ML20070D082
| ML20070D082 | |
| Person / Time | |
|---|---|
| Site: | Calvert Cliffs  |
| Issue date: | 06/24/1994 |
| From: | Denton R BALTIMORE GAS & ELECTRIC CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9407070149 | |
| Download: ML20070D082 (6) | |
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4 Rom n n l'. Drn sus Italtimore Gas <md I:lectric Company Vu e l'rnident Cah crt ChHs Nuclear Powe r I'lant Nm Icar I:nergs 1650 Calvert Clips l'arlway Imby. Alaryland 2o(>57
.sio 3M-220o 13t. 4.g55 laal 4to 2(n.$.455 llattimore June 24,1994 U. S. Nuclear Regulatory Commission Washington, DC 20555 ATTENTION: Document Control Desk SUllJECT: Calvert Clifts Nuclear Power Plant Unit Nos.1 & 2; Docket Nos. 50-317 & 50-318 Rsvision to Reply to Noticq of Violation -- Non-sigsLructive Egminalien
REFERENCES:
(a) Letter from h1r. J. P. Durr (NRC) to hir. R. E. Denton (BGE), dated April 23,1993, NRC Region I inspection of Calvert Cliffs Units I rd 2 Inservice Inspection Activitics, Combined Inspection Report Nos. 50-317/93-08 and 50-318/93-08 (b) Letter from h1r. R. E. Denton (BGE) to Document Contrci Desk (KRC),
dated Jur.; 1,1993, Response to Non-destructive Exanination Notice of Violation (c) Letter from hir bl. W. Ilodges (NRC) to htr. R. E. Denton (BGE), dated July 22,1993, NRC Inspection 50-317/93-08 and 50-318/93-08 s
in response to the non-destructive examination violat i on stated in Reference (a), we submitted our response in Reference (b). AQer reviewing our response you stated the violation was still valid in Reference (c).
AQer further discussing the issue with your staff we accept the violation. Our revised response is provided in Attachment (1).
Should you have any questions regarding this matter, we will be pleased to discuss them with you.
Very truly yours, W m RED /MDM/bjd
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Attachment l 9407070149 940624 PDR ADDCK 05000317 0I[
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Document Control Desk June 24,1994 Page 2 cc: D A. Brune, Esquire .
J. E. Silberg, Esquire M. K. Boyle, NRC jj D. G. Mcdonald, Jr., NRC T. T. Martin, NRC P. R. Wilson, NRC R. I. McLean, DNR J.11. Walter, PSC 1
ATTACllMENT (1)
RILVISED RESPONSE TO NOllCE OF VIOLATION 50-318/93-08-01 Notice of Violation 50-318/93-08-01 states that c ,ntrary to Technical Specification (TS) 4.0.5, which requires inservice Inspection (IS!; of ASME Code Class 1, 2, and 3 components to be performed in accordance with Section XI of the ASME Boiler and Pressure Vessel Code, rejectable magnetic particle indications on main steam system welds 34-MS-2001-6 and 36-MS-2001-3 were examined and accepted using an ultrasonic examination method that faded to establish the dimensions of the flaws as required by ASME Section XI.
We accept the violation described in the report. As discussed in a conference call between members of our staff at.d NRC Regmn I stafT on March 11, 1994, our intentions with respect to this are strike were to conduct an ultrasonic examination to ensure its dimensions did not exceed the acceptance sta .! r6 of u; code and then to remove the are strike that caused the magnetic particle indications. We agre G. > dosem of the Inservice inspection (ISI) restJts resolution package prior to completion of tic ,. .:th ' t premature.
- 1. DESCRIPTION AND CAUSE OF VIOL ATION The facts and sequence of events regarding the inspection of the welds are accurately described in the inspection Repon. Although we later sized the flaw as required by the code, we prematurely closed the ISI Inspection results resolution package after our ultrasonic examination did not detect the indications. With regard to the ultrasonic method we used to determine whether the flaws could have exceeded the acceptance standards of the code, as stated in our initial response (Reference b), we asked the EPRI NDE Center to assess our technique. The response from EPRI is attached, and it concurs in the adequacy of the ultrasonic technique used for tha.s purpcsc,
- 11. CORRECTIVE ACTIONS TAKEN AND RESUI,TS ACillEVED The arc sinkes that caused the magnetic particle indications were removed and reexamined with satisfactory results on May 26,1993.
111. CORRECTIVE ACTi ONS WillCil Wil,L llE TAKEN TO AVOID FURTilER VIOLATIONS In our previcu , response (Refer .nce b) we stated we would use additional techniques to more exactly size indications. Mis requh ner, has been incorporated into our Matet als i Engineering and Analysis implementing .'rocedur 5.0v, " Acceptance ot'Section XI Examination Results" The procedure ensures a technique that s an c'.aracterize the flaw is used when evaluatmg indications. The use of supplemental NDE techniques vi phy sical measurements may be invohed in the charactenzation. We believe this change will ensure flaw characterizations will be achieved prior to closing weld examination packages.
IV. DATE WilEN FUI.l COMPI,l ANCE Wil.1, ilE ACillEVED Full compliance was achieved on May 26,1993, when the indications associated with the welds in question were removed and reexamined with satisfactory results.
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EPRI NDE CENTER E!ectnc Power Research insDtute Noncestruct:ve Evaluation Center Leadershtoin Technology Transfer February 4,1994 Mr. Dajun Song ISI Engineer Materials Testing & Evaluation Unit Trailer 22 Calvert Cliffs Nuclear Power Plant 1650 Calvert Cliffs Parkway I '. , MD 20657 --
SUBJECr: Full-vee detection of shallow outside surface cracking
Dear Dajun:
We have prepared a mockup and made ultrasonic measurements to address your issue regarding full-vec detection of shallow outside surface cracking. We found that cracking smaller than the maximum allowable flaw size was easily detectable using a conventional 45-degree shear wave technique at the full-vce path.
Three EDM notct s and four cracks were placed in the outside surface of a specimen of ferritic hot reheat piping. The wall tnickness was 1.32 inch. One of the EDM notches was an ASME Code calibration notch,1 inch long and 0.122 inch deep as specified by Section XI, Appendix III. Ultrasonic measurements were made using a Megasonics 0.375-inch diameter,2.25 MHz,45-degree shear wave search unit with a Panametrics Epoch 2002 instrument. All measurements were made at the full-vee path. Amplitudes are referenced to the calibration notch. The notch dimensions and associated ultrasonic responses are contained in Table 1.
Table !
EDM Notch Responses Notch Notch Notch Response Length Depth Depth Amplinide (inch) (inch) % wall) (% reference) 0.385 0.193 4.6 % 100 %
1.50 0.149 11.3 % 150 %
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F Dajun Song 4 Febmary,1994 Page 2 The longest allowable surface indication for this thicxness is 0.4125 inch (Table IWB-3514-4). The highest allowable depth for this length is 0.193 inch (Table IWB-3514-1).
One of the EDM notches was made 0.193 inch deep and 0.385 inch long to simulate this maximum allowable (minimum unallowable) flaw. The ultrasonic response of this semicircular notch was 100% of reference level.
Most cracking will have a less extreme aspect ratio. A second notch was machined -
0.149 inch deep and 1.5 inch long, the maximum allowable flaw for aspect ratio 0.10.
The ultrasonic response was 150% of reference level.
Cracking was induced using an arc-strike technique, with addition of small amounts of foreign matter to force the cracking. Five crack sites were prepared; one of the five did not crack. After ultrasonic examination the cracks were ground away to determine their depths. All of the cracks were less than one-half inch long. The crack dimensions and ultrasonic responses are shown in Table 2.
Table 2 Crack Responses Crack Depth Depth Response (inch) (% wall) (% of reference level)
A 0.034 2.6% < 10%, detected but not recorded B 0.071 5.4 % 32 %
C 0.097 7.3 % 32 %
D 0.106 8.0% 25 %
E O 0% 0 appendix III (III-4511) requires that flaw indications are to be recorded at any amplitude, and non-geometric and non-metallurgical indications are to be recorded if greater than 20% of reference level. All four cracks were recordable as flaw indications.
Cracks B, C, and D were also recordable as non-geometric indications. The signal-to-noise ratio was better than 20dB in all cases. These cracks are much smaller than the maximum allowable flaw depth, which is 14.6% throughwall.
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1 Dajun Song February 4,1994 Page 3 In summary: Ultrasonic procedures in accordance with Appendir HI would detect these flaws above the minimum recording level of 20% of reference level, particularly when used to investigate for cracking at the site of a known arc strike.
Please call me at (704) 547-6095 if you have any questions.
Sincerely, / _.
s /
ff ' ,f Greg Selby ,
GS:inb cc: Stan Walker Frank Ammirato Bob Stone Terrence Camilleri, BG&E Rob Pond, BG&E Jack Lance, EPRI
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