ML043140108
| ML043140108 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 11/08/2004 |
| From: | Abney T Tennessee Valley Authority |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| GL-98-005 | |
| Download: ML043140108 (6) | |
Text
November 8, 2004 10 CFR 50.55a(a)(3)(i)
U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Mail Stop: OWFN P1-35 Washington, D.C. 20555-001 Gentlemen:
In the Matter of ) Docket No. 50-259 Tennessee Valley Authority )
BROWNS FERRY NUCLEAR PLANT (BFN) - UNIT 1 - AMERICAN SOCIETY OF MECHANICAL ENGINEERS (ASME) SECTION XI AND AUGMENTED INSPECTIONS - REVISION TO REQUEST FOR RELIEF, 1-ISI-19, REGARDING REACTOR PRESSURE VESSEL (RPV) CIRCUMFERENTIAL SHELL WELD EXAMINATIONS In recent discussions, the NRC Staff requested that TVA revise BFN Unit 1 Relief Request 1-ISI-19, submitted by letter dated May 12, 2004 (Reference 1). Relief Request 1-ISI-19 requests relief, based on the guidance contained in NRC Generic Letter 98-05 (Reference 2), from the inservice inspection requirements of 10 CFR 50.55a(g) for the volumetric examination of the BFN Unit 1 reactor vessel circumferential shell welds.
Relief Request 1-ISI-19 was based in part on an end-of-license reactor vessel circumferential beltline weld (Weld C-1-2) nil-ductility transition temperature (RTNDT) calculated at 1/4T (one quarter thickness) of the reactor vessel wall. Per discussions with the NRC Staff, the NRC requires the end-of-license reactor vessel circumferential beltline weld inner surface RTNDT (RTNDT calculated based on the reactor vessel inner surface fluence) to complete its acceptance review.
Accordingly, TVA has recalculated Weld C-1-2 RTNDT at the reactor vessel inner surface. The information requested and its supporting assumptions are provided below.
The Weld C-1-2 RTNDT reported in Reference 1 and in TVAs response to an NRC Staff Request for Additional Information
U.S. Nuclear Regulatory Commission Page 2 November 8, 2004 (Reference 3), was based on assumed BFN Unit 1 operation of 32 Effective Full Power Years (EFPY) at Extended Power Uprate (EPU) conditions. As discussed in Reference 1, these assumptions were very conservative because BFN Unit 1 is expected to accumulate less than 14 EFPY of reactor operation by the end of its current license due to its extended shutdown, with less than 8 of the 14 EFPY at EPU conditions.
Calculation of Weld C-1-2 RTNDT at the inner vessel surface assuming a fluence representing 32 EFPY of operation at EPU conditions would yield an RTNDT that would exceed the NRCs criteria given in Table 2.6-4 of Reference 4.
Therefore, TVA has calculated the Weld C-1-2 inner surface RTNDT assuming 16 EFPY of operation at EPU conditions. This assumption is still very conservative, and demonstrates that the associated NRC acceptance criteria for granting the requested relief are met. The results of this calculation, along with key inputs are provided below.
BFN Unit 1 Weld C-1-2 Mean ID RTNDT at 16 EFPY RPV manufacturer B&W Existing vessel exposure 6.15 EFPY Current license expiration December 20, 2013 Assumed end-of-license exposure1 16 EFPY RPV ID peak flux (>1.0 Mev) 1.40E9 n/cm2-sec RPV ID peak surface fluence 7.07E17 n/cm2 Ratio peak/weld C-1-2 location 0.81 Weld C-1-2 peak surface fluence2 5.78E17 n/cm2 Cu (Wt %)
0.27%
Ni (Wt %)
0.60%
Chemistry Factor 184 Weld C-1-2 ID surface RTNDT at 16 EFPY 58.2°F Weld C-1-2 initial RTNDT 20°F Weld C-1-2 mean ID surface RTNDT at 16 EFPY 78.2°F
- 1. This value is conservative, as less than 14 EFPY of operation is expected by the end of the current operating license.
- 2. Fluence conservatively increased 1%, from 5.73E17 n/cm2 to 5.78E17 n/cm2 to account for planned future operation in an expanded operating domain (MELLLA+ operation).
U.S. Nuclear Regulatory Commission Page 3 November 8, 2004 As shown in the table above, TVAs revised analysis results in a conservatively calculated Reactor Vessel Beltline Circumferential Weld C-1-2 inner surface end-of-license mean RTNDT of 78.2°F. This value is well below the end-of-license mean RTNDT used in the NRCs conditional failure probability assessment for the bounding Babcox & Wilcox reactor vessel of 99.8°F. Accordingly, BFN Unit 1 meets the NRCs criteria for granting the requested relief.
The reactor vessel beltline circumferential weld C-1-2 fluence and RTNDT information provided in this letter supersedes that provided previously in Reference 1 and 3. This information does not alter the information provided in Reference 3 regarding the flux evaluation methodology utilized.
There are no new commitments contained in this letter. If you have any questions, please telephone me at (256) 729-2636.
Sincerely, Original signed by:
T. E. Abney Manager of Licensing and Industry Affairs
References:
- 1. TVA letter, T. E. Abney to NRC, Browns Ferry Nuclear Plant (BFN) - Unit 1 - American Society of Mechanical Engineers (ASME)Section XI and Augmented Inspections -
Request for Relief, 1-ISI-19, Regarding Reactor Pressure Vessel (RPV) Circumferential Shell Welds, dated May 12, 2004.
- 2. NRC Generic Letter 98-05, Boiling Water Reactor Licensees Use of the BWRVIP-05 Report to Request Relief From Augmented Examination Requirements on Reactor Pressure Vessel Circumferential Shell Welds, dated November 10, 1998.
- 3. TVA letter, T. E. Abney to NRC, Browns Ferry Nuclear Plant (BFN) - Unit 1 - American Society of Mechanical Engineers (ASME)Section XI and Augmented Inspections -
U.S. Nuclear Regulatory Commission Page 4 November 8, 2004 Response to Request for Additional Information - Request Shell Welds, dated August 13, 2004.
- 4. NRC Letter, G. C. Lainas (NRC) to C. Terry (BWRVIP), Final Safety Evaluation of the BWR Vessel and Internals Project BWRVIP-05 Report (TAC No. M93925), dated July 28, 1998.
U.S. Nuclear Regulatory Commission Page 5 November 8, 2004 cc: U.S. Nuclear Regulatory Commission Region II Sam Nunn Atlanta Federal Center 61 Forsyth Street, SW, Suite 23T85 Atlanta, Georgia 30303-3415 Mr. Stephen J. Cahill, Branch Chief U.S. Nuclear Regulatory Commission Region II Sam Nunn Atlanta Federal Center 61 Forsyth Street, SW, Suite 23T85 Atlanta, Georgia 30303-8931 Margaret Chernoff, Project Manager U.S. Nuclear Regulatory Commission (MS 08G9)
One White Flint, North 11555 Rockville Pike Rockville, Maryland 20852-2739 Kahtan N. Jabbour, Project Manager U.S. Nuclear Regulatory Commission (MS 08G9)
One White Flint, North 11555 Rockville Pike Rockville, Maryland 20852-2739 NRC Senior Resident Inspector Browns Ferry Nuclear Plant 10833 Shaw Road Athens, AL 35611-6970
U.S. Nuclear Regulatory Commission Page 6 November 8, 2004 MJB:BAB cc: A. S. Bhatnagar, LP 6A-C J. C. Fornicola, LP 6A-C D. F. Helms, BR 4T-C R. F. Marks, PAB 1C-BFN R. G. Jones, NAB 1A-BFN K. L. Krueger, POB 2C-BFN J. R. Rupert, NAB 1A-BFN K. W. Singer, LP 6A-C M. D. Skaggs, PAB 1E-BFN E. J. Vigluicci, ET 11A-K NSRB Support, LP 5M-C EDMS WT CA - K S:lic/submit/subs/BFN U1 Circ Weld RR Revision.doc