ML13233A068

Monticello Nuclear Generating Plant - Response to an Apparent Violation in NRC Inspection Report 05000263/2013008 (EA-13-096)

ML13233A068
Person / Time
Site:	Monticello
Issue date:	07/11/2013
From:	Schimmel M A Northern States Power Co, Xcel Energy
To:	Document Control Desk, NRC/RGN-III
References
EA-13-096, L-MT-13-062 IR-13-008
Download: ML13233A068 (99)

See also: IR 05000263/2013008

Text

Monticello

Nuclear Generating

Plant XcelEnergy

2807 W County Road 75 Monticello, MN 55362 July 11, 2013 L-MT-13-062

EA-13-096 U.S. Nuclear Regulatory

Commission

ATTN: Document Control Desk Washington, DC 20555-0001

Monticello

Nuclear Generating

Plant Docket 50-263 Renewed Facility Operating

License No. DPR-22 Response to an Apparent Violation

in NRC Inspection

Report 05000263/2013008 (EA-1 3-096)References:

1) Letter from Nuclear Regulatory

Commission (NRC) to Mr. Mark A.Schimmel, "Monticello

Nuclear Generating

Plant, NRC Inspection

Report 05000263/2013008;

Preliminary

Yellow Finding," dated June 11, 2013 (Accession

Number ML13162A776)

2) Letter from Northern States Power -Minnesota

to NRC, "Notification

of Intention

Regarding

NRC Inspection

Report 05000263/2013008 (EA-13-096)," dated June 19, 2013 By the above referenced

letter dated June 11, 2013, the NRC transmitted

Inspection

Report 05000263/2013008

for the Monticello

Nuclear Generating

Plant (MNGP). In the inspection

report, the NRC identified

one finding and apparent violation

with a preliminary

significance

of Yellow for MNGP. In the referenced

letter, the NRC stated that the site had failed to maintain a flood procedure, A.6, "Acts of Nature", such that it could support the timely implementation

of flood protection

activities

within the 12 day timeframe

credited in the design basis, as stated in the updated safety analysis report (USAR).Northern States Power Company -Minnesota (NSPM) reviewed the apparent violation and, pursuant to the provisions

of the choice letter, prepared a written response to the apparent violation.

NSPM agrees that the failure to maintain a flood plan to protect the site from external flooding events is a violation

of Technical

Specification

5.4.1.a.This letter submits additional

information

for the NRC's consideration

in its final determination

of the significance

of the apparent violation.

The enclosures

address the following:

e-7A

Document Control Desk L-MT-1 3-062 Page 2 of 5 Response to Apparent Violation (Enclosure

1)NSPM agrees that the failure to maintain an adequate flood plan to protect the site from external flooding events is a violation

of Technical

Specification

5.4.1 .a. NSPM is taking this failure to protect the site from external flooding very seriously

and has used it to reinforce

NSPM's policy and commitment

to safety as a top priority in our Emergency Response plans, response to acts of nature, and effective

corporate

governance

and oversight.

The site and nuclear fleet are taking corrective

actions to ensure protection

of the radiological

health and safety of the public in the event of an external flooding worst case scenario.

A summary of the corrective

actions to resolve the performance

deficiency

is presented

in Enclosure

1.As part of those actions, NSPM is performing

cultural assessments

focusing on decision making, effective

communication, and closure follow-through

not only at the site levels, but across the nuclear fleet to maximize learning from this situation.

Probabilistic

Risk Analysis (Enclosure

2)NSPM developed

additional

information

providing

further insight into the probability

of a Probable Maximum Flood (PMF) at the Monticello

site for the NRC's consideration.

The report provides probabilistic

risk analyses to support a best-estimate

assessment

of the significance

of this finding as well as bounding analyses to support final significance

determination

prior to corrective

actions taken by the site. The best-estimate

analysis incorporated

the assumptions

necessary

to support the assessment

of a finding related to an external flooding event. Results are shown in the table below: Nominal, Best Sensitivity

1: Sensitivity

2: Estimate Bounding Flood SPAR-H HRA Freauencv

Probabilities

CDF 1.04E-06 3.1 OE-06 1.83E-06 ACDP 8.92E-07 2.66E-06 1.57E-06 The full results of the event tree quantification

are summarized

in Enclosure

2.Monticello

Nuclear Generating

Plant Flood Protection

Analysis (Enclosure

3)The postulated

PMF for the MNGP is compared to other site Mississippi

river conditions

in the table below. The PMF is not an instantaneous

event, but rather a slowly developing

evolution

that allows for plant staff to monitor, predict, prepare, and implement

appropriate

actions to provide the required flood protection.

Since actions have been taken to procure the bin wall and levee materials, performance

of a reasonable

simulation

demonstrated

that the levee and bin wall system can now be installed

within the available

time as defined in the licensing

basis.

Document Control Desk L-MT-1 3-062 Page 3 of 5 Normal and Flooded River Flow Rates and Water Elevations

Mississippi

River Flow Rate (cfs) Water Elevation Condition (ft. msl)Normal 4,600 905 Maximum Recorded 51,000 916 (1965)1000 Year Flood -90,000 (1) 921 Probable Maximum 364,900 939.2 Flood 364,900_ 939.2 A report entitled "Monticello

Flood Protection," was prepared for Monticello

and addresses

the aspects of flood protection

for which MNGP was licensed and is included in Enclosure

3.Annual Exceedance

Probability (Enclosure

4)Annual river exceedance

probabilities

based on annual peak flood estimates

at the Monticello

site were developed

to support the probabilistic

risk assessment.

The probability

of a PMF at the site was determined

to be extremely

low.Enclosure

4 provides a copy of the report entitled, "Annual Exceedance

Probability

Estimates

for Mississippi

River Stages at the Monticello

Nuclear Generating

Plant based on At-site Data for Spring and Summer Annual Peak Floods", June 28, 2013, developed by RAC Engineers

& Economists.

Stakeholder

Outreach (Enclosure

5)NSPM hosted an open house to share information

with its community

neighbors

on its operations

and preparedness

to handle potential

emergencies

and how it would respond to flooding, earthquakes

and other unforeseen

challenges.

The key message presented

to visitors was that safety and security at the NSPM nuclear generating

plants are top priorities

for Xcel Energy. Further, that we understand

the industry, NRC, and public's demand of higher safety standards

and flood preparedness

at the nation's nuclear power plants in the wake of events such as 9/11 and Fukushima Daiichi. The Monticello

Flood Protection

Strategy was identified

and explained

to demonstrate

that the site is capable of withstanding

a PMF and that the site is incorporating

lessons learned from the industry to improve and assure protection

methods.Safety Culture Review NSPM agrees it missed an opportunity

within its control to identify challenges

to the implementation

of the A.6 procedure, leading to the identified

apparent violation.

As such, NSPM assembled

an expert panel to examine the behavioral

and cultural aspects impacting

decision making within the nuclear business unit. This activity was chartered

Document Control Desk L-MT-13-062

Page 4 of 5 as an immediate

and interim measure preceding

the extensive

root cause evaluation

that will be performed

to identify the full magnitude

of this issue, associated

causes, and corrective

actions to prevent recurrence.

This expert panel assembled

to examine safety culture within its nuclear organization

was comprised

of five independent

consultants

and one Xcel representative.

The team reported directly to the Vice President

of Nuclear Operations

Support. A phased approach is being utilized to examine the behavioral

and cultural aspects impacting decision making within the nuclear business unit. Three phases are planned to examine this subject: Phase (1) is specifically

focused on the Monticello

flooding issue, Phase (2)more broadly examines Monticello

issues and Phase (3) examines Prairie Island issues.While the phases are specific to the individual

sites, the scope includes developing

an understanding

of the corporate

culture and influence

beyond a site-centric

examination

of the behavioral

and environmental

influences.

To date Phase (1) has been completed with scheduling

of Phase (2) and (3) expected to commence and complete over the next few months. The initial phase identified

improvement

opportunities

in the areas of decision making, leadership

behaviors, and questioning

attitude regarding

the station's preparedness

for a PMF. The results of this assessment

have been insightful

and will be applied across the nuclear fleet to ensure a healthy safety culture exists. Opportunities

have been identified

to strengthen

fleet and Nuclear Oversight

accountability

for providing

oversight

to proactively

detect performance

gaps.Interim actions are in place for the short term to focus on the areas for improvement, and longer term actions are in development.

Summary NSPM respectfully

requests that the NRC consider the enclosed information

in its final determination

of the significance

of the finding. Notwithstanding

our assessment

of the significance

of the finding, NSPM clearly understands

our performance

shortcomings

concerning

flood protection

for the entire spectrum of possible flooding events at the MNGP. Corrective

actions have already been completed

to address the NRC's identified

performance

deficiency.

Additionally, we unequivocally

acknowledge

the need for overall performance

improvement

at MNGP. Actions are underway to ensure that the lessons learned from this finding are applied more broadly to overall performance.

Summary of Commitments

This letter contains no new commitments

and no revisions

to existing commitments.

Mark A. Schimmel Site Vice-President

Monticello

Nuclear Generating

Plant Northern States Power Company-Minnesota

Document Control Desk L-MT-1 3-062 Page 5 of 5 Enclosures:

Enclosure

1 -Response to Apparent Violation Enclosure

2 -External Flooding Evaluation

for Monticello

Nuclear Generating

Plant Enclosure

3 -Monticello

Flood Protection

Enclosure

4 -Annual Exceedance

Probability

Estimates Enclosure

5 -Stakeholder

Outreach cc: Regional Administrator, Region III, USNRC Project Manager, Monticello

Nuclear Generating

Plant, USNRC Resident Inspector, Monticello

Nuclear Generating

Plant, USNRC

Enclosure

I Response to Apparent Violation EA-1 3-096 NRC Inspection

Report 05000263/2013008

Monticello

Nuclear Generating

Plant 3 Pages Follow

Northern States Power Company -Minnesota Response to Preliminary

Yellow Finding NRC Finding Summary The inspectors

identified

a preliminary

Yellow finding with substantial

safety significance

and associated

apparent violation (AV) of Technical

Specification

5.4.1 for the licensee's

failure to maintain a flood plan to protect the site from external flooding events. Specifically, the site failed to maintain flood Procedure

A.6, "Acts of Nature," such that it could support the timely implementation

of flood protection

activities

within the 12 day timeframe

credited in the design basis as stated in the updated safety analysis report (USAR).The inspectors

determined

that the licensee's

failure to maintain an adequate flood plan consistent

with the USAR was a performance

deficiency, because it was the result of the failure to meet the requirements

of TS 5.4.1 .a, "Procedures;" the cause was reasonably

within the licensee's

ability to foresee and correct; and should have been prevented.

The inspectors

screened the performance

deficiency

per Inspection

Manual Chapter (IMC) 0612, "Power Reactor Inspection

Reports," Appendix B, dated September

7, 2012, and determined

that the issue was more than minor because it impacted the 'Protection

Against External Factors' attribute

of the Mitigating

Systems Cornerstone

and affected the cornerstone's

objective

to ensure the availability, reliability, and capability

of systems that respond to initiating

events to prevent undesirable

consequences (i.e. core damage). Specifically, if the necessary

flood actions cannot be completed

in the time required, much of the station's

accident mitigation

equipment

could be negatively

impacted by flood waters.NRC Baseline Significance

Determination

Process Review As part of the process, the Region III Senior Reactor Analyst (SRA) developed

an event tree model to perform a bounding quantitative

evaluation.

The model presents an external flood event that exceeds grade level (930 ft. MSL) and requires implementation

of Procedure

A.6, "Acts of Nature" Section 5.0.NSPM Response NSPM agrees that a performance

deficiency

exists. Procedure

A.6, "Acts of Nature", at the time of the violation, did not provide sufficient

guidance to execute mitigation

strategies

for a probable maximum flood (PMF) event. Adequate management

oversight

and engagement

was not provided to ensure that the Monticello

external flood mitigation

procedure

and strategies

met expected industry standards

and licensing

basis requirements.

Actions have been completed

to reduce the flood mitigation

plan timeline by pre-staging

equipment

and materials

required for bin-wall levee construction, improving

the quality of the A.6 "Acts of Nature" procedure

and pre-planning

work orders necessary

to carry out the A.6 actions.Summary of Corrective

Actions: Acquired materials

required for flood mitigation

including, but not limited to: " Hardware and components

for construction

of Bin-Wall" Clay for levee construction

(30000 cubic yards)* Rip-Rap stone for levee construction

(1700 cubic yards)Page 1 of 3

• Sand for levee construction

and filling sandbags (11000 cubic yards)" Sand bagging machine (Capacity

1600 sand bags/hr)* Manual sand bag filling tools (25 on site)" Gas Sump Pumps* Electric Sump Pumps" Crushed concrete for alternate

road access (2400 cubic yards)* Preventative

maintenance

plans are being developed

for new flood mitigation

equipment* Performance

of reasonable

simulation

of major steps required by procedure

A.6 "Acts of Nature" Section 5.0, including

building of bin-wall sections, sandbagging, placement

of various covers, and relocation

of vital equipment.

• Extensive

procedure

revisions

to enhance feasibility

of actions and reduce overall time required to execute the strategy.* Table top exercises

of new revisions

performed

to ensure practicality.

• Development

of work orders to provide more detail for execution

of steps within procedure A.6, "Acts of Nature" Section 5." The existing flood prediction

surveillance

was revised to occur on a monthly basis instead of yearly and contains provisions

to continually

monitor river predictions

if certain conditions

are met.* Meetings with the National Weather Service were held to develop more robust prediction

capabilities

and options.* Enhanced construction

drawings of levee and bin-wall to provide more detail* Updated existing contracts

and memorandums

of understanding

with vendors to assure equipment

availability.

• A modification

is also in the design phase to install the base of the bin-wall on the west side of the Intake structure, simplify construction

on the east side of the Intake Structure, and also update the steel plate design for protection

of the Intake Structure.

Review of NRC Significance

Determination

NSPM has developed

additional

information

providing

new insight into the probability

of a PMF at the Monticello

site for your consideration.

A report entitled "External

Flooding Evaluation

for Monticello

Nuclear Generating

Plant" was prepared by Hughes Associates, Inc., for NSPM. The report provides a best-estimate

assessment

of the significance

of this finding. Two (2)sensitivities

were performed

to assess the bounding risk, addressing

some of the uncertainty

associated

with this assessment.

The first sensitivity

study provides the risk assessment

if a bounding annual exceedance

probability

is assumed. As noted in the Hughes' report, the uncertainty

associated

with extreme flooding can be addressed

by artificially

restraining

the AEP to a value of no less than 1 E-05/year.

When this restraint

is assessed, the ACDP is 2.66E-06.Enclosure

4 of this letter provides a copy of the report entitled, "Annual Exceedance

Probability

Estimates

for Mississippi

River Stages at the Monticello

Nuclear Generating

Plant based on At-site Data for Spring and Summer Annual Peak Floods", June 28, 2013, developed

by RAC Engineers

& Economists.

The second sensitivity

address the different

methodologies

available

for quantifying

the Human Error Probability (HEP) associated

with the manual operation

of RCIC (Reactor Core Isolation Cooling) and HPV (Hard Pipe Vent). This sensitivity

provides quantification

using The SPAR-H Page 2 of 3

Human Reliability

Analysis Method, NUREG/CR-6883.

When the simplified

SPAR-H methodology

is used, the assessment

results in a ACDP of 1.57E-06.The result of the nominal, best-estimate

assessment

and the two (2) sensitivities

performed

are shown in the table, below, for ease of reference.

Sensitivity

1: Bounding Flood Frequency Sensitivity

2: SPAR-H HRA Probabilities

Nominal Best-Estimate CDF 1.04E-06 3.1OE-06 1.83E-06 ACDP 8.92E-07 2.66E-06 1.57E-06 Enclosure

2 of this letter provides a copy of a report entitled, Report Number 1SML16012.000-1,"External

Flooding Evaluation

for Monticello

Nuclear Generating

Plant," developed

by Hughes Associates

for consideration.

Page 3 of 3

Enclosure

2 Monticello

Nuclear Generating

Plant"External

Flooding Evaluation

for Monticello

Nuclear Generating

Plant" ISMLI16012.000-1

Hughes Associates

62 Pages Follow

.IHUGHES EASSOCIATES

ENGINEERS

CONSULTANTS

SCIENTISTS

External Flooding Evaluation

for Monticello

Nuclear Generating

Plant 1SML16012.000-1

Prepared for: Xcel Energy Project Number: 1SML16012.000

Project Title: Monticello

External Flooding SDP Revision:

1 Name Date Preparer:

Erin Collins/Paul

Amico/Suzanne

Loyd 7/8/2013~ ~" Erin P. Collins 2013.07.082018:01

-04-00-Reviewer:

Pierre Macheret 7/8/2013 P.",: 2"13 007 .M0 1-. o U.Review Method Design Review E] Alternate

Calculation

E]Approved by: Francisco

Joglar Francisco

Joglar. ,. 7/8/2013 N. I l: "013.07-

ISML-16012.000-1

Table of Contents TABLE OF CONTENTS 1.0 INTRODUCTION

..................................................................................................

1 2.0 REFERENCES

.................................................................................................

2 3.0 METHODOLOGY

and analysis ........................................................................

4 3.1 Event Tree Analysis .............................................................................

4 3.1.1 Evaluation

of Flood Frequency

...................................................

4 3.1.2 Early W arning Probability

...........................................................

7 3.1.3 Protection

of the Reactor Building ...............................................

7 3.1.4 Manual Local Operation

of RCIC and the Hard Pipe Vent ..........

8 4.0 CONCLUSIONS

.............................................................................................

15 APPENDICES

TABLE OF CONTENTS ...................................................................

16 Revision I Page ii

1SML16012.000-1

Introduction

1.0 INTRODUCTION

This analysis was developed

to address the significance

of a finding that was received by the Monticello

Nuclear Generating

Plant (MNGP) associated

with External Flooding hazards. This SDP is summarized

in NRC Letter EA-13-096 (Reference

5). The analysis quantifies

the core damage frequency

associated

with a flood exceeding

930' at MNGP.Revision 2 Page 1 Revision 2 Page1I

ISML16012.000-1

References

2.0 REFERENCES

1. Annual Exceedance

Probability

Estimates

for Mississippi

River Stages at the Monticello

Nuclear Generating

Station based on At-Site Data for Spring and Summer Annual Peak Floods, David S. Bowles and Sanjay S. Chauhan, RAC Engineers

and Economists, June 28, 2013.2. Hydrologic

Atlas of Minnesota, Division of Water, Department

of Conservation, State of Minnesota, 1959.3. US Geological

Survey, Guidelines

for Determining

Flood Flow Frequency, Bulletin#17B, Hydrology

Subcommittee, Interagency

Committee

on Water Data, Office of Water Data Coordination, 1982.4. A Framework

for Characterization

of Extreme Floods for Dam Safety Risk Assessments, Robert E. Swain, David Bowles and Dean Ostenea, Proceedings

of the 1998 USCOLD Annual Lecture, Buffalo, New York, August 1998.5. NRC Letter EA-13-096, Subject: Monticello

Nuclear Generating

Plant, NRC Inspection

Report 05000263/2013008;

Preliminary

Yellow Finding, United States Nuclear Regulatory

Commission, Region III, 11 June 2013.6. A Preliminary

Approach to Human Reliability

Analysis for External Events with a Focus on Seismic, EPRI 1025294, EPRI, December 2012.7. Interim Staff Guidance for Performing

the Integrated

Assessment

for External Flooding, Appendix C: Evaluation

of Manual Actions, JLD-ISG-2012-05, Revision 0, U.S. NRC Japan Lessons-Learned

Project Directorate, November 30, 2012.8. Job Performance

Measure JPM-A.8-05.01-001, Manual Operation

of RCIC, Rev. 0, Task Number NL217.108

-Operation

of RCIC without Electric Power, 3 timed exercises performed

17 June 2013.9. Job Performance

Measure JPM-A.8-05.08.001, Manually Open Containment

Vent Lines, Rev. 0, Task Number FB008.007, 4 timed exercises

performed

17 June 2013.10. Hughes Associates

Record of Correspondence, RCIC Manual Operation

e-mails with Xcel Energy during June -July 2013, Hughes Associates, Baltimore, MD, 7 July 2013.11. Hughes Associates

Record of Correspondence, Hard Pipe Vent Manual Operation

e-mails with Xcel Energy during June 2013, Hughes Associates, Baltimore, MD, 7 July 2013.12. Monticello

Procedures: " 8900, OPERATION

OF RCIC WITHOUT ELECTRIC POWER, Revision 2" C.5-1 100, RPV CONTROL flowchart, Revision 11" C.5-1200, PRIMARY CONTAINMENT

CONTROL flowchart, Revision 16" C.5-3505-A, Revision 10* A.6, ACTS OF NATURE, Revision 43* A.8-05.08, Manually Open Containment

Vent Lines, Revision 1 Revision 2 Page 2

ISML16012.000-1

References

0 A.8-05.01, Manual Operation

of RCIC, Revision 2 13. The EPRI HRA Calculator

Software Users Manual, Version 4.21, EPRI, Palo Alto, CA, and Scientech, a Curtiss-Wright

Flow Control company, Tukwila, WA.14. NUREG/CR-1278, Handbook of Human Reliability

Analysis with Emphasis on Nuclear Power Plant Applications, (THERP) Swain, A.D. and Guttman, H.E., August 1983.15. NUREG-1921, EPRI/NRC-RES

Fire Human Reliability

Analysis Guidelines, Draft Report for Public Review and Comment, November 2009.16. NUREG- 1852, Demonstrating

the Feasibility

and Reliability

of Operator Manual Actions in Response to Fire, October 2007.17. NUREG/CR-1278, Handbook of Human Reliability

Analysis with Emphasis on Nuclear Power Plant Applications, (THERP) Swain, A.D. and Guttman, H.E., August 1983.18. Whaley, A.M, Kelly, D.L, Boring, R.L. and Galyean, W.J, "SPAR-H Step-by-Step

Guidance", INL/EXT-10-18533, Revision 2, Idaho National Laboratory, Risk, Reliability, and NRC Programs Department, Idaho Falls, Idaho, May 2011.Revision 2 Page 3 Revision 2 Page 3

1SML16012.000-1

Methodology

and Analysis 3.0 METHODOLOGY

AND ANALYSIS 3.1 Event Tree Analysis Event trees were developed

to calculate

the core damage frequency (CDF) associated

with External Floods. Event trees were developed

for both a best estimate case as well as sensitivity

cases. Floods were evaluated

at three particular

heights -917' but less than 930', 930' but less than 935', and greater than or equal to 935'. The first flood height range (917' to 930') was evaluated

for frequency

but was not deemed feasible to cause core damage since much of the plant's critical safety equipment

is not threatened

unless flood levels exceed the 930' elevation.

The following

sections describe the development

of the flood frequency

and conditional

probabilities

of the other events that may lead to core damage events.Additionally, it is agreed that, as stated in the NRC letter EA- 13-96 (Reference

5), the evaluation

of large early release frequency (LERF) risk is assumed to be no more significant

than CDF-based risk; therefore, no evaluation

of LERF was performed

for this analysis.3.1.1 Evaluation

of Flood Frequency MNGP teamed with industry experts to evaluate the frequency

of major floods in detail. Dr.David Bowles was the lead author for the flood frequency

analysis.

To ensure that the flood frequency

of exceedance

analysis was sound, an independent

review of the analysis was performed

as part of this analysis (Reference

1). The review resulted in some recommendations

for improvement

that were incorporated

by Dr. Bowles and his team prior to the development

of the event trees that are included in this report. This section documents

the results of that final flood frequency

analysis.The frequencies

of Mississippi

River floods at MNGP for flood heights of 917', 930' and 935'were estimated

using stream-flow

data from 1970 -2012. This estimation

is described

in"Annual Exceedance

Probability

Estimates

for Mississippi

River Stages at the MNGP based on At-Site Data for Spring and Summer Annual Peak Floods" (Reference

1).Separate flood frequency

relationships

were developed

for spring and summer annual peak floods based on the Hydrologic

Atlas of Minnesota (Reference

2) and an examination

of flow records.a) Spring annual peak floods generally

peaked in the period March to May, but if it was clear from examination

of the hydrograph

that a snow melt flood event peaked in June then that peak was used.b) Summer annual peak floods generally

peaked in June to October, but flood peaks in June associated

with snow melts were excluded since they were assigned to spring floods.Frequencies

were estimated

based on extrapolation

of flood frequency

relationships

developed from at-site flow data. The mean daily annual peak stages were obtained for spring and summer annual peak floods. The daily annual peak stages were converted

to daily annual peak flows for spring and summer floods using a combined rating curve described

in Reference

1. The Expected Moments Algorithm (PeakfqSA)

was applied using methodology

described

in the current draft of the upcoming revision to USGS Bulletin 17B (Reference

3). The EMA software provided annual exceedance

probability (AEP) estimates

down to 1 in 10,000/yr.

Annual peak discharge

was plotted on a Log scale and AEPs on a z-variate

scale (corresponding

to a Normal Revision 2 Page 4

ISML16012.000-1

Methodology

and Analysis probability

distribution)

to allow AEPs lower than 1 in 10,000/yr

to be estimated

by linear extrapolation.

The resulting

median estimates

for spring and summer floods at 917', 930' and 935' river heights were as follows: Table 3-1 Median Flood Frequency

Estimates

at MNGP Site (Ref. 1)Elevation

917' Elevation

930' Elevation

935'Spring Floods 6.3E-3/yr

<lE-9/yr <1E-9/yr Summer Floods 1.7E-3/yr

<1E-9/yr <1E-9/yr A full family of flood hazard curves is provided in the Bowles report. There is a substantial

amount of aleatory uncertainty

in the development

of these curves, resulting

in very wide confidence

bounds as can be seen in the figures and tables in the report, especially

for the flood levels of interest.

For example, the elevation

917' 95th percentile

estimate is 3.4E-2/yr

and the 5th percentile

estimate is 5.9E-7/yr

for spring floods. This is indicative

of the limited data available

in the 1970 -2012 year period. In addition, not all potential

flood influences

were seen in the 42 years of experience.

Moreover, there is additional

epistemic

uncertainty

due to simplifications

used in the modeling process, For example, regional flood impacts were not considered, nor were the potential

effect of ice blockage or changes in flood protective

features such as dikes along the river. To address these as well as other potential

flood contributors, the mean hazard for the purposes of quantification

will be represented

by the 84th percentile, which is the median plus one standard deviation

for a lognormal

form distribution.

This is a common practice to provide margin to account for the uncertainties.

As a further consideration, there is a general consensus

that the practical

limit on AEP extrapolation

is no better than 1.OE-5/yr

no matter how much information, including

information

on paleofloods, is available (see for example, "A Framework

for Characterization

of Extreme Floods for Dam Safety Risk Assessments" (Ref. 4). It is believed that all of these factors would tend to increase the estimated

frequency

of floodings.

Some of these uncertainties

could be addressed

in a more detailed analysis, such as a Monte Carlo rainfall-runoff

approach, but others, such as the potential

effect of ice blockage, would remain. In the case of this evaluation, there additional

factors will be addressed

by way of a sensitivity

study, discussed

at the end of this section.The 84th percentile

is the median plus one standard deviation, which is a common "margin value" that addresses

uncertainty

without being overly conservative.

The margin is to cover the wide statistical

uncertainty

in the distribution

plus the modeling uncertainty

that comes from some of the issues we discussed, such as not considering

ice blockage or other downstream

flow bottlenecks, only considering

site data, and not actually modeling the flows and performing

a simulation.

This results in the following

flood frequency

estimates:

The results presented

in the Bowles report support the use of the 84th %-tile as a reasonable

conservative, but not overly conservative, representation

of the mean. A manually generated approximation

of the mean (described

in Ref. 1 -the code used cannot itself generate a mean) is shown to be in the range of the 70th percentile, plus or minus about 10 percentile.

This is the result of the aleatory uncertainty.

The use of the 84th percentile

provides some additional

Revision 2 Page 5

1SM L16012.000-1

Methodology

and Analysis margin to account for epistemic

uncertainty

and give confidence

that the "true mean" is not likely to exceed this value.Treating the 84th percentile

as the mean, the process of developing

the initiating

event frequencies

is straightforward.

It is typical in external hazard PRA to create initiating

events by discretizing

the hazard curve. Because for external flooding there are a clear series of flood levels of concern, the selection

of the initiating

events is clear. For MNGP, the levels of concern are 917', 930', and 935', with the exceedance

of each level causing the same impact on plant systems until the flood exceeds the next level of concern. Therefore

the initiating

events can be defined as follows: " IE1 -level >917' and <930'" IE2 -level >930' and <935'" IE3 -level >935'Using the 84th percentile

values to represent

the mean, we get exceedance

probabilities

for each level of concern as follows: Table 3-2 84th Percentile

Exceedance

Frequencies (Used as Means) (Ref. 1)Elevation

917' Elevation

930' Elevation

935'Spring Floods. 2.0E-02/yr

7.5E-08/yr

<1E-09/yr Summer Floods 8.8E-03/yr

8.8E-06/yr

9.7E-07/yr

Total 2.9E-021yr

8.9E-061yr

9.7E-071yr

The values for spring and summer can be summed because they are each calculated

on a per-calendar-year

basis and because we are using these values to represent

the "true mean" of the distribution, albeit conservatively.

Because these values are exceedance (i.e., the frequency

that a flood exceeds a specified

level), the way to determine

the frequency

of a flood in a given range is to subtract the frequency

of exceedance

of the upper flood in the range from the frequency

of exceedance

of the lower flood in the range.One event tree was developed

to account for all floods that were greater than 930' (including

those greater than 935'). The frequency

of exceedance

for the 930' floods was used and a conditional

probability

was applied to account for the floods within the 930' to 935' range and floods greater than 935'. The frequency

shown as IE2 in Table 3-3 was used in the event tree.The conditional

probability

that the flood was indeed greater than 935' was then applied in a subsequent

branch to determine

the CDF for sequences

specific to floods greater than 935'(value of 0.109). Table 3-3 below shows the initiating

event frequencies

used for this assessment.

Revision 2 Page 6 Revision 2 Page 6

1 SML16012.000-1

Methodology

and Analysis I SMLI 6012.000-1

Methodology

and Analysis Table 3-3 Best Estimate Initiating

Event Frequencies

Initiating

Event Initiating

Event Frequency IEl 1 2.9E-02/yr

IE2 2 8.90E-06/yr

Not deemed feasible for core damage sequences.

Not evaluated

for this analysis.2This frequency

Is represented

in the event tree along with a conditional

probability

that the flood will be >935' to evaluate the correct range of flood heights.As discussed

earlier, there is the question of the practical

limit of extrapolation

of flooding data.Therefore, in addition to the initiating

event frequencies

presented

above, a sensitivity

analysis was performed

limiting the flood frequency

to no less than 1.OE-5/yr, consistent

with the consensus

reached in Ref. 4 concerning

the limit of credible extrapolation

for annual flood exceedance

probability.

Table 3-4 Sensitivity

Case Initiating

Event Frequencies

Initiating

Event Initiating

Event Frequency IE1 2.9E-02/yr

IE2 2 2.OE-05/yr

'Not deemed feasible for core damage sequences.

Not evaluated

for this analysis.2This frequency

is represented

In the event tree along with a conditional

probability

that the flood will be >935' to evaluate the correct range of flood heights.It could be argued that the limit should apply across the 930' events (i.e., that the hazard curve goes flat at 1E-5/yr) and that it is sufficient

to ignore the 935' event (because F(IE2930<=1v1<935)

=fexceed(930)

-fcxceed(935)

= 0) and simply evaluate the 930' flood at a frequency

of lE-5/yr. Since this is a sensitivity

case and not the best estimate, it was decided to assign 2E-5/yr to IE2 for purposes of providing

the sensitivity

insights and use a conditional

probability

of 0.5 to account for floods that are >935'.In the event trees (shown in Appendix A), the flood frequencies

are represented

by the headings"EXTERNAL

FLOOD >930"' and "<935.' for IE2 events. In addition, event trees used for sensitivities

have similar headings.3.1.2 Early Warning Probability

Although it was considered

qualitatively, there was no basis determined

for giving credit to the potential

for early warning of a flood >930'. The event tree model shows a failure probability

of 1.0 for this node.3.1.3 Protection

of the Reactor Building In the event of a major flood, such as those evaluated

in this analysis, MNGP plans to build a bin wall barrier that will protect the site from the high flood waters. If the bin wall levee is successful, the safety equipment

needed to prevent core damage will be protected, providing defense in depth for each required critical safety function.

Simple flood protection

measures may be taken to protect the reactor building from floodwater, even if the bin wall levee fails.These measures to protect the reactor building do not need to be in place until the flood height approaches

the 935' elevation.

A conservative

value of 0.11 is assigned, consistent

with the ES-13-096 NRC letter (Reference

5), to the failure probability

of protecting

the reactor building.Revision 2 Page 7 Revision 2 Page 7

1SML16012.000-1

Methodology

and Analysis 3.1.4 Manual Local Operation

of RCIC and the Hard Pipe Vent MNGP requested

Hughes Associates

to conduct a detailed human reliability

analysis (HRA) to estimate human error probabilities

for operator manual actions to prevent core damage through the use of RCIC as a high pressure injection

source and the Hard Pipe Vent (HPV) to remove decay heat from containment.

This detailed HRA was based upon thermal/hydraulics

analyses, battery depletion

calculations, several Job Performance

Measure (JPM) exercises

for the specific procedure

A8.05.01 and A8.05.01 actions (References

8 and 9) considering

flood and Station Blackout (SBO) conditions, and discussions

with Operations

and PRA staff (References

10 and 11). This section documents

the initial conditions

assumed, the analytical

process, and the results of the detailed HRA. A comparison

between the detailed analysis results and those obtained using SPAR-H is also provided as a sensitivity

evaluation.

3.1.4.1 Initial Conditions

for the Operator Manual Actions Operations

staff at MNGP provided the following

information

on the conditions

that would be evolving leading up to the need for the postulated

operator manual actions evaluated

in this HRA.The A.6 Procedure, "Acts of Nature" (Reference

12) that addresses

External Flooding directs de-energizing

the 115 KV, 230 KV and 345 KV substations

for flood levels in excess of the 930'elevation.

In the case where the flood level is above 930' this would lead to a loss of offsite power and reliance on the EDGs. Since the normal long term fuel oil storage (Tank T-44) for the EDG's is not evaluated

to survive flood levels above 932' elevation, and alternate

fuel oil makeup methods are not pre-prescribed

to support the EDG's, long term EDG operation

is not easily defensible

utilizing

existing procedures.

Additionally, there are several penetrations

in the Plant Administration

Building that would make positive flood proofing of the building difficult, leaving three of the four station batteries

vulnerable

to flooding.The flooding engineer provides daily updates to the station on high river water levels including potentials

to rise above any trigger points from the A.6 procedure.

At this point, heightened

awareness

of the potential

for flooding is implemented.

When river level exceeds 921 feet an evaluation

of EALs would be performed.

If visible damage has occurred due to flood water rising greater than 921 feet, then an Alert per EAL HA1.6 would be declared.Prior to the river reaching these levels, operators

would be walking down the procedures

for alternate

methods to vent primary containment

and operate RCIC remotely.

This would involve staging of equipment

in the torus area to open the Hard Pipe Vent and verification

that equipment

is properly staged to operate RCIC remotely.As water level reached the 930' elevations, Operations

would prepare for isolation

of off-site power and loading essential

loads onto the emergency

diesel generators

as needed to conserve fuel. Only a single EDG is required for shutdown cooling and inventory

makeup. Operators would be in the EDG rooms, intake and other critical areas ensuring no water intrusion

and would be pumping water out of the room as needed. Also the battery rooms in the PAB would be of concern due to the high flood levels. At this point operators

would be briefed to be ready to operate RCIC without electrical

power as necessary.

Revision 2 Page 8

1 SML16012.000-1

Methodology

and Analysis The portable diesel fire pumps would also be staged at higher locations

with hoses staged through higher elevations

of the buildings

to support alternate

RPV makeup.Operators

would be dispatched

with I&C technicians

to the 962' elevation

of the reactor building to install the temporary

level indication

per procedure

A.8-05.01.

This would allow for alternate level indication

to be available

in the event that the batteries

are lost.In the response scenario postulated

for the performance

of the operator manual actions evaluated in this HRA, EDGs and batteries

are not available.

Shutdown cooling, HPCI, and RCIC are not available

from normal electrical

means. RCIC is available

for manual operation.

Operators

would have temporary

level indication

set up in the reactor building.

Pressure indication

is available

in the direct area of the level transmitters.

The building is dark and most likely there is water in the basement of the reactor building.

Additional

portable lights are available

to assist with lighting and boots staged for higher water. The operators

would utilize procedure

A.8-05.01

to un-latch the governor from the remote servo linkage and throttle steam flow to RCIC to start the turbine rolling while coordinating

with operators

monitoring

water level and reactor pressure.

Upon reaching the high end of the level band the operators

would throttle closed the steam admission

valve and await direction

to re-start RCIC. Local operation of RCIC is demonstrated

each refueling

outage during the over speed test. Operation

of a coupled turbine run is less complex because the turbine is easier to control with a load.3.1.4.2 Detailed HRA The human error probabilities (HEPs) for manual local operation

of RCIC and the Hard Pipe Vent during an extreme flooding and SBO event have been developed

in detail utilizing

the EPRI HRA Calculator (Reference

13). Event RCICSBOFLOOD (Fail to manually operate RCIC during SBO and extreme flooding conditions), and event HPVSBOFLOOD (Fail to operate the HPV using N2 bottles to provide containment

heat removal during SBO/Flood)

have values of 9.3E-02 and 1.3 E-02 respectively, for a combined value of 1.06E-01.The HRA Calculator

reports for these events, which provide a detailed basis for these HEP estimates, are presented

in Appendix A. Section A. 1 documents

RCICSBOFLOOD

and Section A.2 documents

HPVSBOFLOOD.

The cognitive

portion of these HEPs was developed

using the Cause Based Decision Tree Method (CBDTM) (Reference

13) and the execution

portion utilized the Technique

for Human Error Rate Prediction (THERP) (Reference

14). These methods are commonly used in internal events PRA, have been cited in the EPRI/NRC-RES

Fire HRA Guidelines, NUREG-1921 (Reference

15) and applied in many fire PRAs, and are also cited in the following

reference:

• A Preliminary

Approach to Human Reliability

Analysis for External Events with a Focus on Seismic, EPRI 1025294, EPRI, December 2012.NUREG-1921

and THERP are also listed as references

to the following

document:* Interim Staff Guidance for Performing

the Integrated

Assessment

for External Flooding, Appendix C: Evaluation

of Manual Actions, JLD-ISG-2012-05, Revision 0, U.S. NRC Japan Lessons-Learned

Project Directorate, November 30, 2012.Revision 2 Page 9 Revision 2 Page 9

ISML16012.000-1

Methodology

and Analysis Appendix C of the ISG on External Flooding concentrates

primarily

on demonstrating

the feasibility

and reliability

of the manual actions consistent

with NUREG-1852 (Reference

16),"Demonstrating

the Feasibility

and Reliability

of Operator Manual Actions in Response to Fire." One of the key variables

in determining

feasibility

of operator manual actions is timing. As stated in the ISG, "For an action to be feasible, the time available

must be greater than the time required when using bounding values that account for estimation

uncertainty

and human performance

variability." In order to assess this feasibility, the following

process is recommended

in section C.3.2.4 Calculate

Time Margin: "The licensee should calculate

the time margin available

for the action using the values for time available

and time required that have been developed

for the analysis." The time margin formula provided is:[(Tsw-Tdelay)--(Tcog+Texe))

Time Margin = (Tcog.Texe)

X 100%The terms of the equation are defined as follows: Tdelay = time delay, or the duration of time it takes for the cue to become available

that indicates that the action will be necessary (assumes that action will not be taken in the absence of a cue);Tsw = the time window within which the action must be performed

to achieve its objective;

Tcog = cognition

time, consisting

of detection, diagnosis, and decision-making;

and Texe = execution

time including

travel, collection

of tools, donning of PPE, and manipulation

of relevant equipment.

The HEP calculations

performed

for the RCIC and HPV manual actions involved the estimation

of the time parameters

cited in the Time Margin formula. These times are based upon thermal/hydraulics

analyses, battery depletion

calculations, several Job Performance

Measure (JPM) exercises

for the specific proceduralized

actions and considering

flood and SBO conditions, and discussions

with Operations

and PRA staff.Using this information, the time margin for these two events is calculated

as: Table 3-5 Time Margin for HFEs Times (in minutes) RCIC HPV Tsw 478.2 900 Tdelay 345 330 Tcog 10 10 Texe 80 45 Time Margin 48% 936%The HEP timing estimates

therefore

meet the criteria that "using the calculation

under C.3.2.4, the margin must be a positive percent value for an action to be deemed feasible." Revision 2 Page 10

1SML16012.000-1

Methodology

and Analysis The External Flooding ISG also recommends

that estimates

of time available

and time required should account for sources of uncertainty

and human performance

variability.

The timing estimates

shown above are already believed to be conservative.

For example, the Tdelay of 345 min for the RCIC event is based on 5.75 hours8.680556e-4 days <br />0.0208 hours <br />1.240079e-4 weeks <br />2.85375e-5 months <br /> until RCIC battery depletion.

This can be considered

conservative

since, in reality, it is likely that an action would be taken before waiting for battery depletion.

For the Texe values, the highest observed time in the JPM trials was used for the RCIC case and further time was added for transit time for actions in various locations.

For the HPV case, the Texe value was also based on JPM trial data and the results above show that uncertainties

are covered by a significant

time margin.In addition to feasibility, the reliability

of the actions was evaluated

through the detailed HRA Calculator

analysis used to quantify HEPs.Section C4 of the ISG says that for an action to be deemed reliable, "sufficient

margin should exist between the time available

for the action and the time required to complete it. This margin should account for: (1) limitations

of the analysis (e.g., failure to identify factors that may delay or complicate

performance

of the manual action); and (2) the potential

for workload, time pressure and stress conditions

to create a non-negligible

likelihood

for errors in task completion...

A simplified

alternative

criterion

for determining

if the margin is adequate to deem an action as reliable is to establish

that the margin is not less than 100%. Such a margin may be justified

when recovery from an error in performing

the action could be accomplished

by restarting

the task from the beginning." As shown above, the time margin for the HPV manual action is greater than 100% and the time margin for the RCIC manual action is estimated

at around 50%. The evaluation

of PRA and Operations

staff in performing

the JPMs for these actions was that there would be 7 hours8.101852e-5 days <br />0.00194 hours <br />1.157407e-5 weeks <br />2.6635e-6 months <br /> or more to perform the procedures, allowing several opportunities

to troubleshoot

and/or re-perform

steps if necessary.

In addition, based on the HEP quantification, the combined probability

for the RCIC and HPV actions is estimated

to have a success rate of 89%. A sensitivity

study was performed

using SPAR-H estimates

to evaluate the effect of reliability

uncertainty.

Regarding

the evaluation

of factors such as workload and stress that could complicate

task performance, performance

Shaping Factors (PSFs) were considered

for feasibility

and addressed in the assessment

of reliability

of the operator manual actions.The following

table discusses

each of the PSF categories

cited in Appendix C of the ISG, the issues related to the RCIC and HPV manual actions and how they were addressed

in the qualitative

and quantitative

analysis of these human failure events.Revision 2 Page 11 Revision 2 Page 11

1SML16012.000-1

Methodology

and Analysis Table 3-6 Performance

Shaping Factors for Human Failure Events Performance

Shaping Factors Specific Considerations

for RCIC and HPV Events under SBO and (PSFs) Flooding Conditions

Cues Cues not only were provided by the Emergency

Operating

Procedure flowcharts

for RPV Level and Containment

Pressure and supporting

procedure, but would be expected to be provided by the Emergency Response Organization

staff and STA. It is expected that daily meetings would be held to assess the plant situation

considering

the long term effects of flooding and SBO and plans would be made to implement

the RCIC and HPV actions. The decision to perform these actions would therefore

be made by ERO and STA and the Shift Supervisor

would give the direction

to operations

staff.Indications

Due to the Station Blackout, impacts to the normal set of indications

were expected and these effects were implemented

in the CBDTM module of the HRA Calculator

consistent

with the methods recommended

in NUREG-1921, Appendix B as well as in the Execution

PSFs and Stress module. In addition, the "Degree of Clarity of Cues & Indications" was degraded from "Very Good" to "Poor".Complexity

of the Required Action The response is considered

to be Complex due to the flooding and SBO impacts to lighting and accessibility.

The procedure

steps of the actions that are required and that were evaluated

in the timed Job Performance

Measures (JPMs) specifically

performed

for these tasks are listed in the Execution

Unrecovered

module of HRA Calculator.

Special Equipment

Flashlights, headlamps

and boots were considered

necessary

by Training when the JPMs were performed

for these tasks, and are reflected

in the timing estimates

for Tm and in the Execution

PSFs Special Requirements

by indicating

that Tools, Parts and Clothing were required and available.

Human-System

Interfaces

The interfaces

with the system will be similar, but with impacts due to the SBO and flooding in terms of indications

and lighting.

For the RCIC task, a hand-held

reactor level monitor is installed

and used by I&C technicians

to monitor the parameter.

These steps of the procedure

were specifically

included in the Execution

portion of the RCIC action quantification.

The HPV task involves the use of air cylinders

and these steps were also included in the Execution

portion of the quantification.

Revision 2 Page 12 Revision 2 Page 12

ISMLI16012.000-1

Methodology

and Analysis Table 3-6 Performance

Shaping Factors for Human Failure Events Performance

Shaping Factors Specific Considerations

for RCIC and HPV Events under SBO and (PSFs) Flooding Conditions

Procedures

Multiple procedures

provide for operation

of the RCIC System without the availability

of AC or DC power. They address the lighting and ventilation

limitations

that accompany

a SBO, and provide for alternate

means of monitoring

reactor water level/pressure, controlling

turbine speed, assuring adequate water source is available

and accommodating

the condensate

from the turbine condenser.

• Procedure

8900 (Operation

of RCIC without Electric Power)* Procedure

C.4-L; Part F (Response

to Security Threats; Initiate Injection to the RPV with RCIC)* Procedure

A.8-05.01 (Manual Operation

of RCIC)* Procedure

B.08.09-05.H.4 (Condensate

Storage System -Filling Condensate

Storage Tanks from Alternate

Source)-Procedure

A.8-05.05 (Makeup to CST)Any of the following

procedures

provide for operation

of the HPV without the need for normal support systems including

electric power and pneumatic

supplies.

All necessary

equipment

to perform this function is specifically

manufactured

and pre-staged

to allow opening the HPV valves.-Procedure

B.04.01-05.H.2 (Primary Containment

System Operation

-Alternate

N2 Supply for Operating

AO-4539 and AO-4540)-Procedure

C.5-3505;

Part A (Venting Primary Containment;

Vent Through the Hard Pipe Vent)-Procedure

A.8-05.08 (Manually

Open Containment

Vent Lines)The relevant procedures

were reviewed, cues and operator action steps were itemized in the quantification

and were evaluated

using multiple iterations

of the timed JPMs.Training and Experience

The RCIC and HPV capabilities

are included in various aspects of periodic operations

training.

Training materials

and mockup training devices related to these activities

include: " JPM -B.02.03-005 (Reset RCIC Overspeed

Trip)" Training mockup of the RCIC Turbine Trip Throttle Valve (MO-2080)" Lesson Plan MT-ILT-EOP-002L (RPV Control)" Lesson Plan MT-NLO-12C-002L (Emergency

Operating

Procedures

Overview)* Lesson Plan MT-NLO-EOP-001

L (EOPs for NLOs (Turbine Building))

• Lesson Plan MT-OPS-FB-004L (Level 4 -Extensive

Damage Mitigation

Guidelines)

-Lesson Plan M-8107L-003 (RCIC)Additionally, control of RCIC, using the RCIC MO-2080 Turbine Trip Throttle Valve is actually performed

during the startup from each refueling outage, in the performance

of procedure

1056 (RCICI Turbine Overspeed Trip Test).Operator training, procedure

adequacy, and equipment

readiness regarding

use of these mitigation

measures has been reviewed by the NRC as part of the B.5.b and Fukushima

Flex response inspections

and been determined

to be acceptable.

• ML1 1235A897 (NRC Fire/B.5.b

Inspection

Report; 8/23/11)* ML1 11320400 (NRC Temporary

Instruction

2515/183;

5/13/11).Perceived

Workload, Pressure Under the quantification

Execution

PSFs, Workload has been assessed and Stress as High and PSFs of Negative, so the overall stress is assessed as High.Revision 2 Page 13 Revision 2 Page 13

ISMLI16012.000-1

Methodology

and Analysis Table 3-6 Performance

Shaping Factors for Human Failure Events Performance

Shaping Factors Specific Considerations

for RCIC and HPV Events under SBO and (PSFs) Flooding Conditions

Environmental

Factors The environment

would be consistent

with SBO (hot, dark, damp) and some Reactor Building flooding requiring

boots. These were the conditions

evaluated

during the timed JPMs and are addressed

in the quantification

under Execution

PSFs for Lighting, Heat/Humidity

and Atmosphere.

Special Fitness Issues No special fitness issues were identified

although the performance

of multiple trials of the JPMs is considered

to address the variability

in personnel

fitness.Staffing Operations

staffing to perform the procedures

would be optimal (several operators

assigned as desired to each procedure).

Discussions

were held to evaluate whether there would be dependencies

in staffing between the RCIC and HPV actions and it was considered

that due to the different timeframes, that the actions and staffing would be separate.Communications

Under SBO conditions

the use of radio and walkie talkies would be expected to allow communications

to be maintained

between the Main Control Room and the I&C Technicians

and the staff performing

the key actions.Accessibility

The Equipment

Accessibility

is evaluated

as "With Difficulty" due to reactor building lighting and flooding issues. The quantification

Execution PSFs indicates

this and these issues were addressed

during the JPM timing sessions.A sensitivity

analysis was also performed

by developing

human error probabilities (HEPs) for manual local operation

of RCIC and the Hard Pipe Vent during an extreme flooding and SBO event utilizing

the SPAR-H module of the EPRI HRA Calculator

and recommended

practices from the Idaho National Laboratory

step-by-step

SPAR-H guidance (Reference

17). Using SPAR-H, event RCICSBOFLOOD (Fail to manually operate RCIC during SBO and extreme flooding conditions), and event HPVSBO FLOOD (Fail to operate the HPV using N2 bottles to provide containment

heat removal during SBO/Flood)

have values of 1.4E-01 and 5.5E-02 respectively, for a combined value of 1.95E-01.The HRA calculator

reports associated

with these HEPs can be found in sections A.3 and A.4 of Appendix A.Revision 2 Page 14 Revision 2 Page 14

ISML16012.000-1

Conclusions

4.0 CONCLUSIONS

The results of the analysis are shown in Table 4-1. This table includes the results of both the best estimate quantification

and the sensitivities

that were performed

in support of this analysis.The ACDF represents

the difference

between the best-estimate

CDF and the baseline CDF. The baseline CDF is the CDF without the performance

deficiency.

The best-estimate

CDF is the result of the event tree calculations

shown in Appendix A. The exposure time represents

the period of time the plant was exposed to the performance

deficiency.

This time period was from February 29, 2012 to February, 15, 2013 resulting

in an exposure time of 352 days or 0.964 years. The failure to build construct

a levee is assumed to be 0.11 (consistent

with the probability

assumed by the NRC). Therefore, the baseline CDF is calculated

by multiplying

the best-estimate

CDF by 0.11. ACDF is equal to the best-estimate

minus the baseline, thus:= best-estimate

-0.11 x best-estimate

= (1-0.11) x best-estimate

= 0.89 x best-estimate.

ACDP = exposure x ACDF = 0.964 x 0.89 x best-estimate.

Table 4-1 Results of Event Tree Quantification

Sensitivity

1: Sensitivity

2: NRC Case Nominal, Bounding Flood SPAR-H HRA Frequency

Probabilities

CD Seq 1 8.41 E-07 1.06E-06 1.55E-06 CD Seq 2 9.15E-08 9.43E-07 1.68E-07 CD Seq 3 1.07E-07 1.10E-06 1.07E-07 CDF 4.20E-05 1.04E-06 3.10E-06 1.83E-06 ACDF 3.60E-05 8.92E-07 2.66E-06 1.57E-06 Significance

Yellow Green White White The results of this analysis show that by a best-estimate

analysis, the significance

of the flooding event is Green. Two sensitivity

studies performed

to evaluate the effects of sources of uncertainty

show that the significance

of the flooding could be characterized

as low to moderate safety or security significance

or 'White' using bounding assumptions.

Revision 2 Page 15 Revision 2 Page 15

I SML16012.000-1

Appendices

APPENDICES

TABLE OF CONTENTS A. APPENDIX A -HRA CALCULATOR

REPORTS ........................................

A-1 A.1. RCICSBOFLOOD, Fail to manually operate RCIC during SBO and extrem e flooding conditions

...............................................................

A-1 A.2. HPVSBOFLOOD, Fail to operate the HPV using N2 bottles to provide containment

heat removal during SBO/Flood

.......................................

A-19 A.3. RCICSBOFLOOD, Fail to manually operate RCIC during SBO and extreme flooding conditions (SPAR-H) .................................................

A-31 A.4. HPVSBOFLOOD, Fail to operate the HPV using N2 bottles to provide containment

heat removal during SBO/Flood (SPAR-H) ......................

A-36 B. APPENDIX B -EVENT TREES ...................................................................

B-1 Revision 2 Page 16 Revision 2 Page 16

1SML16012.000-1

Appendix A -HRA CALCULATOR

REPORTS A. APPENDIX A -HRA CALCULATOR

REPORTS The following

sections document the HRA Calculator

reports that support this analysis.A.1. RCIC_SBOFLOOD, Fail to manually operate RCIC during SBO and extreme flooding conditions

Basic Event Summary.%Plant Data File: ':FiledSize'

File Dated. IR1ecord.

Date Monticello

Ext 913408 07/02/13 07/02/13 Flooding SDP HRAJune 2013.HRA':Nam ;-Date Analyst Erin P. Collins, Hughes 07/02/2013

Associates

Reviewer John Spaargaren

& Pierre 07/02/2013

Macheret, Hug hes Associates

Table 41: RCIC_SBOFLOOD

SUMMARY______________

~HEP,-Sumay

__Pcog Pexe Total HEP Error Factor Method CBDTM THERP CBDTM + THERP Without Recovery 2.9e-02 5.2e-01 With Recovery 9.2e-04 9.2e-02 9.3e-02 5 Initial Cue: RPV Water Level Below 9 in.Recovery Cue: Before RPV level drops to -149 inches Cue Comments: The cue for action is that the TSC and the Emergency

Director have determined

that RCIC operation

is needed. The Control Room Supervisor (CRS) directs operator to initiate RCIC and inject into the RPV using procedure

A.8-05.01, Manual Operation

of RCIC, Part A, Placing RCIC in Service.Due to the SBO, it is assumed that there will be multiple impacts to indications, so the degree of clarity has been set at "Poor".Deqree of Clarity of Cues & Indications:

Poor Procedures:

Cognitive:

C.5-1 100 (RPV CONTROL flowchart (Monticello))

Revision:

11 Execution:

A.8-05.01 (Manual Operation

of RCIC) Revision:

2 Other: A.6 (ACTS OF NATURE (Monticello))

Revision:

43 Other: 8900 (OPERATION

OF RCIC WITHOUT ELECTRIC POWER (Monticello))

Revision:

2 Revision 2 Page A-I Revision 2 Page A-1

1SML16012.000-1

Appendix A -HRA CALCULATOR

REPORTS Cognitive

Procedure:

Step: LEVEL Instruction:

Restore and maintain RPV water level 9 to 48 in. using Preferred

Injection

Systems Procedure

and Training Notes: Three JPM trials were performed

emulating

the specific external flooding conditions

of this scenario on 18 June 2013. Observations

were factored into this analysis.Procedure

A.8-05.01

-2.0 ENTRY CONDITIONS

This strategy is entered when one or more of the following

conditions

are met: o As directed from A.8-01.01 (Extensive

Damage Mitigation

Strategy Overview)o As directed from A.8-03.01 (Initial Response Actions)o As directed from 5790-110-01 (Monticello

Emergency

Management

Guideline)

-presume this is the relevant case since ERF is staffed and will make the call on implementing

the procedure Training: Classroom, Frequency:

0.5 per year Simulator, Frequency:

0.5 per year JPM Procedure:

JPM-A.8-05-01-001 (Manual Operation

of RCIC) Revision:

0 Identification

and Definition:

1. Letter to Region III SRA write-up, 8 April 2013 Section G -HEP Associated

with Protecting

Plant Buildings

from 930' Elevation

Flood For the case where the site is not protected

by a ring levee, but individual

buildings

/ equipment

are protected

by flood barriers as called out in the A.6 (Acts of Nature) procedure, several redundant

options remain available

for protecting

critical safety functions

related to injecting

water to the reactor, maintaining

desired reactor pressure, and removing decay heat from containment.

The A.6 Procedure

[Acts of Nature that addresses

External Flooding]

directs de-energizing

the 115 KV, 230 KV and 345 KV substations

for flood levels in excess of the 930' elevation.

In the case where the flood level is above 930' this would lead to a loss of offsite power and reliance on the EDGs. Since the normal long term fuel oil storage (Tank T-44) for the EDG's is not evaluated

to survive flood levels above 932' elevation, and alternate

fuel oil makeup methods are not pre-prescribed

to support the EDG's, long term EDG operation

is not easily defensible.

Additionally, there are several penetrations

in the Plant Administration

Building that would make positive flood proofing of the building difficult, leaving three of the four station batteries

vulnerable

to flooding.2. PRA-MT-SY-RCIC, Reactor Core Isolation

Cooling System Notebook, Revision 3.0, December 2012 Table 3 -IE_LOOP (Loss Of Offsite Power Initiating

Event) Impact on RCIC System: A loss-of-offsite

power does not affect RCIC, provided AC power remains available

to the Division 1 battery chargers.

A loss of Feedwater

would result, and RCIC operation

would be automatically

actuated when Low-Low Level in the RPV is reached.Key Assumptions:

It is assumed that there will be sufficient

water and fuel supply for the equipment

needed in this scenario despite the flooding conditions

and considering

the long term nature of the flood, which may take as many as 12 days to recede (from the Monticello

Design Basis documentation).

This means that CST level is assumed to be maintained

via a step in this HEP and is not quantified

separately.

Another key assumption

is that because the staffing needed for this event is separate from that used for the Hard Pipe Vent human failure event, and the timeframe

for HPV is much longer, no dependency

between these events was evaluated (in other words, the timing and staffing were considered

as totally separate events).Revision 2 Page A-2

1SMIL160112.000-11

Appendix A -HRA CALCULATOR

REPORTS ISM LI 6012.000-1

Appendix A -HRA CALCULATOR

REPORTS JPM-A.8-05.01-001 (Manual Operation

of RCIC) Rev. 0 INITIAL CONDITIONS:

o Extreme flooding has led to a Station Blackout that has existed at Monticello

for the last 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br />.o Div. 1 250 VDC battery system has been depleted and is not available.

o The plant was in Shutdown Cooling until the station blackout and has since been slowly repressurizing

due to heating up.o Current RPV pressure is 75 psig-and slowly rising.o Current RPV water level is -40" and very slowly lowering.o The TSC and the Emergency

Director have determined

that RCIC operation

is needed.o HPCI is inoperable.

o RCIC suction is from the CSTs.o RCIC operation

is required to maintain RPV level above TAF.o Approximately

2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> ago Radiation

Protection

reported -2" of water on the Rx Bldg basement floor.o A second operator will be performing

Part B, Set Up and Monitor of Rx Vessel with Fluke 707.o A third operator will be maintaining

CST level using A.8-05.05, Makeup to the CST, and verifying valve status in the steam chase.INITIATING

CUES (IF APPLICABLE):

o The CRS directs you to initiate RCIC and inject into the RPV using A.8-05.01, Manual Operation of RCIC, Part A, Placing RCIC in Service.o Inform the CRS when RCIC is in service with discharge

pressure at least 76 psig greater than reactor pressure..

RCIC local manual operation

Job Performance

Measure entry condition

assumptions, Documented

in and excerpted

from Hughes Associates

Record of Correspondence, RCIC Manual Operation

e-mails with Xcel Energy during June -July 2013, Hughes Associates, Baltimore, MD, 7 July 2013: Conditions

anticipated

following

a SBO resulting

from an external flooding event: o ERO has been manned for the past several days, with these procedures

predicted

and planned to be implemented

ahead of time o Plant is in cold shutdown condition (mode 4)o I&C would perform the reactor level monitoring

portion of the RCIC procedure o Operations

staffing to perform the procedures

would be optimal (several operators

assigned as desired to each procedure)

o Environment

would be consistent

with SBO (hot, dark, damp)o There would be 7 hours8.101852e-5 days <br />0.00194 hours <br />1.157407e-5 weeks <br />2.6635e-6 months <br /> to perform the procedures, allowing several opportunities

to troubleshoot

and/or re-perform

steps if necessary o The ERO would place maximum priority on maximizing

chances of successful

performance

of these procedures

Operator Interview

Insights: Documented

in and excerpted

from Hughes Associates

Record of Correspondence, RCIC Manual Operation

e-mails with Xcel Energy during June -July 2013, Hughes Associates, Baltimore, MD, 7 July 2013: From Xcel Operations:

The series of events would progress during a flooding event such that the need for the alternate

instrumentation

would be known before the flood completely

resulted in a station blackout with loss of DC. The alternate

instrumentation (Fluke) would be connected

to the selected locations.

If this instrumentation

did not agree with the actual permanent

instrumentation (i.e. prior to failure), assistance

would be obtained to figure out the discrepancy.

It is a relatively

simple solution to get the temporary

instrumentation

to work by either pulling a fuse or lifting a lead. This action would be required Revision 2 Page A-3

I SMLI16012,000-1

Appendix A -HRA CALCULATOR

REPORTS for the control room, cable spreading

room and EFT locations (again not proceduralized).

The other option would be to use the transmitter

in the reactor building to get the readings which does not require the lifted lead or fuse pulled.The other issue that is of concern is the need to density compensate

the fluke readings to get an actual level. The indicated

level can be drastically

different

from the actual level depending

on the calibration

conditions

of the instrument (hot or cold calibration

conditions)

and the actual pressure/temperature

at the time of the reading. None of this information

is contained

in the A.8 procedures.

There are density compensation

tables in the B.1.1 operations

manual figures section six and they are also posted in the control room. It would take additional

action for the on-shift team/technical

staff to put this all together to determine

what actual level was from the readings that came off the fluke.

FD "nniramanta

el

=~ :!.n cluded. Total Available

Reuired for PNotes________.......___....

..__ ... ... __ .... .. .._____ Execuition

_________________i

Reactor operators

Yes 2 1 Plant operators

Yes 2 0 Mechanics

Yes 2 0 Electricians

Yes 2 0 I&C Technicians

Yes 2 0 Health Physics Technicians

Yes 2 0 Chemistry

Technicians

Yes 1 0 Execution

Performance

Shapina Factors: Environment:

Lighting Portable Heat/Humidity

Hot / Humid Radiation

Background

Atmosphere

Steam (although

steam will not be present, this PSF was used to indicate an off-nominal

condition, such as would be present for flood and SBO)Special Requirements:

Tools Required Adequate Available Parts Required Adequate Clothing Required Adequate Complexity

of Response:

Cognitive

Complex Execution

Complex Equipment

Accessibility

Main Control Room Accessible (Cognitive):

Equipment

Accessibility

Reactor Building With Difficulty (Execution):

Stress: High Plant Response As Expected:

Yes Workload:

High I Performance

Shaping Factors: Negative Revision 2 Page A-4

ISML16012.000-1

Appendix A -HRA CALCULATOR

REPORTS Performance

Shaping Factor Notes: The response is considered

to be Complex due to the flooding and SBO impacts to lighting and accessibility.

Flashlights, headlamps

and boots were considered

necessary

by Training when the JPMs were performed

for these tasks.The Equipment

Accessibility

is evaluated

as With Difficulty

due to Rx building lighting and flooding issues.Despite preparations

and training, the flooding scenario is considered

to be a high stress situation.

Key Assumptions (see that section) regarding

the conditions

provided to Training for performing

the JPM for this task said that the "Environment

would be consistent

with SBO (hot, dark, damp)". The Training insights from the JPM performance (see Operator Interview

Insights)

stated that the operators recommended

to "Stage additional

flashlights

and headlamps

in RCIC room", so it is clear that portable lighting is used.Revision 2 Page A-5 Revision 2 Page A-5

1 SML16012.000-1

Appendix A -HRA CALCULATOR

REPORTS Timing: T S 7.97 Hours T dly5.75 Hours T / 10.00 Minutes T M 80.00 Minutes Irreversible

Cue DamageState

t=o Timingi Analysis: TO = Station Blackout Tsw = Time from Station Blackout to the time by which RCIC must be restored.Per Monticello

MAAP Calculations, case "SBOCase3-R1", 27 June 2013: Time to TAF = 7.17 hrs Time to -149" = 7.2 hrs Time to 1800 F = 7.97 hrs Damage is assumed to occur if the temperature

exceeds 1800 F or 7.97 hrs, so this was used for Tsw as the time by which RCIC restoration

is required.Tdelay = PRA battery calc (PRA-CALC-1

1-002) indicates

that there are 5.75 hrs until RCIC battery depletion.

Also, the RCIC Water Flow (column BC) of the d41 tabs in the "SBOCase3-R1" MAAP analysis spreadsheet

shows that RCIC injection

stops at approximately

the same time (5.74 hrs), so the MAAP runs agree with the calc. This Tdelay can be considered

somewhat conservative, since in reality, it is likely that an action would be taken before waiting for battery depletion.

T1/2 = The cue for action is that the TSC and the Emergency

Response Director have determined

that RCIC operation

is needed. Daily planning meetings will have been held to discuss actions to be taken as soon as the diesels are lost, so the 10 minutes is simply an estimate of the meeting time between TSC and ERF personnel

to make the actual decision to manually operate RCIC. The Control Room Supervisor (CRS) directs operator to initiate RCIC and inject into the RPV using procedure

A.8-05.01, Manual Operation

of RCIC, Part A, Placing RCIC in Service.Tm = Results of RCIC local manual operation

Job Performance

Measure performed

18 June 2013. The procedure

was performed

three times, taking 49 minutes, 37 minutes and 50 minutes to complete for an average time of 45 minutes. 50 minutes was used as the conservative

value for JPM performance.

The JPM did not include the performance

of Part B for installation

and use of the Fluke level monitoring

device; this was estimated

to require 30 minutes, so the total time for Tm was estimated

as 50 min + 30 min = 80 min.Time available

for cognition

and recovery:

53.20 Minutes Time available

for recovery:

43.20 Minutes SPAR-H Available

time (cognitive):

53.20 Minutes Revision 2 Page A-6 Revision 2 Page A-6

1SML16012.000-1

Appendix A -HRA CALCULATOR

REPORTS I SMLI 6012.000-1

Appendix A -HRA CALCULATOR

REPORTS SPAR-H Available

time (execution)

ratio: 1.54 Minimum level of dependence

for recovery:

LD Revision 2 Page A-7 Revision 2 Page A-7

1SML16012.000-1

Appendix A -HRA CALCULATOR

REPORTS I SMII 6012.000-1

Appendix A -HRA CALCULATOR

REPORTS Cognitive

Unrecovered

RCICSBOFLOOD

Table 42: RCICSBOFLOOD

COGNITIVE

UNRECOVERED

Pc Failure Mechanism;.

Birainch 'HEP Pca: Availability

of Information

d 1.5e-03 PCb: Failure of Attention

m 1.5e-02 Pcc: Misread/miscommunicate

data e 3.0e-03 Pcd: Information

misleading

b 3.0e-03 Pce: Skip a step in procedure

9 6.0e-03 Pcf: Misinterpret

instruction

a neg.Pcg: Misinterpret

decision logic k neg.PCh: Deliberate

violation

a neg.Sum of Pca through PCh = Initial Pc = 2.9e-02 Notes: Normal RPV water level indication

is not available

and must be monitored

with a hand held device installed

by I&C. This is clearly proceduralized

in Part B of A.8-05.01.

Presumed that SBO causes issues with normal alarms and indications

so pc-a through -d were adjusted consistent

with insights from EPRI 1025294, A Preliminary

Approach to Human Reliability

Analysis for External Events with a Focus on Seismic, October 2012.Revision 2 Page A-8 Revision 2 Page A-8

I SM L16012.000-11

Appendix A -HRA CALCULATOR

REPORTS ISM LI 6012.000-1

Appendix A -NRA CALCULATOR

REPORTS pca: Avalabilty

of infonnation

u ,cation Aal in CR Inicalion

WaIingAlternate

'l'kaining

on CR Accurate W Procedure

Infelators

Yes (a) neg.(b) neg.(c) neg.3.-e-03 -(d) 1.5e-03 11.0e+00 1.0e-01 (e) 5.0e-02 1.0e+00 (f) 5.0e-01 1.0e400 (g) I.0e+O0 1LOO1M MCR indications

may not be accurate due to the Station Blackout, however, either procedural

or informal crew information

on alternate

indications

and training should provide operator input to decision-making.

pcb: Falum of attention Low vs. M Check vs. Monitor Front vs. Back Alaued vmNot Workload Pan el Alnned ek IO O(a) neg..e*i Back I 0(b) .5e-04 3.0e-0 (c) 3.0e-03 1.8e+.00 Front 15.0e-02 (d) I.5e-04 io.00M oI (e) 3.0e-03 3e-03 Back 15.0e-02 (f) 3.0e-04 1. Cb ie 3.0e-03 (g) 6.Oe-03 2. Cb ice Front 15.0e-02 ((h) neg.Check O.e00 e4 (i)neg.o.oeo Back 5.0e,.2 (i) 7.Se-04 lh 3.0e-03 (k) 15e-02 Front -(I)7.e-04

Monito r O.O+- WL -- (m) I.5e-02 3.e35 I50e-02 (n) 1.5e-03 3.0e-3 I (o) 3.Oe-02 1.0e4.0 Revision 2 Page 9 Revision 2 Page 9

ISML16012.000-1

Appendix A -HRA CALCULATOR

REPORTS ISM LI 6012.000-1

Appendix A -HRA CALCULATOR

REPORTS pcc nicate data Ihucatom Easy to Good&Bad Inicator Foanal LocateI CoImunKicaUons

S O.e 4.0 0 (a) neg.S3.0e-033.e-03

0.Oe+00 I (c) I.Oe-03 YeIot.0e-0

A(d) 4.0e-03 3.0e-03 No ---o (e) 3.0e03 o.oe*Coo (6e3 3F)03 6.e-03 L 3Oe-03 3.OeO3 (g) 4.0e-03 1.0e-03 (3.Oe-03(h)

7.Oe-03 3.0e-03 For this scenario, normal reactor water level indication

is not available

and a hand-held

level monitor will be jumpered in. Although procedural

guidance on reading the monitor is clear, "not Easy" is selected to reflect the additional

challenges

to the task posed by this alternative

source for level indication.

pcd: Infoonation

mismeming M Cues as Stated mring of Specicr ,Rang I General Ta-anug I ~ ~Ifferences

II o.oesoo (a) neg.No---- -- -- ----- --- --- ----- --- ----- --- (b) 3.e-03 1.0e+O0 (c) 1.0e-02 1.0e-02 MCR indications

may not be accurate due to the Station Blackout so cues may not be as stated in procedures.

pce: Sip a step in procedure Obqgiousv&

Singl vs. NfUN*l Graphicaly

Placekeqing

Ad (a) 3.0e-03 3.3"1 (b) 3.0e-03 ()e-02 o.Oe+O 13.0e-03 (c) 3.0e-03 130e0eO0I (e) 2.0e-03 (h) 1.3e-02---------------------------(g) .oe-o3 1.0e-02 1.0e-4D 1 01) t.Oe -01 Revision 2 Page 10 Revision 2 Page 10

ISML16012.000-1

Appendix A -HRA CALCULATOR

REPORTS ISM LI 6012.000-1

Appendix A -HRA CALCULATOR

REPORTS pd' Misinterpret

instruction

Standard or AN Required Training on Step Ambiguous

wording Information

I--- ------ ------- ------- ------- (a) neg.(b) 3.0e-03 3.0e-02 (:c) 3.0e-02 Yes 1.0e4.00 NO1.0e,4 (d) 3.0e-03 0.0e+00 (e) 3.0e-02 3.0e-02 1(f) 6.0e-03 3.0e-02 (g) 6.0e-02 pcg: Misinterprt

decision ogic"NOr Statement

'ANUD or 'Or Both "AND" & practiced

Scenario Statement "OW 3-le0M (a) 1.6e-02 3.0e.02 I(b) 4.9e-02 1.2e-02 (c) 6.0e-03 0o.oe+oo l(d) 1.9-02 (e) 2.0e-03 O.Oe.+O0 (t) 6.0e-03 Yes 3~e-. (g) 1.0e-02 NO 3.0e..02 -(h) 3.1e-02.0e4.00 1.0e-03 (I) 3.0e-04---O.OeO Fi) 1.0e-03 0.0e+00 l .0e44)3.----- (k) neg.O.Oe.F (1) neg-pch: Delbe ate Wiolation BEleinAdequacy

Advere Reasonable

Polcy of of Instruction

Consequenceff

Alternatives "Vembatin"-.---- ------- --- ------- ------- ------- --- --(a)neg.Ye15.0e- (b) 5.oe-o1 NO.e00 I.OeO (c) I.Oe-Oo 1.0e+00 I O.Oe+O0 (d)neg.0.0e44)0 (e) neg.Revision 2 Page 11 Revision 2 Page11

1SML-16012.000-1

Appendix A -HRA CALCULATOR

REPORTS I SMLI 6012.000-1

Appendix A -HRA CALCULATOR

REPORTS Cognitive

Recovery RCICSBOFLOOD

Table 43: RCICSBOFLOOD

COGNITIVE

RECOVERY U- ', a_ , .E -Final Initial HEP Final S0) W C ValueLU OOr "(LU >S o n- -ý.'PCa: 1.5e-03 X -5.0e-01 7.5e-04 Pcb: 1.5e-02 X -X X MD 3.8e-03 5.7e-05 Pcc:: 3.0e-03 --X X -1.0e-02 3.0e-05 Pcd! 3.0e-03 -X X X -5.0e-03 1.5e-05 Pce: 6.0e-03 X X X MD 1. le-02 6.6e-05 Pof, nell. -1.0e+00 Pc-:. neg.- -1.0e+00 Pch: : ne .-1.0e+00 Sumof

Pch = Inita Pc-= 9.2e-04 Notes: Due to long timeframe

and severity of scenario, STA and Emergency

Response Facility will be available.

Operations

staffing to perform the procedures

was assessed by Xcel as optimal (several operators assigned as desired to each procedure)

so Extra Crew was credited.Used Moderate Dependency

due to high stress.Revision 2 Page 12 Revision 2 Page 12

ISML16012.000-1

Appendix A -HRA CALCULATOR

REPORTS ISM LI 6012.000-1

Appendix A -HRA CALCULATOR

REPORTS Execution

Unrecovered

RCICSBOFLOOD

Table 44: RCICSBOFLOOD

EXECUTION

UNRECOVERED

Procedure:

A.8-05.01, Manual Operation

of RCIC .Comment. Stress- Over Ride%* .- ,.Factor Step No. instrUction/Comment

Error ..THERP -HEP... ..* .....YPe.. .. 1. Table .. I .*Item * __._ * ._.In RCIC Room, verify open valves MO-2106 and MO-2096 Depress declutch lever and turn handwheel.

A.8-05.01, Step 8 Location:

Reactor Building EOM 20-7b 2 1.3e-03 5 EOC 20-13 1 1.3E-3 Total Step HEP 1.3e-02 Remove the pin securing the slip link to the governor lever to prevent interference

from the hydraulic

governor (See Attachment

1) 5 A.8-05.01, Step 9 Location:

Reactor Building EOM 20-7b 2 1.3e-03 EOC 99 1 1.OE-2 Total Step HEP 5.7e-02 Uncap and throttle open RCIC-27 condenser

cooling water starting YS A.8-05.01, Step 20 6082 drain. Close when steam is present. 5-22 Location:

Reactor Building EOM 20-7b 2 1.5e-03_5-_22_EOC 20-12 5 1.3E-3 Total Step HEP 1.3e-02 Throttle MO-2080 and control as necessary A.8-05.01

Steps Location:

Reactor Building EOM 20-7b 2 1.3e-03 5 17,18,25,26

EOC 20-12 5 1.3E-3 Total Step HEP 1.3e-02 At D31, Access Control -SET UP for Monitoring

RX Vessel level by A.8-05-01, Step 2, opening circuits and kick out to Part B M at D31 Location:

Reactor Building EOM 20-7b 3 1.3e-03_5 atD31_EOC

20-12 3 1.3E-3 Total Step HEP 1.3e-02 At D100, 1st Floor EFT -SET UP for Monitoring

RX Vessel level by A.8-05-01, Step 2, opening circuits and kick out to Part B At ST Location:

EFT EOM 20-7b 3 1 .3e-03 At EFT EOC 20-12 3 1.3E-3 Total Step HEP 1.3e-02 SET UP for Monitoring

RX Vessel level by selecting

level instrument

and PART B SET UP AND MONITOR OF RX VESSEL attaching

Fluke 707 monitoring

device -Control Room WITH FLUKE 707 Part B, Steps 29 & 29. SELECT a level instrument

from list below, 30P -MCR (preference

should be given to accessibility

and 5 environmental

conditions

such as radiation, temperature, lighting, etc.): In Control Room;Revision 2 Page A-1 3

ISML16012.000-1

Appendix A -HRA CALCULATOR

REPORTS SýProcedure:'A.8.45.01;

Manual Operationof.RCIC

Comment Stress. Over Ride Factor Step No. Instruction/Commetn:t-:

Error THERP HEP i. " .i : .... ..... ..-" ' i , " : i :+ Tabley. ; I;. , tem ... .I. .LI-2-3-85A, Reactor Vessel Water Level, Panel C-03, Term Strip TT-62 to TT-61.LI-2-3-85B, Reactor Vessel Water Level, Panel C-03, Term Strip PP-70 to PP-71.LI-2-3-91A, Fuel Zone, Panel C-03, Term Strip TT-59 to TT-58.30.If Level Indicator

selected for use, Then ATTACH one lead from Fluke 707 to each terminal point listed.Location:

Main Control Room EOM 20-7b 3 1.3e-03 EOC 20-12 13 1.3E-2 Total Step HEP 7.2e-02 SET UP for Monitoring

RX Vessel level by selecting

level instrument

and PART B SET UP AND MONITOR OF RX VESSEL attaching

Fluke 707 monitoring

device -Cable Spreading

Room WITH FLUKE 707 29. SELECT a level instrument

from list below, (preference

should be given to accessibility

and environmental

conditions

such as radiation, temperature, lighting, etc.): In Cable Spreading

Room;Part B, Steps 29.& LI-2-3-91A, Fuel Zone, Panel C-18, Term Strip BB- 5 30 -CSR 57 to BB-59.If Level Indicator

selected for use, Then ATTACH one lead from Fluke 707 to each terminal point listed.Location:

Cable Spreading

Room EOM 20-7b 3 1.3e-03 EOC 20-12 13 1.3E-2 Total Step HEP 7.2e-02 SET UP for Monitoring

RX Vessel level by selecting

level instrument

and PART B SET UP AND MONITOR OF RX VESSEL attaching

Fluke 707 monitoring

device -EFT WITH FLUKE 707 29. SELECT a level instrument

from list below, (preference

should be given to accessibility

and environmental

conditions

such as radiation, temperature, lighting, etc.): At 3rd Floor EFT, ASDS Panel;LI-2-3-86, Reactor Flooding Level, Panel C-292, Part B, Steps 29 & Term Strip (EFT 3) HH-4 to HH-5. 5 30 -EFT LI-2-3-91

B, Fuel Zone, Panel C-292, Term Strip (EFT 3) HH-1 to HH-2.If Level Indicator

selected for use, Then ATTACH one lead from Fluke 707 to each terminal point listed.Location:

EFT EOM 20-7b 3 1.3e-03 EOC 20-12 13 1.3E-2 I Revision 2 Page A-14

1SML16012.000-1

Appendix A -HRA CALCULATOR

REPORTS I SMLI 6012.000-1

Appendix A -HRA CALCULATOR

REPORTS Procedure:

A.8-05.01, ManUal Operation

of R(Step No.instruction/Cot

SET UP for Monitoring

RX Vessel level by selecting

level instrument

and attaching

Fluke 707 monitoring

device -Reactor Building PART B SET UP AND MONITOR OF RX VESSEL WITH FLUKE 707 29. SELECT a level instrument

from list below, (preference

should be given to accessibility

and environmental

conditions

such as radiation, temperature, lighting, etc.): At 962', Rx Bldg;LT-2-3-85A, Reactor Vessel Water Level, Panel C-56.LT-2-3-85B, Reactor Vessel Water Level, Panel C-55.LT-2-3-61, Reactor Flooding Level, Panel C-55.At 935', Rx Bldg;LT-2-3-112A, Fuel Zone, Rx Bldg 935' West, Panel C-122.LT-2-3-112B, Fuel Zone, Rx Bldg 935' East, Panel C-121.31. If level transmitter

selected for use, Then PERFORM the following:

a. REMOVE the cover (see Attachment

5 & 6).b. LIFT positive lead from its conductor (see Attachment

7).c. Slightly ENGAGE screw threads into transmitter.

d. CLAMP Fluke 707 leads in series with lifted positive wire and positive terminal point on transmitter.

Part B, Steps 29 &31 -RxB 5 Location:

Reactor Building EOM 20-7b 3 1 .3e-03 EOC 1 20-12 1 13 1 1.3E-2-t --Total Step HEP 7.2e-02 MONITOR OF RX VESSEL WITH FLUKE 707 (Conducted

separately

by DETERMINE

Rx water level by performing

the I&C) following: (see Attachment

8 -diagram of FLUKE 707 CALIBRATOR

pointing out buttons and displays)a. PRESS green button to START Fluke 707.b. PRESS MODE button until display reads MEASURE mA and Loop Power.c. USE Attachment

9 to obtain vessel level. [read Part B, Step 32 table of RCIC -mA VS. RPV WATER LEVEL]33. If connected

to LT-2-3-61

or LI-2-3-86, Then OPERATE RCIC turbine to maintain steady indication

as close to 8 mA as possible.34. If NOT connected

to LT-2-3-61

or LI-2-3-86, Then OPERATE RCIC turbine to maintain steady indication

as close to 20 mA as possible.Revision 2 Page A-15 Revision 2 Page A-1 5

1SML16012.000-1

Appendix A -HRA CALCULATOR

REPORTS Procedure:-A.8-05.01, Manual Operation

of RCIC Comment-w

.'Stress Over Ride, Factor Step INo .Instrudtion/comnment.

Error -~ THERP :F HEP.Typeý. Table,. Item Location:

Reactor Building EOM 20-7b 3 1.3e-03 EOC 20-11 1 1.3E-3 Total Step HEP 1.3e-02 Interpret

Fluke monitor readings using density compensation

tables in E-mail from Xcel Operations

to B.1.1 operations

manual, section 6 (posted in Control Room) Xcel PRA Manager, 2 July 2013 The indicated

level can be drastically

different

from the actual level depending

on the calibration

conditions

of the instrument (hot or cold calibration

conditions)

and the actual pressure/temperature

at the time of the reading. None of this information

is contained

in the A.8 procedures.

There are density 5 Part B, Step 32c compensation

tables in the B.1.1 operations

manual figures section six and they are also posted in the control room. It would take additional

action for the on-shift team/technical

staff to put this all together to determine

what actual level was from the readings that came off the fluke.Location:

Main Control Room EOM I 20-7b 3 1.3e-03 EOC 120-10 10 1.3E-2 Total Step HEP 7.2e-02 Maintain CST level and venfy valve status in the steam chase I Location:

Reactor Building EOM 20-7b 4 4.3e-03 5 EOC 20-12 5 1.3E-3 Total Step HEP 2.8e-02 Feedback from I&C Level Monitoring

i 5 Recovery 1 Location:

Reactor Building EOM 99 1 1.0e-02 Total Step HEP 5.0e-02 Feedback from Control Room 1 5 Recovery 2 Location:

Main Control Room EOM 20-7b .3 1 1.3e-03 Total Step HEP 6.5e-03 Revision 2 Page A-1 6

1SML-16012,000-1

Appendix A -HRA CALCULATOR

REPORTS I SMLI 6012.000-1

Appendix A -HRA CALCULATOR

REPORTS Execution

Recovery RCICSBOFLOOD

Table 4-5: RCICSBOFLOOD

EXECUTION

RECOVERY Critical Step No.Recovery Step No.Action HEP (Crit)HEP (Rec).Dep. Cond. HEP Total for De. (Recl Stan, A-8-05.01, Step 8 In RCIC Room, verify open valves MO-2106 and MO-2096 1.3e-02 7.3e-04 Recovery 2 Feedback from Control Room 6.5e-03 LD 5.6e-02 A-8-05.01, Step 20 -Uncap and throttle open RCIC-27 condenser

cooling water 1.3e-02 7.3e-04 22 starting YS 6082 drain. Close when steam is present.Recovery 2 Feedback from Control Room 6.5e-03 LD 5.6e-02 A.8-05.01

Steps 17, Throttle MO-2080 and control as necessary 18,25,26 13e02 1.4e04 Recovery 1 Feedback from I&C Level Monitoring

5.0e-02 MD 1.9e-01 Recovery 2 Feedback from Control Room 6.5e-03 LD 5.6e-02 A.8-05-01, Step 2, At D31, Access Control -SET UP for Monitoring

RX Vessel 1.3e-02 7.3e-04 at D31 level by opening circuits and kick out to Part B Recovery 2 Feedback from Control Room 6.5e-03 LD 5.6e-02 A.8-05-01, Step 2, At D100, 1st Floor EFT -SET UP for Monitoring

RX Vessel level 1.3e-02 7.3e-04 At EFT by opening circuits and kick out to Part B Recovery 2 Feedback from Control Room 6.5e-03 LD 5.6e-02 Part B, Steps 29 & SET UP for Monitoring

RX Vessel level by selecting

level 30 -MCR instrument

and attaching

Fluke 707 monitoring

device -7.2e-02 1.1e-02 Control Room Recovery 2 Feedback from Control Room 6.5e-03 MD 1.5e-01 Part B, Steps 29 & SET UP for Monitoring

RX Vessel level by selecting

level 30 -CSR Instrument

and attaching

Fluke 707 monitoring

device -Cable 7.2e-02 4.0e-03 Spreading

Room__Recovery 2 Feedback from Control Room 6.5e-03 LD 5.6e-02 Part B, Steps 29 & SET UP for Monitoring

RX Vessel level by selecting

level 7.2e-02 4.0e-03 30 -EFT instrument

and attaching

Fluke 707 monitoring

device -EFT Recovery 2 Feedback from Control Room 6.5e-03 LD 5.6e-02 Part B, Steps 29 & SET UP for Monitoring

RX Vessel level by selecting

level 31 -RxB Instrument

and attaching

Fluke 707 monitoring

device -7.2e-02 4.0e-03 Reactor Building Recovery 2 Feedback from Control Room 6.5e-03 LD 5.6e-02 Part B, Step 32 MONITOR OF RX VESSEL WITH FLUKE 707 (Conducted

1.3e-02 7.3e-04 separately

by I&C)Recovery 2 Feedback from Control Room 6.5e-03 LD 5.6e-02 Part B, Step 32c Interpret

Fluke monitor readings using density compensation

tables In B.1.1 operations

manual, section 6 (posted In Control 7.2e-02 7.0e-03 I Room)Recovery I Feedback from I&C Level Monitoring

5.0e-02 LD 9.8e-02 Revision 2 Page A-17 Revision 2 Page A-17

1SML16012.000-1

Appendix A -HRA CALCULATOR

REPORTS I SMLI 6012.000-1

Appendix A -HRA CALCULATOR

REPORTS Critical St A.8-05.05 A.8-05.01, ep No. Recovery Step No. .ý.Action.

HEP (Crit) HEP (Rec) Dep. Cond. HEP sTotapfor (Rec) : *step Maintain CST level and verify valve status in the steam chase 2.8e-02 1.6e-03 Recovery 2 Feedback from Control Room 6.5e-03 LD 5.6e-02 Step 9 Remove the pin securing the slip link to the governor lever to prevent interference

from the hydraulic

governor (See 5.7e-02 5.7e-02 Attachment

1)Total Unrecovered:.

5.2e-01 Total Recovered:

9.2e-02 Revision 2 Page A-18 Revision 2 Page A-1 8

ISML16012.000-1

Appendix A -HRA CALCULATOR

REPORTS A.2. HPV_SBO_FLOOD, Fail to operate the HPV using N2 bottles to provide containment

heat removal during SBO/Flood Basic Event Summary Plant DataFile ...File;Size.

File Datei ."Re&cordDate

Monticello

Ext 901120 06/28/13 06/28/13 Flooding SDP HRA June 2013.HRA John Spaargaren

& Pierre Macheret, Hughes Associates

Table 46: HPVSBOFLOOD

SUMMARY... .._*__"___._."_

__.___ '._____HEP

Sumrnhiaty

. ..: .., .-. -.. ..Pcog Pexe Total HEP Error Factor Method CBDTM THERP CBDTM + THERP Without Recovery 3.le-02 2.3e-01 With Recovery 6.1e-04 1.3e-02 1.3e-02 5 Initial Cue: Drywell pressure above 2 psig Cue Comments: The cue for action is that the TSC has recommended

venting the DW by using the Hard Pipe Vent using procedure

A.8-05.08, Manually Open Containment

Vent Lines.Initial procedure

entered on high drywell pressure is C.5-1200.

The DW/Torus Pressure leg directs operators

to C.5-3505.

For the limiting PRA case, it is assumed that normal and alternate

nitrogen and power via Y-80 is not available

and operators

must therefore

use A.8-05.08

to install pre-staged

nitrogen bottles directly to the inboard and outboard HPV isolation

valves to open them.Due to the SBO, it is assumed that there will be multiple impacts to indications, so the degree of clarity has been set at "Poor".Degree of Clarity of Cues & Indications:

Poor Procedures:

Cognitive:

C.5-1200 (PRIMARY CONTAINMENT

CONTROL flowchart (Monticello))

Revision:

16 Execution:

A.8-05.08 (Manually

Open Containment

Vent Lines) Revision:

1 Other: A.6 (ACTS OF NATURE (Monticello))

Revision:

43 Other: C.5-3505-A

0 Revision:

10 Cognitive

Procedure:

Step: DW/TORUS PRESSURE Revision 2 Page A-19 Revision 2 Page A-1 9

1SML16012.000-1

Appendix A -HRA CALCULATOR

REPORTS Instruction:

BEFORE DW pressure reaches Fig. D, DW Pressure Limit (56 psig) vent to stay below Fig. D, DW Pressure Limit per C.5-3505 Procedure

and Training Notes: Three JPM trials were performed

emulating

the specific external flooding conditions

of this scenario on 18 June 2013. Observations

were factored into this analysis.Training: Classroom, Frequency:

0.5 per year Simulator, Frequency:

0.5 per year JPM Procedure:

JPM-A.8-05.08-001 (Manually

Open Containment

Vent Lines) Revision:

0 Identification

and Definition:

This HFE is for the external flooding model for venting prior to core damage.1. Initial Conditions:

SBO due to external flooding.2. Initiating

Events: External flooding causes station blackout.3. Accident sequence (preceding

functional

failures and successes):

No containment

venting or heat removal Need to vent to maintain containment

integrity

prior to ultimate containment

pressure for RCIC injection 4. Preceding

operator error or success in sequence:

None.5. Operator action success criterion:

Align pre-staged

alternate

nitrogen bottles directly to AO-4539 and AO-4540 (located on the torus catwalk) to open the hard pipe vent.6: Consequence

of failure: Failure to vent containment

leads to containment

failure. Any subsequent

release will likely be through an unscrubbed

and unfiltered

release path.Key Assumptions:

JPM A.8-05.08-001, Rev. 0, Manually Open Containment

Vent Lines INITIAL CONDITIONS:

o Extreme flooding has led to a Station Blackout that has. existed at Monticello

for the last 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br />.o Div. 1 and Div 2 250 VDC battery systems have been depleted and are not available.

o The plant was in Shutdown Cooling until the station blackout and has since been slowly repressurizing

due to heating up.o Current RPV pressure is 75 psig-and slowly rising.o H SRV has failed to reseat and indication

of the tailpipe vacuum breaker sticking open have led to a Drywell pressure of 45 psig and rising about 1 psig every 30 minutes.o Efforts to align the diesel fire pump to DW sprays have been unsuccessful

due to the flooding.o The TSC has recommended

venting the DW by using the Hard Pipe Vent using procedure

A.8-05.08, Manually Open Containment

Vent Lines INITIATING

CUES (IF APPLICABLE):

o The CRS directs operator to initiate DW venting through the Hard Pipe Vent lAW procedure

A.8-05.08, Manually Open Containment

Vent Lines, Parts A and B.Revision 2 Page A-20

1SML16012.000-1

Appendix A -HRA CALCULATOR

REPORTS Hard Pipe Vent local manual operation

Job Performance

Measure entry condition

assumptions, Information

excerpted

from Hughes Associates

Record of Correspondence, Hard Pipe Vent Manual Operation

e-mails with Xcel Energy during June 2013, Hughes Associates, Baltimore, MD, 7 July 2013: Conditions

anticipated

following

a SBO resulting

from an external flooding event: o ERO has been manned for the past several days, with these procedures

predicted

and planned to be implemented

ahead of time o Plant is in cold shutdown condition (mode 4)o Operations

staffing to perform the procedures

would be optimal (several operators

assigned as desired to each procedure)

o Environment

would be consistent

with SBO (hot, dark, damp)o There would be more than 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> to perform the procedures, allowing several opportunities

to troubleshoot

and/or re-perform

steps if necessary o The ERO would place maximum priority on maximizing

chances of successful

performance

of these procedures

Operator Interview

Insights: The JPM that was completed

by Xcel with 2 ROs and 2 NLOs was JPM A.8-05.08-001, Rev. 0, Manually Open Containment

Vent Lines. The average time to complete the JPM was 30 minutes given the information

that the N2 bottles were staged on the CRD catwalk. There were no problems or issues that required any of the operators

to stop and get clarifying

information, it was identified

that removing fittings was not the best idea it would be better if the lines had tee's installed

where the caps could be removed and the appropriate

lines connected.

This way the capped connection

could be labeled to further minimize connecting

to the wrong fitting. The operators

stated that strips of non-skid should be placed on the areas around the site for safety reasons. They also mentioned

using the LED headlights

versus flashlights

to allow both hands to be free.Manpower Requirements:

..._....._.____"_

Ci~Wei~ier

hclu~de~d::

TotaAIIVailale

4KRqiiiredfr

'Noe____________

Ex'c~itip'"in

_ _ _ __ _Reactor operators

Yes 2 1 Plant operators

Yes 2 0 Mechanics

Yes 2 0 Electricians

Yes 2 0 I&C Technicians

Yes 2 0 Health Physics Technicians

Yes 2 0 Chemistry

Technicians

Yes 1 0 Execution

Performance

Shapina Factors: Environment:

Lighting Portable Heat/Humidity

Hot / Humid Radiation

Background

Atmosphere

Steam (although

steam will not be present, this PSF was used to indicate an off-normal

condition, such as would be present for flood and SBO)Special Requirements:

Tools Required Adequate Available Parts Required I I_ Adequate Revision 2 Page A-21

1SML16012.000-1

Appendix A -HRA CALCULATOR

REPORTS Clothing Required Adequate Complexity

of Response:

Cognitive

Complex Execution

Complex Equipment

Accessibility

Main Control Room Accessible (Cognitive):

Equipment

Accessibility

Reactor Building With Difficulty (Execution):

Stress: High Plant Response As Expected:

Yes Workload:

High I Performance

Shaping Factors: Negative Performance

Shaping Factor Notes: The response is considered

to be Complex due to the flooding and SBO impacts to lighting and accessibility.

Flashlights, headlamps

and boots were considered

necessary

by Training when the JPMs were performed

for these tasks.The Equipment

Accessibility

is evaluated

as With Difficulty

due to Rx building lighting and flooding issues.Key Assumptions (see that section) regarding

the conditions

provided to Training for performing

the JPM for this task said that the "Environment

would be consistent

with SBO (hot, dark, damp)". The Training insights from the JPM performance

stated that the operators

recommended

the use of "LED headlights

versus flashlights", so it is clear that portable lighting is used.Despite preparations

and training, the flooding scenario is considered

to be a high stress situation.

The steps identified

as Critical in JPM-A.8-05.08-001

were used for the Execution

quantification.

Timing: T SW 15.00 Hours T 5.50 Hours delay T1/2 10.00 Minutes TM 45.00 Minutes M ~ I1 Cue I Irreversible

DamageState

I-I.t=0 Timing Analysis: TO = Station Blackout.Tsw = Per MAAP run Rcic-dgl 3-cts-ABS

performed

in support of an external flooding SDP, containment

pressure reaches 56 psig at 14 hours1.62037e-4 days <br />0.00389 hours <br />2.314815e-5 weeks <br />5.327e-6 months <br /> following

a SBO (flooding

>930'). Core temperature

reaches 1800 degrees F at 15 hours1.736111e-4 days <br />0.00417 hours <br />2.480159e-5 weeks <br />5.7075e-6 months <br /> due to CST depletion

and no transfer of RCIC to the torus. This is conservative

timing as refilling

of the CST is very likely.Td = 5.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> -Based on an interview

conducted

in a prior analysis with a senior Shift Manager, the order to begin the procedure

to manually operate the hard pipe vent would be given at approximately

27 psig containment

pressure.

This is due to the step in C.5-1200 (DW/Torus

Pressure leg) that says if you cannot restore and maintain drywell pressure within Figure 0 (27psig for 0 ft torus level), then maintain drywell pressure less than Figure D (56 psig).The 5.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> is based on MAAP run Rcic-dg13-cts-ABS

as the time when drywell pressure reaches 42 psia (27 psig) [Worksheet

d43-1, column AC Drywell Pressure]T1/2 = According

to the initial conditions

assumed by Training for the Job Performance

Measure performed

for this task, the ERO will have been manned for the past several days, with these procedures

Revision 2 Page A-22

1 SML16012.000-1

Appendix A -HRA CALCULATOR

REPORTS predicted

and planned to be implemented

ahead of time. Daily planning meetings will have been held to discuss actions to be taken, so the 10 minutes is simply an estimate of the meeting time between TSC and ERF personnel

to make the actual decision to vent the DW by using the Hard Pipe Vent. The control room supervisor (CRS) will then direct operators

to initiate the process.Tm = Results of HPV local manual operation

Job Performance

Measure A.8-05.08-001

performed

18 June 2013. The procedure

was performed

four times, taking an average of 30 minutes. Additional

15 minutes for C.5-3505-A

steps 3 and 4.Time available

for cognition

and recovery:

525.00 Minutes Time available

for recovery:

515.00 Minutes SPAR-H Available

time (cognitive):

525.00 Minutes SPAR-H Available

time (execution)

ratio: 12.44 Minimum level of dependence

for recovery:

ZD Revision 2 Page A-23

1SMLII16012.000-1

Appendix A -HRA CALCULATOR

REPORTS Cognitive

Unrecovered

HPVSBOFLOOD

Table 47: HPVSBOFLOOD

COGNITIVE

UNRECOVERED

Pc Failure .Mecdhanism

... -". 1 .1 ." 1 1 .Branch : .HEP.::..Pca: Availability

of Information

d 1.5e-03 PCb: Failure of Attention

m 1.5e-02 Pcc: Misread/miscommunicate

data e 3.0e-03 Pcd: Information

misleading

b 3.0e-03 Pce: Skip a step in procedure

e 2.0e-03 Pcf: Misinterpret

instruction

a neg.Pcg: Misinterpret

decision logic c 6.0e-03 PCh: Deliberate

violation

a neg.Sum of Pca through PCh = Initial Pc = 3.1e-02 Notes: Presumed that SBO causes issues with normal alarms and indications

so pc-a through -d were adjusted consistent

with insights from EPRI 1025294, A Preliminary

Approach to Human Reliability

Analysis for Extemal Events with a Focus on Seismic, October 2012.Revision 2 Page A-24 Revision 2 Page A-24

1SML16012.000-1

Appendix A -HRA CALCULATOR

REPORTS pca: Avlabhty of infonnation

Indiation

ail in CR Indication

bminglAlftmate

Training on CR Accurate in Procedure

Indcators I.0e-01 (a) neg..Oe.00 1.0e+00 (b) neg.O.0e4.00 I .oe-o (c) neg-7- e0(d) 1-pe-03 Yes 5.0e-0 (e) 5.0e-02 No1.e+00 f) 5.oe-o0 1.0e+00 1.0e-+O (g) .0" WO MCR indications

may not be accurate due to the Station Blackout, however, either procedural

or informal crew information

on alternate

indications

and training should provide operator input to decision-making.

pcrb: Failure of attention Low vs. Hi Check vs. Monitor Front vs. Back Aarmed vs.Not Wokdload Panel Alarmed Evout(a) neg-O.Oe0 Back .0(b) 1.5e-4 LOW 3.0e-03 (c) 3.0e-03 1.0e+00 1.0e+00 Front 5e-2(d) 1.-%-04 5.0e-02O Monitor I0-0e+00 l(e) 3.0e-03 3.0e-03 Back 5.0e-02 (f) 3.0e-04 1. Nice 3.0e-03 1(g) 6.0e-03 2. ic Fro,,t 15.,10 (h eg-5(b0n-02 Check O.Oe+0 18 0(i) neg.0.0e*WBack

(.0e.so 5.0e-02e-04

WIgh 3.0e-03 1Ae(k) 1.e-02 Front ()7.5e-04 Monitor --- Oe --0- (m) I.5e-02 3 -Back 50e-02 (n) 1.5e-03 3.Oe-03 I1.0e0 (o) 3.0e-02 Revision 2 Page A-25 Revision 2 Page A-25

I SM L16012.000-1

Appendix A -HRA CALCULATOR

REPORTS ISM LI 6012.000-1

Appendix A -HRA CALCULATOR

REPORTS pcc: Misreadftniscmmnnicate

data Inhicators

Easy to Good--ad Indicator

Fom- --Locate cminunicafions

I O.Oe.H) (a) neg.O.Oe.)O 3i 3 (b) 3.0e-03 , O-Oe+0 (c) 1.0e-03 0(g) 4.0e-03 1.0e-03 (h) 4.0e-03 3.0e-03 o.oe-4oo (g) 3.Oe-03 13.0e-03 3.oe-o3 (h) 7.Oe-O3 pcd: Infonmtion

fidNilng M Cuesas Stated Warnng SpecoTc Tbn,,ig e Tining Dire II o.oe+0o (a) meg.No--------------------

---

---

(b) 3Je-03.0-L-02 (c) 1.0e-02 1..eOe0 1..od-o (d) 1.Oe-O1 1.Oe+OO (e) 1.0e" 0 MCR indications

may not be accurate due to the Station Blackout so cues may not be as stated in procedures.

pce: Sli a step in procedure Obvious Ms Eing s Mlle V& MUPleawaf

cekeqing A&d 13.Oe-O3(a)

1 .0e-03 3.3e-01 (b) 3.Oe-03 1.0e.-02 O.e.O0 3(c) 3.0e-03.Oe.001e-0 (d) 1.8e-02-(e) 4-e-03 3.3e-o------.----

Yes3.0e-03

13.e-3 (g) 6.0e-03 1.Oe4-OI (h) I.3e-02 1..0e-02 1.0e-01 (i) t.0e -0t Revision 2 Page A-26 Revision 2 Page A-26

1SML16012.000-1

Appendix A -HRA CALCULATOR

REPORTS I SMLI 6012.000-1

Appendix A -HRA CALCULATOR

REPORTS pf: Misinterpret

instruction

Standard or AM Required 7haning on Step Ambiguous

wonling Information

--- ------- ------- ---------

--- (a) neg.(b) 3.oe-03 3.0e-02 (c) 3.0e-02 NO .0e4H (d) 3.0e-03 o.e-,.o I(e) 3.0e-02 3.0e-02 1.0e-01 (f) 6.Oe-03 3.0e..02 I 0 (g) 6.0e-02 pcg: Mi§sinrmpt

decision ogic NMor statemmut -ir*N or -ow- Both AND' & IPracticed

Scenail Statement "OFr 3.3e41 (a) 1.Ge-02 3.0e-02 (b) 4.9--02 1.2-02 -3(c) 6.0e-03 33.ie-Ol-.Oe. (d) .9e-02 6.0e-03 (1.0e.9.42

3.3e-1 (e) 2.0e-03 O.Oe-Oe-0 Yes OO + 1.00,6 0O (f) 6.0e-03 (g) t.Oe-02 No 3.0e-02 --(h) 3.1e-02 1.0e30.-0 I.0e-03 30"1 3.0e-0M 13.3e-01 (k) neg.O.OedO l- (1) neg.pch: Deliberate

violation Belef in Adequacy Adverse Reasonable

Poky of of Instructon

Consequence

if Alternatis

"'Verbatic" oew-------

--- ------- ------- --------- ------- ------ (a) neg.Yes 5.0eM (b) 5.0"-01 oI. (c) 1.0e4W I.Oe4O110e00

O.Oe,.O0 (d) neg.Io.oe.,o (e) neg.Revision 2 Page A-27 Revision 2 Page A-27

1SML16012.000-1

Appendix A -HRA CALCULATOR

REPORTS I SMLI 6012.000-1

Appendix A -HRA CALCULATOR

REPORTS Cognitive

Recovery HPVSBOFLOOD

Table 48: HPVSBOFLOOD

COGNITIVE

RECOVERY< a) (" I- LL '.D Final InitiaIIl.

HE > Z 1 -'5: -r-.O Value0 CO W nOa C -O) Lu Value Pc. 1.5e-03 X X -2.5e-01 3.8e-04 Pcb: 1.5e-02 X X X MD 3.8e-03 5.7e-05 Pc': 3.0e-03 X X MD 2.1e-02 6.3e-05 PCd: 3.0e-03 X X X MD 7.3e-03 2.2e-05<PCe: 2.0e-03 X X X MD 1.0e-02 2.0e-05 , :; neg. -1.0e+00 P. 6.e-03 X X X MD 1.1 e-02 6.6e-05-I--neg. 1.0e+00 P 6 SuoP dt 6.1e-04 Notes: Due to long timeframe

and severity of scenario, STA and Emergency

Response Facility will be available.

Operations

staffing to perform the procedures

was assessed by Xcel as optimal (several operators assigned as desired to each procedure)

so Extra Crew was credited.Used Moderate Dependency

due to high stress.Revision 2 Page A-28 Revision 2 Page A-28

1SML16012.000-1

Appendix A -HRA CALCULATOR

REPORTS ISM LI 6012.000-1

Appendix A -HRA CALCULATOR

REPORTS Execution

Unrecovered

HPVSBOFLOOD

Table 49: HPVSBOFLOOD

EXECUTION

UNRECOVERED

ProcedurYe

C:A8-5.08,eManuallyOpen

Containm ent CvehtLines

., omment Stress Over Ride I IStep.No.*

jnstructionlComnent,-, Error' -,. HTHERP HEP Factor., Type' Table Item -..___- _Connect and apply pressure from AH-1 cylinder to rupture Rupture Disk PSD-4543 A.8-05.08, Step 4 Location:

Reactor Building EOM 20-7b 2 1.3e-03 EOC 20-12 5 1.3E-3 Total Step HEP 1.3e-02 Connect and adjust AH-1 regulator

to less than 100 psig and slowly open AH-1 discharge

valve to open valve AO-4539 5 A.8-05.08, Step 5 Location:

Reactor Building EOM 20-7b 4 4.3e-03 EOC 20-13 5 1.3E-2 Total Step HEP 8.7e-02 Connect and adjust AH-2 regulator

to less than 100 psig and slowly open AH-2 discharge

valve to fully open valve AO-4540 5 A.8-05.08, Step 6 Location:

Reactor Building EOM 20-7b 4 4.3e-03 EOC 20-13 5 1.3E-2 I Total Step HEP 8.7e-02 Open and Close the HPV isolation

valves as directed by shift supervisor

C.5-3505 Part A, Location:

Reactor Building EOM 20-7b 1 4.3e-04 5 Step 3 1 EOC 20-13 2 3.8E-3 I Total Step HEP 2.1e-02 Monitor Containment

Pressure and Radiation

Levels in the Hard Pipe C.5-3505 Part A Vent. 5 Step 4 Location:

Reactor Building EOM 20-7b 1 4.3e-04 Step 4 EOC 20-10 1 3.8E-3 Total Step HEP 2.1e-02 Feedback from Control Room 5 Recovery Location:

Main Control Room EOM 20-7b 3 1.3e-03 I Total Step HEP 6.5e-03 Revision 2 Page A-29 Revision 2 Page A-29

1SML16012.000-1

Appendix A -HRA CALCULATOR

REPORTS Execution

Recovery HPV_SBOFLOOD

Table 4-10: HPVSBOFLOOD

EXECUTION

RECOVERY c it.Recovery

Step No.. -i HEP (crit)i HEP'Rec .Dep. P"Cond. :.Totalffor.

~Criticalý

'te k o .__________

_______________________________________________________

....___.... ..._(Rec) Step A.8-05.08, Step 4 Connect and apply pressure from AH-1 cylinder to rupture 1.3e-02 7.3e-04 Rupture Disk PSD-4543 Recovery Feedback from Control Room 6.5e-03 LD 5.6e-02 A.8-05.08, Step 5 Connect and adjust AH-1 regulator

to less than 100 psig and slowly open AH-1 discharge

valve to open valve AO-4539 8.7e-02 4.9e-03 Recovery Feedback from Control Room 6.5e-03 LD 5.6e-02 A.8-05.08, Step 6 Connect and adjust AH-2 regulator

to less than 100 pslg and 8.7e-02 4.9e-03 slowly open AH-2 discharge

valve to fully open valve AO-4540 Recovery Feedback from Control Room 6.5e-03 LD 5.6e-02 C.5-3505 Part A, Open and Close the HPV isolation

valves as directed by shift 2.1 e-02 1.2e-03 Step 3 supervisor

Recovery Feedback from Control Room 6.5e-03 LD 5.6e-02 C.5-3505 Part A, Monitor Containment

Pressure and Radiation

Levels in the 2.1 e-02 1.2e-03 Step 4 1 Hard Pipe Vent.I Recovery Feedback from Control Room 6.5e-03 LD 5.6e-02-* .: .Total ....I.- Unrecoered:-

2.3e1- .Total R 2ovIered:

1.3e2 Revision 2 Page A-30 Revision 2 Page A-30

ISML16012.000-1

Appendix A -HRA CALCULATOR

REPORTS A.3. RCICSBOFLOOD, Fail to manually operate RCIC during SBO and extreme flooding conditions (SPAR-H)Basic Event Summary'Planlt;:".. i. Data :File Dati e

Rebo d

:".Monticello

Ext 909312 07/02/13 07/02/13 Flooding SDP HRAJune 2013_SPAR

H quant for sensitivity.HRA

Table 11: RCIC_SBOFLOOD

SUMMARY[Ana l, i Resu!ts:.-I4

Cognitive

Execution[Failor

3.2e.. 9.1 e-02 1 .4e-01 Plant: Monticello

Initiating

Event: External Flood + SBO Basic Event Context: The flooding engineer provides daily updates to the station on high river water levels including

potentials

to rise above any A.6 trigger points. At this point, heightened

awareness

of the potential

for flooding is implemented.

When river level exceeds 921 feet an evaluation

of EALs would be performed.

If visible damage has occurred due to flood water rising greater than 921 feet, then an Alert per EAL HA1.6 would be declared.Prior to river levels reaching these levels, operators

would be walking down the A.8 procedures

for alternate

methods to vent primary containment

and operate RCIC remotely.

This would involve staging of equipment

in the torus area to open the Hard Pipe Vent and verification

that equipment

is properly staged to operate RCIC remotely.EDGs and batteries

are not available.

Shutdown cooling, HPCI, and RCIC are not available

from normal electrical

means. RCIC is available

for manual operation.

Operators

have temporary

level indication

setup in the reactor building.

Pressure indication

is available

in the direct area of the level transmitters.

The building is dark and most likely water in the basement of the reactor building.

Additional

portable lights are available

to assist with lighting and boots staged for higher water. The operators

would utilize A.8-05.01

to un-latch the governor from the remote servo linkage and throttle steam flow to RCIC to start the turbine rolling while coordinating

with operators

monitoring

water level and reactor pressure.

Upon reaching the high end of the level band the operators

would throttle closed the steam admission

valve and await direction

to re-start RCIC. Local operation

of RCIC is demonstrated

each refueling

outage during the over speed test. Operation

of a coupled turbine run is less complex because the turbine is easier to control with a load.Revision 2 Page A-31

ISML16012.000-1

Appendix A -HRA CALCULATOR

REPORTS Timing: T 7.97 Hours T delay 5.75 Hours i T1/2 10.00 Minutes TM 80.00 Minutes 1 Irreversible

Cue DamageState

t=o Timing Analysis:

TO = Station Blackout Tsw = Time from Station Blackout to the time by which RCIC must be restored.Per Monticello

MAAP Calculations, case "SBOCase3-RI", 27 June 2013: Time to TAF = 7.17 hrs Time to -149" = 7.2 hrs Time to 1800 F = 7.97 hrs Damage is assumed to occur if the temperature

exceeds 1800 F or 7.97 hrs, so this was used as the time by which RCIC restoration

is required.Tdelay = PRA battery calc (PRA-CALC-1

1-002) indicates

that there are 5.75 hrs until RCIC battery depletion.

Also, the RCIC Water Flow (column BC) of the d41 tabs in the "SBOCase3-RI" MAAP analysis spreadsheet

shows that RCIC injection

stops at approximately

the same time (5.74 hrs), so the MAAP runs agree with the calc. This Tdelay can be considered

somewhat conservative, since in reality, it is likely that an action would be taken before waiting for battery depletion.

T1/2 = The cue for action is that the TSC and the Emergency

Response Director have determined

that RCIC operation

is needed. Daily planning meetings will have been held to discuss actions to be taken as soon as the diesels are lost, so the 10 minutes is simply an estimate of the meeting time between TSC and ERF personnel

to make the actual decision to manually operate RCIC. The Control Room Supervisor (CRS) directs operator to initiate RCIC and inject into the RPV using procedure

A.8-05.01, Manual Operation

of RCIC, Part A, Placing RCIC in Service.Tm = Results of RCIC local manual operation

Job Performance

Measure performed

18 June 2013. The procedure

was performed

three times, taking 49 minutes, 37 minutes and 50 minutes to complete for an average time of 45 minutes. 50 minutes was used as the conservative

value for JPM performance.

The JPM did not include the performance

of Part B for installation

and use of the Fluke level monitoring

device; this was estimated

to require 30 minutes, so the total time for Tm was estimated

as 50 min + 30 min = 80 min.Time available

for recovery:

43.20 Minutes SPAR-H Available

time (cognitive):

53.20 Minutes SPAR-H Available

time (execution)

ratio: 1.54 Minimum level of dependence

for recovery:

LD Revision 2 Page A-32 Revision 2 Page A-32

1SML16012.000-1

Appendix A -HRA CALCULATOR

REPORTS ISMLI6OI2.000.1

Appendix A -HRA CALCULATOR

REPORTS PART I. DIAGNOSIS PSFss PSF ,ve;s9 %fMultlper~or<.

Available

Time Inadequate

Time P(failure)

= 1.0 (recommended

choice Barely adequate time (~ 2/3 x nominal) 10 based on timing Nominal time 1 information

in bold) Extra time (between 1 and 2 x nominal 0.1 and > 30 min)Expansive

time (> 2 x nominal and > 30 X 0.01 min)Insufficient

Information

I Stress Extreme 5 High X 2 Nominal 1 Insufficient

Information

I Complexity

Highly complex 5 Moderately

complex X 2 Nominal 1 Obvious diagnosis

0.1 Insufficient

Information

1 Experience/Training

Low 10 Nominal X 1 High 0.5 Insufficient

Information

1 Procedures

Not available

50 Incomplete

20 Available, but poor 5 Nominal X 1 Diagnostic/symptom

oriented 0.5 Insufficient

Information

1 ErgonomicslHMI

Missing/MisleadingJ

50 Poor 10 Nominal X I Good 0.5 Insufficient

Information

1 Fitness for Duty Unfit P(failure)

= 1.0 Degraded Fitness 5 Nominal X 1 Insufficient

Information

1 Work Processes

Poor 2 Nominal 1 Good X 0.8 Insufficient

Information

1 Revision 2 Page A-33 Revision 2 Page A-33

ISM LI6012.000-1ApndxA-HACLUTORERS

Appendix A -HRA CALCULATOR

REPORTS Diagnosis

HEP: 3.2e-04 PART I1. ACTION PSFs PSF IUVeis. ~ Multi 11ýr for.__________________

griagn sis Available

Time Inadequate

Time P(failure)

= 1.0 (recommended

choice Time available

is -the time required 10 based on timing Nominal time X 1 information

in bold) Time available

>= 5x the time required 0.1 Time available

>= 50x the time required 0.01 Insufficient

Information

1 Stress/Stressors

Extreme 5 High X 2 Nominal 1 Insufficient

Information

1 Complexity

Highly complex 5 Moderately

complex X 2 Nominal 1 Insufficient

Information

1 Experience/Training

Low 3 Nominal X 1 High 0.5 Insufficient

Information

1 Procedures

Not available

50 Incomplete

20 Available, but poor X 5 Nominal 1 Insufficient

Information

1 Ergonomics/HMI

Missing/Misleading

50 Poor X 10 Nominal 1 Good 0.5 Insufficient

Information

1 Fitness for Duty Unfit P(failure)

= 1.0 Degraded Fitness 5 Nominal X 1 Insufficient

Information

1 Work Processes

Poor 5 Nominal 1 Good X 0.5 Insufficient

Information

0.5 Revision 2 Page A-34 Revision 2 Page A-34

ISML16012.000-1

Appendix A -HRA CALCULATOR

REPORTS Action Probability:

9.1e-02 [Adjustment

applied: 1.0e-3 * 1.0e+02 / (1.0e-3 * (1.0e+02 -1) + 1)]PART Ill. DEPENDENCY

caeI Im In~ mC..-mhwamc cwi Task Failure WITHOUT Formal Dependence:

9.1le-02 Task Failure WITH Formal Dependence:

1 .4e-01 Revision 2 Page A-35 Revision 2 Page A-35

ISML16012.000-1

Appendix A -HRA CALCULATOR

REPORTS A.4. HPVSBOFLOOD, Fail to operate the HPV using N2 bottles to provide containment

heat removal during SBO/Flood (SPAR-H)Basic Event Summary.:Plant , :Datale FileSize"..

• FileDate : Rerd Date Monticello

Ext 901120 06/28/13 06/28/13 Flooding SDP HRAJune 2013-SPAR

H quant for 1 sensitivity.HRA

John Spaargaren

& Pierre Macheret, Hughes Associates

Table 412: HPVSBOFLOOD

SUMMARY AnalyssResults-,*

Cognitive

Execution Fe ! rN r 1b6 1i.ii 3.2e-04 5.0e-03 Total :HEP. I 5.5e-02 Plant: Monticello

Initiating

Event: External Flood + SBO Basic Event Context: The flooding engineer provides daily updates to the station on high river water levels including

potentials

to rise above any A.6 trigger points. At this point, heightened

awareness

of the potential

for flooding is implemented.

When river level exceeds 921 feet an evaluation

of EALs would be performed.

If visible damage has occurred due to flood water rising greater than 921 feet, then an Alert per EAL HA1.6 would be declared.Prior to river levels reaching these levels, operators

would be walking down the A.8 procedures

for alternate

methods to vent primary containment

and operate RCIC remotely.

This would involve staging of equipment

in the torus area to open the Hard Pipe Vent and verification

that equipment

is properly staged to operate RCIC remotely.EDGs and batteries

are not available.

Shutdown cooling, HPCI, and RCIC are not available

from normal electrical

means. RCIC is available

for manual operation.

Revision 2 Page A-36 Revision 2 Page A-36

1SML16012.000-1

Appendix A -HRA CALCULATOR

REPORTS Timina: T S 15.00 Hours Tdelay 5.50 Hours T1/2 10.00 Minutes TM 45.00 Minutes Ireversible

Cue DamageState

t=o Analysis:

TO = Station Blackout.Tsw = Per MAAP run Rcic-dg13-cts-ABS

performed

in support of an external flooding SDP, containment

pressure reaches 56 psig at 14 hours1.62037e-4 days <br />0.00389 hours <br />2.314815e-5 weeks <br />5.327e-6 months <br /> following

a SBO (flooding

>930'). Core temperature

reaches 1800 degrees F at 15 hours1.736111e-4 days <br />0.00417 hours <br />2.480159e-5 weeks <br />5.7075e-6 months <br /> due to CST depletion

and no transfer of RCIC to the torus. This is conservative

timing as refilling

of the CST is very likely.Td = 5.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> -Based on an interview

conducted

in a prior analysis with a senior Shift Manager, the order to begin the procedure

to manually operate the hard pipe vent would be given at approximately

27 psig containment

pressure.

This is due to the step in C.5-1200 (DW/Torus

Pressure leg) that says if you cannot restore and maintain drywell pressure within Figure 0 (27psig for 0 ft torus level), then maintain drywell pressure less than Figure D (56 psig).The 5.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> is based on MAAP run Rcic-dg13-cts-ABS

as the time when drywell pressure reaches 42 psia (27 psig) [Worksheet

d43-1, column AC Drywell Pressure]T1/2 = According

to the initial conditions

assumed by Training for the Job Performance

Measure performed

for this task, the ERO will have been manned for the past several days, with these procedures

predicted

and planned to be implemented

ahead of time. Daily planning meetings will have been held to discuss actions to be taken, so the 10 minutes is simply an estimate of the meeting time between TSC and ERF personnel

to make the actual decision to vent the DW by using the Hard Pipe Vent. The control room supervisor (CRS) will then direct operators

to initiate the process.Tm = Results of HPV local manual operation

Job Performance

Measure A.8-05.08-001

performed

18 June 2013. The procedure

was performed

four times, taking an average of 30 minutes. Additional

15 minutes for C.5-3505-A

steps 3 and 4.Time available

for recovery:

515.00 Minutes SPAR-H Available

time (cognitive):

525.00 Minutes SPAR-H Available

time (execution)

ratio: 12.44 Minimum level of dependence

for recovery:

ZD Revision 2 Page A-37 Revision 2 Page A-37

1SML16012.000-1

Appendix A -HRA CALCULATOR

REPORTS PART I. DIAGNOSIS P PSFs,6V , AfPSF vels u-ti'for-Dagposis, Available

Time Inadequate

Time P(failure)

= 1.0 (recommended

choice Barely adequate time (~ 2/3 x nominal) 10 based on timing Nominal time 1 information

in bold) Extra time (between 1 and 2 x nominal 0.1 and > 30 min)Expansive

time (> 2 x nominal and > 30 X 0.01 min)Insufficient

Information

Stress Extreme 5 High X 2 Nominal 1 Insufficient

Information

1 Complexity

Highly complex 5 Moderately

complex X 2 Nominal 1 Obvious diagnosis

0.1 Insufficient

Information

1 Experience/Training

Low 10 Nominal X 1 High 0.5 Insufficient

Information

1 Procedures

Not available

50 Incomplete

20 Available, but poor 5 Nominal X 1 Diagnostic/symptom

oriented 0.5 Insufficient

Information

1 Ergonomics/HMI

Missing/Misleading

50 Poor 10 Nominal X 1 Good 0.5 Insufficient

Information

1 Fitness for Duty Unfit P(failure)

= 1.0 Degraded Fitness 5 Nominal X 1 Insufficient

Information

1 Work Processes

Poor 2 Nominal 1 Good X 0.8 Insufficient

Information

1 Revision 2 Page A-38 Revision 2 Page A-38

1 SML-16012.000-I

Appendix A -HRA CALCULATOR

REPORTS I SMLI 6012.000-1

Appendix A -HRA CALCULATOR

REPORTS Diagnosis

HEP: 3.2e-04 PART II. ACTION.PSFs,, PSFLevels'

s Multiplier

for S~ Diagflosis

Available

Time Inadequate

Time P(failure)

= 1.0 (recommended

choice Time available

is -the time required 10 based on timing Nominal time X 1 information

in bold) Time available

>= 5x the time required 0.1 Time available

>= 50x the time required 0.01 Insufficient

Information

1 Stress/Stressors

Extreme 5 High X 2 Nominal 1 Insufficient

Information

1 Complexity

Highly complex 5 Moderately

complex 2 Nominal X I Insufficient

Information

1 Experience/Training

Low 3 Nominal 1 High X 0.5 Insufficient

Information

1 Procedures

Not available

50 Incomplete

20 Available, but poor 5 Nominal X 1 Insufficient

Information

1 Ergonomics/HMI

Missing/Misleading

50 Poor X 10 Nominal 1 Good 0.5 Insufficient

Information

I Fitness for Duty Unfit P =failure)

1.0 Degraded Fitness 5 Nominal X 1 Insufficient

Information

1 Work Processes

Poor 5 Nominal 1 Good X 0.5 Insufficient

Information

0.5 Action Probability:

5.0e-03 Revision 2 Page A-39 Revision 2 Page A-39

ISMLI16012.000-1

Appendix A -HRA CALCULATOR

REPORTS PART II1. DEPENDENCY

C,=, TD I E I I C , F.-- -Cb ntin i...,=, , w M&IMAB ~ F, ib Task. Failre WTHOUForal

D endnce socb addiiorW khedlaf r-I.-ks. &k*T Faaulia u HD 5em Task Failure WITHOUT Formal Dependence:

5.3e-03 Task Failure WITH Formal Dependence:

5.5e-02 Revision 2 Page A-40 Revision 2 Page A-40'

ISML16012.000-1

B. APPENDIX B -EVENT TREES Appendix B -EVENT TREES Revision 2 Page B-I Revision 2 Page B-1

EXTERNAL FLOOD >930' < 935' EARLY WARNING REACTOR BUILDING PROTECTED

RCIC/RPV & HARD PIPE VENT Prob Name SUCCESSFUL

EARLY WARNING O.OOE+00 FLOOD <935'0.891 RCIC SUCCESS 0.894 EXTERNAL FLOOD >930'[8.90E-06]

[1]SUCCESSFUL

EARLY WARNING[0.106]O.00E+00 7.09E-06 8.41 E-07 0.OOE+00 7.72E-07 0.15E-08 1 07F-07 DK OK'D Seq 1:)K DK ,D Seq 2 MD Seq 3 O.00E+00 FLOOD > 935'[0.109]RCIC SUCCESS REACTOR BLDG PROTECTED 0.894 0.89 FAILURE TO PROTECT RB[0.106]1l I[0.11]IMonticello, Flood SDP 930-935.eta

17/3/2013

1 Page 1 IMonticello

Flood SDP 930-935.eta

7/3/2013 Page 1

EXTERNAL FLOOD >930' < 935' EARLY WARNING REACTOR BUILDING PROTECTED

RCIC/RPV & HARD PIPE VENT Prob I Name SUCCESSFUL

EARLY WARNING O.OOE+00 FLOOD <935'0.5 in flflF4flf RCIC SUCCESS 1

a; mai--fnr,[1]0.894'I .uhlt--ub EXTERNAL FLOOD >930'[2.00E-05]

[0.106]SUCCESSFUL

EARLY WARNING:)K::)K ,D Seq 1:)K ,D Seq 2'D Seq 3 O.00E÷00 FLOOD > 935'[0.5]RCIC SUCCESS REACTOR BLDG PROTECTED 0.894 0.89 FAILURE TO PROTECT RB 7.96E-06-9.43E-07 1.10E-06[0.106][1][0.11]Monticello

Flood SDP 930-935 Sens Freq.eta 17/3/2013

1 Page 1

EXTERNAL FLOOD >930' < 935' EARLY WARNING REACTOR BUILDING PROTECTED

RCIC/RPV & HARD PIPE VENT Prob Name SUCCESSFUL

EARLY WARNING I O.OOE+00 FLOOD <935'0.891 1 RCIC SUCCESS 0.805 D.O0E+00 5.38E-06 1.55E-06 EXTERNAL FLOOD >930'[8.90E-06]

[1]SUCCESSFUL

EARLY WARNING[0.195]I Ll=t =IPI Jt I:)K:)K ,D Seq 1:)K:)K'D Seq 2'D Seq 3 0.OOE+00 RCIC SUCCESS FLOOD > 935'[0.109]REACTOR BLDG PROTECTED 0.805[1]0.89] FAILURE TO PROTECT RB[0.195]5.95E-07 1 .68E-07 1.07E-07[0.11]Monticello

Flood SDP 930-935 Sens SPAR-H.eta

7/3/2013 Page 1

Enclosure

3 Monticello

Nuclear Generating

Plant"Monticello

Flood Protection" 11 Pages Follow

Monticello

Flood Protection

1.0 PURPOSE The purpose of this document is to evaluate the flood protection

provided at Monticello

Nuclear Generating

Plant (MNGP).Nuclear power plants are designed to meet robust design criteria, referred to as General Design Criteria (GDC); which are now codified as part of NRC regulations

in 10 CFR Part 50. The GDC have existed in various forms prior to being codified in part 50 and plant commitments

to meet the GDC (or pre-existing

requirements)

depend on the age of the plant.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 50 Appendix A, GDC. The MNGP USAR, Section 1.2, lists the Principal

Design Criteria (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 (Category

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." This evaluation

addresses

the following

aspects of flood protection

that are provided for the MNGP to meet AEC Criterion

2:* Flood Analyses -this discussion

describes

the site location, hydrology

and determination

of the maximum predicted

flood water elevations

and timing.Page 1 of 11

• Flood Mitigation

Strategy -this discussion

describes

the aspects provided to preclude the design bases flood from adversely

impacting

the site. This protection

is provided by structural

design and procedural

actions.* Flood Protection

Implementation

-this discussion

describes

the actions taken at the site to provide reasonable

assurance

that flood protection

strategy can be effectively

implemented

in a design bases flood scenario.2.0 FLOOD ANALYSIS This section describes

the site location and hydrology, and a summary of current design basis flood elevations.

Information

in this section is based on information

in the MNGP Updated Safety Analysis Report (USAR) (Reference

1); specific sections are identified

below.2.1 Site Location and Description

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.Hydrology The Mississippi

River is the major hydrologic

feature for the site. The river poses the significant

flooding source for the site. Table 1, below, summarizes

normal and flooded river flow rates and water elevations.

Table 1 Normal and Flooded River Flow Rates and Water Elevations

Mississippi

River Flow Rate (cfs) Water Elevation Condition (ft. msl)Normal 4,600 905 Maximum Recorded (1965) 51,000 916 1000 Year Flood -90,000 (1) 921 Probable Maximum 364,900 939.2 Flood 364,900 _ 939.2 (1) Estimated

using USAR Appendix G, Exhibit 8, for a water elevation

of 921 ft.Normal river level at the MNGP site is about 905 ft. msl at a distance 1.5 miles upstream, the normal river elevation

is about 910 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: Page 2 of 11

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 1000 year flood estimated

a peak stage of 921 ft. msl (USAR Section 2.4)2.2 Design Basis Flood Hazard The following

flood scenarios

are evaluated

as part of the MNGP licensing

basis [USAR Appendix G]:* Flooding in Streams and Rivers* Flooding due to Downstream

Ice Dam Build-Up A summary of the results as described

in Reference

2 for each of these flooding scenarios

is provided below; specific sections from Reference

2 are identified

with the associated

discussion.

2.2.1 Flooding in Streams and Rivers 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

11 days.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 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 initial retention

rate of zero for spring conditions, and the snowmelt contribution

to runoff, resulted in the spring storm producing

the more critical flood.Key Assumptions

Used to Determine

Design Basis Flood Hazard 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 subfreezing

temperatures

is assumed. This is followed by extreme high temperatures, and a subsequent

major spring storm. The snowmelt and Page 3 of 11

rainfall maximizes

the runoff to the river basin. This sequence of events is postulated

to produce a PMF. Additional

details regarding

key assumptions

used in the analyses are described

in USAR Appendix G.Methodology

Used to Develop Design Basis Flood Hazard The predicted

flood discharge

flow and 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. 1110-2-27, Enclosure

2, "Policies

and Procedures

Pertaining

to Determination

of Spillway Capacities

and Freeboard

Allowances

for Dams," dated August 1, 1966 (Reference

2).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 resulting

water surface elevations, a stage discharge

curve was constructed

for the site.Results The detailed analysis results are presented

in USAR Appendix G. To summarize, the analysis predicts a probable maximum discharge

of 364,900 cfs and a corresponding

peak stage of elevation

939.2 ft. msl. The flood would reach maximum river level in about 12 days after the beginning

of high temperatures, and it was estimated

the flood stage would remain above elevation

930.0 ft. msl for approximately

11 days.It is noted that the 12 day time period is for the river elevation

to reach the peak level.Other important

levels are the elevation

of the Intake Structure

(919 ft.) and Plant Grade (930 ft.). Based on USAR Appendix G Exhibits 8 and 9, water elevation

of 919 ft. could be exceeded at about the fourth day and water elevation

of 930 ft. could be exceeded at the eighth day.Page 4 of 11

2.2.2 Floods due to Ice Dam Build-Up Flooding due to backwater, usually caused by ice jams, was considered.

USAR, Appendix G, Chapter II, Page G.2-5 states that two types of flooding occur in the basin --open-water

flooding and backwater

flooding.

Flooding while open-water

conditions

prevail is caused by runoff producing

rains, or by melting snow, or by a combination

of the two. Flooding because of backwater

is usually caused by ice jams. The most serious flooding throughout

the basin has been associated

with excessive

snowmelt and rainfall.Thus, the open-water

flooding was considered

to be more limiting that the backwater flooding, and was analyzed in detail in the USAR.3.0 FLOOD MITIGATION

STRATEGY Flood protection

features and flood mitigation

procedures

are described

below. The PMF event is applicable

to all modes of operation (i.e., power operation, startup, hot shutdown, cold shutdown, and refueling).

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.

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 static/dynamic

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 static/dynamic

effects of external flooding.

Examples include external walls and penetration

seals 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 protect safety related systems, structures

and components

from the effects of external flooding.These

features are temporary

in nature, i.e., they are installed

prior to design basis external flood levels attaining

specific levels.The following

Class I and II structures

are protected

from flooding up to 939.2 ft. msl: 1. 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 Page 5 of 11

Flood preparations

at the site begin with a flood surveillance

procedure (Reference

6).During the time period of interest the surveillance

was initiated

by procedure

annually in the late winter. The procedure

is currently

performed

monthly for river level predictions

and an annual performance

includes inventory

and inspection

in addition to the river level prediction.

The purpose of this procedure

is to determine

if the potential

for plant flood exist prior to and during the spring flooding season to ensure adequate steps are taken to protect the plant if the potential

for flooding exists. The actions taken in Reference

6 are summarized

as follows:* Based on the nature of the design basis flood (heavy snow pack, thawing/freezing

cycle, coupled with heavy rain) the flood scenario is slow developing

and flood levels are generally

predictable.

Reference

6 determines

the potential

for flooding based on forecast information

from the National Weather Service and river level monitoring.

Procedure

A.6 (Reference

7), Note to Step 5.2.1, indicates

that the National Weather Service Flow Exceedance

Probability

Forecast on internet http://www.crh.noaa.qov

is used to forecast river elevations.

The information

for the St. Cloud and Anoka measurement

stations is provided on a weekly basis in terms of the probability

that the river flow will exceed a given flow rate. The prediction

information

at the website is for the next 90 days based on current conditions.

A flow discharge

curve in Reference

7 is used to determine

predicted

river water elevation

based on the predicted

flow rate. Given the conditions

that precede the PMF; i.e., snowpack with thawing and refreezing, it is reasonable

to expect that the responsible

individuals

at the plant (engineering, operations, management)

would be keenly aware of the need to monitor river water elevations

for predicted

flood conditions.

Increased monitoring

and use of the predictive

National Weather Service tools would increase the time available

to implement

flood protective

actions." Flood preparation

measures are taken as part of Reference

6 to ensure that flood protection

materials

such as sandbags, steel plates, covers and gaskets, and plugs are available.

Contact information

for vendors that would be used as part of flood preparation

activities

are confirmed

to still be valid. This contact information

includes vendors that would be involved with construction

of the bin wall and earthen levee. These actions are implemented

even if flood conditions

are not predicted.

A memorandum

of understanding

is in place with VeitVeit & Company, a local construction

firm, to provide construction

related services in the event of a site emergency, and would cover activities

such as construction

of the earthen levee." In the event that the potential

for flood conditions, dump trucks and excavators

are ensured to be available

for installation

of the levee, and a detailed flood plan is developed.

MNGP Procedure

A.6 (Reference

7), "Acts of Nature," (Part 5 -.External Flooding)stipulates

the actions to be taken in the event flood waters are predicted

to exceed elevation

918 ft. Revision 41 through Revision 45 of Procedure

A.6 (Reference

7) were in effect during the period of time from February 29, 2012 through February 15, 2013.Revision 41 was issued on February 28, 2012 and Revision 45 was issued on February 14, 2013.Page 6 of 11

The following

summarize

the actions in A.6 based on the different

predicted

flood water elevations.

• Step 5.2.8, river level is predicted

to exceed elevation

918 ft. Notification

of Unusual Event is declared.

Actions are taken to protect equipment

such as the discharge

structure

substation.

• Step 5.2.9, river level is predicted

to exceed elevation

919 ft. Actions are taken to protect the Intake Structure

from flooding.

As noted above the Intake Structure

is at elevation

919 feet.* Step 5.2.10, river level is predicted

to exceed elevation

921 ft. An Alert is declared and the plant is shutdown and cooled down to cold shutdown conditions.

Actions are taken to ensure a supply of service water is available.

• Step 5.2.11, river level is predicted

to exceed elevation

930 ft. The bin walls and earthen levee are built. Steel plates are installed

on the outside roof areas of the Intake Structure.

Yard drains and other paths that could result in a water pathway that bypasses the levee are closed. An alternate

access route to the plant is provided from higher ground in the event that the normal access road is flooded.The levee is designed to provide flood protection

up to a river elevation

of 941 ft.Backup flood protection

to the levee can be provided by closing up the various buildings

using steel plates, installing

sand bags, etc. It is noted that the levee is identified

in the procedure

as the preferred

option but, per the procedure, the backup flood protection

can be used in lieu of constructing

the levee. This is discussed

in more detail below." The remaining

Steps 5.2.12 and 5.2.13 provide additional

backup flood protection

for predicted

river elevations

above 930 feet. These are backup flood protection

measures to the levee.As described

in A.6, Step 5.2.11, Note 2, the preferred

flood protection

measure is construction

of a levee around the plant. The decision to use the levee as the preferred flood protection

is based on a recommendation

from the US Army Corps of Engineers (USACE), letter dated November 8, 2001. This USACE letter is referred to in the Bases discussion

for Part 5 of Reference

7. However, Reference

7 includes an option for providing

flood protection

in lieu of construction

of the levee. This optional flood protection

means involves installing

barriers (steel plates, etc.), sandbags, and sealing penetrations.

Resource loaded schedules

developed

in support of the A.6 procedure demonstrate

that the activities

were achievable

in the time required.

Recent simulations

and demonstrations

confirm the construction

time for the bin wall, steel plate installation

and sand bagging.As shown on Figure 13.10 of Reference

7, construction

of the levee includes construction

of a bin wall to the immediate

east and west of the Intake Structure.

The bin wall was added as part of Revision 41 to A.6 on February 28, 2012. Prior to Revision 41, the levee was made entirely of earthen material.

The decision to use the bin wall was based on an analysis performed

by Short Elliot Hendrickson, Inc., (SEH) (Reference

8).As part of this same change, the configuration

of the levee was modified from a ring levee entirely around the plant to a horseshoe

design that ties into areas of the site that Page 7 of 11

are above the peak PMF water elevation.

The recommendation

to use the bin wall was made as part of Reference

8 after considering

various options for the tie to the Intake Structure.

Reference

8 included the following

recommendations:

• Secure a borrow source of levee fill within 15 minutes of the site or purchase and store on site.* Purchase bin wall materials, assemble in modules to reduce installation

time frame, and store on site.The deficiencies

identified

in Reference

5 have subsequently

been addressed.

In addition to the noted deficiencies, other areas were also identified

for improvement

to the plant and procedures.

All of these areas for improvement

were entered into the plant corrective

action system.Additional

actions have been implemented

to further improve the flood protection

at the site. These additional

actions are summarized

below:* Bin wall materials

have been procured and are now stored on site. The procurement

of the bin walls took approximately

eight weeks; however, this was treated as a normal procurement.

The bin walls were supplied by Contech Engineered

Solutions.

Based on discussions

with Contech Engineered

Solutions it is estimated

that the bin wall sections could be provided in approximately

14 days in an emergency

situation.

As discussed

above, in the event that the bin walls cannot be constructed

due to unavailability

of materials, flood protection

could still be provided as stipulated

in the procedure

using the sandbag and flood barrier option. This option is independent

of the levee and bin walls.* Levee materials

have been procured and are now stored on site. Levee materials were delivered

to the site within four 12 hour1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> shifts.* External flood surveillance

procedure, 1478, (Reference

6) has been improved to increase the frequency

of river level monitoring

during potential

flooding conditions.

The additional

river level monitoring

ensures timely plant preparation

for a potential

flood. The increased

river level monitoring

serves to provide earlier warning of predicted

flood levels and increases

available

time to implement protective

actions.* Procedure

A.6 (Reference

7) has been revised to improve the procedure

clarity, remove unnecessary

steps, and ensure completeness

of protective

actions." Detailed work instructions

have been developed

to implement

actions in A.6.The work instructions

provide the technical

detail necessary

to implement

the required action. Pre-staging

the work instructions

prior to the event reduces the required time frames to implement

the required actions in A.6.* Monticello

conducted

a self-assessment

of the site flood protection

response to take an additional

critical review. The self assessment

was performed

by a team of Xcel and contract professionals

experienced

in areas of flood protection.

Page 8 of 11

Specific areas for improvement

were identified

during the self assessment

and were entered in the corrective

action program and are being actively addressed.

4.0 FLOOD MITIGATION

STRATEGY -FURTHER DEMONSTRATIONS

Table top walkthroughs

of procedure

A.6 have been performed

to demonstrate

feasibility

of performance

of the required actions. A detailed schedule is developed

for the actions in A.6 using input from the site departments

who would execute the actions. The schedule shows actions to be performed, time frames, and sequencing, and demonstrates

that the actions can be completed

within the available

time period.Detailed work instructions

have been developed

to implement

the actions in A.6. Pre-staging of the work instructions

reduces the overall time to perform the tasks by removing the time associated

with work planning, identifies

that materials

that may be needed to accomplish

the work, and identifies

any potential

interferences

or impediments

to completing

the required task ahead of time.As described

in Section 3.0, above, the materials

to construct

the bin wall sections and the earthen levee have been procured and are stored on site. As previously

discussed, a memorandum

of understanding (MOU) is in place with VeitVeit & Company, a local construction

firm, to provide equipment

and services for construction

of the bin wall and earthen levee.Reasonable

simulation

of construction

of several of the actions believed to be more time consuming

was performed

in order to demonstrate

that the actions could be performed within the available

time frame. Specific actions examined were construction

and filling of the bin walls, construction

of the steel plates around the roof of the Intake Structure, and filling of sandbags.

The results from these reasonable

simulations

are summarized

below.* Construction

of bin walls. For the reasonable

simulation, approximately

5% of the total bin wall sections were constructed

and filled. The simulation

was contracted

to Veit to add realism per our MOU and exercise the mobilization

of personnel.

The reasonable

simulation

took 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> for one crew to fully construct

and fill.Based on using six crews, available

per our MOU, to construct

and fill the bin walls during implementation

of procedure

A.6, this would indicate that the entire bin wall sections could be fully constructed

within 1.4 days. Accounting

for issues such as excavation, inclement

weather, security concerns, coordination, total construction

time of four days is reasonable.

• Steel plates around roof of Intake Structure.

As part of procedure

A.6 steel plates are attached to the wall of the Intake Structure

with anchors and the seams between the plates welded to form part of the flood protection

barrier. For the reasonable

simulation, approximately

20% of the plates were installed

on a mock-up. The reasonable

simulation

took 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> and 11 minutes. Based on one welder all of the plates could be installed

within 16 hours1.851852e-4 days <br />0.00444 hours <br />2.645503e-5 weeks <br />6.088e-6 months <br />. Using two welders would reduce this time to 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />. Additional

welders would reduce this time even more. This time period is much less than the available

time and provides margin for working in inclement

weather conditions.

Page 9 of 11

Sandbagging.

Per procedure

A.6, approximately

100,000 sandbags are filled.Sandbags are used in several steps in A.6 to seal openings, provide backup flood protection.

Sandbags are critical in the event that the sandbag and flood barrier option were implemented

in A.6 in lieu of the levee option. Reasonable

simulation

indicates

that 600 sandbags can be filled per hour using one machine and 8 people. Go-Baggers

are a manual bagging apparatus

with which an individual

can fill 55 bags an hour. With one machine and 20 people working around the clock, the 100,000 sandbags can be filled in 2 1/2 days. Reasonable

simulation

also showed that a steel double door can be sandbagged

by five personnel

in 34 minutes. Furthermore, it was shown that laying lumber and sandbagging

1 EDG room can be accomplished

by 14 personnel

in four hours.In the three cases discussed

above, the reasonable

simulation

concluded

that the required actions can be accomplished

within the available

time frame.5.0 CONCLUSIONS

The following

conclusions

are drawn from the above discussion:

• The postulated

flood scenario for the MNGP is considered

to be very conservative.

The methodology

employed provides conservative

results. This can be seen from the comparison

of river flow rates and water elevations

in Table 1 in Section 2.1, above.* The flood is a relatively

slow developing

evolution

that allows time for plant staff to monitor, predict and implement

appropriate

actions to provide the required flood protection.

• The flood mitigation

procedure

clearly identifies

actions for plant staff to implement

to provide the required flood protection.

• In the event that the levee were not able to be constructed

due to not having the bin wall materials

available, the procedure

provides an optional approach to implement

flood protection

without relying on the levee and bin wall system.Table top review of the steps to implement

this optional means of flood protection

demonstrated

that the protection

could be provided within the available

time.* Subsequently

actions have been taken to procure the bin wall and levee materials.

Reasonable

simulation

has demonstrated

that the levee and bin wall system can be installed

well within the available

time.Page 10 of 11

6.0 REFERENCES

1. Monticello

Nuclear Generating

Plant, Updated Safety Analysis Report (USAR), Revision 29.2. Department

of the Army, Office of the Chief of Engineers, the U.S. Army Corps of Engineers, Engineer Circular No. 1110-2-27, Enclosure

2, "Policies

and Procedures

Pertaining

to Determination

of Spillway Capacities

and Freeboard

Allowances

for Dams," dated August 1, 1966.3. NRC Letter to Licensees, dated March 12,2012, "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. ML 12053A340).

4. NEI 12-07, Revision O-A, "Guidelines

for Performing

Verification

Walkdowns

of Plant Flood Protection

Features," dated May 2012 (ADAMS Accession

No. ML 12173A215).

5. Xcel Energy Letter L-MT-1 2-097, "MNGP Final Response to NRC Request for Information

Pursuant to 10 CFR 50.54(f) Regarding

the Flooding Aspects of Recommendation

2.3 of the Near-Term

Task Force Review of Insights from the Fukushima

Dai-ichi Accident," dated November 27, 2012.6. Procedure

1478, "External

Flood Surveillance," Revision 7. [Revision

7 is the procedure revision currently

in effect. During 2012, Revisions

4 through 6 was in effect and the procedure

was titled "Annual Flood Surveillance."]

7. Procedure

A.6, "Acts of Nature," Revision 46. [Revision

46 is the procedure

revision currently

in effect. When used, previous revision numbers are identified

in the text.]8. Xcel Contract No. 38398, SEH No. MONNE 117980, "Monticello

Nuclear Generation

Plant, External Flooding Plan Update: Alternative

Analysis and Final Design Report," dated January 5, 2012.Page 11 of 11

Enclosure

4 Monticello

Nuclear Generating

Plant"Annual Exceedance

Probability

Estimates

for Mississippi

River Stages at the Monticello

Nuclear Generating

Plant based on At-site Data for Spring and Summer Annual Peak Floods" 12 Pages Follow

Annual Exceedance

Probability

Estimates

for Mississippi

River Stages at the Monticello

Nuclear Generating

Plant based on At-site Data for Spring and Summer Annual Peak Floods David S. Bowles and Sanjay S. Chauhan RAC Engineers

& Economists

June 28, 2013 Purpose: To estimate the annual exceedance

probabilities (AEPs) for Mississippi

River Stages 917, 930 and 935 ft.NGVD 29 at the Monticello

Nuclear Generating

Plant (MNGP) using at-site data for spring and summer floods.These estimates

are intended to improve on the previous annual peak flood estimates

that were submitted

on April 8, 2013. The previous estimates

were was based on an at-site flood frequency

curve constructed

using a) a conservatively

assigned AEP to the Harza spring PMF, and b) at-site flood frequency

estimates

obtained from a drainage-area

weighted interpolation

between provisional

USGS annual peak flood frequency

estimates

for the upstream and downstream

Mississippi

River gages at St.Cloud and Elk River, respectively.

Given more time, we recommend

that a Monte Carlo rainfall-runoff

approach should be used to develop estimates

of extreme flood frequencies

to make use of regional precipitation

data and a more physically-based

transformation

of rainfall to runoff, including

snow melt and explicit consideration

of uncertainties.

Available

Information:

Observed mean daily flows at the following

locations:

1) Station Number 05270700 Mississippi

River at St. Cloud, MN with a period of record from 1989 to 2012.2) Station Number 05275500 Mississippi

River at Elk River, MN with a period of record from 1916 to 1969.3) Monticello

Nuclear Generating

Plant (at-site)

with a period of record from 1970 to 2012.Flood frequency

estimates

of annual peak discharges:

4) Provisional

2013 USGS annual peak discharge

flood frequency

analyses with estimates

of AEPs ranging from 1 in 1.005 to 1 in 500 based on maximum daily flow rates for the annual peak flows: 1

a. Station Number 05270700 Mississippi

River at St. Cloud, MN with drainage area of 13,320 sq. miles.b. Station Number 05275500 Mississippi

River at Elk River, MN with drainage area of 14,500 sq. miles.Probable maximum flood (PMF) peak discharge

and stage estimates:

5) Harza 1969 (spring) PMF peak discharge

and river stage at the Monticello

Nuclear Generating

Plant -1912 Datum.6) Bechtel 20121 spring and summer PMF peak discharges

and river stages at the Monticello

Nuclear Generating

Plant -NAVD88 Datum.Discharge

rating relationships:

7) Harza 1969 relationship

between river stage (1912 Datum) and river discharge (cubic feet per second, cfs) over the range 26,000 to 437,000 cfs.8) Ops manual equation between river discharge (cubic feet per second, cfs) up to 4,000 cfs and river stage (NGVD 29 Datum): Q = 122(Stage

-901)2.2.Datum conversions

for river stages: 9) NGVD 29 Datum = 1912 Datum -0.36 ft.10) NGVD 29 Datum = NAVD 88 Datum -0.4 ft.Procedure:

The following

two approaches

were examined for developing

improved at-site estimates

of annual exceedance

probabilities (AEPs) for the spring and summer annual floods in the Mississippi

River at the MNGP: 1) Drainage-area

weighted interpolation

of flood frequency

estimates

for the upstream and downstream

USGS gages: Similar to the April 8, 2013 approach, an at-site flood frequency

curve was obtained from a drainage-area

weighted interpolation

between flood frequency

estimates for the upstream and downstream

Mississippi

River gages at St. Cloud and Elk River, respectively.

However, this revised approach was conducted

separately

for spring and summer annual peak floods and it did not conservatively

assign an AEP to the Harza PMF as was done in the April 8, 2013 approach.

Instead the flood frequency

curve was extrapolated

to extreme floods thus providing

estimate of the AEPs for the spring and summer PMF peak flow estimates and for the three elevations

of interest.1 The report, Bechtel 2012 spring and summer PMF peak discharges

and river stages at the Monticello

Nuclear Generating

Plant -NAVD88 Datum, has been provided to NSPM. This study provides bounding estimates

to site peak flood elevations

applicable

to the development

of annual exceedance

probabilities

at the Monticello

Nuclear Generating

Plant.2

2) Flood frequency

analysis based on at-site flow data: A flood frequency

analysis was conducted on the available

at-site streamflow

data for the period 1970 to 2012 with extrapolation

to extreme floods. This provided estimate of the AEPs for the three elevations

of interest and for the PMF peak flow estimates

for spring and summer annual peak floods.Both of the above approaches

included estimating

separate flood frequency

relationships

for spring and summer annual peak floods. Data for estimating

these relationships

were obtained using the following definitions

of spring and summer floods based on discussions

in the Hydrologic

Atlas of Minnesota (State of Minnesota

1959) and examination

of the flow records: 1) Spring annual peak floods generally

peaked in the period March to May, but if it was clear from examination

of the hydrograph

that a snow melt flood event peaked in June then that peak was used.2) Summer annual peak floods generally

peaked in the June to early October period, but flood peaks occurring

in June, which were clearly associated

with snow melt events, were excluded as mentioned

in 1). Since the recession

limb of the annual snow melt hydrograph

extends through the summer, the peak flow rates for summer floods, which are associated

with convective

storms, are dependent

to some degree on the magnitude

of flow on this recession

limb at the time of the summer flood.The two approaches

are discussed

in more detail below.Approach 1): Drainage-area

weighted interpolation

of flood frequency

estimates

for the upstream and downstream

USGS gages The provisional

USGS annual peak flow flood frequency

estimates

for the Mississippi

River gages at St.Cloud and Elk River were verified using USGS flood frequency

software following

Bulletin #17B flood frequency

analysis procedures (USGS 1982). The following

softwares

were applied to the maximum daily annual peak streamflow

data assembled

by the USGS to verify their results: 1) PeakFQ: Bulletin #17B procedure

based on method of moments parameter

estimation

for a Log Pearson Type 3 probability

distribution (Flynn et al 2006)2) PeakfqSA:

The more efficient

Expected Moments Algorithm (EMA) applied to the Bulletin #17B methodology (Cohn 2012)Following

the USGS provisional

analysis, the Bulletin #17B (PeakFQ) software was applied to the St Cloud gage and the EMA (PeakfqSA)

software was applied to the Elk River gage for the verification

step.Separate flood frequency

analyses were then conducted

for spring and summer annual peak flow data at the St. Cloud and Elk River USGS gages. The maximum daily annual peak streamflow

data were assembled

by the USGS and provided with their provisional

flood frequency

analyses.

These data comprised

a mixture of spring and summer floods. These data were separated

into spring and summer floods and mean daily peak flow data were obtained from USGS flow records at both gages for those cases that were not covered by the maximum daily annual peak streamflow

data assembled

by the 3

USGS. An additional

year (2012) of data was added for the St Cloud gage. Maximum daily annual peak flows were estimated

from mean daily annual peak flows for those data not included in the USGS provisional

analyses using regression

relationships

established

between maximum daily annual peak flow data and mean daily annual peak flow data for spring and summer flows for each gage.The PeakfqSA software containing

improved EMA parameter

estimation (Stedinger

2013) was applied to both spring and summer flood data for both gages. No outliers were identified.

The EMA software provided AEP estimates

from I in 1.0001 to I in 10,000. Estimates

of annual peak discharge

on the Mississippi

River at the MNGP were then obtained based on linear interpolations

between various frequency (AEP) estimates

developed

for the St Cloud and Elk River gages as a function of drainage area with the drainage area at the MNGP being 14,071 sq. miles. This interpolation

the procedure

is the same as developed

for the April 2013 AEP estimates.

The at-site annual peak discharge

estimates

were converted

to at-site river stages using a combination

of the Harza and Ops Manual equation rating curves shown in Figure 1.Examination

of the relationship

between flood estimates

for various AEPs and drainage area shown in Figure 2 showed an inconsistent

relationship

that was increasing

or decreasing

with drainage area. As a result we have not relied on these estimates

in favor of using the flood frequency

estimates

obtained from analysis of at-site data in the second approach.947 942 937* 932 0J S927 _______.5922 __________

0J S917 912 907 1 1 _________9021 100 1,000 10,000 100,000 1,000,000 Discharge

In cfs-Ops Man Eqn, Q= 122(Stage-901)^2.2

-Harza Discharge

Rating -- Transition

-.Final curve Figure 1. Combined Harza and Ops Manual Equation stage-discharge

rating curve 4

80,000 70,000 60,000 50,000 0 40,000 E.30,000 20,000 10,000 Interpolation

of at-site quantiles-TF U-------- ----- ----*0.995-0.99-0.95-0.9.--0.6667ý0.5--*-0.4292-o-0.2-0.04-0.02-.--0.01-0-0.005-4-0.002-MNGS 5,000 U 13,000 13,500 14,000 Drainage Area (sq. miles)14,600 I Figure 2. Relationships

between flood estimates

for various AEPs and drainage area for Approach 1 Approach 2): Flood frequency

analysis based on at-site flow data The second approach is based on extrapolation

of flood frequency

relationships

developed

from at-site flow data. The mean daily annual peak stages were obtained for spring and summer annual peak floods following

the process summarized

above. Since only single observations

have been recorded for each day it was not possible to obtain maximum daily annual peak stages. The daily annual peak stages were converted

to daily annual peak flows for spring and summer floods using the combined rating curve shown in Figure 1. The EMA (PeakfqSA)

software was applied to estimate the flood frequency relationships

for spring and summer annual peak floods. No outliers were identified

for the spring season, but one low outlier (2,416 cuffs) was identified

for the summer season using the Multiple Grubbs-Beck

Test) low outlier identification

method. The EMA software provided AEP estimates

for the range 1 in 1.0001 to 1 in 10,000.Annual Exceedance

Probability

Estimates:

Figures 3 and 4 show the resulting

flood frequency

estimates

for the spring and summer annual peak floods obtained from the second approach.

The annual peak discharge

is plotted on a Log scale and AEPs are plotted on a z-variate

scale (corresponding

to a Normal probability

distribution).

In addition to 5

Monticello

NGS -Spring 1,000,000 B el 2012 PMF estim te an--- ----a--T9. nbrPes-Tma

--e .--., e.0l vafion 93S El, -atlon 930 100,000 ...... ...-, -..-'":! ...

""h...=-- -- ~ ~... :...........

10,000 v-Exce dance Probability

1E I 1E-1 1E-2 E-3 1E-4 iE-5 1E-6 1E-7 1E-8 1 9 1,000 .I I I" I 1- 1-4.0 -3.0 -2.0 -1.0 0.0 1.0 2.0 3.0 4.0 5.0 6.0 z-variate Figure 3. Spring Annual Peak Flood Frequency (approximate

mean shown by black dashed line)6

Monticello

NGS -Summer 1,000,000 N 0 2 4)4)4)a.100,000 10,000 1,000-4.0 -310 -2.0 -1.0 0.0 1.0 2.0 3.0 4.0 5.0 6.0 z-variate Figure 4. Summer Annual Peak Flood Frequency (approximate

mean shown by black dashed line)7

providing

median (5 0 th percentile)

and approximate

mean 2 estimates, the 20% (4 0th and 6 0 th percentiles), 40% (3 0 th and 7 0 th percentiles), 60% (2 0 th and 80th percentiles), 80% (1 0 th and 9 0 th percentiles), and 90% (5 th and 9 5 th percentiles)

confidence

interval estimates

are provided with linear extrapolation

to smaller AEPs beyond 1 in 10,000. The site elevations

of 917, 930 and 935 are shown by horizontal

lines based on the NGVD 29 datum matching the datum used on the site drawings.

Also the Harza and Bechtel PMF estimates

are shown by horizontal

lines corresponding

to peak elevations

for these events.It is noted above that only single daily river stage observations

have been recorded at site and therefore it was not possible to obtain maximum daily annual peak stages. Since the difference

between mean daily and maximum daily peak stages decreases

with smaller AEPs, it is likely that the flood frequency relationships

are slightly steeper than shown. This effect would tend to make AEP estimates

for extreme flows slightly conservative (i.e. slightly larger) than of this effect were removed.Tables 1 and 2 contain numerical

AEP estimates

for spring and summer annual peak floods, respectively, for river stages 917, 930 and 935 ft. NGVD 29 for the median (5 0th percentile)

and approximate

mean, and for various confidence

percentiles.

Table 1. Spring Annual Peak Flood Frequency

Estimates Elevation

917 9 5 th I ge 1 8 4th 1 0 th I 7 0 th I 60 I Median 5 0 e 5 th Approx Mean AEP Estimates

3.4E-02 2.5E-02 2.0E-02 1.7E-02 1.2E-02 8.9E-03 6.3E-03 5.9E-07 7.9E-03 i in Tyears 29 40 51 59 82 112 158 1,680,000

127 Elevation

930 95t' 90 84th 80' 70 60h Median 50 5t Approx Mean AEP Estimates

7.OE-06 7.6E-07 7.5E-08 1.7E-08 < 1E-9 < 1E-9 < 1E-9 < 1E-9 < 1E-9 1inTyears

143,0001 1,320,0001

13,400,0001

60,500,0001

>1E+9 I >1E+9 [ >1E+9 I >1E+9 [ >1E+9 I _Elevation

935 F-9 90 o 84th 806 70& 60' Median 506' 51 Approx Mean AEP Estimates

4.3E-07 2.OE-08 < 1E-9 < 1E-9 < 1E-9 < 1E-9 < 1E-9 < 1E-9 < 1E-9 1 in T years 2,350,000

51,100,000

>1E+9 >1E+9 >1E+9 >1E+9 >1E+9 >1E+9 >1E+9 Table 2. Summer Annual Peak Flood Frequency

Estimates___Elevation

917 9Sth 90t 84th 80 th 70 th 60d Median 50th 5th Approx Mean AEP Estimates

1.9E-02 1.3E-02 8.8E-03 7.2E-03 4.4E-03 2.8E-03 1.7E-03 8.5E-07 3.OE-03 1 in Tyears 52 79 113 140 225 358 590 1,180,000

328_ _Elevation

930_95_ 9 0 go 84th 80eh 7 0 th 6 0 e Median 506h 5 th Approx Mean AEP Estimates

2.1E-04 4.3E-05 8.8E-06 3.1E-06 2.4E-07 1.5E-08 < 1E-9 < 1E-9 1.6E-06 1in Tyears 4,7201 23,4001 11,00 324,000 4,160,000

65,100,000

>1E+9 >1E+9 641,000 I-_ Elevation

935 95h 90 o 841 80h 70 60'h Median 50' 5 h Approx Mean AEP Estimates

6.1E-05 7.9E-06 9.7E-07 2.5E-07 8.9E-09 < 1E-9 < 1E-9 < 1E-9 2.OE-07 I in T years 16,500 127,000 1,030,000

4,000,000

112,000,000

>1E+9 >1E+9 >1E+9 1 4,930,000 2 The approximate

mean estimates

were obtained by weighting

the various percentile

estimates

by their respective

intervals

of probability

that each represents.

For example, the 6 0 th percentile

represents

the interval between the mid-points

of the 5 0 th -6 0 th and 6 0 th -7 0 th percetile

intervals

and hence is weighted by the difference

between the percentiles

associated

with the mid-points

of these two intervals, i.e. 0.65-0.55

= 0.10.8

The following

is a summary of the median estimates

and ranges (Upper -9 5 th percentile

and Lower -5 th percentile)

of the AEP estimates

for the river stages of 917, 930 and 935 ft. NGVD 29 at the Monticello

Nuclear Generating

Plant for spring and summer annual peak floods and for the Harza and Bechtel PMF estimates.

The April 8, 2013 spring estimates

are shown in italics for comparison.

The comparison

shows that these estimate were conservative

relative to those obtained using the second approach.Spring Floods: Elevation

917 ft. NGVD 29:* Upper (9 5 th): 3.4E-02 (1 in 29/year) 4.OE-02 (1 in 25/year)" Median (5 0 th): 6.3E-03 (1 in 158 /year) 7.2E-03 (1 in 140/year)* Lower (5 th): 5.9E-07 (1 in 1,680,000

/year) 9.5E-04 (1 in 1,100/year)

Elevation

930 ft. NGVD 29:* Upper (95th): 7.OE-06 (1 in 143,000 /year) 1.6E-04 (1 in 6,300/year)

• Median (5 0 th): < 1E-9 (1 in >1E+9 /year) 1.6E-05 (1 in 61,000/year)

• Lower (5th): < 1E-9 (1 in >1E+9 /year) 2.2E-06 (1 in 460,000/year)

Elevation

935 ft. NGVD 29:* Upper (95th): 4.3E-07 (1 in 2,350,000

/year) 3.OE-05 (1 in 33,000/year)

• Median (50th): <1E-9 (1 in >1E+9 /year) 3.1E-06 (1 in 330,000/year)

• Lower (5th): <1E-9 (1 in >1E+9 /year) 3.4E-07 (1 in 2,900,000/year)

The Harza Spring PMF AEP estimates

are shown below with the April 8, 2013 AEPs assigned to the Harza (spring) PMF shown in italics for comparison.

• Upper (9 5th): 5.9E-08 (1 in 16,900,000)

1 in 10,000,000

• Median (5 0 th): < 1E-9 (1 in >1E+9 /year) 1 in 1,000,000" Lower (5 h): <1E-9 (1 in >1E+9 /year) 1 in 100,000 The estimates

of AEPs assigned to the Harza PMF in the April 8, 2013 work are therefore

confirmed

to be conservative (i.e. larger than now estimated).

The AEP Bechtel spring PMF estimates

are shown below: " Upper (9 5 th): 1.8E-08 (1 in 54,500,000)

• Median (5 0 th): < 1E-9 (1 in >1E+9 /year)* Lower (5 th): < 1E-9 (1 in >1E+9 /year)9

Summer Floods: Elevation

917 ft. NGVD 29:* Upper (9 5 th):* Median (5 0 th):* Lower (5 th): 1.9.4E-02

(1 in 52 /year)1.7E-03 (1 in 590 /year)8.5E-07 (1 in 1,180,000

/year)Elevation

930 ft. NGVD 29:* Upper (9 5 th):* Median (5 0 th): " Lower (5 th): 2.1E-04 (1 in 4,720 /year)< 1E-9 (1 in >1E+9 /year)<1E-9 (in >1E+9/year)

Elevation

935 ft. NGVD 29: 0 0 0 Upper (9 5 th): Median (5 0th): Lower (5 th): 6.1E-05 (1 in 16,500 /year)< 1E-9 (1 in >1E+9 /year)< 1E-9 (1 in >1E+9/year)

The AEP Bechtel summer PMF estimates

are shown below:* Upper (9 5 th):* Median (5 0th):* Lower (5 th): 5.7E-04 (1 in 1,750/year)

3.3E-08 (1 in 29,900,000

/year)< 1E-9 (1 in >1E+9/year)

The second approach used to develop these revised AEP estimates

is preferred

to the initial approach used to develop our April 2013 estimates

for the following

reasons: 1) It separates

the spring and summer flood events.2) It relies on at-site date rather than a drainage-area

weighted interpolation

of AEP estimates

at upstream and downstream

Mississippi

River USGS gages.3) It does not rely on an assignment

of an AEPtothe PMF.A graphical

comparison

of the April 2013 and the current estimates

is presented

in Figure 5. It indicates that the April 2013 AEP estimates

are likely overly conservative

as a result of the assignments

of the AEPs to the Harza PMF.Figure 5 is similar to Figure 3 but includes the USNRC (2013) AEP estimates:

9.37E-05 for Elevation

930 and 2.72E-05 for Elevation

935 (based on 6.65E-05/year

for Elevation

930-935).

The NRC estimates exceed our current 9 5 th percentile

estimates

but are very similar to our April 2013 9 5 th percentile

estimates, which were based on assigning

an AEP of 1E-5 to the Harza PMF. According

to USNRC (2013)their estimates

are based on flood frequency

estimates

from the Monticello

USAR and IPEEE but we are not clear about the origin of those estimates

or the curve fitting approach that was used by the USNRC (2013). Therefore

it is not possible to make a more informed comparison

with our estimates;

although it 10

Monticello

NGS -Spring 1,000,000 z 9 9L aJ tU.X 100,000 10,000 1,000-4.0-3.0 -2.0 -1.0 0.0 1.0 2.0 3.0 4.0 5.0 z-variate-April 2013 Best Estimate --April 2013 Upper Estimate --April 2013 Lower Estimate * NRC Estimates

-Approx Mean 6.0 Figure 5. Comparison

of the current Spring Annual Peak Flood Frequency

with the April 2013 estimates

and the NRC (2013) estimates 11

would appear that our estimates

rely on more recent site-specific

data than the NRC had available.

In addition they use the Bulletin #17B flood frequency

approach, which is the standard for flood frequency analysis in the US. We also used the improved EMA parameter

estimation

approach that will be included in the revision of the Bulletin #17B procedure

that has been drafted.However, we recommend

that a Monte Carlo rainfall-runoff

approach be considered

to develop estimates

of extreme flood frequencies

with explicit consideration

of uncertainties

in the future. This approach can be expected to provide improved estimates

based on the use of regional rainfall analysis, and a more physics-based

representation

of the rainfall-runoff (including

snow melt) processes

for extreme floods than is associated

with the current extrapolation

approach.References

Cohn, T. 2012. User Manual for Program PeakfqSA Flood-Frequency

Analysis with the Expected Moments Algorithm

DRAFT. September.

Flynn, K.M., Kirby, W.H., and Hummel, P.R., 2006, User's Manual for Program PeakFQ Annual Flood-Frequency

Analysis Using Bulletin 17B Guidelines:

U.S. Geological

Survey, Techniques

and Methods Book 4, Chapter B4; 42 pgs.State of Minnesota.

1959. Hydrologic

Atlas of Minnesota.

Davison of Water, Department

of Conservation, State of Minnesota.

Stedinger, J.R. V. Griffis, A. Veilleux, E. Martins, and T. Cohn. 2013. Extreme Flood Frequency

Analysis: Concepts, Philosophy

and Strategies.

Proceedings

of the "Workshop

on Probabilistic

Flood Hazard Assessment (PFHA)" sponsored

by the U.S. Nuclear Regulatory

Commission's

Offices of Nuclear Regulatory

Research, Nuclear Reactor Regulation

and New Reactors in cooperation

with U.S. Department

of Energy, Federal Energy Regulatory

Commission, U.S. Army Corps of Engineers, Bureau of Reclamation

and U.S. Geological

Survey organized.

Rockville, Maryland.January 29 -31.USGS (US Geological

Survey). 1982. Guidelines

for Determining

Flood Flow Frequency.

Bulletin #17B, Hydrology

Subcommittee, Interagency

Advisory Committee

on Water Data, Office of Water data Coordination.

USNRC (U.S. Nuclear Regulatory

Commission).

2013. Monticello

Nuclear Generating

Plant, NRC Inspection

Report 05000263/2013008;

Preliminary

Yellow Finding.12

Enclosure

5 Monticello

Nuclear Generating

Plant"Stakeholder

Outreach" I Page Follows

Stakeholder

Outreach NSPM hosted an open house on Thursday, June 6, from 4 p.m.-8 p.m. to share information

with its community

neighbors

on operations

and preparedness

to handle potential

emergencies

and how we would respond to flooding, earthquakes

and other unforeseen

challenges.

The Site employed numerous methods to publicize

the event: personal, direct invitations

to community

leaders, a full page ad was purchased

in weekly newspapers, a news release was distributed

to local media and 14,000 postcards

were mailed to neighbors

in surrounding

communities.

The outreach event had full corporate

support and the Xcel Energy Chairman, President

and CEO, and the Chief Nuclear Officer attended, as well as numerous senior members of the corporate nuclear staff. The Monticello

Site Vice President

and Plant Manager were also joined by the site's senior leadership

team at the event.A total of 515 persons from Monticello

and surrounding

communities

attended the event at the Monticello

Training Center.The key message presented

to visitors was that safety and security at the NSPM nuclear generating

plants are top priorities

for Xcel Energy. Further, that we understand

the NRC's increased

scrutiny of safety and flood preparedness

at the nation's nuclear power plants in the wake of events such as 9/11 and Fukushima

Daiichi. The Monticello

Flood Protection

Strategy was identified

and explained

to demonstrate

that the site is designed to withstand

a hypothetical

flood beyond anything reported in the Monticello

area. The broad underlying

key messages were reinforced

and manifest in specific subject items such as: B.5.b Pump/Electrical

Generator/Trailer, Portable Emergency

Response Equipment, Backup Power Sources including

description

of backups to the backup (Battery Systems) and the continual

focus on improving

emergency

preparedness

capabilities.

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