ML20135G055
| ML20135G055 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 09/04/1985 |
| From: | NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| To: | |
| Shared Package | |
| ML20135G051 | List: |
| References | |
| 50-423-85-22, NUDOCS 8509180086 | |
| Download: ML20135G055 (1) | |
See also: IR 05000423/1985022
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4.
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CORRECTED COPY
(1) The ability of ultrasonic waves to penetrate cast stainless steel
material.
(2) The adequacy of the ultrasonic calibration block for ultrasonic
testing of cast stainless steel material.
Three representative samples of Millstone centrifugally cast piping con-
taining 15% through wall depth fatigue cracks were UT examined with
defects verified. Another UT demonstration on weld LP-EC2-SWB was per-
formed with results as follows:
ID reflectors were detected inter-
mittently, 360 , adjacent to the weld. The reflector (indication)
appeared to be a counterbore condition. A geometric plot of this reflec-
tor was made, and the reflector was found to be approximately 1
1/4" from
the weld root area. The ID of the counterbore was previously blended
smooth, with the machine edges rounded out.
The inspector believes that
due to transducer wobble, beam spread and, redirection of the beam in the
cast stainless steel material, this reflector was incorrectly reported off
location by 9*.
It appeared that the recorded reflector was probably due
to ID surface irregularities originating at the weld root. The 9 shift
represented a difference of 1 1/2" from the actual area (weld root) to
the recorded reflector, causing problems with reported information.
~
However, the inspector felt that a significant indication could have been
detected using the licensee's method of ultrasonic examination.
Exact
sizing and location of indications still would remain a problem when per-
forming UT on this type of material.
A single calibration block, identified as UT-7 (3.28" thickness), was used
for all main coolant loop ultrasonic examinations. The test block
material is SA-351, grade CF8A, and was manufactured from a cast elbow. A
surface check was performed on the calibration block (125 RMS) and also on
the required examination area of the piping (32RMS). A signal amplitude
comparison was performed by the licensee between the calibration block,
A
centrifugally cast pipe and elbow.
The amplitude from the calibration
W
block (cast elbow material) was essentially equal to the elbow examined.
The centrifigully cast pipe signal amplitude was 6 db greater than the
calibration block. The range of thickness for all components examined was
2.1" to 3.81", as reported on the licensee's ultrasonic examinations
records. Because of the difference between the thickness of the calibra-
tion block and the pipes examined, it appeared that the thickness require-
ment of ASME section XI Appendix III, Paragraph III - 3410 had not been
met. This problem is unresolved pending a review of the licensee's basis
for use of the calibration block.
(423/85-22-04)
6.
Review of NDE Procedures:
The following NDE procedures were reviewed to verify their technical
adequacy and conformance to industry Codes and Standards:
8509180086 850904 ~
ADOCK 05000423
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