ML11262A276
| ML11262A276 | |
| Person / Time | |
|---|---|
| Site: | Watts Bar  |
| Issue date: | 09/15/2011 |
| From: | Stinson D Tennessee Valley Authority |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| Download: ML11262A276 (9) | |
Text
Tennessee Valley Authority, Post Office Box 2000, Spring City, Tennessee 37381-2000 September 15, 2011 10 CFR 50.34(b) 10 CFR 100 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C. 20555-0001 Watts Bar Nuclear Plant, Unit 2 NRC Docket No. 50-391
Subject:
Watts Bar Nuclear Plant (WBN) Unit 2 - Final Safety Analysis Report (FSAR) - Chapter 15.5 Design Basis Dose Analysis
References:
- 1. TVA Letter to NRC dated June 27, 2011, "Watts Bar Nuclear Plant (WBN) Unit 2 - Final Safety Analysis Report (FSAR) - Response to Request for Additional Information (RAI) Regarding Accident Dose Analysis Basis"
- 2. TVA Letter to NRC dated August 5, 2011, "Watts Bar Nuclear Plant (WBN) Unit 2 - Final Safety Analysis Report (FSAR) - Chapter 15.5 Design Basis Dose Analysis" This letter provides revised FSAR Design Basis Accident dose analysis results for the Main Steam Line Break (MSLB), Steam Generator Tube Rupture (SGTR), and Loss of AC Power accidents. provides updated FSAR Tables for the MSLB, SGTR, and Loss of AC Power events. These results changed as a result of correcting the release elevation of the Unit 2 South Main Steam Valve Vault. The effect on the results was minimal, with the resulting dose being slightly lower than previously calculated. A discussion of the limiting release/receptor points for the Unit 2 Control Room Dose assessments for all accidents analyzed for dose is also provided. lists the new commitments to include the revised analysis in a future FSAR amendment and to submit a revised Fuel Handling Accident and a complete FSAR Section 15.5 draft incorporating recent changes by September 30, 2011.
o(LL
U.S. Nuclear Regulatory Commission Page 2 September 15, 2011 I declare under penalty of perjury that the foregoing is true and correct. Executed on the 1 5 th day of September, 2011.
Respectfully, David Stinson Watts Bar Unit 2 Vice President
Enclosures:
- 1.
WBN Unit 2 Revised FSAR Section 15.5 Dose Analysis
- 2.
Regulatory Commitments cc (Enclosures):
U. S. Nuclear Regulatory Commission Region II Marquis One Tower 245 Peachtree Center Ave., NE Suite 1200 Atlanta, Georgia 30303-1257 NRC Resident Inspector Unit 2 Watts Bar Nuclear Plant 1260 Nuclear Plant Road Spring City, Tennessee 37381 WBN Unit 2 Revised FSAR Section 15.5 Dose Analysis A telephone call was held with the NRC on August 30, 2011, for a general discussion of the release points from WBN building ventilation exhausts and receptor points at the Main Control Room (MCR) air intakes used in the FSAR Chapter 15 dose analyses for Unit 2. A summary of the discussions follows.
Release points from either the Unit 1 or Unit 2 shield building stack are used for the Loss of Coolant Accident (LOCA) and Fuel Handling Accident (FHA). The South Main Steam Valve Vault is the release point for the MSLB, SGTR, and Loss of AC events. The release point for the Waste Gas Decay Tank Rupture is the normal Auxiliary Building Exhaust. The receptor points for any of these events can be either the east or west MCR intake.
The control room X/Qs were determined using ARCON96. For the LOCA and FHA, the most limiting release/receptor combination is the Unit 1 Shield Building Vent to the west Control Building Intake. The Unit 1 Shield Building Vent is a release point for Unit 2 because for a LOCA or FHA on Unit 2 due to the design of the Emergency Gas Treatment System and Auxiliary Building Gas Treatment System, the release can occur from either the Unit 1 or the Unit 2 Shield Building Stack. Of the various possible combinations, the path described above will result in the highest dose to the operators. The X/Q for the LOCA is 1.09 E-3 for the 0-2 hour time period and 9.44 E-4 for the 2-8 hour time period. Since all releases for the FHA are assumed to occur within 0-2 hours, only the 1.09E-3 X/Q is used for this accident.
For the MSLB, SGTR, and Loss of AC event, the most limiting release/receptor combination is the Unit 2 South Main Steam Valve Vault with the east Control Building Intake. The X/Q for this combination is 2.59 E-3 for the time period of 0-2 hours and 2.12 E-3 for 2-8 hours. The release elevation is 23 meters.
The limiting Waste Gas Decay Tank rupture control room X/Q is 2.56 E-3 for the 0-2 hour time period. This is based on a release from the Auxiliary Building Vent to the east Control Room intake. Since all releases for the Waste Gas Decay Tank rupture are assumed to occur within the 0-2 hour time period, X/Qs for other time periods are not applicable.
The operators are procedurally directed to use the MCR intake that is experiencing the lower dose rate. The analyses take credit for this action for events with a release that exceeds 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />. The analyses assume that the intake that maximizes the dose to the operator is used for the first 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> and then the intake with the lower dose rate is used thereafter. In the case of the limiting LOCA for Unit 2, the west MCR intake is used for the first 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> (X/Qs are 1.09E-03 from 0-2 hours, and 9.44E-04 from 2-8 hours) after which time the east intake would be used. The X/Qs for the path from the Unit 1 shield building vent to the east MCR intake are 1.26 E-4, 9.53 E-5, and 8.07 E-5 for the time periods of 8 to 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, 1 to 4 days, and 4 to 30 days respectively. The dose analyses actually used 1.56 E-4, 1.16 E-4, and 9.59 E-5.
These values are conservative relative to the values that could have been used and will result in a higher calculated Control Room dose.
El-1 WBN Unit 2 Revised FSAR Section 15.5 Dose Analysis The elevation of the release point for the South Main Steam Valve Vault was corrected from 20 to 23 meters. This resulted in slightly lower X/Q values and thus slightly lower Control Room doses. The following draft FSAR tables provide updated results from analyses using the corrected elevation.
Table 15.5-2 Doses From Loss of A/C Power Conservative Analysis (rem) 2 HR EAB 30 Day LPZ Control Room Gamma 7.45 E-04 4.18 E-04 2.10 E-04 Beta 4.48 E-04 2.52 E-04 2.52 E-03 Thyroid - ICRP-30 4.57 E-02 2.57 E-02 2.09 E-02 Realistic Analysis (rem) 2 HR EAB 30 Day LPZ Control Room Gamma Beta Thyroid - ICRP-30 1.80 E-08 1.66 E-05 1.10 E-06 1.01 E-08 9.29 E-06 6.18 E-07 5.05 E-09 1.79 E-04 5.03 E-07 E1-2
Enclosure I WBN Unit 2 Revised FSAR Section 15.5 Dose Analysis Table 15.5-14 Atmospheric Dilution Factors At The Control Building DILUTION FACTOR (sec/m3)
Time Period (hr)
LOCA/FHA1 SGTR/MSLB/Loss of WGDT AC Power 0-2 1.09 E-03 2.59E-03 2.56 E-03 2-8 9.44 E-04 2.12 E-03 N/A 8-24 1.56 E-04*
N/A N/A 24-96 1.16 E-04**
N/A N/A 96-720 9.59 E-05***
N/A N/A GENERAL CONTROL ROOM PARAMETERS Volume Makeup/pressurization flow Recirculation flow Unfiltered intake Filter efficiency Isolation time, T Occupancy factors:
0-24 hr 1-4 days 4-30 days
- 1. All FHA releases are within 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />.
for the FHA.
257,198 cu ft 711 cfm 2889 cfm 51 cfm 95% first pass 70% second pass 0% for noble gases, Tritium 40 seconds 100%
60%
40%
Thus, only the 0-2 hr X/Q is applicable Calculated value for Ul Shield Bldg Vent to East MCR Intake Calculated value for Ul Shield Bldg Vent to East MCR Intake Calculated value for Ul Shield Bldg Vent to East MCR Intake 1.26 E-04 9.53 E-05 8.07 E-05 E1-3
Enclosure I WBN Unit 2 Revised FSAR Section 15.5 Dose Analysis Table 15.5-17 Doses From Main Steam Line Break 1 gpm Primary-2 HR EAB 30 Day LPZ SRP Control SRP to-Secondary Guidance for Room Guidance Leakage 10CFRIOO for (ARCON-96 X/Q)
Limits (rem)
IOCFR100 Limits (rem)
Pre-Accident Initiated Spike Case (14 pCi/gm maximum peak)
Gamma 2.74 E-02 1.11 E-02 25 4.32 E-03 5
Beta 8.80 E-03 4.20 E-03 300 3.96 E-02 30 Thyroid -
2.41 E+00 1.21 E+00 300 7.38 E+00 30 ICRP-30 Accident Initiated Spike Case (0.265 pCi/gm steady state)
Gamma 1.04 E-01 1.25 E-01 2.5 8.00 E-03 5
Beta 2.54 E-02 3.02 E-02 30 6.44 E-02 30 Thyroid -
3.09 E+00 4.78 E+00 30 1.03 E+01 30 ICRP-30 E1-4 WBN Unit 2 Revised FSAR Section 15.5 Dose Analysis Table 15.5-18 Parameters Used In Steam Generator Tube Rupture Analysis Primary Side Activity Secondary Side Activity Iodine Spiking Factor Iodine Partition Factor Technical Specification Limit ANSI/ANS-18.1-1984 (Expected levels, 150 gpd/SG)
Case 1: Accident initiated spike of 500 times equilibrium iodine concentration Case 2: Pre-accident spike of 14 pCi/gm 1-131 dose equivalent 100 Secondary Side Mass Release (Ruptured Steam Generator) 0 -2 hours 2 - 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> Secondary Side Mass Release (Intact Steam Generator) 0 - 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> 2 - 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> Primary Coolant Mass Release (Total) 0 - 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> Primary Coolant Mass Release (Flashed) 0 - 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> Meteorology 103,300 Ibm 32,800 Ibm 492,100 Ibm 900,200 Ibm 191,400 Ibm 10,077.2 Ibm See Table 15A-2 and 15.5-14 E1-5 WBN Unit 2 Revised FSAR Section 15.5 Dose Analysis Table 15.5-19 Doses From Steam Generator Tube Rupture Pre-Accident Initiated Spike Case (14 pCi/gm maximum peak)
(rem) 2 HR EAB 30 Day LPZ Control Room Gamma 3.78 E-01 1.11 E-01 6.22 E-02 Beta 2.26 E-01 6.92 E-02 7.01 E-01 Thyroid - ICRP-30 1.39 E+01 3.79 E+00 1.23 E+01 Accident Initiated Spike Case (0.265 ItCi/gm steady state)
(rem) 2 HR EAB 30 Day LPZ Control Room Gamma 5.46 E-01 1.60 E-01 5.71 E-02 Beta 2.51 E-01 7.73 E-02 6.64 E-01 Thyroid - ICRP-30 7.19 E+00 2.12 E+00 2.01 E+00 E1-6 Regulatory Commitments
- 1.
Provide a letter that includes a complete FSAR Section 15.5 draft incorporating the updated X/Qs; the revised results for the MSLB, SGTR, and Loss of AC Power; and the revised FHA results by September 30, 2011.
- 2.
Submit revised FSAR Section 15.5 in a future amendment of the FSAR.
E2-1