Text

Mitigating Strategies Flood Hazard Assessment (MSA) Submittal
	ML17087A343
Person / Time
Site:	Monticello
Issue date:	03/28/2017
From:	Gardner P; Northern States Power Co, Xcel Energy
To:	; Document Control Desk, Office of Nuclear Reactor Regulation
References
	CAC MF7712, L-MT-17-015
	Download: ML17087A343 (40)
	v • d • e

2807 West County Road 75 Monticello, MN 55362 800.895.4999 xcelenergy.com March 28, 2017 L-MT-17-015 10 CFR 50.54(f)

ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, DC 20555-0001 Monticello Nuclear Generating Plant Docket No. 50-263 Renewed Facility Operating License No. DPR-22 Monticello Nuclear Generating Plant, Mitigating Strategies Flood Hazard Assessment (MSA)

Submittal (CAC No. MF7712)

References:

1) NRC Letter, Request for Information Pursuant to Title 10 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. (ADAMS Accession No. ML12056A046)

2) NSPM Letter to NRC, Monticello Nuclear Generating Plant: Response to Post-Fukushima Near-Term Task Force (NTTF) Recommendation 2.1, Flooding - Flood Hazard Reevaluation Report, L-MT-16-024, dated May 12, 2016. (ADAMS Accession No. ML16145A179)

3) NRC Letter, Coordination of Requests for Information Regarding Flooding Hazard Reevaluations and Mitigating Strategies for Beyond-Design-Basis External Events, dated September 1, 2015. (ADAMS Accession No. ML15174A257)

4) NRC Staff Requirements Memorandum, Staff Requirements - COMSECY-14-0037 - Integration of Mitigating Strategies for Beyond-Design-Basis External Events and the Reevaluation of Flooding Hazards," dated March 30, 2015. (ADAMS Accession No. ML15089A236)

5) Nuclear Energy Institute (NEI) guidance, NEI 12-06, Revision 2, Diverse and Flexible Coping Strategies (FLEX) Implementation Guide, dated December 2015. (ADAMS Accession No. ML16005A625)

Document Control Desk Page 2

6) Nuclear Regulatory Commission (NRC), JLD-ISG-2012-01, Compliance with Order EA-12-049, Order Modifying Licenses with Regard to Requirements for Mitigation Strategies for Beyond-Design-Basis External Events, Revision 1, dated January 22, 2016. (ADAMS Accession No. ML15357A163)

7) NRC Letter to NSPM, Monticello Nuclear Generating Plant - Interim Staff Response to Reevaluated Flood Hazards Submitted in Response to 10 CFR 50.54(f) Information Request - Flood-Causing Mechanism Reevaluation (CAC No. MF7712), dated September 16, 2016. (ADAMS Accession No. ML16248A004)

8) 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. (ADAMS Accession No. ML13044A561)

On March 12, 2012, the NRC issued Reference 1 to request information associated with Near-Term Task Force (NTTF) Recommendation 2.1 for Flooding. One of the Required Responses in Reference 1 directed licensees to submit a Flood Hazard Reevaluation Report (FHRR).

Northern States Power Company, a Minnesota corporation (NSPM), d/b/a Xcel Energy, submitted the FHRR for the Monticello Nuclear Generating Plant (MNGP), on May 12, 2016 (Reference 2). Per Reference 8, the NRC considers the reevaluated flood hazard to be beyond the current design/licensing basis of operating plants.

Concurrent with the FHRR, NSPM developed and implemented mitigating strategies in accordance with NRC Order EA-12-049, "Requirements for Mitigation Strategies for Beyond-Design-Basis External Events," for the MNGP. In Reference 4, the NRC affirmed that licensees need to address the reevaluated flooding hazards within their mitigating strategies for beyond-design-bases (BDB) external events, including the reevaluated flood hazards. This requirement was confirmed by the NRC in Reference 3. Guidance for performing Mitigating Strategies Assessments (MSAs) is contained in Appendix G of NEI 12-06, Revision 2 (Reference 5). The Reference 5 guidance was endorsed by the NRC in Reference 6.

In Reference 7, the NRC concluded that the reevaluated flood hazards information is suitable for the assessment of mitigating strategies developed in response to Order EA-12-049 for the MNGP.

The Enclosure to this letter provides the MNGP Mitgating Strategies Flood Hazard Assessment (MSA). The new flooding analyses were bounded by the plant design basis flood for all postulated flooding scenarios, with the exception of local intense precipitation (LIP). The MSA evaluated the FLEX strategy implementation during the LIP flooding event. The assessment concluded that the existing FLEX strategies can be successfully implemented as designed. No additional actions or procedural changes are required.

Document Control Desk Page 3 Please contact John Fields, at 763-271-6707, if additional information or clarification is required.

Summary of Commitments This letter makes no new commitments and no revisions to existing commitments.

I declare under penalty of perjury that the foregoing is true and correct.

Executed on March 1:9, 2017.

Peter A. Gardner Site Vice President, Monticello Nuclear Generating Plant Northern States Power Company- Minnesota Enclosure cc: Administrator, Region Ill, USNRC Project Manager, Monticello Nuclear Generating Plant, USNRC Resident Inspector, Monticello Nuclear Generating Plant, USNRC

L-MT-17-015 NSPM ENCLOSURE MONTICELLO NUCLEAR GENERATING PLANT Monticello Mitigating Strategies Flood Hazard Assessment 36 pages to follow

Xcel Energy Contract No. 00048375 Monticello Mitigating Strategies Flood Hazard Assessment CLIENT APP.: N/A BLACK & VEATCH Overland Park, KS Issued for Use DVR180999 0 3/13/2017 SDT N/A SDT (RAR1809990002) 0019 NO. DATE DESCRIPTION DRN DES CHK APP FILE NUMBER 50.2000 REVIEW LEVEL N/A THIS DOCUMENT CONTAINS THIS DOCUMENT CONTAINS SAFETYRELATED ITEMS SEISMIC CATEGORY I ITEMS YES NO YES NO CLIENT DOCUMENT REFERENCE NUMBER TOTAL SHEETS PROJECT DOCUMENT NUMBER N/A 36 180999.50.230003

Monticello Mitigating Strategies Flood Hazard Assessment Rev. 0 Table of Contents List of Acronyms, Abbreviations, and Definitions ......................................................................................... 3 Acronyms .................................................................................................................................................. 3 Definitions ................................................................................................................................................. 4

1. Executive Summary ............................................................................................................................... 5

2. Background ........................................................................................................................................... 5 2.1 Purpose ......................................................................................................................................... 5 2.2 Site Description ............................................................................................................................. 6

3. Overview of FLEX Strategies ................................................................................................................. 7

4. Characterization of the MSFHI (NEI 1206, Revision 2, Appendix G, Section G.2).............................. 11

5. Basis for Mitigating Strategies Assessment (NEI 1206, Revision 2, Appendix G, Section G.3) .......... 12

6. Assessment of Current FLEX Strategy (NEI 1206, Revision 2, Appendix G, Section G.4.1) ................ 14 6.1 LIP Timeline ................................................................................................................................. 14 6.2 Robustness of Plant Equipment .................................................................................................. 22 6.2.1 Plant Access Doors - Evaluation of Potential Water Intrusion ........................................... 22 6.2.2 Plant Access Doors - Structural Evaluation for LIP Loads ................................................... 23 6.3 Operator Actions Outside of the Plant Structures ...................................................................... 24 6.4 FLEX Portable Equipment Storage .............................................................................................. 24 6.5 Deployment of Portable Equipment ........................................................................................... 24 6.5.1 Deployment of Portable Diesel Pump (PDP) ....................................................................... 25 6.5.2 Deployment of 120 VAC Portable Generator...................................................................... 28 6.5.3 Deployment of 480 VAC Portable Diesel Generator ........................................................... 31 6.5.4 Debris Removal ................................................................................................................... 33 6.5.5 Operation of Portable Equipment ...................................................................................... 34 6.6 Conclusions and Summary .......................................................................................................... 34

7. References .......................................................................................................................................... 35 Page 2 of 36

Monticello Mitigating Strategies Flood Hazard Assessment Rev. 0 List of Acronyms, Abbreviations, and Definitions Acronyms AC - Alternating Current BDB - Beyond Design Basis CDB - Current Design Basis cfs - cubic feet per second DC - Direct Current EDG - Emergency Diesel Generator EFT - Emergency Filtration Train ELAP - Extended Loss of all AC Power EOP - Emergency Operating Procedure ERO - Emergency Response Organization FHRR - Flood Hazard Reevaluation Report FLEX DB - FLEX Design Basis (flood hazard)

HCVS - Hardended Containment Vent System HMR - Hydro Metrological Report LIP - Local Intense Precipitation LUHS - Loss of Ultimate Heat Sink MNGP - Monticello Nuclear Generating Plant MSA - Mitigating Strategies Flood Hazard Assessment MSFHI - Mitigating Strategies Flood Hazard Information (from the FHRR and MSFHI letter)

NB - not bounded NGVD29 National Geodetic Vertical Datum of 1929 NEI - Nuclear Energy Institute NRC - Nuclear Regulatory Commission NSPM - Northern States Power Company, a Minnesota corporation NSRC - National SAFER Response Center NTTF - Near Term Task Force PAB - Plant Administration Building PDG - Portable Diesel Generator PDP - Portable Diesel Pump PMF - Probable Maximum Flood psf - pounds per square foot RCIC - Reactor Core Isolation Cooling RHR - Residual Heat Removal RHRSW - RHR Service Water RPV - Reactor Pressure Vessel SBO - Station Blackout SFP - Spent Fuel Pool SRV - Safety Relief Valve SSC - Structure, System, Component UHS - Ultimate Heat Sink USAR Updated Safety Analysis Report VAC - Volts AC VDC - Volts DC WSE - Water Surface Elevation Page 3 of 36

Monticello Mitigating Strategies Flood Hazard Assessment Rev. 0 Definitions FLEX Design Basis Flood Hazard: the controlling flood parameters used to develop the FLEX strategies for a flood.

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Monticello Mitigating Strategies Flood Hazard Assessment Rev. 0

1. Executive Summary FLEX strategies were developed to mitigate an extended loss of all AC power (ELAP) and a loss of normal access to the ultimate heat sink resulting from beyond design bases external events; including design bases flooding events. New flooding analyses were performed in support of developing the Flood Hazard Reevaluation Report (FHRR) for the Monticello Nuclear Generating Plant (MNGP). For all postulated flooding scenarios, except the Local Intense Precipitation (LIP), the new flooding analyses were bounded by the plant design basis flood. The Mitigating Strategies Assessment (MSA) evaluates FLEX strategies to ensure the strategies can successfully be implemented for the Local Intense Precipitation flooding event or to determine if changes are required to the strategies. Based on the evaluation herein, the FLEX strategies can be implemented without change for the Local Intense Precipitation event.

2. Background 2.1 Purpose On March 12, 2012, the NRC issued Reference 1 to request information associated with NearTerm Task Force (NTTF) Recommendation 2.1 for Flooding. One of the Required Responses in Reference 1 directed licensees to submit a Flood Hazard Reevaluation Report (FHRR). The NRC determined that the reevaluated flood hazard is beyond the current design/licensing basis of operating plants. Reference 2 was submitted in response to the request in Reference 1 for the MNGP. Subsequent to submittal of the FHRR (Reference 2), the MNGP performed additional more refined flooding analysis for the LIP (Reference 9). Reference 9 uses site specific precipitation inputs in lieu of the applicable HMR methods for determining precipitation inputs, and includes an unsteady flow approach to refine the evaluation of the impacts of water outside of various plant doors.

Concurrent to the flood hazard reevaluation, the MNGP developed and implemented mitigating strategies in accordance with NEI 1206, Diverse and Flexible Coping Strategies (FLEX) Implementation Guide, (earlier revision of Reference 4).

In Reference 3, the Commission affirmed that licensees need to address the reevaluated flooding hazards within their mitigating strategies for beyonddesignbasis (BDB) external events, including the reevaluated flood hazards. This position was confirmed in Reference 5.

Guidance for performing mitigating strategies flood hazard assessments (MSAs) is provided in Appendix G of NEI 1206 (Reference 4). For the purpose of the MSA, the NRC determined that the flood hazard information provided in the FHRR is the Mitigating Strategies Flood Hazard Information (MSFHI).

Appendix G of NEI 1206, describes the MSA for flooding as containing the following elements:

Section G.2 - Characterization of the MSFHI Section G.3 - Basis for Mitigating Strategies Assessment (MSFHIFLEX DB Comparison)

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)

If a Section G.3 assessment shows that the FLEX Design Basis flood hazard (FLEX DB) completely bounds the reevaluated flood (in the MSFHI), only documentation for Sections G.2 and G.3 are required; assessments and documentation for the remaining sections (G.4.1 through G.4.4) are not necessary. If a Page 5 of 36

Monticello Mitigating Strategies Flood Hazard Assessment Rev. 0 Section G.3 assessment shows that the FLEX DB does not completely bound the MSFHI, then Sections G.4.1 through G.4.4 need to be performed. Sections G.4.1 through G.4.4 are performed sequentially until an acceptable result is received. For example, if the evaluation for Section G.4.1 demonstrates that the existing FLEX strategies can be implemented as designed, then the MSA is considered complete and the results documented.

2.2 Site Description The site is located within the city limits of the Monticello, Minnesota, on the right bank of the Mississippi River. The plant site occupies an area of approximately 2,150 acres. The topography of the MNGP site is characterized by relatively level bluffs, which rise sharply above the river. Three distinct bluffs exist at the plant site at elevations 920, 930, and 940 ft. Bluffs located approximately a mile north and south of the site rise to 950 ft. Further to the north, the terrain is relatively level with numerous lakes and wooded areas. To the south, west, and east, the terrain is hilly and dotted with numerous small lakes (Reference 6).

The Mississippi River abuts the site to the north and northwest. The flow in the Mississippi River in the vicinity of the plant is unregulated and subject to large variations throughout the year. Normal river level is at elevation 905 ft and the maximum river flood stage was recorded in 1965 at elevation 916 ft.

The 1,000year projected river flood stage is at elevation 921 ft (Reference 6).

The natural grade of the power block is at elevation 930 ft with elevations of the majority of critical structure openings ranging from 931 ft to 935 ft. The floor elevation of the Intake Structure and Screen House is at 919 ft (Reference 10).

Elevations used in this evaluation are in the NGVD29 datum.

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Monticello Mitigating Strategies Flood Hazard Assessment Rev. 0

3. Overview of FLEX Strategies FLEX capability is designed to mitigate the consequences of a postulated beyonddesignbasis external event coincident with an extended loss of all AC power (ELAP) and a loss of normal access to the ultimate heat sink. NEI 1206 (Reference 4) outlines an approach for adding diverse and flexible mitigation strategiesor FLEX that will increase defenseindepth for beyonddesignbasis scenarios to address an ELAP and loss of normal access to the ultimate heat sink (LUHS) occurring simultaneously at all units on a site.

Plant coping capability during a FLEX scenario is divided into three phases:

Phase 1 (short term phase) - During Phase 1, the plant is coping using installed plant equipment.

Phase 2 (transition phase) - During Phase 2, coping is extended using portable equipment that is stored onsite.

Phase 3 (long term phase) - During Phase 3, coping is extended indefinitely using portable equipment that is stored offsite and is deployed to the site.

Time durations for the short term and transition phase are defined based on plant specific or generic analyses, capabilities of the portable onsite equipment, and capabilities for accessing the site to deploy offsite portable equipment following a beyond design bases external event.

FLEX strategies were designed and previously evaluated for the design bases flood external event (i.e.,

FLEX DB), which for the MNGP is the probable maximum flood (PMF) on the Mississippi River. The PMF is a relatively slow developing event that provide several days to prepare for the event. The FLEX strategy for the PMF is to proactively stage selected FLEX equipment within the floodprotected area before the design basis flood level is reached.

For the LIP, this same warning time does not exist. The assessment of FLEX strategy implementation for the LIP needs to account for the lack of warning time. For evaluation of the potential impact from a LIP to the FLEX strategies it is useful to understand the timeline for implementation of the strategies. For the LIP, similar to other external events, it is assumed that the ELAP occurs at time = 0. As shown in Table 6.11 this time period also corresponds with the highest rainfall period; which would be reasonable that the loss of offsite power occurs during the most severe time of the event. In addition, as the LIP event is a 6 hour6.944444e-5 days 0.00167 hours 9.920635e-6 weeks 2.283e-6 months event, assuming that the ELAP occurs at time = 0 places the maximum subsequent FLEX strategy implementation time coincident with the LIP event.

The timeline for implementation of FLEX strategies is shown in Table 31. (Reference 7)

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Monticello Mitigating Strategies Flood Hazard Assessment Rev. 0 Table 31 - Timeline for Implementation of FLEX Strategies ELAP Action Elapsed Event Time Action Remarks/Applicability Item Time Constraint (Y/N) 0 Beyond Design Basis NA Plant @100% power.

External Event Happens 1 Per C.4 Immediate Operator NA Verify HPCI and RCIC start at 47 B.09.02.A, Actions inches. Dispatch operator to Station investigate Emergency Diesel Blackout Generator.

2 1 hr Emergency Classification Y In order to ensure that followon SG1.1 Declare ELAP actions are completed consistent with the timelines identified, a timely decision must be made that the Station Blackout (SBO) condition is an Extended Loss of AC Power (ELAP).

3 2 hr DC load shed complete Y This is a necessary action to ensure safetyrelated battery power can be extended through Phase 1.

4 Per C.4 Depressurize Reactor N Reactor depressurization will be B.09.02.A, using SRVs to a range secured in a range that will enable Station that will support continued RCIC operation Blackout continued operation of RCIC 5 6 hr Offsite staffing NA NA because not a time constraint; resources begin to arrive. included for reference.

6 68 hours7.87037e-4 days 0.0189 hours 1.124339e-4 weeks 2.5874e-5 months Large Debris Removal N Will be performed by augmented personnel.

7 Per C.5 Initiate use of Hardened Y The Hardened Containment Vent 1200, Containment Vent System (HCVS) must be opened Primary System per the EOPs. The vent is Containment powered by available battery and Control supplied with Nitrogen from the Alternate Nitrogen System.

8 8 hr For emergency heat load, Y Provide makeup to the SFP using provide makeup to SFP portable FLEX pump.

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Monticello Mitigating Strategies Flood Hazard Assessment Rev. 0 Table 31 - Timeline for Implementation of FLEX Strategies ELAP Action Elapsed Event Time Action Remarks/Applicability Item Time Constraint (Y/N) 9 After 8 but Supplement Alternate Y Provide additional nitrogen supply before9.4 Nitrogen to the Alternate Nitrogen System hours to support continued SRV and Hardened Containment Vent System operation.

10 810 hr Portable diesel driven N The FLEX Portable Diesel Pump FLEX pump staged for (PDP) will be staged after hour 8 use and before end of hour 10.

Operation of PDP is not needed until start of hour 11.

11 After 10 hr Provide Battery Room Y Necessary for continued ventilation qualification and operation of batteries and equipment. Portable FLEX fans will be available and powered by the FLEX 120 VAC generator and will provide cooling.

12 After 10 hr Provide RCIC room N Necessary for continued cooling qualification and operation of RCIC equipment. Portable FLEX fans will be available and powered by the FLEX 120 VAC generator and will provide cooling.

13 After 10 hr Provide Main Control N Necessary for continued Main Room cooling Control Room habitability.

Portable FLEX fans will be available and powered by the FLEX 120 VAC generator and will provide cooling.

14 11 hr or Batteries are being Y Necessary for continued DC before repowered using power.

portable FLEX 480 VAC Diesel Generator 15 After 22 hrs Refuel portable Y Phase 2 portable equipment will equipment require refueling no earlier than 22 hrs.

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Monticello Mitigating Strategies Flood Hazard Assessment Rev. 0 Table 31 - Timeline for Implementation of FLEX Strategies ELAP Action Elapsed Event Time Action Remarks/Applicability Item Time Constraint (Y/N) 16 2572 hrs Supplement onsite Y The National SAFER Response equipment with Center (NSRC) equipment will equipment from the provide a reliable backup to the National SAFER Response onsite portable equipment for Center (NSRC) extended operation. It will restore power to a 4160 VAC bus and restore water make up from the UHS per the direction of the fully staffed ERO.

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Monticello Mitigating Strategies Flood Hazard Assessment Rev. 0

4. Characterization of the MSFHI (NEI 1206, Revision 2, Appendix G, Section G.2)

The NRC has completed the Interim Staff Response to Reevaluated Flood Hazards (Reference 8) to the flood hazards information submitted in the MNGP FHRR. The NRC staff has concluded that the licensee's reevaluated flood hazard information is suitable for the assessment of mitigating strategies developed in response to Order EA12049. The summary of the reevaluated flood hazard (i.e., MSFHI) parameters was provided in Reference 8. The following floodcausing mechanisms were considered as part of the FHRR:

Local Intense Precipitation

Streams and Rivers

Failure of Dams and Onsite Water Control/Storage Structures

Storm Surge

Seiche

Tsunami

IceInduced Flooding

Channel Migrations/Diversions Table 2 in the Enclosure to Reference 8 indicates that the following are the flood hazards for use in the MSA.

Reevaluated Flood Mechanism Stillwater Elevation Waves/Runup Hazard Local Intense 935.8 ft NGVD29 Minimal 935.8 ft NGVD29 Precipitation Note 1 to Table 2 in the Enclosure to Reference 8 states that: the licensee is expected to develop flood event duration parameters and applicable flood associated effects to conduct the MSA. The staff will evaluate the flood event duration parameters (including warning time and period of inundation) and flood associated effects during its review of the MSA.

Subsequent to submittal of the FHRR (Reference 2), the MNGP performed additional more refined flooding analysis for the LIP (Reference 9). Reference 9 uses site specific precipitation inputs in lieu of the applicable HMR methods for determining precipitation inputs, and includes an unsteady flow approach to better quantify the impacts of water outside of various plant doors. The results from Reference 9 are consistent with the flood hazards in Table 2 in the Enclosure to Reference 8.

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Monticello Mitigating Strategies Flood Hazard Assessment Rev. 0

5. Basis for Mitigating Strategies Assessment (NEI 1206, Revision 2, Appendix G, Section G.3)

FLEX strategies were developed to mitigate an extended loss of all AC power resulting from an external event; including design bases flooding events. As described in the FHRR (Reference 2), Section 3, Comparison of Current Design Basis and Reevaluated Flood Hazard, the only nonbounded flood mechanism is the LIP. The LIP is considered nonbounded because it is not included in the MNGP CDB.

As described above, subsequent to submittal of the FHRR (Reference 2), the MNGP performed additional more refined flooding analysis for the LIP (Reference 9). Reference 9 uses site specific precipitation inputs in lieu of the applicable HMR methods for determining precipitation inputs, and includes an unsteady flow approach to better quantify the impacts of water outside of various plant doors. Table 51 summarizes the results of the flood hazard reevaluation for the revised LIP calculation (Reference 9). With the exception of the change in methodology for determining precipitation inputs and the use of an unsteady flow approach, all assumptions, inputs, and methods are the same as those described in Section 2.1 of Reference 2.

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Monticello Mitigating Strategies Flood Hazard Assessment Rev. 0 Table 51 - Local Intense Precipitation Plant MSFHI Bounded FLEX DB Design (B) or Not Flood Scenario Parameter Flood MSFHI Basis Bounded (NB)

Hazard Flood by FLEX DB

1. Maximum Stillwater Elevation (ft NGVD29) 935.72 NB FLEX strategies did not include LIP as it is not within LIP was not specifically addressed in the USAR.

Flood Level and

2. Maximum Wave Runup Elevation (ft NGVD29) See Note 2 N/A

3. Maximum Hydrodynamic/Debris Loading (psf) See Note 3 N/A

4. Effects of Sediment Deposition/Erosion See Note 4 N/A Associated Effects 5. Concurrent Site Conditions See Note 5 N/A

6. Effects on Groundwater See Note 6 N/A

7. Warning Time (hours) See Note 7 N/A the MNGP design basis Flood Event 8. Period of Site Preparation (hours) See Note 8 N/A

9. Period of Inundation (hours) See Note 9 NB Duration

10. Period of Recession (hours) See Note 10 NB

11. Plant Mode of Operations See Note 11 N/A Other 12. Other Factors See Note 12 N/A Additional notes, N/A justifications (why a particular parameter is judged not to affect the site), and explanations regarding the bounded/nonbounded determination.

1. None

2. Consideration of windgenerated wave action for the LIP event is not explicitly required in NUREG/CR7046, ANS2.8 or the 50.54(f) letter. Furthermore, wave runup is considered negligible due to limited flood depths and fetch.

3. Hydrodynamic loading was not considered plausible due to surface water flow direction is not towards the buildings.

Debris impact loading was not considered plausible due to limited velocities and flood depths.

4. Due to limited velocities, and short duration of flooding, sediment deposition and erosion is not considered to have an effect on the LIP flood levels.

5. High winds and hail could coincide with the LIP event. Section 6 evaluates performing actions to implement FLEX strategies that require going outside the plant. Environmental conditions would be considered prior to personnel being directed to move between locations.

6. Due to relatively short duration of the LIP event, surcharge to groundwater is not considered.

7. Warning time is not credited in the flood protection strategy (since only permanent/passive measures are used for the LIP flood) and, therefore, was not considered as part of the analysis.

8. SSCs important to safety are protected by means of permanent/passive measures and, therefore, site preparation was not considered as part of the analysis.

9. The period of inundation varies throughout the site; the time that the water surface elevation exceeds the height of opening for plant access doors is provided in Table 6.12.

10. The time for water to recede from the site varies by site location. Once the flood waters recede below finished floor elevation it would take approximately 2 to 4 hours4.62963e-5 days 0.00111 hours 6.613757e-6 weeks 1.522e-6 months for flood waters to completely recede from areas near the plant access doors. Figures 6.11 through 6.13 show water surface elevations throughout the site at 1 hour1.157407e-5 days 2.777778e-4 hours 1.653439e-6 weeks 3.805e-7 months , 2 hours2.314815e-5 days 5.555556e-4 hours 3.306878e-6 weeks 7.61e-7 months , and 4 hours4.62963e-5 days 0.00111 hours 6.613757e-6 weeks 1.522e-6 months , respectively.

11. There are no limitations on plant modes of operation prior to, or during, the LIP event.

12. There are no other factors applicable to this flood causing mechanism.

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Monticello Mitigating Strategies Flood Hazard Assessment Rev. 0

6. Assessment of Current FLEX Strategy (NEI 1206, Revision 2, Appendix G, Section G.4.1)

The assessment of the ability to implement the FLEX strategies during a LIP focuses on the following:

Robustness of Plant Equipment (Section 6.2).

The robustness of plant equipment is evaluated to confirm that SSCs are capable of withstanding the LIP.

Actions performed by plant personnel (Section 6.3).

Potential impacts to timing of operator actions are evaluated.

FLEX Portable Equipment Storage (Section 6.4).

The location of the FLEX Storage Buildings is evaluated for potential impact from the LIP.

Deployment of Portable Equipment (Section 6.5).

The deployment of FLEX portable equipment during and following the LIP event is evaluated.

Considerations in the evaluation include deployment of the FLEX equipment from the storage building to the staging location; access to connection points, deployment of cables and hoses; and qualifications of the portable equipment.

6.1 LIP Timeline Section 6.1 identifies the assumption with bases for the timing of the ELAP concurrent with the LIP per Reference 4, Appendix G. In addition, Section 6.1 describes the impacts from the LIP that will be used for evaluation of the FLEX strategies.

As described above, FLEX strategies were initially designed for the design bases flood external event, which for the MNGP is the probable maximum flood (PMF) on the Mississippi River. The PMF is a relatively slow developing event that provides several days to prepare for the event. For the LIP, warning time is not credited. Thus, the assessment of FLEX strategy implementation for the LIP needs to account for an absence of warning time.

The LIP event is not expected to cause an ELAP. For the LIP, similar to other external events, it is assumed that the ELAP occurs at time = 0. As shown in Table 6.11 this time period also corresponds with the time period of the highest precipitation rate. It is reasonable to assume that the loss of offsite power occurs during the most severe time of the LIP event. In addition, as the LIP event is a 6 hour6.944444e-5 days 0.00167 hours 9.920635e-6 weeks 2.283e-6 months event, assuming that the ELAP occurs at time = 0 places the maximum subsequent FLEX strategy implementation time coincident with the LIP event.

The updated LIP calculation for the MNGP is provided in Reference 9; which describes the inputs, assumptions, methodology, and results. The timelines for the cumulative precipitation and precipitation rates during the LIP are shown in Table 6.11. The precipitation rate is determined by dividing the change in cumulative precipitation by the change in time duration.

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Monticello Mitigating Strategies Flood Hazard Assessment Rev. 0 Table 6.11, Precipitation Cumulative Precipitation and Rates Time Cumulative Precipitation Rate Duration Precipitation (inches) (inches/hour) 5 min 4.5 54 15 min 7.2 16.2 30 min 10.2 12.0 1 hr 13.2 6.0 6 hr 20.6 1.5 Figures 6.11, 6.12, and 6.13 show water depths at various times during the LIP event. Water levels shown in Figures 6.11 through 6.13 are extracted from the Reference 9 analysis results. Figure 6.11 shows the water depths at 1 hour1.157407e-5 days 2.777778e-4 hours 1.653439e-6 weeks 3.805e-7 months into the event, Figure 6.12 shows the water depths at 2 hours2.314815e-5 days 5.555556e-4 hours 3.306878e-6 weeks 7.61e-7 months into the event, and Figure 6.13 shows the water depths at 4 hours4.62963e-5 days 0.00111 hours 6.613757e-6 weeks 1.522e-6 months into the event.

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Monticello Mitigating Strategies Flood Hazard Assessment Rev. 0 Figure 6.11, Water Depths During LIP at One Hour Page 16 of 36

Monticello Mitigating Strategies Flood Hazard Assessment Rev. 0 Figure 6.12, Water Depths During LIP at Two Hours Flow_ Dept11_2Hr (ft)

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.75-5

* * .0 Page 17 of 36

Monticello Mitigating Strategies Flood Hazard Assessment Rev. 0 Figure 6.13, Water Depths During LIP at Four Hours Flow_Depth_4Hr (ft) c:JM.2S c:Jo.2s-o5 c:Jo.s - o.7s c:Jo.75-1 c : J I.0-125 c:J 1,25-15

. 1.5-1.75

. 1.75-2

. 2.0 - 2.25

. 2.25 - 25

. 2.5 - 2.75

. 2.75-3

. 3.0 - 3.25

- 3.25 -a

. 3.5-3.75

. 3.75- *

*.o.*..25

* . 25 -4.5

*5-4.75

* . 75 - 5

*5.o Page 18 of 36

Monticello Mitigating Strategies Flood Hazard Assessment Rev. 0 An additional consideration is the potential for water ingress to the plant structures. As shown in Table 6.12, the maximum water surface elevations around the plant structures can be up to 1.00 ft above the elevation for some of the plant access door sills or inverts. Table 6.12 includes the maximum water depth at each door, the door opening width, door gap or if the door is assumed to be open, the peak water inflow rate and total inflow volume and time duration that the water elevation exceeds the door opening. The maximum water depths occur at different times all during the first hour of the event. The locations of the plant access doors are shown on Figure 6.14.

Table 6.12 Water Depth at Plant Access Doors Maximum Total Total Estimated Water Depth at Door Gap at Peak Inflow Opening Estimated Estimated Maximum Opening Opening Bottom of Opening Location Invert/Sill Level Inflow Inflow WSE Width Door (in.)

(ft) Volume Time (ft) (ft) (in.) (ft) (Note 1) (cfs) (gpm)

(ft3) (min) 3/4 0.77 346 707 30 Intake Structure Door (Door 209) - interior 919.50 920.02 0.52 6.24 3 1/2 0.51 229 472 30 between Screen House and Intake Structure Open 3.23 1,450 1,520 30 West RollUp Door Turbine Building Turbine Bldg Addition 931.25 931.11 n/a n/a n/a n/a Door 119 Open n/a n/a (Door 119) (Notes 2 and 3)

East RollUp Door Turbine Building Turbine Bldg Addition 931.25 931.53 0.28 3.36 n/a n/a Door 120 Open n/a n/a (Door 120) (Notes 2 and 3)

Turbine Bldg Door (Door 1 1.04 467 2,242 66 931.00 931.53 0.53 6.36 3 30) 3/4 0.78 350 1,681 66 Railcar Entry - Turbine 1 6.5 2,918 17,700 86 935.00 935.72 0.72 8.64 16 Bldg (Door 24) 1/4 1.6 719 4,425 86 1/8 0.48 216 617 36 Railcar Entry - Reactor 935.00 935.23 0.23 2.76 17 Bldg (Doors 45 and 46) 1/16 0.24 108 309 36 Emergency Diesel Generator - East 931.00 931.11 0.11 1.32 3 1/4 0.12 54 33 7 (Door 8)

Emergency Diesel Generator - West 931.00 931.11 0.11 1.32 3 1/4 0.12 54 33 7 (Door 7) 1/2 0.48 216 177 9 PAB Stairway Door 932.83 933.09 0.26 3.12 4 (Adjacent to Door 341) 5/16 0.30 135 111 9 1/2 1.03 463 2,253 67 13.8 KV Room 931.00 931.52 0.52 6.24 6 (Door 1) 1/4 0.51 229 1,127 67 1/4 0.59 265 2,720 101 Off Gas Stack 932.50 933.50 1.00 12.00 5 (Door 193) 1/8 0.30 135 1,360 101 1/4 0.10 45 28 7 Fuel Oil Transfer Pump House 931.00 931.11 0.11 1.32 2.5 1/8 0.05 23 14 7 (Door 483)

Open 0.26 117 52 7 Flex Building #1 Flex #1 East (FLEX Storage Bldg) 920 919.81 0 0 n/a n/a RollUp Door n/a n/a East RollUp Door Open Flex Building #1 Flex #1 West (FLEX Storage Bldg) 920 920.04 0.04 0.48 n/a n/a RollUp/Man n/a n/a West RollUp /Man Door Open Door Page 19 of 36

Monticello Mitigating Strategies Flood Hazard Assessment Rev. 0 Table 6.12 Water Depth at Plant Access Doors Maximum Total Total Estimated Water Depth at Door Gap at Peak Inflow Opening Estimated Estimated Maximum Opening Opening Bottom of Opening Location Invert/Sill Level Inflow Inflow WSE Width Door (in.)

(ft) Volume Time (ft) (ft) (in.) (ft) (Note 1) (cfs) (gpm)

(ft3) (min)

Flex Building #2 Flex #2 North (Warehouse #6) 931.94 932.56 0.62 7.44 n/a n/a n/a n/a Door Open North Door Flex Building #2 Flex #2 Center (Warehouse #6) 931.71 932.56 0.85 10.20 n/a n/a n/a n/a Door Open Center Door Flex Building #2 Flex #2 South (Warehouse #6) 931.71 932.56 0.85 10.20 n/a n/a n/a n/a Door Open South Door Notes:

1. Where more than one gap for a door is shown, the smaller gap is based on site measurements. The larger gap is an assumed value that is conservative relative to the measured gap.

2. Doors 119 and 120 can be open or closed and are assumed to be open for this evaluation.

3. Doors 119 and 120 are exterior doors from the outside to the Turbine Building Addition. Door 30 is between the Turbine Building Addition and the Turbine Building. Door 30 is credited with precluding water ingress in lieu of Doors 119 and 120.

Page 20 of 36

Monticello Mitigating Strategies Flood Hazard Assessment Rev. 0 Figure 6.14, Plant Access Door Locations Page 21 of 36

Monticello Mitigating Strategies Flood Hazard Assessment Rev. 0 6.2 Robustness of Plant Equipment Section 6.2 evaluates the robustness of plant equipment per Reference 4, Appendix G, in order to demonstrate that the existing FLEX strategies can be implemented for the LIP.

The MNGP is licensed for a PMF from the Mississippi River with a flood water elevation up to 939.2 ft (USAR Reference 6). Procedural actions are implemented based on river water elevation projections to provide flood protection for a PMF. Flood preparation measures for a PMF are implemented per procedures A.6 and 830002 (References 10 and 11, respectively). Specific measures are taken as part of References 10 and 11 for preparation for a flood from the Mississippi River. These protective measures include construction of a levee and bin wall extensions around the power block and sealing penetrations in the Intake Structure in order to keep water out of the plant. Implementation of these preparation measures can take several days. Based on the time duration of the PMF there is sufficient time to implement the protective measures.

For a LIP event the levee and bin wall extensions would not be constructed due to an absence of warning time and because, if constructed, the levee and bin wall extensions could exacerbate the LIP event by precluding water drainage from the site. With the exception of Door 209, penetrations in the Intake Structure will not see water during the LIP. During the LIP flood, the predicted water levels exceed threshold elevations of several pathways as the doors are not protected.

The evaluation of the robustness of plant flood protection features during a LIP considers (1) the impact of water intrusion at doors that would not be protected, and (2) the structural impacts of the hydraulic loads to doors that would not be protected.

6.2.1 Plant Access Doors - Evaluation of Potential Water Intrusion As shown in Table 6.12, the LIP flood levels exceed the elevation of several door sill/inverts. The impact of inleakage by the doors in Table 6.12 is assessed by considering the location in the plant structures where the water could accumulate.

EDG Building The peak water elevation outside the doors is 931.11 or approximately 1.3 inches. The equipment in the EDG Building can tolerate a water depth up to 16 inches. In addition, there are 9 in. curbs which separate the two EDG rooms from each other and separate the EDG Building from the Turbine Building.

At a water level of 9 in. in the EDG Building, the water would overtop the curbs and flow into the Turbine Building. Therefore, even if it is assumed that the water level in the EDG Building equalized with the water level outside the doors, SSCs important to safety in the EDG Building would not be adversely affected by the LIP.

Turbine Building Leakage past Doors 1, 24, 30, and 209 could accumulate in the Turbine Building. Leakage past Door 1 can accumulate in either the Turbine Building or the PAB Basement, thus, it is included in the determination of total water accumulation in both structures. The available volume in the Turbine Building to accommodate inleakage is 140,874 ft3. Turbine Building Addition Doors 119 and 120 can either be open or closed, thus, Doors 119 and 120 are not credited with precluding water ingress. Door 30 is credited in lieu of Doors 119 and 120. Using the conservative door gap sizes for Doors 1, 24, 30, and 209 (assuming that Door 209 is open) the total water volume that could accumulate in the Turbine Page 22 of 36

Monticello Mitigating Strategies Flood Hazard Assessment Rev. 0 Building is 2,253 + 17,700 + 2,242 + 1,520 = 23,715 ft3. Thus, SSCs important to safety in the Turbine Building will not be adversely affected by the LIP.

PAB Basement Leakage past the PAB Stairway Door and Door 1, could accumulate in the PAB Basement. The available volume in the PAB Basement to accommodate inleakage is 3,047 ft3. It is noted that the volume of 3,047 ft3 is based on a conservative water height of 4 inches as compared to a limiting component height of 4.75 inches. Using the conservative door gap sizes for the PAB Stairway Door and Door 1 the total water volume that could accumulate in the PAB Basement is 177 + 2,253 = 2,430 ft3. If the realistic door gap size is used for Door 1, the total water volume that could accumulate in the PAB Basement is 177 + 1,127 = 1,304 ft3. This is much less than the acceptance criteria of 3,047 ft3. Thus, SSCs important to safety in the PAB will not be adversely affected by the LIP. 2,430 ft3 of water in the PAB Basement is equivalent to 3.2 inches of water depth.

Fuel Oil Pump House The available volume in the Fuel Oil Pump House to accommodate inleakage past Door 483 is 80 ft3.

Using a conservative door gap with the door closed the inleakage is 28 ft3. Furthermore, conservatively assuming that Door 483 is open the total water volume that could accumulate in the pump house is 52 ft3. Thus, SSCs important to safety in the Fuel Oil Pump House will not be adversely affected by the LIP.

Reactor Building Leakage past Doors 45/46 and 193 could accumulate in the Reactor Building. The available volume of the Reactor Building to accommodate inleakage is 6,713 ft3. Using the conservative door gap size for Door 45/46 and Door 193 the total water volume that could accumulate in the Reactor Building is 617 +

2,720 = 3,337 ft3. This is much less than the allowable volume of 6,713 ft3. Thus, SSCs important to safety in the Reactor Building would not be adversely affected by the LIP.

Intake Structure Leakage by Door 209 would accumulate in the Turbine Building, and is addressed in the discussion for the Turbine Building, above.

Off Gas Stack Leakage by Door 193 into the Off Gas Stack would accumulate in the Reactor Building. This is included in the above discussion of the Reactor Building. There are no SSCs important to safety in the OffGas Stack that could be affected by water accumulation during the LIP.

6.2.2 Plant Access Doors - Structural Evaluation for LIP Loads Consideration was also given to hydrodynamic and debris impacts during the LIP event. The maximum flood level predicted during the LIP event is 935.72 ft. The LIP event does not include any debris impact or any appreciable hydrodynamic effects due to the direction of all flow being away from the building.

As described above, there are several doors that will be subjected to water loading without flood protection. Reference 12 performed a structural evaluation comparing existing allowable pressure, differential pressure, or capacity qualifications for each door with the resultant LIP loading. The results of the evaluation indicate that the existing allowable pressure, differential pressure, or capacity qualifications bound the resultant LIP loading.

Page 23 of 36

Monticello Mitigating Strategies Flood Hazard Assessment Rev. 0 6.3 Operator Actions Outside of the Plant Structures Section 6.3 evaluates performing operator actions outside of plant structures during the LIP. Following unit trip, an operator goes to the Gas House to support the purge of hydrogen in the main generator.

Accessing the gas house requires a short transit outside the Turbine Building; near the Turbine Building Railway Door 24. This is the only operator action outside of plant structures during the LIP.

The MNGP FLEX Validation document (Reference 13) indicates that there is a 5 hour5.787037e-5 days 0.00139 hours 8.267196e-6 weeks 1.9025e-6 months time constraint for performing this action. The ability to purge the main generator within the time constraint was validated in Reference 13, Validation Plan No. 1009; which showed that the action could be completed within 14 minutes. The validation plan assumed that the actions did not start until after the first hour.

Precipitation rates as a function of time are shown in Table 6.11, above. During the first hour the precipitation rates are very high and may make it difficult for the operator to go between the Turbine Building and the Gas House. After the first hour, the precipitation rate has decreased to 1.5 inches per hour and the operator can make the transit to perform the actions in the Gas House. Table 6.12 shows that the peak water surface elevation near Door 24 is 8.6 inches and the water elevation is above the door elevation for 86 minutes. After that time, the water has receded from this area and is no longer above the door sill. Thus, water elevations during the LIP will not preclude the operator from being able to make the transit to the Gas House to perform the actions.

Assuming the operator does not start the actions until after the water has receded from the vicinity of Door 24 is consistent with the validation plan assumption. Using the validated time of 14 minutes to perform the actions, there is more than sufficient time to complete the actions to purge the main generator within the 5 hour5.787037e-5 days 0.00139 hours 8.267196e-6 weeks 1.9025e-6 months time constraint.

6.4 FLEX Portable Equipment Storage Section 6.4 evaluates the storage of FLEX portable equipment per Reference 4, Appendix G, in order to demonstrate that the existing FLEX strategies can be implemented for the LIP.

Two storage buildings are provided; Warehouse #6 and the FLEX Storage Building; shown on Figures 6.5 1 through 6.53. One complete set of portable equipment is stored in each FLEX storage building. The portable equipment to be deployed and the deployment strategy are determined during the initial time of the event using procedure C.54101, FLEX Site Assessment (Reference 14). The LIP calculation determines the peak water level that could be reached inside Warehouse #6 and the FLEX Storage Building assuming that the exterior doors are open. The peak water level inside Warehouse #6 is 10.2 in. and inside the FLEX Storage Building is 0.48 in. These water levels will not adversely affect the FLEX portable equipment in the storage buildings, the associated equipment such as hoses, or the deployment vehicle. Thus, for the LIP, both sets of FLEX portable equipment will be available providing redundancy and flexibility.

6.5 Deployment of Portable Equipment Section 6.5 evaluates FLEX equipment deployment, including validation performed of deployment activities, per Reference 4, Appendix G, in order to demonstrate that the existing FLEX strategies can be implemented for the LIP.

Page 24 of 36

Monticello Mitigating Strategies Flood Hazard Assessment Rev. 0 Table 31, above, identifies the time critical actions that need to be completed for successful implementation of the FLEX strategies. Actions that require deployment of portable equipment and the associated timing are:

Stage the diesel driven FLEX pump for use within 810 hours0.00938 days 0.225 hours 0.00134 weeks 3.08205e-4 months . This is for Reactor Pressure Vessel (RPV) makeup and SFP makeup (nonemergency case). Provide makeup to Spent Fuel Pool (SFP) within 8 hours9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months for the case where the reactor fuel assemblies are offloaded into the SFP; referred to as the emergency heat load case.

Provide Battery Room, RCIC Room and Main Control Room cooling within 10 hours1.157407e-4 days 0.00278 hours 1.653439e-5 weeks 3.805e-6 months using portable fans powered from portable FLEX 120 VAC generators.

Repower Battery Chargers within 11 hours1.273148e-4 days 0.00306 hours 1.818783e-5 weeks 4.1855e-6 months using portable FLEX 480 VAC generators.

Each of these is described in more detail below. Equipment deployment locations are shown on Figures 6.51, 6.52 and 6.53.

Refueling of portable equipment is not included as part of this evaluation. As shown in Table 31, refueling of portable equipment is required no earlier than 22 hours2.546296e-4 days 0.00611 hours 3.637566e-5 weeks 8.371e-6 months ; which is well after the LIP event is over.

6.5.1 Deployment of Portable Diesel Pump (PDP) 6.5.1.1 Function The function of the portable diesel pump (PDP) is to provide makeup to the Reactor Pressure Vessel (RPV) and the Spent Fuel Pool (SFP). As shown in Table 31, for providing makeup to the RPV and the SFP, the PDP is staged after hour 8 and before the end of hour 10 after event initiation. For the case during an outage where the fuel has been removed from the RPV and placed in the SFP (emergency heat load case) it may be necessary to provide makeup to the SFP within 8.3 hours3.472222e-5 days 8.333333e-4 hours 4.960317e-6 weeks 1.1415e-6 months ; i.e., minimum time for the liquid in the SFP to start to boil (Reference 7). The LIP event is over by this time and as shown on Figures 6.51, the water levels have receded and will not affect PDP deployment or operation.

6.5.1.2 Pump Staging and Hose Routing Location Procedure C.54201 (Reference 15) shows possible PDP staging locations and hose routing. Only one PDP is deployed. The suction for the PDP can be taken from the Intake or the Discharge Canal. The PDP staging location depends on the selected suction source. Figure 6.51 shows potential PDP staging locations and deployment routes six hours into the LIP event. The majority of the deployment routes are relatively dry with the exception of the south side of the Warehouse #6. Adjacent to the south side of Warehouse #6 is a swale with deeper water. As shown on Figure 6.51 south of the swale, the water depth is less than 9 inches and will not preclude deployment.

Page 25 of 36

Monticello Mitigating Strategies Flood Hazard Assessment Rev. 0 Figure 6.51 PDP Deployment Routes and Staging Locations (water elevations shown are at 4 hours4.62963e-5 days 0.00111 hours 6.613757e-6 weeks 1.522e-6 months )

Flow_Depth_4Hr (ft) c:Jo.o.25 c:Jo25-0.5 c:Jo.5-o7s c:Jo.75-*

01.0-125

- 1.25-1.5

- 1.5-1.75

- 1.75-2

- 2.0-2.25

- 2.25-2.5

- 2.5-2.75

- 2.75-3

. 3.0-3.25

. 3.25-3.5

. 3.5-3.75

. 3.75-*

* .o-*.25

- 425-*.s

- *.5 -4.75

* . 75-5

*5 o Page 26 of 36

Monticello Mitigating Strategies Flood Hazard Assessment Rev. 0 6.5.1.3 Connection Locations The PDP can be connected to one of the following locations to provide makeup to the RPV and SFP:

1. RHRSW68 via Turbine Building North Route

2. Fire System at 12 Cooling Tower

3. A RHR Discharge Pipe

4. RHRSW68 via PAB South Route The RHRSW68 connection is at the 931 ft level in the Turbine Building. This connection point is above the accumulated water elevation in the Turbine Building. Thus, the LIP will not affect access to this connection point.

The Fire System connection at 12 Cooling Tower is located outside. As shown in Section 6.1, the LIP is essentially over after 6 hours6.944444e-5 days 0.00167 hours 9.920635e-6 weeks 2.283e-6 months and the waters have receded. The PDP is deployed after six hours and this connection point should be available.

The connection to the A RHR Discharge Pipe is at the 896 ft elevation in the Reactor Building. As discussed in Section 6.2.1, above, water volume that could accumulate in the Reactor Building is a small fraction of the available volume. Thus, this connection point will not be affected by the accumulated water volume in the Reactor Building. Thus, the LIP will not affect access to this connection point.

6.5.1.4 Time Validation MNGP validated the ability to deploy and stage the PDP within the time constraints in Reference 13, Validation Plan No. 1006. The validation plan assumed a start time of 8 hours9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months and showed that the PDP can be staged within the available time constraint. The 8 hours9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months is based on an assumed arrival time for supplemental personnel at 6 hours6.944444e-5 days 0.00167 hours 9.920635e-6 weeks 2.283e-6 months and includes 2 hours2.314815e-5 days 5.555556e-4 hours 3.306878e-6 weeks 7.61e-7 months for debris removal. For the LIP event, debris removal is expected to be minimal and deployment should be able to start earlier than 8 hours9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months . The validation also used the most limiting staging location and hose routing options. The 8 hour9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months assumed start time is after the LIP event is over and water has receded from the deployment paths. Thus, the LIP will not affect the time validation for deploying the PDP.

For the SFP emergency heat load case, it may be necessary to provide makeup to the SFP within 8.3 hours3.472222e-5 days 8.333333e-4 hours 4.960317e-6 weeks 1.1415e-6 months ; i.e., minimum time for the liquid in the SFP to start to boil. This configuration could exist during an outage. During this condition there are additional supplemental personnel already at the site to support the outage. Using available personnel, the deployment and staging would occur much sooner than 8 hours9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months , but well after the most severe time periods for the LIP. In addition, makeup would only need to be provided to the SFP in lieu of both the RPV and the SFP, which simplifies deployment and operation. Based on these considerations, the LIP will not affect the ability to provide makeup to the SFP within the time constraint.

Page 27 of 36

Monticello Mitigating Strategies Flood Hazard Assessment Rev. 0 6.5.2 Deployment of 120 VAC Portable Generator 6.5.2.1 Function The function of the 120 VAC portable generator is to power portable fans to provide forced ventilation for the Battery Room, RCIC Room and Main Control Room. As shown in Table 31, the fans are operating to provide forced ventilation for these areas before the end of hour 10 after event initiation. The LIP event is over by this time and as shown on Figure 6.52, the water levels have receded and will not affect deployment or operation of the 120 VAC portable generator.

6.5.2.2 Generator Staging and Cable Routing Location Procedure C.54406 (Reference 16) shows possible staging locations for the 120 VAC portable generator.

One 120 VAC portable generator is deployed. Figure 6.52 shows potential staging locations and deployment routes for the 120 VAC portable generator six hours into the LIP event. The majority of the deployment routes are relatively dry with the exception of the south side of the Warehouse #6.

Adjacent to the south side of Warehouse #6 is a swale with deeper water. As shown on Figure 6.52 south of the swale, the water depth is less than 9 inches and will not preclude deployment.

Page 28 of 36

Monticello Mitigating Strategies Flood Hazard Assessment Rev. 0 Figure 6.52 120 VAC Generator Deployment Routes and Staging Locations (water elevations shown are at 4 hours4.62963e-5 days 0.00111 hours 6.613757e-6 weeks 1.522e-6 months )

N w E s

Flow_ Oepth_4Hr (ft) o~2*

c:Jo25-0.5 c:Jo.s-0.75 c:Jo.75- 1 CJ1.D-1 .25

- 1.25 - 1.5

. 1.5- 1.75

- 175-2

- 2.0-2.25

- 2.25-2.5

- 25-2.75

- 2.75 * )

* .* . 3.25

. 3.25-3.$

. 3.5-3.75

- 3.75-*

-o-*.25

25-*.5

- * * .7*

50 Page 29 of 36

Monticello Mitigating Strategies Flood Hazard Assessment Rev. 0 6.5.2.3 Connection Locations The 120 VAC Generator is used to provide power to portable fans to provide cooling for Battery Chargers, the RCIC Room, and the Main Control Room.

To provide cooling to the Division I Battery Chargers, a portable fan is placed outside the Division I 250V Battery Room at elevation 928 ft in the PAB (Reference 17). Water that enters the PAB during the LIP accumulates at the 928 ft elevation. As discussed in Section 6.2.1, the water depth at the 928 ft elevation in the PAB is approximately 3 in. A portable fan can be staged above this elevation such it would not be affected by the LIP. It is noted that the placement of the portable fan is based on which battery charger(s) is powered - Refer to Section 6.5.3. If the battery chargers in the EFT are powered, then this fan is not necessary.

To provide cooling to the Division 2 Battery Chargers, a portable fan is placed outside the Division II 250V Battery Room at elevation 932 ft in the EFT Building (Reference 18). This is above the LIP maximum surface elevation and water does not enter the EFT Building during a LIP. Therefore, operation of this fan will not be affected by the LIP.

To provide cooling to the RCIC Room, the portable fan is placed at elevation 935 ft in the Reactor Building and flexible ducting is lowered to the RCIC Room (Reference 19). The power cord from the 120 VAC Generator to the portable fan is routed through Doors 45/46. As shown in Table 6.12, the water level has receded below the elevation of Doors 45/46 within 36 minutes. This is well before the portable fan, ductwork, and power cord would be staged. Therefore, operation of this fan will not be affected by the LIP.

To provide cooling to the Main Control Room, a portable fan is placed outside the PAB entrance and flexible ductwork is routed to the Main Control Room (Reference 17). The elevation of the PAB entrance is above the maximum water surface elevation for the LIP. Therefore, operation of this fan will not be affected by the LIP.

6.5.2.4 Time Validation MNGP validated the ability to deploy and stage the 120 VAC Generator within the time constraints in Reference 13, Validation Plan No. 1008. The validation showed that the total time to establish cooling was 36 minutes compared to a success criteria of 1 hour1.157407e-5 days 2.777778e-4 hours 1.653439e-6 weeks 3.805e-7 months . The validation also used the most limiting staging location, fan placement, duct routing, and cable routing options. The ability to initiate the actions to deploy the 120 VAC Generator need to consider an assumed arrival time for supplemental personnel at 6 hours6.944444e-5 days 0.00167 hours 9.920635e-6 weeks 2.283e-6 months and time for debris removal; 2 hours2.314815e-5 days 5.555556e-4 hours 3.306878e-6 weeks 7.61e-7 months has been used for other FLEX scenarios for debris removal. For the LIP event, debris removal is expected to be minimal and deployment should be able to start earlier than 8 hours9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months . The 8 hour9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months assumed start time is after the LIP event is over and water has receded from the deployment paths. With the conservative 8 hour9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months start time, cooling will be established within the available time constraint. Thus, the LIP will not affect the time validation for deploying the PDP.

Page 30 of 36

Monticello Mitigating Strategies Flood Hazard Assessment Rev. 0 6.5.3 Deployment of 480 VAC Portable Diesel Generator 6.5.3.1 Function The function of the 480 VAC Portable Diesel Generator (PDG) is to repower the Battery Chargers to charge the Batteries. As shown in Table 31, the Battery Chargers are energized no later than 11 hours1.273148e-4 days 0.00306 hours 1.818783e-5 weeks 4.1855e-6 months after event initiation. The LIP event is over by this time and as shown on Figure 6.53, the water levels have receded and will not affect deployment or operation of the PDG.

6.5.3.2 Generator Staging and Cable Routing Location Procedure (Reference 14) shows possible staging locations for the 480 VAC PDG. Only one PDG is deployed. Figure 6.53 shows potential staging locations and deployment routes for the PDG six hours into the LIP event. The majority of the deployment routes are relatively dry with the exception of the south side of the Warehouse #6. Adjacent to the south side of Warehouse #6 is a swale with deeper water. As shown on Figure 6.53 south of the swale, the water depth is 9 inches or less and will not preclude deployment.

Page 31 of 36

Monticello Mitigating Strategies Flood Hazard Assessment Rev. 0 Figure 6.53 PDG Deployment Routes and Staging Locations (water elevations shown are at 4 hours4.62963e-5 days 0.00111 hours 6.613757e-6 weeks 1.522e-6 months )

Flow_Dopt~_4Hr (ft)

Oo.o.25 Oo2s-o,5 O o.5-0.75 OoJS- 1 0 1.0 - 1.25 t::J 1.25-15 t 5 1.75 4

1.75

2 2.0-225

- 2 2.5

- 2.5-2.75

. 2.75-3

-

0 -3.25

- 3.25 - 3.5

- 3.5-3.75

- 3.75 - 4

* .0-*25

. ... .. .s

* '.75

* .75-5

* *.o Page 32 of 36

Monticello Mitigating Strategies Flood Hazard Assessment Rev. 0 6.5.3.3 Connection Locations The PDG can be connected to one of the following locations to power battery chargers or other components (Reference 20).

1. Repower D52, Charger, D3A (13) and D54, Swing Charger, D3A, D3B (13) Battery

2. Repower D10, 125 VDC Charger for #11 Battery

3. Repower D70, Charger, D16B, and D90, Charger Swing D6A

4. Repower D20, 125 VDC Charger for #12 Battery The connections for Battery Chargers D70 and D90 are located in the Division II 250 VDC Battery Room; which is located at 932 ft elevation in the EFT Building. Water does not enter the EFT Building during a LIP. Thus, the LIP will not affect making this connection.

The connections for Battery Chargers D52 and D54 are located in the Division I 250 VDC Battery Room.

The connection for Battery Charger D10 is in the Division I 125 VDC Battery Room. The connection for Battery Charger D20 is in the Division II 125 VDC Battery Room. All of these connections are located at the 928 ft elevation in the PAB. Water that enters the PAB during the LIP accumulates at the 928 ft elevation. As discussed in Section 6.2.1, the water depth at the 928 ft elevation in the PAB is approximately 3 in. The connections to the Battery Chargers are above the accumulated water depth.

It is noted that, due to water accumulation at the PAB 928 ft elevation it may be desirable to make the connection in the EFT which is unaffected by the LIP.

6.5.3.4 Time Validation MNGP validated the ability to deploy and stage the PDG within the time constraints in Reference 13, Validation Plan No. 1005. The validation plan assumed a start time of 8 hours9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months and showed that the PDG can be staged within the available time constraint; i.e., a total deployment of time of 9 hour1.041667e-4 days 0.0025 hours 1.488095e-5 weeks 3.4245e-6 months 35 minutes compared to time constraint of 11 hours1.273148e-4 days 0.00306 hours 1.818783e-5 weeks 4.1855e-6 months . The 8 hours9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months is based on an assumed arrival time for supplemental personnel at 6 hours6.944444e-5 days 0.00167 hours 9.920635e-6 weeks 2.283e-6 months and includes 2 hours2.314815e-5 days 5.555556e-4 hours 3.306878e-6 weeks 7.61e-7 months for debris removal. For the LIP event, debris removal is expected to be minimal and deployment should be able to start earlier than 8 hours9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months .

Furthermore, the 8 hour9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months assumed start time is after the LIP event is over and water has receded from the deployment paths. The validation also used the most limiting staging location and cable routing options. Thus, the LIP will not affect the time validation for deploying the PDG.

6.5.4 Debris Removal In support of implementation of FLEX strategies, debris removal is assessed in Reference 21. For debris removal, the plant maintains a front endloader and a Freightliner truck with a plow; one is stored at each FLEX Building location.

Regarding timing of debris removal (for any external event), Reference 21 states:

Based on the type of debris expected it is reasonable to consider that a deployment path can be cleared within two hours. Minor debris such as building materials, tree limbs, and fencing can be removed within a 2 hour2.314815e-5 days 5.555556e-4 hours 3.306878e-6 weeks 7.61e-7 months period by use of the Freightliner truck with chains and plow along one of the many deployment path options leading to the main security entrance as well.

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Monticello Mitigating Strategies Flood Hazard Assessment Rev. 0 For the LIP event significant debris is not expected. The deployment paths from Warehouse #6 are paved and level; thus erosion is not expected. Portions of the deployment path the FLEX Storage Building to the Protected Area are not paved and areas are sloped. These unpaved sloped areas could experience erosion due to the LIP. These paths would be assessed as part of Reference 14. Any debris removal and minor erosion repair due to the LIP are well within the capability of either the front end loader or the Freightliner truck.

6.5.5 Operation of Portable Equipment The evaluation of the operation of portable equipment considers the equipment qualifications and the conditions for the personnel operating the equipment. Per Sections 6.5.1 through 6.5.3, above, the portable equipment is expected to be available at approximately 10 hours1.157407e-4 days 0.00278 hours 1.653439e-5 weeks 3.805e-6 months . Per Table 6.11, at 6 hours6.944444e-5 days 0.00167 hours 9.920635e-6 weeks 2.283e-6 months , the LIP event is essentially over. The heaviest precipitation has passed; however, there could be some lingering relatively light precipitation. In the event that the portable equipment is staged and available prior to 6 hours6.944444e-5 days 0.00167 hours 9.920635e-6 weeks 2.283e-6 months , then per Table 6.11, the precipitation rate is approximately 1.4 inches/hour. The equipment and personnel supporting the equipment are evaluated based on this higher precipitation rate.

The procurement specifications (Reference 22) for the portable equipment include the following requirement for the equipment:

The engine and generator shall also be capable of starting and continuous operation regardless of external weather conditions (e.g., rain, snow, sleet, ice, wind, high solar radiation, high humidity, etc.). Support system enclosures shall provide protection from these elements and shall be permanently affixed to the unit (e.g., NEMA 4X cabinet for controls).

When necessary to check on the portable equipment, personnel would use protective clothing as necessary.

6.6 Conclusions and Summary The above evaluation demonstrates that the current FLEX strategies can be implemented during a LIP without changes. Therefore, consistent with NEI 1206 (Reference 4), Section G.4.1, the existing FLEX strategies can be implemented for the LIP as designed and no further actions are necessary.

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Monticello Mitigating Strategies Flood Hazard Assessment Rev. 0

7. References

1. U.S. Nuclear Regulatory Commission Letter, Request for Information Pursuant to Title 10 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 Daiichi Accident; dated March 12, 2012.

2. NSPM Letter LM16024 to the U.S. Nuclear Regulatory Commission, Monticello Nuclear Generating Plant, Units 1 and 2, Response to March 12, 2012 Request for Information Enclosure 2, Recommendation 2.1, Flooding, Required Response 2, Flooding Hazard Reevaluation Report, dated May 12, 2016, (ADAMS Accession No. ML16145A233).

3. U.S. Nuclear Regulatory Commission Letter, Coordination of Requests for Information Regarding Flooding Hazard Reevaluations and Mitigating Strategies for BeyondDesignBasis External Events, dated September 1, 2015.

4. Nuclear Energy Institute (NEI), Report NEI 1206, Rev 2, Diverse and Flexible Coping Strategies (FLEX) Implementation Guide, dated December 2015.

5. U.S. Nuclear Regulatory Commission, Revision to JLDISG201201, Revision 1, Compliance with Order EA12049, Order Modifying Licenses with Regard to Requirements for Mitigating Strategies for BeyondDesignBasis External Events, dated January 22, 2016, (ADAMS Accession No. ML15357A163).

6. NSPM, Monticello Updated Safety Analysis Report, Section 2.2, Site Description, Revision 26, and Section 2.4, Hydrology, Revision 32.

7. NSPM, FLEX, Diverse and Flexible Coping Strategies Coping Strategies (FLEX) Program Document, Revision 1.

8. U.S. Nuclear Regulatory Commission, Letter to Peter A. Gardner, Northern States Power Company - Minnesota,

Subject:

Monticello Nuclear Generator Plant - Interim Staff Response to Reevaluated Flood Hazards Submitted in Response to 10 CFR 50.54(f) Information Request -

FloodCausing Mechanism Reevaluation (CAC Nos. MF7712), Dated September 16, 2016, (ADAMS Accession No. ML16248A003).

9. Black & Veatch, Local Intense PMP & Hydrology, Calculation 180999.51.1005, Revision 4.

10. NSPM, Procedure A.6, Acts of Nature, Revision 55.

11. NSPM, Procedure 830002, External Flooding Protection, Implementation to Support A.6, Acts of Nature, Revision 7.

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Monticello Mitigating Strategies Flood Hazard Assessment Rev. 0

12. Black & Veatch, Evaluation of Structural Elements - Flood, Calculation 180999.51.1010, Revision 1.

13. NSPM, MNGP FLEX Validation, dated May 13, 2015.

14. NSPM, Ops Man C.54101, FLEX Site Assessment, Revision 1.

15. NSPM, Procedure C.54201, FLEX Portable Diesel Pump Staging and Hose Connection, Revision 0.

16. NSPM, Procedure C.54406, Stage 120V Portable Diesel Generator, Revision 0.

17. NSPM, Procedure C.54502, Control Room and PAB Ventilation during FLEX Conditions, Revision 0.

18. NSPM, Procedure C.54503, EFT Ventilation during FLEX Conditions, Revision 0.

19. NSPM, Procedure C.54501, Reactor Building Ventilation during FLEX Conditions, Revision 0.

20. NSPM, Procedure C.54402, Stage and Connect FLEX 480V Portable Diesel Generator, Revision 0.

21. Black & Veatch, Monticello Debris Removal Assessment, Evaluation 178599.50.210003, Revision 0.

22. NSPM, Monticello FLEX Portable Diesel Generator Specification, Specification MPS2173, Revision 0.

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v t e Letter Sequence Other
CAC:MF7712, (Open)
Initiation Request, Request, Request Acceptance... Administration Questions Answers Results Approval... Other: L-MT-17-015, Mitigating Strategies Flood Hazard Assessment (MSA) Submittal, ML16152A125, ML16245A720, ML16248A003, ML16323A329, ML17096A443, ML17104A310
MONTHYEAR2016-09-23 [Table View]

L-MT-17-015, Mitigating Strategies Flood Hazard Assessment (MSA) Submittal

Text

References:

Subject:

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