IA-86-784, Package Consisting of Request for Addl Info Re Alternative Pipe Break Criteria Attached to NRC to Util

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Package Consisting of Request for Addl Info Re Alternative Pipe Break Criteria Attached to NRC to Util
ML20214K274
Person / Time
Site: South Texas  STP Nuclear Operating Company icon.png
Issue date: 07/10/1986
From:
NRC
To:
Shared Package
ML20214K217 List:
References
FOIA-86-784 NUDOCS 8612020245
Download: ML20214K274 (3)


Text

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i ATTAC,HMENT REQUESTFORADDITI'h,iALINFORMATION

1. Material Characterization a) For the base and weld metal actually in the South Texas surge line provide the mechanical properties (e.g. ultimate and yield strengths) or other significant material property, which will characterize the mate' rial.

1 b) Indicate the type of weld and post weld heat treatment used to fabricate the welds in the surge line.

c) Provide a materials evaluation to demonstrate that the material stress-strain curve, Jic, and J-R curve used in the analyses are representative of the material in the surge line. This evaluation should follow the general guidelines in NUREG-1061, Vol. 3, and include a comparison, of the material properties for the surge line to the material properties for test data.

2. History of Cracking 4

Section 2.0 of WCAP 10489 should include references to NUREG-0691 and

NUREG 0531 reports. Evaluate the susceptibility of the surge line to j stress corrosion cracking that is described in these NUREG's.
3. Loads l$d20goyj5861124 GRABER86-784 PDR 4

a) List individual axial loads and bending moment components used to determine the resultant axial forces and bending moments indicated on page 3-2 of WCAP 10489.

b) Provide a qualitative discussion of why a circumferential flaw in l

a straight pipe section is more limiting than a longitudinal flaw in an elbow or other component.

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4. Stability Analysis ..

a)

How were loads combined to d fermine the crack opening area in the leak rate calculation? Provide justification that the method of combining loads is conservative, b)

The stability analysis should meet the margins on load and flaw size in Sections 5.2 (h) and (i) and factor of 10 on leakage discussed in Section 5.7 of NUREG 1061 Vol. 3.

c)

The bilinear stress strain curve is a nonconservative representation of the data points shown in Figure 5-11 of WCAP 10489.

Provide justification that these curves conservatively ,

represent the surge line material described in item 1.

d)

Describe the method of validating (bench marking) each computer code used in the leak rate and fracture mechanics calculations.

5. Leak Rate Analysis The crack opening area used in the leak rate computation is the average of the opening area obtained from displacements at the pipe inner and outer surfaces.

more appropriate. It seems that the minimum area would be Provide justification for using the average value.

6. Fatigue Crack Growth Analysis a)

The data cited in Reference 8-2 as the basis for the fatigue crack growth rate should be included in the report in graphical form that would illustrate and justify the fatigue crack growth rate constants in equation 8-4 of WCAP 10489. These equations should represent the fatique crack growth rate of the material characterized in item 1.

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df b) The applicant will perform s realistic analysis as possible using service level A and B loads. The aspect ratio for the postulated crack in the fatigue evaluation should be 6. The aspect ratio should remain constant throughout the analysis.

Unless otherwise justified the maximum allowable flaw depth is the smaller of:

. (1) 60% of the wall' thickness, or (2) the depth at which the plastic zone is equal to the remaining ligament.

c) The length of the fatique crack must be less than both:

3 (1) the length of the instability thru-wall crack at J2 (N+SSE) and (2) 1/2 (instability thru-wall flaw at N+SSE)

The applicant is requested to confirm that the fatigue analysis includes the items listed in b) and c), above.

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