ML19309E381
| ML19309E381 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 03/24/1980 |
| From: | Mattson R Office of Nuclear Reactor Regulation |
| To: | Webb R AFFILIATION NOT ASSIGNED |
| Shared Package | |
| ML19309E382 | List: |
| References | |
| NUDOCS 8004210398 | |
| Download: ML19309E381 (1) | |
Text
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NUCLEAR REGULATORY COMMISSION 5 ',I WASHINGTON, D. C. 20555 3
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<3 Or. Richard E. Webb 2858 111 Street Toledo, Ohio 43611
Dear Mr. Webb:
Your letter to me dated February 22, 1980 asks whether the emergency core cooling systems for PWRs have been changed in any way after the TMI accident. My response is that the NRC staff has. reviewed the TMI-2 scenario and has implemented a variety of short-term requirements for pressurized water reactors, none of which can in any way be portrayed as "...a more powerful safety injection system."
As you may know, the capacity of the omergency core cooling system d'id.
not in itself influence the course of events at TMI-2; rather it was the operator's decision to throttle down on high pressure injection flow from the ECCS during critical periods that was a major contributor to the severity of the accident. Changes to emergency procedures and more thorough operator training have been required for all operating pressurized water reactors to reduce the chances of repeating such an error.
However, our evaluation of the TMI-2 accident and the lessons to be learned are continuing. Short-term requirements in a variety of areas, both design and analytical, have been specified and implemented. Addi-tionally, some long-term requirements have been identified.
It is possible that as a result of such ongoing work, further ECCS require-ments could evolve.
For example, on page VIII-4 of NUREG-0611, " Generic Evaluation of Feedwater Transients and Small Break Loss-of-Coolant Accidents in Westinghouse-Designed Operating Plants" (enclosed), we address the issue of the need for automatic tripping of reactor coolant purnps. We state that the automatic tripping may not be an ideal solution and suggest that increased safety injection flow rate may be a viable option to be considered by licensees. Also, a Task Action Plan has evolved from the TMI-2 accident which recommends further study to decrease frequency of challenges to emergency core cooling system (ECCS); improve reliability; ensure that the ECCS design basis is consistent with operational experience; reach better technical understanding of ECCS performance; and ensure that the uncertainties associated with the prediction of ECCS performance are properly treated in small break evaluations.
l Other areas potentially affecting ECCS design do exist, and will continue to be a possible outgrowth of our assessment of TMI-2 consequences. How-ever, in the context of your letter which suggests that NRC has required plant after plant to be equipped with a more powerful safety injection 8004 1o39y