ML20084B277
| ML20084B277 | |
| Person / Time | |
|---|---|
| Site: | Byron  |
| Issue date: | 04/18/1984 |
| From: | Tramm T COMMONWEALTH EDISON CO. |
| To: | Harold Denton Office of Nuclear Reactor Regulation |
| References | |
| 41906, 8494N, NUDOCS 8404260142 | |
| Download: ML20084B277 (3) | |
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Commonwrith Edison One First Natior.at Plaza. Chicago, lilinois
(
v Address Reply to. Post Office Box 767 g(-
ChtCago. Illinois 60690 April 18, 1984 Mr. Harold R.
Denton, Director Office of Nuclear Reactor Regulation U.S.
Nuclear Regulatory Commission Washington, DC 20555
Subject:
Byron Generating Station Unit 1 Preservice Inspection Program Plan NRC Docket No. 50-454 References (a):
August 26, 1983 letter from T.
R.
Tramm to H.
R. Denton (b):
December 6, 1983 letter.from T.
R.
Tramm to H. R. Denton
Dear Mr. Denton:
~
This 1etter provides additional information in support of the requests contained in references (a) and (b) for relief from the requirement to examine certain cast stainless steel components during the Byron 1 preservice inspection program.
Attachment I to this letter summarizes attempts which have been made to examine by ultrasonic means typical cast stainless steel components at Byron 1.
None of these efforts were successful.
Please address further questions regarding this matter to this office.
Very truly yours,
/ r $< p/ A ~
T. R.
Tramm Nuclear Licensing Administrator bs Attachment ggd 8494N e4o4aeot42 e4o41s i
PDR ADOCK 05000454 G
PDR __
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ATTACHMENT I Summary of Cast Stainless Steel Examinations for Byron Unit 1 i
1.
Welds of Pipe-To-Cast Stainless Steel Components and Elbows O
Ultrasonic examinations were performed on these welds with a 450 shear wave transducer calibrated on a block made of the pipe material per ASME Section XI.
Axial scans were made f rom the pipe side to examine the required inspection volume of the piping material and weld metal for reflectors parallel to the weld.
Longitudinal wave examinations were made on all welds to obtain thickness measurements and to detect any defects parallel to the surface.
Since an additional.30.to 40 dB gain was needed to see the back reflection on the cast stainless steel side it was concluded that shear wave examinations on this side would be meaningless.
Th e re f o re, axial scans' from the cast side were not performed.
}
Relief Request NR-6 requests relief from Section XI requirements.
Additional examinations of these welds include circumeferential ultrasonic scans on the weld crown in both directions for transverse
)
reflectors and ASME Section _III radiographs.
2.
Welds of Reactor Nozzle'-Safe Ends and Steam-Generator Primary j
Nozzles-to-Cast Stainless Steel Elbows The reactor nozzle safe end-to-cast stainless steel elbow weld originally were to be examined from the inner diameter by the automated reactor vessel examination tool.
However, discovering that this could not be done and -being aware thatl 450 shear wave examinations are meaningless on cast stainless steel an examination procedure utilyzing a 2.25 megahertz. (MHZ) 450 refracted longitudinal wave transducer was developed.
This procedure was f'
developed-and qualified on a mockup consisting of safe end material welded to cast stainless steel.- The cast stainless steel material' was obtained from the manuf acturer of the cast stainless-steel elbows at Byron Units 1 and 2 (and also at Braidwood Units 1 and 2).
The mockup contained two holes in the cast stainless material.
One hole was at the weld' fusion line 1/4 T-from the outer diameter (0.0.) of the cast stainless material.
The other hole was in 'the corner of the required inspection volume, 1/3 T from the-inner diameter and:approximately 1/2 inch from the fusion line into the.
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cast material.
i Because the' acoustic properties of-cast' stainless steel are unpredictable, a test of the attenuation characteristics of the mockup material and the cast elbows was performed.
Using a 1 MHZ longitudins) wave transducer on_ the cast side of the mockup, 24 to
- 26. decibels (dB) gain was needed.to-obtain.an;80_ percent back wall reflection.
With a 2.25 MHZ transducer 32 to 34'dB-gain was needed.
to see.the back reflection.
Perf orming the - same test on a Byron -
Unit 2 pipe-to-elbow weld 28 to 32 dB, gain was needed;for 1 MHZ and 40 dB gain'was required for 2.25 MHZ. :Thus,- it was concluded that
'. the cast elbows installed in the plant are more attenuative than the cast material in the mockup.
Similar results were obtained from the elbows at Braidwood Units 1 and 2.
The Byron Unit 1 elbows can be expected to have the same attenuation properties since the same manufacturer provided elbows for all four units.
This conclusion is substantiated by the f act that longitudinal examinations performed on the Byron Unit I welds for thickness measurements required 30 to 40 dB gain to obtain a back reflection.
Th e 450 refracted longitudinal wave transducer was chosen to be used on the reactor safe end-to-elbow welds' and the ste~am generator primary nozzle-to-elbow welds in an attempt to perform a meaningful exam on the cast material.
However, during calibration the hole at the fusion line 1/4T from the 0.D. could not be seen from the cast side.
As a result of this and because the elbows have even higher attenuation properties than the mockup it was concluded that an axial scan from the cast side of the welds using refracted longitudinal wave would also be meaningless.
Therefore, these scans were not performed.
Relief Requests NR-4 and NR-8 request relief from Section XI requirements for these examinations.
Refracted longitudinal wave was used to examine these weTds axially from the safe-end side.
During calibration on the mockup both holes in the cast stainless material were seen with 1/2 V-path shooting across the weld.
Th e ref ore, it is estimated that during the scans from the safe-end side the heat-affected-zone (HAZ) on the cast stainless side.was examined up to 1/2 inch beyond the fusion line.
Circumferential ultrasonic scans were also done in both directions and prior to the preservice inspections ASME Section III radiographs were made.
DPC/sb/4190b C
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