ML20041E545
| ML20041E545 | |
| Person / Time | |
|---|---|
| Site: | Ginna, Zion, 05000000 |
| Issue date: | 02/23/1982 |
| From: | Harold Denton Office of Nuclear Reactor Regulation |
| To: | Dumelle J ILLINOIS, STATE OF |
| Shared Package | |
| ML20041E546 | List: |
| References | |
| NUDOCS 8203110063 | |
| Download: ML20041E545 (3) | |
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Dunelle, P.E.
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State of Illinois
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Dear fir. Dunelle:
Your letter to Chairman Palladino of January 27, 1982, was referred to ue for reply.
In your letter you refer to the Chairman's appearance on the "licfkil-Lehrer Report" television progran on January 26, which discussed the then recent steam generator event at the Ginna fluclear Plant, located near Rochester, New York.
Yeu express concern with regard to whether stean generator tube problens could occur at the Zion plants, question the cost of the Ginna shutdown, and suggest stean generator replacement prior to tube degradation.
As a natter of background, pressurized water reactor (PWR) steau generators have been experiencinq a variety of tube degradation problems for a number of years. flost of these problems have been associated with corrosion and/or mechanically induced danage. Corrosion and nechanically induced danage are caused by corolex interactions of water chenistry, thernal-hydraulic design, naterials selection, f abrication nethods, and operations. Various types of corrosion have af fected nost stean generators resulting in scheduled and unscheduled outages to repair or replace steam generators. The primary safety consideration regarding degraded stean generator tubes is that they retaia adequate structural integrity, without excessive leakage, over the full range of nornal operation, transient, and postulated accident conditions.
Our bases for allowing con *.inued operation of current plants is to assure that the stean generators have and retain tube integrity without excessive leakage.
To provide assurance that plants can be operating safely, the stean generators are tested initially to confirm tube integrity and plant Technical Specifications include requirenents for periodic inservice inspection of the tubes. The Technical Specifications also include operating linits on primary and secondary systen activity levels. Tubes identified to be degraded beyond the limit pecified in the plant Technical Specification must be renoved fron service by plugging. For a few plants, repair of tubes by " sleeving" has been approved W jk l
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as an acceptable alternative to plugging thereby permitting the required tubes to remain in service.
In addition, the plant Technical Specifications provide I
limits on allowable prinary to secondary leakage, beyond which the unit must be shutdown for additional inspection and repairs.
We believe that these requirements have proven effective in assuring public health and safety to date.
With regard to the Zion Station steam generators, our records show that Zion Unit I had a snall steam generator tube leak (31 gallons per day) in January 1981 and was experiencing tube leakage during January and February 1982. This Unit is now-shutdown for refueling and to inspect and repair the steam generators. No leaks have been experienced in Zion Unit 2.
Your question concerning the costs of the current Ginna shutdown cannot be determined at this time because the cause of the event is still under investi-gation and it is uncertain what inspections and repairs would be required.
Your last question concerned the periodic replacement of steam generators. As we have stated above, our basis for allowing continued operation of plants is to assure that the steam generators have and retain tube integrity without excessive leakage.
However some utilities, because of excessive shutdowns to inspect and repair steam generator tubes or when the number of tubes plugged results in inefficient operation of the plant, have replaced steam generators.
In these cases the time for replacement took about ten months and cost about seventy million dollars not including the cost of replacement power.
Therefore, the decision of when to replace steam generators rests with each utility and is based on cost / benefit factors.
I trust that the information provided by this letter is responsive to your letter.
Sincerely,
Original Siped by H. R. Denton Harold R. Denton, Director Office of Nuclear Reactor Regulation y
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