ML033350516

Proposed Technical Specification Changes Implementation of Alternate Source Term Request for Additional Information

ML033350516
Person / Time
Site:	North Anna
Issue date:	11/20/2003
From:	Hartz L Virginia Electric & Power Co (VEPCO)
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
03-464A
Download: ML033350516 (31)

Text

VIRGINIA ELECTRIC AND POWER COMPANY RICHMOND, VIRGINIA 23261 November 20, 2003 U.S. Nuclear Regulatory Commission Serial No.

03-464A Attention: Document Control Desk NL&OS/ETS R1 Washington, D.C. 20555 Docket Nos. 50-338 50-339 License Nos. NPF-4 NPF-7 VIRGINIA ELECTRIC AND POWER COMPANY NORTH ANNA POWER STATION UNITS 1 AND 2 PROPOSED TECHNICAL SPECIFICATION CHANGES IMPLEMENTATION OF ALTERNATE SOURCE TERM REQUEST FOR ADDITIONAL INFORMATION In a letter dated September 12, 2003 (Serial No.03-464), Virginia Electric and Power Company (Dominion) requested amendments, in the form of changes to the Technical Specifications to Facility Operating Licenses Numbers NPF-4 and NPF-7 for North Anna Power Station Units 1 and 2, respectively. The proposed changes were requested based on the radiological dose analysis margins obtained by using an alternate source term consistent with 10 CFR 50.67. In an October 27, 2003 telephone conference call with the NRC Staff, additional information was requested regarding the meteorological data used to predict the dose consequence from a design basis accident.

The requested information, including the input data and analysis methodology and assumptions are included as attachments to this letter.

Due to the number of program and procedure changes necessary to implement these changes, we continue to request ninety days from the issuance date of the amendments to implement the Technical Specifications changes. If you have any further questions or require additional information, please contact Mr. Thomas Shaub at (804) 273-2763.

Very truly yours, Leslie N. Hartz Vice President - Nuclear Engineering Attachments

1.

Request for Additional Information

2.

Associated Sketches

3.

CD Containing Met Data Commitments made in this letter: None

cc:

U.S. Nuclear Regulatory Commission (cover letter only)

Region II Sam Nunn Atlanta Federal Center 61 Forsyth Street, SW Suite 23T85 Atlanta, Georgia 30303 Mr. J. E. Reasor, Jr. (cover letter only)

Old Dominion Electric Cooperative Innsbrook Corporate Center 4201 Dominion Blvd.

Suite 300 Glen Allen, Virginia 23060 Commissioner (cover letter only)

Bureau of Radiological Health 1500 East Main Street Suite 240 Richmond, VA 23218 Mr. M. J. Morgan (cover letter only)

NRC Senior Resident Inspector North Anna Power Station Mr. S. R. Monarque NRC Project Manager U. S. Nuclear Regulatory Commission One White Flint North 11555 Rockville Pike Mail Stop 8-H12 Rockville, MD 20852

SN: 03-464A Docket Nos.: 50-338/339 SN: 03-464A Docket Nos.: 50-338/339

Subject:

AST RAI Meteorological Data COMMONWEALTH OF VIRGINIA

)

)

COUNTY OF HENRICO

)

The foregoing document was acknowledged before me, in and for the County and Commonwealth aforesaid, today by Leslie N. Hartz who is Vice President - Nuclear Engineering of Virginia Electric and Power Company. She has affirmed before me that she is duly authorized to execute and file the foregoing document in behalf of that Company, and that the statements in the document are true to the best of her knowledge and belief.

Acknowledged before me this Lfday of 6L Lf k

cL4

, 2003.

My Commission Expires:

31, Z006.

Notary Public (SEAL)

Virginia Electric and Power Company North Anna Power Station Units 1 and 2 Proposed Technical Specification Changes Implementation of Alternate Source Term Request for Additional Information North Anna Power Station Units 1 and 2 Virginia Electric and Power Company (Dominion)

SN: 03-464A Docket Nos.: 50-338/339 NORTH ANNA ALTERNATIVE SOURCE TERM ARCON96 INPUTS, ASSUMPTIONS, MODELING OPTIONS AND RESULTS The inputs to ARCON96

[Reference 1] consisted of meteorological and dimensional/directional data. In some cases the output from ARCON96 was adjusted based upon wind speed statistical and PORV steam thermodynamic data. The inputs and modeling options used and the data used to make adjustments to the ARCON96 output are discussed below in separate sections.

1) ARCON96 INPUTS 1.1) METEOROLOGICAL DATA The first input required by the ARCON96 computer code is the site meteorological data.

The North Anna site meteorological data is collected according to the guidance found in Regulatory Guide 1.23.

Included with this letter is a CD with the raw meteorological data and the processed meteorological data ready for input into ARCON96.

The processed meteorological data is contained in the file "NA9701MET2".

The raw meteorological data is written to 5 files - one for each year from 1997 through 2001.

These file names are "North Anna 1997 Met Data.txt", "North Anna 1998 Met Data.txt",

"North Anna 1999 Met Data.txt", "North Anna 2000 Met Data.txt" and "North Anna 2001 Met Data.txt".

Also included on the CD for convenience are the ARCON96 input files.

1.2) DIMENSIONAL DATA The North Anna meteorological tower has its lower data collection sensors at 10.0 meters above grade and its upper data collection sensors at 48.4 meters above grade

[Reference 5].

After generating ARCON96 readable meteorological data the next input data developed was dimensional data. The dimensional data consisted of the horizontal distances between the source points and receptor points, the elevation above grade (271') of the source points and receptor points and the area of one of the containment buildings above grade.

The location of each receptor and source are marked on Sketch No. 1, which is an attachment to this letter. The location designations for the receptors and sources on Sketch No. 1 are as follows:

NCR - normal control room intake C4 - emergency control room intake close to column lines C and 4 C6 - emergency control room intake close to column lines C and 6 C10 - emergency control room intake close to column lines C and 10 C11 - emergency control room intake close to column lines C and 11 Ul - Unit 1 containment building Page 1 of 22

U2 - Unit 2 containment building V

- vent stacks A and B (vent stacks A and B are only 22' apart from each other)

El - Unit 1 equipment hatch E2 - Unit 2 equipment hatch P1 - Unit 1 PORVs P2 - Unit 2 PORVs Rl - Unit 1 RWST vent R2 - Unit 2 RWST vent EL - auxiliary building east louver WL - auxiliary building west louver Bi - Unit 1 primary ventilation blowout panel B2 - Unit 2 primary ventilation blowout panel The location and elevation of each receptor and source are displayed in Table 1. In Table 1 the locations were defined relative to the columns lines "C" and "9". That is, every receptor and source has an associated distance south of column line "C" and an associated distance east or west of column line "9". From these distances relative to columns lines "C" and "9", the horizontal distance between each source-receptor pair was calculated and is shown in Table 1.

The grade of the station is elevation 271' and the heights of each source and receptor above this elevation are also included in Table 1.

Sketch No. 2 shows the filter housings and intake ducting for the two F41 emergency control room fans. The intakes for these fans draw air from the turbine/service building air volume. One intake is close to column lines C and 10. The other intake is close to column lines C and 6.

Sketch No. 3 shows the filter housing and intake ducting for the Unit 1 F42 emergency control room fan. The intake takes suction on the Unit 1 air conditioning chiller room and not on the turbine/service building air volume. The air conditioning chiller room is within the control room concrete envelope (but not the control room pressure envelope) and communicates with the turbine/service building air volume via an exhaust fan and intake louver. The chiller room intake louver were was modeled as the intake point into the control room envelope for the Unit 1 F42 fan. This intake point is referred to as the C4 receptor because of its proximity to column lines C and 4. See the assumptions section for more information about the selection of the intake point.

Sketch No. 4 shows the filter housing and intake ducting for the Unit 2 F42 emergency control room fan. The intake takes suction on the Unit 2 air conditioning chiller room and not on the turbine/service building. The air conditioning chiller room is within the control room concrete envelope (but not the control room pressure envelope) and communicates with the turbine/service building air volume via an exhaust fan and intake louver. The chiller room intake louver was modeled as the intake point into the control room envelope for the Unit 2 F42 fan.

This intake point is referred to as the Cl1 receptor because of its proximity to column lines C and 11.

See the assumptions section for more information about the selection of the intake point.

Page 2 of 22

According to Regulatory Guide 1.194 [Reference 3] the containment buildings will create wake effects as a function of their cross sectional areas. The wake effect of a large building increases the dispersion of any airborne effluents. In these ARCON96 runs only the cross sectional area of a single containment building is used. The cross sectional area of this containment building was computed in accordance with Regulatory Guide 1.194 [Reference 3].

This means that only the portion of the containment building above grade is considered. The outer radius of the dome portion of the containment building is 65.5' and the outer radius of the right circular cylinder portion of the containment building is 67.5'. The bend line where the transition between the right circular cylinder and hemisphere occurs is at elevation 342'. This makes the cross sectional area of the hemispherical dome (PI*R*R/2) or 6739.1 square feet or 626.1 square meters. The cross sectional area above grade of the right circular cylinder portion of the containment is ((342'-271')*67.5*2) or 9585 square feet or 890.5 square meters. The total cross sectional area of one of the containment buildings above grade is 626.1 square meters plus 890.5 square meters or 1516.6 square meters.

Distances from the containment buildings to the receptors were calculated by treating the point on the cylinder of the outside wall of the containment that was closest to the receptor as the source.

1.3) DIRECTIONAL DATA The ARCON96 code requires the compass direction of the source point relative to the receptor point for each run. Expressed another way, this is the compass heading a person is facing when they are at the receptor and are looking at the source. This angle was calculated using the coordinates of the source and the coordinates of the receptor relative to column lines "C" and "9". This calculation was done for each source-receptor pair. The results of this calculation for each source receptor pair is shown in Table 1.

Included in these calculations is a correction for true north. The "Called North" arrow shown in Sketch No. 1 is for local references on site. The buildings on site are aligned 36 degrees off of true north by protractor measurement. Therefore, a 36-degree correction is incorporated into each source-receptor compass heading calculation.

Page 3 of 22

SN: 03-464A Docket Nos.: 50-338/339 TABLE 1 - ARCON96 INPUTS LOCATION Elevation Meters Feet (grade elev 271')

Point Sources (feet) above South arade of C Feet Feet Meters meters Meters Meters meters Degrees Degrees Degrees Degrees Degrees East West To to To To to norm from NCR from from From from Of 9 of 9 C-4 C-11 C-1.0 C-6 intake intake to C-4 to C-11 to C-10 to C-6 to Unit 1 PORV A 339.00 20.73 117.58 129.08 37.66 70.29 57.79 35.76 22.39 192.08 162.64 84.51 90.88 125.57 Unit 1 PORV C 339.00 20.73 117.58 140.58 36.69 73.33 60.63 37.01 19.92 185.33 157.45 83.12 88.89 120.42 Unit 1 PORV B 339.00 20.73 117.58 153.50 35.98 76.79 63.90 38.76 17.57 175.65 151.34 81.69 86.87 115.07 Unit 2 PORV C 339.00 20.73 117.58 153.25 104.38 43.86 52.81 82.09 103.80 225.71 214.01 179.55 192.95 209.59 Unit 2 PORV B 339.00 20.73 117.58 140.33 100.69 41.70 49.91 78.52 99.91 225.39 213.24 175.14 189.98 208.40 Unit 2 PORV A 339.00 20.73 117.58 128.83 97.42 40.00 47.45 75.37 96.44 225.08 212.51 170.84 187.04 207.25 U1 RWST vent 335.56 19.68 134.00 234.50 45.38 101.22 87.84 58.32 25.26 106.23 117.72 77.70 80.86 95.87 U2 RWST vent 335.56 19.68 134.00 234.50 129.42 64.67 75.81 106.86 129.04 225.10 215.68 195.01 202.43 212.64 Vent Stack B 386.75 35.28 7.50 78.00 27.69 45.03 30.68 4.28 37.21 263.98 229.58 56.72 56.11 229.07 Vent Stack A 386.75 35.28 7.50 56.00 34.38 38.34 23.98 10.98 43.15 259.52 230.44 56.70 56.70 232.08 Ul blowout panel 322.50 15.70 177.83 15.50 71.40 59.95 54.30 57.25 61.16 200.98 184.80 118.37 131.66 168.04 U2 blowout panel 322.50 15.70 161.67 33.21 78.72 50.36 48.23 60.82 71.97 210.76 195.39 131.28 147.85 182.86 E Aux Bld louver 301.22 9.21 119.73 50.00 51.25 51.47 41.69 36.87 43.65 213.04 188.85 98.91 111.95 164.32 W Aux Bld louver 301.22 9.21 119.37 50.00 75.84 36.72 36.20 55.33 72.91 221.72 205.46 134.64 157.35 195.47 Ul Equip Hatch 298.42 8.36 259.63 143.56 79.35 102.27 92.98 78.80 59.53 155.88 149.52 104.56 111.00 132.50 U2 Equip Hatch 298.42 8.36 231.22 191.79 130.42 79.58 86.40 110.37 124.75 210.57 201.37 171.91 180.65 195.60 Diffuse Sources Siama-Y Sigma-Z Ul Cont Center 1192.50 136.50 l l 59.33 85.85 75.23 58.35 40.45 164.86 153.49 96.97 103.87 130.56 Ul Cont Wall 6.858m 6.143m l

l_

l_38.76 65.28 54.66 37.78 19.87 l

}

U2 Cont Center 192.50 136.50 109.87 61.97 67.19 89.84 104.67 212.83 201.82 163.21 175.12 194.82 U2 Cont Wall 6.858m 6.143m 89.30 41.40 46.61 69.27 84.10 l

Receptors C-4 ECR Intake 265.00

-1.83 l

0.50 168.58 l

C-11 ECR intake 265.00

-1.83 1 0.50 69.58 C-10 ECR intake 292.00 6.40 3.79 22.58 C-6 ECR intake 286.92 4.85 l

6.29 92.00 l

Normal CR intake 294.25 7.09 J 68.50 183.75 l

Meters Meters Meters Above Below Below Grade Grade Grade to NCR to C-4 to C-1I meters Meters above Above grade Grade to C-10 to C-6 I

Ul 1 7.09 1 -1.83

-1.83 1

6.4 1 4.71 U2 l

7.09 l -1.83 l -1.83 6.4 4.71 Lower met tower instrument level - 10.04 m Upper met tower instrument level - 48.43 m Containment area above grade - 1516.6 sq. m Page 4 of 22

1.4) WIND SPEED STATISTICAL DATA According to Regulatory Guide 1.194 [Reference 3], releases from atmospheric relief valves which release effluent vertically at high velocity without obstruction qualify for a reduction in the atmospheric dispersion factors computed by ARCON96. This reduction by a factor of five is permitted as long as the vertical velocity of the effluent is at least five times the speed of the wind at the elevation of the release.

These ARCON96 runs modeled the six PORVs on top of the main steam valve house as sources. During a release from these PORVs the effluent stream would be propelled at a very high velocity straight up from these PORVs. To apply the factor of 5 reduction to the atmospheric dispersion factors for the PORVs the vertical velocity of the effluent stream has to be 5 times greater than the upper 9 5 th percentile wind speed at the height of the PORVs. Thus, the 9 5 th percentile wind speed at the height of the PORVs has to be computed from the meteorological data and the vertical velocity of the effluent flow has to be computed from the thermodynamics of the release.

The calculation of the 95th percentile wind speed at the height of the PORVs was done using a SAS program. The output from the SAS code is shown in Table 2 and Table 3.

Table 2 shows that the upper 9 5th percentile wind speed at the 33' level of the meteorological tower is 5.1 meters per second and Table 3 shows that the upper 9 5th percentile wind speed at the 159' level of the meteorological tower is 7.3 meters per second. The tops of the PORV exhaust stacks are 68' above the ground or an elevation of 339'.

If you interpolate between the two 9 5th percentile wind speeds, the 9 5th percentile wind speed at the 68' level is 5.72 meters per second.

Page 5 of 22

Table 2 Results of SAS Wind Speed Statistics Code 1997-2001 NORTH ANNA LOW WIND SPEED FREQUENCY DISTRIBUTION OF WIND SPEED AT 33 FEET CUMULATIVE CUMULATIVE WINDSLO FREQUENCY PERCENT FREQUENCY PERCENT 0.1 3

0.0 3

0.0 0.2 24 0.1 27 0.1 0.3 87 0.2 114 0.3 0.4 361 0.8 475 1.1 0.5 560 1.3 1035 2.4 0.6 691 1.6 1726 4.0 0.7 895 2.1 2621 6.1 0.8 1569 3.7 4190 9.8 0.9 1294 3.0 5484 12.8 1

1356 3.2 6840 16.0 1.1 1274 3.0 8114 18.9 1.2 1361 3.2 9475 22.1 1.3 2085 4.9 11560 27.0 1.4 1328 3.1 12888 30.1 1.5 1347 3.1 14235 33.2 1.6 1342 3.1 15577 36.3 1.7 1832 4.3 17409 40.6 1.8 1177 2.7 18586 43.4 1.9 1152 2.7 19738 46.1 2

1174 2.7 20912 48.8 2.1 1658 3.9 22570 52.7 2.2 1037 2.4 23607 55.1 2.3 1047 2.4 24654 57.5 2.4 1022 2.4 25676 59.9 2.5 1412 3.3 27088 63.2 2.6 908 2.1 27996 65.3 2.7 815 1.9 28811 67.2 2.8 848 2.0 29659 69.2 2.9 768 1.8 30427 71.0 3

1107 2.6 31534 73.6 3.1 718 1.7 32252 75.2 3.2 675 1.6 32927 76.8 3.3 622 1.5 33549 78.3 3.4 896 2.1 34445 80.4 3.5 525 1.2 34970 81.6 3.6 558 1.3 35528 82.9 3.7 486 1.1 36014 84.0 3.8 668 1.6 36682 85.6 3.9 414 1.0 37096 86.6 4

383 0.9 37479 87.4 4.1 368 0.9 37847 88.3 4.2 526 1.2 38373 89.5 4.3 331 0.8 38704 90.3 4.4 321 0.7 39025 91.1 4.5 296 0.7 39321 91.7 4.6 396 0.9 39717 92.7 4.7 211 0.5 39928 93.2 4.8 208 0.5 40136 93.6 4.9 207 0.5 40343 94.1 5

215 0.5 40558 94.6 5.1 273 0.6 40831 95.3 5.2 147 0.3 40978 95.6 5.3 158 0.4 41136 96.0 5.4 137 0.3 41273 96.3 Page 6 of 22

Table 2 (continued)

Results of SAS Wind Speed Statistics Code 1997-2001 NORTH ANNA LOW WIND SPEED FREQUENCY DISTRIBUTION OF WIND SPEED AT 33 FEET CUMULATIVE CUMULATIVE WINDSLO FREQUENCY PERCENT FREQUENCY PERCENT 5.5 184 0.4 41457 96.7 5.6 116 0.3 41573 97.0 5.7 91 0.2 41664 97.2 5.8 88 0.2 41752 97.4 5.9 123 0.3 41875 97.7 6

63 0.1 41938 97.8 6.1 79 0.2 42017 98.0 6.2 63 0.1 42080 98.2 6.3 91 0.2 42171 98.4 6.4 48 0.1 42219 98.5 6.5 47 0.1 42266 98.6 6.6 46 0.1 42312 98.7 6.7 35 0.1 42347 98.8 6.8 59 0.1 42406 98.9 6.9 35 0.1 42441 99.0 7

35 0.1 42476 99.1 7.1 25 0.1 42501 99.2 7.2 33 0.1 42534 99.2 7.3 20 0.0 42554 99.3 7.4 19 0.0 42573 99.3 7.5 24 0.1 42597 99.4 7.6 26 0.1 42623 99.4 7.7 9

0.0 42632 99.5 7.8 13 0.0 42645 99.5 7.9 10 0.0 42655 99.5 8

33 0.1 42688 99.6 8.1 12 0.0 42700 99.6 8.2 9

0.0 42709 99.6 8.3 9

0.0 42718 99.7 8.4 19 0.0 42737 99.7 8.5 10 0.0 42747 99.7 8.6 7

0.0 42754 99.8 8.7 8

0.0 42762 99.8 8.8 5

0.0 42767 99.8 8.9 17 0.0 42784 99.8 9

3 0.0 42787 99.8 9.1 5

0.0 42792 99.8 9.2 4

0.0 42796 99.9 9.3 5

0.0 42801 99.9 9.4 5

0.0 42806 99.9 9.5 2

0.0 42808 99.9 9.6 3

0.0 42811 99.9 9.7 5

0.0 42816 99.9 9.8 1

0.0 42817 99.9 9.9 2

0.0 42819 99.9 10 3

0.0 42822 99.9 10.1 5

0.0 42827 99.9 10.2 3

0.0 42830 99.9 10.4 2

0.0 42832 99.9 10.5 4

0.0 42836 99.9 10.6 1

0.0 42837 99.9 10.7 4

0.0 42841 100.0 10.8 1

0.0 42842 100.0 10.9 1

0.0 42843 100.0 Page 7 of 22

Table 2 (continued)

Results of SAS Wind Speed Statistics Code 1997-2001 NORTH ANNA LOW WIND SPEED FREQUENCY DISTRIBUTION OF WIND SPEED AT 33 FEET CUMULATIVE CUMULATIVE WINDSLO FREQUENCY PERCENT FREQUENCY PERCENT 11.1_________2___0.0_______42845_________100.0_______

11.1 2

0.0 42845 100.0 11.2 4

0.0 42849 100.0 11.4 2

0.0 42851 100.0 11.5 1

0.0 42852 100.0 11.6 1

0.0 42853 100.0 11.7 1

0.0 42854 100.0 11.8 1

0.0 42855 100.0 11.9 2

0.0 42857 100.0 12 1

0.0 42858 100.0 12.1 1

0.0 42859 100.0 12.2 1

0.0 42860 100.0 Page 8 of 22

Table 3 Results of SAS Wind Speed Statistics Code 1997-2001 NORTH ANNA HIGH WIND SPEED FREQUENCY DISTRIBUTION OF WIND SPEED AT 159 FEET CUMULATIVE CUMULATIVE WINDSHI FREQUENCY PERCENT FREQUENCY PERCENT 0.1 1

0.0 1

0.0 0.2 6

0.0 7

0.0 0.3 5

0.0 12 0.0 0.4 44 0.1 56 0.1 0.5 65 0.2 121 0.3 0.6 142 0.3 263 0.6 0.7 179 0.4 442 1.0 0.8 453 1.1 895 2.1 0.9 386 0.9 1281 3.0 1

452 1.1 1733 4.0 1.1 496 1.2 2229 5.2 1.2 519 1.2 2748 6.4 1.3 866 2.0 3614 8.4 1.4 592 1.4 4206 9.8 1.5 700 1.6 4906 11.4 1.6 675 1.6 5581 13.0 1.7 1073 2.5 6654 15.5 1.8 762 1.8 7416 17.3 1.9 756 1.8 8172 19.1 2

775 1.8 8947 20.9 2.1 1237 2.9 10184 23.8 2.2 808 1.9 10992 25.6 2.3 812 1.9 11804 27.5 2.4 857 2.0 12661 29.5 2.5 1250 2.9 13911 32.5 2.6 822 1.9 14733 34.4 2.7 825 1.9 15558 36.3 2.8 877 2.0 16435 38.3 2.9 862 2.0 17297 40.4 3

1223 2.9 18520 43.2 3.1 851 2.0 19371 45.2 3.2 817 1.9 20188 47.1 3.3 779 1.8 20967 48.9 3.4 1215 2.8 22182 51.8 3.5 804 1.9 22986 53.6 3.6 757 1.8 23743 55.4 3.7 757 1.8 24500 57.2 3.8 1141 2.7 25641 59.8 3.9 722 1.7 26363 61.5 4

735 1.7 27098 63.2 4.1 692 1.6 27790 64.8 4.2 1046 2.4 28836 67.3 4.3 653 1.5 29489 68.8 4.4 674 1.6 30163 70.4 4.5 608 1.4 30771 71.8 4.6 909 2.1 31680 73.9 4.7 559 1.3 32239 75.2 4.8 540 1.3 32779 76.5 4.9 507 1.2 33286 77.7 5

491 1.1 33777 78.8 5.1 704 1.6 34481 80.5 5.2 412 1.0 34893 81.4 5.3 453 1.1 35346 82.5 5.4 350 0.8 35696 83.3 Page 9 of 22

Table 3 (continued)

Results of SAS Wind Speed Statistics Code 1997-2001 NORTH ANNA HIGH WIND SPEED FREQUENCY DISTRIBUTION OF WIND SPEED AT 159 FEET CUMULATIVE CUMULATIVE WINDSHI FREQUENCY PERCENT FREQUENCY PERCENT 5.5 569 1.3 36265 84.6 5.6 354 0.8 36619 85.4 5.7 333 0.8 36952 86.2 5.8 321 0.7 37273 87.0 5.9 468 1.1 37741 88.1 6

313 0.7 38054 88.8 6.1 253 0.6 38307 89.4 6.2 261 0.6 38568 90.0 6.3 338 0.8 38906 90.8 6.4 240 0.6 39146 91.3 6.5 211 0.5 39357 91.8 6.6 194 0.5 39551 92.3 6.7 193 0.5 39744 92.7 6.8 263 0.6 40007 93.3 6.9 162 0.4 40169 93.7 7

140 0.3 40309 94.0 7.1 134 0.3 40443 94.4 7.2 192 0.4 40635 94.8 7.3 120 0.3 40755 95.1 7.4 101 0.2 40856 95.3 7.5 108 0.3 40964 95.6 7.6 142 0.3 41106 95.9 7.7 92 0.2 41198 96.1 7.8 82 0.2 41280 96.3 7.9 88 0.2 41368 96.5 8

140 0.3 41508 96.8 8.1 66 0.2 41574 97.0 8.2 59 0.1 41633 97.1 8.3 58 0.1 41691 97.3 8.4 98 0.2 41789 97.5 8.5 54 0.1 41843 97.6 8.6 52 0.1 41895 97.7 8.7 58 0.1 41953 97.9 8.8 59 0.1 42012 98.0 8.9 73 0.2 42085 98.2 9

41 0.1 42126 98.3 9.1 42 0.1 42168 98.4 9.2 34 0.1 42202 98.5 9.3 60 0.1 42262 98.6 9.4 34 0.1 42296 98.7 9.5 19 0.0 42315 98.7 9.6 32 0.1 42347 98.8 9.7 34 0.1 42381 98.9 9.8 28 0.1 42409 98.9 9.9 25 0.1 42434 99.0 10 31 0.1 42465 99.1 10.1 33 0.1 42498 99.2 10.2 17 0.0 42515 99.2 10.3 24 0.1 42539 99.3 10.4 23 0.1 42562 99.3 10.5 26 0.1 42588 99.4 10.6 12 0.0 42600 99.4 10.7 18 0.0 42618 99.4 10.8 17 0.0 42635 99.5 Page 10 of 22

Table 3 (continued)

Results of SAS Wind Speed Statistics Code 1997-2001 NORTH ANNA HIGH WIND SPEED FREQUENCY DISTRIBUTION OF WIND SPEED AT 159 FEET CUMULATIVE CUMULATIVE WINDSHI FREQUENCY PERCENT FREQUENCY PERCENT 10.9 19 0.0 42654 99.5 11 24 0.1 42678 99.6 11.1 15 0.0 42693 99.6 11.2 15 0.0 42708 99.6 11.3 8

0.0 42716 99.7 11.4 13 0.0 42729 99.7 11.5 9

0.0 42738 99.7 11.6 13 0.0 42751 99.7 11.7 10 0.0 42761 99.8 11.8 8

0.0 42769 99.8 11.9 5

0.0 42774 99.8 12 2

0.0 42776 99.8 12.1 1

0.0 42777 99.8 12.2 8

0.0 42785 99.8 12.3 2

0.0 42787 99.8 12.4 3

0.0 42790 99.8 12.5 7

0.0 42797 99.9 12.6 3

0.0 42800 99.9 12.7 2

0.0 42802 99.9 12.8 5

0.0 42807 99.9 12.9 3

0.0 42810 99.9 13 1

0.0 42811 99.9 13.1 3

0.0 42814 99.9 13.3 1

0.0 42815 99.9 13.4 3

0.0 42818 99.9 13.5 3

0.0 42821 99.9 13.6 5

0.0 42826 99.9 13.7 3

0.0 42829 99.9 13.8 2

0.0 42831 99.9 13.9 2

0.0 42833 99.9 14 3

0.0 42836 99.9 14.1 3

0.0 42839 100.0 14.2 3

0.0 42842 100.0 14.3 3

0.0 42845 100.0 14.4 1

0.0 42846 100.0 14.6 5

0.0 42851 100.0 14.8 1

0.0 42852 100.0 15 3

0.0 42855 100.0 15.2 2

0.0 42857 100.0 15.3 1

0.0 42858 100.0 15.8 1

0.0 42859 100.0 17.4 1

0.0 42860 100.0 Page 11 of 22

2) ASSUMPTIONS The louvers on the east and west faces of the auxiliary building normally flow 16,000 cfm into the 291'10" level of the auxiliary building from outside air. The only accident for which effluents would be expected to potentially egress out of these louvers is the fuel handling accident. In the fuel handling accident, portions of the gap inventory are postulated to escape the reactor pool and migrate from the containment into the auxiliary building 291'10" level via the personnel access hatch. It would be expected that the louvers closest to the containment (the source of the effluent) would flow an effluent concentration higher than the louvers furthest from the containment. Thus, both louvers on the western face of the auxiliary building were modeled as one louver located halfway between and the two louvers on the eastern face of the auxiliary building were modeled as one louver located halfway between.

When the control room is isolated the locations for air inlet to the control room concrete envelope are the emergency control room fan intakes. The emergency control room intakes designated C11 and C4 in this calculation are at the inlet or supply ducts for the Unit 2 and Unit 1 air conditioning chiller rooms respectively.

As can be seen in Sketches No. 3 and 4, the actual emergency fans for C11 and C4 are inside another compartment within the control room envelope and the supply ducts for these fans take suction on the air conditioning chiller rooms. It was assumed that the majority of the air entering into the chiller rooms is provided through the chiller room supply ducts which take suction from the Turbine building / Service building air volume.

When determining the source to receptor distances, the turbine building and service building walls and floors were ignored. By ignoring the turbine/service building walls and floors the distances from the sources to the emergency control room fan receptors would include short runs inside the turbine/service building. The portion of the total source-to-receptor distances that are inside a building are very small compared to the overall source-to-receptor distances. The alternative to ignoring the turbine/service building walls and floors in measuring the source-to-receptor distances is to measure the source-to-receptor distances to the turbine building supply louvers on the southern face of the turbine building. The equilibrium concentration of an effluent inside the turbine building would be approximated with an average atmospheric dispersion factor based on all the openings into the turbine building weighted by their cross sectional area. Therefore, the assumption was made that the small decrease in the atmospheric dispersion factors caused by including short inside distances would be less than the decreases in the atmospheric dispersion factors which would be applied if a cross sectional area weighted average atmospheric dispersion factor were used.

3) MODELING OPTIONS 3.1) RELEASES AND RECEPTORS The three types of releases that can be specified in ARCON96 are ground, vent and elevated or stack releases. However, Regulatory Guide 1.194 [Reference 3] requires Page 12 of 22

that no vent releases should be modeled with ARCON96. Therefore, only ground and elevated releases can be modeled with ARCON96. In the case of the North Anna site, none of the sources is at an elevation two and half times the height of the buildings on site. Therefore, there are no sources that qualify for the elevated release option of ARCON96. This means that all the source-receptor pairs were modeled as ground level releases in the ARCON96 runs.

The auxiliary building louvers being modeled as sources were treated as point sources.

The only accident in which these louvers could be sources is the fuel handling accident where the portion of the gap inventory which escapes the core pool migrates into the auxiliary building 291'10" level via the personnel access hatch.

The equipment hatches were treated as point sources. The location of the point source was modeled as the center of each equipment hatch.

The containment buildings were modeled as diffuse sources. The distance between the containment buildings and the receptors was determined in accordance with Regulatory Guide 1.194. That is, the minimum distance from the receptor to the containment outer wall was used. This was determined for each receptor individually. The results are presented in Table 1. The use of the diffuse source option of ARCON96 also requires the calculation of sigma-y and sigma-z.

Sigma-z and sigma-y were computed in accordance with Regulatory Guide 1.194 by dividing the width and height of the containment building by 6.

In this case the containment is a right circular cylinder topped by a hemispherical dome.

So the area of the hemisphere (626.08 square meters) was added to the area of the right circular cylinder (890.48 square meters) and the resulting total area was assumed to be a right circular cylinder with the same radius as the lower part of the containment (20.57 meters). This results in a height above grade of 36.86 meters and a width of 41.15 meters.

So the sigma-y value is the containment width divided by 6 (6.86) and the sigma-z value is the height of the re-configured containment building divided by 6 (6.14).

For all the ARCON96 runs the cross sectional area of one of the containment buildings above grade was used to model a wake effect. As was discussed in Section 1.2, the area of the containment building entered was 1516.6 square meters.

The remaining sources were all modeled as point sources. These remaining sources were the RWST vents, the PORV exhaust stacks, the vent stacks and the primary ventilation blowout panels.

3.2) PORV STEAM FLOW According to Regulatory Guide 1.194, atmospheric dispersion factors computed by ARCON96 for atmospheric relief valves can be reduced by a factor of 5 if two conditions are met.

First, the flow from the valve must be vertical and must not be impeded.

Second, the vertical velocity of the flow must be at least 5 times the 95th percentile wind speed at the elevation of the release. In the case of the PORVs for North Anna the Page 13 of 22

steam flow from these valves is vertical and unimpeded. See Figure 1 for a simplified arrangement of the steam flow path through a PORV. The vertical velocity of the steam exhausting these valves is conservatively estimated in the discussion below for the steam generator tube rupture (SGTR) accident.

The highest density of steam is at saturated conditions (versus superheated steam).

The steam exiting the PORV exhaust stack was assumed to be saturated steam since this would yield a lower vertical velocity than treating the steam as superheated. The vertical velocity of the steam exiting the PORV exhaust stack is limited to being no higher than the choked flow velocity. The following background information on choked flow is from the ASME Steam Tables for Industrial Use [Reference no. 2]:

"An important industrial problem is the flow of fluid through nozzles, with reduction of pressure across the nozzle. Often, these flows can be considered to be isentropic. For a given upstream pressure, decreasing the downstream pressure increases the flow rate until a certain point; after that point (sometimes known as the "critical pressure," not to be confused with the critical pressure associated with the end of the vapor-liquid saturation curve), further decreases in downstream pressure do not produce more flow. At this state, the flow is said to be "choked"; the velocity of the flow at that point is called the choking velocity.

The determination of choked flow involves finding a condition where the velocity divided by the specific volume (a ratio proportional to the mass flow rate) is maximized. The velocity used in this maximization is determined by assuming that the change in enthalpy in isentropic expansion from stagnant upstream conditions to the choked state is converted to kinetic energy of the fluid.

For expansions taking place without any phase change, the choking velocity is simply equal to the speed of sound at the choked conditions."

According to the ASME Steam Tables for Industrial Use [Reference no. 2], the choked flow velocity of saturated steam at atmospheric pressure is 1547 feet per second. The lowest mass flow out of the affected steam generator PORV - 84.9 pounds mass per second - occurs at 30 minutes after the accident just before operator action isolates the steam generator. The pressure of the steam as it leaves the PORV exhaust stack is unknown. Saturated steam at atmospheric pressure has a density of 0.037 pounds per cubic foot. The exhaust stack for the PORV is a 10" diameter vertical pipe. The cross sectional area of a 10" diameter pipe is 0.545 square feet. If the steam at the end of the PORV exhaust stack reached equilibrium with atmospheric pressure (14.7 pounds per square inch) it would have a density of 0.037 pounds per cubic foot. At a density of 0.037 pounds per cubic foot, the steam would have to have a vertical velocity of about 4200 feet per second to flow 84.9 pounds per second through an area of 0.545 square feet.

This far exceeds the choked flow velocity of saturated steam at atmospheric pressure - 1547 feet per second. Therefore, the steam at the end of the PORV exhaust stack must be at a pressure higher than atmospheric pressure so that it has a density high enough to meet the mass flow rate requirement.

However, the pressure of the steam at the end of the PORV exhaust stack cannot be at an arbitrarily high value.

Page 14 of 22

FIGURE 1 - A SIMPLIFIED DIAGRAM OF PORV STEAM FLOW STEAM FLOW PORV EXHAUST STACK PORV MAIN STEAM Page 15 of 22

The steam leaving the PORV exhaust stack will tend to come into equilibrium with atmospheric pressure as quickly as possible. This means that the steam pressure at the end of the PORV exhaust stack will be at the lowest possible pressure for which the steam velocity does not exceed the choked flow velocity. The steam at the end of PORV exhaust stack must be at choked flow conditions and at a pressure higher than atmospheric pressure.

By using the ASME Steam Tables for Industrial Use [Reference no. 2] in an iterative fashion, it was determined that saturated steam at a pressure of approximately 41 pounds per square inch flows 84.9 pounds of steam per second through a cross sectional area of 0.545 square feet at it's choked flow velocity of about 1590 feet per second.

This is the lowest saturated steam pressure that would flow 84.9 pounds of steam per second at choked flow velocity through a cross sectional area of 0.545 square feet.

During an SGTR, the unaffected steam generators flow for 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> and are not isolated at 30 minutes like the affected steam generator. Furthermore, the unaffected PORVs are not modeled as being stuck open and would open only when their setpoint pressure is reached. The setpoint pressure is adjustable and would be reduced by the operators to maximize the steam flow and hence the cool down rate during the post-accident recovery effort. The calculation of the mass flow rates out of the unaffected steam generators is broken into two time intervals. For the first 30 minutes the mass flow is calculated at specific times up to 30 minutes. For the first 30 minutes the lowest mass flow out of one of the unaffected steam generators is 34.6 pounds per second. Using the ASME Steam Tables for Industrial Use [Reference no. 2] iteratively, it was found that the lowest pressure which would allow a mass flow rate of 34.6 pounds of saturated steam per second through a cross sectional area of 0.545 square feet at choked flow velocity is approximately 16.1 pounds per square inch. At this pressure the choked flow velocity of the saturated steam is about 1550 feet per second.

The second time interval for the calculation of the mass flow of the unaffected steam generators is from 30 minutes to 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />. For this second time interval an integrated mass flow over the 7.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> was calculated. There are no mass flow rates at specific times. The average mass flow rate was computed by dividing the integrated mass flow over 7.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> by the number of seconds in 7.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br />. The lowest integrated mass flow between the loss-of-offsite power and no loss-of-offsite power scenarios over the 7.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> is 892,000 pounds mass. This flow occurred over 27,000 seconds to yield an average mass flow rate of 16.52 pounds mass per second per steam generator. Again, this mass flow rate does not reflect the actual mass flow rates since the unaffected PORVs are only going to flow when their pressure setpoint is reached. This means that they will open and shut frequently over the 7.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> and that the actual mass flow rate when they are open will be much higher than the time average mass flow rate. Based on the ASME Steam Tables for Industrial Use, a mass flow rate of 16.52 pounds of saturated steam per second through a cross sectional area of 0.545 square feet is not at choked flow conditions at atmospheric pressure. The density of saturated steam at Page 16 of 22

atmospheric pressure is 0.037 pounds per cubic foot.

At this density, the vertical velocity required to pass 16.52 pounds per second through a 0.545 square foot area is 812 feet per second. This is approximately 248 meters per second.

For the SGTR accident the minimum vertical velocity of the steam exiting a PORV exhaust stack is about 812 feet per second or about 248 meters per second. The 95th percentile wind speed at the elevation of the top of the PORVs exhaust stack is 5.72 meters per second. Five time's 5.72 meters per second is 28.6 meters per second.

Thus, the minimum vertical velocity of the steam at the point where it exits the PORVs exhaust stack is far in excess of the threshold needed to qualify for the factor of 5 reduction in ARCON96 calculated atmospheric dispersion factors.

For the lock rotor accident (LRA) the core / decay heat driving the steam flows out of the steam generators is identical to the core / decay heat driving the releases for the SGTR.

The primary difference between the SGTR and LRA is that after 30 minutes only two steam generators are exhausting steam in the SGTR and in the LRA all three steam generators flow steam to the environment for 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />. This means that the steam flow rates in the LRA will be about 2/3 of the steam flow rates in the SGTR. However, the minimum PORV exhaust velocity for the SGTR is nearly 10 times the 28.6 meters per second threshold needed to qualify for the reduction in the atmospheric dispersion factors. Thus, the PORV steam flows for the LRA will have vertical velocities high enough to allow the use of the reduced PORV atmospheric dispersion factors in the LRA dose analysis.

For the main steam line break (MSLB), the information available about the steam flow out of the PORVs was not sufficient to determine the vertical velocity of the steam.

Therefore, the reduction factor of 5 was not applied to the PORV atmospheric dispersion factors used to model the MSLB.

4) RESULTS The results of the ARCON96 runs are shown in Table 4. The Units of the atmospheric dispersion factors in Table 4 and also in Table 5 are (Curies / cubic meter)/ (Curies /

second) or (seconds / cubic meter) after simplification. The results of the PORV runs in Table 4 do not include the reduction factor of 5 for vertical exhaust velocity. The values of the atmospheric dispersion factors for the Vent Stack B to C-6 control room intake are not shown in Table 4. This is because the C-6 control room intake is less than 10 meters from the base of Vent Stack B. According to Nuclear Regulatory Commission guidance on the use of ARCON96, these atmospheric dispersion factor values cannot be used because the distance from the source to the receptor is less than 10 meters.

Because of this restriction, C-6 will be procedurally precluded from functioning as an emergency control room intake. This will be accomplished with emergency procedures that will stipulate that the fan associated with the C-6 intake can only be operated in re-circulation mode. In re-circulation mode the C-6 fan takes suction on the air inside the control room envelope and does not draw on the outside air.

Page 17 of 22

Table 4-Results of ARCON96 Runs LOCATION XIQ to C,-4 X/Q To C-1I XIQ to C-10 XIQ to C-6 XIQ to norm intake Point Snirces Unit 1 PORV A 0-2 hours 2.94E-03 1.05E-03 1.53E-03 3.35E-03 7.51 E-03 2-8 hours 2.18E-03 6.62E-04 9.78E-04 2.06E-03 6.41 E-03 8-24 hours 8.34E-04 2.33E-04 3.41 E-04 7.51 E-04 2.51 E-03 24-96 hours 5.88E-04 1.91 E-04 2.73E-04 5.62E-04 1.76E-03 96-720 hours 4.36E-04 1.57E-04 2.21 E-04 3.96E-04 1.31 E-03 Unit 1 PORV C 0-2 hours 3.11 E-03 9.64E-04 1.39E-03 3.15E-03 8.93E-03 2-8 hours 2.14E-03 6.19E-04 8.98E-04 2.02E-03 7.29E-03 8-24 hours 8.26E-04 2.18E-04 3.1 OE-04 7.12E-04 2.93E-03 24-96 hours 5.66E-04 1.74E-04 2.55E-04 5.49E-04 2.01 E-03 96-720 hours 4.29E-04 1.47E-04 2.06E-04 3.87E-04 1.51 E-03 Unit 1 PORV B 0-2 hours 3.14E-03 8.93E-04 1.27E-03 2.95E-03 1.04E-02 2-8 hours 2.08E-03 5.66E-04 8.16E-04 1.93E-03 8.20E-03 8-24 hours 7.87E-04 2.03E-04 2.85E-04 6.44E-04 3.23E-03 24-96 hours 5.59E-04 1.60E-04 2.31 E-04 5.19E-04 2.25E-03 96-720 hours 4.36E-04 1.36E-04 1.90E-04 3.67E-04 1.68E-03 Unit 2 PORV C 0-2 hours 5.49E-04 2.42E-03 1.86E-03 8.30E-04 5.66E-04 2-8 hours 4.68E-04 1.94E-03 1.57E-03 7.35E-04 4.71 E-04 8-24 hours 1.84E-04 7.73E-04 6.24E-04 2.87E-04 1.84E-04 24-96 hours 1.35E-04 5.36E-04 4.37E-04 2.08E-04 1.37E-04 96-720 hours 1.02E-04 4.04E-04 3.26E-04 1.56E-04 1.06E-04 Unit 2 PORV B 0-2 hours 5.75E-04 2.59E-03 2.06E-03 9.08E-04 6.1 OE-04 2-8 hours 5.02E-04 2.05E-03 1.72E-03 7.95E-04 5.08E-04 8-2,4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> 1.95E-04 8.12E-04 6.85E-04 3.09E-04 1.96E-04 24-96 hours 1.44E-04 5.64E-04 4.77E-04 2.26E-04 1.48E-04 96-720 hours 1.08E-04 4.22E-04 3.56E-04 1.68E-04 1.13E-04 Unit 2 PORV A 0-2 hours 6.23E-04 2.71 E-03 2.23E-03 9.88E-04 6.37E-04 2-8 hours 5.27E-04 2.12E-03 1.87E-03 8.48E-04 5.47E-04 8-24 hours 2.09E-04 8.28E-04 7.45E-04 3.35E-04 2.08E-04 24-96 hours 1.53E-04 5.88E-04 5.14E-04 2.41 E-04 1.58E-04 96-720 hours 1.15E-04 4.33E-04 3.85E-04 1.81 E-04 1.19E-04 U1 RWST vent 0-2 hours 2.18E-03 5.50E-04 7.19E-04 1.51 E-03 6.36E-03 2-8 hours 1.42E-03 3.46E-04 4.52E-04 9.67E-04 4.16E-03 8-24 hours 4.89E-04 1.29E-04 1.66E-04 3.42E-04 1.39E-03 24-96 hours 3.84E-04 9.82E-05 1.28E-04 2.67E-04 1.09E-03 96-720 hours 2.72E-04 8.43E-05 1.09E-04 2.08E-04 8.13E-04 U2 RWST vent 0-2 hours 3.63E-04 1.28E-03 9.85E-04 5.23E-04 3.73E-04 2-8 hours 3.22E-04 1.06E-03 8.39E-04 4.56E-04 3.21 E-04 8-24 hours 1.26E-04 4.26E-04 3.34E-04 1.78E-04 1.23E-04 24-96 hours 9.24E-05 3.01 E-04 2.37E-04 1.32E-04 9.31 E-05 96-720 hours 6.96E-05 2.25E-04 1.77E-04 9.84E-05 7.14E-05 Vent Stack A 0-2 hours 2.64E-03 2.06E-03 3.75E-03 5.69E-03 2.24E-03 2-8 hours 2.20E-03 1.46E-03 2.60E-03 4.60E-03 1.60E-03 8-24 hours 8.21 E-04 5.77E-04 1.03E-03 1.74E-03 6.02E-04 24-96 hours 6.46E-04 3.92E-04 7.03E-04 1.35E-03 4.45E-04 96-720 hours 4.73E-04 3.11 E-04 5.52E-04 9.96E-04 3.56E-04 Vent Stack B 0-2 hours 3.21 E-03 1.72E-03 2.91 E-03 2.67E-03 2-8 hours 2.65E-03 1.22E-03 2.13E-03 1.88E-03 8-24 hours 9.96E-04 4.80E-04 8.25E-04 7.17E-04 24-96 hours 7.77E-04 3.26E-04 5.66E-04 5.11 E-04 96-720 hours 5.70E-04 2.59E-04 4.47E-04 4,05E-04 Page 18 of 22

Table 4-Results of ARCON96 Runs (continued)

LOCATI ON X/O To 0-4 X/Q to C-11 X/Q to C-10 X/Q to C-6 X/Q to norm intake Point Sources U1 blowout panel 0-2 hours 1.06E-03 1.40E-03 1.70E-03 1.59E-03 1.47E-03 2-8 hours 8.78E-04 8.99E-04 1.05E-03 1.18E-03 1.24E-03 8-24 hours 3.54E-04 3.13E-04 3.94E-04 4.69E-04 4.95E-04 24-96 hours 2.44E-04 2.46E-04 2.89E-04 3.30E-04 3.53E-04 96-720 hours 1.83E-04 1.73E-04 2.06E-04 2.45E-04 2.63E-04 U2 blowout panel 0-2 hours 8.90E-04 1.90E-03 2.12E-03 1.44E-03 1.08E-03 2-8 hours 7.59E-04 1.15E-03 1.38E-03 1.18E-03 9.37E-04 8-24 hours 3.03E-04 4.36E-04 5.29E-04 4.76E-04 3.67E-04 24-96 hours 2.12E-04 3.19E-04 3.76E-04 3.26E-04 2.67E-04 96-720 hours 1.58E-04 2.28E-04 2.93E-04 2.44E-04 2.01 E-04 E Aux Bid louver 0-2 hours 1.96E-03 1.92E-03 2.86E-03 3.54E-03 2.78E-03 2-8 hours 1.58E-03 1.23E-03 1.82E-03 2.53E-03 2.30E-03 8-24 hours 6.44E-04 4.37E-04 6.37E-04 1.01 E-03 9.16E-04 24-96 hours 4.39E-04 3.40E-04 5.07E-04 6.95E-04 6.59E-04 96-720 hours 3.29E-04 2.62E-04 3.55E-04 5.17E-04 4.97E-04 W Aux Bld louver 0-2 hours 9.59E-04 3.38E-03 3.66E-03 1.73E-03 1.05E-03 2-8 hours 8.05E-04 2.05E-03 2.46E-03 1.42E-03 8.74E-04 8-24 hours 3.29E-04 7.96E-04 9.87E-04 5.78E-04 3.50E-04 24-96 hours 2.29E-04 5.77E-04 6.80E-04 3.98E-04 2.52E-04 96-720 hours 1.72E-04 4.12E-04 5.02E-04 2.99E-04 1.90E-04 U1 Equipment Hatch 0-2 hours 8.15E-04 5.34E-04 6.37E-04 8.35E-04 1.43E-03 2-8 hours 5.34E-04 3.47E-04 4.08E-04 5.06E-04 9.54E-04 8-24 hours 2.10E-04 1.22E-04 1.43E-04 1.96E-04 3.83E-04 24-96 hours 1.47E-04 9.43E-05 1.14E-04 1.42E-04 2.63E-04 96-720 hours 1.14E-04 6.90E-05 8.03E-05 1.01 E-04 1.95E-04 U2 Equipment Hatch 0-2 hours 3.50E-04 8.47E-04 7.38E-04 4.77E-04 3.84E-04 P2-8 hours 2.98E-04 6.41 E-04 5.92E-04 3.98E-04 3.28E-04 8-24 hours 1.22E-04 2.66E-04 2.45E-04 1.62E-04 1.33E-04 24-96 hours 8.61 E-05 1.84E-04 1.67E-04 1.14E-04 9.54E-05 96-720 hours 6.48E-05 1.36E-04 1.25E-04 8.53E-05 7.20E-05 Diffuse Sources Ul Containment 0-2 hours 1.23E-03 6.26E-04 8.01 E-04 1.25E-03 2.61 E-03 2-8 hours 8.87E-04 4.23E-04 5.20E-04 7.68E-04 1.83E-03 8-24 hours 3.49E-04 1.52E-04 1.83E-04 2.87E-04 7.72E-04 24-96 hours 2.46E-04 1.17E-04 1.44E-04 2.14E-04 5.69E-04 96-720 hours 1.87E-04 8.79E-05 1.05E-04 1.57E-04 4.35E-04 U2 Containment 0-2 hours 4.38E-04 1.15E-03 1.02E-03 6.16E-04 4.79E-04 2-8 hours 3.82E-04 9.02E-04 8.34E-04 5.40E-04 4.14E-04 8-24 hours 1.69E-04 3.57E-04 3.51 E-04 2.41 E-04 1.83E-04 24-96 hours 1.16E-04 2.55E-04 2.49E-04 1.64E-04 1.27E-04 96-720 hours 8.81 E-05 1.91 E-04 1.90E-04 1.25E-04 9.72E-05 Page 19 of 22

For each accident analysis the largest applicable atmospheric dispersion factors were selected to calculate the limiting dose consequences. For most of the sources, there was one source-receptor geometry that produced the largest values for each of the five time intervals. For the MSLB, LRA and SGTR accident analyses the largest PORV to normal control room intake set of atmospheric dispersion factors was used to calculate the limiting doses. For the SGTR and LRA accidents the atmospheric dispersion factors were divided by 5 because of the high vertical steam exhaust velocity. For the LOCA containment leakage dose contribution calculation, a composite set of atmospheric dispersion factors was used.

This composite set of atmospheric dispersion factors consisted of the largest atmospheric dispersion factor for each of the five time intervals chosen from all the possible source-receptor combinations with either the Unit 1 or Unit 2 containment as the source and either the C-4, C-11 or C-10 emergency control room intake as the receptor. The C-6 emergency control room intake was excluded as a receptor for the LOCA since the control room will be isolated and the fan associated with the C-6 intake would be aligned in re-circulation mode by procedure. Similarly, for the LOCA ECCS leakage dose calculation, a composite set of atmospheric dispersion factors was used which consisted of the largest atmospheric dispersion factor for each of the five time intervals chosen from all possible source-receptor combinations with either vent stack A or B as the source and either the C-4, C-11 or C-10 emergency control room intakes as the receptor.

The atmospheric dispersion factors used to calculate the limiting dose consequences are shown in Table 5 below.

Page 20 of 22

TABLE 5 - CONTROL ROOM ATMOSPHERIC DISPERSION FACTORS USED TO CALCULATE THE LIMITING DOSES ATMOSPHERIC Source of ACCIDENT SOURCE RECEPTOR DISPERSION FACTOR XIQ Values ACCIDE SOURCE POINT (sec/M 3)

Selected Vent Stack Emergency 3.75E-3 0-2 hr Vent A to C-1 0 Control Room 2.65E-3 2-8 hr Vent B to C-4 Intake 1.03E-3 8-24 hr Vent A to C-1 0 7.77E-4 24-96 hr Vent B to C-4 5.70E-4 96-720 hr Vent B to C-4 RWST Vent Emergency 2.18E-3 0-2 hr U1 RWST to C-4 Control Room 1.42E-3 2-8 hr U1 RWST to C-4 LOCA Intake 4.89E-4 8-24 hr U1 RWST to C-4 3.84E-4 24-96 hr U1 RWST to C-4 2.72E-4 96-720 hr U1 RWST to C-4 Containment Emergency 1.23E-3 0-2 hr U1 Cont to C-4 Control Room 9.02E-4 2-8 hr U2 Cont to C-1 1 Intake 3.57E-4 8-24 hr U2 Cont to C-11 2.55E-4 24-96 hr U2 Cont to C-1 1.91 E-4 96-720 hr U2 Cont to C-1 E Aux Normal 2.78E-3 0-2 hr E AuxLvr to NCR Building Control Room 2.30E-3 2-8 hr E AuxLvr to NCR FHA Louver Intake 9.16E-4 8-24 hr E AuxLvr to NCR (Personnel 6.59E-4 24-96 hr E AuxLvr to NCR Access Hatch) 4.97E-4 96-720 hr E AuxLvr to NCR PORV Normal 2.08E-3 0-2 hr U1 PorvB to NCR SGTR Control Room 1.64E-3 2-8 hr U1 PorvB to NCR (divided by I ntake 6.46E-4 8-24 hr U1 PorvB to NCR

5) 4.50E-4 24-96 hr U1 PorvB to NCR

5) 3.36E-4 96-720 hr U1 PorvB to NCR PORV Normal 1.04E-2 0-2 hr U1 PorvB to NCR Control Room 8.20E-3 2-8 hr U1 PorvB to NCR MSLB Intake 3.23E-3 8-24 hr U1 PorvB to NCR 2.25E-3 24-96 hr U1 PorvB to NCR 1.68E-3 96-720 hr U1 PorvB to NCR PORV Normal 2.08E-3 0-2 hr U1 PorvB to NCR LRA Control Room 1.64E-3 2-8 hr U1 PorvB to NCR (divided by Intake 6.46E-4 8-24 hr U1 PorvB to NCR

5) 4.50E-4 24-96 hr U1 PorvB to NCR 3.36E-4 96-720 hr U1 PorvB to NCR Page 21 of 22

REFERENCES

1. Computer Code ARCON96, "Atmospheric Relative Concentrations in Building Wakes", NUREG/CR-6331, PNNL-10521, Rev.1, May 1997.

2.

"ASME Steam Tables for Industrial Use", The American Society of Mechanical Engineers Press, 2000, based on the IAPWS Industrial Formulation 1997 for the Thermodynamic Properties of Water and Steam, CRTD-Vol.58.

3.

REGULATORY GUIDE 1.194, "Atmospheric Relative Concentrations for Control Room Radiological Habitability Assessments at Nuclear Power Plants", U.S.

Nuclear Regulatory Commission, Office of Nuclear Regulatory Research, June 2003.

4.

Letter from W.R. Matthews to the NRC, Serial No. 00-123B, "Virginia Electric and Power Company Surry Power Station Units 1 and 2 Request for Additional Information Alternate Source Term -

Proposed Technical Specification Change",

November 20, 2000.

5.

North Anna UFSAR Section 2.3.3.2 "Upgraded Onsite Meteorological Measurements Program for Station Operation", Sub-section 2.3.3.2.1 "General Program Description".

6.

System Design Basis Document for Auxiliary Building Ventilation System North Anna Power Station, SDBD-NAPS-HA, Rev. 1, October 31, 2002.

Page 22 of 22

Serial No. 03-464A 50-338/339 Virginia Electric and Power Company North Anna Power Station Units 1 and 2 Proposed Technical Specification Changes Implementation of Alternate Source Term Request for Additional Information Sketches North Anna Power Station Units 1 and 2 Virginia Electric and Power Company (Dominion)

Sketch No. 1 Column Line C Legend Receptor Source Ul U2 V

Ri R2 El E2 P1 P2 BI B2 EL WL Unit 1 containment (diffuse)

Unit 2 containment (diffuse) vent stacks A and B (only 22' apart)

Unit 1 RWST Unit 2 RWST Unit 1 equipment hatch Unit 2 equipment hatch Unit 1 PORVs Unit 2 PORVs Unit 1 primary ventilation blowout panel Unit 2 primary ventilation blowout panel auxiliary building east louver auxiliary building west louver NCR CIO Cli C6 C4 normal control room (CR) intake emergency CR intake by column lines C and 10 emergency CR intake by column lines C and 11 emergency CR intake by column lines C and 6 emergency CR intake by column lines C and 4

Sketch No. 2 Turbine Building / Service Building Air Volume Colun LineC Unit 2 F-41 Intake Ducting Unit 1 F-41 Intake Ducting N

Control Room 7

A Column Line 10 Unit 2 F-41 Filter Housing A

Unit 1 F-41 Filter Housing Column Line 6

Sketch No. 3 Unit 1 Air Cond Chiller Room Exhaust Fan Outlet Unit I Air Cond Chiller Room Intake Louver Turbine Building / Service Building Air Volume Column Line C Chiller Room Unit 1 Instrument Room Unit 1 Switchgear and Relay Room Unit 1 F42 filter /

housing and intake ducting Column Line 4

Sketch No. 4 Unit 2 Air Cond Chiller Room Exhaust an Outlet Unit 2 Air Cond Chiller Room I

ke Louver Turbine Building / Service Building Air Volume Column Line C U

Li Unit 2 Air Cond Chiller Room Unit 2 Instrument Room Unit 2 Switchgear and Relay Room Unit 2 Air Cond Room Unit 2F42 filter housing and intake ducting A

Column Line 11