ML11180A032
| ML11180A032 | |
| Person / Time | |
|---|---|
| Site: | Watts Bar  |
| Issue date: | 06/27/2011 |
| From: | Stinson D Tennessee Valley Authority |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| Download: ML11180A032 (3) | |
Text
Tennessee Valley Authority, Post Office Box 2000, Spring City, Tennessee 37381-2000 June 27, 2011 10 CFR 50.4 10 CFR 2.390(b)(4)
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 - Response to Request for Additional Information Regarding April 27, 2011 NRC Audit
References:
- 1. NRC letter to TVA dated April 27, 2011, "Watts Bar Nuclear Plant, Unit 2 -
Audit Report of Westinghouse Documents Relating to Final Safety Analysis Report Accident Analyses (TAC NO. ME4620)"
Unit 2 - Final Safety Analysis Report (FSAR) - Response to Request for Additional Information" During preparation for an audit the week of June 27, 2011, TVA determined the enclosed information should have been provided in response to Reference 1. Accordingly, the information requested in Reference 1, Section A. 1 actions 4 and 5 is provided herein. Also, it should be noted that Reference 2, Attachment 6 provided the information requested by Reference 1, Section A. 1, action 1.
If you have any questions, please contact Bill Crouch at (423) 365-2004.
I declare under penalty of perjury that the foregoing is true and correct. Executed on the 27th day of June 2011.
Respectfully, David Stinson Watts Bar Unit 2 Vice President DD3D
U.S. Nuclear Regulatory Commission Page 2 June 27, 2011
Enclosure:
- 1. Supplemental Information for the Watts Bar Unit 2 (WBT) Hot Zero Power (HZP) Steam Line Break (SLB) Analysis for RAI Response cc (Enclosure):
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
Enclosure Watts Bar Nuclear Plant (WBN) Unit 2 - Response to Request for Additional Information (RAI) Regarding April 27, 2011 NRC Audit Supplemental Information for the Watts Bar Unit 2 (WBT) Hot Zero Power (HZP) Steam Line Break (SLB) Analysis for RAI Response
Reference:
Westinghouse Letter WBT-D-3109 NRC Question A.4:
Address the staffs question, raised during the audit, regarding fuel rod mechanical design rod internal pressure (i.e., clad liftoff) concerns during the steamline break event down to the accumulator injection set pressure.
TVA Response:
The fuel design limit for rod internal pressure is that:
- 1. The internal pressure of the lead rod in the reactor will be limited to a value below that which could cause (1) the diametral gap to increase due to outward cladding creep during steady-state operations and (2) extensive DNB propagation to occur,
- 2. DNB propagation is limited for Condition II events, and
- 3. The increased fuel pressure does not introduce a significant number of additional DNB events in the safety analysis of Condition III and IV events.
Cycle-specific evaluations are performed using NRC-approved models and methodologies in order to confirm that all of the above criteria are met. These evaluations include analyzing the effects of steamline break events down to the accumulator injection set pressure.
NRC Question A.5:
What, if any, actions would plant operators initiate if the moderator temperature coefficient (MTC) surveillance measurement was within the most-negative allowable MTC, but beyond the cycle specific moderator density coefficients used in the steamline break analysis?
TVA Response:
There are no separate, tiered actions for Technical Specification requirements and cycle-specific values. The required actions are defined by Technical Specifications Limiting Condition for Operation (LCO) 3.1.4. Related information is provided in Reference 5 (WCAP-15088, Rev. 1) of the Core Operating Limits Report (COLR) section of the Watts Bar Unit 2 Technical Specifications (Section 5.9.5).