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{{Adams
#REDIRECT [[L-MT-13-062, Response to an Apparent Violation in NRC Inspection Report 05000263/2013008 (EA-13-096)]]
| number = ML13233A068
| issue date = 07/11/2013
| title = Monticello Nuclear Generating Plant - Response to an Apparent Violation in NRC Inspection Report 05000263/2013008 (EA-13-096)
| author name = Schimmel M A
| author affiliation = Northern States Power Co, Xcel Energy
| addressee name =
| addressee affiliation = NRC/Document Control Desk, NRC/RGN-III
| docket = 05000263
| license number = DPR-022
| contact person =
| case reference number = EA-13-096, L-MT-13-062
| document report number = IR-13-008
| document type = Letter, Licensee Response to Enforcement Action, Licensee Response to Notice of Violation
| page count = 99
}}
See also: [[followed by::IR 05000263/2013008]]
 
=Text=
{{#Wiki_filter: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 hours 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 hours 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 hours.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 hours 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 hours 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- -&#xfd;.'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 S&#xfd;Procedure:'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
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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.Type&#xfd;. 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. .&#xfd;.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 hours.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 hours 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 hours following
a SBO (flooding
>930'). Core temperature
reaches 1800 degrees F at 15 hours 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 hours -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 hours 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&sect;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.
~Critical&#xfd;
'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 11&#xfd;r 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 hours following
a SBO (flooding
>930'). Core temperature
reaches 1800 degrees F at 15 hours 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 hours -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 hours 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&#xf7;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 hour 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 hours 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 hours and 11 minutes. Based on one welder all of the plates could be installed
within 16 hours. Using two welders would reduce this time to 8 hours. 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.--0.6667&#xfd;0.5--*-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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