ML20236L772
| ML20236L772 | |
| Person / Time | |
|---|---|
| Site: | Palisades, Point Beach, Arkansas Nuclear, 07201007  |
| Issue date: | 03/06/1998 |
| From: | Howe A NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| To: | Doctor S Battelle Memorial Institute, PACIFIC NORTHWEST NATION |
| Shared Package | |
| ML20236J176 | List: |
| References | |
| FOIA-98-164 NUDOCS 9807130169 | |
| Download: ML20236L772 (3) | |
Text
_- -....
Y From:
Allen Howe To:
Intemet:pnl. gov:sr_ doctor, intemet:inel. gov:mta2...
Date:
3/6/9811:58am
Subject:
Latest on VSC-24 UT Yesterday,3/5/98, SFPO had two telephone calls with the VSC-24 Owners Group - VSCOG (ANO/ Palisades / Point Beach, SNC).
4 The following summarizes the phone calls:
In the first call, the VSCOG updated us on the status of the UT development process using the P scan system. This method involves a partial (-5") lift of the MSB in the MTC to gain access to the MSB shell side. Examination performance was acceptable at temperatures ranging from j
room temperature up to about 175 F, however, accuracy was affected when scanning was done at 200 F. A-Scan data is shown during data acquisition, but not saved. It is, however, possible to save A-scan data. The P-scan examination procedure is in a final draft format; the majority is generic, but certain parts are tailored to the P-Scan /ANO site-specific items. It discusses process, qualifications, and so-called essential variables.
The weld team described two issues to the VSCOG so they could address them during the inspection.
Issue 1 - UT "near field" effects. What measures will be taken to cddress UT examination in the near-field regime to assure reliable and repeatable examination results?
The VSCOG is aware of this situation. They do not consider it a significant issue as 20 scans have shown repeatable results, and many nuclear UT inspections are done in the near field.
They are prepared to discuss it further during the inspection.
Issue 2 - Transducer size. For flaw sizing, it is generally better to use transducers that produce the smallest practicable sound beam cross section at the flaw location. The transducer described by the VSCOG produces a sound beam cross sectional area much larger than most of the flaws that are being sized. What measures is the VSCOG taking to ensure accurate flaw sizing with the transducer proposed for this UT examination technique?
Similar to above, the VSCOG is aware of the situation, and will address it during inspection.
The technique they are using is approved through EPRl/PDI and they can get information from signals ringing at the tip of the flaw.
The VSCOG Indicated their dose assessment for the P-SCAN UT inspection method resulted in an estimated dose increase of -2 REM for each cask loaded. By comparison, the dose for the entire loading process of the last VSC-24 cask loaded at ANO was 500 millirem. NRC requested a second call to further discuss this issue. High gamma dose rates of
-10.7 R/hr, unshielded, and -1.8 R/hr, shielded, were estimated on contact in the MSB/MTC gap area. As stated above, access to the MSB shell from the side the requires the MSB to be lifted - 5 inches. The VSCOG was not satisfied with this increased dose burden and they are looking at altematives. These dose estimates have given the VSCOG pause and as a result the March 16,1998 inspection may be delayed.
One alternative yields an estimated per cask load dose increase of 200 MREM. This method i
9807130169 980630
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involves UT examination from the top, without a MSB lift. THE VSCOG is considering use of the TestPro ultrasonic inspection system from Structural Integrity Associates, Inc. So far, initial i.
examinations had been encouraging. The TestPro system uses the Time of Flight Diffraction (TOFD) techniques with two transducers mounted on the top of the weld (P-scan uses a side mounted transducer). This method results in very accurate sizing of flaws, but alone cannot locate the flaw precisely in the radial direction (distance from outside of shell towards conter of cask). Additional scans, using another technique, could pinpoint the flaw (s). No high l
temperature tests have been done with TestPro. Scans are done from the top of the weld, and no crown grinding is necessary.' TestPro records A-scans during acquisition for later analysis.
CC:
TWD2.TWPO.DAJ1, TWD2.TWPO.EMH1 i.
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V Mall Envelope Info:
(35002B30.A46 : 17 : 42080)
Subject:
Latest on VSC-24 UT Creation Date:
3/6/9811:58am From:
Allen Howe l
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WND1.WNP7:AGH1 Recipients Action Date & Time Post Office internet mta2 Post Office Intemet sr_ doctor Post Office TWD2.TWP0 DAJ1 CC (Deborah Jackson)
EMH1 CC (Edwin Hackett)
Post Office WND1.WNP7 Delivered 05/29/98 02:53pm AGH1 (Allen Howe)
CKB1 (Charles (Ken) Battige)
TJK1 (Timothy Kobetz)
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Pending Intemet:pnl. gov TWD2.TWP0 Pending TWD2.TWP0 WND1.WNP7 05/29/98 02:53pm WND1.WNP7 Files Size Date & Time MESSAGE 3793 03/06/9811:58am View 4109 03/06/98 06:58am i
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