ML17250B240

TMRE LAR Pre-Submittal Meeting with NRC

ML17250B240
Person / Time
Site:	Vogtle
Issue date:	08/30/2017
From:	Gilbreath A, Lowery K Southern Nuclear Operating Co
To:	Office of Nuclear Reactor Regulation
Brown E
References
Download: ML17250B240 (24)

Text

NRC Pre-Submittal Meeting Vogtle Electric Generating Plant - Units 1&2 License Amendment Request to Incorporate Tornado Missile Risk Evaluator into the Licensing Basis August 30, 2017 Prepared by Alex Gilbreath and Ken Lowery

Proposed Licensing Action

• Revise the VEGP Units 1 & 2 licensing basis for protection from tornado-generated missiles addressing certain tornado missile protection nonconforming conditions

• Revise the FSAR to

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

- Describe the results of the plant specific tornado missile hazard analysis using the TMRE methodology for those nonconforming conditions 2

Schedule

• Multiple NRC & Industry Public Meetings Since 2015

• NEI 17-02, Revision 0 (Tornado Missile Risk Evaluator)

- Issued: June 2017

- NRC Public Meeting: July 6, 2017

- NRC Public Meeting: August 17, 2017

• VEGP Pilot

- Fee-waiver Approval: July 2017

- Pre-Submittal Meeting: August 30, 2017

- Planned Submittal Date: September 29, 2017

- Requested Approval Date: May 29, 2018 3

Preliminary Bases of Proposed Licensing Action

• Technical

• Safety

• No Significant Hazards Consideration

• Environmental 4

Technical

• Requested an amendment to the license for the application of the TMRE methodology for tornado missile risk analysis

• TMRE methodology was used to demonstrate that specific plant features that are currently unprotected at VEGP do not require additional engineered missile protection barriers due to the low risk associated with tornado missile damage

• The requested changes 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 5

Technical Nonconformances

• MSSV Exhausts

• ARV Exhaust Stacks

• ARV

• TDAFW Exhaust

• CST Vents 6

Technical TMRE Evaluation

• Standard PRA practices used for non-TMRE specific analyses

• No deviations from TMRE guidance were identified

• Missile count assumption in TMRE is not bounding - Site missile count of approximately 410,000 > 240,000

• Site-specific tornado hazard curve developed 7

Technical 8

Technical TMRE Evaluation Example Exposed Equipment Failure Probabilities Turbine Driven Aux Feed Pump exhaust pipe Elevation: < 30 Robust type J (Not Robust)

Intensity Basic Event MIP #Missiles SA (sq.ft.) EEFP F'2 TMRE-F2-TDAFWVENT 1.10E-10 160,000 12 2.11E-04 F'3 TMRE-F3-TDAFWVENT 3.60E-10 310,000 12 1.34E-03 F'4 TMRE-F4-TDAFWVENT 6.30E-10 380,000 12 2.87E-03 F'5 TMRE-F5-TDAFWVENT 1.60E-09 400,000 12 7.68E-03 F'6 TMRE-F6-TDAFWVENT 2.40E-09 410,000 12 1.18E-02 9

Technical TMRE Evaluation - PRA Modeling

• Selected operator actions failed - Examples Event Name Description OA-N1EBATCHG-H Operator fails to put the standby non 1E battery charger to service OA-DEP-SBO---H Operator fails to depressurize SG in SBO - local ARV operation OA-PW-CTSDG----H Operator fails to start PW CTS (or the black start DG) & energize SAT

• Selected equipment failed from high winds equipment List - Examples Event Name Description RAT A supply breaker AA0205 to 4160V BUS AA02 1ACCBAA0205--U spuriously opens RAT B supply breaker BA0301 to 4160V BUS BA03 1ACCBBA0301--U spuriously opens 10

Technical TMRE Evaluation Results Top Event F Cat. Compliant Cases Degraded Cases Cases Sum F % of Total F'2 1.461E-08 2.553E-08 1.092E-08 25.1%

F'3 3.877E-09 9.481E-09 5.604E-09 12.9%

CDF F'4 1.076E-09 5.665E-09 4.589E-09 4.357E-08 10.5%

F'5 2.683E-10 1.780E-08 1.753E-08 40.2%

F'6 1.574E-11 4.935E-09 4.919E-09 11.3%

F'2 1.759E-11 1.394E-10 1.218E-10 13.9%

F'3 4.099E-12 1.371E-10 1.330E-10 15.2%

LERF F'4 9.137E-13 1.372E-10 1.362E-10 8.779E-10 15.5%

F'5 1.338E-13 3.971E-10 3.970E-10 45.2%

F'6 0.000E+00 8.982E-11 8.982E-11 10.2%

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Safety

• Once information about the sites non-conforming targets and other missile vulnerabilities were collected, a TMRE model, based on the VEGP Units 1 & 2 PRA internal events model of record was used to assess the change in CDF and LERF.

• The results show that the overall change in risk for both the permanent missile count and temporarily increased missile count are acceptable when compared to RG 1.174 Region III guidelines.

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No Significant Hazards Consideration

• As required by 10 CFR 50.91(a)(1), it has been determined that the proposed amendment does not involve a significant hazards consideration using the standards of 10 CFR 50.92(c) 13

Environmental

• The proposed amendment meets the eligibility criterion for categorical exclusion set forth in 10 CFR 51.22(c)(9)

• Therefore, pursuant to 10 CFR 51.22(b), no environmental impact statement or environmental assessment need be prepared in connection with the proposed amendment 14

NRC Regulatory Guidance

• 10 CFR 100.10 (Evaluation Factors for Stationary Power Reactor Site Applications Before January 10, 1997 and for Testing Reactors)

• 10 CFR 50 Appendix A - General Design Criteria

- GDC-2 (Design Basis for Protection Against Natural Phenomena)

- GDC-4 (Environmental and Dynamic Effects Design Basis)

• Regulatory Guide 1.13 (Spent Fuel Storage Facility Design Basis)

• Regulatory Guide 1.27 (Ultimate Heat Sink for Nuclear Power Plants)

• Regulatory Guide 1.76 (Design Basis Tornado and Tornado Missile for Nuclear Power Plants)

• Regulatory Guide 1.117 (Tornado Design Classification) 15

NRC Generic Communications

• NRC Regulatory Issue Summary 2015-06, June 10, 2015 (Tornado Missile Protection)

Related Guidance:

• Enforcement Guidance Memorandum 15-002, Revision 1, February 7, 2017 (Enforcement Discretion For Tornado Generated Missile Protection Non-compliance)

• DSS-ISG-2016-01, Interim Staff Guidance, February 2016 (Clarification of Licensee Actions in Receipt of Enforcement Discretion Per Enforcement Guidance Memorandum EGM 15-002, Enforcement Discretion for Tornado-Generated Missile Protection Noncompliance) 16

Facility Specific Licensing Basis GDC-2 (VEGP FSAR 3.1.1)

• Structures, systems, and components important to safety shall be designed to withstand the effect 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:

1. 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 accuracy, quantity, and period of time in which the historical data have been accumulated

2. appropriate combinations of the effects of normal and accident conditions with the effects of the natural phenomena

3. the importance of the safety functions to be performed 17

Facility Specific Licensing Basis GDC-4 (VEGP FSAR 3.1.1)

• Structures, systems, and components important to safety are designed to accommodate the effects of and to be compatible with the environmental conditions associated with normal operation, maintenance, testing, and postulated accidents, including the design basis LOCA

• These structures, systems, and components are appropriately protected against dynamic effects and discharging fluids that may result from equipment failures

• Normal and postulated accident effects and load combinations are given in sections 3.6, 3.8, 3.9, and 3.10

• Special attention was directed to the effects of pipe movement, jet forces, and missiles within the primary containment. Pipe whip restraints have been provided to the extent practical

• The structures, systems, and components important to safety are protected from dynamic effects by separating redundant counterparts so that no single event can prevent a required safety action and by routing and locating, to the extent practical, these components to avoid potentially hazardous areas

• Dynamic effects external to the plant, induced by natural phenomena, i.e., tornado-produced missiles, are appropriately considered in section 3.5 18

Facility Specific Licensing Basis Regulatory Guide 1.13 Fuel Storage Facility Design Basis (December, 1975)

FSAR 1.9.13

• Conform, with exception to regulatory position C.7, as the spent fuel pool level indicator alarms in the control room only, and not locally

• Additional information is given in FSAR 9.1 19

Facility Specific Licensing Basis Regulatory Guide 1.27 Ultimate Heat Sink For Nuclear Power Plants (Revision 2, January 1976)

FSAR 1.9.27

• Conformance with this guide is given in FSAR 9.2.5 20

Facility Specific Licensing Basis Regulatory Guide 1.76 Design Basis Tornado For Nuclear Power Plants (April 1974)

FSAR 1.9.76

• Conformance with this guide is given in FSAR 3.3

• The tornado design parameters for (RG 1.76) Region 1 are used for VEGP 21

Facility Specific Licensing Basis Regulatory Guide 1.117, Revision 1 Tornado Design Classification (April 1978)

FSAR 1.9.76

• Conform, with exception of the nuclear service cooling water tower fans which are not missile protected

• Refer to section 3.5 22

Facility Specific Licensing Basis 23

Industry Guidance

• NEI 17-02 (Tornado Missile Risk Evaluator) 24