ML17283A412

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Meeting Slides - October 10, 2017 Pre-Application Meeting with Grand Gulf Concerning Tornado Missile Risk Evaluator Submittal
ML17283A412
Person / Time
Site: Grand Gulf Entergy icon.png
Issue date: 10/10/2017
From: Siva Lingam
Special Projects and Process Branch
To:
Entergy Operations
Lingam S, 301-415-1564
References
Download: ML17283A412 (29)
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Text

Grand Gulf TMRE LAR Pre-submittal Meeting October 10, 2017

1 Agenda

  • Purpose
  • Grand Gulf Team
  • Current Licensing Basis
  • Proposed License Action
  • Schedule
  • Conclusion

1 Purpose Introduction of License Amendment Request for NRC approval of TMRE methodology at Grand Gulf Nuclear Station

1 Entergy / Grand Gulf Participants J Hallenbeck, Special Projects Manager D Neve, Regulatory Assurance Manager J Nadeau, Corporate Regulatory Assurance R Harris, PRA Engineer R Millison, Corporate Risk Informed Application Manager

1 Grand Gulf Unit 1

  • Bechtel prime contractor
  • Construction Permit issued September 4, 1974
  • Operating License issued November 1,1984
  • Commercial operation began July 1, 1985
  • Improved Technical Specifications

1 Facility Specific Licensing Basis 3.1.1 Summary Description This section contains an evaluation of the design bases of the plant as measured against the NRC General Design Criteria for Nuclear Power Plants, Appendix A of 10 CFR 50 effective May 21, 1971, and subsequently amended July 7, 1971.

3.1 CONFORMANCE WITH NRC GENERAL DESIGN CRITERIA Based on the content herein, SERI concludes that the nuclear power plant fully satisfies and is in compliance with the General Design Criteria.

From the Grand Gulf UFSAR

1 Facility Specific Licensing Basis 3.1.2.1.2 Criterion 2 - Design Bases for Protection Against Natural Phenomena Structures, systems, and components important to safety shall be designed to withstand the effects of natural phenomena such as earthquakes, tornadoes, hurricanes, floods, tsunami, and seiches without loss of capability to perform their safety functions. The design bases for these structures, systems, and components shall reflect:

a. Appropriate consideration of the most severe of the natural phenomena that have been historically reported for the site and surrounding area, with sufficient margin for the limited data that have been accumulated
b. Appropriate combinations of the effects of normal and accident conditions with the effects of the natural phenomena
c. The importance of the safety functions to be performed From the Grand Gulf UFSAR (cont.)

1 Facility Specific Licensing Basis Bechtel Topical Report BC-TOP-3A, Revision 3, August 1974, Tornado and Extreme Wind Design Criteria for Nuclear Power Plants.

ASCE Paper No. 3269, Wind Forces on Structures, Transactions of the American Society of Civil Engineers, Volume 126, Part II (1961).

Regulatory Guide 1.76 Revision 0 Design-Basis Tornado and Tornado Missiles for Nuclear Power Plants (April 1974)

Grand Gulf is considered in Region 1

1 Facility Specific Licensing Basis Wood plank 4 in x 12 in x 12 ft 115 272 Steel Pipe, 6 in diameter, schedule 40, 15 ft long 286 170 Steel rod, 1 in diameter, 3 ft long 9

167 Utility pole, 13.5 in diameter, 35 ft long 1,123 180 Steel pipe, 12 in diameter, schedule 40, 15 ft long 749 154 Automobile 20 ft contact area 3,991 194 Missile Weight lbs Horizontal Velocity, fps Grand Gulf Missiles Generated by Natural Phenomena

1 Proposed Licensing Action

Identify TMRE as the methodology used for assessing tornado-generated missile protection of nonconforming SSCs existing prior to submittal of the LAR.

Describe the results of the plant specific tornado missile hazard analysis using the TMRE for those nonconforming conditions.

Methodology would not be used for future design modifications.

1 Basis of Proposed Licensing Action

  • Technical
  • Safety
  • No Significant Hazards Consideration
  • Environmental

1 Technical Request an amendment to the Grand Gulf license for the application of the TMRE methodology (NEI 17-02, Revision 1) for tornado missile risk analysis The TMRE methodology was used to demonstrate that plant identified vulnerabilities do not require engineered missile protection barriers due to the low risk associated with tornado missile damage The requested change would revise the licensing and design bases as described in the FSAR by adding a description of the TMRE methodology utilized for determining the acceptability of tornado missile protection for those SSCs determined to be nonconforming prior to the submittal of the LAR PRA values are current but considered preliminary

1 Technical Vulnerability General Location Diesel Generator Fuel Oil Storage Tank Vents and Inlets Yard (above underground Diesel Generator Fuel Oil Storage Tanks)

Standby Service Water (SSW)

Cooling Tower Fanstacks (Top Grating)

SSW Cooling Tower Basin at Gridlines B2, B3, C2, C3, C6, & C7 SSW Vertical Piping between Basins and SSW Superstructures SSW Cooling Tower Basin at Gridlines B2, B3, C2, C3, C6, & C7 Control Building HVAC Outside Air Intake Louver/Damper (Penetration CV-4H)

Control Building (Centerline of louver at El. 208'-8")

Control Building Elevator Machine Room Intake Air Damper (Penetration CV-2H)

Control Building, Elevator Machine Room (damper centerline at EL.

212'-4")

Control Building Elevator Machine Room Service Door (Door OC801)

Control Building, Elevator Machine Room (door at El. 207'-6")

Control Building Elevator Machine Room Exhaust Air Check Damper (Penetration CV-3H)

Control Building, Elevator Machine Room (damper centerline at El.

212'-4")

Grand Gulf Identified Vulnerabilities

1 Technical Vulnerability General Location Eighty-one (81) 6" dia. Openings in Control Building North Wall Control Building, North Wall Control Building Stairwell Door (Door OCT5)

Control Building (door at El. 133'-0")

Diesel Generator Exhaust Pipes (Penetrations DP-16A, DP-17A, DP-18A, and DP-19A)

Diesel Generator Building (roof El.

172'-0")

Diesel Generator Lube Oil Sump Vents (Penetrations DP-20A and DP-21A)

Diesel Generator Building (roof El.

172'-0")

Diesel Generator Fuel Oil Day Tank Vents (Penetrations DC-20A, DC-21A, and DC-22A)

Diesel Generator Building (roof El.

172'-0")

SSW Supply and Return Headers (Penetrations DP-1A and DP-2A)

North End of Breezeway between Diesel Generator Building and Auxiliary Building Three (3) Cable Tray Supports at South End of Breezeway South End of Breezeway between Diesel Generator Building and Auxiliary Building Grand Gulf Identified Vulnerabilities (cont.)

1 Technical Vulnerability General Location Cable Chase Room 1A539 (Behind Door 1A501)

South End of Control Building (Access gained from the Auxiliary Building Roof)

SSW Valve Room Doors 1M112 and 2M112 and Pump House Doors 1M110 and 2M110 SSW Basins A & B Diesel Generator Crank Case Vents (Penetrations DP-22A and DP-23A)

Diesel Generator Building (roof El.

172'-0")

Control Building Lobby Door (Door OC313)

Control Building (door at El. 133'-0")

Grand Gulf Identified Vulnerabilities (cont.)

1 TMRE Evaluation No deviations from TMRE guidance were identified Site-specific tornado hazard curve developed The NEI 17-02 missile count was bounding Exposed Equipment Failure Probabilities (EEFPs) were adjusted to account for robust target missile reduction per NEI 17-02 Operator actions were evaluated per NEI 17-02 guidance Technical

16 1

Technical y = -21.93ln(x) - 57.667 R² = 1 100 120 140 160 180 200 220 240 260 280 300 1.00E-08 1.00E-07 1.00E-06 1.00E-05 1.00E-04 1.00E-03 Tornado Probability Grand Gulf Tornado Hazard Curve

1 Technical Fujita Prime (F)

Category Range, MPH Initiating Event Frequency F2 103-135 5.05E-04 F3 135-168 1.19E-04 F4 168-209 2.87E-05 F5 209-277 5.00E-06 F6 277-300 2.36E-07 GGNS Plant Specific Initiating Event Frequency

1 Technical CDF/year LERF/year Compliant 5.89E-07 2.72E-08 Degraded 8.13E-07 5.06E-08 Delta 2.25E-07 2.34E-08 Initiating Event Frequency

% CDF Contribution Compliant

% CDF Contribution Degraded Description

%GG-T-F2 5.05E-04 74.9%

58.0%

GGNS FREQ FOR F'2 TORNADO

%GG-T-F3 1.19E-04 18.6%

17.9%

GGNS FREQ FOR F'3 TORNADO

%GG-T-F4 2.87E-05 5.0%

8.3%

GGNS FREQ FOR F'4 TORNADO

%GG-T-F5 5.00E-06 1.5%

13.9%

GGNS FREQ FOR F'5 TORNADO

%GG-T-F6 2.36E-07 0.1%

2.0%

GGNS FREQ FOR F'6 TORNADO TMRE Evaluation - Quantification Results Initiating Event Contribution

1 Technical CDF/year LERF/year Compliant 5.89E-07 2.72E-08 Degraded 8.14E-07 5.07E-08 Delta 2.25E-07 2.35E-08 De Minimis Penetration Sensitivity Eighty-one 6-inch diameter penetration vulnerabilities through the North wall of the un-completed Unit 2 portion of the control building.

De Minimis Sensitivity Results

1 Technical CDF /year LERF /year Compliant 5.89E-07 2.72E-08 Degraded 1.08E-06 8.08E-08 Delta 4.88E-07 5.36E-08 Zonal VS. Uniform Missile Distribution Sensitivity Sensitivity addresses the potential underestimation of target hit probability due to the missile distribution at the GGNS site.

Sensitivity evaluates SSCs with a tornado missile failure basic event RAW 2 and only applies to basic events for tornado categories F4, F5 and F6.

1 Technical CDF /year LERF /year Compliant 5.89E-07 2.72E-08 Degraded 9.96E-07 7.19E-08 Delta 4.07E-07 4.47E-08 Missile Impact Parameter sensitivity Sensitivity addresses the potential underestimation of target hit probability due to SSCs located or oriented in a way that exposes them to a higher than average missile impact parameter (MIP).

Sensitivity evaluates highly exposed SSCs with a tornado missile failure basic event RAW 2 and only applies to basic events for tornado categories F4, F5 and F6.

1 Technical Modeling Conservatisms Potential that conservative assumptions can mask delta risk estimates.

Potential to have a larger impact on the compliant model, resulting in under estimating delta risk by over estimating the compliant model risk.

This conservatism can be bounded by performing a single sensitivity where the compliant risk model results are set to zero.

CDF/year LERF/year Degraded 8.13E-07 5.06E-08 Compliant 0

0 Delta Risk 8.13E-07 5.06E-08

1 Safety The total change in risk associated with tornado missile damage to non-conforming conditions identified at Grand Gulf results in a risk increase of 2.25E-07 per year CDF and 2.34E-08 per year LERF.

The tornado risk change for accepting GGNS non-conforming conditions results in a very small risk increase per RG 1.174 Rev 2.

1 No Significant Hazards Consideration As required by 10CFR 50.91 (a)(1), the proposed amendment does not involve a significant hazards consideration using the standards of 10CFR50.92(c).

1 Environmental

  • The proposed amendment meets the eligibility criterion for categorical exclusion set forth in 10CFR51.22(c)(9)
  • Therefore, pursuant to 10CFR51.22(b), no environmental impact statement or environmental assessment need be prepared in connection with the proposed amendment

1 Schedule Grand Gulf Pilot

  • Fee-waiver approved: July 2017
  • Planned Submittal Date: October 26, 2017
  • Requested Approval Date: June 29, 2018

1 Conclusion

  • No deviations from TMRE methodology were identified
  • LAR will address the five principles of risk-informed decision making RG 1.174 Meets current regulations Consistent with and maintains defense-in-depth Maintains safety margins Increase in risk is small and consistent with NRC Safety Goal Policy Impact will be monitored
  • PRA quality - No open findings on internal events model

1 Questions

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