L-PI-09-056, Supplement to License Amendment Request (LAR) to Revise the Loss of Coolant Accident (LOCA) and Main Steam Line Break (MSLB) Accident Dose Consequences Analyses and Affected Technical Specifications (TS)

Supplement to License Amendment Request (LAR) to Revise the Loss of Coolant Accident (LOCA) and Main Steam Line Break (MSLB) Accident Dose Consequences Analyses and Affected Technical Specifications (TS)

ML091210703
Person / Time
Site:	Prairie Island
Issue date:	05/01/2009
From:	Wadley M Northern States Power Co, Xcel Energy
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
L-PI-09-056, TAC MD9140, TAC MD9141
Download: ML091210703 (20)

Text

@ Xcel Energym MAY 0 1 2009 L-PI-09-056 10 CFR 50.90 U S Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Prairie Island Nuclear Generating Plant Units 1 and 2 Dockets 50-282 and 50-306 License Nos. DPR-42 and DPR-60 Supplement to License Amendment Request (LAR) to Revise the Loss of Coolant Accident (LOCA) and Main Steam Line Break (MSLB) Accident Dose Consequences Analvses and Affected Technical Specifications (TS) (TAC Nos. MD9140, MD9141)

Reference:

1. Nuclear Management Company, LLC (NMC) letter to US Nuclear Regulatory Commission (NRC), "License Amendment Request (LAR) to Revise the Loss of Coolant Accident (LOCA) and Main Steam Line Break (MSLB) Accident Dose Consequences Analyses and Affected Technical Specifications (TS)", dated June 26, 2008, Accession Number ML081790439.

2. Northern States Power Company, a Minnesota corporation, (NSPM) letter to US Nuclear Regulatory Commission (NRC), "Supplement to License Amendment Request (LAR) to Revise the Loss of Coolant Accident (LOCA) and Main Steam Line Break (MSLB) Accident Dose Consequences Analyses and Affected Technical Specifications (TS)",

dated March 16,2009, Accession Number ML090890180.

In Reference 1, NMC* submitted an LAR for the Prairie Island Nuclear Generating Plant (PINGP) Units 1 and 2 to revise the licensing basis LOCA and MSLB accident radiological dose consequences for PINGP as currently described in the Updated Safety Analysis Report (USAR) and revise TS 3.3.5, "Containment Ventilation Isolation Instrumentation",TS 3.4.17, "RCS Specific Activity", and TS 3.6.3, "Containment Isolation Valves". In Reference 2, NSPM provided supplemental information to support NRC Staff review of Reference 1. Pursuant to telephone calls with the NRC Staff on March 26, 2009, and April 2, 2009, NSPM provides additional information in Enclosure 1

• On September 22, 2008, NMC transferred its operating authority to NSPM, doing business as Xcel Energy. By letter dated September 3, 2008, NSPM assumed responsibility for actions and commitments previously submitted by NMC.

1717 Wakonade Drive East Welch, Minnesota 55089-9642 Telephone: 651.388.1 121

Document Control Desk Page 2 to this letter to support review of References 1 and 2. NSPM submits this supplement in accordance with the provisions of 10 CFR 50.90.

The supplemental information provided in this letter does not impact the conclusions of the Determination of No Significant Hazards Consideration and Environmental Assessment presented in the June 26, 2008 submittal as supplemented March 16, 2009.

In accordance with 10 CFR 50.91, NSPM is notifying the State of Minnesota of this LAR supplement by transmitting a copy of this letter and enclosure to the designated State Official.

If there are any questions or if additional information is needed, please contact Mr. Dale Vincent, P.E., at 651-388-1121.

Summarv of Commitments This letter contains no new commitments and no revisions to existing commitments.

I declare under penalty of perjury that the foregoing is true and correct.

Executed on MAY 0 1 2009 Mud&%

Michael D. Wadley Site Vice president, Prairie lslahd Nuclear Generating Plant Units 1 and 2 Northern States Power Company - Minnesota Enclosures (1) cc: Administrator, Region Ill, USNRC Project Manager, PINGP, USNRC Resident Inspector, PINGP, USNRC State of Minnesota NSPM Enclosure 1 By letter dated June 26, 2008, Northern States Power Company, a Minnesota corporation (NSPM), submitted a license amendment request titled, "License Amendment Request (LAR) to Revise the Loss of Coolant Accident (LOCA) and Main Steam Line Break (MSLB) Accident Dose Consequences Analyses and Affected Technical Specifications (TS)", ADAMS Accession Number ML081790439 for the Prairie Island Nuclear Generating Plant (PINGP). By letter dated March 16, 2009, NSPM provided supplemental information (ADAMS Accession Number ML090890180) to support Nuclear Regulatory Commission (NRC) review of this LAR. The NRC Staff has requested the following additional information to support review and approval of the LAR to revise LOCA and MSLB analyses. NRC questions are shown in bold.

Question (I):

With respect to Enclosure 1 of NSPMYsMarch 16,2009, response to the U.S.

Nuclear Regulatory Commission's (NRC's) request for additional information, Question 1, the NRC staff requires the following clarifications to complete its review of the LAR to revise LOCA and MSLB analyses and affected TS:

I. Page 2 of 19, Bullet 3: What are the height and width of the Shield Building with respect to determining that the initial sigma y input should be 6.1 meters and the initial sigma z input should be 6.3 meters? How much of the Shield Building is above the Auxiliary Building? How was 43.0 or 43.6 meters determined to be the appropriate height of release input to the ARCON96 calculations?

NSPM response:

a. For the evaluation of the Shield Building wall release point, the initial sigma y value is based on the Shield Building outside diameter of 120 ft and the initial sigma z value is based on the height of the top of the Shield Building dome (El 898 ft) above the Auxiliary Building roof (El 775 ft), which is 123 ft (898 ft - 775 ft).

Therefore, using the Regulatory Guide 1.I94 recommendation of dividing the applicable building dimensions by a factor of 6, the initial sigma values were obtained as follows:

Initial sigma y = 120 ft/6 = 20.0 ft (6.096 meters) lnitial sigma z = 123 ft/6 = 20.5 ft (6.248 meters)

Page 1 of 18 NSPM The initial sigma y and sigma z values were then rounded to 6.1 meters and 6.3 meters, respectively.

b. As shown above, 123 ft of the Shield Building is above the Auxiliary Building roof.

c. The height of release for the Shield Building wall release point is based on the elevation of the midpoint between the top of the Shield Building dome (El 898 ft) and the Auxiliary Building roof (El 775 ft), which is 775 ft + 123 ft/2 or 836.5 ft, rounded up to 837 ft.

The control room air intake XIQ values (determined in PINGP calculation GEN-PI-049) used a Shield Building wall release height of 142 ft based on the midpoint elevation of 837 ft and the ground floor elevation of 695 ft (i.e., 837 ft - 695 ft = 142 ft). The 1424 height was converted to 43 meters.

The control room inleakage receptor WQ values used a Shield Building wall release height of 143 ft based on the midpoint elevation of 837 ft and the plant grade elevation of 694 ft (i.e., 837 ft - 694 ft = 143 ft). The 1434 height was converted to 43.6 meters.

2. Page 3 of 19, Bullets 5 and 6: The Steam Generator (SG) Power Operated Relief Valve (PORV) and Main Steamline Break (MSL) direction inputs listed in Table 1 do not appear to match the graphical representation in the Attachment 1 figure in all cases. For example, the Unit 1 SG PORVs &

MSLB-Point to Unit 1 Control Room Air Intake input is listed as 180 degrees in Table 2, but appears to be about 155 degrees in the Attachment 1 figure.

Which inputs represent the closest valve and which represent the centroid of a group of valves? What are the dimensions and orientations of the groups of valves and the distance of the closest valve to each receptor?

NSPM response:

The locations of the Main Steam Safety Valves (MSSVs) and Steam Generator (SG)

Power Operated Relief Valves (PORVs) are shown in Attachment 1, with the Group 1 valves located just north and slightly west of the Unit 1 Shield Building and just north and slightly east of the Unit 2 Shield Building. As shown in the drawing, the valve groups are oriented in an east-west direction, with the Group 1 valves covering an east-west distance of approximately 24 ft and a north-south distance of approximately 8 ft.

There are five main steam safety valves and one PORV in each group as shown on the drawing.

The distances and directions for Unit 1 and Unit 2 MSSVsISG PORVs Group 1 releases to the Unit Iand Unit 2 control room air intakes were taken from the existing PlNGP calculation, determined from the closest valve. The 180-degree direction from the Unit 1 SG PORVs and MSLB-point to the Unit 1 control room air intake listed in Table 2 Page 2 of 18 NSPM of the March 16, 2009 request for additional information (RAI) response (ML090890180) was determined from the far western edge of the MSSVsISG PORVs Group 1.

The distance and directions for Unit 1 and Unit 2 SG PORVs and MSLB-point (i.e., point source) to the Unit 1 and Unit 2 control room air intakes were also taken from the existing PlNGP calculation to maintain consistency, even though the actual PORV release point is at the far end of the valve group. The distances and directions for Unit 1 and Unit 2 MSSVsISG PORVs and SG PORVs and MSLB-point to the control room inleakge point were based on the centroid of the valve groups given that the SG PORVs and MSLB-point is a point source and the MSSVsISG PORVs are essentially a point source given the very small value of the initial sigma y used in the PlNGP calculation.

The Attachment 1 figure in the March 16,2009 RAI response (ML090890180) shows a point representing the controlling SG PORVs and MSLB-point for the control room inleakage receptor.

The distances (meters) from the closest valve to each receptor are as follows:

Unit 1 Valve Group 1 Unit 2 Valve Group 1 Unit 1 CR' Air Intake 16.1 Unit 2 CR Air Intake 53.2 CR lnleakage2 29.0 1

Control Room 2

Values provided in response to this RAI, but not used in any calculation

3. Page 3 of 19, Bullet 7: What causes the Refueling Water Storage Tank releases through the louvers to be well mixed over the entire face of louvers per Regulatory Guide 1.194, "Atmospheric Relative Concentrations for Control Room Radiological Habitability Assessments at Nuclear Power Plants"? Do the planes of the exterior surfaces of the louvers face the control room and control room air intakes? Does M.U. in Table 5.2-1 in the June 26,2008 license amendment request mean "make-up"?

NSPM response:

a. The Refueling Water Storage Tank (RWST) for each unit includes a vent at the top of the tank which discharges into the cylindrical concrete structure which encloses the tank. Personnel access to the top of the tank is provided by a 4'-6" x 3' opening in the concrete enclosure which allows a path for released activity to be discharged into the Auxiliary Building Normal Ventilation System equipment room. With the normal ventilation system isolated due to the SI signal and the start of the Aux Building Special Ventilation System, there will be no forced air movement in the room other than any natural circulation or differential pressure induced flow between the room and the ductwork in the room. With no forced ventilation, the activity discharged from the RWST is assumed to be slowly distributed throughout the room. Some Page 3 of 18 NSPM activity is assumed to seep into the ventilation system supply duct through small openings since the ducts are not sealed. This activity will then mix with the air in the duct and be slowly dispersed though the louver and into the environment. No credit is taken for any mixing in order to reduce the concentration prior to release from the louvers. Because of this slow mixing of activity into the room and into the ductwork, releases are assumed to be well mixed by the time they reach the environment and leave the duct uniformly over the face of the louver. Therefore, the type of source that best represents this type of release would be a diffuse source as described in Regulatory Guide 1. I 94.

b. The planes of the exterior surface of the louvers for the supply to the Auxiliary Building Normal Ventilation system are perpendicular to the line-of-sight from the control room and the control room intakes but do not face the control room or air intakes. The exterior surfaces of the louvers face away from the control room. See Attachment 2 for a sketch of the location of the louvers relative to the control room.

c. Yes. The M.U. in Table 5.2-1 in the June 26, 2008 LAR means "Make-Up".

Question (2):

With respect to Enclosure I of NSPM's March 16,2009, response to the U.S.

Nuclear Regulatory Commission's (NRC's) request for additional information, Question 2, the NRC staff requires the following clarifications to complete its review of the LAR to revise LOCA and MSLB analyses and affected TS:

Numbered paragraphs 1 through 5: For the list of sourcelreceptor pairs evaluated, please provide either the calculations or all inputs and resultant atmospheric dispersion factors (XIQ values) for each sourcelreceptor pair.

NSPM response:

Below is a list of the releaselreceptor pairs evaluated in the ARCON96 analyses that encompass all of applicable combinations in order to determine the limiting control room doses:

1. Unit 1 and Unit 2 Shield Building Wall to the Unit 1 and Unit 2 Control Room Air lntakes and the Control Room lnleakage receptor (i.e., located at the center of the Control Room ceiling);

2 Release Points x 3 Receptors = 6 ReleaseIReceptor combinations

2. Unit 1 and Unit 2 Shield Building Stack to the Unit 1 and Unit 2 Control Room Air lntakes and the Control Room lnleakage receptor; Page 4 of 18 NSPM 2 Release Points x 3 Receptors = 6 ReleaseIReceptor combinations

3. Unit 1 and Unit 2 RWST Vent (i.e., the Auxiliary Building Make-up (M.U.) Air Intake Louver) to the Control Room lnleakage receptor; 2 Release Points x 1 Receptor = 2 ReleaselReceptor combinations (Note: Unit 1 and Unit 2 Control Room Air Intake receptors are not evaluated due to control room isolation prior to initiation of RWST back-leakage. RWST back-leakage is expected to start at initiation of the recirculation mode which at PlNGP is conservatively assumed to be at T=16.25 minutes, which is well after control room isolation at T = 2 minutes)

4. Unit 1 and Unit 2 MSSVsISG PORVs to the Unit 1 and Unit 2 Control Room Air lntakes and the Control Room lnleakage receptor (Note: Diffuse Source);

4 Release Points x 2 Receptors = 8 ReleaseIReceptor combinations (Note: Unit 1 & Unit 2 MSSVsISG PORVs, Valve Groups 1 and 2 to Unit 1 and Unit 2 Control Room Air Intakes) 2 Release Points x 1 Receptor = 2 ReleaseIReceptor combinations (Note: Unit 1 & Unit 2 MSSVsISG PORVs, Valve Group 1 only evaluated for Control Room lnleakage receptor as Valve Group 2 is located at the opposite end of the Shield Building away from the receptor. A greater distance between the release and receptor increases the dispersion of the release, thus reducing the XIQ values. Therefore, since Valve Group 1 is much closer to the control room receptors, it is the controlling release point. See Attachment 1 to this enclosure for the Valve Group locations.)

Total: 10 ReleaseIReceptor combinations

5. Unit 1 and Unit 2 SG PORVs (also utilized for the main steam line (MSL) break location) to the Unit 1 and Unit 2 Control Room Air lntakes and the Control Room lnleakage receptor (Note: Point Source).

2 Release Points x 3 Receptors = 6 ReleaseIReceptor combinations (Note: Unit 1 & Unit 2 SG PORVs, Valve Group 1 only evaluated for Unit 1 and Unit 2 Control Room Air lntakes and Control Room lnleakage receptor as Valve Group 2 is located at the opposite end of the Shield Building away from the receptors. A greater distance between the release and receptor increases the dispersion of the release, thus reducing the X/Q values. Therefore, since Valve Group 1 is much closer to the control room receptors, it is the controlling release point.)

Total: 30 ReleaseIReceptor combinations Page 5 of 18 NSPM The design inputs used in the ARCON96 WQ calculations for the above 30 release-receptor combinations are provided in Table 1. The resultant WQ values for the 30 release/receptor combinations are provided in Table 2.

Page 6 of 18

Enclosure 1 NSPM Table 1 ARCON96 Parameter Unit 1 Shield Bldg. Wall1 Unit 1 Shield Bldg. Wall1 Unit 2 Shield Bldg. Wall1 Unit 2 Shield Bldg. Wall1 Unit 1 Control Room Air Unit 2 Control Room Air Unit 1 Control Room Air Unit 2 Control Room Air Intake Intake Intake Intake MeteorologicalInformation:

Period of Meteorological Data 1993 - 1997 1993 - 1997 1993 - 1997 1993 - 1997 Lower Measurement Height 10.0 10.0 10.0 10.0 (m) I Upper Measurement Height 60.0 60.0 60.0 60.0 Wind Speed Units mlsec mlsec mlsec mlsec Meteorological Data File P193.met, P194.met, P193.met, P194.met, P193.met, P194.met, P193.met, P194.met, Names P195.met, P196.met, P195.met, P196.met, P195.met, P196.met, P195.met, P196.met, P197.met P197.met P197.met P197.met Default Information:

Surface Roughness Length 0.20 0.20 0.20 0.20 r ~ i n Direction d Window (deg I 90 I 90 I 90 I 90 az)

Minimum Wind Speed (mlsec) 0.5 0.5 0.5 0.5 Averaging Sector Width 4.3 4.3 4.3 4.3 Constant I I NSPM Table 1 - Continued ARCON96 Parameter Unit 1 Shield Bldg. Wall1 Unit 2 Shield Bldg. Wall1 Unit 1 Shield Bldg. Unit 1 Shield Bldg.

Control Room Inleakage Control Room Inleakage Stackl Unit 1 Control Stackl Unit 2 Control Meteorological Information:

Period of Meteorological Data 1993 - 1997 1993 - 1997 1993 - 1997 1993 - 1997 Lower Measurement Height 10.0 10.0 10.0 10.0 (m)

Upper Measurement Height 60.0 60.0 60.0 60.0 Wind Speed Units mlsec mlsec mlsec mlsec Meteorological Data File P193.met, P194.met, P193.met, P194.met, P193.met, P194.met, P193.met, P194.met, Names P195.met, P196.met, P195.met, P196.met, P195.met, P196.met, P195.met, P196.met, P197.met P197.met P197.met P197.met Source Information:

Release Type ground ground ground ground Release Height (m) 43.6 43.6 56.7 56.7 Building Area (mL) 2,176 2,176 2,176 2,176 Vertical Velocity (mlsec) 0.0 0.0 0.0 0.0 Stack Flow (mJlsec) 0.0 0.0 0.0 0.0 Stack Radius (m) 0.0 0.0 0.0 0.0 Default Information:

Surface Roughness Length 0.20 0.20 0.20 0.20 (m) I I I Wind Direction Window (deg I 90 90 90 90 az)

Minimum Wind Speed (mlsec) 0.5 0.5 0.5 0.5 Averaging Sector Width 4.3 4.3 4.3 4.3 NSPM Table 1 - Continued PlNGP Design Inputs Used to Determine ARCON96 xIQ Values for All Applicable ReleaselReceptor Combinations SourcelReceptor ARCON96 Parameter Unit 2 Shield Bldg. Unit 2 Shield Bldg. Unit 1 Shield Bldg. Unit 2 Shield Bldg.

Stack/ Unit 1 Control Stack/ Unit 2 Control Stack/ Control Room Stack1 Control Room Room Air Intake Room Air Intake Meteorological Information:

Period of Meteorological Data 1993 - 1997 1993 - 1997 1993 - 1997 1993 - 1997 Lower Measurement Height 10.0 10.0 10.0 10.0 (m)

Upper Measurement Height 60.0 60.0 60.0 60.0 (m)

Wind Speed Units mlsec mlsec mlsec mlsec Meteorological Data File P193.met, P194.met, P193.met, P194.met, P193.met, P194.met, P193.met, P194.met, Names P195.met, P196.met, P195.met, P196.met, P195.met, P196.met, P195.met, P196.met, P197.met P197.met P197.met P197.met Default Information:

Surface Roughness Length 0.20 0.20 0.20 0.20 I

(m)

Wind Direction Window (deg az)

I 1 90 I

90 I

90 90 I Minimum Wind Speed (mlsec) 0.5 0.5 0.5 0.5 Averaging Sector Width 4.3 4.3 4.3 4.3 Constant Initial Diffusion Coefficients (m) 1 0.00, 0.00 I

0.00, 0.00 I 0.00, 0.00 0.00, 0.00 I Page 9 of 18 NSPM Table I - Continued ARCON96 Parameter Page 10 of 18

Enclosure 1 NSPM Table I Continued PlNGP Design Inputs Used to Determine ARCON96 xIQ Values for All Applicable ReleaseIReceptor Combinations I 1 II1 ARCON96 Parameter Unit 1 MSSVslSG PORVs Group 21 Unit 1 Control Unit 1 MSSVslSG PORVs Group 21 Unit 2 Control

~oom Air Intake Unit 2 MSSVslSG PORVs Group 11Unit 1 Control

~oom Air Intake Unit 2 MSSVslSG PORVs Group 11 Unit 2 Control Room Air Intake Meteorological Information:

Period of Meteorological Data 1993 - 1997 1993 - 1997 1993 - 1997 1993 - 1997 Lower Measurement Height 10.0 10.0 10.0 10.0 (m)

Upper Measurement Height 60.0 60.0 60.0 60.0 (m)

Wind Speed Units mlsec mlsec mlsec mlsec Meteorological Data File P193.met, P194.met, P193.met, P194.met, P193.met, P194.met, P193.met, P194.met, Names P195.met, P196.met, P195.met, P196.met, P195.met, P196.met, P195.met, P196.met, P197.met P197.met P197.met P197.met Default Information:

Surface Roughness Length 0.20 0.20 0.20 0.20 (m)

Wind Direction Window (deg) 90 90 90 90 Minimum Wind Speed (mlsec) 0.5 0.5 0.5 0.5 Averaging Sector Width 4.3 4.3 4.3 4.3 Constant I I I I Page 11 of 18

Enclosure 1 NSPM Table 1 Continued ARCON96 Parameter Unit 2 MSSVslSG PORVs Unit 1 MSSVslSG PORVs Unit 1 MSSVslSG PORVs Unit 2 MSSVslSG PORVs Group 21 Unit 1 Control Group 21 Unit 2 Control Group I 1 Control Room Group 11 Control Room Room Air Intake Room Air Intake Inleakage Receptor Inleakage Receptor I Meteorological Information:

Period of Meteorological Data 1993 - 1997 1993 - 1997 1993 - 1997 1993 - 1997 Lower Measurement Height 10.0 10.0 10.0 10.0 (m)

Upper Measurement Height 60.0 60.0 60.0 60.0 Page 12 of 18 NSPM Table I Continued ARCON96 Parameter Page 13 of 18 NSPM Table I Continued PlNGP Design In1 Ieceptor Combinations SourcelReceptor Unit 2 SG PORVs & MSL Unit 2 SG PORVs & MSL ARCON96 Parameter Break-Point, Group I 1 Break-Point, Group I 1 Unit 1 Control ~ o o m Air Unit 2 Control Room Air Intake Intake Meteorological Information:

Period of Meteorological Data 1993 - 1997 1993 - 1997 Lower Measurement Height 10.0 10.0 (m) I Upper Measurement Height 60.0 60.0 mlsec mlsec Meteorological Data File P193.met, P194.met, P193.met, P194.met, Names P195.met, P196.met, P195.met, P196.met, P197.met P197.met

-~eceptorInformation:

Distance to Receptor (m) 53.0 13.0 Intake Height (m) 25.0 25.0 Elevation Difference (m) 0.0 0.0 Direction to Source (deg) 253 129 Default Information:

Surface Roughness Length 0.20 0.20

'ind~irection Window (deg) 90 90 Minimum Wind Speed (mlsec) 0.5 0.5 Averaging Sector Width 4.3 4.3 Constant I I Page 14 of 18 NSPM Table 2 PlNGP ARCON96 xIQ Values for All Applicable ReleaselReceptor Combinations Page 15 of 18 NSPM Table 2 - Continued PlNGP ARCON96 xIQ Values for All Applicable ReleaseIReceptor Combinations Unit 1CR Intake Note: Control Room Inleakage Receptor is located at the center of the Control Room ceiling Page 16 of 18 NSPM Question (3):

With respect to the June 26,2008, LAR:

Please provide a discussion that supplements Appendix H in the Prairie Island Updated Safety Analysis Report describing how the low population zone XIQ values were calculated and a historical perspective of their basis.

The NRC staff notes that the XIQ values for the I-4 and 4 30 day time periods were calculated to include a non-conservative reduction factor which appears to be outside of the scope of the Regulatory Guide 1.4 methodology.

NSPM response:

In Amendment 19 of the Final Safety Analysis Report (FSAR), dated July 17, 1972, Northern States Power company provided the Atomic Energy Commission (AEC) with additional information regarding the site meteorological program in Appendix H. This new appendix included updated information on the determination of X/Q values for design basis accidents. Table XIV of FSAR Appendix H, provided in Amendment 19, is the same Table XIV that is in Appendix H of the current PlNGP Updated Safety Analysis Report (USAR), with one possible exception discussed in Note 1, below.

The AEC Safety Evaluation Report (SER) for PINGP, dated September 28, 1972, Sections 2.3.3 through 2.3.6 provide the AEC discussion on the meteorological program and accident diffusion estimates. The information in these sections refers to Appendix H in the PlNGP FSAR. The AEC SER concluded in Section 2.3.6 that, ". . . the meteorological data provide an acceptable basis for a conservative evaluation of atmospheric diffusion for accidental and routine gaseous effluent releases from the plant."

The actual calculation of low population zone (LPZ) X/Q values is based on the information in PlNGP USAR Appendix H, Table XIV, "Prairie Island - Site Accident Dispersion Factors (sec/m3)". The LPZ distance for PlNGP is 1.5 miles as defined in PlNGP Updated Safety Analysis Report (USAR) Section 2.2.5. This distance converts to approximately 2,414 meters. PlNGP USAR Appendix H, Table XIV does not provide atmospheric dispersion factors for this exact distance so linear interpolation of the values provided was performed to obtain the correct X/Q values for the LPZ distance.

Linear interpolation provides conservative values as the linear line travels above the actual curve. The LPZ X/Q values in the June 26,2008 License Amendment Request were previously submitted to the NRC in the PlNGP License Amendment Request titled "Selective Scope Implementation of Alternate Source Term for Fuel Handling Accident Applied to Containment Technical Specifications", dated January 20, 2004 (ML040270067), which was approved by the NRC in a Safety Evaluation dated September 10,2004 (ML042430504).

Page 17 of 18 NSPM Note 1 - The X/Q value for 4-30 days at the 33,000 meter distance is shown as 2.06 x lo-' in the FSAR Appendix H, Amendment 19. The current USAR shows this value as 2.16 x 10-'which is assumed to be a typographical error. Additionally, this value is not used for determining the LPZ XIQ values and therefore would not impact any current analyses.

Page 18 of 18

Attachment 2*- Sketch of the Normal Aux Building Vent Supply Louver Locations

'Sketch is not to scale and is only intended for the purpose of demonstrating the approximate location of the supply louvers Approximate CR intake locations Unit 2 Unit 1 Normal Aux Building Vent (on Aux Bldg Roof)

Control Room Reactor Building Unit 2 AUX. BLDG. 755'4"