ML20077F351
| ML20077F351 | |
| Person / Time | |
|---|---|
| Site: | Hatch  |
| Issue date: | 07/12/1983 |
| From: | Gucwa L GEORGIA POWER CO. |
| To: | Stolz J Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML20077F352 | List: |
| References | |
| NED-83-388, TAC-51407, NUDOCS 8308010343 | |
| Download: ML20077F351 (2) | |
Text
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Georg a Poner Company 333 P,edmont Aven e Atlanta GNrg a 5;308
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s Te*pbore 424 526 6526 Va i.ng Add.ess Post Cff a Box 4545 At:anta, Geeg a 30302 M
Georgia Power L T. Gucwa ys ; un scr:c s,sem Che' Nuclear Engrw Power Gareraton Departrnert NED-83-388 July 12, 1983 9 SH Director of Nuclear Reactor Regulation Attenticn:
Mr. John F. Stolz, Chief Operating Reactors Branch No. 4 Division of Licensing U.S. Nuclear Regulatory Commission Washington, D.C.
20555 NRC DOCKET 50-366 OPERATING LICENSE NPF-5 EDWIN I. HATCH NUCLEAR PL44T UNIT 2 RECIRCULATION SYSTEM PIPE CRACK STUDY AND END CAP DESTRUCTIVE EXAMINATION Gentlemen:
Enclosed for your review is the Structural Integrity Associates prepared report which discusses the investigation into the cause of pipe cracking at Plant Hatch Unit 2 and comparison with Plant Hatch Unit 1.
Three copies of the report have been enclosed for your convenience.
The results of the investigation were summarized in our May 26, 1983, submittal on the repairs and analysis of flawed recirculation system and residual heat removal system piping and were discussed in a meeting with tEC staff on June 1, 1983.
A number of areas were investigated as potential causes of the accelerated intergranular stress corrosion cracking (IGSCC) behavior at Plant Hatch Unit 2 compared to Plant Hatch Unit 1.
Areas investigated included fabrication history, applied and residual stresses, and operational history of the two units (both time / stress cycles and water chemistry).
A detailed review of the current inspection results at both units was also conducted.
Based on the investigation, the only substantive difference found between the two units was an unusual weld prep /counterbore configuration in the Plant Hatch lhit 2 shop welds which resulted in a stress concentration notch or fillet within the IC5CC susceptible weld heat affected zones.
Analyses were performed which indicate that the stress concentrating effect of this notch could accelerate the initiation of IGSCC in the counterbore region sufficiently to explain the observed cracking.
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PDR ADOCK 05000366 0b5 8308010343 830712 I
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Georgia Power d Director of Nuclear Reactor Regulation Attention:
Mr. John F. Stolz, Chief Operating Reactors Branch No. 4 July 12, 1983 Page Two l
During the repairs at Plant Hatch Unit 2,
one of the affected Recirculation System manifold end caps (weld 2831-1RC-22BM-4) was voluntarily replaced.
A sample from the end cap was sent to Battelle-Columbus Laboratories for analysis.
Georgia Power Company (GPC) has been notified of the preliminary results of the Battelle analysis.
IGSCC was confirmed in the end cap sample.
Transgranular cracking was observed in one indication found in the sample and is considered to be an anomaly.
This occurrence of transgranular cracking is being investigated further.
Analysis revealed there was no appreciable amount of chlorides observed in the cracking.
In addition, crack depth was measured during destructive testing and observed to be consistent with the results of ultrasonic testing performed during inservice inspection.
Maximum through-wall depth of weld 2831-lRC-22BM-4 was estimated to be 37% by ultrasonic sizing.
Wall thickness of the end cap is approximately one inch. - Destructive testing at Battelle indicated through-wall depth to be 0.28 inch (approx. 28% of wall thickness) thereby proving conservatism in the through-wall sizing performed.
A formal report from Battelle is not available at this time as work is incomplete.
Upon completion of the Battelle analysis and review by GPC, a formal report will be submitted for your review.
A sample from the aforementioned end cap was. provided to WC-NRR for analysis by Argonne National Laboratory in a cooperative effort to resolve the IGSCC phenomenon.
GPC requests a copy of the report on the results of that analysis in order to expand our understanding of IGSCC.
A copy of this submittal is being provided concurrently to EC Region II for their review.
Should you have any questions in this regard, please t.ontact this office.
Sincerely yours,
/[ LL _ s L. T. Gucwa JAE/b1m Enclosures (3) xc:
J. T. Beckham, Jr.
H. C. Nix, Jr.
Senior Resident Inspector J. P. O'Reilly (NRC Region'II) w
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