Text

Proposed Emergency Plan Revision - Location of the Technical Support Center (TSC) Supplemental Information - LOCA Dose Calculation Summary Report and Elimination of CO2 Fire Suppression System
	ML23192A215
Person / Time
Site:	North Anna
Issue date:	06/27/2023
From:	James Holloway; Virginia Electric & Power Co (VEPCO)
To:	; Document Control Desk, Office of Nuclear Reactor Regulation
References
	23-045
	Download: ML23192A215 (1)
	v • d • e

VIRGINIA ELEcTRIC AND POWER COMPANY RICHMOND, VIRGINIA 23261 June 27, 2023 10 CFR 50.54(q) 10 CFR 50.90 U. S. Nuclear Regulatory Commission Serial No.: 23-045 Attention: Document Control De-Sk NRA/GDM: RO Washington, DC 20555-0001 Docket Nos.: 50-338/339 License Nos.: NPF-4/7 VIRGINIA ELECTRIC AND POWER COMPANY NORTH ANNA POWER STATION UNITS 1 AND 2 PROPOSED EMERGENCY PLAN REVISION - RELOCATION OF THE TECHNICAL SUPPORT CENTER (TSC)

SUPPLEMENTAL INFORMATION - LOCA DOSE CALCULATION

SUMMARY

REPORT AND ELIMINATION OF CO2 FIRE SUPPRESSION SYSTEM By letter dated January 13, 2023, (ADAMS Accession No. ML23013A195), Virginia Electric and Power Company (Dominion Energy Virginia) submitted a license amendment

. request (LAR) to revise the North Anna Power Station (NAPS) Units 1 and 2 Emergency Plan. The proposed change would relocate the Technical Support Center (TSC) from its current location adjacent to the Main Control Room (MCR) to the building located outside the Protected Area (PA) previously used as the site Local Emergency Operations Facility (LEOF).

LOCA Dose Calculation Summary Report In support of the LAR, a dose calculation was completed to confirm the projected dose to personnel in the proposed TSC from a design basis Loss of Coolant Accident (LOCA) with a release to the environment would be less than the dose limit of five (5) rem Total Effective Dose Equivalent (TEDE). Subsequent to the LAR submittal, the NRC requested supplemental information summarizing the inputs to the LOCA dose calculation to facilitate its review. In response to the NRC request, a NAPS TSC LOCA Dose Summary Report has been prepared and is provided in Attachment 1 for the NRC's information and review. The dose analysis and X/Q input and output files supporting the LOCA dose calculation are included in the enclosed CD-ROM, and Attachment 2 provides a list and descriptions of the various files included on the CD-ROM. Attachment 3 includes a figure showing the site arrangement including the relocated TSC location. This figure provides the site geometry related to calculation of the X/Q dispersion factor for the relocated TSC.

Elimination of CO2 Fire Suppression System It was also stated in the LAR that a carbon dioxide (CO2) fire suppression system would be installed for the high efficiency gas absorption (HEGA) filter installed in the relocated XI_/ 5

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Serial No.: 23-045 Docket Nos.: 50-338/339 Page 2 of 3 TSC's ventilation system. Following the submittal of the LAR, it was determined the CO2 fire suppression system is not required due to the availability of other fire protection measures and equipment being installed. Consequently, the CO2 fire suppression system has been removed from the relocated TSC design modification. The technical basis for this decision is provided in Attachment 4. The marked-up LAR page indicating the proposed revision and the LAR replacement page incorporating the revision are provided in Attachments 5 and 6, respectively.

Should you have any questions or require additional information, please contact Mr. Gary D. Miller at (804) 273-2771.

Respectfully, Cr-James E. Holloway Vice President - Nuclear Engineering and Fleet Support Commitments contained in this letter: None.

Attachments:

1. Relocated Technical Support Center LOCA Dose Summary Report 1-A. Updated North Anna Core Inventory

2. Lists and Descriptions of Files Included on the Enclosed CD-ROM Supporting the Relocated TSC LOCA Dose Calculation

3. North Anna X/Q Geometry for the Relocated TSC

4. Technical Basis for Elimination of the Relocated TSC CO2 Fire Protection System

5. Marked-up LAR Page Indicating Deletion of the CO2 Fire Suppression System

6. Revised LAR Replacement Page Indicating Deletion of the CO2 Fire Suppression System

Enclosure:

CD-ROM - LOCA Dose Analysis and X/Q Input and Output Files COMMONWEALTH OF VIRGINIA )

)

COUNTY OF HENRICO )

The foregoing document was acknowledged before me, in and for the County and Commonwealth aforesaid, today by James E. Holloway, who is Vice President - Nuclear Engineering and Fleet Support, of Virginia Electric and Power Company. He has affirmed before me that he 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 his knowledge and belief.

Acknowledged before me this 27~ day of ~he. , 2023.

My Commission Expires: Ouj\.,,l.b .\-- ~ l, "Z.o:2.,3

GARY DON MILLER Notary Public Commonvvealth of Virginia As9. # 7629412 j My Comm1ss1on Expiras August 31, 2cg_

Serial No.: 23-045 Docket Nos.: 50-338/339 Page 3 of 3 cc: U. S. Nuclear Regulatory Commission - Region II (w/o Enclosure)

Attn: Regional Administrator Marquis One Tower 245 Peachtree Center Avenue, NE., Suite 1200 Atlanta, Georgia 30303-1257 Mr. G. Edward Miller NRC Senior Project Manager - North Anna Power Station U.S. Nuclear Regulatory Commission One White Flint North Mail Stop 09 E-3 11555 Rockville Pike Rockville, Maryland 20852-2738 Mr. L. John Klos (w/o Enclosure)

NRC Project Manager - Surry Power Station U.S. Nuclear Regulatory Commission One White Flint North Mail Stop 09 E-3 11555 Rockville Pike Rockville, M~ryland 20852-2738 NRC Senior Resident Inspector (w/o Enclosure)

North Anna Power Station State Health Commissioner (w/o Enclosure)

Virginia Department of Health James Madison Building - 7th floor 109 Governor Street, Suite 730 Richmond, Virginia 23219 Old Dominion Electric Cooperative (w/o Enclosure)

R-North-Anna-Correspondence@odec.com

Serial No.23-045 Docket Nos.: 50-338/339 Attachment 1 RELOCATED TECHNICAL SUPPORT CENTER LOCA DOSE

SUMMARY

REPORT PROPOSED EMERGENCY PLAN REVISION - RELOCATION OF THE TECHNICAL SUPPORT CENTER (JSC)

Virginia Electric and Power Company (Dominion Energy Virginia)

North Anna Power Station Units 1 and 2

Serial No.23-045 Docket Nos.: 50-338/339 Attachment 1 RELOCATED TECHNICAL SUPPORT CENTER LOCA DOSE

SUMMARY

REPORT NORTH ANNA POWER STATION UNITS 1 AND 2 TABLE OF CONTENTS Page No.

1.0 Introduction and Background ........................................................................................2 2.0 Purpose ..........................................................................................................................2 3.0 General Methodology ....................................................................................................2 4.0 TSC Dose Results .........................................................................................................3 5.0 Impact Assessment .......................................................................................................4 6.0 References ................................................................................................................... 14 -A: Updated North Anna Core Inventory LIST OF TABLES Page No.

Table 4-1: Summary ofTSC Dose Results ......................................................................4 Table 5-1: Summary of Changes for TSC Relocation X/Q Calculation ............................ 5 Table 5-2: Summary of Changes for TSC Relocation LOCA Dose .................................. 8 Page 1 of 14

Serial No.23-045 Docket Nos.: 50-338/339 Attachment 1 RELOCATED TECHNICAL SUPPORT CENTER LOCA DOSE

SUMMARY

REPORT NORTH ANNA POWER STATION UNITS 1 AND 2 1.0 Introduction and Background As part of the Subsequent License Renewal (SLR) efforts at North Anna Power Station (NAPS), the Technical Support Center (TSC) is being relocated to the former Local Emergency Operations Facility (LEOF} Building. NUREG-0737, Item 11.B.2 (Reference

[1]), requires that dose to TSC personnel during a Loss of Coolant Accident (LOCA) remain below the control room dose limit of 10 CFR 50, General Design Criterion (GDC) 19, which is 5 rem Total Effective Dose Equivalent (TEDE) for licensees that have adopted the Alternative Source Term (AST). Relocation of the TSC therefore requires a reanalysis of the consequences of a LOCA with respect to personnel in the new TSC location.

2.0 purpose This report summarizes the differences in inputs and assumptions used in analyzing the dose consequences to TSC personnel in the new location and the licensing basis AST implementation.

3.0 General Methodology The ARCON96 models docketed in Reference [4] were used as the basis for determining the atmospheric dispersion factors to the new TSC location. The previously analyzed release locations were reviewed for applicability and conservatism with respect to the new TSC location then updated to reflect the new TSC receptor location. The results of these updated ARCON96 models were extracted for use in the RADTRAD-NAI dose models.

The basis for the LOCA dose analysis is documented in Reference [8] and approved by the Nuclear Regulatory Commission (NRC) in Reference [9]. The analysis of record RADTRAD-NAI models developed for containment leakage, Emergency Core Cooling System (ECCS) leakage, and Refueling Water Storage Tank (RWST) backleakage were therefore used as the basis for the TSC LOCA dose analysis. Only the necessary modifications to add the TSC and an updated source term were made to the models.

These modifications included adding the TSC compartment, filtered intake pathway, and a TSC exhaust pathway.

The TSC RADTRAD-NAI models produced the inhalation and immersion doses for personnel within the TSC during the event. An additional dose location within the RADTRAD-NAI models determined the immersion dose from the radioactive cloud Page2 of 14

Serial No.23-045 Docket Nos.: 50-338/339 Attachment 1 surrounding the building to estimate shine from the cloud.

The relevant nuclide inventories with respect to the containment (sprayed and unsprayed), TSC filter, TSC compartment, and environmental integral were extracted from the RADTRAD-NAI leakage case outputs for use in the MicroShield, MicroSkyshine, and MCNP5 computer models. Two MicroShield/MicroSkyshine models determined the shine dose to TSC personnel from containment. A MCNPS model determined the shine dose to TSC personnel from the nuclide buildup on the TSC HVAC filters.

Each of the individual leakage case doses and shine component doses were summed to produce the overall TSC personnel dose for the thirty-day event.

4.0 TSC Dose Results The results of the TSC Relocation LOCA dose and the AST implementation for TSC dose are summarized in Table 4-1. As expected, the increase in TSC distance from the release points combined with changes in shielding and equipment configurations resulted in a considerably lower TSC dose.

The TSC Relocation analysis considered both an automatic Safety Injection (SI) signal-based isolation and a manual isolation at sixty minutes. The SI-based case aligned with the assumption of receipt of an SI signal at the TSC used in the AST implementation for TSC dose; however, the new TSC location will not be provided with an SI signal. The sixty minute manual isolation case ensured that TSC personnel can withstand additional time without air filtration in the event of manual TSC HVAC isolation during a LOCA. The results of both cases are presented in Table 4-1.

Although it is common for the containment skyshine component to be a smaller dose contributor than the containment direct shine, a number of conservatisms in the relocation analysis resulted in the skyshine being greater. These skyshine conservatisms included but are not limited to lack of credit for TSC wall or roof shielding due to preset code geometries, use of fewer time edits for the containment inventory resulting in conservatively high prediction of skyshine from 4 to 720 hours0.00833 days 0.2 hours 0.00119 weeks 2.7396e-4 months , and use of low steam density for the core inventory to minimize self-shielding. Inclusion of the TSC roof shielding would reasonably reduce the skyshine component by approximately 90%.

Page 3 of 14

Serial No.23-045 Docket Nos.: 50-338/339 Attachment 1 Table 4-1: Summary of TSC Dose Results TSC Dose Jrem TEDEl TSC Relocation LOCA Dose Component SI-based 60-min ASTTSC Isolation Isolation Containment Leaka~e 0.0262 0.4250 0.8000 ECCS Leakage 0.0114 0.0491 0.1200 RWST Leakaee 0.0007 0.0007 0.0057 Containment Direct Shine 0.0019 0.0019 0.047 Containment Skvshine 0.2660 0.2660 0.3810 Cloudshine1 0.0368 0.0368 0.6165 Filter Shine 0.0311 0.0311 0.1600

__2 Containment Shine throul!b. Main Steam Line Penetrations -- 0.0050 SI Piping under Main Steam Valve House & QS Pump -- -- 0.1940 House HydroJ;P;en Re-combiner Vault -- -- 0.0040 Total 0.38 0.82 2.33 1 Cloudsbine was reported individually for each of the three release cases. The individual values are summed here for comparison, to the cloudsbine/plume calculation.

2 Sources indicated with a result of"-" were deemed negligible with respect to the new TSC location due to source/receptor geometry.

5.0 Impact Assessment TSC relocation dose inputs were compiled from several references to produce a conservatively high TSC dose. Table 5-1 and Table 5-2 below summarize the inputs of the TSC relocation dose and compare them to the existing AST implementation. These tables may assist in determining the impact of changes to the licensing basis AST implementation.

The RADTRAD-NAI models used in the TSC relocation analysis were upconverted for use in RADTRAD-NAI Version 1.3 and benchmarked to the results of the analysis of record. This change represents a licensing basis change from Version 1.0 patch 3 to Version 1.3 for the LOCA dose *analysis. The process of converting and benchmarking the models required a time step sensitivity to ensure alignment with previous results, as well as proper calculation of the Exclusion Area Boundary (EAB) worst two-hour dose.

The RADTRAD-NAI models of the NAPS LOCA releases may be used as a starting point for subsequent analysis of other personnel locations with respect to the LOCA accident.

Additionally, the nuclide inventory and dose conversion files reflect a licensing basis change from SCALE 4.4a to SCALE 6.2.3 for determination of the core source term. The updated core source term incorporated a wider range of enrichments and a higher core average burnup within the constraints of the rated thermal power plus calorimetric Page 4 of 14

Serial No.23-045 Docket Nos.: 50-338/339 Attachment 1 uncertainty. Having been part of the up-conversion of RADTRAD-NAI models, these files may also be used as a starting point for subsequent RADTRAD-NAI Version 1.3 analyses.

Table 5-1: Summary of Changes for TSC Relocation X/Q Calculation Meteorological Data Period 1997-2001 1997-2001 In ut 1.1, 4 Lower Wind Instrument Height (m) 10.04 10.04 Table 1, 4 Upper Wind Instrument Height (m) 48.43 48.43 Table 1 4 Wind Speed Unit of Measure Meters/second (m/s) Meters/second (m/s) 4 Release Type Ground Ground Section 3.1 4 Building Area (m2) 1516.6 Effluent Vertical Velocity (m/s) 0.00 0.00 TableA-2, 5 TableA-2, 5 Vent/Stack Radius (m) 0.0 0.0 TableA-2, 5 TableA-2, 5 Vent/Stack Flow (m3/s) 0.0 0.0 TableA-2, 5 TableA-2, 5 Wind Direction Sector Width 90° 90° TableA-2, 5 TableA-2, 5 Terrain Elevation Difference (m) 0.0 0.0 TableA-2, 5 TableA-2, 5 Minimum Wind Speed (mis) 0.5 0.5 TableA-2, 5 TableA-2, 5 Surface Roughness (mis) 0.20 0.20 TableA-2, 5 TableA-2, 5 Sector Averaging Constant 4.3 4.3 TableA-2 5 TableA-2, 5 Hours in Averages 1, 2, 4, 8, 12, 24, 96, 168, 1, 2, 4, 8, 12, 24, 96, 360,720 168,360, 720 TableA-2, 5 TableA-2, 5 Minimum Number of Hours 1, 2, 4, 8, 11, 22, 87, 152, 1, 2, 4, 8, 11, 22, 87, 324,648 152,324,648 TableA-2, 5 TableA-2, 5 TSC Intake Hei ht m 6.8 3.96 Containment Source Table 1, [4]

Source Treatment Diffuse Diffuse Sigma-Y (m) 6.86 6.86 Si a-Z m 6.14 6.14 Page5of 14

Serial No.23-045 Docket Nos.: 50-3381339 Attachment 1 Sources Considered Ul Containment Ul/U2 Containment UlRWST AB Louvers Ul Equip. Hatch Ul/U2RWST Ul Blowout Panel Primary Ventilation VentStackA Blowout Panels Vent StackB VentStackA Vent StackB Section 3.1.3.1, 2 Source Release Heights (m) Table 1, [4}

Ul Containment 6.87 6.4 Vent Stack A 35.28 35.28 VentStackB 35.28 35.28 Ul Blowout Panel 15.70 15.70 UlRWST 19.68 19.68 Ul ui ment Hatch 8.36 8.36 Intake-to-Source Distances (m)

Ul Containment to TSC 371.25 36.28 Vent Stack A to TSC 444.54 32.87 Vent Stack B to TSC 439.24 26.17 Ul Blowout Panel to TSC 425.44 68.73 Ul RWST to TSC 377.91 44.03 Ul ui ment Hatch to TSC 379.14 Direction from Intake to Source (degrees)

Ul Containment 280 152.43 VentStackA 284 233.73 VentStackB 285 233.67 Ul Blowout Panel 278 185.14 UlRWST 285 114.72 Ul E ui ment Hatch 278 True North Correction (degrees) -23.207 Included in directions above

-~; : : '.,~.,\"a~'.<~Ll~!:!~~j~~!!1~~~;(.**

Ul RWST Vent to TSC Emergency Intake X/Q 0-2 hours 6.13E-05 2.40E-03 2-8 hours 4.98E-05 l.SSE-03 8-24 hours 1.67E-05 5.27E-04 24-96 hours l.47E-05 4.20E-04 96-720hours 1.22E-05 2.97E-04 Vent Stack A to TSC Emergency Intake X/Q 0-2 hours 5.02E-05 4.02E-03 2-8 hours 3.41E-05 3.24E-03 8-24hours 1.18E-05 1.25E-03 24-96hours 9.70E-06 9.48E-04 96-720hours 8.17E-06 7.40E-04 Page 6 of 14

Serial No.23-045 Docket Nos.: 50-338/339 Attachment 1 Vent Stack B to TSC Emergency Intake X/Q 0 2 hours2.314815e-5 days 5.555556e-4 hours 3.306878e-6 weeks 7.61e-7 months 5.12E-05 5.67E-03 2-8 hours 3.46E-05 4.46E-03 8-24 hours 1.20E-05 1.73E-03 24-96 hours 9.93E-06 l.33E-03 96-720 hours 8.28E-06 l.0lE-03 Ul Blowout Panel to TSC Emergency Intake XJQ 0-2 hours 5.16E-05 1.16E-03 2-8 hours 4.25E-05 9.43E-04 8-24 hours 1.36E-05 3.85E-04 24-96hours 1.24E-05 2.63E-04 96-720hours 1.03E-05 1.97E-04 Ul Containment to TSC Emergency Intake X/Q 0-2 hours 5.63E-05 1.34E-03 2-8 hours 4.62E-05 9.43E-04 8 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months l.52E-05 3.74E-04 24 -** 96 hours0.00111 days 0.0267 hours 1.587302e-4 weeks 3.6528e-5 months 1.36E-05 2.64E-04 96 720hours l.13E-05 2.03E-04 Ul Equipment Hatch to TSC Emergency Intake X!Q 0-2 hours 5.88E-05 Not explicitly 2-8 hours 4.88E-05 considered - excluded 8-24 hours l.61E-05 by geometry and only 24-96 hours 1.44E-05 used for fuel handling 96 720 hours0.00833 days 0.2 hours 0.00119 weeks 2.7396e-4 months 1.21E-05 accident releases.

1 For TSC specific inputs, "Implementation of AST" refers to the use of AST acceptable inputs in the TSC dose analyses rather than docketed inputs with respect to the TSC dose.

2 The True North correction of -36 degrees from Reference [4] was based on protractor measurement from a site drawing. The True North correction of-23.207 degrees was based on an indicated value from a different site drawing that was converted from Plant North to Va North and Va North to True North based on USGS data.

3 The RWST vent X/Qs are the only X/Q values used to determine dose to the relocated TSC. X/Qs for the current TSC are shown for comparison to the values calculated for the relocated TSC.

Page 7 of 14

Serial No.23-045 Docket Nos.: 50-338/339 Attachment 1 Table 5-2: Summary of Changes for TSC Relocation LOCA Dose Core inventory 110 isotopes total 94 isotopes Added: Table 3.1-3, {2]

Am-242, Ba-141, Co-58, Co-60, Cs-134m, Eu-154, Eu-155, La-143, Np-238, Pd-109, Pm-151, Pr-144m, Pu-243, Sb-124, Sb-126, Tc-101, Te-133m, Te-134, Y-94, and Y-95 Removed: Ag-11 Om, Cs-135, Kr-89, and Xe-137 (Reproduced in Attachment 1-A Fuel Design Westinghouse 17xl 7 Westinghouse 17xl 7 RFA-2 RFA-2 Section 15.3.1.4, 6 Fuel T e 4.2-5.0 4.4-4.55 0.462 0.466 Thermal Power (MWt) 2958 2958 Including 0. 6% calorimetric Table 15.4-9, {6}

uncertain End of Cycle Core Average Bumup 42.0 38.9 GWD/MTU Release from fuel Tables 2 and 4, Containment Leakage Chemical Release Form 95% aerosol (Section 3.5 of Reg. Guide 1.183) 4.85% elemental 4.85% elemental 0.15% organic 0.15% organic Table 3.1-1, 2 ECCS Leakage Chemical Release Form 97% elemental 97% elemental (Appendix A of Reg. Guide 1.183, [7]) 3% organic 3% organic Section 3.1.5.2, 2 RWST Leakage Chemical Release Form 97% elemental 97% elemental A endixA of Re . Guide 1.183, 7) 3% or anic 3% or anic Dose conversion factors FGR 11 and 12 FGR 11 and 12 Att. 1 Section 4, {8 Containment net free air volume (ft3) 1.916 million 1.916 million Att. 1 Section 4.2, 8 Page 8 of 14

Serial No.23-045 Docket Nos.: 50-338/339 Attachment 1 Fraction of containment volume that is sprayed (%) Att. I Section 4.2, {8]

73 seconds - 40 minutes 37.6% 37.6%

40 minutes - 1.5 hours5.787037e-5 days 0.00139 hours 8.267196e-6 weeks 1.9025e-6 months 83.8% 83.8%

1.5 hours5.787037e-5 days 0.00139 hours 8.267196e-6 weeks 1.9025e-6 months 6 hours 73.1% 73.1%

Exchange rate between sprayed and unsprayed (cfm) 73 seconds - 40 minutes 39,867 39,867 40 minutes - 1.5 hours5.787037e-5 days 0.00139 hours 8.267196e-6 weeks 1.9025e-6 months 10,347 10,347 1.5 hours5.787037e-5 days 0.00139 hours 8.267196e-6 weeks 1.9025e-6 months - 720 hours0.00833 days 0.2 hours 0.00119 weeks 2.7396e-4 months 17,180 17,180 (2x Unsprayed Volume/hr, Assumption 3.3, Table 15.4-9, {6}

A . A of Re . Guide 1.183, 7 Natural deposition coefficient for aerosol in Not analyzed Not analyzed uns ra ed re ion of containment our-1 Section 15.4. 1. 9.2, 6 Beginning of containment spray and 73 seconds 73 seconds mixin between s ra ed and uns ra ed Att. 1 Table 4.2-1, 8 Duration of containment spray (hours) Att. 1 Sections 4, 4.3, [8]

Organic Iodine NIA NIA Elemental Iodine (time to reach DF = 200) 2.33 2.33 Particulate/aerosol 720 7202 Spray removal coefficient (hours*1)2 Att. 1 Table 4.3-3, [8]

Organic iodide Zero Zero Elemental iodine 10 10 Particulate/aerosol 73 seconds -0.556 hours0.00644 days 0.154 hours 9.193122e-4 weeks 2.11558e-4 months 5.832 5.832 0.556 0.667 hours0.00772 days 0.185 hours 0.0011 weeks 2.537935e-4 months 6.167 6.167 0.667 - 0.833 hour0.00964 days 0.231 hours 0.00138 weeks 3.169565e-4 months s2 12.34 12.34 0.833- 1.11 hour1.273148e-4 days 0.00306 hours 1.818783e-5 weeks 4.1855e-6 months s1 12.45 12.45 1.11 - 1.39 hour4.513889e-4 days 0.0108 hours 6.448413e-5 weeks 1.48395e-5 months s2 12.45 12.45 1.39 - 1.50 hour5.787037e-4 days 0.0139 hours 8.267196e-5 weeks 1.9025e-5 months s2 12.34 12.34 1.50 - 1.80 hours9.259259e-4 days 0.0222 hours 1.322751e-4 weeks 3.044e-5 months 11.87 11.87 1.80 - 1.88 hours0.00102 days 0.0244 hours 1.455026e-4 weeks 3.3484e-5 months 7.565 7.565 1.88 - 1.97 hours0.00112 days 0.0269 hours 1.603836e-4 weeks 3.69085e-5 months 5.285 5.285 1.97 -2.35 hours4.050926e-4 days 0.00972 hours 5.787037e-5 weeks 1.33175e-5 months 2.821 2.821 2.35 - 3.82 hours9.490741e-4 days 0.0228 hours 1.35582e-4 weeks 3.1201e-5 months 1.534 1.534 3.82-5.46 hours5.324074e-4 days 0.0128 hours 7.60582e-5 weeks 1.7503e-5 months 1.370 1.370 5.46 - 7.13 hour1.50463e-4 days 0.00361 hours 2.149471e-5 weeks 4.9465e-6 months s2 1.350 1.350 Containment leak rate (percent per day) Att. 1 Table 4.1-1, {8}

first hour 0.10 0.10 1- 6 hours6.944444e-5 days 0.00167 hours 9.920635e-6 weeks 2.283e-6 months 0.04 0.04 Filter efficienc ,

Control Room Att. 1 Section 4, [8]

Organic iodine 95% 95%

Elemental iodine 95% 95%

Particulate/aerosol 98% 98%

Page 9 of 14

Serial No.23-045 Docket Nos.: 50-338/339 Attachment 1 Technical Support Center for dose detennination3 Organic iodine 95% 99%

Elemental iodine 95% 99%

Particulate/aerosol 95% 99%

for filter inventory (shine dose analysis)

Organic iodine 99% 99%

Elemental iodine 99% 99%

Particulate/aerosol 99% 99%

Auxiliary Building (PREACS) Att.1 Section 4, [8]

Organic iodine 90%

Elemental iodine 95%

Particulate/aerosol 98%

. :--~~~::**::~~ ~~~:~?\~-:;_~,~ ~'.*. '::~ :.... ..

Effective volume (:ft:3) 79,100 79,100 Att. 1 Section 4. 9, 8 Filtered inflow from environment (c:fin) Att. 1 Section 4, [8]

first hour 0 0 after first hour 900 900 Unfiltered inleakage (cfin) 250 250 Att. 1 Section 4, 8 Time delay (minutes) Table 1.3-1, [2]

To isolate 0 0 To ressurize 60 60 Recirculation Flow (cfin) 0 0 Att. 1 Section 4, 8 Vent Stack to CR Emergency Intake X/Q Table 5, [4]

(sec/m3) 0-2 hours 3.75E-03 3.75E-03 2-Shours 2.65E-03 2.65E-03 8-24 hours 1.03E-03 l.03E-03 24-96hours 7.77E-04 7.77E-04 96-720hours 5.70E-04 5.70E-04 RWST Vent to CR Emergency Intake XJQ Table 5, [4]

(sec/m3) 0-2hours 2.18E-03 2.18E-03 2-8hours l.42E-03 1.42E-03 8-24 hours 4.898-04 4.89E-04 24-96hours 3.848-04 3.84E-04 96-720hours 2.72E-04 2.728-04 Page 10 of 14

Serial No.23-045 Docket Nos.: 50-338/339 Attachment 1 Containment to CR Emergency Intake X/Q Table 5, [4]

(sec/m3) 0 2 hours2.314815e-5 days 5.555556e-4 hours 3.306878e-6 weeks 7.61e-7 months 1.23E-03 l.23E-03 2-8 hours 9.02E-04 9.02E-04 8 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months 3.57E-04 3.57E-04 24-96 hours 2.SSE-04 2.55E-04 96-720hours l.91E-04 1.91E-04 Filtered inflow ( cfm)

Operational Flow Range 405-1000+/- 10%

Before isolation (unfiltered) 1100 After isolation 365 Immediate Isolation Cases Constant 11004 1000 Unfiltered inleaka e cfm 0 0 Time delay to enter emergency 0.5 (60 and 90 minute 0 operation/isolation/filtration (minutes) manual isolations also anal ed Recirculation Flow cfm) 0 0 Construction Details Wall Thickness (ft) 1.0 1.0 Wall Material Grout-filled CMU, Concrete Brick, and Mortar Roof Thickness (ft) 1.0 1.0 Roof Material Concrete Concrete Building Pressure in Emergency Operation 0.125 Positive inw..

Entryway Details Vestibule with Double Vestibule with Double Doors Doors Breathing rates ( cubic meters/second) Section 4.1.3, {7} Att. 1 Section 4, {8}

Control room (all the time) 3.5 x I0-4 3.5 X 10-4 TSC (all the time) 3.5 X 10-4 3.5 X 104 offsite Section 4.1.3, {7] Att. 1 Section 4, [8]

0-8 hours 3.5 X 104 3.5 X 104 8-24hours 1.8 X 104 1.8 X 104 after 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months 2.3 X 10-4 2.3 X 104 Control Room Occupancy factors Section 4.2.6, {7} Att. 1 Section 4, {8}

First day 1.0 1.0

. between 1 to 4 days 0.6 0.6 after 4 da: s 0.4 0.4 TSC Occupancy factors 0-24 hours 1.0 1.0 24-96hours 1.0 0.6 96-720hours 1.0 0.4 Page 11 of 14

Serial No.23-045 Docket Nos.: 50-338/339 Attachment 1 Offsite X/Qs {sec/m3) Table 1, [3]

Exclusion Area Boundary 0-720 hours 3.lOE-04 3.lOE-04 Low Population Zone 0-8 hours 1.lOE-05 l.lOE-05 8-24hours 7.30E-06 7.30E-06 24-96hours 3.00E-06 3.00E-06 96-720hours 8.20E-07 8.20E-07 Unfiltered ECCS leakage (cc/hr)5 Automatic HVAC Isolation Case 0-720hours 1700 1700 [CR & LPZ]

Manual HVAC Isolation Case 0-1 hour 17,200 17,200 [BAB]

1-720hours 0 0 AB Filtered ECCS leakage (cc/hr) [PREACS]5 Automatic HVAC Isolation Case 0-720 hours 0 0 [CR&LPZ]

Manual HVAC Isolation Case 0-1 hour 0 0 [BAB]

1-720 hours 17 200 17,200 AB Containment sump liquid volume (ft') Att. 1 Table 4.4-1, [8]

840-1,500 seconds 16,800 16,800 1,500 - 1,900 seconds 25,700 25,700 1,900 - 2,500 seconds 31,400 31,400 2,500 - 3,000 seconds 39,900 39,900 3,000 - 4,000 seconds 46,800 46,800 4,000 - 5,000 seconds 60,000 60,000 5,000 - 6,000 seconds 68,800 68,800 6,000 - 8,000 seconds 73,200 73,200 8 000+ seconds 76000 76 000 RWST Breathing Rate (Suppression Pool Model) Att. 1 Section 4.5, [8]

Flow rate (cfm) 3.7 3.7 Duration hours 0.533-720 0.533-720 RWST Decontamination Factor 40 40 Att. 1 Section 4. 5, 8 Fraction of activity in ECCS liquid leakage released 10% 10%

as airborne Section 3.1.5.2, 2 ECCS back-leakage into RWST during recirc 2400 (480 + 1920) 480 via recirc lines (cc/hr)' 1920 via LHSI suction line Att. 1 Section 4.5, 8 Maximum RWST air volume {ft') 6.5850E+04 6.5850E+04 (492,600 gal)

Section 4.5, 8 Page 12 of 14

Serial No.23-045 Docket Nos.: 50-338/339 Attachment 1 Containment shine, Containment shine, Containment skyshine, Containment sk.yshine, SI Sources of shine dose to TSC personnel plume/cloud, and HVAC piping,Hydrogen filters Recombiner Vault, plume/cloud, HVAC filters Containment Construction Wall Concrete Thickness (ft) 4.5 Not listed Wall Steel Liner Thickness (in) 0.375 Not listed Dome Concrete Thickness (ft) 2.5 2.5 Dome Steel Liner Thickness in 0.5 Not listed 1 For TSC specific inputs, "Implementation of AST" refers to the use of AST acceptable inputs in the TSC dose analyses rather than docketed inputs with respect to the TSC dose.

2 Due to a previous limitation in RADTRAD-NAI, table inputs could not exceed 10 time-dependent values; therefore, an aerosol removal coefficient value of 12.34 hr-1 was conservatively used from 0.667 - 1.50 hours5.787037e-4 days 0.0139 hours 8.267196e-5 weeks 1.9025e-5 months . Also, the last entry of 1.35 hr1 remains in effect until problem duration of720 hours. Since containment is subatmospheric by 6 hours6.944444e-5 days 0.00167 hours 9.920635e-6 weeks 2.283e-6 months , this has no impact on the result.

3 The TSC charcoal filter efficiency was reduced due to the new TSC location having 2" charcoal filters versus the existing TSC use of 411 charcoal filters. Assumed HEPA filter efficiency for particulate removal is conservative.

4 Filtration is delayed 30 seconds for damper operation in the immediate isolation cases for the new TSC.

5 ECCS leakage modeling is described in references [2] and [8]. The ECCS leakage analysis has not changed from Reference

[8]. The analysis has two limiting scenarios relevant to the TSC dose: 1) allowable unfiltered ECCS leakage of 1700 cc/hr, or

2) allowable filtered ECCS leakage of 17,200 cc/hr with filtration delayed 1 hour1.157407e-5 days 2.777778e-4 hours 1.653439e-6 weeks 3.805e-7 months . Modeled leak rates are twice the allowable (3400 cc/hr unfiltered and 34,400 cc/hr), which were input into RADTRAD-NAI as 0.002 cfin and 0.02025 cfin, respectively.

Evolution is modeled by specifying a source fraction of 0.1. Filtration ofECCS leakage is accomplished by manual initiation of the Auxiliary Building ventilation (PREACS) filters at 1 hour1.157407e-5 days 2.777778e-4 hours 1.653439e-6 weeks 3.805e-7 months .

6 RWST allowable leakage is 1200 cc/hr. RWST modeled leakage of2400 cc/hr was input into RADTRAD-NAI as 3.533E-5 cfm after reduction based on DF of 40 inside the tank.

Page 13 of 14

Serial No.23-045 Docket Nos.: 50-338/339 Attachment 1 6.0 References

1. NUREG-0737, "Clarification of TMI Action Plan Requirements", November 1980.

2. Letter from Virginia Electric and Power Company to the USNRC (Serial No. 04-494A) dated November 3, 2004, "Virginia Electric and Power Company (Dominion),

North Anna Power Station Units 1 and 2, Response to Request for Additional Information, Proposed Technical Specification Changes, Implementation of Alternate Source Term Revised Dose Analysis and Technical Specification Changes." [ML043150026]

3. Letter from the USNRC to Virginia Electric and Power Company dated June 15, 2005, "North Anna Power Station, Units 1 and 2 - Issuance of Amendments on Implementation of Alternate Source Term (TAC Nos. MC0776 and MC0777)."

[ML05159051 O]

4. Letter from Virginia Electric and Power Company to the USNRC (Serial No. 03-464A) dated November 20, 2003, "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."

[ML033350516]

5. Regulatory Guide 1.194, Revision 0, "Atmospheric Relative Concentrations for Control Room Radiological Habitability assessments at Nuclear Power Plants", June 2003.

6. North Anna Updated Final Safety Analysis Report, Revision 58, September 2022.

7. Regulatory Guide 1.183, Revision 0, "Alternative Radiological Source Terms for Evaluating Design Basis Accidents at Nuclear Power Reactors", July 2000.

8. Letter from Virginia Electric and Power Company to the USN RC (Serial No.06-849) dared October 3, 2006, "Virginia Electric and Power Company (Dominion), North Anna Power Station Units 1 and 2, Proposed Technical Specification Change and Supporting Safety Analyses Revisions to Address Generic Safety Issue 191."

[M L062850195]

9. Letter from the USNRC to Virginia Electric and Power Company dated March 13, 2007, "North Anna Power Station, Units 1 and 2 - Issuance of Amendments Regarding Technical Specification Changes Per Generic Safety Issue (GSI) 191 (TAC Nos. MD3197 and MD3198)." [ML070720043]

Page 14 of 14

Serial No.23-045 Docket Nos.: 50-338/339 Attachment 1-A Updated North Anna Core Inventory Isotope No. Isotope Activity (Ci) 1 Kr-83m l.O0E+07 2 Kr-85 9.09E+o5 3 Kr-85m 2.23E+07 4 Kr-87 4.28E+07 5 K.r-88 5.80E+o7 6 Xe-13lm 9.6lE+05 7 Xe-133 1.60E+08 8 Xe-133m 5.03E+o6 9 Xe-135 4.96E+o7 10 Xe-135m 3.49E+07 11 Xe-138 l.41E+08 12 Br-82 2.97E+05 13 Br-83 9.98E+06 14 Br-84 1.74EI 07 15 I-130 1.58E+06 16 I-131 7.99E+07 17 1-132 l.16E+o8 18 I-133 l.64E+08 19 I-134 1.85E+08 20 I-135 l.57E+08 21 Rb-86 1.80E+05 22 Rb-88 5.89E+07 23 Rb-89 7.73E+07 24 Cs-134 1.68E+07 25 Cs-134m 4.73E+06 26 Cs-136 3.82E+06 27 Cs-137 9.72E+06 Page 1 of 4

Serial No.23-045 Docket Nos.: 50-338/339 Attachment 1-A Isotope No. Isotope Activity (Ci) 28 Cs-138 1.54E+o8 29 Sb-125 8.22E+o5 30 Sb-126 3.51E+o4 31 Sb-127 7.69E+o6 32 Sb-129 2.30E+o7 33 Te-125m l.7SE+o5 34 Te-127 6.90E+o6 35 Te-J27m 5.43E+o5 36 Te-129 2.19E+o7 37 Te-129m 3.75E+o6 38 Te-131 6.8SE+o7 39 Te-131m 1.56E+o7 40 Te-132 l.14E+o8 41 Te-133 8.28E+o7 42 Sr-89 8.08E+o7 43 Sr-90 7.09E+06 44 Sr-91 l.OOE+o8 45 Sr-92 1.07E+o8 46 Ba-137m 9.25E+o6 47 Ba-139 1.47E+o8 48 Ba-140 1.42E+o8 49 Ba-141 1.32E+o8 50 Pd-109 2.93E+07 51 Ag-111 5.52E+o6 52 Mo-99 1.49E+o8 53 Rh-103m l.28B+o8 54 Rh-105 8.41E+o7 55 Rh-106 5.37E+o7 56 Ru-103 l.29E+o8 Page 2 of4

Serial No.23-045 Docket Nos.: 50-338/339 Attachment 1-A Isotope No. Isotope Activity (Ci) 57 Ru-105 9.19E+07 58 Ru-106 4.66E+07 59 Tc-99 l.23E+03 60 Tc-99m l.32E+08 61 Tc-101 1.38E+08 62 Ce-141 l.33E+o8 63 Ce-143 I.26E+08 64 Ce-144 l.03E+08 65 Np-239 1.60£+09 66 Pu-238 3.61E+05 67 Pu-239 2.64E+04 68 Pu-240 2.66E+04 69 Pu-241 l.30E+07 70 Am-241 l.33E+04 71 Cm-242 4.87E+o6 72 Cm-244 6.17E+05 73 Eu-156 2.17E+07 74 La-140 l.47E+08 75 La-141 l.33E+08 76 La-142 l.29E+08 77 La-143 l.25E+08 78 "Nb-95 l.38E+08 79 "Kb-95m l.51E+06 80 Nb-97 l.37E+08 81 Nb-97m l.30E+o8 82 Nd-147 5.25E+07 83 Pm-147 l.46E+07 84 Pm-148 1.74E+07 85 Pm-148m 2.94E+06 Page 3 of 4

Serial No.23-045 Docket Nos.: 50-338/339 Attachment 1-A Isotope No. Isotope Activity (Ci) 86 Pm-149 4.39E+o7 87 Pr-143 l.22E+08 88 Pr-144 l.04E+08 89 Pr-144m l.46E+06 90 Sm-153 3.79E+o7 91 Y-90 7.37E+06 92 Y-91 l.04E+08 93 Y-91m 5.90E+07 94 Y-92 l.08E+08 95 Y-93 l.21E+08 96 Y-94 l.27E+o8 97 Y-95 l.32E+08 98 Zr-95 l.37E+08 99 Zr-97 l.36E+08 100 Sb-124 7.34E+04 101 Te-133m 8.32E+07 102 Te-134 l.49E+o8 103 Co-58 0.00E+00 104 Co-60 0.00E+00 105 Eu-154 6.63E+05 106 Eu-155 3.58E+o5 107 Pm-151 l.58E+07 108 Am-242 8.68E+o6 109 Np-238 3.75E+o7 110 Pu-243 4.30E+07 Page 4 of 4

Serial No.23-045 Docket Nos.: 50-338/339 Attachment 2 LISTS AND DESCRIPTIONS OF FILES INCLUDED ON THE ENCLOSED CD-ROM SUPPORTING THE RELOCATED TSC LOCA DOSE CALCULATION Virginia Electric and Power Company (Dominion Energy Virginia)

North Anna Power Station Units 1 and 2

Serial No.23-045 Docket Nos.: 50-338/339 Attachment 2 LISTS AND DESCRIPTIONS OF FILES INCLUDED ON THE ENCLOSED CD-ROM SUPPORTING THE RELOCATED TSC LOCA DOSE CALCULATION CD-ROM contents:

The enclosed CD-ROM contains a zip file named North Anna Computer 1O.zip. The following table describes the contents of the zip file on the enclosed CD-ROM.

North Anna Computer Files File Name Description

..., . ; >lW)T~~Affiles (.p~f;;:.11if;,dwp/.dd,:ftft,*.oht)°. .. '

.,., *. **i, ... ,*, :t *'::;; . '. .~:<]~ ~-;*,~ . : . .::. .t~* ..; _.,: *. ' . .';..i,:,:;;.,:, .. ; ' c.;:, '_.,, *~ .. .. *:. _t,,;"_, -,-~*'. - :;. ".

naps_ctmt_ TSC.psf LOCA containment leakage model for TSC dose with automatic isolation at thirty seconds.

Naps_eccs_TSC.psf LOCA ECCS leakage model for TSC dose with automatic isolation at thirty seconds.

Naps_rwst_TSC.psf LOCA RWST leakage model for TSC dose with automatic isolation at thirty seconds.

Naps__ ctmt_TSC_jso!60.psf LOCA containment leakage model for TSC close with manual isolation at 60 minutes into the accident.

Naps_eccs_TSC_Isol60.psf LOCA ECCS leakage model for TSC dose with manual isolation at 60 minutes into the accident.

Naps_nvst__ T..'iC_Jso/60.psf LOCA RWST leakage model for TSC dose with manual isolation at 60 minutes into the accident.

Naps_ ctmt_ TSC_Isol90.psf LOCA containment leakage model for TSC dose with manual isolation at 90 minutes into the accident.

Naps_ eccs_ TSC_jsol90.psf LOCA ECCS leakage model for TSC dose with manual isolation at 90 minutes into the accident.

Naps_rwst_ TSC_Isol90.psj LOCA RWST leakage model for TSC dose with manual isolation at 90 minutes into the accident.

Naps_ctmt_TSC..}9.p~f LOCA containment leakage model for maximum TSC filter loading with automatic isolation at thirty seconds.

Naps_eccs_TSC_99.psf LOCA ECCS leakage model for maximum TSC filter loading with automatic isolation at thirty seconds.

Naps_rwst_TSC_JJ9.psf LOCA RWST leakage model for maximum TSC filter loading with automatic isolation at thirty seconds.

NAPS_Core.nif Nuclide inventory file upconverted and reformatted for use with RADTRAD-NAI Version 1.3.

NAPSJgrl 1&12.inp Dose conversion factor file.

Page 1 of 3

Serial No.23-045 Docket Nos.: 50-338/339 Attachment 2 File Name Description Na__pwr_ dba.rft Release fraction timing file for containment leakage during a LOCA.

Na_iodine_ only.rft Release :fraction timing file for ECCS leakage and RWST backleakage during a LOCA.

cont- shine- XX.msd Micro Shield case file for determination of containment shine to TSC personnel.

Four subcases are derived from the base model for various times in hours from the start of the event indicated by the two-digit suffix (XX).

Filename.mxd External source files for use in MicroShield.

Filename.pd/ MicroShield Output files.

cont_sky_XX.sky Case file for determination of skyshine from containment to TSC personnel. Two subcases are derived from the base model for various times in hours from the start of the event indicated by the two-digit suffix (XX).

Cont_sky_XX.pd/ MicroSkyshine Output File NI CNTLEOF.RSF ARCON96 run specification file for UI source NI CNTLEOF.log ARCON96 output file for Ul source NlCNTLEOF.cfd ARCON96 cumulative frequency distribution file for Ul source NAVTALEOF.RSF ARCON96 run specification file for VA source NAVTALEOF.log ARCON96 output file for VA source NAVTALEOF.cfd ARCON96 cumulative frequency distribution file for VA source NAVTBLEOF.RSF ARCON96 run specification file for VB source NAVTBLEOF.log ARCON96 output file for VB source NAVTBLEOF.cfd ARCON96 cumulative frequency distribution file for VB source NlBLPLEOF.RSF ARCON96 run specification file for B 1 source NlBLPLEOF.log ARCON96 output file for Bl source NlBLPLEOF .cfd ARCON96 cumulative frequency distribution file for B 1 source NlRWTLEOF.RSF ARCON96 run specification file for RI source Page 2 of 3

Serial No.23-045 Docket Nos.: 50-338/339 Attachment 2 File Name Description NlRWTLEOF.log ARCON96 output file for Rl source NlRWTLBOF.cfd ARCON96 cumulative frequency distribution file for Rl source NlEQHLEOF.RSF ARCON96 run specification file for El source NlEQHLEOF.log ARCON96 output file for El source

. NlEQfilEOF.cfd ARCON96 cumulative frequency distribution file for El source NA9701MET2 North Anna Meteorological Data file Page 3 of 3

Serial No.23-045 Docket Nos.: 50-338/339 Attachment 3 NORTH ANNA X/Q GEOMETRY FOR THE RELOCATED TSC Virginia Electric and Power Company (Dominion Energy Virginia)

North Anna Power Station Units 1 and 2

Serial No.23-045 Docket Nos.: 50-338/339 Attachment 3 NORTH ANNA X/Q GEOMETRY FOR THE RELOCATED TSC Ap,-VA.N HIIIIS£St RAn IIAU.F"IS.

WC£ WTit RSlllt LEOF Prooosed TSC Unit 1 Unit 1 Containment Unit2 Unit 2 Containment VA Ventilation Stack A VB Ventilation Stack B 81 Blowout panel Unit 1 RWST Unit 1 Refuelina Water Storaae Tank EQ Eauioment Hatch

Serial No.23-045 Docket Nos.: 50-338/339 Attachment 4 TECHNICAL BASIS FOR ELIMINATION OF TSC CO2 FIRE PROTECTION SYSTEM Virginia Electric and Power Company (Dominion Energy Virginia)

North Anna Power Station Units 1 and 2

Serial No.23-045 Docket Nos.: 50-338/339 Attachment 4 TECHNICAL BASIS FOR ELIMINATION OF TSC CO2 FIRE PROTECTION SYSTEM The relocated TSC facility is designed to meet the requirements of NUREG-0696, "Functional Criteria for Emergency Response Facilities," (1981), and NUREG-0737, Supplement 1, "Requirements for Emergency Response Capability," (1982). NUREG-0696 specifies the need for a TSC ventilation system that includes charcoal filters but does not specify requirements for fire protection of the filters. However, other documents provide limited guidance for the fire protection of charcoal filters including Regulatory Guide (RG) 1.189, 11 Fire Protection for Nuclear Power Plants," (2009) and ASME AG-1, 11 Code on Nuclear Air and Gas Treatment," (2019). RG 1.189 states that any filter (not installed in an Engineered-Safety-Featured Atmosphere Cleanup System) that includes combustible materials and is a potential exposure fire hazard that may affect components important to safety should be protected as determined by the fire hazards analysis. The same direction is provided within section AB-5170 of ASME AG-1, which indicates designated filter fire protection systems are to be provided based on the plant fire hazard analysis. Additional guidance is provided within RG 1.140, "Design, Inspection, and Testing Criteria for Air Filtration and Adsorption Units of Normal Atmosphere Cleanup Systems in Light-Water-Cooled Nuclear Power Plants," (2016) which states prevention and mitigation of auto-ignition should be considered and includes a water~based fire suppression system as an option if needed. The fire hazard analysis in the North Anna Appendix R Report currently identifies a localized CO2 fire suppression system for the activated carbon filter in the existing TSC. However, a CO2 fire suppression system is not necessary for the relocated TSC since the TSC: 1) is not required for safe shutdown,

2) contains other fire protection measures, and 3) is unlikely to experience a HEGA filter fire.

The installation of a designated fire suppression system in the HEGA filter would be to extinguish a fire that developed in the activated carbon bed. However, it is unlikely a fire would occur in this area of the HVAC system during normal system operation as it is only in use during an accident condition in which the outside air needs to be filtered of radiological contaminants. If the need for radiological filtration arises, the possibility for a fire in the HEGA filter increases due to the resulting decay heat from the radionuclides deposited on the activated carbon beds. If the decay heat is significant, the activated carbon could reach its ignition temperature thus causing a fire. Consequently, to determine if the ignition temperature could be reached, the total decay heat load was calculated based on the radionuclide inventory across all filters in the HVAC system. It assumes that energy from all potential emissions or reactions are locally deposited, which is conservative as photon-based emissions are likely to escape the filter media. Based on these assumptions, the total decay heat load across all filters was calculated to be 9.01E-04 watts or 3.0SE-03 BTU/hr. Even by conservatively assuming the entirety of this heat load is gained by a single carbon bed in the HEGA filter, this heat load is very small and is unlikely to increase the temperature of the activated charcoal filter by any significant amount. In addition to this minimal heat load, the TSC HVAC system is capable of providing 1,000 cubic feet per minute (CFM) airflow during emergency operation. Such airflow through the HEGA filter would provide sufficient cooling of the decay heat load and limit the temperature increase of the activated carbon beds. Thus, there is no significant increased fire risk in the activated carbon beds due to the filtered Page 1 of 3

Serial No.23-045 Docket Nos.: 50-338/339 Attachment 4 radionuclides.

In the event a fire does ignite in the TSC Penthouse where the HEGA filter is located, there is no risk to the safe shutdown of the plant as it does not contain safety-related equipment or any equipment required for fire safe shutdown. The remainder of the relocated TSC and the adjacent Training Building also do not contain any such equipment, and thus pose no risk to safe shutdown if a TSC Penthouse fire were to somehow spread to these areas.

Should a HEGA filter fire occur without a designated CO2 suppression system installed, the activated carbon would be damaged and would require replacement once the fire had been extinguished. If the filter fire were extinguished via water suppression, the filter efficiency would be significantly reduced due to the resulting saturation and increased local humidity. These issues could be mitigated by a CO2 suppression system and result in a more timely recovery of the filter; however, there is no requirement specifying a recovery time for atmospheric cleanup systems following a fire. Additionally, as the new TSC does not contain any safe shutdown equipment, it can be evacuated if the space becomes unfit for human habitation. In the unlikely event TSC occupants are exposed to radioactive contaminants during a HEGA filter fire (or after it has been extinguished), the area can be evacuated without risk to safe shutdown of the plant.

If a fire does occur in the charcoal filter, there are several fire protection measures in place that alleviate the need for a dedicated CO2 suppression system. The HEGA filter is fitted with heat detection that alarms at the relocated TSC fire protection panel, the existing fire protection panel in the adjacent Training Building, and the Security Alarm Station (SAS). Upon reaching a temperature of 190°F, the heat detection actuates the Emergency Power Off (EPO) panel which de-energizes both the emergency supply fan and motor operated dampers, isolating the HEGA filter.

Additionally, cross-zoned smoke detectors are installed in the supply and return ventilation ducts and in the Penthouse area. These detectors alarm in the same locations as the heat detection. Upon smoke detection by two of the cross-zoned smoke detectors, the air handling unit (AHU) is de-energized and motor operated dampers are modulated closed to limit the spread of smoke or fire to other areas of the TSC. As the HEGA filter is located upstream of the supply duct smoke detector, a fire at that location would trip theAHU.

In addition, the Penthouse is served by the TSC pre-action fire suppression system. This system is designed in compliance with NFPA 13 and consists of four sprinklers with a design area of discharge that covers the entirety of the Penthouse. These sprinklers are actuated automatically by the local area smoke detectors. Fire protection is also provided by the station Fire Brigade in accordance with station Fire Protection Program requirements. The Fire Brigade has access to the two Training Building fire hydrants1 1-FP-HYD-100 and 1-FP-HYD-101, to aid in the suppression of fires in the TSC and TSC Penthouse should they be required. Hydrant 1-FP-HYD-100 is located on the west side of the Training Building, approximately 182 feet from the Penthouse, and hydrant 1-FP-HYD-101 is located on the east side of the Training Building, approximately 228 feet from the Penthouse.

Page2 of3

Serial No.23-045 Docket Nos.: 50-338/339 Attachment 4 The construction and location of the Penthouse also offers some passive fire protection that can slow the spread of a fire from the space. The Penthouse is located on the roof of the TSC and only its floor is adjacent to the remainder of the TSC facility. The floor of the Penthouse is constructed of 12-inch-thick reinforced concrete and designed to prevent the spread of radiological contaminants to the occupied areas of the TSC. As a result, the floor can also impede the spread of fire. Per the Concrete Reinforcing Steel Institute - (CRSI) [2015], "Fire Resistance of Reinforced Concrete Buildings," Table 1 of Technical Note ETN-B-1-16, a reinforced siliceous concrete floor with a thickness of about 6.2 inches provides a 3-hour fire rating. Given the Penthouse floor thickness of 12 inches, it provides an equivalent construction of greater than 3 hours3.472222e-5 days 8.333333e-4 hours 4.960317e-6 weeks 1.1415e-6 months , which would slow the spread of a fire from the Penthouse to the remainder of the TSC. Note that because the Penthouse floor is not a rated fire barrier, its associated penetrations are not designed to a particular fire rating and are thus assumed to not be fire rated.

Based on the equipment installed in the Penthouse, it is expected the associated fire loading maintains an Equivalent Fire Severity (EFS) of Low since a fire area is considered to have a Low EFS when its associated fire load is below 100,000 BTU/ft2. The TSC Penthouse occupies a space of approximately 490.6 square feet and would thus require a heat release of 49,060,000 BTU to reach this fire loading threshold. Conservatively assuming that all of the combustible equipment in the Penthouse is general plastic (heat of combustion of 15,750 BTU/lb), approximately 3,115 lbs of general plastic is required to meet this heat release. The combustible equipment installed in the Penthouse is limited to the HVAC filters (prefilter, HEPA filter, and activated carbon from the HEGA filter), a variable frequency drive and small electronic devices such as smoke and heat detectors.

Since the combined weight of the filter equipment and variable frequency drive is approximately 172 lbs, the combustible equipment in the Penthouse remains well below 3,115 lbs, and therefore, the EFS of the space is determined to be Low.

Conclusion Based on this evaluation, a designated CO2 fire suppression system for the TSC HEGA activated carbon filter is neither required nor warranted. The probability of ignition of the HEGA filter is minimal based on the insignificant radiological decay heat load and sufficient emergency operation airflow. In the unlikely event auto-ignition of the charcoal filter were to occur, heat and/or cross-zone smoke detection initiates an alarm and de-energizes the emergency fan or AHLI and closes all motor operated dampers to isolate the filter fire from the remainder of the TSC. A filter fire is unlikely to spread into the TSC general area due to the installed pre-action sprinkler system, and the existing separation between the Penthouse and the remainder of the TSC. Consequently, the CO2 fire suppression system is no longer being installed in the relocated TSC contrary to the discussion included in the Ventilation paragraph in Attachment 1, page 12 of 30, of Section 3.1.6, Habitability, of the License Amendment Request (LAR) dated January 13, 2023, (ADAMS Accession No. ML23013A195). The marked-up LAR page indicating the proposed change and the revised LAR replacement page incorporating the proposed change are provided in Attachments 5 and 6, respectively.

Page 3 of 3

Serial No.23-045 Docket Nos.: 50-338/339 Attachment 5 MARKED-UP LAR PAGE INDICATING DELETION OF THE CO2 FIRE SUPPRESSION SYSTEM Virginia Electric and Power Company (Dominion Energy Virginia)

North Anna Power Station Units 1 and 2

Serial No.22-036 Docket Nos.: 50-338/339 Attachment 1 Page 12 of 30 Ventilation The ventilation system for the proposed TSC is designed to meet the requirements of NUREG-0696 (Reference 1} and NUREG-0737, Supplement 1 (Reference 2). Upon facility activation, the ventilation system will be manually placed in emergency operating mode via a hand switch. When placed in emergency operating mode, bubble tight motor operated dampers will align makeup air through a filtration system and deenergize exhaust fan circuits. The filter bank consists of a HEPA filter in series with a high efficiency gas absorption (HEGA) filter with a nominal flow rate of 1000 cfm. The HEPA filter removes particulate radioactive air contaminants, and the HEGA removes remaining pollutants such as iodine compounds. The HEGA filter temperature is monitored by a heat detector. If a flame is detected, the CO.a SuppFession system floods COa into the duet mounted filter housing to e~inguish the flame. The humidity of the makeup air stream is controlled via a sensor and electric duct heater. During emergency operation, the exhaust fans will be de-energized and isolated via dampers enabling the building's static pressure controller to modulate the filter fan speed to maintain the conditioned space at 0.125 inches water gauge (WG) relative to the outside air pressure to prevent infiltration of outside air. The ventilation system design has been suitably sized to provide heating and cooling that is capable of maintaining facility temperature at approximately 75 °F dry bulb+/- 3 °F during the summer and 72 °F dry bulb +/- 3 °F during the winter. The ventilation system is provided with an alarm function that will alert TSC staff of a component failure in the Emergency HVAC system. A LOCA dose calculation was completed to determine the ability of the proposed TSC shielding and ventilation design to meet the specified occupancy dose requirements. Results of this calculation are described below.

Radiological Monitoring The proposed TSC will be provided with radiation monitoring to provide continuous indication of the dose rate and airborne radioactivity in the TSC during an emergency, as well as alerting personnel of adverse conditions as required per NUREG-0696 (Reference 1). The RMS consists of a Mirian radiation monitor to detect airborne radioactivity, and two Mirion DRM-2 general area radiation monitors. The Mirian radiation monitor will include a particulate, an iodine, and a noble gas detector and will be able to distinguish the presence or absence of radioiodines at concentrations as low as 10-7 µci/cc. The monitor will be located in the Dose Assessment Room and will continuously sample the facility atmosphere from locations throughout the TSC and provide an audible alarm to alert TSC personnel of adverse conditions. The two Mirian DRM-2 general area radiation monitors will be wall mounted at separate locations on the TSC Operation Floor and will provide an audible alarm to alert TSC personnel of adverse conditions.

Serial No.23-045 Docket Nos.: 50-338/339 Attachment 6 REVISED LAR REPLACEMENT PAGE INDICATING DELETION OF THE CO2 FIRE SUPPRESSION SYSTEM Virginia Electric and Power Company (Dominion Energy Virginia)

North Anna Power Station Units 1 and 2

Serial No.22-036 Docket Nos.: 50-338/339 Attachment 1 Page 12 of 30 Ventilation The ventilation system for the proposed TSC is designed to meet the requirements of NUREG-0696 (Reference 1) and NUREG-0737, Supplement 1 (Reference 2). Upon facility activation, the ventilation system will be manually placed in emergency operating mode via a hand switch. When placed in emergency operating mode, bubble tight motor operated dampers will align makeup air through a filtration system and deenergize exhaust fan circuits. The filter bank consists of a HEPA filter in series with a high efficiency gas absorption (HEGA) filter with a nominal flow rate of 1000 cfrn. The HEPA filter removes particulate radioactive air contaminants, and the HEGA removes remaining pollutants such as iodine compounds. The HEGA filter temperature is monitored by a heat detector. The humidity of the makeup air stream is controlled via a sensor and electric duct heater. During emergency operation, the exhaust fans will be de-energized and isolated via dampers enabling the building's static pressure controller to modulate the filter fan speed to maintain the conditioned space at 0.125 inches water gauge (WG) relative to the outside air pressure to prevent infiltration of outside air. The ventilation system design has been suitably sized to provide heating and cooling that is capable of maintaining facility temperature at approximately 75 °F dry bulb +/- 3 °F during the summer and 72 °F dry bulb +/- 3 °F during the winter. The ventilation system is provided with an alarm function that will alert TSC staff of a component failure in the Emergency HVAC system. A LOCA dose calculation was completed to determine the ability of the proposed TSC shielding and ventilation design to meet the specified occupancy dose requirements. Results of this calculation are described below.

Radiological Monitoring The proposed TSC will be provided with radiation monitoring to provide continuous indication of the dose rate and airborne radioactivity in the TSC during an emergency, as well as alerting personnel of adverse conditions as required per NU REG-0696 (Reference 1}. The RMS consists of a Mirian radiation monitor to detect airborne radioactivity, and two Mirion DRM-2 general area radiation monitors. The Mirion radiation monitor will include a particulate, an iodine, and a noble gas detector and will be able to distinguish the presence or absence of radioiodines at concentrations as low as 1o-7 µci/cc. The monitor will be located in the Dose Assessment Room and will continuously sample the facility atmosphere from locations throughout the TSC and provide an audible alarm to alert TSC personnel of adverse conditions. The mo Mirian DRM-2 general area radiation monitors will be wall mounted at separate locations on the TSC Operation Floor and will provide an audible alarm to alert TSC personnel of adverse conditions.

Serial ~o.22-045 Docket Nos.: 50-338/339 Enclosure CD-ROM - LOCA DOSE ANALYSIS AND X/Q INPUT AND OUTPUT FILES Virginia Electric and Power Company (Dominion Energy Virginia)

North Anna Power Station Units 1 and 2

v t e Letter Sequence Request
EPID:L-2023-LLA-0006, Proposed Emergency Plan Revision, Relocation of the Technical Support Center (Open)
Initiation Request Acceptance Administration Questions Answers Results Approval, Approval Other: ML23223A040
MONTHYEAR2023-12-07 [Table View]

ML23192A215

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