ML090540682

Response to Request for Additional Information Related to the License Amendment Request (LAR) for Implementation of Alternative Source Term

ML090540682
Person / Time
Site:	Mcguire, McGuire
Issue date:	02/12/2009
From:	Geer T Duke Energy Carolinas, Duke Energy Corp
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
Download: ML090540682 (16)

Text

THOMAS C. GEER Duker Vice President t'Energye Nuclear Engineering Duke Energy Corporation 526 South Church St.

Charlotte, NC 28202 Mailing Address:

EC08H / PO Box 1006 Charlotte, NC 28201-1006 704 382 4712 704 382 7852 fax tcgeer@duke-energy.corn February 12, 2009 U. S. Nuclear Regulatory Commission Washington, D.C. 20555 ATTENTION: Document Control Desk

Subject:

Duke Energy Carolinas, LLC (Duke)

McGuire Nuclear Station, Units 1 and 2 Docket Nos. 50-369 and 50-370 Response to Request for Additional Information Related to the License Amendment Request (LAR) for Implementation of Alternative Source Term (AST).

This letter provides the responses to the third and most recent request for additional information (RAI) regarding the AST LAR conveyed by the NRC staff via letter from Jon Thompson dated February 10, 2009 (Reference 4). The NRC staff's questions and Duke's responses are provided in Attachment 1. Duke is attaching two drawings to support the RAI responses. Due to the sensitive nature of the requested drawings, Duke Energy requests that these drawings be withheld from public disclosure pursuant to 10 CFR 2.390(d)(1).

The conclusions reached in the original determination that the LAR contains No Significant Hazards Considerations and the basis for the categorical exclusion from performing an Environmental/Impact Statement have not changed as a result of this request for additional information.

Please contact Lee A. Hentz at 704-875-4187 if additional questions arise regarding this license amendment request.

Sincerely, Thomas C. Geer Attachment www. duke-energy. com

U.S. Nuclear Commission February 12, 2009 Page 2 cc: w/attachment L. A. Reyes Regional Administrator, Region II U.S. Nuclear Regulatory Commission Sam Nunn Atlanta Federal Center 61 Forsyth St., SW, Suite 23T85 Atlanta, GA 30303 J. H. Thompson (addressee only)

Project Manager U.S. Nuclear Regulatory Commission Office of Nuclear Reactor Regulation Mail Stop 0-8 G9A Washington, D.C. 20555 J. B. Brady NRC Senior Resident Inspector McGuire Nuclear Station B. 0. Hall Section Chief Division of Radiation Protection Section 1645 Mail Service Center Raleigh, NC 27699

U.S. Nuclear Commission February 12, 2009 Page 3 OATH AND AFFIRMATION Thomas C. Geer affirms that he is the person who subscribed his name to the foregoing statement, and that all the matters and facts set forth herein are true and correct to the best of his knowledge.

Thomas C. Geer, Vice President Nuclear Engineering Subscribed and sworn to me: *)-92

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Date N6tary Public A/ &WW-i'59-My commission expires: ,41LU-?/ /, 'i//

U, Date

ATTACHMENT I REQUEST FOR ADDITIONAL INFORMATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION REGARDING PROPOSED LICENSE AMENDMENT REQUEST FOR IMPLEMENTATION OF ALTERNATIVE SOURCE TERM MCGUIRE NUCLEAR STATION, UNITS 1 AND 2

1. Section C.3.4 of Regulatory Guide (RG) 1.194, "Atmospheric Relative Concentrations for Control Room Radiological Habitability Assessments at Nuclear Power Plants," states that "Ifthe distance to the receptor is less than about 10 meters, the ARCON96 code and the procedures in Regulatory Position 4 should not be used to assess x/Q values.

These situations will need to be addressed on a case-by-case basis." (Regulatory Positions 4.1 to 4.3 of RG 1.194 are based on Murphy-Campe and Standard Review Plan Chapter 6.4). With regard to the calculation of x/Q values for releases from the main steam safety valves on the outboard doghouse (MSSVout), please provide a case-specific analysis that either recalculates the x/Q values, or that quantitatively demonstrates that the magnitude of the MSSVout values listed in Table B-3 of Appendix D of your response sent by letter dated December 17, 2008, are bounded by dilution effects resulting from case-specific factors. Such an analysis need not be limited to meteorological factors. For example, it may consider applicable case-specific engineering influences such as high energy flow rates, thermal buoyancy, and effects of steam flashing to atmospheric conditions, but should account for temporal changes and resultant dilution effects throughout the accident.

Duke Response Duke has reviewed the release locations originally submitted in Appendix B of the full scope Alternative Source Term (AST) License Amendment Request (LAR, Reference 1) and determined that this list can be shortened to the point sources below, and simplified. The revised list of release points to be considered for the full scope AST LAR are those associated with the LOCA analysis:

" Unit Vent (UV)

" Equipment Hatch (EQ)

• Refueling Water Storage Tank (FWST)

• Containment Purge Ventilation Intake'(VP) and the principal secondary system release locations:

• Steam Generator Power Operated Relief Valves (PORVin, PORVout)

• Main Steam Safety Valves (MSSVin, MSSVout)

• Auxiliary Feedwater Pump (Turbine Driven) discharge (AFW).

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The release points that are being removed from consideration are:

a Reactor Building (RX)

• Fuel Building (FUEL)

• Inboard and outboard doghouses (NDOG, ODOG, VNDOG, VODOG, AGin, and AGout)

The amount of data required for the review will be simplified by concentrating on the limiting (or bounding) release point and receptor combination(s) for each release location. This will reduce the number of verification cases required and reduce the size of Tables B-2 and B-3. The Unit Vent and Equipment Hatch models were previously submitted and reviewed as part of the Fuel Handling Accident (FHA) LAR, however, the Safety Evaluation Report (SER, Reference 2) placed restrictions on their use. These restrictions resulted from issues related to the meteorological data used in determining the dispersion factors submitted. No issues were identified in the SER related to the models. Thus, while EQ was modeled as both a point source and an area source, the dispersion factors computed were based upon the limiting case-the point source model (as stated in footnote "a" to Table B-2 in the original LAR and subsequent correspondence). Therefore, the EQ source is retained as a point source. All of the area sources have been removed from further consideration.

Additionally, Duke has reviewed the separation distance between the most limiting MSSV and the associated same unit control room intake location. It has been determined that this distance is greater than 10 meters. With the re-measured MSSV separation distance and the revision to the release locations under consideration, including the deletion of RX, the separation between sources and receptors for all release locations is now greater than 10 meters in this submittal. Thus, all modeling can be done employing ARCON96 for these points. With the changes communicated above in this response, the Murphy-Campe methodology that was the basis for Question 1 is no longer applied in this LAR.

Originally, the distances between the sources and receptors were determined using the sketch provided in Appendix A of the initial LAR package. This sketch was developed by importing data from a topographical "fly-over" into a computer aided design (CAD) code. However, the resulting image did not capture smaller site details such as these release points and receptor locations, which were subsequently plotted. Using a single sheet of paper allowed for a single source of data, and it provided the ability to easily measure the "cross-unit" source to receptor distances. However, the small scale associated with it induced a potential for error when measuring the relatively short distances associated with the same unit source and receptor combinations, particularly those associated with the outboard doghouse.

Full size plant drawings (see response to Question 3) and actual field measurements were used to more accurately determine the distances. Revised distances were applicable to MSSVin, MSSVout, PORVin, PORVout and the AFW release points. The dispersion factors for the release points used in the LOCA analysis were not impacted.

In summary, only the UV, EQ, FWST, VP, PORVin, PORVot, MSSVin, MSSVOut, and AFW release locations are being retained for the full scope AST LAR review. Because 2

of this change in the scope of release locations and the re-determined source to receptor distances, modeling of separations less than 10 meters and the treatment of area sources no longer apply to this submittal. Updated Tables B-2 and B-3 of the LAR package follow. Technical information which has changed has been bolded.

The information in Appendices A and C of Reference 3 is no longer applicable to this submittal.

Because the dispersion factors associated with the LOCA analysis are not changed, there is no impact on the computed doses.

The list of release points provided in this response and the following Tables B-2 and B-3 replace and supersede previously provided information associated with the dispersion factor review portion of this LAR package.

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Table B-2 McGuire Source Parameters for Table B-3 ARCON96 Limiting Case Dispersion Factors (sheet 1 of 2)

Source Type: EQ a I FWST UV VP PORVin PORVout MSSVin MSSVout AFW(')

Vertical Point , . x x x Horizontal or Capped Point Release Height 0m 14.6 m 40.2 m 9.5 m 18.9 m 18.9 m 18.8 m 18.8 m 15.5 m Flow Rate m3/s 0 m3/s 8.60 m 3/s 0 m3/s 0 m 3/s 0 m3/s 0 m 3/s 0 m 3/s 0 m 3/s (M3/s) 0r n86 Sigma-Y 0m 0Om 0m 0m 0m 0Om 0Om 0Om m0 Sigma-Z 0m 0m 0r 0m 0Om 0m 0Om 0Om m0 Bldg Cross- 1588 m 2 188.1 m 2 1588 m 2 1588 m 2 1588 m2 188.1 m 2 1588 m2 188.1 m 2 1588 m 2 sectional Area Source/Stack Radius (m) (b) 0m 0Om 0m 0m 0Om 0m 0Om 0 rn 0m Vertical Velocityi(c ) 0 m/s 0 r/s 0 rn/s 0 rn/s 0 rm/s 0 rn/s 0 m/s 0 rn/s Arc 32 marc 720arc Limitinq Case 17 m 54 rn 43m 59marc 39 m 23 m 35 m Distance 36marc Wind Direction 320 arc 620 620 2650 arc 670 410 790 520 Straight-line 29m 960 Limiting Case Unit 1 Unit 2 Unit 1 Unit 2 Source Unit 1 EQ Unit 2 FWST Unit 1 UV Unit 2 VP PORVinboard PORVoutboard MSSVinboard MSSVoutboard Unit 1 AFW Receptor Unit 1 Unit 2 intake Unit 1 Unit 2 Unit 1 intake Unit 2 intake Unit 1 intake Unit 2 intake Unit 1 intake intake intake intake 4

Table B-2 McGuire Source Parameters for Table B-3 ARCON96 Limiting Case Dispersion Factors (sheet 2 of 2)

Notes:

(a) Two source type runs were made for the equipment hatch: point source and receptor on the same unit and vertical area source and receptor on the same unit. The limiting case was with a point source and receptor on the same unit, representing a single hole in the hatch.

(b) Values of zero are assumed for the vertical velocity and the stack radius parameters, to treat the release as a ground-level release in ARCON96. Plume rise of the PORV and MSSV sources is NOT accounted for.

(c) Not used.

(d) Selected maximum x/Q for each time period for the AFW sources, comparing ARCON96 runs for straight line distances and arc-length distances (i.e. around the Reactor Building).

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Table B-3 McGuire Maximum (X/Q)s per Source (McGuire 2001-2005 Meteorology) 0-2 Hr 0-4 Hr 0-8 Hr 2-8 Hr 4-8 Hr 8-24 Hr 1-4 day 4-30 day EQ 4.09E-03 3.88E-03 3.73E-03 3.61 E-03 3.58E-03 1.72E-03 1.28E-03 9.99E-04 MIE1PTMx (arc)

FWST 1'84E-03 1.80E-03 1.75E-03 1.71 E-03 1.70E-03 8.09E-04 5.97E-04 4.62E-04 m2FWST2x_____

UV 1.69E-03 1.65E-03 1.59E-03 1.56E-03 1.53E-03 7.52E-04 5.68E-04 4.32E-04 ml1UVlx VP 1.58E-03 1.50E-03 1.38E-03 1.31E-03 1.26E-03 5.51E-04 4.20E-04 3.49E-04 m2VP2x (arc)

PORVin PORRin 3.03E-03 2.90E-03 2.81E-03 2.73E-03 2.72E-03 1.30E-03 9.57E-04 7.40E-04 mlPORVnl PORVout 6.71E-03 6.52E-03 6.23E-03 6.07E-03 5.94E-03 2.83E-03 2.17E-03 1.68E-03 m2PORVo2 MSSVin 3.56E-03 3.45E-03 3.32E-03 3.24E-03 3.19E-03 1.44E-03 1.09E-03 8.16E-04 mlMSSVnl MSSVout 9.70E-03 9.44E-03 9.04E-03 8.82E-03 8.64E-03 4.19E-03 3.20E-03 2.46E-03 m2MSSVo2 AFW ("a" = arc) 5.22E-03 4.92E-03 4.42E-03 4.16E-03 3.97E-03 1.92E-03 1.40E-03 1.07E-03 mlAFWNls mlAFWNls mlAFWNls mlAFWNls mlAFWNla mlAFWNIa mlAFWNla mlAFWNla

("s"=straight-line)

Receptor/source nomenclature lists the receptor first, followed by source. For example, "M1UVI" represents a release from the Unit 1 unit vent ("UVI") to the McGuire unit one control room area ventilation system inlet location ("MI").

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2. Based on a January 15, 2009, telephone conference between Duke and NRC staff, it is the NRC staff's understanding that Duke no longer requests approval of x/Q values associated with the reactor building surface. Please confirm that this is the case.

Duke Response As discussed in the response to Question 1 above, the Reactor Building surface release location (RX) will not be retained in the scope of the AST LAR. The changes to the requested review of release point locations are summarized below.

Release points retained for review in the full scope AST LAR:

UV, EQ, FWST, VP, PORVinboard, PORVoutboard, MSSVinboard, MSSVoutboard, and AFW.

Release points removed from review in the full scope AST LAR package:

RX, FUEL, NDOG, ODOG, VNDOG, VODOG, AGinboard, and AGoutboard.

3. Some of the locations identified in Figure 1 of Appendix B of your response sent by letter dated December 17, 2008, appear to be at different distances and/or directions than those listed in Table B-2 of Appendix D of your response. Please provide one or more additional figures with higher resolution which clearly highlight all release and receptor locations and from which distance, height and direction inputs can be reasonably approximated. When both an arc direction and a straight-line direction could apply, please clarify whether calculations were made for both cases and the limiting resultant x/Q values were listed in Table B-3 of Appendix D.

Duke Response Duke is providing two drawings which can be used to determine the separation between the various sources and the control room intakes on the same unit. Each drawing refers to one of the two nuclear units at McGuire. Due to the sensitive nature of the requested drawings, Duke Energy requests that these drawings be withheld from public disclosure pursuant to 10 CFR 2.390(d)(1).

As discussed in the response to Question 1, the use of these drawings mimics the process Duke used to re-determine the separation between these sources and receptors. The LOCA release poirts were not found to be affected, as these separations were similar to or greater than those previously determined. However, new distances were measured for the PORV, MSSV, and AFW release points. The dispersion factors for these secondary side release locations have been recomputed using the re-determined distances. These distances are reflected in the revised Table 7

B-2 included in the response to Question 1, above. All distances and directions in Table B-2 have been rounded to whole numbers.

In using these marked up drawings, it should be noted that:

" These drawings show the Auxiliary Building at the roof elevation. The penetration of the inlets through the roof are shown on the drawing, however, the actual inlet locations (each inlet has a "candy cane" shape) are approximately four feet from the penetration. Therefore, the actual inlet locations (two inlets per intake location) have been plotted using field data. The control room intakes are marked in green.

" All release points are indicated in purple. The most limiting PORV or MSSV location was used to compute the dispersion factor and, thus, has been indicated on the drawings. Inboard and outboard sources may connect with a different limiting inlet (at an intake location) on the same unit.

• Release locations not found on this drawing were plotted using data from other plant drawings.

• The arrangement of the PORVs is not uniform for all doghouses, so the plotted PORV location is not always the same relative to the MSSVs.

" The FWSTs are not shown on these drawings. Because the distance to the FWSTs is very large, they cannot be plotted (to scale) on these drawings. The (centerline of the) FWSTs are 75 feet north of plant grid coordinate FF (centerline of the Reactor Building). The centerline of the Unit 1 FWST is 200 feet west of plant grid coordinate 49. The centerline of the Unit 2 FWST is 200 feet east of plant grid coordinate 63.

" The release heights are provided in Table B-2.

• True North is indicated on each drawing as well as called North. The difference is 12 degrees 20 minutes.

As reflected in Tables B-2 (including footnote "d") and B-3 (in the case designations accompanying each dispersion value) in the response to Question 1, only the AFW dispersion factors were computed using both arc and straight-line distances/directions.

The maximum of the dispersion factors computed by these two model runs are reflected in Table B-3. The straight-line based model treatment was bounding for short-time periods and arc-length based model treatment was bounding for longer time periods.

Two of the sources (VP and EQ) were modeled using arc distances/directions. For releases from VP, arc-lengths and arc-directions were modeled to allow flow around the Reactor Building to reach the intake on the same unit. Due to the channeling of flow between the Reactor Building and the Turbine Building, an "arc wind direction" was selected to both push the plume to, and simultaneously pull it around, the Reactor Building to the intake. For the Unit 1 model, an arc wind direction of 108 deg arc was 8

used to pull the plume south and then push it west to the intake. For the Unit 2 model, an arc wind direction of 265 deg was used to pull the plume south and then push it east to the intake.

Releases from the equipment hatch were modeled from the middle of the hatch opening at ground level. The Unit 1 equipment hatch location prescribes that the plume arc around the Reactor Building to the intake, even if the release were modeled from the top of the equipment hatch. The Unit 2 equipment hatch is located inside the Equipment Staging Building, so this release point is modeled at the roll-up door entrance on the east side of the Equipment Staging Building.

All other release locations (PORVin, PORVout, MSSVin, MSSVout, UV, and FWST) were computed using straight-line distance/directions as reflected in the data supplied in Table B-2. Straight-line modeling was applied to the high velocity PORV and MSSV releases to reflect plume rise. The unit vent discharges near the top of containment. It is much taller than the other sources which makes its release plume more likely to travel over containment to the intake.

4. Question 6 of your response sent by letter dated December 17, 2008, discusses the control room air intake locations and auxiliary building roof elevation. Please clarify whether the heights of the control room air intakes are 3.6 meters above plant grade.

Were all of the source and receptor values input into the ARCON96 computer code with respect to their height above plant grade? If the height of the auxiliary building roof was factored into the ARCON96 inputs, how was this done and to which release locations does it apply?

Table B-2 of Appendix D of your response sent by letter dated December 17, 2008, lists non-zero initial sigma-y and sigma-z values for each of the following postulated release locations:

equipment hatch (EQ),

fuel building (FUEL),

inboard doghouse (NDOG),

inboard doghouse plus steam and feedwater line penetrations (VNDOG) outboard doghouse (ODOG),

outboard doghouse plus steam and feedwater line penetrations (VODOG), and reactor building surface (RX).

The NRC staff notes that the diffusion models incorporated in ARCON96 are Gaussian models that assume that the release is from a point source. When using ARCON96 for a point source, the initial sigma y and sigma z are both zero, which are the default values. Input of a non-zero initial sigma value identifies the release as a diffuse source.

Since ARCON96 is not able to directly calculate atmospheric dispersion factors for non-point sources, it uses each non-zero initial sigma value to determine the distance from the center of the real source to a virtual point source upwind of the real source.

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Regulatory Position 3.2.4.5 of RG 1.194, states that the height and width of the area source may be taken as the maximum vertical and horizontal dimensions perpendicuiar to the line of sight from the source center to the control room intake. These dimensions are used to calculate the initial sigma values which ARCON96 uses to calculate upwind virtual point sources. Regulatory Position 3.2.4.8, which discusses large louvered panels or large openings, states that application of the diffuse area source model would be appropriate when (1) the release rate from the building interior is essentially equally dispersed over the entire surface of the panel or opening and (2) assumptions of mixing, dilution, and transport within the building necessary to meet condition 1 are supported by the interior building arrangement.

Other than for the reactor building surface, please provide drawings showing the orientation of release with respect to the control room intake, describe the physical characteristics resulting in a diffuse release (e.g., louvered panel, array of vents) and further justify that it is appropriate to model each of the sources using the initial sigma-y and sigma-z values and distances and directions listed in Table B-2 of Appendix D of your response sent by letter dated December 17, 2008. Confirm that the other criteria discussed above have been met and that a release through another penetration (e.g., a single vent) would not result in more limiting X/Q values than from the diffuse source.

Duke Response The control room air intakes/inlets are 3.6 meters above plant grade.

The source/release heights were supplied to ARCON96 with respect to their height above plant grade. The height of the Auxiliary Building roof was not a factor in determining the release heights of the sources.

The receptor/inlets are 1.5 meters above the roof of the Auxiliary Building. The Auxiliary Building roof is represented in ARCON96 as the base elevation of the receptor/intake, because the intakes protrude above the roof in a "candy-cane" shape, with the inlets hooked over to face downward.

The height of the Auxiliary Building roof was incorporated by entering a value of "-2.1 in" as the "Elevation Difference," which is the base elevation difference between source and receptor. A negative value is entered since the base elevation of the receptor is greater than that of the sources (i.e. Auxiliary Building roof at the intakes is 767 ft elevation, while plant grade is 760 ft elevation).

A sensitivity test was performed to verify identical results for the case in which all heights would be taken with respect to plant grade (receptor height = 3.6 m and elevation difference = 0.0 in). This result has been confirmed by NRC staff.

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As discussed in the response to Questions 1 and 2, no area sources are retained in the list of release locations in the scope of the LAR review. Therefore, it is Duke's understanding that these drawings are no longer needed to respond to this question.

The limiting Equipment Hatch (EQ) release model is as a point source. Therefore, the sources retained for review are modeled as point sources with sigma-y and sigma-z equal to zero.

References

1. Letter from B. H. Hamilton (Duke) to U. S. Nuclear Regulatory Commission, License Amendment Request for Full Scope Implementation of the Alternative Source Term, March 20, 2008.

2. Letter from J. F. Stang (USNRC) to G. R. Peterson (Duke) McGuire Nuclear Station, Units I and 2, Issuance of Amendments Regarding Implementation of Alternative Source Term Methodology (TAC Nos. MC9746 and MC9747),

December 22, 2006 and enclosed Safety Evaluation Report.

3. Letter from B. H. Hamilton (Duke) to U. S. Nuclear Regulatory Commission, Response to Request for Additional Information relatedto the License Amendment Request for Implementation of the Alternative Source Term, December 17, 2008.

4. Letter from J. H. Thompson (USNRC) to B. H. Hamilton (Duke), Request For Additional Information (RAI) Regarding ProposedLicense Amendment Request For Implementation of Alternative Source Term, February 10, 2009.

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THIS PAGE IS AN OVERSIZED DRAWING OR FIGURE, THAT CAN BE VIEWED AT THE RECORD TITLED:

DWG. NO. MC-1209-04.00 "AUXILIARY BUILDING ARCHITECTURAL ROOF PLAN UNIT 1."

WITHIN THIS PACKAGE... OR BY SEARCHING USING THE D-01

THIS PAGE IS AN OVERSIZED DRAWING OR FIGURE, THAT CAN BE VIEWED AT THE RECORD TITLED:

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