87-00 guidance .

has been or will be clearly indicated. Carolina Power & Light Company has .

reviewed the January 4, 1990 NUMARC letter and our previous responses to the SB0 Rule for the Brunswick Steam Electric Plant, Unit Nos. 1 & 2 (BSEP).

Based on our review, one change to the coping assessment calculation was necessary and deviations f rom the NUMARC 67-00 methodology were identified.

The results of the review are detailed below.

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1. Change to Coping Assessment Calculation Condensate Inventory For Decay lleat Removal - Based on the additional clarification provided in the NUMARC letter, the maximum condensate l inventory was recalculated for the four hour coping period using an 18 ,

gpm leak rate for both recirculation pumps. The previous calculation l assumed a 25 gpm leak rate since there was no specific guidance  !

provided for BWR recirculation pumps. The recalculated maximum l inventory requirement is less than 98,000 gallons. The BSEP Technical l Specification condensate storage tank minimum inventory reserved for llPCI/RCIC operation is 103,738 gallons.

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2. Deviations from NUMARC 87-00 Culdelines and Methods Loss of Ventilation Assessment Methodology Average Wall Temperature

- The Control Room bestup calculation previously perf ormed used the inner wall temperature to determine the temperature rise. This was based on CP&L's interpretation of the NUMARC 87-00 approach as presented in Appendix E of NUMARC 87-00. Based on the clarification provided in question 2.5 of the NUMARC January 4, 1990 letter, CP&L's previous calculation now constitutes a deviation to the NUMARC 87-00 methodology.- However, CP&L believes that our calculation remains valid for the reasons described below.

The compartment heatup model derived in Appendix E of NUMARC 87-00 considers two heat loss paths for determining the bulk air temperaturet (1) heat loss by convection through open doors in the compartment, and (2) heat loss to the walls. For the BSEp Control Room, no openings in the compartment were considered. For the heat loss to the walls, NUMARC 87-00 conservatively represents the heat loss as being equal to the natural convection coef ficient between the air and the wall . This is a reasonable approach since a . transient analysis of a concrete surface would show that the concrete would allow a much higher heat flux than can be transferred between the air i

and the surface.t Therefore, for a short-term transient analysis, the-natural convection coefficient becomes the limiting heat loss mechani m. NUMARC 87-00 utilizes the Churchill and Chu correlation for establishing the free convection, which is based on the temperature difference between the air and the wall surface as defined by the Rayleigh number (Equation E-10 in NUMARC 87-00).

The above approach can be applied to transient analysis provided the wall has a high heat c.apacity (i .e., the surface temperature of the wall does not significantly rise over the duration of the analysis).

l This constraint applies regardless of the initial temperature profile through the wall. Temperature rise of the BSEP Control Room is not a i concern due to the high heat capacity of the wall (24" thick concrete) l in relationship to the duration of the analysis (1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />). The control room wall could have a temperature gradient of approxitaately ID F per inch (with the surface being close to the initial room temperature) which will have a negligible effect on the heat transferred to the surf aces with a bulk air temperature rise of 42"F over 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />.

l In addition, the control room heatup calculat ion deviated from the NUMARC 87-00 calculational method in that the calculational approach l generally followed the NUMARC 87-00 guidelines, except credit was j taken for the heat absorption capacity of the electrical equipment i cabinet surface steel.

In summary, the Company believes that the analysis performed for the control room is generally in accordance with the basis of the NUMARC 87-00 approach. The control room heatup calculation was reviewed by representatives from the NRC Staff during their visit to our facilities from June 27 to June 30, 1989.

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,. r Loss of Ventilation Assessment Methodology Pot ent ial Dominant Aseas '

of Concern - To document engineering judgement, heatup calculations were also perf ormed f or areas that had a potentially signifiosnt heat i

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s t>u r c e. Heatup calculations for the four-hour coping period were per f ornied for the service water pump area and the diesel generator building 480V switchgear rooms. The final temperature in the service water pump area was less than 130'r and less than 1l'O'r in the 480V 6witchgear rooms, so they were judged ret t o be dominant areas of concern because SB0 related equipment can operate in temperatures greater than 160*F.

3. Emergency Diesel Ceneratot (EDC) Target Reliabilly A target EDC ret! ability of 0.975 was selected for use in the evaluations based on the performance of the pl ant 's EDCs. It is CP6t.'s understanding that this target reliability is to be maintained consistent with the final resolution of Ceneric Issue B-56.

In suneary, Carolina Power & Light Comrany's previous SB0 submit tals for BSEp,

. as modif ied by this letter, are based on the guidelines provided in WUMARC 87-00 and the clarifications issued by WUMARC on January 4, 1990. Applica-bility of .the NUMARC 87-00 assumptions,is documented in our files. -

I If you should have any questions, please contact Mr. S. D. Floyd at (919) 546-6901.

Very gulyyoeg, A. B Cutter JCP/dsm (b$9ECC) cc Mr. S. D. Ebneter Mr. W. B. Le Mr. A. Marion (NUMARC)

Mr. W. 11. Rutand m