1CAN128207, Application for Amend to License DPR-51,proposing Change to Tech Spec 4.18 Re Steam Generator Tubing Surveillance to Assure That Known Problem Areas Are Adequately Inspected. Class III Amend Fee Encl
| ML20079J659 | |
| Person / Time | |
|---|---|
| Site: | Arkansas Nuclear  |
| Issue date: | 12/17/1982 |
| From: | Jeffery Griffin ARKANSAS POWER & LIGHT CO. |
| To: | Stolz J Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML20079J661 | List: |
| References | |
| 1CAN128207, NUDOCS 8212280307 | |
| Download: ML20079J659 (4) | |
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ARKANSAS POWER & LIGHT COMPANY FIRST NATIONAL BUILDING /P.O. BOX 551/LITTLE ROCK. ARKANSAS 72203/t501) 371-7901 December 17, 1982 JOHN M. GRIFFIN Vice President Nuclear Operations 1CAN128207 Director of Nuclear Reactor Regulation ATTN:
fir. J. F. Stolz, Chief Operating Reactors Branch #4 Division of Licensing U. S. Nuclear Regulatory Commission Washington, DC 20555
SUBJECT:
Arkansas Nuclear One - Unit 1 Docket No. 50-313 License No. DPR-51 Proposed Change to Tech Spec 4.18 Steam Generator Tubing Surveillance Gentlemen:
This letter transmits a proposed change to the Arkansas Nuclear One - Unit 1 (ANO-1) Technical Specification 4.18 relative to the surveillance of steam generator tubes.
As discussed below we feel this change is appropriate in light of experience gained to date from steam generator tube inspections currently being performed during the ANO-1 fifth refueling outage.
The present Technical Specifications governing inservice inspection of steam generator tubes requires an inspection of at least three percent of the tut es in each steam generator.
In addition, two special interest areas are defined. These areas consist of the tubes on the bundle periphery with drilled holes at the fifteenth support plate and those tubes in the first three rows on either side of the inspection lane.
Although these areas are subject to increased inspections, defects located in the defined areas do not result in increased general inspection requirements, provided that all tubes in the special interest areas are inspected.
Experience during the current refueling outage inservice inspections on the "B" steam generator indicates a need to define an additional special interest area on either side of the presently defined lane area and near the bundle periphery.
Modifying the existing Technical Specifications to include this new area will assure that the problem area is thoroughly inspected, but will preclude unnecessary inspections in areas of the steam generator where there is no indication of potential problems.
This will also prevent unnecessary personnel radiation exposure associated with such inspections.
We believe this Technical Specification change is appropriate for the reasons discussed below.
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Mr. J. F. Stolz 2
December 17, 1982 Operating experience has indicated that B&W once-through steam generators can be subject to tube degradation in tubes directly adjacent to the open inspection lane at the fifteenth tube support plate and upper tubesheet regions.
Contaminants transported by moisture up the open lane are believed to be a major contributor to tube degradation in this area.
First of a kind
'asts at a B&W operating plant in 1973 indicated moisture in the top tube span at power levels above 85%.
It is judged that at full power, a substantial amount of moisture reaches the upper tubesheet.
The moisture is apparently due to the high axial velocity up the open lane combined with less available heat transfer surface.
In the top span, the relatively high radial velocities have played a role in a number of past tube failures in the lane region.
The first 9 tube leaks in B&W plants were in tubes directly adjacent to the open lane.
In 1977, the first off-lane leak occurred.
This tube was on the periphery of the tube bundle in the second row from the open lane.
The failures are believed to have been initiated by corrosion and propagatM by fatigue.
Because of this pattern of tube degradation, the lane region was defined as a special region consisting of three tube rows on each side of the open lane. This definition encompassed tubes which were subjected to the contaminants transported by moisture and those tubes exposed to higher than average bundle velocities.
The vast majority of tubes with reportable eddy current indications detected during the present inspection of the ANO-1 "B" steam generator have been concentrated in and around peripheral " lane tubes".
In addition, the eddy current indications with few exceptions are within the upper tubesheet which supports a failure hypothesis based on the transport of contaminants up the lane and the concentration of an aggressive chemical species within the tube sheet crevice.
Because this apparent degradation pattern is not encompassed in the originally defined lane region, it therefore appears prudent to add an additional special region as defined in the proposed Technical Specification. As proposed, the Technical Specification will assure that problem areas associated with the lane region are properly bounded, but will not require unnecessary extensive inspections in other areas of the steam generator.
In addition, the proposed Technical Specification will permit inspections in the special interest areas to be limited to portions of the tubes where experience has indicated the tube degradation to be localized.
Since the defined special interest areas are based on an increased probability of detecting tube degradation based on past experience, limiting the inspection of tubes in ruch areas to those portions of the tubes where degradation is expected u appropriate.
In summary we feel the proposed Technical Specification will provide assurance that known problem areas are adequately inspected.
This change will not decrease the number of tubes examined during the general inspection, but will preclude unnecessary inspections in areas of the steam generator where there are no potential problems and prevent unnecessary personnel radiation exposure which would result from such inspections. We have been keeping the NRC staff informed of the progress and results of
Mr. J. F. Stolz 3
December 17, 1982 these inspections by phone calls and a meeting on December 20 1982, in Bethesda. We will continue to provide information as it is obtained and make additional formal submittals as may be required. As required by our Technical Specifications, a report describing the results of this inspection will be submitted following their completion.
In accordance with the previsions of 10CFR170 we have determined this to be a class III change and our check for $4,000 is enclosed.
Very truly yours, U
5 John M. Griffi JMG:DH:rd Attachments I
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STATE OF ARKANSAS
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SS COUNTY OF PULASKI
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I, John M. Griffin, being duly sworn, subscribe to and say that I am Vice President, Nuclear Operations for Arkansas Power & Light Company; that I have full authority to execute this oath; that I have read the document numbered ICAN128297 and know the contents thereof; and that to the best of my knowledge, information and belief the statements in it are true.
S th-John M. Gri SUBSCRIBED AND SWORN T0 before me, a Notary Public in and for the County and State above named, this /N day of 1982.
Notary Public My Commission Expires:
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