ML16127A556
| ML16127A556 | |
| Person / Time | |
|---|---|
| Site: | Duane Arnold  |
| Issue date: | 12/21/2016 |
| From: | Lauren Gibson Japan Lessons-Learned Division |
| To: | Vehec T NextEra Energy Duane Arnold |
| Minarik A, NRR/JLD, 415-6185 | |
| References | |
| CAC MF3683 | |
| Download: ML16127A556 (18) | |
Text
UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 Mr. Thomas A. Vehec Site Vice President NextEra Energy Duane Arnold Energy Center 3277 DAEC Road Palo, IA 52324-9785 December 21, 2016
SUBJECT:
NUCLEAR REGULATORY COMMISSION REPORT FOR THE AUDIT OF NEXTERA ENERGY, LLC'S FLOOD HAZARD REEVALUATION REPORT SUBMITTAL RELATING TO THE NEAR-TERM TASK FORCE RECOMMENDATION 2.1-FLOODING FOR DUANE ARNOLD ENERGY CENTER (CAC NO. MF3683)
Dear Mr. Vehec:
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 NextEra Energy Duane Arnold, LLC's (NextEra's, the licensee's) Flood Hazard Reevaluation Report (FHRR) submittal related for Duane Arnold Energy Center (Duane Arnold). 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 17, 2015 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML15160A715), the NRC informed you of the staff's plan to conduct a regulatory audit of NextEra's FHRR submittal for Duane Arnold. 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 July 2015 - March 2016, with periodic meetings to discuss NRC staff information needs. The NRC staff and NextEra held an exit meeting on March 28, 2016, during which the remaining documentation needs were discussed. 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 this audit have been discussed with Mr. Tim Holt 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. 50-331
Enclosure:
Audit Report cc w/encl: Distribution via Listserv Sincerely, 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 NEXTERA ENERGY DUANE ARNOLD, LLC'S FLOOD HAZARD REEVALUATION REPORT SUBMITIAL RELATING TO THE NEAR-TERM TASK FORCE RECOMMENDATION 2.1-FLOODING FOR DUANE ARNOLD ENERGY CENTER DOCKET NO. 50-331 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 (10 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 and enclosure dated March 10, 2014 (Agencywide Documents Access and Management System (ADAMS) Accession Nos. ML14072A019 and ML14072A020, respectively), NextEra Energy Duane Arnold, LLC (NextEra, the licensee) submitted its Flood Hazard Reevaluation Report (FHRR) for Duane Arnold Energy Center (Duane Arnold, DAEC).
The NRC is in the process of reviewing the aforementioned submittals and has completed a regulatory audit of NextEra 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 electronic reading room and teleconferences held on the following dates: September 10, 2015, November 5, 2015, December 14, 2015, Enclosure February 4, 2016, and March 21, 2016. A closeout meeting was held by telephone on March 28, 2016.
AUDIT TEAMS Title Team Member Organization Team Leader, NRR/JLD Anthony Minarik NRC Branch Chief, NRO/DSEA Aida Rivera NRC Technical Manager Richard Rivera-Lugo NRC Lead Hydrologist Mike Lee NRC Lead Meteorologist Kevin Quinlan NRC Technical Support (hydro.)
Raiiv Prassad Pacific NW National Lab Technical Support (hydro.)
Nancy Boyd Pacific NW National Lab Technical Support (hydro.)
Yuan Yong Pacific NW National Lab Technical Support (met.)
Scott DeNeale Oak Ridge National Lab
~hnical Support (met.)
David Watson Oak Ridge National Lab hnical Suooort (met.)
Shieh-Cheh Kao Oak Ridge National Lab Site Fukushima Response Mgr Curt Bock NextEra (DAEC)
Licensing Engineer Tim Holt NextEra (DAEC)
Licensing Engineer Clara Rushworth NextEra (DAEC)
Fukushima Response Mgr Ronnie Lingel NextEra (Corp.)
Fleet Licensing Mgr Bill Cross NextEra (Corp.)
Technical Lead (hydro.)
Shaun Kline Enercon Technical Support (Hydro.)
Chris Moyer Enercon Technical Support (Hydro.)
Justin Pistininzi Enercon Technical Support (Hydro.)
Paul Martinchich Enercon Technical Manager (Hydro.)
Wayne Miller Enercon Technical Lead (Met.)
Bill Kappel Applied Weather Assc.
(AWA)
Technical Support (Met.)
Doug Hultstrand AWA DOCUMENTS AUDITED of this report contains a list which details all the documents that were reviewed by the NRC staff, in part or in whole, as part of this audit. The documents were located in an electronic reading room 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 files to computer files, such as Hydrologic Engineering Center (HEC)-River Analysis System (RAS), FL0-2D, and HEC-Hydrologic Modeling System (HMS), to have 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.
EXIT MEETING/BRIEFING:
On March 28, 2016, the NRG staff closed out the discussion of the technical topics described above. The NRG 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 would update or supplement the FHRR based on the audit discussions. This information included the following:
- 1) A formal response providing flood elevation levels for the local intense precipitation event, and the riverine flooding event,
- 2) An explanation of the effects that changing the drainage basin area had on the FHRR values, and
- 3) The wind/wave analysis and justifications for using a fetch length that is smaller than the inundation area of the plant (i.e. mature vegetation and obstacles).
The requested information was received by letter dated August 12, 2016 (ADAMS Accession No. ML16229A159).
Attachments:
1. Audit Documents
- 2. Duane Arnold Information Needs -Audit/Post-Audit Summary
ATTACHMENT 1 Audit Documents Alexeev, G. A., I. L. Kaljuzhny, V. Y. Kulik, K. K. Pav-lova and V. V. Romanov.
1972.
"Infiltration of Snowmelt Water into Frozen Soil: The Role of Snow and Ice in Hydrology,"
Proceedings of the Banff Symposia, Vol. 1, Geneva, WMO, IAHS, UNESCO, Banff, pp. 313-325.
Dingman, S.L. 1975. "Hydrologic Effects of Frozen Ground: Literature Review and Synthesis."
Cold Regions Research and Engineering Laboratory (CAREL) Special Report 218, U.S. Army CAREL, Hanover, NH.
Hinkel, K.M., S.I. Outcalt, and A.E. Taylor. 1997. "Seasonal patterns of coupled flow in the active layer at three sites in northwest North America." Canadian Journal of Earth Sciences, 34, pp. 667-678.
Luo, L., A. Roback, K.Y. Vinnikov, C.A. Schlosser, A.G. Slater, A. Boone, H. Braden, P. Cox, P. de Rosnay, R.E. Dickinson, Y. Dai, Q. Duan, P. Etchevers, A. Henderson-Sellers, N.
Gedney, Y.M. Gusev, F. Habets, J. Kim, E. Kowalczyk, K. Mitchell, O.N. Nasonova, J. Noilhan, A.J. Pitman, J. Schaake, A.B. Shmakin, T.G. Smirnova, P. Wetzel, Y. Xue, Z.-L. Yang, and Q.
Zeng. 2002. "Effects of Frozen Soil Temperature, Spring Infiltration, and Runoff: Results from the PILPS 2(d) Experiment at Valdai, Russia." Journal of Hydrometeorology, 4, pp. 334-351.
Sutinen, R., P. Hanninen and A. Venalainen. 2008. "Effect of mild winter events on soil water content beneath snowpack." Cold Req. Sci. Technol., 51, pp. 56-67.
U.S. Army Corps of Engineers (USAGE). 1998. "Runoff from Snowmelt." Engineer Manual EM-1110-2-1406, Department of the Army, Washington, DC.
USAGE 1984. "Shore Protection Manual, Volumes 1 and 2."
USAGE 2008. "Coastal Engineering Manual," EM 1110-2-1100 Part II.
ATTACHMENT2 Duane Arnold Information Needs - Audit/Post-Audit Summary INFO INFORMATION NEED DESCRIPTION ACTION (POST*AUDIT)
NEED 1
Local Intense Precipitation (LIP) Flood: Choice of The licensee noted that it had considered four land-use classes for the purposes of Model Parameters the LIP flood analysis. Those classes and the corresponding Manning's n values Evaluation of the effects of flooding LIP on water (the corresponding FL0-20 recommended ranges are in parentheses) were:
surface elevations at the Duane Arnold Energy Asphalt (0.02 - 0.05)
Center (DAEC) site is requested in the 50.54(f)
Mixed asphalt and grass {licensee reasoned that asphalt with grass will have a letter. The licensee selected Manning's roughness higher roughness) coefficient values based on FL0-20 guidance.
Open ground with debris (0.1 - 0.2)
However, the staff noticed that for most land-use Shrubs and forest litter {0.3 - 0.4) types, the licensee-selected values were at the lower end of the range of recommended values in The Manning's n roughness values chosen by the licensee for asphalt-covered the FL0-20 guidance. Because lower values of surfaces is 0.02 because the center of the DAEC powerblock site was completely Manning's n roughness coefficient enhance water impervious. For areas surrounding the site that are a mixture of impervious-drainage away from site areas that may contain covered surfaces and maintained pervious land cover, the licensee used the safety-related buildings, the estimated flood depth higher-end of the "asphalt" range (0.05). The licensee used a value of 0.2, the elevations could be underestimated near those higher-end of the "open ground with debris" range for areas that were judged to critical facilities.
consist of non-concrete/asphalt and un-forested surfaces. Forested areas north of the DAEC site were considered "shrubs and forest litter, pasture," with a The staff requests the licensee to provide corresponding roughness coefficient of 0.3, the lower-end of the suggested range.
justification explaining its rationale for selecting The licensee also noted that they had performed a sensitivity analysis using the Manning's roughness coefficient values that are higher-end of the recommended range of Manning's roughness values for all toward the lower range of recommended values.
surfaces and found that the maximum increase in flood depths at the critical door locations identified in the FHRR was approximately 1 inch (in.).
Although the degree of imperviousness of a surface does not control its roughness, the staff concluded that the licensee used the deqree of imperviousness as a INFO INFORMATION NEED DESCRIPTION ACTION*(POST-AUDIT)
NEED 2
surrogate for vegetation growth cover that would affect roughness of a surface.
The licensee's sensitivity analysis showed that the maximum water-surface elevations near critical door locations are not sensitive to Manning's roughness.
The staff found that the licensee's explanation (reasoning) for choosing the values of Manning's roughness coefficient was reasonable. The staff concluded that the licensee's approach was reasonable and had met the general intent of the 50.54(f) letter. No further action is necessary.
LIP Flood: Model Configuration Evaluation of the effects of flooding of LIP on water The licensee confirmed that ARFs were not used in any of the FL0-20 LIP flood surface elevations at the OAEC site is requested in simulations. The licensee also stated that they did not include WRFs for those grid the 50.54(f) letter. The FHRR described the use of cells corresponding to the locations of the VBS in their LIP flood simulations. The area reduction factors (ARFs) and width reduction licensee stated that a sensitivity run was performed with FL0-20 Pro Build factors (WRFs) for representing permanent and 14.08.09, instead of the previously-used Build 13.11.06.1 For the center-loaded temporary obstructions to flow within the licensee's temporal distribution of the site-specific LIP event, the licensee reported that the FL0-20 modelling domain. The FHRR also stated difference in simulated water depths at the selected doors was minimal between that WRFs were used for grid cells corresponding to the two model runs.
the location of the vehicle barrier system (VBS).
The staff's review of the licensee's FL0-20 model The staff verified that correctly including WRFs for grid cells corresponding to the setup revealed that the FL0-20 input files did not location of the VBS in the FL0-20 model resulted in minimal difference in water contain any data for ARFs for buildings and other depths at selected door locations. The staff concluded that the licensee's approach temporary site structures. The staff review also was reasonable and had met the general intent of the 50.54(f) letter. No further revealed that althouQh ARFs and WRFs for the VBS action is necessary.
1 In Build 14.08.09, the FL0-20 developer had fixed a number of issues related to representation of grid cells with ARFs specified. One of these issues with earlier Build 13.11.06 was that meteoric water was retained on building roofs if the ARFs for those corresponding grid cells were set to a value of 1.
INFO
>,INFORMATION NEED DESCRIPTION ACTION (POST*AUDIT)
NEED were specified in the licensee's FL0-20 input file, an option flag that turns on the use of ARFs and WRFs was actually turned off during all model simulations.
The staff requests the licensee to clarify and resolve the inconsistency between the FHRR description and the actual model configuration in the modeling of buildings and VBS structures in the FL0-20 model.
3 LIP Flood: Model Configuration Evaluation of the effects of flooding of LIP on water In response to this information need request, the licensee noted that there was a surface elevations at the OAEC site is requested in possibility that secondary scuppers located on the building roofs could concentrate the 50.54(f) letter. The licensee's FL0-20 model flow above the rolling doors on the north and south sides of the OAEC turbine considered building roofs as elevated flat surfaces building. However, the licensee showed that the estimated discharge in front of the from which roof runoff was allowed to drain evenly to doors in question would be about 1 cubic foot per second (cfs), but this would not surrounding areas. Section 11.4 of American occur at the time of the peak discharge during the LIP event. Additionally, because National Standards Institute/American Nuclear the roof parapets are approximately 13.5-in. high, minimal overtopping from the Society (ANSI/ ANS)-2.8-1992 recommends that site-specific LIP depth of 14.1 in. is expected. The licensee's FL0-20 LIP flood building runoff used in the LIP flood assessment model does not incorporate parapets and therefore does not take credit for water allow evaluation of worst-case roof drainage, stored on the roofs.
including analysis of alternative points of roof drainage to maximize flood elevation adjacent to The staff agrees with the licensee that the FHRR LIP flood model is reasonably points of access and egress at safety-related conservative, because it does not take credit for water stored on roofs. The staff structures, systems and components. Allowing roof concluded that the licensee's approach was reasonable and had met the general runoff to drain adjacent to turbine building doors intent of the 50.54(f) letter. No further action is necessary.
could substantially increase the water depths at those locations. A preliminary sensitivity analysis by the staff that directed part of the roof to drain near INFO INFORMATION NEED DESCRIPTION ACTION (POST~AUDIT)
NEED the turbine building doors showed that water depths adjacent to the doors would substantially increase.
The staff requests the licensee to describe how drainage from facility roofs as represented in FLO-20 analyses is consistent with the recommendations of ANSI/ ANS-2.8-1992, Section 11.4 or provide a revised analysis.
4 Streams and Rivers: Drainage Area Used for the Probable Maximum Precipitation Estimation The NRG staff noted that the upstream watershed area of 6,250 mi2 area, In developing the probable maximum precipitation corresponding to the watershed immediately above the DAEC site, is the (PMP) used to estimate the probable maximum appropriate area to use for the FHRR as it is (a) consistent with how the current flood (PMF) at the DAEC site, the licensee selected design basis was developed and (b) accepted engineering practice for the conduct the complete drainage area of the Cedar River of such types of analyses.
watershed at the point where the Cedar River joins the Iowa River. The FHRR reported that the area of In an electronic reading room document (dated January 11, 2016), the licensee the watershed upstream of the DAEC site is 6,250 described a revised PMP analysis for a drainage area corresponding to 6,250 mi2.
mi2, and the total drainage area at the mouth of the In doing so, the licensee also removed those downstream subbasins (specifically Cedar River is 7,824 mi2. Because the area subbasins SB30, SB31, SB32, SB33, and SB34) that no longer applied to their upstream of the DAEC site is about 20 percent revised hydrologic model. The licensee's revised model relied on site-specific smaller than the total watershed area, there could PMP depth-area duration values obtained from the HMR52 software to estimate be a significant increase in the PMP if the smaller the all-season and the cool-season PMP hyetographs for the subbasins comprising area is used with depth-area-duration curves to the 6,250 mi2 drainage area. The licensee used seven storm centers, all located estimate basin average precipitation.
upstream of the DAEC site, and five temporal distributions for the precipitation The staff estimated that the maximum increase to estimates in the HEC-HMS simulations.
both the Hydrometeorological Report (HMR) and the site-specific PMP depths for various durations could The licensee repeated the all-season and the cool-season PMF analysis using the be as much as 9 percent. The staff requests the newly-estimated PMP hyetographs, keeping all other model parameters
INFO NEED INFORMATION NEED*DESCRIPTION licensee to justify the use of the larger watershed area as the basis for PMP estimation. ACTION(POST*AUDIT) unchanged. The licensee determined that the all-season, front-third-loaded PMP storm centered on storm center 4 resulted in the highest peak discharge in the HEC-HMS simulations. The licensee found that the peak discharge for the all-season PMF increased by 4 percent, from 319, 119 cfs to 331,973 cfs. The licensee determined that the cool-season, center-loaded PMP storm centered on storm center 4 resulted in the highest peak discharge in the HEC-HMS simulations.
For the cool-season PMF, Alternative 3 (100-year snowpack and coincident snow-season PMP), the smaller (corrected) drainage area resulted in an increase of 1.5 percent in the peak discharge, from 402,509 cfs to 408,383 cfs. Using the newly-estimated discharge hydrographs at J27-28 (river discharge), 8828 (inflow), and 8829 (inflow) in the hydraulic model, the licensee found that the maximum stillwater water surface elevation (WSE) at the DAEC site increased to 765.2 ft North American Vertical Datum of 1988 (NAVD88) from the 763.5 ft NAVD88 reported in the FHRR.
Subsequently, in material provided to the NRC in connection with the audit {on February 22, 2016), the licensee presented an analysis using a "refined PMP depth-area-duration relationships" that were accepted by NRC's review of the licensee's site-specific PMP. The refined analysis, using the 6,250 mi2 drainage area, resulted in a stillwater WSE of 764.8 ft NAVD88 at the DAEC site. The refined PMP depth-area-duration relationship is reproduced below.
Duration Area (hr)
(mi2) 6 12 24 48 72 10 7.1 9.6 13.6 15.5 15.6 100 6.9 9.3 13.4 14.8 14.9 INFO INFORMATION NEED DESCRIPTION ACTION(POST*AUDIT)
NEED 200 6.7 9.0 13.1 14.4 14.5 500 6.4 8.5 12.4 13.8 13.9 1000 6.1 8.1 11.7 13.2 13.3 2000 5.7 7.6 11.0 12.5 12.6 5000 5.2 6.9 9.9 11.5 11.6 10,000 4.5 6.1 8.7 10.5 10.6 20,000 3.6 5.3 7.4 9.3 9.4 Precipitation depths are reported in inches.
The staff reviewed the model files and results summary associated with the licensee's refined HEC-HMS analysis, and verified the resulting stillwater WSE of 764.8 ft NAVD88 at the DAEC site. The staff concluded that the licensee's approach was reasonable and had met the general intent of the 50.54(f) letter. No further action is necessary.
(The licensee also revised its wind-wave estimate for the higher WSE resulting from the refined PMF analysis. See Information Need 8, below.)
5 Streams and Rivers: Loss Rates for a PMF Event In its FHRR, the licensee stated that a constant loss In response to this information need request (dated July 23, 2015), the licensee rate was calibrated for each subbasin based on the asserted that modeling the whole Cedar River watershed PMF in a saturation-historical event simulated in the calibration. The excess state would be overly-conservative. In support of that position, the licensee constant loss rates range from 0.11 to 0.3 in/hr.
estimated that the depth of precipitation required to create saturated runoff These constant loss rates lead to very large losses conditions in the watershed would be approximately 25 in., which exceeds current of the PMP rainfall and snowmelt in the PMF model, INFO INFORMATION NEED DE$CRIPDON ACTl()N (POST-AUDIT)
NEED on the order of 50 percent of the total input. A real estimates of the combined flood depth associated with snowmelt and a cool-flood on the order of a PMP event would have season PMP.
saturated ground and after some time would not allow any additional infiltration; hence, the most In a subsequent response (dated October 27, 2015), the licensee further asserted conservative and typical assumption for PMF that most of the calibrated and validated infiltration rates for the DAEC watershed modeling is that ongoing losses are zero or minimal.
were at or below the minimum for NRCS Soil Group 8, which is the dominant soil The staff's sensitivity analyses with reduced type for this particular watershed. The licensee also provided the references it constant loss rates show a significant increase in cited as rationale for its selection of loss rate values, including allowance for peak discharge and associated water-surface infiltration capacity in frozen soils - i.e., Alexeev et al. (1972); Dingman (1975);
elevation near the DAEC site.
Hinkel et al. (1997); USAGE (1998); Luo et al. (2002); and Sutinen et al. (2008).
These references were later examined by the staff.
The staff requests that the licensee justify the use of these large constant loss rates in the PMF model or While the staff agrees that some infiltration can take place even under frozen soil revise the model with more commonly accepted conditions, the staff's sensitivity analyses demonstrated that the maximum PMF constant loss rates.
stillwater elevation at the DAEC site is very sensitive to selected loss rates in the DAEC watershed upstream of the site. The staff concluded that the licensee's approach was reasonable and met the general intent of the 50.54(f) letter. No further action is necessary.
References cited:
Alexeev, G. A., I. L. Kaljuzhny, V. Y. Kulik, K. K. Pav-lova and V. V. Romanov. 1972. "Infiltration of Snowmelt Water into Frozen Soil: The Role of Snow and Ice in Hydrology," Proceedings of the Banff Symposia, Vol. 1, Geneva, WMO, IAHS, UNESCO, Banff, pp. 313-325.
Dingman, S.L. 1975. "Hydrologic Effects of Frozen Ground: Literature Review and Synthesis." CRREL Special Report 218, U.S. Army Corps of Engineers Cold Regions Research and Engineering Laboratory, Hanover, NH.
Hinkel, K.M., S.I. Outcalt, and AE Taylor. 1997. "Seasonal patterns of coupled flow in the active layer at three sites in northwest North America." Canadian Journal of Earth Sciences, 34, pp. 667-678.
INFO
.... INFORMATION NEED DESCRIPTION ACTION.(POST*AUDIT)
NEED U.S. Army Corps of Engineers. 1998. "Runoff from Snowmelt." Engineer Manual EM-1110-2-1406, Department of the Army, Washington, DC.
Luo, L., A. Robock, K. Y. Vinnikov, C.A. Schlosser, A.G. Slater, A. Boone, H. Braden, P. Cox, P. de Rosnay, R.E. Dickinson, Y. Dai, Q. Duan, P. Etchevers, A. Henderson-Sellers, N. Gedney, Y.M. Gusev, F. Habets, J.
Kim, E. Kowalczyk, K. Mitchell, O.N. Nasonova, J. Noilhan, A.J. Pitman, J. Schaake, A.B. Shmakin, T.G.
Smirnova, P. Wetzel, Y. Xue, Z.-L. Yang, and Q. Zeng. 2002. "Effects of Frozen Soil Temperature, Sprint Infiltration, and Runoff: Results from the PILPS 2(d) Experiment ar Valdai, Russia." Journal of Hydrometeorology, 4, pp. 334-351.
Sutinen, R., P. Hanninen and A. Venalainen. 2008. "Effect of mild winter events on soil water content beneath snowpack." Cold Req. Sci. Technol., 51, po. 56-67.
6 Streams and Rivers: Initial Loss for all Subbasins Evaluation of the effects of flooding of streams and The licensee stated that their calibration methodology assumed the same starting rivers on water surface elevations at the DAEC site initial-loss value for all subbasins. It appears that the licensee also assumed the is requested in the 50.54{f) letter. The licensee initial-loss value to be uniform across all 34 subbasins. In its response (dated July stated in calculation package FPL-070-CALC-005 23, 2015), the licensee explained that the starting initial-loss value for all subbasins Rev. O that the initial loss was calibrated for each of was set at 1.0 in. prior to calibration. The initial-loss value was not calibrated for the subbasins, and not the watershed as a whole.
subbasins individually. The licensee used two major flood events in May 2004 and However, the NRC staff's review of the licensee's June 2008 recorded at the streamflow gauge 05464500, Cedar River at Cedar model files revealed that the initial loss values for all Rapids, Iowa for calibration of loss parameters. The June 2008 flood event was subbasins was set to 0.45 in.
used as the calibration event and the May 2004 flood event was used as the validation event.
The staff requests that the licensee explain why all the initial loss values are the same.
The NRC staff reviewed the licensee's response and found the modeling approach initially being questioned to be reasonable. The staff concluded that the licensee's approach had met the general intent of the 50.54(f) letter. No further action is necessary.
7 Streams and Rivers: HEC-HMS Model Setup INFO INFORMATION NEED DESCRIPTION ACTION (POST*AUDIT)
NEED The licensee developed a time series of incremental The licensee acknowledged that the FHRR PMF analysis relied on an erroneous precipitation and snowmelt for each of 34 subbasins hyetograph for subbasin 6. The licensee corrected the error and revised their in the watershed. The precipitation scenario for the HEC-HMS analysis using a center-loaded PMP with storm center 4 to be the PMF was based on using storm center 6 and a controlling case.
center-loaded temporal pattern. However, while reviewing the licensee's HEC-HMS input files, the The staff reviewed the licensee's response and found it acceptable. The staff staff identified that the precipitation and snowmelt concluded that the licensee's approach had met the general intent of the §50.54(f}
time series provided for subbasin 6 has a temporal letter. No further action is necessary.
pattern that is very different from all of the other subbasins, and appears to be from a front-loaded temporal pattern. The staff performed an HEC-HMS run with a center-loaded precipitation and snowmelt time series for subbasin 6 and determined that the peak discharge at DAEC, reported to be 402,509 cfs in the FHRR, reduced significantly.
The staff requests that the licensee provide the appropriate precipitation and snowmelt input time series for subbasin 6 or to provide an explanation why the input time series currently in the licensee's HEC-HMS model is the appropriate one.
8 Streams and Rivers: Wind-Wave Activity In its FHRR, the licensee described the estimation of In a response dated March 2, 2016, the licensee stated that a detailed description wind-wave activity coincident with the PMF in rivers of the procedure to estimate wind-wave effects were contained in a document and streams. Table 4-21 in the FHRR provides the entitled "Calculation FPL-070-Cal-012 Revision 0, 'Co-Incident Wind Wave and wind setup and runup estimates used. However, the Runup'." In its review of that calculation package, the staff determined that the licensee did not provide details of the method it used licensee used the USAGE Shore Protection Manual (USAGE, 1984} and the to estimate wind wave activitv.
Coastal Engineering Manual (USAGE, 2008) to estimate wind-wave effects; use of INFO INFORMATION NEED DESCRIPTION ACTION (POST-AUDIT)
NEED The staff requests the licensee to provide a detailed these two documents in the estimation of wind-wave effects is consistent with description of wind wave estimation procedure current NRG guidance. The licensee also provided an updated wind-wave analysis including citations.
based on the USAGE methodology, but updated for higher stillwater PMF elevation, 764.8 ft NAVD88, for the corrected 6,250-mi2 drainage area. The It is requested that the licensee provide a detailed licensee's initial response, though, did not provide technical justification for the description of wind wave estimation procedure selection of fetch length. The staff subsequently requested that the licensee including the identification of appropriate citations.
provide this information.
In response to an e-mail inquiry (dated June 20, 2016), the licensee described its wind-wave analysis and provided clarification regarding the manner in which the fetch length was arrived at for the purposes of the FHRR wind/wave analysis. In its response, the following points are noteworthy:
Fetches affecting the DAEC site are restricted by geometry and limit wave growth.
Wave runup from the east, west, south, southwest, and southeast directions were evaluated because the longest unobstructed fetches occur in those directions.
The longest fetch length estimated was 11,200 ft in the south direction from the plant.
The southern fetch runs from the DAEC site to an elevated highway (the Briars Ferry Road location, to the south of the DAEC site) where the PMF stillwater elevation on the Cedar River is approximately 20 ft above the ground surface.
Mature vegetation would not be completely inundated by the floodwaters near the highway. Therefore, the licensee concluded that the longest fetch length in the south direction would be 11,200 ft.
INFO INFORMATION NEED DESCRIPTION ACTION (POST-AUDIT)
NEED The licensee's wind-wave results for the corrected 6,250-mi2 drainage area for the various fetch directions are, based on a 2-year wind speed estimated by the licensee of 40 mph, were as follows (in feet):
Fetch PMF Stillwater Fetch Si bu I Wave Wave Total Total Elevation Wind WSE WSE Direction (NAVD88)
Length Setup Setup Run-up (NAVD88)
(MSL)
South 764.8 11,200 0.135 0.289 2.17 767.4 767.8 Southwest 764.8 10,000 0.122 0.276 2.06 767.3 767.7 Fetch PMF Stillwater Fetch Sibul Wave Wave Total Total Elevation Wind WSE WSE Direction (NAVD88)
Length Setup Setup Runup (NAVD88)
(MSL)
West 764.8 1,600 0.031 0.117 0.85 765.8 766.2 Northeast 764.8 6,400 0.083 0.228 1.69 766.8 767.2 East 764.8 3,600 0.053 0.174 1.28 766.3 766.7 Southeast 764.8 3,600 0.053 0.174 1.28 766.3 766.7 The NRG staff reviewed the licensee's response and found the response to include a detailed description of the wind-wave activity calculation associated with the higher stillwater WSE obtained from the revised PMF calculation. Upon review, the staff concluded that the licensee provided adequate justification for the selection of the longest straight-line fetch and that their approach was reasonable. No further action is necessary.
References cited:
USAGE 1984. "Shore Protection Manual, Volumes 1 and 2."
USA CE 2008. "Coastal Enqineerinq Manual," EM 1110-2-11.00 Part II.
INFO
.JNFO.RflATION NEED DESCRIPTION ACOON {POST-AUDIT)
NEED 9
Ice Jams: Potential Ice Jam Location In its FHRR, the licensee described the potential for In response to this information need request, the licensee noted that it had site flooding as a result of ice jams above and below considered ice jams at the Blairs Ferry Road bridge location.
the DAEC site. Based on its FHRR analysis, the licensee concluded that the current design basis The staff reviewed the licensee's response and found it acceptable. The staff bounds this particular flood hazard. However, when concluded that the licensee's approach had met the general intent of the 50.54(f) reviewing the description of the licensee's analysis, letter. No further action is necessary.
it is not clear whether the closest structure traversing the Cedar River to the DAEC site - the Blairs Ferry Road bridge - was considered as a potential location for the formation of an ice dam.
The staff requests the licensee clarify whether the Blairs Ferry Road bridge location was considered as a potential location for the formation of an ice dam for the purposes of the FHRR analysis.
Alternatively, if the site was considered, explain whether the flooding effects at this particular location could be discounted and thus are bounded by the current design basis flood elevation.
- via email OFFICE NRR/JLD/JHMB/PM NRR/JLD/JHMB/LA NRO/DSEA/RHM1fTM
- NRO/DSEA/RHM1/BC (A)
NAME LKGibson Slent RRivera-Luao CCook DATE 11/17/16 11/16/16 9/2/16 12/9/16 OFFICE NRR/JLD/JHMB/BC(A) NRR/JLD/JHMB/PM NAME GBowman LKGibson DATE 11/25/16 12/21/16