ML18227B321
| ML18227B321 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 09/05/2018 |
| From: | Duke Energy Carolinas |
| To: | Division of Operating Reactor Licensing |
| Klett A | |
| References | |
| Download: ML18227B321 (17) | |
Text
Oconee Nuclear Station Tornado License Amendment Pre-Application Meeting One White Flint, Rockville, MD August 1, 2018
Attendees Duke Attendees:
David A Baxter (Dave) ONS Regulatory Projects Timothy D Brown (Tim) ONS Regulatory Projects Jason A Patterson (Jason) ONS Regulatory Projects Philip J North (Phil) ONS Regulatory Projects David A Wilson (David) ONS Design Basis Lee M Kanipe (Lee) Fleet Probabilistic Risk Assessment Michael E Henshaw (Eric) Fleet Safety Analysis 2
Agenda Opening Remarks Oconee Tornado Current License Basis (CLB) 2018 Tornado License Amendment Request (LAR)
Discussion of LAR Closing Remarks 3
Opening Remarks To clarify the tornado license basis, ONS intends to submit a license amendment that will seek NRC review and approval of the following:
Crediting the standby shutdown facility (SSF) as the assured mitigation path following a tornado with damage from the tornado assumed to be loss of all alternating current (AC) power to all units with significant damage to one unit.
Formal incorporation of the use of tornado missile probabilistic methodology (TORMIS) in the ONS tornado license basis and associated UFSAR changes.
Elimination of the spent fuel pool (SFP) to high pressure injection (HPI) flow path for reactor coolant makeup (RCMU) from the license basis.
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Tornado CLB Tornado is not defined as a design basis event, or scoping event in the CLB.
In the original licensing of the plant, no event analysis for tornado was completed and no safe shutdown sequences were determined.
Protection from the effects of a tornado is established as a design criterion for select systems, structures, and components (SSCs).
Physical tornado protection of Class 1 structures (e.g. reactor building, and portions of the auxiliary building) is provided.
Redundancy, diversity, and physical separation credited to assure:
Source of power and associated pathway to the unit.
Source of secondary side decay heat removal and associated pathway to the unit.
Source of primary makeup and associated pathway to the unit.
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Proposed Tornado LB Protection from the effects of a tornado will remain as a design criterion for credited systems, structures, and components (SSCs).
However, analyses have been completed that demonstrate the plants ability to mitigate a tornado using the SSF and procedures will be revised to reflect this capability.
Physical tornado protection of Class 1 structures (e.g. reactor building, and portions of the auxiliary building) will remain.
Redundancy, diversity, and physical separation of mitigating components/systems will no longer be credited, however redundant/diverse components/systems may be used if available.
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Proposed 2018 Tornado LAR Proposed LAR supersedes LAR submitted in 2008.
Credits the SSF as the one deterministically protected path for tornado mitigation within its 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> mission time.
All units experience a loss of AC power with one unit experiencing significant damage from the tornado.
Significant damage defined as either a main feedwater line break (overheating event) or main steam line break (overcooling event).
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Proposed 2018 Tornado LAR Implementation of TORMIS as an acceptable method for evaluating systems and components necessary for the SSF to fulfill its credited mission that are not physically protected from tornado induced missiles:
SSF related systems and components located in the west penetration and cask decontamination tank rooms (WPR and CDTR, respectively).
Other systems and components required for the SSF to fulfill its design function (MSRVs, spent fuel cooling piping, CCW surge lines, etc.).
Committed modifications routed in areas of the WPR and CDTR.
Results: All units <1x10-06 per reactor year with conservatisms.
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Proposed 2018 Tornado LAR Credits completed modifications:
Protection of BWST for tornado wind and missiles.
Protection against wind loads and DP using fiber reinforced polymer (FRP) on the west penetration rooms (WPRs) and cask decontamination tank rooms (CDTRs).
Protection of SSF south side double doors for tornado missiles.
Protection from tornado missile impacts through the SSF south side personnel access stairwell on the SSF ASW lines.
Protection from tornado missiles through miscellaneous SSF exterior penetrations.
Protection of SSF north end cable trench cover and SSF trench crossover of CT-5 trench for tornado missiles.
Protection of SSF diesel service water discharge piping for tornado missiles.
Protection of SSF diesel fuel oil tank vent for tornado missiles.
Unit 2 & 3 SSF RCMU replacement pulsation dampeners.
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Proposed 2018 Tornado LAR Credits future modifications:
Missile protection of the SSF diesel fuel oil tank vent and fill lines to prevent shear/perforation of the piping and potential rain water intrusion.
Unit 1 SSF RCMU replacement pulsation dampener.
New SSF letdown line for each unit.
Enhanced SSF system instrumentation, including:
Individual steam generator pressure.
Wide range neutron flux.
Pressurizer temperature.
Does not seek NRC review and approval of these modifications (they will be evaluated via 50.59).
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Proposed 2018 Tornado LAR Licensing Document Changes Significant rewrite of UFSAR description of tornado mitigation:
Establishes initial condition of significant tornado damage to one unit with all units experiencing a loss of all AC power.
Credits SSF as assured mitigation path.
Establishes success criteria for RCS conditions following a tornado.
Applies TORMIS to evaluate SSF support systems and components that are not physically protected for tornado missiles.
Eliminates SFP suction source for HPI from license basis.
No anticipated changes to Technical Specifications.
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Proposed 2018 Tornado LAR Thermal hydraulic success criterion for the RCS following a tornado:
Main feedwater line breaks (overheating events):
Core remains intact and in a cool-able geometry.
RCS pressure < 2750 psig.
Minimum departure from nucleate boiling ratio (DNBR) meets specified acceptable fuel design limits.
Main steam line breaks (overcooling events):
Core remains intact and in a cool-able geometry.
The steam generator (SG) tubes remain intact.
The RCS remains within acceptable pressure and temperature limits.
Minimum DNBR meets specified acceptable fuel design limits.
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Discussion of Tornado LAR LAR Composition (NEI 06-02 guidelines)
Cover Letter Enclosure 1.0 Summary Description 2.0 Detailed Description
- SSF System Description
- Tornado CLB
- Reason for Proposed Changes
- Description of Proposed Changes
- UFSAR Changes 13
Discussion of Tornado LAR LAR Composition / continued Enclosure / continued 3.0 Technical Evaluation
- RCS T-H Analysis
- Revised Tornado LB
- Operations Tornado Response, Training, and Procedures
- Other Safety Considerations
- Corrosion Effects
- TORMIS Methodology
- Passive Civil Features 4.0 Regulatory Evaluation 14
Discussion of Tornado LAR LAR Composition / continued Attachments Regulatory Commitments UFSAR Markups UFSAR Retypes Tornado Missile Probabilistic Methodology (TORMIS) Thermal Hydraulic Models (Proprietary) Thermal Hydraulic Models (Non Proprietary) Thermal Hydraulic Transient Analysis Duke Proprietary Affidavit Framatome Proprietary Affidavit 15
Closing Remarks To clarify the tornado license basis, ONS intends to submit a license amendment that will seek NRC review and approval of the following:
Crediting the standby shutdown facility (SSF) as the assured mitigation path following a tornado with damage from the tornado assumed to be loss of all alternating current (AC) power to all units with significant damage to one unit.
Formal incorporation of the use of tornado missile probabilistic methodology (TORMIS) in the ONS tornado license basis and associated UFSAR changes.
Elimination of the spent fuel pool (SFP) to high pressure injection (HPI) flow path for reactor coolant makeup (RCMU) from license basis.
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