north anna, unit 3, combined license application srp 02.04 ... · water level of 288.9 ft navd88...

4DominionEugene S. GrecheckVice PresidentNuclear Development

Dominion Energy, Inc. • Dominion GenerationInnsbrook Technical Center5000 Dominion Boulevard, Glen Allen, VA 23060Phone: 804-273-2442, Fax: 804-273-3903E-mail: [email protected] May 3, 2011

SECURITY-RELATED INFORMATIONWITHHOLD UNDER 10 CFR 2.390

U. S. Nuclear Regulatory CommissionAttention: Document Control DeskWashington, D. C. 20555

Serial No. NA3-11-018RDocket No. 52-017

COL/DWL

DOMINION VIRGINIA POWERNORTH ANNA UNIT 3 COMBINED LICENSE APPLICATIONSRP 02.04.02: RESPONSE TO RAI LETTER 63

On April 7, 2011, the NRC requested additional information to support the reviewof certain portions of the North Anna Unit 3 Combined License Application(COLA). The responses to the Request for Additional Information (RAI)Questions are provided in Enclosures 1 and 2:

0

S

RAI 5574 Question 02.04.02-8RAI 5574 Question 02.04.02-9

Design Basis Flood LevelIntense Precipitation Drainage Map

This information will be incorporated into a future submission of the North AnnaUnit 3 COLA, as described in the enclosures.

Please contact Regina Borsh at (804) 273-2247 ([email protected]) if youhave questions.

Very truly yours,

Eugene S. Grecheck

ENCLOSURE 2 TO THIS LETTER CONTAINS SECURITY- RELATEDINFORMATION AND MUST BE PROTECTED ACCORDINGLY. UPON

SEPARATION OF ENCLOSURE 2, THIS LETTER IS DECONTROLLED.

SECURITY-RELATED INFORMATION - WITHHOLD UNDER 10 CFR 2.390 -DC)0oo n

SECURITY-RELATED INFORMATION - WITHHOLD UNDER 10 CFR 2.390

Serial No. NA3-11-018RSRP 02.04.02: Response to RAI Letter No. 63

of 2Enclosures:

1. Response to NRC RAI Letter No. 63, RAI 5574 Question 02.04.02-82. Response to NRC RAI Letter No. 63, RAI 5574 Question 02.04.02-9 (Security-

Related)

Commitments made by this letter:

1. Incorporate proposed changes in a future COLA submission.

COMMONWEALTH OF VIRGINIA

COUNTY OF HENRICO

The foregoing document was acknowledged before me, in and for the County andCommonwealth aforesaid, today by Eugene S. Grecheck, who is Vice President-Nuclear Development of Virginia Electric and Power Company (Dominion VirginiaPower). He has affirmed before me that he is duly authorized to execute and file theforegoing document on behalf of the Company, and that the statements in the documentare true to the best of his knowledge and belief.

Acknowledged before me this~ day of ,_ _

My registration number is 7/7 31r7 "and my

Notap P-U.i r wom" .IC

717MO7COMMOW un ft.AVG31. 2012

cc: U. S. Nuclear Regulatory Commission, Region IIC. P. Patel, NRCT. S. Dozier, NRCJ. T. Reece, NRC

ENCLOSURE 2 TO THIS LETTER CONTAINS SECURITY- RELATEDINFORMATION AND MUST BE PROTECTED ACCORDINGLY. UPON

SEPARATION OF ENCLOSURE 2, THIS LETTER IS DECONTROLLED.

SECURITY-RELATED INFORMATION - WITHHOLD UNDER 10 CFR 2.390


Enclosure 1

ENCLOSURE 1

Response to NRC RAI Letter 63

RAI 5574 Question 02.04.02-8

Page 1 of 3


Enclosure 1

RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION

North Anna Unit 3

Dominion

Docket No. 52-017

RAI NO.: 5574 (RAI Letter 63)

SRP SECTION: 02.04.02 - FLOODS

QUESTIONS for Hydrologic Engineering Branch (RHEB)

DATE OF RAI ISSUE: 04/07/2011

QUESTION NO.: 02.04.02-8

FSAR Revision 3 Section 2.4.2.2 Flood Design Considerations reports a design basisflood elevation that is 23.47 ft below the Unit 3 plant grade of 290.0 ft NAVD88. FSARRevision 3 Section 2.4.2.3 Effects of Local Intense Precipitation reports the maximumwater level of 288.9 ft NAVD88 for the local PMP. In order to meet the regulatoryrequirements stated in 10 CFR 52.79 and 10 CFR 100.20(c) Staff requests clarificationas to why the reported design basis flood elevation is lower than the maximum floodelevation from the local PMP, particularly noting that Regulatory Guide 1.59 indicatesthat severe local precipitation is a possible cause for worst site related flooding.

Dominion Response

FSAR Section 2.4.2.2, Flood Design Considerations, incorporates SSAR Section2.4.2.2 and supplements it with revised plant grade information based on the US-APWRfacilities. SSAR Section 2.4.2.2 defines the design basis flood level as the result of theprobable maximum flood (PMF) on Lake Anna that was produced by the probablemaximum precipitation (PMP) over the Lake Anna watershed. This terminology wasretained in FSAR Section 2.4.2.2.

Flooding due to local intense precipitation (local PMP) over the US-APWR site isaddressed separately in FSAR and SSAR Sections 2.4.2.3. In these sections, variousmultipliers are applied to the PMP parameters to reflect a shorter (more intense)duration and a significantly smaller site watershed area.

The Lake Anna PMF and the local PMP are significantly different with respect to theirmaximum water levels and characteristics. However, each has the ability to cause plant

Page 2 of 3

Serial No., NA3-11-018RDocket No. 52-017

Enclosure 1

flooding. The NRC question correctly identified that there is a contradiction and thepotential for confusion in the FSAR as to which water level elevation was appropriate forthe designation of the design basis flood level. Discussions held with the NRC Staffresulted in the agreement that the designated "design basis flood" level should beassociated with the highest potential water level since it represents the minimumfreeboard distance to plant grade level. This is consistent with the current FSARSection 2.0 Table 2.0-201, "Evaluation of Site/Design Parameters and Characteristics,"for the evaluation of Maximum Flood Level which states:

"The Unit 3 site characteristic value for maximum flood water level below designplant grade is due to the local probable maximum precipitation (PMP) flood. Asdescribed in Section 2.4.2, this value is 1.1 ft below design plant grade in thepower block area based on the local PMP flood water elevation of 288.9 ftNAVD88 (289.8 ft NGVD29) in this area. Therefore, the Unit 3 site characteristicvalue for maximum flood water level below design plant grade falls within (islower than) the DCD site parameter value."

Accordingly, FSAR Section 2.4.2.2 will be revised to reflect the minimum freeboardvalue of 1.1 feet above the design basis flood level and state that the design basis floodlevel is due to the local PMP. Also, because the PMF is no longer considered thedesign basis flood, the text in FSAR Sections 2.4.3 and 2.4.10 and Table 19.1-205 willbe revised to provide consistency with the design basis flood designation.

Proposed COLA Revision

FSAR Sections 2.4.2.2, 2.4.3 and 2.4.10 and FSAR Table 19.1-205 will be revised asshown on the attached mark-up.

Page 3 of 3

Serial No. NA3-11-018RDocket No. 52-017RAI 02.04.02-8Page 1 of 7

North Anna 3Combined License Application

Markup of North Anna COLA

The attached markup represents Dominion's good faith effort to show how the COLA will be revisedin a future COLA submittal in response to the subject RAI. However, the same COLA content maybe impacted by revisions to the DCD, responses to other COLA RAIs, other COLA changes, plantdesign changes, editorial or typographical corrections, etc. As a result, the final COLA content thatappears in a future submittal may be somewhat different than as presented herein.

Serial No. NA3-11-018RDocket No. 52-017 North Anna 3RAI 02.04.02-8 Combined License ApplicationPage 2 of 7 Part 2: Final Safety Analysis Report

of 249.14 ft NAVD88 (250 feet NGVD29) before the addition of Unit 3.The increased normal pool level improves water availability duringdrought conditions downstream of Lake Anna.

The sixth sentence of the seventh paragraph of this SSAR section is

supplemented as follows with information on the flood surcharge.

A flood surcharge of 14.75 feet above the normal pool level is providedfor flood storage.

Table 2.4-1 of this SSAR section is supplemented with information on theLake Anna storage allocation as shown in Table 2.4-1R.

2.4.2 Floods

NAPS COL 2.4(1) Replace the content of DCD Subsection 2.4.2 with the following.

The information needed to address DCD COL Item 2.4(1) is included inSSAR Section 2.4.2, which is incorporated by reference with thefollowing supplements.

2.4.2.2 Flood Design Considerations

The last paragraph of this SSAR section is supplemented as follows withinformation on the design plant grade elevation for Unit 3.

The design plant grade for Unit 3 safety-related components andstructures is at Elevation 290.0 ft NAVD88 (290.86 ft NGVD29) providing23.47-1.1 ft of freeboard above the design basis flooding level, which is

due to the local PMP.

2.4.2.3 Effects of Local Intense Precipitation

This SSAR section is supplemented as follows to show that local intenseprecipitation is discharged to Lake Anna and that safety-related

structures are located at elevations above the maximum water surfaceelevation produced by local intense precipitation.

The site layout, drainage facilities, and drainage areas are shown onFigure 2.4-201. Plant north for the US-APWR is oriented 217.54 degreesfrom true north. All directions presented in this subsection are referencedto plant north. The safety-related buildings with above grade entrances

consist of the reactor building, power source buildings (PS/Bs), the power

2-176 Revision 4 (Draft 04/25/11)TBD 2011



Part 2: Final Safety Analysis Report

NAPS COL 2.4(1)

NAPS ESP VAR 2.4-4

2.4.3 Probable Maximum Flood on Streams and Rivers

Replace the content of DCD Subsection 2.4.3 with the following.

The information needed to address DCD COL Item 2.4(1) is included inSSAR Section 2.4.3 which is incorporated by reference with the followingsupplements.

The third paragraph of this SSAR section is supplemented as follows withinformation on the revised Lake Anna PMF analysis incorporating theraised normal pool level.

The Lake Anna PMF analysis presented in the SSAR utilized a normalpool elevation of 249.14 ft NAVD88 (250.00 ft NGVD29). For the additionof the Unit 3 power reactor, the normal pool elevation has been raised by3 inches to an elevation of 249.39 ft NAVD88 (250.25 ft NGVD29). Theincreased normal pool elevation results in increased water availabilityduring drought conditions downstream of the Lake Anna Dam.

Because the normal pool elevation has been increased, another LakeAnna PMF analysis has been performed to reflect the new normal poolelevation. The modeling approach, calibration, and nearly all input datafrom the Lake Anna PMF model presented in the SSAR remain the samefor the present analysis. The input data for the starting water level andthe stage-discharge relationship have been revised to reflect the newnormal pool elevation. Additionally, the U.S. Army Corps of Engineers(USACE) computer program HEC-HMS (Reference 2.4-220) is used tocompute inflow and outflow hydrographs as well as Lake Anna waterlevels instead of the USACE Computer Program HEC-1 (SSARReference 14), which was used in the SSAR PMF analysis. HEC-HMSperforms the same function as HEC-1 and is an upgraded program thatmakes use of modern computer operating systems. All of themethodologies utilized in the SSAR HEC-1 analysis with the same inputdata are utilized in the present HEC-HMS analysis. For the HEC-HMSmodel, adjustments to two variables (the Coefficient Ratio and theRecession Ratio) were necessary due to revisions to input parameters forHEC-HMS. Those instances where alterations were required aredescribed in the following subsections. Otherwise, the input parametersdescribed in the SSAR are still valid for the present HEC-HMS analysisand are incorporated by reference.


Serial No. NA3-11-018RDocket No. 52-017 North Anna 3RAI 02.04.02-8 Combined License ApplicationPage 4 of 7 Part 2: Final Safety Analysis Report

Initially, the SSAR HEC-1 input parameters, without modification to thenormal pool elevation, were input into the HEC-HMS model. Asmentioned previously, minor adjustments were made to two inputvariables due to revisions to the input parameters. With these

adjustments, the HEC-HMS analysis produced results essentiallyidentical to the results produced in the SSAR HEC-1 analysis.

Then, the normal pool elevation (starting water level) and the

stage-discharge relationship were revised to reflect the raised normalpool for Lake Anna in the HEC-HMS analysis. The results of the presentHEC-HMS analysis indicate that with a 3 inch increase in the starting

water level, the maximum Lake Anna PMF still water level at Lake AnnaDam does not increase and remains at elevation 263.21 ft NAVD88(264.07 ft NGVD29). Because the still water level at the dam does notincrease above that level, the backwater and wind wave activity analysis

have not been revised.

The design basis f•loodin,,,, PMF elevation at the Unit 3 site is 266.53 ftNAVD88 (267.39 ft NGVD29). This elevation is 23.47 ft below the Unit 3design plant grade elevation of 290.0 ft NAVD88 (290.86 ft NGVD29) forsafety-related facilities, including the safety-related UHS SSCs. Becausethe design plant grade and operating deck for the UHS are more than

1.0 foot above the design basis flooding PMF elevation, the UHS iscapable of withstanding the PMF on streams and rivers without loss ofthe UHS safety functions.

2.4.3.2 Precipitation Losses

The second paragraph of this SSAR section is supplemented as follows

with information on precipitation losses used in the Lake Anna PMFmodel.

The HEC-1 precipitation loss coefficients listed in SSAR Table 2.4-11,

DKLTR, ERAIN, RTIOI, and STRKR, are defined as Initial Range,Exponent. Coefficient Ratio, and Initial Coefficient respectively inHEC-HMS. The Initial Range, Initial Coefficient and Exponent HEC-HMS

precipitation loss coefficients are defined exactly the same as theircounterpart HEC-1 coefficients. The exact same values for these HEC-1loss coefficients, used in the SSAR PMF analysis, were input into theHEC-HMS model for the present analysis. The Coefficient Ratio inHEC-HMS has a slightly different definition than RTIOL in HEC-1. An





NAPS COL 2.4(1) 2.4.10 Flooding Protection Requirements


The first paragraph of this SSAR section is supplemented as follows withinformation on the site grade elevation for Unit 3.

The design plant grade is at Elevation 290.0 ft NAVD88 (290.86 ftNGVD29) (a greater height above the maximum design basis Lake Annaflood level of 266.53 ft NAVD88 (267.39 ft NGVD29) than was assumedin the SSAR).

The first paragraph of this SSAR section is further supplemented asfollows with information to address slope embankment protectionfeatures for the Unit 3 intake structure.

NAPS ESP COL 2.4-9 The Unit 3 station water intake/fire pump house is located in a separateintake channel true west of the cove that houses the intake structurepump house for Units 1 and 2 as shown on Figure 2.4-204. The Unit 3intake channel area is separated from Lake Anna by an outer bermconstructed in the early 1980s. The top of the outer berm is at Elevation255.0 ft NAVD88 (255.86 ft NGVD29) and protects the Unit 3 intakechannel area from flood events up to the 100-year flood on Lake Anna,which has an estimated flood level at Elevation 254.14 ft NAVD88(255.0 ft NGVD29) (SSAR Reference 23). Flow from Lake Anna passesthough a multi-barrel culvert in the outer berm as shown onFigure 2.4-204. The Unit 3 station water intake/fire pump house and theintake channel area are protected from wind wave activity on Lake Annaby the outer berm, which has no visible indications of erosion or damagefrom wave activity. Rip-rap protection of the slope embankment at thepump house location is provided to prevent local runoff from eroding theembankment near this on-shore intake structure. It should be noted thatalthough protection is provided, the Unit 3 station water intake/fire pumphouse is not a safety-related structure.


I




NAPS COL 2.4(1) The second paragraph of this SSAR section is supplemented as followswith information to show that flood protection measures are not requiredfor the Unit 3 site.

A local PMP drainage analysis was performed assuming, conservatively,that all underground storm drains and culverts are clogged. Details of thelocal PMP analysis and the resulting flood levels are presented inSection 2.4.2.3. The maximum PMP water level in the power block areais predicted to be at Elevation 288.9 ft NAVD88 (289.8 ft NGVD29), whichis 1.1 ft below Elevation 290.0 ft NAVD88 (290.86 ft NGVD29), thedesign plant grade elevation for safety-related facilities. Thus, no Unit 3safety-related structure is subject to static or dynamic loading due toflooding a. a rFeult of dcign ba.ic fl... .v,,tc or any flood-producin-phenomena, including the local PMP events. No flood protectionmeasures are required for the Unit 3 site. Additionally, no technicalspecifications or emergency procedures are required to implement floodprotection activities.S

2.4.11 Low Water Considerations

Replace the content of DCD Subsection 2.4.11 with the following.


2.4.11.1 Low Flow in Streams

The third sentence of the second paragraph of this SSAR section issupplemented as follows with information on the Lake Anna operatingwater level.

With the addition of Unit 3, the lake is maintained at an operating waterlevel of 249.39 ft NAVD88 (250.25 ft NGVD29).

I

NAPS COL 2.4(1)

NAPS ESP VAR 2.4-4

2.4.11.4 Future Controls

This SSAR section is supplemented as follows with information on thewater budget analysis and calculated minimum water levels.

As indicated in Section 2.4.1, other than the required releases from theLake Anna Dam, the only other consumptive water use from Lake Annais the existing units. To determine the impact of Unit 3 on Lake Anna



NAPS COL 19.3(4) Table 19.1-205 External Events Screening and Site Applicability

SSAR/FSAR

SectionDispositionCategory Event Description

HydrologicEngineering

Flood fromProbableMaximumPrecipitation

FSAR The Unit 3 site drainage facilities and grading in the power2.4.2.3 block area provide evacuation of the runoff from the PMP

storm event. The design plant grade elevations forsafety-related buildings are located above the estimatedPMP water levels and grading is such that sheet flows androof drainage flow away from safety-related buildings.The maximum water level from a PMP event in the powerblock area, located plant north of the UHS, isElevation 288.9 ft NAVD88 (289.8 ft NGVD29), which is1.1 ft below the design plant grade elevation forsafety-related structures.Additionally, the Unit 3 PMP flows do not impact the Units 1and 2 site. No flood protection measures are necessary forthe Unit 3 site.

FSAR 2.4.3 The Lake Anna PMF analysis presented in the SSARutilized a normal pool elevation of 249.14 ft NAVD88(250.00 ft NGVD29). For the addition of the Unit 3 powerreactor, the normal pool elevation has been raised by 3inches to an elevation of 249.39 ft NAVD88 (250.25 ftNGVD29). Because the normal pool elevation has beenincreased, the Lake Anna PMF analysis was performed toreflect the new normal pool elevation. The deei'gn basisfleediRg-PMF elevation at the Unit 3 site is 266.53 ftNAVD88-7.39 ft NGVD29). This elevation is 23.47 ftbelow the Unit 3 design plant grade elevation of 290.0 ftNAVD88 (290.86 ft NGVD29) for safety-related facilities,including the safety-related UHS SSCs.

Screening and Applicability

Freq. SiteCriteria (/yr) Appl.

1,3 None No

1,3 None NoProbableMaximumFlood


Revision 4 (Draft 04/25/11)TBD 201119-76

north anna, unit 3, combined license application srp 02.04 ... · water level of 288.9 ft navd88...

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