ML20127J298
| ML20127J298 | |
| Person / Time | |
|---|---|
| Site: | Quad Cities  |
| Issue date: | 05/16/1985 |
| From: | Rybak B COMMONWEALTH EDISON CO. |
| To: | Harold Denton Office of Nuclear Reactor Regulation |
| References | |
| GL-84-11, NUDOCS 8505210440 | |
| Download: ML20127J298 (9) | |
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@ One First National Plan Chicago. litinois Commonwealth Edison Address Reply to: Post Office Box 767 Chicago. Illinois 60690 May 16, 1985 Mr. Harold R. Denton, Director Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, DC 20555
Subject:
Quad Cities Station Unit 2 1985 IGSCC Weld Inspection Analysis on Weld 10S-F5 NRC Docket No. 50-265
Dear Mr. Denton:
On May 1985 Commonwealth Edison (CECO) presented to the Staff the results of our Generic Letter 84-11 inspection at Quad Cities Unit 2 and in particular, addressed concerns raised by the Staff on the results for some five welds. For one of those welds 10S-F5, it was agreed to present additional analytical information to support our position that the weld with its existing crack indications is acceptable for an additional cycle of operation.
The attached summaries of analytical results for Weld 10S-F5 (Attachments A and B) demonstrate that there is no loss of design safety margin over that provided in the ASE Boiler and Pressure Vessel Code for Class 1 piping. -The analysis presented in Attachment A demonstrates that this weld is in compliance with the requirements of the 1983 Edition of ASE Section XI with addenda through Winter 1983 as modified by USNRC Generic Letter 84-11. The analysis presented in Attachment B addresses the following concerns:
1.
To conservatively account for postulated brittle fracture due to potential low fracture toughness of flux-welded metal, the allowable end-of-cycle flaw depth ratio is based upon newly proposed ASE Section XI Table IWB-3461-5 and Generic Letter 84-11 requirements.
2.
To conservatively address the concern over the effectiveness of induction heating stress improvement (IHSI) on flawed welds, the predicted IGSCC flaw growth for a fuel cycle is based upon a weld residual stress indication only partially improved by IHSI.
We feel that these results adequately demonstrate the acceptability our position to continue operation for an additioni cycle without a weld overlay repair. These analyzes were conservatively done and demonstrated adequate margins to the applicable Codes and NRC guidance. Furthermore, this weld is on the downstream side of an isolation valve which is closed during power operation, that is, it is only open when the shutdown cooling system is in operation.
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8505210440 850516 l
PDR ADOCK 0500026S G
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!H. R. Deriton May 16, 1985 A
If you have any additional questions concerning this matter, please contact this office.
' One signed original ~ and forty (40) copies of this letter and its attachments'are provided'for your use.
Very truly yours, f
/
B. Ry Nuclear Licensing Administrator
' Im
' Attachment cc: NRC Resident-Inspector - Quad Cities R. Bevan - NRR gL i-l
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m 9..
r ATTACHMENT A
SUMMARY
OF ANALYTICAL RESULTS FOR WELD 10S-F5 Pipe Geometry:
Pipe-outside diameter
= 20" Pipe wall thickness
= 0.96" Flaw
Description:
Fall 1983 Outage Spring 1985 Outage 3 " x 18% Circ. (P.S.)
9" x 11% Circ. (P.S.)
8 " x 12% Circ. (P.S.)
10" x 17% Circ. (P.S.)
3" x 13% Circ. (P.S.)
Applied Loads:
Load Dead Thermal Internal-Tyge Weight Expansion Seismic Pressure Axial (1bs) 398 37,410 1,065 392,500 Moment (in-lbs) 144,315 2,698,380 163,023 0
Applied Stresses (psi) :
Dead Thermal Internal-Weight Expansion' Seismic Pressure-561 10,993 642 6,510 Page 1 of 3
77 Flawed Pipe Analysis:
o Assumed'360 flaw length-by-17% flaw depth.
o Crack growth predicted for combination of primary (dead weight and internal pressure) and secondary (thermal expansion and as-welded / post-IHSI residual) stresses.
.o Used conservative. crack growth law.
o For as-welded residual stress distribution, predict through-wall-IGSCC flaw growth in less than 18 months (one fuel cycle).
o Comparison of 1983 and 1985 flaw depth data shows no flaw growth, therefore, IHSI favorably altered as-welded residual stress pattern.
o For typical post-IHSI residual stress distribution, predict no flaw growth in 18 months (one fuel cycle).
PerUSNRCGenergcLetter84-11,allowableflawdepth o
for assumed 360 flaw length is 0.47 (2/3 of Table IWB-3641-1 source equation value) for dead weight, seismic, and internal pressure stress combination'.
o Measured flaw depth is a factor of 2.76 smaller than Generic Letter 84-11 allowable flaw depth.
Page 2 of 3
3.
'J Limit Load Failure Analysis:
o As required by USNRC Generic Letter 84-11, calculated limit load.
o Used net section plastic collapse limit moment equation-from Section A2.3.2 of NUREG-1061, Volume III.
o' Allowable limit moment calculated for primary loads (dead weight, seismic, and~ internal pressure).
o Allowable limit moment is 2,718,453 in-lbs.
Applied' moment is 307,338 in-lbs.
o o
Applied moment is a factor of 8.85 smaller.than allowable-limit moment for Generic Letter 84-11 100% through-wall by measured length flaw size requirement.
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Page 3 of 3 L
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b 1 :. -
ATTACHMENT,B
SUMMARY
OF ANALYTICAL RESULTS FOR WELD 10S-F5 PER PROPOSED TABLE IWB-3641-5
'Pi.pe' Geometry:
'Dipe outside diameter
= 20"'
Pipe wall thickness
= 0.96" Flaw ~
Description:
Fall 1983 Outage
' Spring 1985 Outage 3 " x 18%~ Circ. (P.S.)
9" x 11% Circ. (P.S.)
8 " x 12% Circ. (P.S.)
10" x 17% Circ. (P.S.)
3" x 13% Circ. (P.S.)
- Applied Loads:
Load Dead Thermal Internal Type Weight Expansion Seismic Pressure Axial (lbs) 398 37,410 1,065 392,500 Moment (in-lbs) 144,315 2,698,380 163,023 0
Applied Stresses (psi):
Dead Thermal Internal Weight Expansion Seismic Pressure 561 10,993 642 6,510 Page 1 of 4 l..
u
+-
(
- 91.,
~
' Allowable:End-of-Cycle-Flaw Depth Ratio:
o
- o. ' Stress Ratio M(P
+Pb+ e!*
} !
=-
m m-561 psi + 642 psi + 6,510 psi
= 7 ', 713 ' p s i -
P [+ Pb
=
P /2.77
= 10,993 psi /2.77.
= 3,969 psi e
M
= 1.0 for pipe diameters less-than 24" welded together using SMAW S,
= 16,950 psi fgr TP304 stainless-steel at 550 F Stress Ratio
= 1.0 (7,713 psi + 3,969 psi)/
16,950 pai
= 0.69 o
Flaw Length Ratio = ( 9 " + 10 " + 3 " ) / (20" - 0.96") n
= 0.37 o
Allowable End-of-Cycle Flaw Depth Ratio per Proposed Table IWB-3641 =-0.54 i
o Allowable End-of-Cycle Flaw Depth Ratio per USNRC Generic Letter 84-11
= 2/3 (0.54)
= 0.36 Page 2.of 4 u.
(-
T u
Flawed Pipe Analysis:
o Assumed 360 flaw length-by-17% flaw depth.
o Crack growth predicted for combination of primary (dead weight and internal pressure) and secondary (thermal expansion and as-welded / post-IHSI residual) sustained stresses.
o Used conservative crack growth law.
o For as-welded residual stress distribution (assumes no credit for IIISI) shown on Page 4 of 4, predict IGSCC flaw to grow to Generic Letter 84-11 allowable end-of-cycle flaw depth ratio in 4 months.
o For partially improved residual stress distribution shown on Page 4 of 4, predict IGSCC flaw to grow to Generic Letter 84-11 allowable end-of-cycle flaw depth ratio in 18 months (one full cycle).
o For IHSI residual stress distribution shown on Page 4 of 4, predict no IGSCC flaw growth.
Page 3 of 4 L
a.
e 3
+30 ksi
+8.1 ksi
+7.5 ksi l
Outside Pipe Surface
-14.2 ks' 50s
-28 ksi 19%
[
I Inside
+30 ksi
-7.5 ksi
-27 ksi Pipe Surface b
O AS-WELDED RESIDUAL STRESS PARTIALLY IMPROVED IllSI RESID,UAL STRESS DISTRIBUTION
- RESIDUAL STRESS DISTRIBUTION
- DISTRIBUTION
- Bounds stress distributions presented in Figure III-34 of EPRI Document No. NP-2662-LD, December 1982.
_ _ _ _, _