L-MT-12-097, Final Response to NRC Request for Information Pursuant to 10CFR50.54(f) the Flooding Aspects of Recommendation 2.3 of the Near-Term Task Force Review of Insights from the Fukushima Dai-ichi Accident

Final Response to NRC Request for Information Pursuant to 10CFR50.54(f) the Flooding Aspects of Recommendation 2.3 of the Near-Term Task Force Review of Insights from the Fukushima Dai-ichi Accident

ML12333A348
Person / Time
Site:	Monticello
Issue date:	11/27/2012
From:	Grubb J Northern States Power Co, Xcel Energy
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
L-MT-12-097
Download: ML12333A348 (35)

Text

Xcel Energy@

November 27,2012 Monticello Nuclear Generating Plant 2807 W. CR 75, Monticello Monticello, MN 55362 L-MT-12-097 10 CFR 50.54(f)

U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Monticello Nuclear Generating Plant Docket No. 50-263 Renewed Facility Operating License No. DPR-22 MNGP Final Response to NRC Request for lnformation Pursuant to 10 CFR 50.54(f)

Regardinq the Flooding Aspects of Recommendation 2.3 of the Near-Term Task Force Review of Insights from the Fukushima Dai-ichi Accident

References:

1. NRC Letter, "Request for lnformation 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 lnsights from the Fukushima Dai-ichi Accident," dated March 12, 2012, ADAMS Accession No. ML12053A340.

2. NRC Letter, "Endorsement of Nuclear Energy Institute (NEI) 12-07,

'Guidelines for Performing Verification Walkdowns of Plant Flood Protection Features,"' dated May 31, 2012, ADAMS Accession No. ML12144A142.

3. NSPM Letter to NRC, "MNGP 90-Day Response to NRC Request for lnformation Pursuant to 10 CFR 50.54(f) Regarding the Flooding Aspects of Recommendations 2.1 and 2.3 of the Near-Term Task Force Review of lnsights from the Fukushima Dai-ichi Accident,"

dated June 1 1,201 2, ADAMS Accession No. ML12164A436.

On March 12, 2012, the NRC Staff issued Reference 1 to all NRC power reactor licensees and holders of construction permits in active or deferred status. Enclosure 4 of the March 12, 2012 letter contains specific Requested Actions, Requested Information, and Required Responses associated with Near-Term Task Force (NTTF)

Recommendation 2.3, Flooding. As part of this letter, licensees were requested to

Document Control Desk Page 2 perform flooding walkdowns to verify that plant features that are credited in the current licensing basis (CLB) for protection and mitigation from external flood events are available, functional, and properly maintained.

In a letter to the NRC dated June I I, 2012 (Reference 3), Northern States Power Company, a Minnesota corporation (NSPM), d/b/a Xcel Energy, confirmed that it would use the flooding walkdown procedure NEI 12-07, "Guidelines for Performing Verification Walkdowns of Plant Flood Protection Features," endorsed by the NRC in Reference 2, as the basis for the flooding walkdowns at the Monticello Nuclear Generating Plant (MNGP). In accordance with 10 CFR 50.54(f), NSPM is providing the results of its external flooding walkdowns, as well as its responses to the requested information in of Reference 1, on behalf of the MNGP.

The enclosure to this letter provides the information requested by the NRC in Reference 1 for NTTF Recommendation 2.3, Flooding. It also includes the results of the external flooding walkdowns completed at the MNGP following the guidance of NEI 12-07.

If there are any questions, or if additional information is needed, please contact Ms.

Jennie Eckholt, Licensing Engineer, at 61 2-330-5788.

Summaw of Commitments This letter proposes the following new commitments and no revisions to existing commitments.

1 2

Regulatory Commitments NSPM will complete resolution of deficiencies identified in Table 3.6-1, "Deficiency List," of the enclosure.

NSPM will complete inspection of flood protection features identified in Table 3.6-3, "Restricted Access," of the enclosure.

Due Date February 15,201 3 October 31, 2013

Document Control Desk Page 3 I declare under penalty of perjury that the foregoing is true and correct.

Executed on November 27,2012.

' Plant Manager, Monticello Nuclear Generating Plant Northern States Power Company - Minnesota Enclosure cc:

Administrator, Region Ill, USNRC Director, Office of Nuclear Reactor Regulation (NRR)

NRR Project Manager, MNGP, USNRC Senior Resident Inspector, MNGP, USNRC

ENCLOSURE MONTICELLO NUCLEAR GENERATING PLANT EXTERNAL FLOODING WALKDOWN REPORT (31 Pages Follow)

Monticello Nuclear Generating Plant External Flooding Walkdown Report TABLE OF CONTENTS INTRODUCTION........................................................................................ 1 PURPOSE.................................................................................................. 2 NRC REQUESTED INFORMATION.......................................................... 4 NRC Request.

Design Basis Flood Hazard Level(s)..........................

4 3.1. 1 MNGP Response - Design Basis Flood Hazards......................

4 3.1.2 MNGP Response. Key Assumptions 6

3.1.3 MNGP Response. Methodology Used to Develop Design Basis Flood Hazard 6

3.1.4 MNGP Response - Differences or Contradictions in Flood Hazard Levels 7

NRC Request.

Protection and Mitigation Features Considered in Licensing Basis

-7 3.2.1 MNGP Response - Flooding Licensing Basis.......................

...... 8 3.2.2 MNGP Response - Flood Duration 10 3.2.3 MNGP Response - Flood Protection Features..................

.... 10 3.2.4 MNGP Response - Weather Conditions That Trigger Protective Actions 12 3.2.5 MNGP Response - Adverse Weather Conditions Assumed with Protective Features and Actions 12 NRC Request.

Warning Systems to Detect the Presence of Water.. I 3 3.3.1 MNGP Response.

Water Level Warning Systems Credited..... I 3 NRC Request.

Effectiveness of Flood Protection Features.............. 13 3.4.1 MNGP Response. Purpose of the Walkdowns.......................... 14 3.4.2 MNGP Response -Acceptance Criteria Development.............. 14 3.4.3 MNGP Response - Evaluation of the Overall Effectiveness of Flood Protection Features and Operator Response 15 3.4.4 MNGP Response - Other Existing Plant Equipment, Structures, and Procedures that Might Mitigate the Effects of an External Flood under a Variety of Plant Configurations 15 NRC Request.

Implementation of the Walkdown Process................ 15 3.5.1 MNGP Response - Guidance for Walkdown Process................ 16 Page i

Monticello Nuclear Generating Plant External Flooding Walkdown Report TABLE OF CONTENTS 3.5.2 MNGP Response - Walkdown Team Organization.................... 16 3.5.3 MNGP Response - Walkdown Team Selection and Training.... 16 3.6 NRC Request.

Results of Flooding Walkdown 16 3.6.1 MNGP Response.

Results of Flooding Walkdown.................... 17 3.7 NRC Request.

Available Physical Margin (APM) 20 3.7.1 MNGP Response. Documentation of Available Physical Margin 20 3.8 NRC Request.

Other PlannedINewly Installed Flood Protection Features or Mitigation Measures

................... 20 3.8.1 MNGP Response.

PlannedINewly Installed Flood Protection Features or Mitigation Measures........................

20

4.0 CONCLUSION

S....................................................................................... 21

5.0 REFERENCES

......................................................................................... 22 LIST OF TABLES Table 3.6.1 : Deficiency List................................................................................ 23 Table 3.6.2. Observation List............................................................................. 24 Table 3.6.3. Restricted Access..................................

.................................... 25 Page ii

Monticello Nuclear Generating Plant External Flooding Walkdown Report REQUEST FOR INFORMATION PURSUANT TO 10 CFR 50.54(f)

NEAR-TERM TASK FORCE RECOMMENDATION 2.3 -

FLOOD WALKDOWN REPORT I

.O INTRODUCTION The United States Nuclear Regulatory Commission (NRC) issued a letter to licensees entitled "Request for lnformation 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," on March 12, 2012 (Reference 5.1). In accordance with Near-Term Task Force (NTTF) Recommendation 2.3, Flooding, of the March 12, 2012 NRC Request for lnformation (Enclosure 4 to Reference 5.1), Northern States Power Company, a Minnesota corporation (NSPM), d/b/a Xcel Energy, was requested to perform walkdowns to verify that plant features credited in the current licensing basis (CLB) for protection and mitigation from external flood events are available, functional, and properly maintained for the Monticello Nuclear Generating Plant (MNGP).

External flooding walkdowns were performed by NSPM following the guidelines provided in Nuclear Energy Institute (NEI) document 12-07, Revision O-A, "Guidelines for Performing Verification Walkdowns of Plant Flood Protection Features," dated May 2012 (Reference 5.2). The NEI 12-07 guidance has been endorsed by the NRC in a letter to NEI dated May 31, 201 2 (Reference 5.3). The results of the external flooding walkdowns performed at MNGP are presented herein.

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Monticello Nuclear Generating Plant External Floodinn Walkdown Report 2.0 PURPOSE In response to the accident at the Fukushima Dai-ichi nuclear power plant caused by the March 11,201 1, Tohoku earthquake and subsequent tsunami, the Commission established the NTTF to conduct a systematic review of NRC processes and regulations, and to make recommendations to the Commission for its policy direction. The NTTF recommendations are contained in a report to the commission, SECY-11-0093, "Near-Term Report and Recommendations for Agency Actions Following the Events in Japan," dated July 12, 201 1 (Reference 5.4).

NTTF Recommendation 2.3 (Enclosure 4 to Reference 5.1), as amended by the NRC Staff Requirements Memorandum (SRM) associated with Commission Papers SECY-11-0124 and SECY-11-0137, instructed the NRC staff to issue requests for information to licensees pursuant to 10 CFR 50.54(f). Subsequently, the NRC Staff issued a letter on March 12, 2012 (Reference 5.1) which requested licensees to provide the following information under 10 CFR 50.54(f):

Perform flood protection walkdowns using an NRC-endorsed walkdown methodology, ldentify and address plant-specific degraded, nonconforming, or unanalyzed conditions, as well as, cliff-edge effects through the corrective action program, and consider these findings in the Recommendation 2.1 hazard evaluations, as appropriate, Identify any other actions taken or planned to further enhance the site flood protection,

. Verify the adequacy of programs, monitoring and maintenance for protection features, and,

. Report to the NRC the results of the walkdowns and corrective actions taken or planned.

In response to the NRC information request, external flooding walkdowns were performed by NSPM following the methodology provided in NEI 12-07, Revision 0-A (Reference 5.2). NSPM reviewed current licensing and design basis documents including flood mitigation procedures to identify site-specific flood protection features and mitigation procedures that are credited for protection from and mitigation of an external flooding event. Installed and temporary flood protection features were included.

The scope of the external flooding walkdowns was established based on the site-specific flood protection features and mitigation procedures credited in the CLB.

The walkdowns were performed to verify if permanent Structures, Systems, and Components (SSC), temporary plant equipment and features, and the procedures needed to install and/or operate them during a flood were acceptable and capable of performing their design function as credited in the CLB. The Page 2

Monticello Nuclear Generating Plant External Flooding Walkdown Report results of the external flooding walkdowns, including identified deficiencies, observations, and areas that are classified as inaccessible or restricted-access are presented in Section 3.6 of this report. Identified deficiencies are being evaluated in accordance with the MNGP Corrective Action Program (CAP).

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Monticello Nuclear Generating Plant External Flooding Walkdown Report 3.0 NRC REQUESTED INFORMATION Appendix D of NEI 12-07 (Reference 5.2) provides additional information on the specific NRC information requested in Enclosure 4 of Reference 5.1. NSPM1s responses to the NRC1s 10 CFR 50.54(f) information requests can be found below in Sections 3.1 through 3.8. Sections 3.1 through 3.8 provided below are consistent with the NRC requested information 2.a thru 2.h listed in Enclosure 4, 3.1 NRC Request - Design Basis Flood Hazard Level(s)

Describe the design basis flood hazard level(s) for all flood-causing mechanisms, including groundwater ingress.

1, ldentify all flood hazards that were evaluated in the site's design basis and the flood level resulting from each. ldentify hazards that were screened out.

i. Note that some flood hazards may be limiting for flood level and some for other considerations such as warning time and dynamic loading.

2. Describe any key assumptions (e.g., all culverts were assumed blocked).

3. Include information on the methodology used in developing the design basis flooding hazard.

4. If differences or contradictions in flood hazard levels were found in design or licensing basis documentation, include a description of the basis for flood level used.

3.1.1 MNGP Response - Design Basis Flood Hazards Site Description/Topography The plant is located within the city limits of Monticello, Minnesota on the right (west) bank of the Mississippi River. 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 above msl.

The finished plant grade is approximately 930 ft msl. The plant grade surrounding Class I and Class II structures housing Class I equipment varies between 935 ft msl and 930 ft msl. The site description and topography is described in detail in the MNGP USAR Section 2.2 (Reference 5.9).

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Monticello Nuclear Generating Plant External Flooding Walkdown Report Hvdrolonv The normal river level at the MNGP site is about 905 ft. msl. At a distance I

.5 miles upstream, the normal river elevation is about 91 0 ft. msl, and at an equal distance downstream, the river is at 900 ft. msl.

The following flow statistics are estimated for the Mississippi River at the MNGP site:

Average Flow - 4,600 cubic feet per second (cfs)

Minimum Flow - 240 cfs Maximum Flow - 51,000 cfs The maximum reported high water level at the MNGP site was about 916 ft msl which was recorded during the spring flood of 1965 with an estimated river flow of 51,000 cfs. The results of flood frequency study for the I000 year flood estimated a peak stage of 921 ft msl (Section 2.4. of Reference 5.9)

Probable Maximum Flood (PMF)

The predicted flood discharge flow and probable maximum flood (PMF) level at the MNGP site was defined using Department of the Army, Office of the Chief of Engineers, the U.S. Army Corps of Engineers, Engineer Circular No. 11 10-2-27,, "Policies and Procedures Pertaining to Determination of Spillway Capacities and Freeboard Allowances for Dams," dated August 1, 1966 (Reference 5.7). The study results are presented in USAR Appendix G (Reference 5.9).

The probable maximum discharge was determined to be 364,900 cfs and a corresponding peak stage of elevation 939.2 ft msl. The flood would result from meteorological conditions which could occur in the spring and would reach maximum river level in about 12 days. It was estimated the flood stage would remain above elevation 930.0 ft msl for approximately I I days.

The PMF at the MNGP site was determined by transposing an actual, critical spring storm to the Mississippi River drainage area, and maximizing the precipitation for potential moisture. Potential snow cover and a critical temperature sequence were developed for determining snowmelt contribution to flood runoff. Flood runoff at the plant site was determined by developing unit hydrographs for four sub-basins, applying rainfall and snowmelt excesses to the unit hydrographs and routing the resultant hydrographs for the sub-basins to the project site.

The most critical sequence of events leading to a major flood would be to have an unusually heavy spring snowfall and low temperatures after a period of Page 5

Monticello Nuclear Generating Plant External Flooding Walkdown Report intermittent warm spells and sub-freezing temperatures has formed an impervious ground surface and then a period of extremely high temperatures followed by a major storm. The snowmelt and rainfall excesses were then routed to the plant site by computer modeling. A stage discharge rating curve was then constructed. The probable maximum discharge was determined to be 364,900 cfs with a corresponding peak stage elevation of 939.2 ft. msl from the discharge rating curve.

A probable maximum summer storm over the project area was also studied in detail and the resulting flood at the project site determined. Although the summer storm was much larger than the spring storm, the much lower retention rates under ordinary spring conditions, and the snowmelt contribution to runoff, resulted in the spring storm producing the more critical flood.

Flooding due to backwater, usually caused by ice jams, was considered. The most serious flooding throughout the Mississippi River basin has been associated with excessive snowmelt and precipitation (Appendix G, Reference 5.9).

As discussed in Reference 5.8, buildings were analyzed for hydrostatic loading up to elevation 939.2 ft msl.

3.1.2 MNGP Response - Key Assumptions As discussed in Section 3.1.I above, the PMF evaluation for the spring storm conservatively maximizes the potential snow cover and precipitation. A limiting temperature sequence that results in an impervious ground surface due to sub-freezing temperatures is assumed. This is followed by extreme high temperatures, and a subsequent major storm. The snowmelt and rainfall maximizes the runoff to the river basin. This sequence of events is not unusual in the area and the maximization of rainfall, snow-cover, and temperature would produce a probable maximum flood.

Additional details regarding key assumptions used in the analyses are described in USAR Appendix G (Reference 5.9).

3.1.3 MNGP Response - Methodology Used to Develop Design Basis Flood Hazard The predicted flood discharge flow and probable maximum flood level at the MNGP site was defined using Department of the Army, Office of the Chief of Engineers, the U.S. Army Corps of Engineers, Engineer Circular No. 1 11 0-2-27,, "Policies and Procedures Pertaining to Determination of Spillway Capacities and Freeboard Allowances for Dams," dated August 1, 1966 (Reference 5.7).

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Monticello Nuclear Generating Plant External Flooding Walkdown Report The PMF at the MNGP site was determined by transposing an actual critical spring storm to the drainage basin and maximizing the precipitation for potential moisture. Potential snow cover and a critical temperature sequence were developed for determining snowmelt contribution to flood runoff.

The study area was divided into four major sub-basins and synthetic unit hydrographs were developed for each, using Snyder's method, which is derived from the various physical basin characteristics. Unit hydrograph peaks were also increased by 25 percent and basin lag decreased by one-sixth, in accordance with standard Corps of Engineer practice.

Snowmelt and rainfall excesses were applied to unit hydrographs and the resulting hydrographs determined for each sub-basin. Sub-basin hydrographs were then routed to the project site by computer program using the modified Wilson method. Travel times for flood routing were taken from Corps of Engineers recorded travel times for large floods. Base flow was determined from long-term records of stream flow for nearby stations. Base flow was then added to the total of the routed flood hydrographs.

The stage-discharge curve at the MNGP Site was extended above the range of historical experience by means of hydraulic computations based on the river channel downstream. This was done by a series of backwater computations based on a range of discharges. Backwater computations were made using water surface elevations and their corresponding discharges as determined from the rating curve downstream from Monticello. Using the discharges and the water surface elevations determined, a stage discharge curve was constructed.

The analysis results are presented in USAR Appendix G (Reference 5.9).

3.1.4 MNGP Response - Differences or Contradictions in Flood Hazard Levels A review of documentation found no differences or contradictions in the PMF flood level of 939.2 ft identified in the design and licensing basis documentation.

3.2 NRC Request - Protection and Mitigation Features Considered in Licensing Basis Describe protection and mitigation features that are considered in the licensing basis evaluation to protect against external ingress of water into SSCs important to safety.

1. Describe the flooding licensing basis including what plant configurations (modes of operation; for example, full power operations, startup, Page 7

Monticello Nuclear Generating Plant External Flooding Walkdown Report shutdown, and refueling) were considered. This description should be consistent with the scope of the external flooding walkdowns.

2. Document the flood duration assumed in the CLB. If the CLB does not provide information on the flood duration, this lack of information should be documented in the walkdown report.

3. Describe the flood protection features that are credited in the CLB, such as incorporated, exterior and temporary barriers, time required for credited actions under flood conditions, active flood protection features, procedures, warnings credited for external floods, site drainage plan, etc.

4. Describe weather conditions or flood levels that trigger procedures and associated actions for providing flood protection and mitigation.

5. Describe the adverse weather conditions that were assumed concurrent with flood protection features and associated actions.

3.2.1 MNGP Response - Flooding Licensing Basis The following is a summary of the MNGP CLB that governs the design, operation and maintenance of plant SSCs for the protection and mitigation from external flooding events.

The CLB, as defined by 10 CFR 54.3, is the set of NRC requirements applicable to a specific plant, plus a licensee's docketed and currently effective written commitments for ensuring compliance with, and operation within, applicable NRC requirements and the plant-specific design basis, including all modifications and additions to such commitments over the life of the facility operating license. It also includes the plant-specific design basis information, defined by 10 CFR 50.2, as documented in the most recent Updated Safety Analysis Report (USAR) as required by 10 CFR 50.71.

The basis for the PMF level of 939.2' msl is discussed in Section 3.1 of this report and is detailed in USAR Section 2.4.1 and Appendix G (Reference 5.9).

Flood Protection requirements necessary to prevent external flooding or flood damage to Class I Structures or Class II structures housing Class I equipment are identified in USAR Section 12.2.1.7.1. For the design flood of 930 ft msl no increase in allowable stress was permitted in the design of buildings to withstand hydrostatic loadings. For the flood stage elevation of 939.2 ft msl, a one-third increase in allowable stress was permitted. Flood protection features include incorporated, exterior and temporary SSCs and applicable procedures that are credited to protect against or mitigate the effects of CLB external floods. The flood protection features have either an active or passive flood protection function. Flood Protection features are discussed in Section 3.2.3 below. The plant flood mitigation procedures are described in Section 3.2.3.2. The PMF Page 8

Monticello Nuclear Generating Plant External Flooding Walkdown Report event is applicable to all modes of operation (i.e., power operation, startup, hot shutdown, cold shutdown, and refueling).

Discussion of applicable NRC regulations and docketed correspondence and commitments to the NRC that are included within the MNGP CLB for flood protection are as follows:

3.2.1.I Principal Design Criteria (PDC)

MNGP was designed before the publishing of the 70 General Design Criteria (GDC) for Nuclear Power Plant Construction Permits proposed by the Atomic Energy Commission (AEC) for public comment in July 1967, and constructed prior to the 1971 publication of the 10 CFR 50, Appendix A, GDC. As such, MNGP was not licensed to 10 CFR Appendix A, GDC.

The MNGP USAR, Section 1.2, lists the PDC for the design, construction and operation of the plant. MNGP USAR Appendix E provides a plant comparative evaluation to the 70 proposed AEC design criteria. It was concluded in the USAR that the plant conforms to the intent of the GDC. A listing of the PDC and AEC GDC (by number and title) pertaining to external flooding is provided below:

PDC 1.2.1.c "General Criteria" "The design of those components which are important to the safety of the plant includes allowances for the appropriate environmental phenomena at the site. Those components important to safety and required to operate during accident conditions are designed to operate in the post accident environment."

AEC Criterion 2 - Performance Standards (Cateaorv A)

"Those systems and components of reactor facilities which are essential to prevention of accidents which could affect the public health and safety or to mitigation to their consequences shall be designed, fabricated, and erected to performance standards that will enable the facility to withstand, without loss of the capability to protect the public, the additional forces that might be imposed by natural phenomena such as earthquakes, tornadoes, flooding conditions, winds, ice, and other local site effects. The design bases so established shall reflect: (a) appropriate consideration of the most severe of these natural phenomena that have been recorded for the site and surrounding area and (b) an appropriate margin for withstanding forces greater than those recorded to reflect uncertainties about the historical data and their suitability as a basis for design."

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Monticello Nuclear Generating Plant External Flooding Walkdown Report 3.2.1.2 Regulatory Requirements and Licensing Commitments Licensing Commitments made in docketed licensing correspondence (such as licensee responses to NRC bulletins, License Event Reports, Generic Letters, and Enforcement Actions) were reviewed. One commitment was identified and is listed below:

Letter to NRC dated April 24, 1991 (MNGP LER 90-019-01)

It was identified that Procedure A.6, "Acts of Nature" for external flooding did not contain complete instructions for protecting the Diesel Fuel Oil Pump House, Diesel Fuel Oil Storage Tank, Emergency Diesel Generator Building, Turbine Building, Reactor Building, Radwaste Building, Intake Structure (including access tunnel), Off-gas Stack, Emergency Filtration Train Building, and the Control Building during a PMF. Architect-Engineer Study MNTS-83-048, 82-002-SPEC, "Flood Protection Requirements for Maximum Probable Flood" (Reference 5.8),

was not complete for these structures. Licensee Event Report (LER) 90-01 9-01 was submitted to the NRC in Letter dated April 24, 1991 (Reference 5.10).

NSPM committed to revise Procedure A.6 to address the concerns identified in the LER.

3.2.2 MNGP Response - Flood Duration The flood would result from meteorological conditions which could occur in the spring and would reach maximum river level in about 12 days. It was estimated the flood stage would remain above elevation 930.0 ft msl for approximately 11 days (Refer to USAR Appendix G).

3.2.3 MNGP Response - Flood Protection Features Flood protection features utilized at MNGP in the event of a PMF include both incorporated (installed) and temporary active and passive barriers. MNGP does not rely upon any flood protection features external to the immediate plant area as part of the current licensing basis that protect safety related systems, structures and components from inundation and staticldynamic effects of external floods.

Incorporated engineered passive or active flood protection features are features that are permanently installed in the plant that protect safety related systems, structures and components from inundation and staticldynamic effects of external flooding. Examples include external walls, penetration seals, and flood detection instrumentation, etc. that are permanently incorporated into a plant structure.

Temporary passive or active flood protection features at MNGP include portable pumps, sandbags, plastic sheeting, steel plates, levees, etc, that similarly protect safety related systems, structures and components from the effects of external Page 10

Monticello Nuclear Generating Plant External Flooding Walkdown Report flooding. These features are temporary in nature, i.e., they must be installed prior to design basis external flood levels attaining specific levels.

3.2.3.1 Incorporated Flood Protection Features All Class I and Class II structures have been designed for a high water level of 930 ft msl. The flood protection requirements necessary to prevent flooding or flood damage to Class I structures and Class ll structures housing Class I equipment in the event of the PMF were identified in Architect-Engineer Study MNTS 048, 82-002-SPEC, "Flood Protection Requirements for Maximum Probable Flood" (Reference 5.8).

The Architect-Engineer study recorded openings in buildings that are located below 939.2 ft. msl, and recommended modifications and/or methods for securing openings, as required. The resulting hydrostatic loading on the structures and buoyancy affects were also considered. Additional buildings that require protection from external flooding were identified following completion of the Architect-Engineer study and are listed below.

The following Class I and II structures are protected from flooding up to 939.2 ft.

msl:

I Reactor Building (including High Pressure Coolant Injection (HPCI) structure)

2. Turbine Building 3, Intake Structure (including access tunnel)

4. Off-gas Stack and Compressed Gas Storage Building

5. Radwaste Building

6. Diesel Generator Building

7. Plant Control and Cable Spreading Structure

8. Emergency Filtration Train (EFT) Building

9. Diesel Fuel Oil Pump House

10. Diesel Oil Storage Tank MNGP USAR Section 12.2.1.7.1 summarizes the results of the external flooding study. For the design flood of 930 ft msl no increase in allowable stress was permitted in the design of buildings to withstand hydrostatic loadings. For the flood stage 939.2 ft msl, 113 increase in allowable stress was permitted. All structures with the exception of the Diesel Generator Building are sufficiently heavy to resist buoyancy, and the stresses do not exceed the allowable defined above. Flood protection for the Diesel Generator Building is provided by either Page 11

Monticello Nuclear Generating Plant External Flooding Walkdown Report erecting a flood barrier around the structure or by preventing buckling of the building floor slab.

Diesel Fuel Oil Storage Tank T-44 has been evaluated for hydrostatic forces with the flood level up to 930 ft. msl. Should flood levels be predicted to exceed 930 ft msl, the tank will be protected by a temporary ring levee in accordance with the plants flooding Procedure A.6, "Acts of Nature."

The process for plant modifications requires a review of structural openings below the 939.2 ft elevation to ensure external flooding protection is not affected.

3.2.3.2 MNGP Response - Flood Mitigation Procedures MNGP Procedure A.6, "Acts of Nature," (Section 5.0 - External Flooding) outlines actions to be taken in the event flood waters are predicted to exceed elevation 91 8 ft. Action levels progress to 919 ft, 921 ft, 930 ft, 934 ft, and 938 ft depending on flood level predictions.

Should river level exceed 918 ft msl, an Unusual Event is declared. Should river level reach 921 ft msl, an Alert is declared and an orderly plant shutdown is commenced to place the reactor in a cold shutdown condition.

3.2.4 MNGP Response - Weather Conditions That Trigger Protective Actions In accordance with MNGP Procedure A.6, when flood predictions indicate the river level has a potential to reach 918 ft, the steps in Procedure A.6 are implemented.

The most critical sequence of events leading to a major flood would be an unusually heavy spring snowfall and low temperatures after a period of intermittent warm spells and sub-freezing temperatures has formed an impervious ground surface and then a period of extremely high temperatures followed by a major storm.

3.2.5 MNGP Response -Adverse Weather Conditions Assumed with Protective Features and Actions The current licensing basis does not describe adverse weather conditions that are assumed concurrent with flood protection features and associated actions.

Section 5.1, Precautions, of Procedure A.6, identifies that rapidly flowing floodwater and very cold floodwater temperature may be possible.

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Monticello Nuclear Generating Plant External Flooding Walkdown Report 3.3 NRC Request - Warning Systems to Detect the Presence of Water Describe any warning systems to detect the presence of water in rooms important to safety.

1. Describe the room water level warning systems credited for their flood protection function in the plant's external flooding licensing basis.

Note that systems that detect internal flooding sources are not part of the scope of the walkdown.

3.3.1 MNGP Response - Water Level Warning Systems Credited Although not credited as part of the CLB for external flooding, level sensors and pumps associated with the following annunciators were included within the scope of the external flooding walkdown report. The annunciators may indicate a flooding condition exists in rooms important to safety:

101-A-I I (HOTWELL AREA FLOODING) 101-A-9 (CW PUMP PIT FLOODING) 84A-A-1 (RADWASTE SHIPPING BUILDING SUMP HI LEVEL) 84A-A-2 (TURB BLD EQUIP DRAIN SUMP S-44 HI LEVEL) 84A-A-7 (TURB BLDG NORM WASTE SUMP S-45 HI LEVEL) 84A-A-10 (RADWASTE BLD DRN SUMP S-39 HI LEVEL) 84A-A-12 (TURB BLDG FLOOR DRAIN SUMP S-40 HI LEVEL) 84A-A-13 (LABORATORY DRAIN SUMP S-35 HI LEVEL) 84A-A-14 (CONVEYOR FLOOR DRAIN SUMP S-41 HI LEVEL) 5-A-49 (RADWASTE TROUBLE) 102-A-5 (DSCH STRUCTURE SUMP HI-HI LEVEL) 3.4 NRC Request - Effectiveness of Flood Protection Features Discuss the effectiveness of flood protection systems and exterior, incorporated, and temporary flood barriers. Discuss how these systems and barriers were evaluated using the acceptance criteria developed as part of Requested Information Item I

.h (Reference 5. I).

1. The purpose of the 2.3 walkdowns is to verify the conformance with the CLB; the adequacy of the CLB will be addressed as part of the NTTF Recommendation 2.1 flood reevaluations if an integrated assessment is required.

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Monticello Nuclear Generating Plant External Flooding Walkdown Report

2. The acceptance criteria for the walkdowns are described in Reference 5.2.

This approach is consistent with requested information item I

.h of the 50.54(f) letter. Discuss how the plant implemented this approach.

This discussion should include an evaluation of the overall effectiveness of the plant's flood protection features to perform their credited functions during a variety of site conditions (as defined previously), as determined by the results of the walkdowns (the features are available, functional, and implementable). The CAP process will determine which of the walkdown observations are deficiencies and what actions were taken or planned to address them. Questions such as the following should be evaluated for a variety of site conditions:

i.

Is the barrier system functional?

ii.

Are operator actions feasible?

4. Describe how other existing plant equipment, structures, and procedures might mitigate the effects of an external flood under a variety of plant configurations.

3.4.1 MNGP Response - Purpose of the Walkdowns The purpose of the external flooding walkdown was to verify the conformance of external flood features with the CLB.

In addition to the visual component of the flood feature walkdown, a review of the preventative maintenance records was performed, where appropriate. The purpose of the review was to validate that the credited features were contained in a program that would ensure their continued conformance with the CLB.

Procedures which implement flood protection features were reviewed to ensure they are executable, achievable, properly staffed, and required materials are available.

3.4.2 MNGP Response - Acceptance Criteria Development NSPM developed acceptance criteria based on Section 6 and Appendix A of NEI 12-07 (Reference 5.2). This approach is consistent with the Requested Information Item I

.h from Enclosure 4 of the 10 CFR 50.54(f) letter (Reference 5.1).

The acceptance criteria for each flood feature were annotated in Part B of the MNGP Walkdown Record Forms, where applicable.

Page 14

Monticello Nuclear Generating Plant External Flooding Walkdown Report 3.4.3 MNGP Response - Evaluation of the Overall Effectiveness of Flood Protection Features and Operator Response The results of the external flooding walkdowns show that the flood protection features and operator responses are effective overall. Deficiencies were identified during the walkdowns but do not impact the overall effectiveness of the external flooding program.

Section 3.6 of this report provides a detailed discussion of the results from the external flooding walkdowns.

3.4.4 MMGP Response - Other Existing Plant Equipment, Structures, and Procedures that Might Mitigate the Effects of an External Flood under a Variety of Plant Configurations The current licensing basis for protection and mitigation of an external flooding event, including plant equipment, structures, and procedures, is discussed in Section 3.2 of this report. No other existing plant equipment, structures, or procedures were identified as being able to mitigate an external flooding event that is not already credited in the flooding CLB.

A review of the preventative maintenance records was performed. The purpose of the review was to validate that the credited features were contained in a program that would ensure their continued conformance with the CLB. The work order planning process ensures that any scheduled maintenance activities are reviewed by plant engineering if the job scope of the work may impact the site's flooding analysis. Therefore, maintenance activities would not degrade the capability of flood protection features to perform their credited function.

3.5 NRC Request - Implementation of the Walkdown Process Present information related to the implementation of the walkdown process (e.g.,

details of selection of the walkdown team and procedures,) using the documentation template discussed in Requested Information Item I

.j (Reference 5.1), including actions taken in response to the peer review.

1. Confirm that guidance was followed (and options selected when available within the guidance) and any exceptions taken to the guidance.

2. Describe how the walkdown teams were organized (e.g., number of members, general background, etc.).

3. Describe the approach used to comply with guidance on walkdown team selection and training.

Page 15

Monticello Nuclear Generating Plant External Flooding Walkdown Report 3.5.1 MNGP Response - Guidance for Walkdown Process The NEI 12-07 guidance was followed for the external flooding walkdown scoping, execution, and documentation. No exceptions were taken to the guidance.

A walk-through of Section 5.0 of Procedure A.6, "Acts of Nature", was performed as part of the external flooding walkdown to ensure site preparation and response for the licensing basis flood event were adequate and could be completed within acceptable time under the conditions expected. Additional details are discussed in Section 3.6.1 of this report.

3.5.2 MNGP Response - Walkdown Team Organization The MNGP flood walkdown team was composed of three (3) qualified individuals of various technical disciplines. The walkdown team members represented discipline areas with complimentary skill sets that included fieldtinspection experience, design engineering, knowledge of plant flood protection features, and knowledge of the current MNGP external flooding licensing basis.

3.5.3 MNGP Response - Walkdown Team Selection and Training In accordance with Section 5.3 of NEI 12-07 (Reference 5.2), multiple skill sets were available to participate in the evaluation of a given flood mitigation feature depending on the intended credited function. Each flood mitigation feature was evaluated by a minimum of two individuals from the team.

The flood walkdown team was made familiar with the information required to respond to the NRC's 10 CFR 50.54(f) request for information (Enclosure 4 of Reference 5.1). The walkdown team members completed the training developed by the NEI Fukushima Flooding Task Force and available through the INPO NANTEL website (Appendix C of Reference 5.2). All training records for flood feature walkdown team participants are documented in the MNGP training records database.

3.6 NRC Request - Results of Flooding Walkdown Summarize results of the walkdown including key findings and identified degraded, non-conforming, or unanalyzed conditions. Include a detailed description of the actions taken or planned to address these conditions using the guidance in Regulatory Issues Summary 2005-20, Rev I, Revision to NRC Inspection Manual Part 9900 Technical Guidance, "Operability Conditions Adverse to Quality or Safety," including entering the condition in the corrective action program.

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Monticello Nuclear Generating Plant External Flooding Walkdown Report

1. Description of all deficiencies as determined by the CAP. Observations that are entered into the CAP and not dispositioned as deficiencies do not need to be reported.

2. Description of any observations reported in the CAP that were not dispositioned at the time of the report.

3. Describe actions that were taken or are planned to address the deficiencies using the guidance in Regulatory Issues Summary 2005-20 Revision 1.

4. Flood protection features that could not be inspected, including:

i.. Features affected by restricted access:

. Justification for delay Schedule Any necessary special procedures ii, Inaccessible features:

Basis for reasonable assurance that the feature is available and will perform its credited function or an assessment of the impact of non-performance of the function.

If more than one "inaccessible" flood protection feature with potential loss of function is reported, then an evaluation of the aggregate effect flood protection features must be provided.

3.6.1 MNGP Response - Results of Flooding Walkdown Summarv of Findings The plant flood protection features were found to be as described in the CLB (available, functional, and maintained), with the exceptions that are considered deficiencies and restricted access. Deficiencies are described in Table 3.6-1, "Deficiency List." Observations identified during the external flooding walkdowns are listed in Table 3.6-2, "Observation List." Table 3.6-3, "Restricted Access,"

provides a list of the restricted access features as well as actions to inspect each feature. There were no flood protection features identified as inaccessible during the external flooding walkdowns. Deficiencies and Restricted Access features notwithstanding, the flood protection features in aggregate would perform their design function as credited in the CLB. Eighty-one (81) walkdown record forms were created, following the NEI 12-07 guidance, of the specific features included within the scope of the walkdown record forms.

Page 17

Monticello Nuclear Generating Plant External Flooding Walkdown Report Eighty (80) walkdown record forms are for physical flood features.

o Twenty-two (22) walkdown record forms contain specific areas or components that were determined to be subject to restricted access and were entered into the CAP or work management system for future disposition and scheduling (Refer to Table 3.6-3).

o Eight (8) action requests were initiated and then evaluated using the NEI 12-07 guidance to determine if a deficiency existed. Two (2) deficiencies were identified (Refer to Table 3.6-1) from this review. The six action requests which were not identified as deficiencies are listed in Table 3.6-2.

o Five (5) features credited in the CLB were included in a preventative maintenance or surveillance program. A maintenance program review was performed and determined that these flood protection features are functional and maintained. No deficiencies were identified.

o Although not credited as part of the external flooding CLB, 22 walkdown record forms were completed for active equipment which included level sensors and pumps located in plant areas that provide indication of water intrusion from internal or external sources. A review of maintenance records was performed and determined that these flood protection features are functional and maintained. No adverse conditions were identified.

One (1) walkdown record form was completed for procedures. Section 5 of the MNGP Procedure A.6, "Acts of Nature," outlines actions to be taken in the event flood waters are predicted to exceed elevation 91 8 ft. Specific aspects of Procedure A.6 related to protection of SSCs important to safety were evaluated using a methodology consistent with that described in the NEI 12-07 guidance.

o Walkthroughs of actions in Procedure A.6, that are related to protection of SSCs important to safety, consisted of reviewing the time required to complete the actions, personnel requirements and availability, resource requirements and availability, and any impacts due to adverse conditions (either from the event it is intended to mitigate or other adverse conditions that could reasonably be expected to simultaneously occur).

o Steps in Procedure A.6 assigned to departments, such as Maintenance or Plant Operations, are within normal training, experience and skill of the craft, and no specialized training is considered necessary.

o Performance of the procedure walkthroughs resulted in 23 suggested enhancements to improve the clarity in the procedure, increase overall preparedness, and streamline actions needed to Page 18

Monticello Nuclear Generating Plant External Flooding Walkdown Report protect SSCs important to safety. These enhancements are recorded in Table 3.6-2 as an observation.

o Two (2) deficiencies were identified by the walkthroughs and are listed in Table 3.6-1 of this report.

3.6.1.I Deficiencies Refer to Table 3.6-1, "Deficiency List," for the identified deficiencies, including a brief description of the feature, the reported degraded condition, and actions assigned with the anticipated completion date.

3.6.1.2 Observations In accordance with the NEI 12-07 guidance, NSPM has dispositioned the observations identified during the external flooding walkdowns. Only four (4) observations were determined to be deficiencies. Six (6) observations entered into site action requests were determined to be enhancements to the flooding protection features or strategies. Table 3.6-2, "Observation List," lists these observations, including a brief description of the flood protection feature, comments on the observation, and an action request number.

3.6.1.3 Describe Actions to address the Deficiencies The actions planned to address the deficiencies are described in Table 3.6-1, "Deficiency List." NSPM will complete resolution of deficiencies by February 15, 201 3.

3.6.1.4 Restricted and Inaccessible Flood Protection Features Table 3.6-3, "Restricted Access" lists those items that were not inspected during the course of the MNGP external flooding Walkdown including the basis for delay. No special procedures are required for inspection of the restricted-access features. There were no flood protection features identified as inaccessible during the external flooding walkdowns.

The anticipated completion date for inspection of the restricted access items is October 31, 201 3.

Page 19

Monticello Nuclear Generating Plant External Flooding Walkdown Report 3.7 NRC Request - Available Physical Margin (APM)

Report that APM has been collected and documented in the Walkdown Record Form.

3.7.1 MNGP Response - Documentation of Available Physical Margin The APM has been estimated and documented, as applicable, in the walkdown record forms in accordance with NEI 12-07. This informati~n will be used in the flood hazard reevaluations performed in response to NTTF Recommendation 2.1: Flooding of the NRC's 10 CFR 50.54(f) letter (Reference 5.1).

3.8 NRC Request - Other PlannedlNewly Installed Flood Protection Features or Mitigation Measures Describe any other planned or newly installed flood protection systems or flood mitigation measures including flood barriers that further enhance the flood protection. Identify results and any subsequent actions taken in response to the peer review. Describe changes determined to be necessary by the flood walkdowns and whether they have been completed or their schedule for completion.

3.8.1 MNGP Response - PIannedlNewly Installed Flood Protection Features or Mitigation Measures A number of observations were identified which could improve the clarity in the A.6 procedure, increase overall preparedness, and streamline actions already contained within the A.6 Procedure. These observations are contained in Table 3.6-2. Additionally, changes will be made as part of the resolution of the deficiencies identified in Table 3.6-1. However, none of these changes constitute new flood protection or mitigation features. NSPM has not installed or does not plan to install any new flood protection features, or implement any new flood mitigation features.

Page 20

Monticello Nuclear Generating Plant External Flooding Walkdown Report

4.0 CONCLUSION

S The identified plant flood-protection physical features were found to be as described in the CLB (available, functional, and maintained) with those exceptions as described in Table 3.6-1, "Deficiency List." The results of the external flooding walkdown show that the flood protection features and operator responses are effective overall. Deficiencies were identified during the walkdowns but do not impact the overall effectiveness of the external flooding walkdown.

4.1 Deficiencies A total of four (4) deficiencies were identified as a result of the walkthroughs and are summarized in Table 3.6-1, "Deficiency List". The deficiencies were entered into the CAP.

4.2 Observations Table 3.6-2, "Observation List," lists six (6) observations identified during the external flooding walkdowns as enhancements to the external flooding program.

4.3 Restricted-Access Flood Features Table 3.6-3, "Restricted Access," lists those flood features that were deemed restricted access and require future scheduling and disposition. Restricted access features have been entered into the CAP or work management system for tracking. All restricted-access features will be tracked by their respective work orders and visually inspected by October 31, 201 3.

4.4 Inaccessible Flood Features There was no flood protection features determined to be inaccessible during the external flooding walkdowns.

Page 21

Monticello Nuclear Generating Plant External Flooding Walkdown Report REFERENCES NRC Letter to Licensees, dated March 12, 201 2, "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" (ADAMS Accession No. MLI 2053A340).

NEI 12-07, Revision 0-A, "Guidelines for Performing Verification Walkdowns of Plant Flood Protection Features," dated May 2012 (ADAMS Accession No. MLI 21 73A215).

NRC Letter to Nuclear Energy lnstitute (NEI) dated May 31, 2012, "Endorsement of Nuclear Energy Institute (NEI) 12-07, "Guidelines for Performing Verification Walkdowns of Plant Flood Protection Features,"

(ADAMS Accession No. MLl2144A142).

SECY-I 1-0093, "Near-Term Report and Recommendations for Agency Actions Following the Events in Japan," dated July 12, 201 1 (ADAMS Accession No. MLI 11861807).

SRM SECY 11-0124, "Recommended Action to be taken without Delay from the Near-Term Task Force Report," dated October 18, 201 1 (ADAMs Accession No. MLI 1291 1571).

SRM SECY 11-0137, "Prioritization of Recommended Actions to Be Taken in Response to Fukushima Lessons Learned," dated December 15,201 1 (ADAMS Accession No. MLI 13490055).

Department of the Army, Office of the Chief of Engineers, the U.S. Army Corps of Engineers, Engineer Circular No. 11 10-2-27, Enclosure 2, "Policies and Procedures Pertaining to Determination of Spillway Capacities and Freeboard Allowances for Dams," dated August 1, 1966.

Architect-Engineer Study MNTS 048, 82-002-SPEC, "Flood Protection Requirements for Maximum Probable Flood."

Monticello Nuclear Generating Plant, Updated Safety Analysis Report (USAR Revision 28).

NSPM Letter to NRC, "Potential Loss of Fuel Oil Transfer Capability during External Flooding Due to Procedural Inadequacy," (LER 90-019-01) dated April 24, 1991.

Page 22

Monticello Nuclear Generating Plant External Flooding Walkdown Report Table 3.6-1: Deficiency List Page 23 Anticipated Completion Date February 15,2013 February 15,2013 February 15,2013 February 15,2013 CAP Action Request No.

01 3581 77 01358177 01 3581 77 01 353929 Actions Revise Procedure A.6 to remove pathway.

Actions to mitigate effects from flood water could include, but are not limited to 1) replacing windows or 2) revising Procedure A.6 to include sandbag berm in PAB Control Building.

Revise Procedure A.6 to clarify protection of tank T-44.

Revise Procedure A.6 to provide improved method of sealing the gap.

Condition Provides a path for flood water to enter the PAB Control Building.

Provides a potential path for flood water to enter the PAB Control Building.

Current step 5.2.1 1.B is not in agreement with step 5.2.1 1.H regarding protection of tank T-44 if the ring levee option is not chosen.

Successful completion of step 5.2.9.1 may not be assured as currently written.

No.

1 2

3 4

Description of Feature Penetrations in Plant Administration Building (PAB) 939 Telephone Room Windows in PAB Lunchroom Conflict with steps in Procedure A.6 to protect tank T-44 Seal gap between the Intake Structure and access tunnel or between the tunnel and Turbine Building (Procedure A.6, Step 5.2.9.1)

Monticello Nuclear Generating Plant External Flooding Walkdown Report Table 3.6-2: Observation List 1 Flood Protection I 1

Feature 1

Observation Action Request No.

Comments USAR section 12.2.1.7.1 needs clarification.

lntake Structure 01354211 1 USAR will be revised and actions taken, if appropriate.

Penetrations were found in the lntake Structure that allow water to enter the lntake structure during a PMF.

1 01356612 1 No safety related cables are located in this conduit.

1 Off Gas Stack Reactor building, Turbine building 01 353461, 01354075 Corroded electrical conduit.

Multiple Procedure A.6 requires plugging open penetrations when a PMF is predicted.

Flooding Procedure A.6 does not adequately identify when construction should begin on a temporary berm.

Improvement opportunities identified in the Procedure A.6 walk through. 23 observations are to be evaluated for improvements to NSPM's response to a PMF.

Flooding procedure should be enhanced to clarify temporary berm instruction.

The improvements will be evaluated and actions taken, if appropriate. A procedure change request has been initiated to incorporate identified improvements.

1 I

1 1 Procedure A.6 requires plugging open I

Multiple referenced in Procedure A.6.

Open penetrations were found during the flooding walkdowns.

Page 24 01 353659 penetrations when a PMF is predicted.

Recommend that a Flooding Penetration Database be created, and

Monticello Nuclear Generating Plant External Flooding Walkdown Report Table 3.6-3: Restricted Access No.

Location DescriptionIJustification Work Order No.

Remarks 1

Intake Structure - Elev. 919' Inspect Conduit Penetration 466385, Task 01 May Require Opening for Seal 1 Install Scaffolding.

Junction Box Other Side of Wall. See CAP 01354075.

2 Intake Structure - Elev. 919' Remove Insulation /Verify 466385, Task 02 Three Sodium Hypochlorite Floor Penetration Sealed.

Lines. See CAP 01 354075.

3 Intake Structure Elev. 916' - Verify Conduit Penetration is 466385, Task 12 Open Ended Conduit. See Alcove Area Sealed 1 Install Scaffolding.

CAP 1354075.

RClC Room - North Wall Open Junction Boxes North 466385, Task 04 Verify if Penetrations Exist at (Reactor Building Elev. 896')

Wall I Inspect Penetration.

Junction Box and Properly Sealed. See CAP 01 354536.

HPCI Room -West Wall Inspect Penetrations for Seals 466385, Task 05 Three Piping Penetrations to (Reactor Building Elev. 896')

1 Install Scaffolding.

be Inspected. See CAP 01 354530.

HPCI Room - West Wall Inspect Penetrations for Seals 466385, Task 06 Two Piping Penetrations to be (Reactor Building Elev. 896')

1 Install Scaffolding.

Inspected. See CAP 01 354530.

Reactor Building Tank Room Open Junction Boxes North 466385, Task 15 Verify if Penetrations Exist at

- North Wall (Reactor Wall 1 Install Scaffolding &

Junction Box and are Properly Building Elev. 896')

Inspect Penetrations.

Sealed. See CAP 01 354534.

1 1 & 12 Emergency Diesel Open Floor Trenches I 466385, Task 07 Remove Trench Covers.

Generator Room - Elev.

Perform Inspections.

931' Open Junction Box / Inspect Penetration.

Page 25

Monticello Nuclear Generating Plant External Flooding Walkdown Report Table 3.6-3: Restricted Access Page 26 No.

lo 1 1 12 Location Turbine Building Elev. 931' -

~ o r t h ~ a l l Lower 4 KV Room Entryway

- North Wall (Turbine Building Elev. 91 1')

MVP Room - Northeast Corner (Turbine Building Elev. 908')

Lower 4 KV Room - North Wall (Turbine Building Elev.

91 1')

Remarks Remove Metal Jacketed Insulation I Inspect Penetration.

Verify Seal on Outside of Wall.

Identify Unknown Penetration.

Verify Piping Penetration, Unknown Penetration, and Conduit Penetration are Sealed I Install Scaffolding.

Two Conduits Located Behind Raceway.

Three Junction Boxes (J-681, J-317, J-101) with Conduit Penetrations.

Two Conduits Into Junction BOX J-102.

Three Conduit Penetrations (Elev. 929').

DescriptionlJustification Insulation conceals pipe penetration seal.

Drain Pipe Penetration. Verify Piping Penetration Sealed.

Unable to directly view penetrations.

Open Junction Boxes. Verify Conduit Penetrations are Sealed I Install Scaffolding Work Order No.

466385, Task 08 466385, Task 13 466385, Task 09 466385, Task 14

Monticello Nuclear Generating Plant External Flooding Walkdown Report Table 3.6-3: Restricted Access Page 27 No.

13 14 15 16 17 Work Order No.

466385, Task 16 466385, Task 10 466385, Task 17 466385, Task 18 466385, Task 19 Remarks Verify if Penetration Exists and is Properly Sealed for Junction Box NJ5220.

One conduit lnto Junction Box J-313.

Two Conduits lnto Junction BOX J-289.

Two Conduits lnto Junction BOX J-312.

Verify Obstructed Conduit Rout. If Penetration Exists, Verify Seal.

Remove Visual Obstruction.

Complete Inspection.

Verify Junction Box (2J-4001, 2J-4002, 2J-6003) Conduit Penetrations are Sealed.

Verify Junction Box (1 J-3121 and 1 J-3225 Conduit Penetrations are Sealed.

Verify Bottom 2 Feet of Wall is Properly Sealed.

Location Lower 4 KV Room - West Wall (Turbine Building Elev.

91 1')

Turbine Building Elev. 91 1' -

East Wall Emergency Filtration Train (EFT) Elev 932' -West Wall Office & Control Building Elev. 928' (125 V Battery Room)

Office & Control Building Elev. 939' Description/Justification Open Junction Boxes. Verify Conduit Penetrations are Sealed / Install Scaffolding.

Inspect Piping Penetrations for Seals / Grout.

Open Junction Boxes. Verify Conduit Penetrations are Sealed.

Open Junction Boxes. Verify Conduit Penetrations are Sealed.

Door Opening Replaced with Wall. Covered with Sheetrock.

Verify Wall is In-filled with Concrete/Sealed.

Monticello Nuclear Generating Plant External Flooding Walkdown Report Table 3.6-3: Restricted Access Page 28 Remarks Install cap on conduit as needed.

Conduit does not correspond to any known equipment.

None.

None.

None.

None.

None.

None.

None.

Work Order No.

466385, Task 11 466385, Task 27 466385, Task 26 466385, Task 20 466385, Task 21 466385, Task 22 466385, Task 23 466385, Task 25 466385, Task 24 DescriptionlJustification Conduit Penetrations / Install Scaffolding & Verify Conduit Penetrations Sealed.

Inspect Open Conduit Penetration. Verify seal.

Complete lnspection 1 Locked High Radiation Area Complete lnspection 1 Locked High Radiation Area Complete lnspection 1 Locked High Radiation Area Complete lnspection 1 Locked High Radiation Area Complete lnspection 1 Locked High Radiation Area Complete lnspection / Locked High Radiation Area Complete Inspection /

Confined Space No.

18 19 20 21 22 23 24 25 26 Location Intake Structure Tunnel Extension Elev. 91 6' - West Wall Intake Structure Elev. 91 6' (East Wall Tunnel Extension)

Reactor Building Elev. 935' -

Steam Chase Condenser Room (Turbine Building Elev. 91 1')

Condensate Resin Receiver Tank Room (Turbine Building Elev. 908')

Steam Jet Air Ejector Room (Turbine Building Elev. 91 1')

Condensate Demineralizer Area (Turbine Building Elev.

937')

Compressed Gas Storage Building Diesel Fuel Oil Storage Tank (Elev. 930')

Monticello Nuclear Generating Plant External Flooding Walkdown Report Table 3.6-3: Restricted Access Page 29 Remarks None.

None.

No.

27 28 Location Office and Control Building (Elev. 928')

North Wall (Turbine Building Elev. 91 1')

Description/Justification Verify Penetrations are Sealed I Install Scaffolding.

Verify Penetrations are Sealed I Install Scaffolding.

Work Order No.

466385, Task 29 466385, Task 30