ML20076F920
| ML20076F920 | |
| Person / Time | |
|---|---|
| Site: | Vermont Yankee File:NorthStar Vermont Yankee icon.png |
| Issue date: | 06/09/1983 |
| From: | Murphy W VERMONT YANKEE NUCLEAR POWER CORP. |
| To: | Vassallo D Office of Nuclear Reactor Regulation |
| References | |
| REF-SSINS-6820 FVY-83-53, IEB-3-2, IEB-83-02, IEB-83-2, NUDOCS 8306140489 | |
| Download: ML20076F920 (3) | |
Text
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VERMONT YANKEE NUCLEAR POWER CORPORATION RD 5, Box 169, Ferry Road, Brattieboro, VT 05301 y
ENGINEERING OFFICE 1671 WORCESTER ROAD FRAMINGHAM, MASSACHUSETTS 01701 TELEPHONE 617-672-8100 FVY 83-53 2.C.2.1 June 9, 1933 United States Nuclear Regulatory Commission Washington, D. C. 20555 Attention:
Office of Nuclear Reactor Regulation Mr. Domenic B. Vassallo, Chief Operating Reactors Branch No. 2 Divisicn of Licensing
References:
(a) License No. DPR-28 (Docket No.50-27I)
(b) Letter, VYNPC to USNRC, FVY 83-50, dated June 3,1983 (c) Letter, USNRC to VYNPC, IE Bulletin 83-02, dated March 4, 1983 (d) Letter, VYNPC to USNRC, FVY 82-132, dated December 21, 1982
Subject:
IE Bulletin 83-02 Inspection Results - Supplemental Information
Dear Sir:
Reference (b) provided you with our report of findings and actions taken in response to IE Bulletin 83-02, Reference (c).
The purpose of this letter is to provide updated information regarding the results of our post-overlay weld joint inspections. Enclosure E of Reference (b) has been revised to reflect these results and is provided as an attachment to this letter.
By Reference (d), we informed you that we were monitoring the events taking place at other boiling water reactors relative to Intergranular Stress Corrosion Cracking (IGSCC), and that it was our intent to submit a revision to our Inservice Inspection Program prior to the 1983 refueling outage. The proposed revisio; became unnecessary as it would have called for a duplication of the augmented inspection program required by the Bulletin.
O och PDR I
I
U. S. Nuclear Regulatory Commission June 9, 1983 Attention:
Mr. Domenic B. Vassallo Page 2 4
We trust this information is satisfactory; however, should you have any questions, please contact us.
Very truly yours, VERMONT YANKEE NUCLEAR POWER CORPORATION
/
W.
. Murphy Vice Piesident an nager of Operations JBS/ds 2n.:losure cc:
U. S. Nuchar Regult. tory Com111 salon Region I 631 Park Avenue Kir.g of Prussia, PA 19406 Atten:
Mr. T. T. Ma rtin COMMONWEALTH OF MASSACHUSETTS)
)ss MIDDLESEX COUNTY
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Then personally appeared before me, W. P. Murphy, who, being duly sworn, did state that he is Vice President and Manager of Operations of Vermont Yankee Nuclear Power Corporation, that he is duly authorized to execute and file the foregoing request in the name and on the behalf of Vermont Yankee Nuclear Power Corporation and that the statements therein are true to the best of his knowledge and belief, sb.
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a Enclosure E i
-POST-WELD OVERLAY EXAMINATIONS l
The examinations following the weld clad repair at Vermont Yankee consisted of the following:
1.
Clad Bond Examination 2
Clad Integrity Examination 3.
Rebaseline Examination of Weld Joints The Clad Bond Examination consisted of a straight beam examination f rom the clad surface. The principle area of concern is the clad to base metal interface. A 3/8" diameter flat bottomed hole at the clad to base metal interface of a clad calibration standard was used as the reference reflector.
Scanning sensitivity was at least +6 db gain. The acceptance criteria was 50%
of the 3/8" diameter hole reference signal or any indication with an area less than the reference reflector at reference sensitivity.
This examination revealed no relevant indications.
The Clad Integrity Excmination consisted of an angle beam inspection of the clad and clad to base metal interface. The reference reflector was a 1/16" diametar side drilled hole at tie clad to base metal interface of a clad calibration standard. Acceptants criieria was any indication less than 50% of the reference reflector. No cracks, lack of penetration, or lack of fusion were allowed. No elongated indications greater than 1/4" were permitted.
'f he results did not reveal any relevant indications in the overlay or overlay tc base metal interface.
The ultiasonic examination of the base metal (rebaseline) was performed in the presence of nitrasonic noise encountered at the overlay to base metal interface.
Significant beta angle shifts were noted. The data was evaluated and recorded for comparison to the weld joint's condition during later examinaticn periods. There was no evidence of an increase in the number of flaws or size of existing flaws in the welds examined. This rebaseline examination of weld joints was performed on the overlayed pipe to safe-end joints (34, 25, 40, 31, 52), and the riser to elbow joints (29, 54, 51,18, 35, 24, 32).
Vermont Yankee has attempted to perform an angle beam, longitudinal mode inspection of the sweep-o-let to riser weld joints as a baseline examination; however, these examinations were inconclusive. Therefore, Vermont Yankee is unable to perform a baseline examination on these weld joints at this time.
Radiography was not performed as an alternate to ultrasonic testing. The radiographic process using IR-192 has not demonstrated sufficient sensitivity to IGSCC to provide reliable results.
It is further felt that the overlay will compress the indications, effectively closing them and as such providing no sensitivity to a radiographic examination.
Vermont Yankee recognizes that radiographic and ultrasonic examination techniques are currently being developed to provide greater sensitivity to IGSCC. As these techniques become qualified, they will be considered for reinspection of the overlayed weld joints, as necessary.
In addition to the volumetric examination described, a liquid penetrant examination has been performed on the final weld overlay surface condition.
The results showed ru) unacceptable indications.
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