RA-16-041, Submittal of Mitigating Strategies Flood Hazard Assessment (Msfha)

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Submittal of Mitigating Strategies Flood Hazard Assessment (Msfha)
ML16351A219
Person / Time
Site: Oyster Creek
Issue date: 12/16/2016
From: David Helker
Exelon Generation Co
To:
Document Control Desk, Office of Nuclear Reactor Regulation
References
RA-16-041, RS-16-102
Download: ML16351A219 (19)
v • d • e


Text

Exelon Generation .

RS-16-102 10 CFR 50.54(f)

RA-16-041 December 16, 2016 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555 Oyster Creek Nuclear Generating Station Renewed Facility Operating License No. DPR-16 NRG Docket No. 50-219

Subject:

Mitigating Strategies Flood Hazard Assessment (MSFHA) Submittal

References:

1. NRG Letter, Request for Information Pursuant to Title 1O of the Code of Federal Regulations 50.54(f) Regarding Recommendations 2.1, 2.3, and 9.3, of the Near-Term Task Force Review of Insights from the Fukushima Dai-ichi Accident, dated March 12, 2012
2. Exelon Generation Company, LLC Letter to USNRC, Response to March 12, 2012 Request for Information Enclosure 2, Recommendation 2.1, Flooding, Required Response 2, Flooding Hazard Reevaluation Report, dated March 12, 2015 (RS-15-063)
3. Exelon Generation Company, LLC Letter to USNRC, Supplemental Response to NRG Audit Review Request for Additional Information Regarding Fukushima Lessons Learned

- Flood Hazard Reevaluation Report, dated April 15, 2016 (RS-16-051)

4. NRG Letter, Supplemental Information Related to Request for Information Pursuant to Title 1O of the Code of Federal Regulations 50.54(f) regarding Flooding Hazard Reevaluations for Recommendation 2.1 of the Near Term Task Force Review of Insights from the Fukushima Dai-ichi Accident, dated March 1, 2013
5. NRG Staff Requirements Memoranda to COMSECY-14-0037, "Integration of Mitigating Strategies for Beyond-Design-Basis External Events and the Reevaluation of Flooding Hazards," dated March 30, 2015
6. NRG Letter, Coordination of Requests for Information Regarding Flooding Hazard Reevaluations and Mitigating Strategies for Beyond-Design-Basis External Events, dated September 1, 2015
7. Nuclear Energy Institute (NEI), Report NEI 12-06 [Rev 2], Diverse and Flexible Coping Strategies (FLEX) Implementation Guide, dated December 2015

U.S. Nuclear Regulatory Commission Mitigating Strategies Flood Hazard Assessment (MSFHA) Submittal December 16, 2016 Page 2

8. U.S. Nuclear Regulatory Commission, JLD-ISG-2012-01, Revision 1, Compliance with Order EA-12-049, Order Modifying Licenses with Regard to Requirements for Mitigating Strategies for Beyond-Design-Basis External Events, dated January 22, 2016
9. NRC Letter, Oyster Creek Nuclear Generating Station - Interim Staff Response to Reevaluated Flood Hazards Submitted in Response to 10 CFR 50.54(f) Information Request- Flood-Causing Mechanism Reevaluation {TAC No. MF6111 ), dated February 9, 2016 On March 12, 2012, the NRC issued Reference 1 to request information associated with Near-Term Task Force (NTIF) Recommendation 2.1 for Flooding. One of the Required Responses in Reference 1 directed licensees to submit a Flood Hazard Reevaluation Report (FHRR). For Oyster Creek Nuclear Generating Station, the FHRR was submitted on March 12, 2015 (Reference 2). Additional information was provided with Reference 3. Per Reference 4, the NRC considers the reevaluated flood hazard to be "beyond the current design/licensing basis of operating plants."

Concurrent to the flood hazard reevaluation, Oyster Creek Nuclear Generating Station developed and implemented mitigating strategies in accordance with NRC Order EA-12-049, "Order Modifying Licenses with Regard to Requirements for Mitigation Strategies for Beyond-Design-Basis External Events". In Reference 5, the NRC affirmed that licensees need to address the reevaluated flooding hazards within their mitigating strategies for beyond-design-basis (BOB) external events, including the reevaluated flood hazards. This requirement was confirmed by the NRC in Reference 6. Guidance for performing mitigating strategies flood hazard assessments (MSFHAs) is contained in Appendix G of Reference 7, endorsed by the NRC in Reference 8. For the purpose of the MSFHAs and in Reference 6, the NRC termed the reevaluated flood hazard, summarized in Reference 9, as the "Mitigating Strategies Flood Hazard Information" (MSFHI). Reference 7, Appendix G, describes the MSFHA for flooding as containing the following elements:

  • Section G.2 - Characterization of the MSFHI
  • Section G.3 - Comparison of the MSFHI and FLEX DB Flood
  • Section G.4.1 -Assessment of Current FLEX Strategies (if necessary)
  • Section G.4.2 -Assessment for Modifying FLEX Strategies (if necessary)
  • Section G.4.3 - Assessment of Alternative Mitigating Strategies (if necessary)
  • Section G.4.4 - Assessment of Targeted Hazard Mitigating Strategies (if necessary)

In Reference 9, the NRC concluded that the "reevaluated flood hazards information, as summarized in the Enclosure [Summary Table of the Reevaluated Flood Hazard Levels], is suitable for the assessment of mitigating strategies developed in response to Order EA-12-049" for Oyster Creek Nuclear Generating Station.

The enclosure to this letter provides the Mitigating Strategies Assessments for Flooding for the Oyster Creek Nuclear Generating Station. The assessment concluded that the current FLEX strategies, with the addition of the sandbags at Reactor Building Doors 9 and 14 and associated warning time procedures, can be deployed and implemented as designed for the MSFHI LIP flood and no further actions, including modifications to FLEX, are required. For the reevaluated Probable Maximum Storm Surge (PMSS) event, the peak flood level is below the elevation of

U.S. Nuclear Regulatory Commission Mitigating Strategies Flood Hazard Assessment (MSFHA) Submittal December 16, 2016 Page 3 the FLEX equipment and produces minor intermittent wave runup depths in areas of FLEX deployment. Therefore, the assessment concluded that the current FLEX strategies can be successfully deployed and implemented as designed for the MSFHI PMSS flood and no further actions, including modifications to FLEX, are required.

This letter contains no new regulatory commitments. If you have any questions regarding this report, please contact Ron Gaston at (630) 657-3359.

I declare under penalty of perjury that the foregoing is true and correct. Executed on the 161h day of December 2016.

Respectfully submitted, David P. Helker Manager - Licensing & Regulatory Affairs Exelon Generation Company, LLC

Enclosure:

Oyster Creek Nuclear Generating Station, Mitigating Strategies Assessments for Flooding, dated December 16, 2016 cc: Director, Office of Nuclear Reactor Regulation NRC Regional Administrator - Region I NRC Senior Resident Inspector - Oyster Creek Nuclear Generating Station NRC Project Manager, NRR - Oyster Creek Nuclear Generating Station Ms. Tekia Govan, NRR/JLD/JHMB, NRC Mr. John D. Hughey, NRR/JLD/JOMB, NRC

Enclosure Oyster Creek Nuclear Generating Station Mitigating Strategies Assessments for Flooding dated December 16, 2016 (15 Pages)

Mitigating Strategies Assessments for Flooding Oyster Creek Nuclear Generating Station Exelon© December 16, 2016

Oyster Creek MSA for Flooding Page 2 of 15 Contents 1 Executive Summary ....... ...................................................................................... 3 2 List of Acronyms ................................................................................................. 3 3 Background ........................................................................................................ 4 3.1 Purpose ....................................................................................................... 4 3.2 Site Description ............................................................................................ 5 3.3 Overview of FLEX Strategy ............................................................................. 5 4 Characterization of MSFHI (NEI 12-06, Rev 2, Section G.2) ...................................... 7 5 Basis for Mitigating Strategy Assessment (NEI 12-06, Rev 2, Section G.3) ................. 8 6 Assessment of Current Flex Strategy (NEI 12-06, Rev 2, Section G.4.1) .................... 8 6.1 Assessment Methodology and Process .............................................................. 8 6.2 Results ....................................................................................................... 12 6.3 Conclusions ................................................................................................. 13 7 References ........................................................................................................ 13

Oyster Creek MSA for Flooding Page 3 of 15 1 Executive Summary This Mitigating Strategies Assessment (MSA) evaluates the impact of the reevaluated flood hazard on FLEX strategy implementation. The Mitigating Strategies Flood Hazard Information (MSFHI), based on Oyster Creek's Flood Hazard Reevaluation as affirmed in the NRC's February 9, 2016 interim response letter, is used to define the flood hazard for the MSA. The reevaluated flood hazard (i.e. MSFHI) showed that the plant's DB flood does not completely bound the MSFHI for the Probable Maximum Storm Surge (PMSS), including wind-wave runup, and Local Intense Precipitation (LIP). The FLEX strategies were developed prior to completion of the flood hazard reevaluation so the FLEX DB was set equivalent to the plant's DB flood, but only for the plant's DB PMSS flood (including wind-wave runup). LIP was not addressed in the FLEX DB. Therefore, both flood-causing mechanisms (PMSS and LIP) are addressed in the Mitigating Strategies Assessment (MSA).

The PMSS, including wind-wave run-up, minimally impacts the FLEX strategy which can be successfully implemented with no additional operator actions or FLEX modifications. The LIP flood adversely impacted the FLEX strategy, as originally designed, and required additional operator actions to place sandbags at Reactor Building Door locations 9 and 14 for successful implementation. OCNGS modified the FLEX strategy to incorporate the use of sandbags at Reactor Building Doors 9 and 14 to prevent LIP impacts on the FLEX strategy.

Specifically, the placement of sandbags at Reactor Building Doors 9 and 14 protect the FLEX connection points (located at the Reactor Building floor elevation 23 feet MSL FLEX manifold) and allow re-energizing USS 1A2 or 1B2 during the LIP flood. Station procedure OP-OC-108-109-1001, "Severe Weather Preparation" has been revised to include warning time (per NEI 15-05) and placement of sandbags as a result of LIP with no effect from the PMSS. Hoses and cables will be routed from the Northwest Turbine Building access door (elevation 27 feet MSL). It is noted that the strategy for storage of FLEX equipment is unaffected by MSFHI.

The FLEX equipment is designed to travel above the flood levels for both events with no issues. The FLEX Equipment Storage pads (located in the protected area at the Northwest and Southeast locations) and deployment locations are elevated above the reevaluated LIP and PMSS flood levels. The movement of the FLEX equipment will not be affected by the LIP and PMSS flooding height due to the design height of the FLEX truck and equipment.

2 List of Acronyms

  • AMS - Alternate Mitigating Strategies
  • AOP - Abnormal Event Operating Procedures
  • BDB - Beyond Design Basis
  • BDBEE - Beyond Design Basis External Events
  • CDB - Current Design Basis
  • CST - Condensate Storage Tank
  • DB - Design Basis
  • ELAP - Extended Loss of A/C Power
  • EOP - Emergency Operating Procedures
  • FHRR - Flood Hazard Reevaluation Report
  • FLEX DB - FLEX Design Basis (flood hazard); the controlling flood parameters used to develop the FLEX flood strategies
  • ICS - Isolation Condenser System
  • ISPH - Intake Screen and Pump House

Oyster Creek MSA for Flooding Page 4 of 15

  • LIP - Local Intense Precipitation
  • NRC - Nuclear Regulatory Commission
  • NGVD National Geodetic Vertical Datum of 1929
  • NTTF - Near-Term Task Force
  • MSA - Mitigation Strategy Assessment
  • MSFHA - Mitigating Strategies Flood Hazard Assessment
  • MSFHI - Mitigating Strategies Flood Hazard Information
  • MSL - Mean Sea Level
  • NW - Northwest
  • OCNGS - Oyster Creek Nuclear Generating Station
  • OIP - Overall Integrated Plan
  • PMF - Probable Maximum Flood
  • PMH - Probable Maximum Hurricane
  • PMP - Probable Maximum Precipitation
  • PMSS - Probable Maximum Storm Surge
  • SFPC - Spent Fuel Pool Cooling
  • SE- Southeast
  • THMS - Targeted Hazard Mitigating Strategies 3 Background 3.l Purpose This MSA evaluates the ability to implement FLEX strategies for the reevaluated flood hazard as defined by the MSFHI. It is performed in accordance with NEI 12-06, Rev 2, Appendix G and contains the following elements:
  • Section G.2 - Characterization of the MSFHI
  • Section G.3 - Basis for Mitigating Strategy Assessment (MSFHI-FLEX DB Comparison)
  • Section G.4.1 - Assessment of current FLEX Strategy (if necessary)
  • Section G.4.2 - Assessment for modifying FLEX Strategy (if necessary)
  • Section G.4.3 - Assessment of AMS (if necessary)
  • Section G.4.4 - Assessment of THMS (if necessary)

On March 12, 2012, the NRC issued Reference 1 to request information associated with NTTF Recommendation 2.1 for Flooding. One of the Required Responses in Reference 1 directed licensees to submit a FHRR. The Oyster Creek Nuclear Generating Station (OCNGS) FHRR was submitted on March 12, 2015 (Reference 2). Additional information was provided with References 3 and 16. Per Reference 6, the NRC considers the reevaluated flood hazard to be "beyond the current design/licensing basis of operating plants."

Concurrent to the flood hazard reevaluation, OCNGS developed and implemented mitigating strategies in accordance with NRC Order EA-12-049, "Order Modifying Licenses with Regard to Requirements for Mitigation Strategies for Beyond-Design-Basis External Events." In Reference 7, the Commission affirmed that licensees need to address the reevaluated flooding hazards within their mitigating strategies for BDBEE, including the reevaluated flood hazards. This requirement was confirmed by the NRC in Reference 8. Guidance for performing mitigating strategies flood hazard assessments (MSFHAs) is contained in Appendix G of Reference 9, endorsed by the NRC in Reference 10.

If a Section G.3 assessment shows that the FLEX DB flood completely bounds the reevaluated flood (MSFHI), only documentation for Sections G.2 and G.3 are required, and

Oyster Creek MSA for Flooding Page 5 of 15 assessments and documentation for the remaining sections (G.4.1 through G.4.4) are not necessary.

3.2 Site Description The OCNGS site is located on the eastern coastline of New Jersey, about two miles inland from the shore of Barnegat Bay and about seven miles west northwest of Barnegat Light. It is approximately nine miles south of Toms River, New Jersey, 50 miles east of Philadelphia, Pennsylvania, and 60 miles south of Newark, New Jersey (OCNGS UFSAR).

Site grade elevation is nominally 23 feet MSL. The deck elevation of the intake structure is set at elevation 6.0 feet MSL. Hurricane storm surge analysis, performed after the completion of the OCNGS, established a DB PMH stillwater level of 22 feet MSL and a wind-wave runup elevation of 23 feet MSL at the site. During such an event, the safety related buildings and structures at the plant island remain above flood levels. However, the Intake Structure deck, which is at an elevation of 6 feet MSL, will become flooded. The Circulating Water, Service Water and Emergency Service Water pumps installed on this deck will have to be shutdown, leading to the shutdown of the reactor (OCNGS UFSAR).

3.3 Overview of FLEX Strategy The OCNGS FLEX response strategies to maintain Core Cooling, Containment, Spent Fuel Pool Cooling, and Safety Function Support are summarized below. This summary is derived from the OCNGS OIP (Reference 13), including all 6-month FLEX updates through August 2016, in Response to the March 12, 2012, NRC Order EA-12-049. Movement of FLEX equipment will occur on the onset of an LIP event. Oyster Creek uses two outside FLEX Equipment Storage Pads located in the protected area at the NW and SE locations. The deployment location of the FLEX equipment is directly outside the Turbine building Northwest wall. Cables and Hoses will be routed through the Northwest Turbine building access door, through the Main Lube oil bay, to the NW Reactor Building 23-foot elevation Airlock doors and 480v room (door 9). Hoses will be connected to the FLEX manifold on RB 23-foot elevation and FLEX cables will be connected in the 480V room. Hoses are stored on a trailer with the FLEX pump and cables are stored at the entrance of the Northwest Turbine building access door. FLEX equipment is readily accessible indoors and at the FLEX storage pad.

FLEX Phase 1, (1.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br />), strategy relies on installed plant equipment. The Reactor will automatically isolate maintaining RPV inventory. Reactor Core Cooling, and Decay Heat Removal is achieved through the ICS. The ICS is comprised of two heat exchangers. The ICS is placed into service by opening a single DC powered condensate return valve in each system. The condensate return valves open automatically and are then manually cycled to limit RPV cool down rate. The ICS removes decay heat and deposits it into the environment and not into Containment. The ICS is a closed loop system.

RPV inventory is not lost due to ICS operation. Oyster Creek is designed for hot shutdown and, as long as water is supplied to the ICS shells, coping can extend indefinitely. The ICS can provide decay heat removal for 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> 40 minutes without makeup water being provided to the condenser shells. Although not credited in the FLEX time line, onsite redundant fire diesels can provide water to the ICS shells if the fire system is not damaged in the initiating event. The fire protection system is considered a defense in-depth system to use if available, but does not affect the FLEX primary strategy.

Key Reactor Parameters are obtained via DC powered and locally installed instrumentation.

A DC load shedding strategy is employed to extend battery life.

Oyster Creek MSA for Flooding Page 6 of 15 Specific Containment Control is not required in Phase 1 as both temperature and pressure stay within design limits for the first 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> of the event. Key containment parameters are obtained from DC powered instrumentation or from locally installed gauges.

No specific Spent Fuel Pool control is required in Phase 1 as both temperature and level stay within design limits for the first 14.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> of the event. Spent Fuel Pool level is obtained from the new Spent Fuel Pool wide range instrumentation installed under order EA-12-051.

No specific Safety Function Support actions are required during Phase 1.

FLEX Phase 2, {1.5 to 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />s}, strategy relies on installed plant equipment and portable equipment. Core Cooling is ensured by providing water to the shell side of the ICS within 1.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br />. Makeup water is supplied using the FLEX pump taking suction from the intake or discharge canal. Reactor Inventory control is managed using a connection to Core Spray System I and uses the same FLEX pump that provides makeup water to the shell side of the ICS. The ICS system reduces reactor pressure to the point that the low-pressure FLEX pump can inject into the RPV. Reactor inventory loss and containment energy addition are from reactor recirculation pump seal leakage and unidentified leakage, with the major contributor being recirculation pump seal leakage.

During Phase 2, electrical power is restored at 2.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br />. A portable 500KW 480VAC diesel generator is installed at 480 VAC Unit Substations USS 1A2 or USS 182. This re-powered USS will provide power to Battery chargers, ICS MOVs, and CRD pump if the CST is available. The use of the CRD pump is a FLEX defense in-depth strategy. The CST is not a protected or seismically qualified water source but if available, would provide a clean high pressure injection source to the RPV.

Electrical power is used to isolate reactor recirculation pumps, limiting RPV losses and energy addition to the containment from recirculation pump seal leakage. This restored power is also used to re-power station battery chargers ensuring the continued availability of DC power to provide critical instrumentation and DC valve operation.

Key Reactor Parameters are obtained via DC powered instrumentation or via the 500KW 480 VAC generator to re-power MCCs required to provide additional instrumentation.

No specific Containment Control is required in Phase 2 as both temperature and pressure stay within design limits for the first 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> of the event. Key Containment Parameters are obtained from DC powered instrumentation, local gauges, or instrumentation re-powered from the FLEX generator.

Spent Fuel Pool control is required in Phase 2. At 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> a connection from the FLEX pump will be made to the SFPC systems existing b.5.b connection to provide makeup water to the fuel pool. An alternate SFPC strategy is to provide a water spray directly to the fuel pool on the refueling floor.

Spent Fuel Pool level is obtained from the new Spent Fuel Pool wide range instrumentation installed under order EA-12-051.

Safety Functions Support strategies in Phase 2 include the Main Control Room, DC battery rooms, and refuel floor habitability. The strategies include opening of doors and roof hatches, and the use of portable fans and blowers, to provide ventilation to affected areas.

FLEX Phase 3, {hour 24 to 72}, strategy relies on installed plant equipment and portable equipment. Phase 1 and 2 strategies will provide sufficient capability that no additional Phase 3 strategies are required. Phase 3 equipment for OCNGS includes backup portable pumps and generators. The portable pumps will be capable of providing the necessary flow and pressure as outlined in Phase 2 response for Core Cooling & Decay Heat Removal, RCS Inventory Control and Spent Fuel Pool Cooling. The portable generators will provide the

Oyster Creek MSA for Flooding Page 7 of 15 necessary 480 VAC power requirements as outlined in Phase 2 response for Safety Functions Support.

4 Characterization of MSFHI (NEI 12-06, Rev 2, Section G.2)

The NRC has completed the "Interim Staff Response to Reevaluated Flood Hazards" (Reference 11) related to the OCNGS' Flood Hazard Reevaluation Report (Reference 2). In Reference 11, the NRC states that the "staff has concluded that the licensee's reevaluated flood hazards information is suitable for the assessment of mitigation strategies developed in response to Order EA-12-049 (i.e., defines the mitigating strategies flood hazard information described in Nuclear Energy Institute (NEI) guidance document NEI 12-06 (Reference 9)) for Oyster Creek." Tables 1 and 2 of the enclosure to Reference 11 include a summary of the CDB and non-bounding reevaluated flood hazard parameters, respectively.

In Table 1 of the enclosure to Reference 11, the NRC addresses the following flood-causing mechanisms for the current design basis flood:

  • Local Intense Precipitation;
  • Streams and Rivers;
  • Failure of Dams and Onsite Water Control/Storage Structures;
  • Storm Surge;
  • Seiche;
  • Tsunami;
  • Ice Induced Flooding; and
  • Channel Migrations/Diversions.

In Table 2 of the enclosure to Reference 11, the NRC lists flood hazard information (specifically stillwater and wind-wave runup elevations) for the following flood-causing mechanisms that are not bounded by the plant's DB flood:

  • Local Intense Precipitation; and
  • Storm Surge (Probable Maximum Storm Surge (PMSS)).

It should be noted that the "storm surge" flood-causing mechanism for OCNGS represents the NUREG/CR-7046 (Reference 12), Section H.3.2, Combined-Effects Flood {Floods along Shores of Open and Semi-Enclosed Bodies of Water (Streamside Location)). These are the reevaluated flood-causing mechanisms that were addressed in the mitigating strategies assessment. The two non-bounding flood mechanisms for OCNGS are described in detail in References 2 and 3, FHRR submittals.

Below is a summary of the MSFHI flood elevations for the applicable flood-causing mechanisms (those mechanisms that produce flood levels above plant grade); LIP and Storm Surge:

Oyster Creek MSA for Flooding Page 8 of 15 Table 1 - Summary of Reevaluated Flood Elevations Stillwater Wind-Wave Maximum Flood Flood-Causing Mechanism Elevation Runup Height Elevation (feet MSL) (feet) (feet MSL)

Local Intense Precipitation 1 :

  • Door 9 24.4 Minimal 24.4
  • Door 14 24.4 Minimal 24.4 Storm Surge/PMSS 2
  • Reactor Building 22.8 0.7 23.5
  • Site Emergency Building 22.9 3.7 26.6
  • Turbine Building 23.2 2.7 25.9
  • Intake Structure 23.2 1.4 24.6 1

LIP Flood: See Reference 3, Enclosure 1, Table 5 for stillwater elevations; Reference 3, Enclosure 1, Table 4 for hydrodynamic loads; and Reference 15, Enclosure 3 for flood event duration parameters.

2 Storm Surge/PMSS: See Reference 2, Enclosure 2, Tables 2 and 8 for stillwater and wind-wave runup elevations; and Reference 2, Enclosure 2, Section 3.11 for other associated effects and flood event duration parameters.

5 Basis for Mitigating Strategy Assessment (NEI 12-06, Rev 2, Section G.3)

The plant's DB flood for PMSS, which did not bound the reevaluated (MSFHI) PMSS flood, was incorporated as the design input to the FLEX strategy (described in Reference 13). The FLEX DB did not consider the plant's DB LIP flood. Therefore, since the MSFHI is not bounded by the FLEX DB, an evaluation was performed to address the reevaluated flooding hazards for LIP and PMSS within its BDB mitigating strategies (Reference 16; See also Section 6 below [G.4.1]).

6 Assessment of Current Flex Strategy (NEI 12-06, Rev 2, Section G.4.1)

As discussed above, the reevaluated (MSFHI) LIP and PMSS flood-causing mechanisms are not bounded by the FLEX DB and are, therefore, evaluated below as part of the MSA for OCNGS. The assessment (below) concluded that the current FLEX strategies, as described in Reference 13, can be successfully implemented without modification for the MSFHI PMSS flood (with wind-wave runup). With the procedural changes to incorporate sandbag protection and associated warning time, the current FLEX strategies can be successfully implemented without further modification for the MSFHI LIP flood. Additional details are provided below.

6.1 Assessment Methodology and Process This assessment reviews the effect of a LIP event, PMSS and concurrent ELAP/LUHS on the FLEX strategy. The assessment addresses the following key aspects of the FLEX strategy from NEI 12-06, Rev 2, Section G.4.1 (Reference 9):

  • In the sequence of events for the FLEX strategies, if the reevaluated flood hazard does not cause the ELAP/LUHS, then the time when the ELAP/LUHS is assumed to

Oyster Creek MSA for Flooding Page 9 of 15 occur should be specified and a basis provided (e.g., the ELAP/LUHS occurs at the peak of the flood).

Effect from LIP: It is assumed that the initiation of an ELAP will coincide with the peak of the LIP flood. The MSFHI LIP flood elevation is higher than the plant's DB LIP flood elevation and sandbags are required at Reactor Building Doors 9 and 14 (Reference 3) to fully deploy FLEX; specifically, re-energizing of USS 1A2 or 1B2.

Effect from Storm Surge: An ELAP is expected to occur sometime during a hurricane event due to high winds or storm surge flooding. The timing of the ELAP during the hurricane or resulting surge cannot be predicted with reasonable assurance.

However, the assessment of FLEX deployment is based on the conservative assumption that the ELAP occurs at the peak PMSS storm surge levels, including wind-wave runup.

  • The impacts of the MSFHI should be used in place of the FLEX DB flood to perform the screening and evaluation per Section 6 of NEI 12-06, Rev 2:

o Protection of FLEX Equipment (Section 6.2.3.1 of NEI 12-06, Rev 2)

  • Confirm that the guidance for protection of FLEX equipment (NEI 12-06, Rev 2, Section 11.3) was followed. Confirm that FLEX equipment is not impacted by MSFHI.

Effect from LIP: FLEX equipment has been stored and designed to the requirements of NEI 12-06. The LIP elevations at the NW and SE FLEX Storage locations are at a maximum 23.30 and 24.38 feet MSL respectively (Reference 3 pp-12 for worst case structure). The FLEX equipment, at the storage locations, is at elevation 27.5 feet MSL, therefore there is 4.2 feet (NW storage pad) and 3.1 feet (SE storage pad) MSL of margin above the LIP flood elevation. The FLEX equipment is relocated from the two storage areas (NW and SE locations) to the Turbine Building Truck Bay and Low Level Radiation Waste (LLRW) in the event of a hurricane or snowfall, not LIP flooding. Installed plant equipment supporting FLEX, including manifold riser (located at elevation 23.5 feet MSL of Reactor Building) and USS 1A2 or 1B2 transformers (located in 4160V room near Door 9) are unaffected by this event since they would be protected by the placement of sandbags at Doors 9 and 14.

Effect from Storm Surge: The protection of FLEX equipment will not be affected by wind-wave runup since the flood levels at the storage locations, NW and SE locations, are well below the FLEX equipment as not to impede their functionality. Wind-wave runup elevations at the NE and SE locations are at a maximum 25.4 feet MSL (Reference 2 pp-12 for Administration Building). The FLEX equipment, at the storage locations, is at elevation 27.5 feet MSL, 2.1 feet MSL of margin above the wind-wave runup elevation. Installed plant equipment supporting FLEX, including manifold riser and USS 1A2 or 1 B2 transformers (located in 4160V room near Door 9) are located in the Reactor Building and unaffected by this event since the peak storm surge level (with wind-wave runup) does not exceed the 23.5-foot elevation at the Reactor Building floor.

  • If applicable, document that any flood protection features credited in the FLEX strategy meet the performance criteria (NEI 12-06, Rev 2, Section G.5). How were the flood protection features evaluated?

Confirm that the flood protection features are not impacted by MSFHI.

Oyster Creek MSA for Flooding Page 10 of 15 Effect from LIP: The FLEX design uses sandbag protection measures at Reactor Building Doors 9 and 14; specifically, to assist in the re-energizing of USS 1A2 or 1B2 and protect installed plant equipment in the Reactor Building supporting FLEX, including the manifold riser and USS 1A2 or 1B2 transformers (located near Door 9). No other protection features are credited in the FLEX strategy. Sandbags are designed and implemented using guidance from the U.S. Army Corps of Engineers (Reference 17 & 18) and, therefore, meet the performance criteria in NEI 12-06, Rev 2, Section G.5.

Effect from Storm Surge: Flood protection features are not required in the FLEX strategy during a PMSS event (including wind-wave runup) since the MSFHI PMSS wind generated waves are below the height of the FLEX equipment (at elevation 27.5 feet MSL, providing 2.1 feet of margin) (Reference 2). Installed plant equipment supporting FLEX, including manifold riser and USS 1A2 or 1B2 transformers (located in 4160V room near Door 9), are located in the Reactor Building and unaffected by this event since the peak storm surge level (with wind-wave runup) does not exceed the 23.5-foot elevation at the Reactor Building floor.

o Deployment of FLEX Equipment (Section 6.2.3.2 of NEI 12-06, Rev 2)

  • Document that deployment of FLEX equipment is not impacted by MSFHI - e.g., warning time, ability to move equipment and re-stock supplies, and availability of fuel.

Effect from LIP: The MSFHI LIP flood will not affect the deployment of the FLEX equipment since maximum flood depth is 0. 88 feet along the haul path (from both NW and SE FLEX equipment storage locations) and at the deployment location. The tow vehicle and FLEX trailer mounted equipment have sufficient clearance to traverse the haul path with a flood of this magnitude. The FLEX equipment LIP flood elevations, at the NW and SE storage locations, are at 23.56 feet MSL and 23.27 feet MSL, respectively. The FLEX equipment, at the storage locations, is at elevation 27.5 feet MSL; therefore, there is 4.2 feet (NE storage pad) and 3.1 feet (SE storage pad) MSL of margin above the LIP flood elevation for the FLEX equipment. This depth will not impact the ability to deploy FLEX equipment. There is a 90-minute timeline to initially deploy the FLEX equipment, at which time, most of the water from an LIP event would recede.

Effect from Storm Surge: Wind generated waves will not affect the deployment of the FLEX equipment since the waves are at a maximum intermittent runup depth of 1.9 feet (wave runup elevation of 25.4 feet MSL minus plant grade elevation 23.5 feet MSL) along the NW and SE haul path (Reference 2; SE haul path location of FLEX is from Administration Building to Turbine Building NW wall). The FLEX equipment, at the storage locations, is at elevation 27.5 feet MSL, 2.1 feet MSL of margin above the wind-wave runup elevation of 25.4 feet MSL. Alternate paths, past the ISFSI facility and Warehouse, for both NW and SE FLEX storage locations are available, both of which have more margin to transport equipment to the deployment location at the Turbine building NW wall.

  • Document that availability and access to all connection points is not impacted by the MSFHI.

Oyster Creek MSA for Flooding Page 11 of 15 Effect from LIP: The availability and access to all connection points are maintained during the MSFHI LIP flood through the use of sandbag protection measures at Reactor Building Doors 9 and 14.

Effect from Storm Surge: The availability and access to all connection points is not impacted by the PMSS wind generated waves. Wind generated waves at Doors 9 and 14 does not reach the ingress elevation of 23.5 feet MSL and, therefore, do not adversely affect the connection points.

  • Document that deployment of temporary flood barriers is not impacted by MSFHI.

Effect from LIP: The FLEX design includes the placement of sandbags in the Reactor Building (Doors 9 and 14) to successfully implement FLEX. The staging and deployment of the sandbags was designed using the MSFHI for LIP (per References 3 and 15). LIP warning time procedures were developed per NE! 15-05 to provide sufficient time to deploy and install the sandbags.

Effect from Storm Surge: Temporary flood barriers are not credited in the FLEX strategy for the PMSS, including wind-wave runup.

o Procedural Interfaces (Section 6.2.3.3 of NEI 12-06, Rev 2)

  • Confirm that no procedural changes are required due to MSFHI.

Effect from LIP: Procedural changes were required for the LIP flood to address requirements of NE! 15-05 (Reference 14) LIP warning time for proper staging of sandbags and for establishing the required height of the sandbags. These procedural changes have already been made.

Effect from Storm surge: Procedural changes are not required for the PMSS.

o Utilization of Off-Site Resources (Section 6.2.3.4 of NEI 12-06, Rev 2)

  • Confirm that site access routes are not impacted by MSFHI.

Effect from LIP: The LIP event may cause flooding along access roads to some extent but the flooding is not expected to impede site access routes and the functionality of FLEX deployment. However, FLEX strategies do not rely on off-site resources.

Effect from Storm Surge: The storm surge event, including wind-generated waves, may cause flooding along access roads to some extent but the flooding is not expected to impede site access routes and the functionality of FLEX deployment. However, FLEX strategies do not rely on off-site resources.

  • The equipment storage guidance of Section 11.3 should be reassessed based on the impacts of the MSFHI.

Equipment storage was reassessed using the MSFHI for both LIP and PMSS and it resulted in no impacts.

  • The impacts of the MSFHI should be used in place of the FLEX DB flood in the consideration of robustness of plant equipment as defined in Appendix A of NEI 12-
06. For determining robustness only, the MSFHI should be used as the applicable hazard.

Oyster Creek MSA for Flooding Page 12 of 15 The FLEX equipment was evaluated for the worst case flood height with wave runup and will still be capable of performing their functions due to the elevated heights of the transport trailers.

Effect from LIP: LIP will cause a stillwater elevation well below the storage location elevations for FLEX equipment and therefore will not affect their function or robustness.

Effect from Storm Surge: Storm surge will cause a wind wave runup above grade, but well below the storage location elevation for the FLEX equipment and will not affect their function or robustness.

  • The impacts of the MSFHI should be used to evaluate the location of connection points in accordance with Section 3.2.2.17 of NEI 12-06, Rev 2.

Effect from LIP: The MSFHI LIP impacts the location of the FLEX connection points in the Reactor Building 23.5 feet MSL elevation. FLEX currently includes the placement of sandbags in the Reactor Building (Doors 9 and 14) and the requirements for warning time in accordance with NEI 15-05.

Effect from Storm Surge: The location of connection points is not impacted by the MSFHI PMSS wind generated waves due to minimal wind generated waves at potential ingress points.

  • Any flood protection features credited in the FLEX strategies meet the performance criteria in Section G.5.

Effect from LIP: FLEX currently includes the use of sandbags at Reactor Building Doors 9 and 14. The design was developed using USACE standards (Reference 17 &18) and meets the performance Criteria in Section G.5 of NEI 12-06, Rev. 2.

Effect from Storm Surge: There are no flood protection features credited in the FLEX strategy from the PMSS event, including wind-wave runup.

6.2 Results

  • Confirm that boundary conditions and assumptions in the initial FLEX design are maintained. If not, describe the differences. Describe the basis for this determination .

The boundary conditions and assumptions in the initial FLEX design are that large external event occurs which results in an ELAP, impedes access to the site, and the reactor is shut down. No concurrent events have occurred and the minimum shift staffing is on-site and available to respond.

The boundary conditions and assumptions in the initial FLEX design are maintained and are not changed by the MSFHI. The overall FLEX strategy boundary conditions and assumptions include moving the FLEX equipment from their storage locations (NW and SE locations) to the Turbine Building entry point and routing cables and hoses to its FLEX connection riser located inside the Reactor Building at elevation 23 feet MSL. For a LIP flood, sandbag protection at Reactor Building Doors 9 and 14 will protect FLEX implementation. There is no change to entry into ELAP or the minimum shift on-site staffing levels and will therefore not impact the boundary conditions or assumptions made by FLEX.

  • Confirm that the sequence of events for the FLEX strategies is not impacted by MSFHI (including impacts due to the environmental conditions created by MSFHI) in

Oyster Creek MSA for Flooding Page 13 of 15 such a way that the FLEX strategies cannot be implemented as currently developed.

If yes, describe the impacts. Describe the basis for this determination.

The sequence of events for the current FLEX strategies (including sandbag placement at Doors 9 and 14) is not impacted by the MSFHI and the FLEX strategy. However, based on wave action for the NW and SE storage pads for the PMSS flood, the NW storage pad closest to the Turbine building NW entry point is expected to be used if deployment occurs during the peak PMSS flood.

  • Confirm that the validation performed for the deployment of the FLEX strategies is not impacted by MSFHI. If yes, describe the impacts. Describe the basis for this determination.

Effect from LIP: The deployment of the FLEX strategies is not impacted by MSFHI for LIP. Deployment occurs within 90 minutes of declaring an ELAP and the LIP flood will recede during that time frame. Therefore, the validation performed for the deployment of the FLEX strategies is not impacted by MSFHI. OCNGS has fully incorporated sandbags into the FLEX strategies per the NE! 12-06 Appendix E Validation Guidance using the MSFHI LIP event.

Effect from Storm Surge: The deployment of the FLEX strategies is not impacted by the MSFHI for PMSS. Validation for the deployment of the FLEX strategies was performed along the longest path and assumed minimal staffing levels. Plant procedures require addition staffing when a hurricane warning is issued and provides for alternative paths at both storage pad locations that are shorter in length or subject to shallower PMSS flood depths than the path used in the validation plan.

6.3 Conclusions The assessment concluded that the current FLEX strategies, with the addition of the sandbags at Reactor Building Doors 9 and 14 and associated warning time procedures, can be deployed and implemented as designed for the MSFHI LIP flood and no further actions, including modifications to FLEX, are required.

For the MSFHI PMSS event, the flood elevation is below the elevation of the FLEX equipment and therefore will not impede the FLEX equipment functionality. Additional PMSS wind-wave runup effects will be minimal in areas of FLEX deployment and, therefore, have no impact.

With 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> of preparation time following an ELAP before a hurricane surge reaches site grade, the current FLEX strategies can be successfully deployed and implemented as designed for the MSFHI PMSS flood and no further actions, including modifications to FLEX, are required.

7 References

1. NRC Letter, Request for Information Pursuant to Title 10 of the Code of Federal Regulations S0.54(f) Regarding Recommendations 2.1, 2.3, and 9.3, of the Near-Term Task Force Review of Insights from the Fukushima Dai-ichi Accident; dated March 12, 2012.
2. Exelon Generation Company, LLC Letter to USNRC, Response to March 12, 2012 Request for Information Enclosure 2, Recommendation 2.1, Flooding, Required Response 2, Flooding Hazard Reevaluation Report and Request for Relief from Flooding Integrated Assessment, dated March 12, 2015 (RS-15-063 and RA-15-015).

Oyster Creek MSA for Flooding Page 14 of 15

3. Exelon Generation Company, LLC Letter to USNRC, Supplemental Response to NRC Audit Review Request for Additional Information Regarding Fukushima Lessons Learned - Flood Hazard Reevaluation Report, dated April 15, 2016 (RS-16-051).
4. Exelon Generation Company, LLC Letter to USNRC, Fifth Six-Month Status Response to March 12, 2012 Commission Order Modifying Licenses to Requirements for Mitigation Strategies for Beyond Design-Basis External Events (order Number EA 049) dated August 28, 2015 (RS-15-213).
5. Exelon Generation Company, LLC Letter to USNRC, Sixth Six-Month Status Response to March 12, 2012 Commission Order Modifying Licenses to Requirements for Mitigation Strategies for Beyond Design-Basis External Events, dated February 26, 2016 (RS-16-025).
6. NRC Letter, Supplemental Information Related to Request for Information Pursuant to Title 10 of the Code of Federal Regulations 50.54(f) regarding Flooding Hazard Reevaluations for Recommendation 2.1 of the Near Term Task Force Review of Insights from the Fukushima Dai-ichi Accident, dated March 1, 2013.
7. NRC Staff Requirements Memoranda to COMSECY-14-0037, "Integration of Mitigating Strategies for Beyond-Design-Basis External Events and the Reevaluation of Flooding Hazards", dated March 30, 2015.
8. NRC Letter, Coordination of Requests for Information Regarding Flooding Hazard Reevaluations and Mitigating Strategies for Beyond-Design-Basis External Events, dated September 1, 2015.
9. Nuclear Energy Institute (NEI), Report NEI 12-06 [Rev 2], Diverse and Flexible Coping Strategies (FLEX) Implementation Guide, dated December 2015.
10. U.S. Nuclear Regulatory Commission, JLD-ISG-2012-01, Revision 1, Compliance with Order EA-12-049, Order Modifying Licenses with Regard to Requirements for Mitigating Strategies for Beyond-Design-Basis External Events, dated January 22, 2016 [Effective February 29, 2016 per Federal Register/ Vol. 81, No. 39].
11. NRC Letter, Oyster Creek Nuclear Generating Station - Interim Staff Response to Reevaluated Flood Hazards Submitted in Response to 10 CFR 50.54(f) Information Request - Flood-Causing Mechanism Reevaluation (CAC NO. MF6111), dated February 9, 2016.
12. U.S. Nuclear Regulatory Commission, NUREG/CR-7046, "Design-Basis Flood Estimation for Site Characterization at Nuclear Power Plants in the United States of America", dated November 2011.
13. Overall Integrated Plan in Response to March 12, 2012 Commission Order Modifying Licenses with Regard to Requirements for Mitigation Strategies for Beyond-Design-Basis External Events (Order number EA-12-049, Dated February 28, 2013 (RS 023).
14. NEI 15-05, Rev. 6, Warning Time for Local Intense Precipitation Events, April 2015.
15. Exelon Generation Company, LLC Letter to USNRC, Response to March 12, 2012, Request for Information Enclosure 2, Recommendation 2.1, Flooding, Required Response 2, Flood Hazard Reevaluation Supplemental Information Regarding Associated Effects and Flood Event Duration Parameters, dated October 4, 2016 (RS-16-186, RA-16-074, and TMI-16-087).
16. OYS-16-001, Rev. A, Consequential and Interior Flooding Analyses, October 18, 2016.

Oyster Creek MSA for Flooding Page 15 of 15

17. Flood-Fighting Structures Demonstration and Evaluation Program: Laboratory and Field Testing in Vicksburg, Mississippi, ERDC TR-07-3, July 2007.
18. US Army Corps of Engineers Northwestern Division Sandbag Pamphlet, 2004.
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