ML20205T228

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Acceptance Criteria for Mid-Cycle Insp of Peach Bottom Unit 3 Recirculation Inlet Safe-Ends & Piping
ML20205T228
Person / Time
Site: Peach Bottom Constellation icon.png
Issue date: 05/28/1986
From: Branlund B, Kiss E, Ranganath S
PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC
To:
Shared Package
ML20205T219 List:
References
DRF-137-0010, DRF-137-10, SAS-86-35, NUDOCS 8606130080
Download: ML20205T228 (13)
v • d • e


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ATT/CEENP 3 Docket tb. 50-278 June 9, 1986 SAS-86-35 DRF-137-0010 May 28, 1986 l

ACCEPTANCE CRITERIA FOR THE j HID CYCLE INSPECTION OF THE j PEACH BOTTOM 3 RECIRCULATION INLET SAFE ENDS AND PIPING a

Prepared By: O S. Ranganath, Aanager Structural Analysis Services i

i Verified By 9.D3r.d . N M26/M B. J. Branlund,' Engineer Structural Analysis Services Approved By:

E. Kiss, Manager Plant Technology i

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SUMMARY

lC Acceptance flaw sizes are described for the mid-cycle inspection.of .

safe ends F and J. and three pipe welds in the Peach Bottom Unit 3 recirculation and RHR piping systems. The proposed limits are consistent I' with previously reported evaluations and are based on conservative crack (C- growth predictions. These limits assure that the required structural i

margins are maintained for the next operating cycle. Table 1 summarizes ._

the proposed limits on the average and peak depths. .If the evaluation of

- the UT indications during the mid-cycle inspection is less than the -

f limits in Table 1. the plant can return to power.'as is' and continued f- operation up to the end of the fuel cycle is acceptable.

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- TABLE 1 MID-CYCLE ACCEPTANCE LIMITS

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Wald No. Mid-Cycle Limits on Depth; Percent of Wall Average Maximum

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f- Safe End J 27% 50%

Safe End F 24% 46%

2-AS-08 30% 50%

. . 2-BD-12 30% 45%

( 10-0-03 42% 42%

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1. INTRODUCTION IC 'C: '

Ultrasonic inspection- of the Peach Bottom Unit 3 recirculation piping, inlet safe ends, and RHR piping during the. 1985 outage revealed 1 '?

the presence of IGSCC indications in the inlet: safe ends and the piping.

-h Except for the safe ends and twelve pipe . welds (including 2-AS-08,

. C' *- - 2-BD-12 and 10-0-03) all welds with indications were weld overlayed. The

"- - safe ends and the twelve welds were shown to be; acceptable for continued il

  • operation for 18 months without repair. The crack growth assessment was I

y based on the conservative assumption of worst case water chemistry. It s was shown that the flaw size at the end of .18. months would still be within allowable values even af ter providing a margin on stress and an 4

- additional factor of 1.5 on flaw size (2/3 factor on Code limits per NRC .

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% approved procedures, Reference 3)..

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- - The analysis of the safe ends and the pipe welds are described in a'

  • detail in References 1 and 2. To provide further assurance of structural margin it was decided that a mid-cycle-inspection should be performed on

' safe ends F and J and pipe welds 2-AS-08, 2-BD-12 and 10-0-03. This can l be used to verify that the incremental crack growth during the nine month a

period was within the predictions in the original evaluation [1, 2)

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f The purpose of this report is to document acceptance flaw sizes for the mid-cycle inspection of the recirculation. inlet safe ends F and, J.

and pipe welds 2-AS-08, 2-BD-12, and 10-0-03. If the UT sizing of the indications during the mid-cycle inspection is less than the acceptance A. limits documented here, the plant can return to power 'as is' and continued operation up to the end of the fuel cycle is acceptable. If, i! however, the mid-cycle UT flaw sizes exceed the limits, more detailed l evaluation may be necessary.

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2. BACKCROUND C ~ "

Ultrasonic inspections were performed on the safe ~ ends.and.the pipe 3

welds during the 1985 outage. Flaw sizes from these inspections (in terms of percent of wall), and predicted crack depth af ter the 9 months prior to the mid-cycle examination are shown in the following table.

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,; Weld No. SAFE END 2-AS-08 2-BD-12 10-0-03 J F f Reported Depth

,( Maximum 33% 25% 40% 30% 25%

i Average 19% 16% 21% 21% 23%

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ll Predicted Mid-Cycle Crack Depth

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!! Average 27% 24% 30% 30% 42%

(Ref.1) (Ref.1) (Ref.2) (Ref.2) (Ref.2) i

The predicted average crack depths at the end of 9 months for the safe end were based on crack growth rates corresponding to lifetime water l' chemistry conditions and are consistent with the predictions in Reference
1. The predicted depth at the end of 9 months for the pipe velds considered shrinkage stresses based on measured values and as welded residuni stresses (i.e., no credit for IHSI). Thus, all predictions were based on conservative assumptions. With the expected improvement in water chemistry, actual growth is likely to be lower.

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! 3. TECHNICAL APPROACH FOR SETTING ACCEPTANCE LIMITS C The limits on the average depth proposed in this report are based on i the expected ersch growth during the nine months prior to the mid-cycle inspection and are consistent with References 1 and 2. This approach, based on the predicted crack growth, is reasonable for the average depth  ;

C since it is based on an integrated value from several measurements.

Figures 1-5 show the limits on the average depth in comparison with the
allowable values. It is seen that the limits on average depth assure l- th'at there is sufficient pipe area available to maintain the structural .;

8 margin required by the NRC and ASME Code criteria.

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The approach based on crack growth would be too restrictive for o -

highly localized peak depths. For example, destructive metallographic

( examination of the Unit 2 safe ends have confirmed that there can be p significant variations in depth even with small variations in the azimuthal location where-the UT measurement is performed. Thus, the UT sizing of a local ' cusp' should not be used as a tool for verifying crack growth prediction. The limit on peak depth is therefore based on the

.f Code allowable limits for short flaws (after taking the 2/3 factor per NRC procedures) and not on crack growth predictions. This is shown in Figures 1-5. For example, for a short flaw, the maximum allowable depth

,( for safe end J at the end of 18 months is 67 percent. Based on this the allowable size at the end of nine months for safe end J is 50 percent.

Similar values are shown for safe end F and the two pipe welds 2-AS-08 l{ .

and 2-BD-12. For veld 10-0-03, the average depth and the maximum depth

( were almost the same. The allowable value is therefore the same for both the average and maximum depth.

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l l With this approach full Code structural margins are maintained for for both the full circumferential case as well as the I

( all cases, i.e.,

localized cusp situation for both safe ends and piping.

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4. MID-CYCLE ACCEPTANCE CRITERIA

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Acceptance flaw sizes for the safe.. ends and pipe welds are

- ' . < ' documented in the following table. These are based on inspections after a nine month period. If the actual time period to the mid-cycle inspection is longer, the limits should be adjusted accordingly.

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Weld No. Mid-Cycle Limits on Depth, Percent of Wall

Aversge Maximum

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Safe End J 27% 50%

-0 Safe End F 24% 46%

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( 2-AS-08 30% 50%

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2-BD-12 30% 45%

10-0-03 42% 42%

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IEFERENCES f 1. CE Report NEDC-31086-P, " Evaluation of Crevice Cracking in Peach Bottom Atomic Power Station Unit 3 Recirculation Inlet Safe Ends."

2. CE Report SASR 86-61, " Weld Overlay Design and Analysis for the f'

Indications in the Peach Bottom Unit 3 Recirculation and Residual Heat Removal System."

3. NRC Document from Willit e J. Dircks to the. Commissioners, Subject I
Staff Requirements for Reinspection of BWR Yiping and Repair of Cracked Piping, NR0, November 7, 1983, (SECY-83-267C).

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1.0 NET $ECTsDN i COL L APSE o8 -

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9 Month i !go.s j

E 9 o 50% Mid Cycle U f k 2/3 sF ACTOR OF Limit on Crack Depth -

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l 27% Mid Cycle 33% Max Depth Limit on 4 - 9 Months Average Depth n 1985 Inspection g o.2 -

19% Average Depth 1985 Inspection

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46% Mid Cycle

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Limit on Average Depth

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