ML14059A188

Request for Additional Information, Near-Term Task Force Recommendation 2.1, Flood Hazard Reevaluation Report

ML14059A188
Person / Time
Site:	Comanche Peak
Issue date:	03/07/2014
From:	Balwant Singal Plant Licensing Branch IV
To:	Flores R Luminant Generation Co
Singal B
References
TAC MF1099, TAC MF1100
Download: ML14059A188 (14)

Text

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 March 7, 2014 Mr. Rafael Flores Senior Vice President and Chief Nuclear Officer Attention: Regulatory Affairs Luminant Generation Company LLC P.O. Box 1002 Glen Rose, TX 76043

SUBJECT:

COMANCHE PEAK NUCLEAR POWER PLANT, UNITS 1 AND 2 - REQUEST FOR ADDITIONAL INFORMATION REGARDING FUKUSHIMA LESSONS LEARNED- FLOODING HAZARD REANALYSIS REPORT (TAC NOS. MF1099 AND MF1100)

Dear Mr. Flores:

By letter dated March 12, 2012, the U.S. Nuclear Regulatory Commission (NRC) issued a request for information pursuant to Title 10 of the Code of Federal Regulations, Section 50.54(f)

(hereafter referred to as the 50.54(f) letter). The request was issued as a part of implementing lessons-learned from the accident at the Fukushima Dai-ichi nuclear power plant. Enclosure 2 to the 50.54(f) letter requested licensees to perform a flood hazard reevaluation using present-day methodologies and guidance.

By letter dated March 12, 2013 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML13074A058), Luminant Generation Company LLC (the licensee) submitted a response to Enclosure 2, Required Response 2 of the 50.54(f) letter. The NRC staff has determined that additional information is needed to complete its review.

This request was sent to Mr. Tim Hope of your staff on February 19, 2014. Mr. Carl Corbin of your staff informed us on February 25, 2014, that a clarification call is not required and agreed to respond to the request by April 4, 2014.

R. Flores If you have any questions, please contact me at 301-415-3016 or via e-mail at Balwant.Singal@nrc.gov.

Sincerely, t.?w~~~~r~

Plant Licensing Branch IV-1 Manager Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket Nos. 50-445 and 50-446

Enclosure:

Request for Additional Information cc w/encl: Distribution via Listserv

REQUEST FOR ADDITIONAL INFORMATION FUKUSHIMA LESSONS LEARNED FLOODING HAZARD REEVALUATION REPORT LUMINANT GENERATION COMPANY LLC COMANCHE PEAK NUCLEAR POWER PLANT, UNITS 1 AND 2 DOCKET NOS. 50-445 AND 50-446 By letter dated March 12, 2012, the U.S. Nuclear Regulatory Commission (NRC) issued a request for information pursuant to Title 10 of the Code of Federal Regulations, Section 50.54(f)

(hereafter referred to as the 50.54(f) letter). The request was issued as a part of implementing lessons-learned from the accident at the Fukushima Dai-ichi nuclear power plant. Enclosure 2 to the 50.54(f) letter requested licensees to perform a flood hazard reevaluation using present-day methodologies and guidance.

By letter dated March 12, 2013 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML13074A058), Luminant Generation Company LLC (Luminant, the licensee) submitted a response to Enclosure 2, Required Response 2 of the 50.54(f) letter for Comanche Peak Nuclear Power Plant (CPNPP), Units 1 and 2. The NRC staff has determined that the following additional information is needed to complete its review.

Request for Additional Information (RAI)

RAJ 1: Local Intense Precipitation and Associated Site Drainage (Choice of Methods and Technical Rationale)

The CPNPP, Units 1 and 2 Flood Hazard Reevaluation Report (FHRR) local intense precipitation section includes discussions on methods used to perform the analysis. In the discussions, the licensee uses a 5-minute (min) 1-square mile (mi 2J (2.59-square kilometer (km 2 )) probable maximum precipitation (PMP) value of 6.25 inches (15.9 centimeter (em)) and a 15-min 1-mi2 (2.59 km 2 ) PMP value of 9.78 inches (24.8 em). In the Final Safety Analysis Report (FSAR) for CPNPP, Units 3 and 4 combined license application (Luminant, 2012), the 5-min 1-mi2 (2.59 km 2 ) PMP is reported as 6.3 inches (16.0 em), and the 15-min 1-mi2 (2.59 km 2 ) PMP is reported as 9.8 inches (24.9 em). The NRC staff has analyzed both sets of PMP values and determined that use of the Units 3 and 4 FSAR (Luminant, 2012) would produce higher peak discharge, according to the Rational Runoff Transformation Method (RRTM) and when used in the U.S. Army Corps of Engineers (USACE) Hydrologic Engineering Center Hydrologic Modeling System (HEC-HMS) for simulating Scenario 4. The effects of rounding could also result in higher water levels when using other runoff estimation methods and when analyzing other flooding hazards, such as stream and river flooding and dam failure flooding.

Enclosure

Also, the review of the FHRR indicates that for intervals not included in HMR 52 1 , evenly-split distribution of rainfall was provided (i.e. the 20-min cumulative rainfall total was estimated as the 15-min total plus one-third of the difference between the 30-min and 15-min totals).

a. With respect to uncertainty in estimating PMP values and proper assessment of flooding hazards using current methods, the NRC staff requests a justification and description of the technical rationale for the Units 1 and 2 FHRR that resulting in a lower flood hazard compared to the values presented in the Combined License Application (COLA) for Units 3 and 4 of the same site.

b. In order to determine the appropriate method to be used for the analysis related to the rainfall distribution, the NRC staff requests justification for the interpolation method used to determine PMP values at 5-min intervals for durations not reported in HMR 52 (i.e. 10-min, 20-min, 25-min, etc.). More specifically, the staff requests justification for not using other interpolation methods, such as non-linear interpolation, which could potentially have provided higher magnitudes of precipitation.

RAI 2: Local Intense Precipitation and Associated Site Drainage (Model Documentation and Input/Output Files)

The NRC staff requests electronic input/output files and other relevant digital data files for the following:

1) HEC-HMS model for surface flow modeling of the Local Intense Precipitation

{LIP) probable maximum flood (PMF)

2) Hydrologic Engineering Center River Analysis System (HEC-RAS) and HEC-Geo-RAS model for LIP PMF routing and peak water elevations

3) Digital Elevation Model (OEM) or other x-y-z data files used for surface modeling RAI 3: Local Intense Precipitation and Associated Site Drainage {Choice of Methods and Technical Rationale)

The NRC staff analyzed different temporal rainfall distributions and determined that a centered distribution produces higher peak discharge values compared to a descending distribution for a 6-hour {hr) LIP event. Compared to a descending distribution, the staff's analysis determined that a centered rainfall distribution using the Soil Conservation Service (SCS) Unit Hydrograph

{UH) method without rainfall losses results in 6.2 percent to 6.8 percent higher peak discharge values. An illustration of temporal PMP and discharge values for both distributions is shown in Figure 1 for Storage Area 21677. According to the staff's analysis, for the SCS UH Method including rainfall losses, peak discharge values using a centered distribution, range from 9.3 percent to 23.4 percent, higher than those from a descending distribution. An illustration of temporal PMP and discharge values for both distributions is shown in Figure 2 for Storage National Weather Service (NWS), 1982, "Hydrometeorological Report No. 52 (HMR No. 52):

Application of Probable Maximum Precipitation Estimates- United States East of the 105th Meridian,"

August 1982.

Area 21677. While a centered distribution appears to bound a descending distribution, other arrangements (such as a two-thirds distribution) may produce even higher water levels. Based on the review, the NRC staff requests for the following information:

a) Technical rationale for assuming a descending distribution for LIP analysis.

b) Documentation of any sensitivity analysis performed in analyzing the PMP, drainage discharge, and water levels associated with local intense precipitation flooding .

Comparison of Discharge and Rainfall Distribution for SCS UH Method (without rainfall losses) 1400 . - - - - - - - - - - - - - - - - - - - - - - - - - - - - . 7.0 14

~ 1200 .._-- =-P=-a= =-

- d-=s-= -= -g=-=- =- =-s-= -= -=-=-=- =- =- =- -

+--- =-=- =- =- =- =- = -=-=-=- =- =- =-

- = -=-=-=- =- =- =--+ 6.0 -.s::.:fl Ql Peak discharge= 1170 cfs u m c

1000 5.0

:.

.s::. c u 0

~  ;

0 800 4.0 ~Q.

CD

..... -~

N 600 ~~----------~~-------------+ 3.0 ~

I!!

c( ~

Ql 400 2.0 ~

m

-0

~

( /)

200 0

---"'"r- - - - - - - - - - -~!m~lll!ll!fft!!!!._ 0.0 1.0 ~

I!!

0 60 120 180 240 300 360 Time (minutes)

Licensee's hyetograph i:::::::=:::J Staffs hyetograph

- - - - Series3 - - - - Series6 Note: the discharge associated with the licensee's approach are displayed based on staff s reconstruction (values vary only slightly).

Figure 1: Comparison of temporal rainfall distributions and discharge using the SCS UH Method, without rainfall losses (see note at bottom of Figure 1)

Comparison of Discharge and Rainfall Distribution for SCS UH Method (with rainfall losses) 1400 - r - - - - - - - - - - - - - - - - - - - - - - - - - - . - 7.0

~

1200 P~-

a~_d.!._

s~-

h~-rg_e =_- 1_

34_

~_':!s_-_-_-_-_-_-_-_----HI- - --_-_-_-_-_-_-_-_-_-_ - _- _

-_-_-_-_-_-_-_--+ 6

.0 i

.J:.

& Peak discharge = 1125 cfs g

1000 5.0

:.

.J:. c:

u~  ;

0

~

,... 800 4.0 ~

,... Q.

<D

..... *~

N 600 ~~------------...-tr-------------+ 3.0 c..

"'~  !

~

Cl) 400 ---~,------------.H-..------------+ 2.0 5i Cl E I!

0 II) 200 --~-----------+ 1.0

~

.E 0 !lltE:t:r;~-..:1!:1;1!1~--- 0.0 0 60 120 180 240 300 360 Time (minutes)

Licensee's hyetograph t::=:::::J Staffs hyetograph

- - - - Series3 - - - - Series6 Note: the discharge associated with the licensee's approach are displayed based on staffs reconstruction (values vary only slightly).

Figure 2: Comparison of temporal rainfall distributions and discharge using the SCS UH Method, including rainfall losses (see note at bottom of Figure 2)

RAI 4: Local Intense Precipitation and Associated Site Drainage (Choice of Methods and Technical Rationale)

For Scenario 4 presented in the FHRR, the associated calculation package F-03 (Rizzo, 2013c2 )

mentions that culverts on the northwest and southwest sides of the vehicle barrier system (VBS) were assumed not to be blocked. This important modeling assumption is not mentioned in the FHRR. In order to determine the correct application of methods, the NRC staff requests that the licensee provide the technical rationale and assumptions implemented in the modeling of these culverts in a consistent manner.

RAI 5: Local Intense Precipitation and Associated Site Drainage (Choice of Methods and Technical Rationale)

The FHRR for CPNPP, Units 1 and 2 does not have a documented reference for data in the FHRR; instead the licensee cross-references the FSAR for CPNPP, Units 1 and 2 (referred to as Reference 2 throughout the FHRR) for various elevations. During the review, the NRC staff also noted some inconsistencies in the use of data within some of the calculation packages thus raising questions with regard to the accuracy and quality control used in ensuring that data and predicted water levels were properly maintained. As an example, Table 7-1 of calculation package F-03 (Rizzo, 2013c) appears to report peak water elevations in NAVD88, whereas the majority of the calculation package and FHRR describe elevations using NGVD29. With respect 2

Paul C. Rizzo Associates , Inc., "Comanche Peak Nuclear Power Plant, Units I & 2 Flooding Hazard Reevaluation Report," Revision 0 , Project No . 12-4891 , February 12, 2013 .

to the data presented in the FHRR and to address errors associated with reporting of elevation data, the NRC staff requests a clear verification of the data used in the FHRR for elevations.

The NRC staff also requests a description of the method used for extracting elevation data from topography maps, entering values into hydrologic models, and reporting peak water levels and plant grades in the FHRR in a consistent manner.

RAJ 6: Local Intense Precipitation and Associated Site Drainage (Choice of Methods and Technical Rationale)

The licensee has selected Scenario 4, which is the least conservative of the scenarios considered in the FHRR. The NRC staff also noted that the site characteristics, more specifically the weir coefficients used in the analysis, require further explanation. In order to address questions related to estimation of water levels using appropriate and current methods, the NRC staff requests the technical rationale for selection of:

a) Water levels resulting from Scenario 4 and the assumptions included in the HEC-RAS model for Scenario 4, the least conservative of the scenarios presented in the FHRR.

b) Site characteristics which justify the use of weir coefficients of 3.0, which calculation package F-03 (Rizzo, 2013c) states is a high value for the conditions simulated, in modeling storage area connections for Scenario 4.

RAJ 7: Local Intense Precipitation and Associated Site Drainage (Choice of Methods and Technical Rationale)

In calculation package F-01 (Rizzo, 2013a), the licensee states "the HMR52 program was used to obtain the 72-hour PMP storm analysis for comparison purpose only." The NRC staff requests documentation of the analysis used in the estimation of the 72-hour (hr) PMP for LIP and clarification on how HMR 52 program results for the 72-hr LIP storm were used and what comparisons were made.

RAJ 8: Local Intense Precipitation and Associated Site Drainage (Choice of Methods and Technical Rationale)

The FHRR in Section 3.2.1.4 states that the water levels on the Squaw Creek Reservoir (SCR) and the Safe Shutdown Impoundment (SSI) due to LIP are lower than the water levels in the SCR due to regional river flooding, as documented in the licensee's calculation packages.

Considering the significance of wind wave run up in estimation of flood levels and the low physical margin available between the peak UP-induced flood level under Scenario 4 and entry elevations of safety-related systems, structures, and components (SSCs), the NRC staff requests:

a) Clarification to determine whether wind wave runup was considered in the analysis of on-site flooding within the protected area (PA).

b) Information and analysis related to water depth, fetch length, wave height potential, and flooding potential for on-site flooding with wind effects.

RAI 9: Local Intense Precipitation and Associated Site Drainage (Choice of Methods and Technical Rationale)

As noted in the FHRR Section 4.3.2, an equipment ramp on the west face of the non-safety-related Turbine Building (TB) of Unit 2, which is at elevation of 809.3 feet (ft)

(246.67 meters (m)) NGVD29, could communicate the reevaluated effects of local intense precipitation flood water to the safety related Electrical Control Building at elevation 778 ft. The FHRR indicates that "the total volume of runoff that can accumulate in the lower Unit 2 TB sump and condenser pit elevations (i.e., elevation 759ft and lower) for the 6-hour duration of the Local Intense Precipitation event was determined to be less than the available capacity of these areas." Although not explicitly stated, the NRC staff assumes this conclusion is based on quantitative analysis of LIP Scenario 4.

The NRC staff requests that the licensee provide quantitative analyses of LIP flood-water inundation into the Unit 2 TB sump and condenser pit resulting from:

a. 6-hr duration LIP flooding Scenarios 1, 2, 3, and 4, as well as any new LIP flooding evaluations involving different PMP distributions.

b. The 72-hr duration LIP event.

In addition, the quantitative analyses should also state the level of flooding, if any, that occurs within the Electrical and Control Building due to water conveyance from the Unit 2 TB.

RAI10: Stream and River Flooding (Model Documentation and Input/Output Files)

The NRC staff requests electronic input/output and other relevant digital data files for the following:

1) HMR 52 programs for PMP analysis of the Squaw Creek and Paluxy River watersheds

2) HEC-HMS model for surface flow modeling of PMF

3) HEC-RAS and HEC-Geo-RAS model for PMF routing and peak water elevations Digital Elevation Model (OEM) or other x-y-z data files used for surface modeling

4) Land use map used for Curve Number estimation as included in Appendix B

5) Soil type map used for Curve Number estimation as included in Appendix B RAI 11: Stream and River Flooding (Model Documentation, Choice of Methods, and Technical Rationale)

a. As reported in calculation packages F-10 (Rizzo, 2013j) and F-11 (Rizzo, 2013k),

HEC-HMS model calibration for the Squaw Creek and Paluxy River watersheds used a meteorological model of SCS Storm, Type II. Since CPNPP is located very near the area of Storm Type Ill, the NRC staff requests a description of any

consideration given to a Type Ill distribution and a justification as to why a Type Ill distribution was not selected.

b. The NRC staff requests the technical rationale related to site characteristics for selecting the Manning's roughness coefficients n used in the HEC-HMS models for runoff estimation. In particular, the staff requests additional information on any sensitivity analysis used to calibrate the model to other precipitation and flow conditions that would have resulted in higher magnitudes. If no additional conditions were used for calibration, the staff requests justification as to why one observation was sufficient to determine the model calibration was satisfactory.

c. The NRC staff notes that the calibrated model includes a basin coefficient which may be conservative (typical range of 1.8 to 2.2 with lower values more conservative) and a peaking coefficient which may not be conservative (typical range of 0.4 to 0.8 with higher values more conservative). In order to determine the consistent use of appropriate parameters, the staff requests the technical rationale related to site characteristics for selecting Snyder's unit hydrograph transformation coefficients as used in the licensee's hydrologic modeling. The NRC staff also requests additional information on any sensitivity analysis used to calibrate the model to other precipitation and flow conditions.

d. Section 2.5.2 of the FHRR states "Additionally, for both the Squaw Creek and Paluxy River watersheds, consideration was given to a potential 50-year projected scenario with an assumed 5 percent increase in impervious area for each sub-basin." With respect to the Hierarchical Hazard Assessment (HHA) approach discussed in Section 3.2.2.2.1 of the FHRR, the staff requests the following:

i. Technical rationale for using a 5 percent increase in impervious cover for future projections, exclusively for Scenario 5 of the Paluxy River watershed runoff analysis.

ii. Justification for why this 5 percent assumption was not added to the least conservative scenario (Scenario 4) which the licensee selected.

iii. Justification for not applying this 5 percent assumption to any scenarios for the Squaw Creek watershed PMF considered by the licensee.

RAI12: Stream and River Flooding (Choice of Methods and Technical Rationale)

a. Calculation F-12 (Rizzo, 20131) describes the selection of 0.1 and 0.3 for contraction and expansion coefficients, respectively, for normal flowing cross-sections. The NRC staff requests the technical rational for the selection of values for contraction and expansion coefficients. Additionally, the staff requests a description of whether any changes in contraction or expansion coefficients were used for any cross-sections aside from those adjacent to bridges.

b. The NRC staff requests the technical rationale for the selection of Manning's roughness coefficient n values and any sensitivity analysis performed in selecting

these values for the channels and overbanks in HEC-RAS for the stream and river flooding analysis.

c. Compared to the FSAR for Units 3 and 4 (Luminant, 2012), the values for Manning's roughness coefficient included in the Units 1 and 2 FHRR are less conservative. The licensee has selected Scenario 4 which is the least conservative scenario and as such should describe how this justifies appropriate reevaluation of flood hazards at the site using current and appropriate methods.

The NRC staff requests the description of, and the technical rationale for, the assumptions included in the HEC-RAS model for Scenario 4.

RAI13: Stream and River Flooding (Choice of Methods and Technical Rationale)

The FHRR (Table 2.2) describes the service water intake structure (SWIS) operating deck elevation of 796ft (242.62 m) NGVD29 as a safety-related sse elevation with a peak flooding elevation for this structure (under scenario PF 4) of 795.03 ft (Table 3-3). However, in calculation package F-13 (Rizzo, 2013m), the licensee states that "overtopping of the operating deck of the SWIS at 796 ft for PF 1 will not flood the safety-related structures at the SWIS since the vertical face of the SWIS pump room continues to an elevation of 830 ft MSL [mean sea level)." To address this apparent inconsistency, the NRC staff requests:

a) Clarification of what the minimum safety-related elevation of the SWIS is and how flood water levels exceeding the 796ft (242.62 m) NGVD29 elevation of the SWIS operating deck would impact this safety-related SSC.

b) A description of how flooding as a result of scenarios that are more conservative than Scenario 4 would impact flooding of the SWJS. The NRC staff notes that peak surface water elevations for PMF Scenario PF 1 and SSI PMF Scenarios 1 and 2 exceed the 796 ft NGVD29 elevation of the SWIS operating deck.

RAI14: Combined Effects Flooding (Choice of Methods and Technical Rationale)

The NRC staff requests a description of any sensitivity analysis that was performed on the temporal distributions of the full PMP and 40 percent PMP used for antecedent conditions in the combined effects analysis. In particular, the staff requests additional information on whether rainfall distributions with higher proportions of rainfall toward the end of the antecedent event were considered.

RAI15: Combined Effects Flooding (Choice of Methods and Technical Rationale}

With consideration of the HHA (as presented in Section 3.2.8 of the FHRR), the NRC staff requests justification for selecting and reporting water levels resulting from Scenario PF 4 (which is a less conservative scenario and includes rainfall losses and no assumption for a future increase in impervious cover) in the FHRR for combined effects flooding. The staff also requests the technical rationale for the use of contraction and expansion coefficients, Manning's roughness coefficient n values, and Snyder transformation coefficients as used in HEC-HMS and HEC-RAS for Scenario PF 4.

RAI16: Combined Effects Flooding and Local Intense Precipitation (Choice of Methods and Technical Rationale)

As noted in the "Severe Weather Abnormal Procedure Simulation" section of the FHRR, backflooding to the Electrical & Control Building can occur within the Circulating Water System (CWS) when the discharge valve pathways are open for maintenance and the flood level reaches 778 ft. The response procedure simulation estimates that a total of 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> is required to reinstall equipment and preclude backflooding. It is further noted that for the combined event PMF (i.e., scenario PF 4) it will take 3.2 hrs for the SCR water level to rise from elevation 777ft (when response procedure begins) to 778ft. The NRC staff notes that although SCR peak flood elevations are lower for LIP flooding than for combined effects flooding, the rate of reservoir pool elevation rise is likely to differ between the different flooding mechanisms. In order to quantitatively assess flooding hazard to the CWS from the flooding of the SCR, the staff requests quantitative analyses of the time in which the SCR rises from 777 ft to 778 ft and the extent of CWS flooding, if any, as resulting from:

a. Combined effects flooding Scenarios PF 1, PF 2, PF 3, and PF 4, as well as any new combined effects flooding evaluations involving different PMP distributions

b. LIP flooding Scenarios 1, 2, 3, and 4, as well as any new LIP flooding evaluations involving different PMP distributions.

RAI17: Failure of Dams and Onsite Water Control/Storage Structures (Model Documentation and Input/Output Files)

The NRC staff requests electronic input/output files and relevant digital data files for the following:

1) HEC-HMS models for surface flow modeling of PMF

2) HEC-RAS and HEC-geoRAS model for PMF routing and peak water elevations

3) Digital Elevation Model (OEM) or other x-y-z data files used for surface modeling RAI18: Failure of Dams and Onsite Water Control/Storage Structures (Choice of Methods and Technical Rationale)

The NRC staff's review of calculation package F-14 (Rizzo, 2013n) identified some inconsistencies as to whether Fort Phantom Hill Dam and Hubbard Creek Dam were included in the analysis. Hence, the staff requests clarification on which dams were breached in the controlling dam failure scenario and the criteria used to select the dams included in the controlling dam failure analysis.

RAI19: Failure of Dams and Onsite Water Control/Storage Structures (Choice of Methods and Technical Rationale)

The licensee assumes downstream boundary conditions based on the results of the FSAR for Units 3 and 4, with total breach flow along the Brazos River of 6,730,000 cubic feet per second (cfs) (191 ,000 cubic meters per second (ems)) and a water level of 760.45 ft (231. 79 m)

NGVD29 at the foot of Squaw Creek Dam. A more recent revision of the FSAR for Units 3 and 4 includes a total breach flow of 8,380,000 cfs (237,000 ems) and water level of 768.03 ft (234.10 m) NGVD29 below Squaw Creek Dam. The NRC staff requests clarification on how these changes to the Units 3 and 4 FSAR are being addressed and what impact the changes may have on the dam failure analysis.

RAI 20: Hazard Input to the Integrated Assessment: Flood Event Duration Parameters The March 12, 2012, 50.54(f) letter, Enclosure 2, requests the licensee to perform an integrated assessment of the plant's response to the reevaluated hazard if the reevaluated flood hazard is not bounded by the current design basis. Flood scenario parameters from the flood hazard reevaluation serve as the input to the integrated assessment. To support efficient and effective evaluations under the integrated assessment, the NRC staff will review flood scenario parameters as part of the flood hazard reevaluation and document results of the review as part of the staff assessment of the flood hazard reevaluation.

The licensee has provided reevaluated flood hazards at the site including local intense precipitation flooding, probable maximum flooding on contributing watershed, flooding in streams and rivers, and flooding from breach of dams. The local intense precipitation flooding is reported to exceed the current licensing basis and subsequently the licensee has committed to perform integrated assessment.

The licensee is requested to provide the applicable flood event duration parameters (see definition and Figure 6 of the Interim Staff Guidance (ISG) JLD-ISG-2012-05, "Performing of an Integrated Assessment," dated November 30, 2012 (ADAMS Accession No. ML12311A214),

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. Please 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 21: Input to Integrated Assessment: Flood Height and Associated Effects The March 12, 2012, 50.54(f) letter, Enclosure 2, requests the licensee to perform an integrated assessment of the plant's response to the reevaluated hazard if the reevaluated flood hazard is not bounded by the current design basis. Flood scenario parameters from the flood hazard reevaluation serve as the input to the integrated assessment. To support efficient and effective evaluations under the integrated assessment, the NRC staff will review flood scenario parameters as part of the flood hazard reevaluation and document results of the review as part of the staff assessment of the flood hazard reevaluation.

The licensee has provided reevaluated flood hazards at the site including local intense precipitation flooding, probable maximum flooding on contributing watershed, flooding in streams and rivers, and flooding from breach of dams. The local intense precipitation flooding is

reported to exceed the current licensing basis and subsequently the licensee has committed to perform integrated assessment.

The March 12, 2012, 50.54(f) letter, Enclosure 2, requests the licensee to perform an integrated assessment of the plant's response to the reevaluated hazard if the reevaluated flood hazard is not bounded by the current design basis. The licensee is requested to provide the flood height and associated effects (as defined in Section 9 of ISG JLD-ISG-2012-05) that are not described in the flood hazard reevaluation report for mechanisms that trigger an Integrated Assessment.

This includes the following quantified information for each flooding 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 22: Input to the Integrated Assessment: Triggers for the Integrated Assessment The FHRR describes integrated assessment related actions as follows:

Since the current design basis for external flooding does not bound the reevaluated hazards, an integrated assessment will be performed.

The NRC staff requests the licensee to identify which flooding hazard mechanisms will be included in the integrated assessment.

ML14059A188

• Email dated 2/14/14 OFFICE NRR!DORLILPL4-1/PM NRR!DORLILPL4-1/LA NRO/DSEA/RHMB/BC* NRR/DORLILPL4-1/BC NRR!DORLILPL4-1/PM NAME BSingal JBurkhardt CCook MMarkley (FLyon for) BSingal DATE 3/5/14 3/5/14 2/14/14 3/7/14 3/7/14