ML20236M010
| ML20236M010 | |
| Person / Time | |
|---|---|
| Site: | Arkansas Nuclear  |
| Issue date: | 03/04/1998 |
| From: | Doctor S PACIFIC NORTHWEST RESEARCH CENTER |
| To: | Howe A, Diane Jackson NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS), NRC OFFICE OF NUCLEAR REGULATORY RESEARCH (RES) |
| Shared Package | |
| ML20236J176 | List: |
| References | |
| FOIA-98-164 NUDOCS 9807130264 | |
| Download: ML20236M010 (4) | |
Text
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l From:
' Doctor, Steven R' < steven. doctor @pnl. gov >
To:
DAJ1 @ nte. gov" <DAJ1 @ nrc. gov >, AGH1 @ nrc. gov.. 3 s2F5 Date:
3/4/98 3:20pm
Subject:
Near Field Effects I spent some time talking today with Jerry Posakony. Jerry began working in UT back in the mid 50s and one of his areas of expertise is ultrasonic transducer.
I asked him if there was something going on that I was missing. He agreed that working in the near field zone must be done with great care. He noted that at the location of the root of the weld the UT response will be about 1/2 of that at the near to far field transition (2.7'). But then he went on to qualify this by stating that this will be a function of the bandwidth of the transducer. The factor of 1/2 will pertain to transducers with a 50% bandwidth. If the Bandwidth of the transducer is 100% or larger then there will effectively be no near field zone amplitude variations. So one of the things that will need to be known is what is the bandwidth of the transducers that are being used. We need to know this in the steel, Jerry is going to provide me with an ASTM standard that he has been working on to do this. What I am now thinking is that we will put a couple of side drilled holes in a piece of steel and take this to ANO.
Then have them manually place their transducer on this and record the A-scan that is produced for each side drilled hole. This information can be used to determine the bandwidth (it will be easier and more automatic if they can display the A-scan in the frequency domain). I willlook into the P-scan info l
and see if this mode is available. If not I will request a printed copy of the A-scan display at that time so that we can compute it by hand.
We discussed the performance that they were quoting on the sizing and he was in total agreement that they should be systematically oversizing by values more than what they were citing. He felt that they should be doing one thing for detection and then using highly focused transducers (focal spot size less than the smallest flaw of interest) at the location of the flaw to achieve the best sizing results. He cited his experience in using and observing the P-scan and that the sizing can be done repeatably with reference to calibration flaws that are the same (type and size). (We will need to see the data to better understand how they are achieving this performance.) We discussed the potential problem that they are using fairly nice thermal fatigue cracks for the demonstration, but actual fabrication flaws tend to be not so well behaved acoustically. The fabrication flaws tend to not just be in one plane, tend to be irregular, and they tend to have slag or porosity around them. In other words they are more complex and this adds to the difficulty of sizing them accurately. I believe that we will need to examine this procedure very closely to assure ourselves that it will be robust when applied to real flaws.
l These are the latest thoughts.
Steven R. Doctor
- Pacific Northwest National Laboratory P. O. Box 999, MSIN K5-26 Richland, WA 99352 9807130264 980630
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DUMS98-164 PDR 0..:
Phone: 509-375-2495 Fax: 509-375-6497 Email: steven. doctor @pnl. gov l
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Subject:
Near Field Effects To: "'DAJ1 @ nrc. gov" <DAJ1 @ nrc. gov >, AGH1 @ nrc. gov" <AGH1 @ nrc. gov >,
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3/4/98 3:20pm From:
' Doctor, Steven R' < steven. doctor @pnl. gov >
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