ML17096A443

Audit Report Relating to the Flood Hazard Reevaluation Report

ML17096A443
Person / Time
Site:	Monticello
Issue date:	04/18/2017
From:	Lauren Gibson Japan Lessons-Learned Division
To:	Gardner P Northern States Power Company, Minnesota
Gibson L, NRR/JLD, 415-1056
References
CAC MF7712
Download: ML17096A443 (12)

Text

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 Mr. Peter A. Gardner Site Vice President Northern States Power Company -

Minnesota Monticello Nuclear Generating Plant 2807 West County Road 75 Monticello, MN 55362-9637 April 18, 2017

SUBJECT:

NUCLEAR REGULATORY COMMISSION REPORT FOR THE AUDIT OF NORTHERN STATES POWER COMPANY'S FLOOD HAZARD REEVALUATION REPORT SUBMITTAL RELATING TO THE NEAR-TERM TASK FORCE RECOMMENDATION 2.1-FLOODING FOR MONTICELLO NUCLEAR GENERATING PLANT (CAC NO. MF7712)

Dear Mr. Gardner:

The purpose of this letter is to provide you with the final audit report which summarizes and documents the U.S. Nuclear Regulatory Commission's (NRC's) regulatory audit of the Flood Hazard Reevaluation Report (FHRR) submitted by Northern States Power Company, a Minnesota corporation (NSPM, the licensee), doing business as Xcel Energy, related to Monticello Nuclear Generating Plant (Monticello). The FHRR was submitted as part of implementing lessons learned from the 2011 accident at the Fukushima Dai-ichi nuclear plant.

Specifically, the FHRR documents the results of the flood hazard reevaluation being completed as part of NRC Near-Term Task Force Recommendation 2.1.

By letter dated June 7, 2015 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML16152A125), the NRC informed you of the staff's plan to conduct a regulatory audit of NSPM's FHRR submittal for Monticello. The audit was intended to support the NRC staff's review of the licensee's FHRR and the subsequent issuance of a staff assessment documenting the staff's review. The audit was conducted remotely during the months of June 2016 - March 2017, with a teleconference on August 18, 2016. The audit was performed consistent with NRC Office of Nuclear Reactor Regulation Office Instruction LIC-111,

"Regulatory Audits," dated December 29, 2008 (ADAMS Accession No. ML082900195). The details of the audit were discussed with Ms. Lynne Gunderson of your staff.

If you have any questions, please contact me at (301) 415-1056 or by e-mail at Lauren.Gibson@nrc.gov.

Docket No. 50-263

Enclosure:

Audit Report cc w/encl: Distribution via Listserv Sincerely,

~40)

Lauren K. Gibson, Project Manager Hazards Management Branch Japan Lessons-Learned Division Office of Nuclear Reactor Regulation

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 AUDIT REPORT BY THE OFFICE OF NUCLEAR REACTOR REGULATION FOR THE AUDIT OF NORTHERN STATES POWER COMPANY'S FLOOD HAZARD REEVALUATION REPORT SUBMITTAL RELATING TO THE NEAR-TERM TASK FORCE RECOMMENDATION 2.1-FLOODING FOR MONTICELLO NUCLEAR GENERATING PLANT DOCKET NO. 50-263 BACKGROUND AND AUDIT BASIS By letter dated March 12, 2012, the U.S. Nuclear Regulatory Commission (NRC) issued a request for information to all power reactor licensees and holders of construction permits in active or deferred status, pursuant to Title 10 of the Code of Federal Regulations (1 O CFR),

Section 50.54(f), "Conditions of Licenses" (hereafter referred to as the "50.54(f) letter"). The request was issued in connection with implementing lessons learned from the 2011 accident at the Fukushima Dai-ichi nuclear power plant, as documented in the NRC's Near-Term Task Force report. Recommendation 2.1 in that document recommended that the NRC staff issue orders to all licensees to reevaluate seismic and flooding hazards for their sites using current NRC requirements and guidance. Subsequent staff requirements memoranda associated with SECY-11-0124 and SECY-11-0137 instructed the NRC staff address this recommendation through the issuance of requests for information to licensees pursuant to 10 CFR 50.54(f).

By letter dated May 12, 2016 (Agencywide Documents Access and Management System (ADAMS) Accession Nos. ML16145A233), Northern States Power Company, a Minnesota corporation (NSPM, the licensee), doing business as Xcel Energy, submitted its Flood Hazard Reevaluation Report (FHRR) for Monticello Nuclear Generating Plant (Monticello). The NRG is in the process of reviewing the aforementioned submittals and has completed a regulatory audit of NSPM to inform the licensee of its review of the submittals, identify any similarities/differences with past work completed, and ultimately aid in its review of licensees' FHRR. This audit summary is being completed in accordance with the guidance set forth in NRC Office of Nuclear Reactor Regulation Office Instruction LIC-111, "Regulatory Audits," dated December 29, 2008 (ADAMS Accession No. ML082900195}.

AUDIT LOCATION AND DATES The audit was completed by document review via the electronic reading room (ERR) and a teleconference held on August 18, 2016. A closeout phone call was held on April 5, 2017.

Enclosure AUDIT TEAM Title Team Member Organization Team Leader, NRR/JLD Anthony Minarik NRC Project ManaQer, NRR/JLD Lauren Gibson NRC Branch Chief, NRO/DSEA Aida Rivera NRC Branch Chief, NRO/DSEA Christopher Cook NRC Technical ManaQer Richard Rivera-LuQo NRC Lead Hydrologist Mike Lee NRC Contractor Vinod Mahat ANL Contractor Nicholoas Haas ANL Contractor John Quinn ANL Contractor EuQene Yan ANL DOCUMENTS AUDITED of this report contains a list that details all the documents reviewed by the NRC staff, in part or in whole, as part of this audit. The documents were located in an ERR during the NRC staff review.

AUDIT ACTIVITIES In general, the audit activities consisted of the following actions:

Review background information on site topography and geographical characteristics of the watershed.

Review site physical features and plant layout.

Understand the selection of important assumptions and parameters that would be the basis for evaluating the individual flood-causing mechanisms described in the 50.54(f) letter.

Review model input/output computer files, such as Hydrologic Engineering Center (HEC)-River Analysis System (RAS), FL0-2D, and HEC-Hydrologic Modeling System (HMS), to gain an understanding of how modeling assumptions were programmed and executed. of this report provides more detail and summarizes specific technical topics (and resolution) of important items that were discussed and clarified during the audit. The items discussed in Attachment 2 may be referenced/mentioned in the staff assessment in more detail.

CLOSEOUT TELECONFERENCE MEETING Following the August 18, 2016, teleconference, the NRC staff identified certain information that needed to be provided on the docket in order to resolve some of the items discussed during the audit. The information updated or supplemented the FHRR based on the audit discussions.

This information included the following:

1) Certain plant diagrams showing the locations of key doors The requested information was received by e-mail dated September 23, 2016 (ADAMS Accession No. ML16323A329).

On April 5, 2017, the NRC informed the licensee that no further information was needed for the audit and that the virtual audit was henceforth considered closed.

Attachments:

1. Audit Documents

2. Monticello Information Needs - Audit/Post-Audit Summary

ATTACHMENT 1 Monticello Nuclear Generating Plant, Unit 1 Audit Document List

1. Black & Veatch, 2015, "Local Intense PMP Hydrology and Hydraulics," Calculation No.

180999.51.1005, Revision 2. April 2016.

2. NRG (U.S. Nuclear Regulatory Commission), 2011 d, "Design-Basis Flood Estimation for Site Characterization at Nuclear Power Plants in the United State of America,"

NUREG/CR-7046, November 2011, ADAMS Accession No. ML11321A195.

3. NSPM (Northern States Power - Minnesota), 2016a, "FHRR (Flood Hazard Reevaluation Report) Audit Presentation 8-18-16-Webinar Slides", in response to Monticello Nuclear Generating Plant (MNGP) Unit 1 Information Needs - Local Intense Precipitation, August 18, 2016.

4. NSPM, 2016b, "

Subject:

Monticello Nuclear Generating Plant Flood Hazard Reevaluation Report - Responses to Requested Information (COG no. MF7712)," email from John S. Fields, Monticello Projects Licensing to Lauren Gibson, Project Manager, U.S. Nuclear Regulatory Commission, September 23, 2016, 11 :03:54 AM, ADAMS Accession No. ML16323A329.

5. NSPM, 2016c, "Excel Spreadsheet HEC-RAS Inflows -- MNGP Spreadsheet Discussed in 03 & 04", in response to Monticello Nuclear Generating Plant (MNGP) Unit 1 Information Needs - Local Intense Precipitation, August, 2016.

6. NSPM, 2016d, "Hydraulic Models Tables - Tables 1-3 Discussed in Webinar for MNGP 03", in response to Monticello Nuclear Generating Plant (MNGP) Unit 1 Information Needs - Local Intense Precipitation, August 18, 2016.

7. Xcel Energy, 2016a, "Calculation 180999.51.1005 - Local Intense Precipitation, HEC-HMS Input & Output files", in a CD of "Monticello Nuclear Generating Plant" prepared on June 15, 2016 and sent to Victor Hall, Project Manager, U.S. Nuclear Regulatory Commission, June 2016.

8. Xcel Energy, 2016b, "Calculation 180999.51.1005 - Local Intense Precipitation, HEC-RAS Input & Output files", in a CD of "Monticello Nuclear Generating Plant" prepared on June 15, 2016 and sent to Victor Hall, Project Manager, U.S. Nuclear Regulatory Commission, June 2016.

ATTACHMENT 2 Monticello Nuclear Generating Plant Information Needs - Audit/Post-Audit Summary Information Information Need Description

Response

Need No.

1 Local Intense PreciQitation - Critical OQening locations The licensee provided additional annotated figures (NSPM 2016a) showing locations of the four missing critical door

Background:

In the Flood Hazard Reevaluation Report openings, and indicated that those door locations are (FHRR) Table 2 and Tables 3.0-1 and 5.4-5 of the local designated Doors 1, 193, 341, and 483 in both Table 2 of the intense precipitation (LIP) calculation package (Black &

FHRR and the supporting LIP calculation package (Tables 3.0-1 Veatch, 2015), the calculated maximum water surface and 5.4-5). One of the figures provided also illustrates the elevations (WSEs) exceeded the as-built door sill elevations location of Door 30 that was mentioned in FHRR Section 2.1 0.1.

at 11 critical door opening locations. The locations for 7 of In its response, the licensee also addressed a related door the 11 critical doors are shown in Figures 5.3.5-1 and 5.3.6-1 opening location question related to the Fuel Oil Transfer of the LIP calculation package. However, the locations of the Pumping House. The licensee noted that the maximum WSE remaining 4 critical openings are not presented or discussed simulated for a critical door opening there was based on the in any of the FHRR-related documents.

hydraulic model described as "MNGP Site West Sub2a In a related matter, Table 5.4-5 presents hydraulic model -

Plan.P01." The licensee acknowledged that the hydraulic model mentioned in the Table 5.4-5 calculation package as "MNGP [Monticello Nuclear Generating Plant] Site West "MNGP Site West Sub21 Plan.P01 " was in fact a typographical Sub21" - and the maximum WSEs simulated by this model error (NSPM 2016a).

for one critical door location; however, the model is not cited (referenced) in any of the documents just described.

In order to complete the review of all critical door opening locations at the Monticello site, the staff requested that the Request: It is requested that the licensee describe the licensee provide revised figures to include all critical door locations and modeling results for all critical door openings opening locations in question, their river reaches, and that are assumed for safety-related structures, systems and associated cross sections using appropriate annotations and components at the reactor site. It is also requested that the legends. On September 23, 2016, the figures were submitted to licensee provide the hydraulic model files and related the NRC (NSPM, 2016b).

documents for computer model designated "MNGP Site West The NRC staff reviewed information provided during the audit Sub21 ".

and the figures subsequently provided by the licensee after the audit, and concluded that the information provided by the licensee was sufficient to address this information need request.

Information Information Need Description

Response

Need No.

2 Local Intense Preci~itation - Unit h)ldrogra~h In response to the information need request, the licensee explained that the reduction in the lag time by 33% in the SCS

Background:

The licensee used the Soil Conservation of the unit hydrograph method will result in an increase in the Service (SCS) Unit Hydrograph method to transform unit hydrograph peak discharge. For a lag time range of 3.6 to precipitation into surface runoff. The derived unit hydrograph

88. 7 minutes, the estimated discharge increase ranges from (including the SCS unit hydrograph) may not always 41 % to 49% after lag time adjustment, and further adjustment of represent the actual hydrometeorological conditions that the peak discharge was not warranted (NSPM, 2016a).

might prevail during the probable maximum flood (PMF) event. Consequently, NUREG/CR-7046 (NRC, 2011)

The NRC staff concluded that the information provided by the recommends that nonlinearity adjustments to the unit licensee was sufficient to address the staff's information need hydrograph should be made by increasing the peak of the request.

unit hydrograph by 20% and reducing the time of peak by 33%. As part of its review, the staff found that the licensee reduced the time of the peak by 33% but didn't increase the peak of the unit hydrograph by 20%.

Request: It is requested that the licensee explain its reasoning for why unit hydrograph was not adjusted to account for the nonlinear effects of the basin response to the peak flow.

3 Local Intense Preci~itation - Model in~ut/out~ut files and In response to the information need request, the licensee the model runs prepared: (a) an Excel spreadsheet (NSPM, 2016c); and (b) summary tables (NSPM, 2016d) containing the names of the

Background:

The licensee provided several input/output (1/0) final versions of the 1/0 files that were associated with the model files for both the U.S. Army Corps of Engineer's simulated model results for the critical door openings presented Hydrologic Engineering Center Hydrologic Modeling System in the FHRR. That spreadsheet was placed in the licensee's (HEC-HMS) and Hydrologic Engineering Center River ERR. Upon review, the staff found that the spreadsheet Analysis System (HEC-RAS) software packages. Both the included a cross-walk between the HEC-HMS sub-basins and HEC-HMS and HEC-RAS computer models and their the corresponding HEC-RAS models. The staff also confirmed attendant 1/0 files were placed in the licensee's electronic Information Information Need Description

Response

Need No.

reading room (ERR). However, upon review, it is not clear that the Excel spreadsheet identified the flow distribution which version of those 1/0 files was the principal file calculations in relation to the 11 critical door opening locations.

associated with the results presented in the licensee's FHRR.

The NRC staff reviewed the information provided by the Request: It is requested that the licensee identify the final licensee and the 1/0 files for HEC-HMS and HEC-RAS models version(s) of the 1/0 files used, and their corresponding (Xcel Energy, 2016a and 2016b) and concluded that the results presented in the FHRR for the respective HEC-HMS information provided was sufficient to address the staff's and HEC-RAS computer models.

information need request.

4 Local Intense Preci~itation - Flow distribution to In response to the information need request, the licensee reaches/cross sections explained that the distribution of the flow to reaches and cross-sections within a sub-basin was calculated using a spatial

Background:

The HEC-HMS model was used to transform weighting scheme based on: (a) the percentage of drainage the precipitation into runoff (flow). For each sub-basin or area corresponding to each reach within the basin; and (b) a reach, the flow simulated by the HEC-HMS model serves as flow accumulation estimate that itself was based on an estimate an input to the HEC-RAS model. However, in the HEC-RAS of accumulated GIS pixels corresponding to a specific location models, many of the model sub-basins have more than one of interest. In response to this information need request, a reach (drainage path), and sub-basin flow can be distributed spreadsheet was placed in the ERR documenting the spatial among multiple reaches. Upon review, the staff found that weighting schemes and flow distributions to reaches and cross surface flow was also distributed to many cross sections sections in each sub-basin used by the licensee (NSPM, within a sub-basin. In its FHRR, the licensee stated that the 2016c).

flow was distributed to different reaches or cross sections via a spatial weighting scheme, but it is not clear from the FHRR The NRC staff reviewed the spreadsheet and concluded that text how that spatial weighting scheme was determined and the information provided by the licensee was sufficient to how the results were subsequently implemented in the HEC-address the information need request.

RAS model.

For example, HEC-HMS model (MNGP Site East: Sub-Basin-

3) simulated peak flow for sub-basin 3 is 448.8 cubic feet per second (ft3/s, cfs} (Figure 1 ), and this flow value was distributed to three reaches within the same sub-basin in the HEC-RAS model as 168.1 ft3/s (37%), 92.7 ft3/s (21 %) and 188 ft3/s (42%) (See page 51 of the calculation package

[Black & Veatch, 20151). It is not clear how these distributed Information Information Need Description

Response

Need No.

values were derived. Similarly, in the HEC-HMS model MNGP Site South: Sub-Basin 9, simulated peak flow for sub-basin 9 is 242.7 cfs (Figure 2), and the flow was distributed to four cross sections within the same sub-basin. Again, it is not clear how the flow distribution was achieved within the model.

Request: It is requested that the licensee identify which FHRR supporting documents contain the calculation results showing the flow distributions among the respective reaches and cross sections for the various sub-basins. In connection with the identification, it is also requested that the licensee place these documents in the ERR.

Sources:

Black & Veatch, 2015, "Local Intense PMP Hydrology and Hydraulics," Calculation No. 180999.51.1005, Revision 2. April 2016.

NRC (U.S. Nuclear Regulatory Commission), 2011 d, "Design-Basis Flood Estimation for Site Characterization at Nuclear Power Plants in the United State of America," NUREG/CR-7046, November 2011, ADAMS Accession No. ML11321A195.

NSPM, 2016a, "FHRR (Flood Hazard Reevaluation Report) Audit Presentation 8-18 Webinar Slides", in response to Monticello Nuclear Generating Plant (MNGP) Unit 1 Information Needs - Local Intense Precipitation, August 18, 2016.

NSPM, 2016b, "Monticello Nuclear Generating Plant Flood Hazard Reevaluation Report - Responses to Requested Information (CAC No. MF7712)," email from John S. Fields, Monticello Projects Licensing to Lauren Gibson, Project Manager, U.S. Nuclear Regulatory Commission, September 23, 2016, 11 :03:54 AM, ADAMS Accession No. ML16323A329.

NSPM, 2016c, "Excel Spreadsheet HEC-RAS Inflows -- MNGP Spreadsheet Discussed in 03 & 0 4", in response to Monticello Nuclear Generating Plant (MNGP) Unit 1 Information Needs - Local Intense Precipitation, August, 2016.

NSPM, 2016d, "Hydraulic Models Tables - Tables 1-3 Discussed in Webinar for MNGP 03", in response to Monticello Nuclear Generating Plant (MNGP) Unit 1 Information Needs - Local Intense Precipitation, August 18, 2016.

Xcel Energy, 2016a, "Calculation 180999.51.1005 - Local Intense Precipitation, HEC-HMS Input & Output files", in a CD of "Monticello Nuclear Generating Plant" prepared on June 15, 2016 and sent to Victor Hall, Project Manager, U.S. Nuclear Regulatory Commission, June 2016.

Xcel Energy, 2016b, "Calculation 180999.51.1005 - Local Intense Precipitation, HEC-RAS Input & Output files", in a CD of "Monticello Nuclear Generating Plant" prepared on June 15, 2016 and sent to Victor Hall, Project Manager, U.S. Nuclear Regulatory Commission, June 2016

NUCLEAR REGULATORY COMMISSION REPORT FOR THE AUDIT NORTHERN STATES POWER COMPANY'S FLOOD HAZARD REEVALUATION REPORT SUBMITTAL RELATING TO THE NEAR-TERM TASK FORCE RECOMMENDATION 2.1-FLOODING FOR MONTICELLO GENERATING PLANT (CAC NO. MF7712} DATED APRIL 18, 2017 DISTRIBUTION:

PUBLIC JLD R/F RidsNRRJLD Resource RidsNrrPMDuaneArnold Resource NSanfilippo, NRR BHayes, NRO RRivera-Lugo, NRO CCook, NRO KQuinlan, NRO Mlee, NRO LGibson, NRR LQuinn-Willingham, NRO MWillingham, NRO RidsNrrDorlLPL3 Resource ADAMS Accession No.: ML17096A443

• via email OFFICE NRR/JLD/JHMB/PM NRR/JLD/JHMB/LA NRO/DSEA/RHM1/BC NRR/JLD/JHMB/BC NAME LKGibson Slent CCook NSanfiliooo DATE 4/13/17 4/10/17 4/13/17 4/14/17 OFFICE NRR/JLD/JHMB/PM NAME LKGibson (FVega for)

DATE 4/18/17