ML15100A366
| ML15100A366 | |
| Person / Time | |
|---|---|
| Site: | McGuire, Mcguire  |
| Issue date: | 04/09/2015 |
| From: | Juan Uribe Japan Lessons-Learned Division |
| To: | Andrews S Duke Energy Corp |
| References | |
| TAC MF3623, TAC MF3624 | |
| Download: ML15100A366 (9) | |
Text
1 NRR-PMDAPEm Resource From:
Uribe, Juan Sent:
Thursday, April 09, 2015 10:38 AM To:
Andrews, Sherry E (Sherry.Andrews@duke-energy.com)
Subject:
McGuire Nuclear Station-Fukushima 2.1 Flooding-FHRR Review RAIs Attachments:
McGuire RAIs Final-NRRO-Con Call Comm-03302015.docx Mrs. Andrews, By letter dated March 12, 2014, Duke Energy submitted its flood hazard reevaluation report (FHRR) for the McGuire Nuclear Station, Units 1 and 2 (Agencywide Documents Access and Management System (ADAMS) Accession Number ML14083A415). During its review, the NRC staff determined that additional information is necessary to complete its assessment of the licensees FHRR. As we discussed in our clarification call, the NRC staff requests that Duke provide a response within 60 days of this email.
The attached document contains the NRC staffs Request for Additional Information (RAI) letter. Should you have any questions, please do not hesitate to contact me.
Thanks JUAN F. URIBE PROJECT MANAGER NRR/JLD/JHMB 301-415-3809 l O-13F10 l Juan.Uribe@nrc.gov U.S. Nuclear Regulatory Commission
Hearing Identifier:
NRR_PMDA Email Number:
1982 Mail Envelope Properties (Juan.Uribe@nrc.gov20150409103700)
Subject:
McGuire Nuclear Station-Fukushima 2.1 Flooding-FHRR Review RAIs Sent Date:
4/9/2015 10:37:41 AM Received Date:
4/9/2015 10:37:00 AM From:
Uribe, Juan Created By:
Juan.Uribe@nrc.gov Recipients:
"Andrews, Sherry E (Sherry.Andrews@duke-energy.com)" <Sherry.Andrews@duke-energy.com>
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1 Request for Additional Information related to the Fukushima Lessons Learned Flood Hazard Reevaluation Report for the McGuire Nuclear Station, Units 1 and 2 (TAC Nos. MF3623 and MF3624)
By letter dated March 12, 2014, Duke Energy (Duke or the licensee) submitted its flood hazard reevaluation report (FHRR) for the McGuire Nuclear Station, Units 1 and 2 (Agencywide Documents Access and Management System (ADAMS) Accession Number ML14083A415).
During its review, the NRC staff determined that additional information is necessary to complete its assessment of the licensees FHRR. The following are NRC staffs Request for Additional Information (RAI).
RAI 1: Local Intense Precipitation (LIP) of Enclosure 2 of the 10 CFR 50.54(f) lists LIP as a flood causing mechanism that should be addressed in the FHRR. The LIP flood reevaluation provided in the FHRR for McGuire Nuclear Station (MNS)is based on a postulated 1-hour, 1-square-mileprobable maximum precipitation (PMP)with a front-peak-loaded distribution in 5-minute increments.
During its review, the staff noted that the licensee-postulatedLIP scenario may not produce conservative flood parameter estimates, because the event duration and rainfall distribution were not shown to be bounding based on the information provided.
Provide the following information:
a) Justification that the LIP analysis presented in the FHRR is bounding in terms of warning time, flood depth, and flood duration. This justification can include sensitivity analysis of LIP event duration to consider localized (one square mile) PMP events up to 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> in duration (e.g., 1-, 6-, 12-, 24-, 48-, 72-hour PMPs) and various rainfall distributions (e.g.,
center-loaded and others in addition to a front-loaded distribution). The evaluations could identify potentially bounding scenarios with respect to flood height, event duration, and associated effects.
b) A discussion on how the sensitivity results may affect the analysis for the on-site LIP with respect to the Standby Nuclear Service WaterPond flooding causing a possible backwater effect for the modeling of the on-site LIP.
RAI 2: LIP Figure 2.1.2-1 of the FHRR shows that the Lake Norman east embankments serve as the north and west boundary of the Integrated Catchment Model (ICM). However, the FHRR does not clearly describe how the north and west boundary of the LIP ICM model, nor the southern and eastern section of the model, was determined.
Provide additional information and discussion on the variations of the east embankment elevations extending from the Cowans Ford Dam to the intake embankmentby providing an elevation view and/or diagram depicting how the east embankment (east of the dam) elevation varies extending from the Cowans Ford Dam to the intake embankment. Provide this as well for the remaining eastern and southern boundaries, and provide an explanation for the decision used in selecting the boundaries of the LIP ICM model.
RAI 3: LIP Section 4.4 (Model Boundary Conditions) in the Calculation MNS-193049-017 (Analysis of Local Intense Precipitation) states that the hydrodynamic model boundary condition was modeled as Critical Condition allowing water to leave the 2-D Zone using broad crested weir equation
2 without energy loss. During its review, the NRC staff was unsure ifthe entire boundary of the ICM, including the dam embankments, is modeled as a weir or just the security barriers.
Clarify the following ICM model setup issues:
a) How the boundaries of the 2-D modeling domain were represented at dam embankments, security barriers, and topographical slopes, b) How any gaps between the barriers were treated, and c) To what extent has the analysis ensured that the computational representations of the boundary conditions are conservative in terms of its physical counterpart and its role with on-site flooding protection.
RAI 4: LIP During its review, the NRC staff noted that the FHRR Section 2.1.2 does not clearly explain how
- 1) the ICM model handles building roof drains and2) why some buildings and structures are not included in the mesh (e.g., the vicinity of the Cask Storage area).
Provide the following information related to the ICM modeling:
a) Provide justification pertaining towhy somestructures(circled in yellow in the following graphic) are not included in the mesh as boundaries to the flow and demonstrate and/or discuss the justification for this simplification.
b) Demonstrate and identify how and where the roof drainage empties directly onto the ground as it is not easily identifiable in the ICM model and its document nor the results.
c) Explain the three different cases identified in the ICM model as base, no exterior parapets, and ESPS Building.
3 d) Discuss the sensitivity to changes in water levels in the yard with respect to some buildings and structures not being included in the mesh and how this affects the conservatism of the results.
e) Discuss the adequacy of the mesh grid in terms of angle skewness and size transitions.
f) Identify the objects that are represented by the areas of very fine mesh grids scattered throughout the yard in the model and explain how the analysis of flow in these locations affects the model predictions of flow elevations and velocities.
g) Discuss the decision to exclude the parking lots south and north of the site yard from the 2-D model area and whether increased roughness and possible backwater effects created by the parking lot being full of vehicles affect site flood elevations.
RAI 5: LIP The FHRR Section 2.1.4 states that a group of 21 specified node points (locations of interest) were identified for monitoring the simulated LIP flood levels near the safety-related buildings and facilities. However, there is no description on why and how these node points were selected.
Explain how the 21 specified points were selected for monitoringsimulated LIP flood levels. If the specified points are different from the location of doors and openings to the safety-related structures and facilities, provide the simulated surface water elevations, velocities vectors, and inundation durations near the doors and openings.
RAI 6: Streams and Rivers of Enclosure 2 of the 10 CFR 50.54(f) lists flooding in streams and rivers as a flood causing mechanism that should be addressed in the FHRR. The licensee used the legacy HEC-1 hydrologic model to simulate two sets of inflow hydrographs from the upstream watershed to Lake Norman (one for verification and the other based on the PMP estimates for the reevaluation). During the review, the staff noted that the HEC-1 model was calibrated with the 1916 hurricane event. Reference Document 101_1992_Catawba-Wateree_PMF Study provides detailed information on the 1992 PMF study, including input for the HEC-1 hydrologic model. Table 7.4 of this document summarizes the calibration of the 1992 model with Hurricane Hugo. Water surface profiles and reservoir results for the 1916 hurricane and 1940 storm, used in the calibration and validation of the 2013 Catawba River Model, are provided in Calculations Document MNS-193049-018, Appendix C and state that the 1916 and 1940 flooding routing results from the 1992 HEC-1 Legacy Model and the 2013 Model provide a very reasonable comparison with the observed hydraulic performance from the respective flood event.
Provide justification on why the calibrated HEC-1 model for the pre-developed river condition with an old hurricane event is appropriate to use for simulating the future river PMF scenarios.
RAI 7: Streams and Rivers During the review of the HEC-1 watershed modeling, the NRC staff noted that the licensee adopted the Soil Conservation Service (SCS) unit hydrograph method which abstracts basin runoff from the given rainfall event based on the Antecedent Moisture Conditions (AMC), and selected AMC 2 moisture conditions.
Provide additional information or analysis that justifies the choice of AMC 2 conditions as appropriately conservative instead of the more conservative AMC 3.
4 RAI 8: Streams and Rivers Calculation Document MNS-193049-018section 5.2.1 states that, The Catawba River Model incorporates influences of bridges that cross the Catawba River and tributaries by adding additional cross sections [.] The bridge hydraulic influences were modeled using three cross sections: one channel cross section each at the upstream and downstream embankments of the bridge and one cross section at the bridge representing the constriction from abutments. HDR applied representative contraction and expansion coefficients at the bridge cross sections.
The same calculation package Appendix D-8 at the section Cross Section Edits - Bridges states that, Contraction and expansion coefficients added to each of the bridge reference cross sections (0.3 contraction and 0.5 expansion).
a) Define what is meant by applied representative contraction and expansion coefficients at the bridge cross sections and Contraction and expansion coefficients added to each of the bridge reference cross sections (0.3 contraction and 0.5 expansion). as stated in the above referenced calculation package.
RAI 9: Streams and Rivers The FHRR (p. 56) states that the CRM model was verified using the 1916 and 1940 storm events. During its review of the Calculation Document MNS-193949-018, the staff noted that the dams (Oxford, Cowans Ford, and Wylie) that did not exist at the time of the respective storms were not removed from the model, and that the model utilized an operational methodology to enforce that inflow is equivalent to outflow.No additional information or reference to this approach is provided in the calculation document.The staff also noted that the reevaluation of the PMFwater level in Lake Norman (esp., FHRR page 66 and Table 3-1) did not account for associated effects on the reservoir flooding.
Provide the following additional information:
a) Provide elaboration and discussion pertaining to the methodology used to model an unregulated flow (no existing three dams) with an operational method that includes the three dams.
b) Adjustment of the reevaluatedPMF-induced Lake Norman water levelwithapplicable associated effects (e.g., wind, debris, sedimentation), and updating the relevant FHRR sections (esp. Table 3-1) as this flood causing mechanism which would create higher flood level than that of the current design basis must be addressed in the Integrated Assessment.
RAI 10: Failure of Dams of Enclosure 2 of the 10 CFR 50.54(f) lists dam failures as a flood causing mechanism that should be addressed in the FHRR. During its review, the NRC staff noted that the licensee identified 10 major dams out of 130 upstream dams in the Catawba Riverbasin applicable to be used in the dam failure analysis.
5 Explain why the FERC approved PMF scenario is used in lieu of the reevaluated PMF scenario for the small dam cumulative volume impact calculations for the 10 dams listed in the Results and Conclusions section of the calculation package MNS-193049-015_Rev. 0 titled HHA-NID Volume Screening for Non-Duke Energy Dam Failures.
RAI 11: Failure of Dams During its review, the NRC staff found(FHRR page 71) that if all the storage volumes for the screened-out dams were instantaneously added to Lake Norman, the lake level would rise from elevation 760 ft to 761 ft mean sea level.However, no calculations for this estimation are provided. Provide the calculation for estimating the 1 ft increase in the Lake Norman flood elevation due to the instantaneous failure of upstream small dams that were screened out.
RAI 12: Failure of Dams During its review, the NRC staff noted that the reevaluated upstream dam failure floods could cause overflow-inducedbreaching of the east embankment section (adjoining the Intake Dike) of the concrete section of Cowans Ford Dam. However, the staff noted that the FHRR and calculation package do not clearly describe detailed information on this additional failure mode and its flooding impacts on the plant site.
Provide a description (indicated with flow paths on maps) that would clarify the locations and extents of the potential embankment overflow sections for the Cowans Ford East Bulkhead and Embankment, the West Rim Dike, and the Hicks Crossroads Dike.
RAI 13: Failure of Dams The licensee used the ICM 2-D model to evaluate the effects of overflow of the Cowans Ford Dam on the site inundation.The boundary conditions of the ICM model are adjusted to account for the specific flooding scenario (FHRR page 78). During its review of the Calculation MNS-193049-019, the staff noted that the licensee removed a boundary condition labeled as critical for the dam failure analysis. The staff also noted that the reevaluated dam failure flood elevation in Lake Norman (esp., FHRR p. 78 and Table 3-1) did not account for any associated effects on the reservoir flooding.
Provide additional information that document:
a) The reasons for the removal of the critical condition boundary on the eastern side of the model and how this affects the conservatism of the results (if any).
b) The differences between the LIP analysis and the on-site analysis for dam failure as they pertain to the changes in boundary conditions.
RAI 14: Failure of Dams The FHRR(page 78) states that the controlling external flooding event for the MNS site is a combined event of the Cowans Ford basin PMF and aseries of overtopping failures of two upstream dams and three downstream dams including the Cowans Ford Dam. During its review, the staff noted that the dam failure scenario without anovertopping failure of the Cowan Ford Dam which is downstream to the plant site could create a higher flood level in Lake Norman. This staff positionis consistent with the guidance described in JLD-ISG-2013-01 Section 4.2.9 (NRC, 2013b), where it provides amethod for considering cascading failure of dams upstream from the site only. The staff also noted that the above dam failure flood
6 reevaluation does not account for plausible associated effects (e.g., wind, debris, sediment) as well as the effects of a potential overtopping failure of the Cowans Ford Dam earth embankment section on site inundation.
Provide the justification for not considering the following three factors in the dam failure flood analyses in the FHRR Section 2.3 or not necessary based on conservatism in place:
- No-overtopping-failure of the Cowans Ford Dam.
- Applicable associated effects (e.g., wind, debris, sedimentation) on the Lake Norman flooding.
- The onsite flooding caused by a potential overtopping breach of the Cowans Ford earth embankment.
If the licensee performs anadditional dam failure flood analysis with the above three factors independently or jointly, the licensee is requested to update the relevant FHRR sections (esp.
Table 3-1) as this flood causing mechanism which would create higher flood level than that of the current design basis must be addressed in the Integrated Assessment. Also provide the electronic versions of input and output files for the additional analysis(if any) related to this RAI.
RAI 15: General Hazard Reevaluation The NRC developed JLD-ISG-2012-05 Guidance for Performing the Integrated Assessment for External Flooding (ADAMS Accession No. ML 2311A214) which describes to licensees methods acceptable to the NRC for performing the integrated assessment for external flooding as described in the 50.54(f) letter. Section 5.1 of this document states that: The hazard reevaluations performed under Recommendation 2.1 identify the external flood mechanisms applicable to a site. Before the licensee performs the integrated assessment, it should collect or review the flood height and associated effects for all applicable flood mechanisms from the hazard review for use in the integrated assessment.
With respect to the input that will be used to develop the integrated assessment, please provide the following:
a) Clarify which flood hazard mechanisms, and their combined and associated events if applicable, will be included in the Integrated Assessment.
b) Provide the applicable flood event duration parameters (see definition and Figure 6 of JLD-ISG-2012-05, associated with mechanisms that trigger an integrated assessment using the results of the flood hazard reevaluation. This includes (as applicable) the warning time the site will have to prepare for the event (e.g., the time between notification of an impending flood event and arrival of floodwaters on site) and the period of time the site is inundated for the mechanisms that are not bounded by the current design basis.
c) Provide the basis or source of information for the flood event duration, which may include a description of relevant forecasting methods (e.g., products from local, regional, or national weather forecasting centers) and/or timing information derived from the hazard analysis.
RAI 16: General Hazard Reevaluation Provide the flood height and associated effects (as defined in Section 9 of JLD-ISG-2012-05) that are not described in the flood hazard reevaluation report for mechanisms that trigger an
7 integrated assessment. This includes the following quantified information for each mechanism (as applicable):
Hydrodynamic loading, including debris; Effects caused by sediment deposition and erosion (e.g., flow velocities, scour);
Concurrent site conditions, including adverse weather; and Groundwater ingress.
RAI 17: Comparison of Reevaluated Flood Hazard with Design Basis The FHRR for the MNS provides a comparison of the reevaluated flood hazards with the current licensing basis. For the purposes of the FHRR, the parameter of interest is the current design basis.
Provide clarification for the inconsistencies identified in the FHRR with regard to the comparison of the reevaluated flood hazard to the current design basis and submit a revised hazard comparison consistent with the instructions provided in the 50.54(f) letter.