ML051020318

Licensees Slides for 04/11/2005 Summary of Category 1 Meeting with Entergy Corporation, to Discuss an Alternate Compliance Strategy for Meeting Fire Wrap Requirements in Certain Plant Areas

ML051020318
Person / Time
Site:	Grand Gulf
Issue date:	05/04/2005
From:	Bhalchandra Vaidya NRC/NRR/DLPM/LPD4
To:
vaidya B, NRR/DLPM, 415-3308
References
Download: ML051020318 (18)

Text

APRIL 11, 2005, MEETING ON AN ALTERNATIVE COMPLIANCE STRATEGY FOR MEETING GRAND GULF'S FIRE WRAP REQUIREMENTS GRAND GULF'S PRESENTATION SLIDES (FIGURES ON PAGES 10 AND 11 WITHHELD UNDER 10 CFR 2.390)

Pu rpose e Brief NRC on the methodologies to be used for a risk-informed, performance-based License Amendment Request for Grand Gulf Nuclear Station (GGNS) 1

=

Background===

• SECY 99-204 documented problems with Kaowool installations at Farley

• SECY identified issues were also applicable to Grand Gulf

• Initial efforts to re-qualify Kaowool deemed not feasible

• GGNS resolution strategy was to replace the Kaowool with 3M Interam wrap 2

Modification Status

• Control Building All wrap has been replaced.

• Containment Building

- All wrap has been replaced on the required MSIV circuits Alternate compliance strategy will eliminate need for wrap on Suppression Pool Temperature Monitoring 3

Modification Status

• Auxiliary Building: four elevations

- 3M wrap needed to support current fire modeling Kaowool.

results is being applied in place of

- Elevations 119' and 166' are complete

- Elevations 103' and 139' are in progress

- Where possible, Kaowool is being left in where the fire modeling does not dictate replacement (additional margin) place 4

Methodology

• Use of Performance-Based techniques to determine where cables are subject to damage from fire.

o Use of Risk-Insights as appropriate per guidance in Reg Guide 1.174 5

Goals &Assumptions

• MEFS half of LFS

• One train will be maintained free of fire damage.

• Kaowool wrap left on not credited to prevent cable damage, but will prevent fire growth.

• No credit for suppression.

• Transient Fire Package (MEFS)

- 350 kW Transient Fire

- - 50 Ibs burning at steady state 6

Performance-Based Methods

• Analytical Technique

- SFPE Guide and test data correlations for direct fire exposure to cable trays and equipment CFAST model to model indirect fire exposure (transient combustible storage areas) 7

Performance Criteria e The critical exposure values are as follows per NRC guidance for cables constructed of thermoset materials:

Critical surface temperature: 3290C (6250F)

Critical incident heat flux: 1 1.4 kW/m2 (1.0 Btu/s-ft2 )

- Failure of instrument and other equipment based on EQ criteria 8

Preliminary Study 119' Auxiliary Building

• Performed a risk-informed, performance based evaluation of the 119' Elev. of the Auxiliary Building

• Preliminary fire modeling results Some areas require wraps regardless of the methodology Other areas originally planned for wrap will not require any wrap 9

FIGURES ON PAGES 10 AND 11 WITHHELD UNDER 10 CFR 2.390

Results for El.

119'

• Cables installed in vertical trays protected to 15feet above the floor are not subject to damage from floor based transient fire.

• No fixed ignition sources capable-of causing damage to both divisions.

• Transient storage area (located --87feet away) will not generate hot gas layer that will damage equipment in the wrap areas.

12

Defense-i n-Depth

• Area in which wrap is installed is provided with ionization detection and a wet-pipe sprinkler system

• Area in which wrap is installed Is designated as a combustible-exclusion area

- Exclusion areas will be modified as required to maintain the analysis basis 13

Results Summary 14

Risk-Insights v Ignition Frequency From IMC 0609, assume area is "medium frequency" (1.7E-04)

Using weighting factor, scenario specific IF=3.17E-07

• CCDP

- Assumes unprotected division cables are damaged o No Credit for Automatic or Manual Suppression (PAS = 1.0 PMS 1 0 )

15

Scenario Specific CDF

• Scenario Specific CDF is 5.99E-10 for El.

119'

• Conservatism

- No credit for detection and suppression

- Assumes that half of fire area will not have transient combustibles present (i.e. plausible area is 50% of total fire area)

- No credit for combustible exclusion area 16

Results

• One train of Safe Shutdown Equipment is maintained free of fire damage e MEFS less than half LFS e CDF number for this elevation is within Region IV of Reg Guide 1.174 17

Conclusions

• Use of Risk-Informed, Performance-Based Methods Demonstrate that Strategic Use of 1-Hour Rated Barriers, in Conjunction with Defense-In-Depth Measures in Place, Provide an Acceptable Method to Achieve Safe Shutdown in the Event of Fire.

18