ML20249C434
| ML20249C434 | |
| Person / Time | |
|---|---|
| Site: | Peach Bottom  |
| Issue date: | 06/23/1998 |
| From: | Geoffrey Edwards PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9806290332 | |
| Download: ML20249C434 (6) | |
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10 CFR 50.55a PECO NUCLEAR nco== c-v Nuclear Group Headquarters A DNir or PECO Ewucy 965 Chestertwook Boulevard j
Wayre. PA 19087-5691 j
i June 23,1998 l
Docket No. 50-277
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License No. DPR-44 U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555
Subject:
Peach Bottom Atomic Power Station, Unit 2 HPCI Suction Drain Line Proposed Non-Code Repair
Dear Sir:
In our letter dated June 17,1998, PECO Energy Company (PECO Energy) requested your review and approval for relief from specific requirements of Article IWA-4000 of the ASME Section XI Code,1980 Edition, with Addenda through Winter 1981 Addendum, in 3
accordance with 10 CFR 50.55a (g) (6)(i). This issue was also discussed in conference -
i calls between PECO Energy and the U. S. Nuclear Regulatory Commission (USNRC) staff on June 15 and 16,1998.
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Attached is our response to questions that were discussed in a June 19,1998 conference l
call between PECO Energy and the USNRC staff conceming the proposed temporary l
non-code repair of the High Pressure Coolant injection (HPCI) System suction drain line l
for Peach Bottom Atomic Power Station (PBAPS), Unit 2. As discussed in the call, verbal approval was granted as of 2:00 pm, Friday, June 19,1998, to perform the temporary non-code repair and retum the HPCI System to service. The repair was subsequently completed on Saturday, June 20,1998.
If you have any questions, please contact us.
Very truly yours, a
C)f&.x f
Garrett D. E wards Director, Licensing l
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Enclosure cc:
H. J. Miller, Administrator, Region I, USNRC i
A. C. McMurtray, USNRC Senior Resident inspector, PBAPS 9906290332 990623 PDR ADOCK 05000277
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RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION REQUESTED IN JUNE 19,1998 CONFERENCE CALL Question:
- 1. a) Will the welding technique involve temper beads?
Response
The welding technique will not involve temper beads.
Question:
- 1. b) If not, will there be more than one pass?
Response
The fillet welds will be multipass SMAW, using 3/32" diameter electrodes with an estimated three (3) to four (4) passes on the weld to the valve, and five (5) to six (6) passes on the weld to the coupling.
Question:
- 1. c) The WPS/POR indicate multipass groove, but are silent for fillet.
Response
The POR is based on the ASME Code,Section IX, which states that qualification on groove welds qualifies for all fillet welds.
Question:
- 1. d) What is the carbon equivalence of the fitting and valve body?
Response
Based upon the Certified Material Test Report (CMTR), the carbon equivalence for the coupling is 0.51%. The CMTR could not be located for the valve, therefore, based upon the specification limits for A-105, the maximum carbon equivalence would be 0.73%.
Question:
- 2. Has there been consideration for performing a helium leak test after welding?
Helium could be injected through the drain plug hole.
b'4.
- Juno 23,1998 L
Page 2 l
l Respons :
As stated in our call, although not required by the code, a pneumatic pressure test will l-be performed utilizing station air. (During the repair, a pressure test was performed at 170 psi. - This pressure is the accident pressure expected at this location. In addition, a
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VT-2 and soap bubble examination were performed at the welded locations with no
!L evidence ofleakage.)
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Question-
- 3. a) What is the status of the other discovered linear indication?
Responsei
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- The other identified flaw was removed and repaired in accordance with Code rules.
' Ouestion:
- 3. b) Are the two indications oriented on the same side of the pipe?
Response
Both indications were on the same side of the pipe.
Question:
3.' c) Was UT performed to size this flaw for the disposition?
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Response
An informational UT was performed on both indications. A magnetic particle
- examination was performed on the repaired location to verify removal.
Question:
'3. d) Were examiners and procedure qualified, and if so to what requirements?
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Response
The NDE procedures were qualified, and the examiner was qualified to SNT-TC-1 A.
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.'c Jun3 23,1998 Page 3 Question:
- 4. a) Did the EPRI report contain a microhardness traverse of the water-backed weld heat-affected zone (HAZ) for material with the same carbon equivalence and number of weld passes?
Response
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- The EPRI report testing consisted of microhardness, Charpy impact testing, and burst testing which showed that the heat-affected zones on the welds had good toughness propedies. The carbon equivalence for the EPRI test was 0.35% and 0.36% The welds were multipass, however, the specific number of passes were not described.
Question:
- 4. b) Was temper bead used?
Response
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No temper bead was used.
- 4. c) Does the overlay work at EPRI bound the expected hardenability for the Peach Bottom repair?
Response
Our review of the EPRI work has determined that the EPRI testing does bound the concem of heat-affected zone cracking from quenching effects of water backing. The EPRI testing was performed using A106B piping which had been thinned to 1/16",3/32" and 1/8", with water backing. This compares to the much thicker material for the HPCI drain line (0.382" for the coupling and 0.292" for the valve). Therefore, the net affect of
' the water backing on the cooling rates experienced in the heat-affected zone would be significantly less than the EPRI tests.. The EPRI results showed good heat-affected
. zone toughness even with very high cooling rates, as discussed in our response to question 4.a. The planned socket weld configuration also has been successfully demonstrated in previous applications.
Question:
- 5. Were the mock-up welds sectioned and microhardness traverses performed?
From the metallographic results, how much martensite is present? Is it tempered?
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Page 4
Response
The mock-up welds were not sectioned, nor was a metallographic analysis performed.
Based on a comparison to the EPRI report, the successful pressure testing and non-Destructive examination of the mock-up welds, no sectioning was determined to be necessary.-
Question:
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- 6. a) How will leakage be stopped prior to welding?
Resoonse:
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As stated in our call, a repair epoxy was to be used in stopping the leakage, however,
- the epoxy did not stop the leakage. Therefore, tape backing was used to stop the
- leakage, j-Question:
j; 6.L b)- If leakage is not completely controlled, what measures wil! be taken to minimize l
porosity or hydrogen cracking?
t
Response
As stated in our call, no welding would be performed if leaking was occurring..The plan,
- which was followed, called for welding to begin at the bottom of the collar and finish at the location closest to the HPCI System piping.
Question:
- 7. Provide discussion of implications of a failed repair effort.
t Responsa:
Th' repair' effort was successfully completed on' Saturday, June 20,1998. No failure of e
-the piping occurred. However, as stated in the June 19,1998 call, plugs and hose
. clamps were staged at the repair location in the remote event of a pipe break in the drain line.' If such a failure were to have occurred, the leakage rate through the break had been calculated to be 30 gpm. The unit would also have been shutdown in.
< accordance with the Technical Specifications. Sufficient makeup capability would have
- been provided by the Residual Heat Removal System, the Core Spray System, and the stay fill system, and as a last resort, the High Pressure Service Waic System. The repair welding was monitored through the vent hole, and NDE was performed following the repair.-
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/F' Jun3 23,1998 Page 5 Question!
- Provide additional information regarding the as-found condition of the indications.
Response
Although the indications are suspected to have resulted from vibration fatigue, a visual field inspection identified an overlap condition that may have resulted in a concentration
.of stresses in the flaw region. The vibration fatigue combined with the overlap condition could have contributed to the eventual leakage.
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