ML20100G447
| ML20100G447 | |
| Person / Time | |
|---|---|
| Site: | Peach Bottom  |
| Issue date: | 02/16/1996 |
| 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 9602230186 | |
| Download: ML20100G447 (5) | |
Text
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EtItlon support Deptrtment
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965 Chesterbrook Boulevard Wayne, PA 19087-5691 February 16,1996 Docket Nos. 50-277 50-278 License Nos. DPR-44 DPR-56 U. S. Nuclear Regu'atory Commission Attn: Document Co*rol Desk Washington, D.C. 20555 Subject.
Peach Bottom Atomic Power Station, Units 2 and 3 Response to Questions Regarding a Laak in the Reactor Water Cleanup System (RWCU) Piping
Dear Sir:
In a corwersation between M. C. Kray (PECO Energy) and J. W. Shea (U. S. Nuclear Regulatory Commission (USNRC)) on November 13,1995, detalis concinning a leak in the Reactor Water Cleanup (RWCU) System piping were discussed in that conversation, the USNRC provided five
. quotions to which PECO Energy was requested to respond Each question is restated boiow foi; owed by PECO Energy's response.
USNRC Question Number 1:
What were the operating conditions for the pipe in which the crack was found, i.e., pressure and temperature?
PECO Energy Response.
On November 9,1995, a leak was discovered during the performance of a contaminated pipe wall.down procedure in the Peach Bottom Atomic Power Station (PBAPS), Unit 3 RWCU System pipng. This leak was located near an elbow-to-pipe weld in the retum portion of the RWCU Sydem piping at the inlet to the final stage of the Regenerative Heat Exchanger (see Attachment). The intamal pressure of the piping at the location d the leak is estimated to be 1050 poig. The nomal operating temperature at the inner diameter of the leak location is estimated to be 330Y.
USNRC Question Number 2:
What were the results of the non-destructive examination?
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February 16,1996 i
Page 2 i
- i PECO Energy Renoonaa.
In an eNort to expedite repair of the weld and to minimize radiation worker exposure, no Ultrasonic Testing (UT) was performed while the piping was intact. In the process of removing the piping, the pipe was cut too close to the leak such that no tR could be performed at the leak location Rather, a dye penetrant examination d tlw inner diameter of the pipe revealed a crack on the circumference at the top inside of the pipe. The crack was 1.3 inches and was adjacent to the weld on the pipe side. Additionally, the dye penetrant confirmed three longitudinal cracks of lengths.86,.75, and.80 inches at a location of 90 degrees from the top of the pipe on the elbow side of the weld. These longitudinal cracks were within a one inch circumferential band on the piping Sullicient pipe length was ava8able to confirm the presence of these longitudinal cracks witn UT. All cracking was attributed to Intergranular Stress Corrosion Cracking (IGSCC).
An approximate 5-foot section of the piping was removed for examination and repair. This section induded two elbows and the four elbow-to-pipe welds. A UT of a second elbow wold identified four longitudinal cracks. Two cracks were on each side of the weld and were.65 inches These longitudinal cracks were within a one inch circumferential band on the piping An examination d the remaining two elbow welds revealed no IGSCC indications.
USNRC Question Number 3:
Provide a discussion regarding the replacernent of the piping, the type of piping that a being replaced, and the Intergranular Stress Corrosion Cracking susceptibElty of the piping being replaced.
PECO Energy Resoonse.
The repair was completed, and the RWCU System was placed back in service on November 12, 1995. The removed pipe and elbows were Type 304 stainless sPsel. The piping was fabricated by the Regenerative Heat Exchanger vendor and was fumished as an assembled unit with 3 stacked heat exchangers. The section of replaced piping is U-shaped,4-inch nominal diameter, Schedule 80 pipe, which includes two elbows. This section of piping connects the shell ends of the middle and upper heat exchangers The pipe-to shell welds were not replaced. The piping was replumi with new pipe and fittings composed of Type 304L stainless steel which is not susceptible to IGSCC. The weld faler metal is Type 308. The use of this filler does not permit the welds to be improved above a Category G weld. A Category G weld is defined in Generic 1.mtter 8841, "NRC Position on Intergranular Stress Corrosion Cracking (IGSCC) in BWR Austenitic Stainless Steel Piping.'
USNRC Qusation Number 4:
Are similar cracks occurring on the PBAPS, Unit 2 piping? Are any associated exams planned?
PECO Enerav Resoonse.
No cracks are known to exist in the PBAPS, Unit 2 RWCU System outboard d the containment isolation valves As a result of this event, two welds, similar to the welds which experienced IGCCC in PBAPS, Unit 3, wil be examined on the PBAPS, Unit 2 RWCU System. These welds wiu be examined as a part of the GL 8841 inspections planned for the current cycle at PBAPS, Unit 2.
February 16,1996
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Page3 USNRC QuestKm Number 5.
Are any sample expansions planned? When would these exams be poibir,6d?
PECO Energy Response.
As stated previously, the leak (later confirmed as IGSCC) was identitled as part d the contaminated pipe walkdown procedure, which is outside d the Generic Letter 88-01 sample inapartiari program. However, as discussed in response to Question 2, an additional three welds were inspected.
If you have any questions, please contact us.
Very truly yours, h $ < W A S l,r,a G. A. Hunger, Jr.
Director - Licensing Attachment cc:
T. T. Martin, Administrator, Region I, USNRC W. L Schmidt, USNRC Senior Resident inspector, PBAPS 4
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