ML20217G875
| ML20217G875 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 07/31/1997 |
| From: | Langenbach J GENERAL PUBLIC UTILITIES CORP. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| RTR-REGGD-01.099, RTR-REGGD-1.099 6710-97-2324, GL-92-01, GL-92-1, TAC-M92741, NUDOCS 9708080090 | |
| Download: ML20217G875 (3) | |
Text
. _ _..
,,c*:
.e
~
j GPU Nuclear. Inc.
(
Route 441 south NUCL' EAR Middletown, PA 17057-0430 Tef 717-944 7621 July 31,1997 6710-97-2324 U.S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, DC 20555 l
Gentlemen:
Subject:
Three Mile Island Nuclear Station Unit 1 (TMI-1)
Operating License No. DPR-50 Docket No. 50-289 Pressure-Temperature (P-T) Limit Curves and Low Temperature Overpressurization (LTOP) Limits
Reference:
NRC letter dated December 23,1996 from Mr. J. A. Norris to Mr. James Knubel, subj. Close-out for GPU Response to 92-01, Revision 1, Supplement 1 for Three Mile Island Unit 1, (TAC No. M92741)
The reference letter requested t'nat an assessment of the application of the ratio procedure, as
- described in Position 2. I of Regulatory Guide 1.99, Revision 2 (May 1988), to the TMI-1 P-T limit curves and LTOP limits be provided. The requested assessment should include an evaluation relative to the margins specified in applicable codes and standards (i.e.: Appendix G to Section III of the ASME Code).
During a meeting with the NRR Staff, on March 6,1997, GPU Nuclear (GPUN) presented the impact of applying the ratio procedure to the B&WOG integrated surveillance data for the limiting TMI-l weldment made of single wire Linde80 (weld wire heat number 299L44) on the chemistry factor which is used in the calculation of the reference temperature (RTNur) as a ge019 function of the applied fluence.
As stated in the meeting, GPUN considers the ratio procedure to be inappropriate for use with surveillance capsule data from the multiple sources, wherein the variation in the chemistry composition of the surveillance capsules bounds the chemical composition of the vessel 9708000090 970731 l
lhllll l
PDR ADOCK 05^O0289 P
- a c
v
weldment, and that application of the ratio procedure does nothing more than increase the scatter in ratio adjusted data while artificially inflating the chem:stry factor. The surveillance capsule which had the greatest impact with the application of the ratio procedure was the Surry Unit No. I capsules which had a copper content below the lower 95% confidence limit for the vessel copper content nomial distribution. GPUN stated that the reported copper content may be in error (due to only a single analysis result) as compared to the larger population of chemical analysis from three different vessel weldments, and all of the surveillance capsule data for this weld wire heat should be treated as a representative population for the vessel weldment made of this same weld wire heat.
GPUN has, since that meeting, contracted Framatome Technologies to re-analyze the chemical composition of the Surry Unit No.1 Charpy specimens, using both the ICP and the Atomic Absorption (per ASTM E350) methods. Preliminary results indicate that the previously reported chemical composition of these capsules is valid.
Since the Surry surveillance capsules have copper contents which are significantly below the balance of the surveillance capsules which are made of the same weld wire heat and were irradiated at temperatures of 17 to 21 degrees lower than the balance, GPUN calculated the chemistry factor several ways. First, a chemistry factor of 217 was determined on the basis of all of the data without applying the ratio pmcedure, with application of the ratio procedure the chemist:y factor increased to 231.8. Secondly, excluding the Suny data (which had the lowest Cu & Ni chemical composition), a chemistry factor of 218 was calculated without the ratio procedure, and a value of 220 was calculated when the ratio procedure was applied. Based on the chemistry factor (CF) table contained in the Regulatory Guide 1.99, Rev.2, and the best estimate Cu & Ni content of the vessel weldment, the CF should be 225 which compared to the 217 to 220 values calculated from the data. This indicates that there is something anomalous in regard to the Suny surveillance capsule embrittlement data which is not properly accounted for in position 2.1 of the Regulatory Guide 1.99, Rev. 2.
During the reference meeting with the Staff, GPUN also pointed out that there are presently Code changes in progress such as a more appropriate definition of the assumed flaw orientation, and the application of direct fracture toughness measurements of the material.
Both of these changes, when approved and applied, would demonstrate a substantial margin of safety in the present operating P-T curves for Thil-!.
If a CF of 231.8 were used to assess the trend in RTsar for the Thil-1 P/T limits and the Code change for the assumed flaw orientation were approsed, then the Thil-1 limiting weld would change to a longitudinal weld made of the same weld wire, but with lower fluence, and the RTmyr of 186 (had been based on a CF of 221.25) which forms the basis of the present P-T curves would be reached in htarch or April 1999.
If the Code change regarding the use of direct fracture toughness data were approved and applied, then the RTxor of the limiting Thil-1 vessel weld would not reach its current P-T limit basis of 186 until a point in time which is beyond its present operating license. GPUN, through the B&WOG, has already submitted for NRC approval of a topical report (BAW-2241) which contains ThfI-l specific weld material data to justify an upper bound initial
basis of 186 until a point in time which is beyond its present operating license. GPUN, through the B&WOG, has already submitted for NRC approval of a topical report (BAW 2241) which contains TMI-l specific weld material data to justify an upper bound initial RTmr of-27 F.
An exemption using the fracture toughness methodology for a different weld wire heat has already been granted by the NRC.
Other ongoing activities regarding irradiation embrittlement of reactor vessel materials include the ASThi E 900 activity to reassess the correlations and methodology contained in the Regulatory Guide 1l'9, Rev.2.
With the ongoing industry activities which are nearing approval, which may lead to regulatory change, and the completion of an enhanced ISI examination of the Thil-l vessel which indicated that the vessel did not contain any flaws, GPUN believes that the present Thil-l P-T and LTOP limits provide adequate assurance for the prevention of non-ductile failure of the vessel. When we revise the present P-T and LTOP limits as required by the current Thil Technical Specifications (TS) for operation beyond 15.2 effective full power years (EFPY), we l
will include evaluation and incorporation of relevant infonnation at the time of submittal. We plan to submit the revised TS in the third quaner of 1998.
t Sincerely, i
i 14
' ames W. Langenba Vice President and Director, TM1 YN/JSS cc: Administrator, USNRC Region 1 TMI Sr. Project Manager, USNRC NRR TMI Resident inspector, USNRC Region i