ML20134M592
| ML20134M592 | |
| Person / Time | |
|---|---|
| Site: | Peach Bottom  |
| Issue date: | 11/14/1996 |
| From: | Hunger G PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| GL-88-01, GL-88-1, NUDOCS 9611250172 | |
| Download: ML20134M592 (2) | |
Text
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PECO NUCLEAR nw%c-965 Chesterbrook Boulevard A Unit of PECO Energy Wayne. PA 19087 5691 1
November 14,1996
)
Docket No. 50-277 License No. DPR-44 U. S. Nucieer Regulatory Commission ATTN: Document Control Desk Washington, DC 20555
SUBJECT:
Peach Bottom Atomic Power Station, Unit 2 Discovery of Indication in a Reactor Water Cleanup System I
Dear Sir:
l This letter is in response to a telephone conversation between PECO Energy Company (PECO Energy) and the U. S. Nuclear Regulatory Commission (USNRC) on September 19,1996, regarding the discovery of a crack 4ike indication in the unclassified portion of the Reactor Water s Cleanup (RWCU) System piping during outage examinatiorw (2R11) at Peach Bottom Atomic Power Station (PBAPS), Unit 2. In that conversation, PECO Energy Company committed to supplying information regarding the discovery within 45 days following the completion of 2R11.
The weld was repaired by the overlay method in accordance with Code Case N-504. Therefore, i
no request was necessary for permission to restart in accordance with Generic Latter 88-01 j
("NRC Position on Intergranular Stress Corrosion Cracking (IGSCC) in BWR Austenitic Stainless Steel Piping").
This crack 41ke indication, characteristic of IGSCO, was identified on September 17,1996, in the
{
i pipe-to-elbow heat affected zone of weld (12-14-5) in the RWCU System piping at PBAPS, Unit 2 q
]
during the performance d augmented examinations. The augmented inspections were conducted as described in the PBAPS, Units 2 and 3, " inservice Inspection (ISI) Program 4
Second Ten Year Interval" (Specification M-733), AUG-1 examination program during the 2R11
[
refueling outage
]
The indication is located in the four (4) inch RWCU System retum line, upstream of MO-212-68,
~
in unciassified pipe outboard of the primary containment boundary. The PBAPS, Unit 2 indication was 0.6 inches long around the circumference with a maximum depth of 0.132 inches.
The measured pipe thickness is 0.337 inches. The piping is Code Class B31.1 piping with a design pressure of 1300 lbs. and a standard operating pressure of 550 degrees fahrennelt. This crack was identified by General Electric Nuclear Energy personnel performing ultrasonic testing (UT). These examinations consisted of 60 and 70 degree shear waves.
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, November 14,1996 Page 2 i
? A Non conformance Report (NCR) uns origir.::esd to address this crack indication. The
- =- *' i of the NCR was to repair the weld using a fun structural overlay. This overlay was performed in accordance with Code Case N-504, which has been approved for usage as i
documented in Regulatory Guide 1.147, Revision 11.
The indication was in the heat allected zone of a weld that was not part of the augmented examination sample (2%), but was a reexamination d a weld examined during 2R10. The 2%
sample examination of unclassified RWCU System piping revealed no indications. However, as a result of this discovery, the sample of welds was expanded by doubling the sample (2%)
which corresponds to 2 addhional welds These welds were located in the same horizontal run of piping and were chosen for their high susceptibuky to IGSCC No addhional indications were discovered. in accordance with the guidance provided in your letter dated September 15,1996 (letter from J. W. Shea (USNRC) to G. A. Hunger, Jr. (PECO Energy Company)), the sample of RWCU System welds to be examined will remain at 2% for future examinations.
The addhional examinations were performed in the outboard Main Steam isolation Valve Room.
j Several RWCU System indications have been found in this location at both Units (e.g.,12-1-1D (2R08),12-1-1C (3R08),12-14-5 (2R11)). The pipe at these locations is Type 304 stainless steel.
Operating at service conditions creates the susceptibilky to IGSCC at these locations.
To date,30 of 108 welds have been examined in the PBAPS, Unit 2 RWCU System piping rushnard of the containment lantatlan valves in accordanos with the GL 8801 requirements including this indication, a total of two (2) indications have been identified at PBAPS, Unit 2.
These ir*atinns are lentad in close proximity. The previous indication was repaired with a weld overlay and was approved by the USNRC in a letter dated November 8,1991 (letter from R. J. Clark (USNRC) to G. J. Beck (PECO Energy)). Based on the minimal number of identified indications, continued performance of the 2% sample is considered to be a prudent course of action.
If you have any question, please contact us.
Very truly yours, j
N.
G. A. Hunger, Jr i
Director Ucensing Serd.m cc:
H. J. Miller, Administrator, Region I, USNRC W. L Schmidt, USNRC Senior Resident inspector, PBAPS I
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