ML13038A011
| ML13038A011 | |
| Person / Time | |
|---|---|
| Site: | Watts Bar  (NPF-090) |
| Issue date: | 02/04/2013 |
| From: | James Shea Tennessee Valley Authority |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| Download: ML13038A011 (5) | |
Text
Tennessee Valley Authority, 1101 Market Street, Chattanooga, Tennessee 37402 February 4, 2013 10 CFR 50.4 10 CFR 50.90 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, D.C. 20555-0001 Watts Bar Nuclear Plant, Unit 1 Facility Operating License No. NPF-90 Docket No. 50-390
Subject:
Response to NRC Request for Additional Information Regarding the Application to Allow Selective Implementation of Alternate Source Term to Analyze the Dose Consequences Associated With Fuel-Handling Accidents (TAC No. ME8877)
Reference:
- 1. Letter from TVA to NRC, "Watts Bar Nuclear Plant Unit 1 - Application to Allow Selective Implementation of Alternate Source Term to Analyze the Dose Consequences Associated with Fuel Handling Accidents (WBN-TS-1 1-19)," dated June 13, 2012
- 2. Letter from NRC to TVA, "Watts Bar Nuclear Station, Unit 1 - Request For Additional Information Related to License Amendment Request to Allow Selective Implementation of Alternate Source Term to Analyze The Dose Consequences Associated With Fuel-Handling Accidents (TAC No. ME8877)" dated December 20, 2012 By letter dated June 13, 2012 (Reference 1), the Tennessee Valley Authority (TVA) submitted a request for an amendment to the Facility Operating License No. NPF-90 for the Watts Bar Nuclear Plant, Unit 1. The proposed amendment request would allow selective implementation of the alternate source term methodology to analyze the dose consequences associated with fuel handling accidents.
By letter dated December 20, 2012 (Reference 2), the Nuclear Regulatory Commission (NRC) forwarded a request for additional information (RAI) regarding the subject LAR allowing selective implementation of alternate source term to analyze the dose consequences associated with fuel handling accidents. As agreed, the response to the RAI is due 45 days from its date of issuance, or February 3, 2013. Since February 3, 2013 is a Sunday, the response is due the next working day, February 4, 2013.
Prin~ted on~
recy(ýIed papert i
U.S. Nuclear Regulatory Commission Page 2 February 4, 2013 The enclosure to this letter provides TVA's responses to the questions forwarded to TVA in the RAI (Reference 2). TVA's responses to these RAIs does not require any changes to the previous submittal regarding the proposed license amendment to allow selective implementation of the alternate source term methodology to analyze the dose consequences associated with fuel handling accidents.
Consistent with the standards set forth in 10 CFR 50.92(c), TVA has determined that TVA responses as provided in this letter does not affect the no significant hazards considerations associated with the proposed license amendment previously provided in Reference 1. TVA has further determined that the proposed amendment still qualifies for a categorical exclusion from environmental review pursuant to the provisions of 10 CFR 51.22(c)(9). Additionally, in accordance with 10 CFR 50.91 (b)(1), TVA is sending a copy of this letter, the enclosures, and the attachments to the Tennessee Department of Environment and Conservation. There are no regulatory commitments included in this submittal. If you have any questions, please contact Terry Cribbe at (423) 751-3850.
I declare under penalty of perjury that the foregoing is true and correct. Executed on the 4th day of February 2013.
Respectf
`.,Shea 4
Vi
- President, Nuclear Licensing
Enclosure:
Response to NRC Request for Additional Information (RAI) cc (Enclosures):
NRC Regional Administrator - Region II NRC Senior Resident Inspector - Watts Bar Nuclear Plant Director, Division of Radiological Health, Tennessee State Department of Environment and Conservation
ENCLOSURE TENNESSEE VALLEY AUTHORITY WATTS BAR NUCLEAR PLANT UNIT 1 RESPONSE TO NRC REQUEST FOR ADDITIONAL INFORMATION (RAI)
Subject:
Watts Bar Nuclear Plant Unit I - Application to Allow Selective Implementation of Alternate Source Term to Analyze-the Dose Consequences Associated with Fuel Handling Accidents (WBN-TS-11-19)
RAI QUESTION 1 Page E1-6 of Enclosure 1 to the June 13, 2012, submittal discusses a fuel-handling accident scenario that assumes that the containment is open. Please 1) confirm that, in this case when the containment is classified as "open," the only effluent release location to the environment is through the Shield Building vent or Auxiliary Building vent, or 2) if this is not the case, describe the other pathways and justify that the limiting case has been identified.
TVA Response - Question 1 The Shield Building vent and Auxiliary Building vent are the only release points for the Fuel Handling Accidents (FHA). When the containment is "open" it opens into the Auxiliary Building and not to the environment. Therefore any radioactivity in the containment can migrate into the Auxiliary Building or stay within the Reactor Building. During normal operation the Auxiliary Building Ventilation system would be in service and exhausts through the Auxiliary Building vent. The Reactor Building Purge Ventilation system could also be in operation during refueling.
This system exhausts through the Shield Building vent. During emergency conditions the Auxiliary Building Gas Treatment System (ABGTS) could be placed in service. The ABGTS takes suction from the fuel handling area and other areas within the Auxiliary Building and exhausts through the Shield Building vent as well. Therefore during normal and emergency conditions, any releases would either go through the Auxiliary Building vent or the Shield Building vent.
RAI QUESTION 2 Table 5, page E1 -20, provides some of the inputs for calculation of one of the control room atmospheric dispersion factors (x/Q values) using the ARCON96 computer code, but does not include, all of the inputs for the unspecified release location. Table 5 lists two control room x/Q values, one for the Auxiliary Building vent and one for the Shield Building vent. Enclosure 3 of the June 13, 2012, letter is a compact disk that provides a file entitled ARCON96 Output File.
This file includes computer input and output information for approximately 16 different cases.
- a. Please identify and discuss the computer runs in the ARCON96 Output File that are pertinent to the June 13, 2012, LAR and pinpoint the cases used to identify the bounding doses to the control room operators.
- b. Do the generated x/Q values model the bounding doses considering those due to loss of offsite power or other single failures?
Page E-1
- c. Which X/Q values were used to model unfiltered inleakage into the control room and why is the use of these x/Q values appropriate?
TVA Response - Question 2.a Cases 1-4 determines the x/Q from the combinations of the Shield Building vents of Unit 1 and Unit 2 and the normal and emergency intake locations of the Main Control Room (MCR). Cases 13-14 determine the x/Q from the combinations of the Auxiliary Building vent to the normal and emergency MCR intake locations. Case 2 was the bounding case for the Shield Building vent and Case 14 was the bounding case for the Auxiliary Building vent. The normal intake is the one closest to Unit 1 and is referred to as the west intake. The emergency intake is closest to Unit 2 and is referred to as the east intake.
Case #
Release Point Intake 1
Ul Shield Building East/Emergency 2
Ul Shield Building West/Normal 3
U2 Shield Building East/Emergency 4
U2 Shield Building West/Normal 13 Aux. Building West/Normal 14 Aux. Building East/Emergency TVA Response - Question 2.b The analysis released the source term directly to the environment without any filtration or holdup. Therefore, there are no active components to assume a single failure. The only major pathways to the environment from the fuel handling areas would be through the Shield Building vent or the Auxiliary Building vent with or without power. Therefore the x/Q values used would be bounding with respect to the dose consequences.
TVA Response - Question 2.c The Control Room Envelope (CRE) unfiltered inleakage x/Qs values are assumed to be the same as the Control Room intake x/Q values. As identified in Table 5 of the TVA License Amendment Request (LAR) submitted on June 13, 2012, the onsite (i.e., CRE) x/Qs were changed to 2.56E-3 sec/m3 for releases from the Auxiliary Building vent and 1.09E-3 sec/m3 for releases from the Shield Building vent.
The x/Q values established by ARCON96 are the worst case of a set of x/Q values. Each x/Q set is based on the intake location. The Control Room intake locations are on opposite sides of the buildings. As such, using the worst case x/Q value based on the intake is conservative relative to the potential locations for unfiltered inleakage into the building. This includes consideration of the door leading from the Main Control Room Habitability Zone to the Turbine Building (for egress/ingress) listed in WBN, Unit 1 Updated Final Safety Analysis Report Table 6.4-2, Air Leakage (Infiltration) Paths in the Watts Bar MCRHS Area Control Room.
Page E-2
The assumption that the CRE unfiltered inleakage x/Q values are the same as the Control Room intake x/Q values was previously reviewed and approved by the NRC as part of License Amendment No. 59 to Facility Operating License No. NPF-90 issued on January 6, 2006.
On October 13, 2005, the NRC issued the following Request for Additional Information (RAI):
"What are the control room atmospheric dispersion factors (x/Q values) used in the dose assessment for postulated releases from the openings in the shield building dome to 1) the control room air intakes and 2) as a result of unfiltered inleakage..
TVA responded to the RAI on November 8, 2005, by stating that the CRE unfiltered inleakage x/Q values are assumed to be the same as the Control Room intake x/Q values. Subsequently, the NRC issued License Amendment No. 59 to Facility Operating License No. NPF-90. The NRC's supporting Safety Evaluation Report states:
"The calculation incorporates new atmospheric dispersion coefficients (x/Q) values as determined by ARCON96. These codes are described in TVA's letter dated May 21, 2002 (ML021440139), and have previously been used by TVA to support other TVA license amendment requests approved by the staff, such as the Tritium Production Core associated with Watts Bar License Amendment No. 40 dated September 23, 2002 (ML022540925)."
"Based on the review described above, the NRC staff has concluded that the control room, EAB and LPZ x/Q values as presented in Table 1 are acceptable for use in the design basis accident assessments performed in support of this license amendment request."
NRC RAI #RAI QUESTION 3 Watts Bar Final Safety Analysis Report Figure 1.2-1 was annotated and previously docketed as 2 (ADAMS Accession Number ML102290279) to a TVA letter dated July, 31, 2010 (ADAMS Accession Number ML102290258), in support of a licensing action related to Watts Bar, Unit 2. Please confirm that information on this figure supports the current LAR for Watts Bar, Unit 1, or provide a similar annotated figure for the current LAR which highlights the release and receptor locations on a facility layout diagram drawn to scale.
TVA Response - Question 3 Figure 1.2-1 as given in the noted Unit 2 document is also applicable and was used for the current LAR for Unit 1. The normal intake is the one closest to Unit 1 and is referred to as the west intake. The emergency intake is closest to Unit 2 and is referred to as the east intake.
Page E-3