ML19319E083
| ML19319E083 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 11/16/1972 |
| From: | Maccary R US ATOMIC ENERGY COMMISSION (AEC) |
| To: | Deyoung R US ATOMIC ENERGY COMMISSION (AEC) |
| Shared Package | |
| ML19319E080 | List: |
| References | |
| NUDOCS 8003310593 | |
| Download: ML19319E083 (4) | |
Text
p) '.
i CGe /)
t
,,tw en
\\/
t g'e, UNITED STATES f
ATOMIC ENERGY COMMISSION
. h.-].
J g
W ASHINGTON. O.C. 20545
'% U NOV 161972 u,,,,,,
Richard C. DeYoung, Assistant Director for Pressurized Water Reactors Directorate of Licensing REVIEW OF " FINAL REPORT ON MINOR IMPERFECTIONS FOUND IN PIPE WELDS AT THE RANCHO SECO NUCLEAR GENERATING STATION", DOCKET No. 50-312 (OL)
Plant Name: Rancho Seco Nuclear Generating Station Licensing Stage: OL Docket Number:
50-312 Responsible Branch and Project Manager: PWR-4; B. C. Buckley Requested Completion uate: November 3, 1972 Technical Review Branches Involved: Materials Engineering Branch Description of Task: Review of Construction Related Incident Report Review Status: Completed The report " Final Report on Minor Imperfections Found in Pipe Welds at Rancho Seco Muclear Generating Station" has been reviewed by the Materials Engineering Branch, Directorate of Licensing. We conclude
)
that pipe welds containing minor imperfections of the type evaluated in g
this report are acceptable, provided that the applicant furnish addi-tional assurance of the adequacy of austenitic pipe welds considering the actual test results obtained in the test program covered by this report. Details of our review are $n the enclosure.
QQL m R. R. Maccary, Assistant Director for Engineering Directorate of Licensing
Enclosure:
Review of Report
-i d
8oos310Tf3
(
L) i I
r f
RANCHO SECO - REVIEW OF " FINAL REPORT ON MINOR IMPERFECTIONS FOUND IN PIPE WELDS.tT THE RANCHO SECO NUCLEAR GENERATING STATION" MATERIALS ENGINEERING BRANCH, L Summary of Report Minor imperfections (up to 15 mils in depth) were found to be present in i
some pipe welds that showed " dark" and "lig'ht" lines on radiographs.
l Investigations indica.ted that these " lines", and the minor imperfections, were associated with weld joint variables of fit up and " roll over" on the I.D. reinforcement. Improvements in fit up, veld procedure and purge gas control were _ instituted to minimize conditions leading to
" lines" and minor imperfections.
s b
Because " dark lines" could mask serious weld defects, all safety related butt welds showing dark lines will be repaired. Weld joints showing
" light lines" will 'not be repaired, as they meet the applicable code (ANSI B31.7) according to,the applicant. Although weld joints showing
" light lines" may also contain minor imperfections, they are considered by the applicant to be acceptable, based on results of an experimental program run to evaluate the effects of these minor i= perfections on the fatigue life of the welds.
This experimental program consisted of fatigue tests on simulated pipe joints, specimens cut from pipe joints, and a few tests on actual full p
d we ww-
~
')
?
~
~ size pipe joints. All three types of tests were run on austenitic naterial, but only simulated pipe joints were tested of carbon steel.
Conclusions reached by the applicant from the results of these tests were:
1.
Minor imperfections did not affect the fatigue life of austeniti welds because the failure location was generally not at the
~
imperfection.
2.
Minor imperfections did reduce the fatigue strength of the carbon indices to 2.0 over the steel welds, and an increase in K2 and K3 L
Code values of 1.8 and 1.7 was recommended.
The applicant stated that the stress indices used for evaluating welds in safety related Seisnic Class I carbon steel piping will be increased to 2.0.
Repair or resupport will be applied to any weld joints exceed-ing allowable limits using the higher indices.
S 9
l l
v)
I
~
I
c-
?-
\\
3-Materials Engineering Branch Evaluation We agree with the analysis of the problem, actions taken to reduce the Probability of occurrence of minor imperfections, and the interpretation of the results of the experimental program with the following exceptions:
1.
Although analysis of the results of.the fatigue tests on austenitic Pipe welds showed that failure usually did not take place through the imperfection, the average number of cycles to failure was
~
slightly. lower in those specimens where it did.
This indicates that there is some detrimental effect associated nith the imperfections 1
2.
Our evaluation of the actual test data on austenitic pipe welds indicates that higher stress indices may also be required on austenitic weld j i t s,
ons similar to those used in the test program.
We, conclude that pipe velds having " minor imperfections" of the type evaluated in this report are acceptable, provided that the applicant furnishes additional assurance that pipe welds that may contain minor
~
imperfections have adequate fatigue strength margin, considering the actual fatigue properties obtained-in the experimental program.
~
I g~'sp 4
ji l
i f
r-,
m e---
~
r