ML20211Q523

Forwards Request for Addl Info Re Submittal & 950728 Re IPEEE for Unit 3.Addl Info Re Fire Analyses in IPEEE Requested within 60 Days from Ltr Date

ML20211Q523
Person / Time
Site:	Waterford
Issue date:	10/20/1997
From:	Chandu Patel NRC (Affiliation Not Assigned)
To:	Dugger C ENTERGY OPERATIONS, INC.
References
TAC-M83692, NUDOCS 9710220332
Download: ML20211Q523 (7)

Text

.

October 20, 1997

- Mr. Charles M. Dugger

Vice-President Operations-

--Entergy Operations, Inc.-

P.'O.-Box B-Killona, LA 70066 f

SUBJECT:

REQUEST FOR ADDITIONAL INFORMATION:0N WATERFORD STEAM ELECTRIC STATION, UNIT-3 INDIVIDUAL PLANT EXAMINATION OF EXTERNAL EVENTS (IPEEE) SUBMITTAL (TAC NO.-M83692) ,

Dear Mr. Dugger:

The Nuclear Regulatory Commission'is reviewing your submittal dated

-December 29, 1994, as supplemented by letter dated July 28, 1995, regarding

IPEEE for Waterford Steam Electrk. Station, Unit 3. We would like to have additional information regarding fire analyses in IPEEE. Please provide your response to our enclosed request for information within 60 days from the date of- this letter. Please contact me if you have any questions.

Sincerely, ORIGINAL SIGNED BY:

Chandu P. Patel, Project Manager 5

-Project Directorate IV-1 Division of Reactor Projects III/IV Office of Nuclear Reactor Regulation Docket-No. 50-382

Enclosure:

- . Request for Additional Information -

cc w/ encl: See next page DISTRIBUTION:

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• s*****/ October 20, 1997 Mr. Charles M. Dugger Vice President Operations Entergy Operations, Inc.

P. O. Box B Killona, LA 70066

SUBJECT:

REQUEST FOR ADDITIONAL INFORMATION ON WATERFORD STEAM ELECTRIC STATION, UNIT 3 INDIVIDUAL PLANT EXAMINATION OF EXTERNAL EVENTS (IPEEE) SUBMITTAL (TAC NO. M83692)

Dear Mr. Dugger:

The Nuclear Regulatory Commission is reviewing your submittal dated December 29, 1994, as supplemented by letter dated July 28, 1995, regarding IPEEE for Waterford Steam Electric Station, Unit 3. We would like to have additional information regarding fire analyses in IPEEE. Please provide your response to our enclosed reque::t for information within 60 days from the date of this letter. Please contact me if you have any questions.

Sincerely, fhw Chandu P. Patel, Project Manager Project Directorate IV-1 Division of Reactor Projects III/IV Office of Nuclear Reactor Regulation Docket No. 50-382

Enclosure:

Request for Additional Information cc w/ encl: See next page r

Mr. Charles H. Dugger Enteigy Operations, Inc. Waterford 3 cc:

Administrator Regional Administrator, Region IV Louisiana Radiation Protection Division U.S. Nuclear Regulatory Commission Post Office Box 82135 611 Ryan Plaza Drive, Suite 1000 Baton Rouge, LA 708B4-2135 Arlington, TX 76011 Vice President, Operations Resident Inspector /Waterford NPS Support Post Office Box 822 Entergy Operations, Inc. Killona, LA 70066 P. O. Box 31995 Jackson, MS 39286 Parish President Council St. Charles Parish Director P. O. Box 302 Nuclear Safety & Regulatory Affairs Hahnville, LA 70057 Entergy Operations, Inc.

P. O. Box B Executive Vice-President Killona, LA 70066 and Chief Operating Officer Entergy Operations, Inc.

Wise, Carter, Child & Caraway P. O. Box 31995 P. O. Box 651 Jackson, MS 39286-1995 Jackson, h5 39205 Chai rmat.

General Manager Plant Operations Louisiana Public Service Commission Entergy Operations, Inc. One American Place, Suite 1630 P. O. Box B Baton P.ouge, LA 70825-1697 Killona, LA 70066 Licensing Manager Entergy Operations, Inc.

P. O. Box B Killona, LA 70066 Winston & Strawn 1400 L Street, N.W.

Washington, DC 20005-3502 I

. . . _ . . . - . ~ . _ . . _ _ . . _ _ _ . _. ._.

{L1

Waterford Generating Stati:n, Unit 3 Request for Additional Information (RAI) on IPEEE Submittal Fire events-

l. In_ the Electric Power Research Institute (EPRI) Fire Probabilistic Risk Animaamant (PRA)

Implementation Guide, test results for the control cabinet heat reinase rates beve been misinterpreted and have been inappropriately extrapolated. Cabinet best release rates as low as 65 Btu /sec are used in the guide. In contrast, experimental work has developed heat release rates ranging from 23 to 1171 Btu /sec.

Considering the range of heat release rates that could be applicable to.different cabinet

. 6res, and to ensure that cabinet 6re areas are not prematurely screened out of the analysis, a heat release rate in the mid range of the currently available experimental data (e.g., 550 Btu / soc) should be used for the analyds.

Discuss the heat release rates used in your assessment of control cab' met 6res. Please provide a discussion of changes in the IPEEE Are assessment results ifit is assumed that the heat release from a cabinet fire is increased to $50 Btu /s.

2. Fires 60m both 6xed and transient combustible ignition sources can be significant contributorz to the fire-related risk at a nuclear power plant, fhe screening of 6re areas and the final quantitative 6te assessn:ent should consider both of these types of fire sources.

'- Transient combustible (TC) Gres were not described for the unscreened areas analyzed in the PRA evaluation which contained fixed ignition sources. Indicate ifTC Gres were considered in the detailed PRA evaluation for these areas and provide the impact of TC 6tes in applicable Sre areas on the overall core damage frequency.

3. It would appear that the frequency of fires in the switchgear fire areas has been inappropriately partitioned, in particular, the DEEE has reduced the ignition frequency for an individual switchgear pane! by over three orders of magnitude based on the assumption that there are over 1000 switchgear panels at the plant. Then, for quantification purposes, only a very few of these panels are considered as signi6 cant risk contributors. While there may be over 1000 general electrical panels in the plant, it appears improbable to postulate that there are in fact over 1000 switchgear panels at this plant. The generic switchgear fire frequency cited in the study derives only from actual switchgear fires, and 1.ence, the corresponding panel count should only include switchgear panels.

Please (1) describe how the switchgear panels were counted and what criteria were used to define an individual panel, (2) describe how was it determined which of the individual panels would represent potential risk contributors, and (3) what would be the total ENCLOSURE

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e contribution to core damage frequency if the contributions nom all panels were summed without the screening ofindividual panel scenarios based on low frequency of contribution.

4. Fine zone RAB.16 was not screened in the qualitative assessment but was not includd in the PRA evaluation. Provide a brief discussion on the core damage frequency results from this zone.

5. De Fire-Induced Vulnerability Evaluation (FIVE) Sre modelu ; methods were useil to calculate the total heat release for some Sre scenarios and compared to the critical total heat releases required for component damage. The submittalindicates that the FIVE Gre modeling technique is conservative. One important factor in validating this assertion is the heat loss factor used in the analyses.

i-The heat loss factor is defined as the fraction of energy released by a fire that is transferred to the enclosure boundaries. This is a key puameter in the prediction of component damage, as it determines the amount ofheat available to the hot gas layer. In FIVE, the heat loss factor is modeled as being inversely related to the amount of heat required to cause a given temperature rise. Thus, for example, a larger heat loss factor means that a larger amount of heat (due to a more severe 6re, a longer buming ti:ne, or both) is needed to cause a given temperature rise. It can be seen that if the value assumed for the heat loss factor is unrealistically high, Sre scenarios can be improperly screened out. Figure 1 provides a representative example of how hot gas layer temperature predictions can change assuming different heat loss factors. Note that: 1) the curves are computed for a 1000 kW Gre in a 10m x Sm x 4m compedmer.t with a forced ventilation rate of 1130 cfm;

2) the FIVE-recommended damage temperature for quali6ed cable is 700*F for qualified cable and 450'F for unquali6ed cable; and, 3) the Society for Fire Protection Eapa-s (SFPE) curve in the Sgure is peaerated from a correlation provided in the SFPE Handbook.

The FIVE methodology recommends the use of a heat loss factor of 0.7 as a conservative value, and 0.85 as a realistic value. The difference between these two factors is a factor of two (0.3 versus 0.15) in terms of heat available to cause fire damage. Reference 1, which documents the results ofmulti-compartment fire experiments, indicates her.t loss factors on the order of 0.51 to 0.74 are appropriate when analyzing a single compartment fire (higher heat loss factors are appropriate when the hot 3.s layer moves fkom the burning companment to adjacent companments). In summary, (a) hot gas layer predictions are very sensitive to the assumed value of the heat loss factor, and (b) large heat loss factors cannot be justi6ed for single-room scenarios.

Ten of the fire scenarios evaluated using the FIVE fire modeling were reported as resulting in total heat release within 88 99% of the critical total heat release required for cable damage and were thus screened from further analysis. Please indicate what heat loss factors were used in the fire modeling assessments. In light of the preceding discussion, w ~ ~-.,~. _ ,.v ~ - , . _ . - - - - - .- -

please either: a) justify the value used and discuss its effect on the identification of fire vulnerabilities, or b) repeat the analysis using a more justifiable value and provide the I resulting change in scenario contribution to core damage frequency. l

. 1 l

Reference- t i

1. L. Y. Cooper, M. Harkleroad, J. Quintiere, W. Rinkinen, "An Experimental Study  ;

of Upper Hot Layer Stratification in Full-Scale Multiroom Fire Scenaries," ASME ,

1 Jourt.) of Heat Transfer, .1M, 741-749, November 1982. ,

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