ML19316A720
| ML19316A720 | |
| Person / Time | |
|---|---|
| Issue date: | 03/24/1980 |
| From: | Mattson R Office of Nuclear Reactor Regulation |
| To: | Webb R AFFILIATION NOT ASSIGNED |
| Shared Package | |
| ML19316A721 | List: |
| References | |
| NUDOCS 8005230779 | |
| Download: ML19316A720 (2) | |
Text
l 8005230 7 7 Distribution:
Central _ File..
f.RR RDG R53 RCG T. Schultze (D55-80-32)
G. Mazetis Mazetis Chron.
POR
- . J. Mattson F. Schroeder Dr. Richard E. Webb 2358 111 Street Toledo, Jhlo 43511 l
Dear P,
. Webb:
Your letter to nc R Led February 22, 1980 asks whether the cmcrgency core cooling systems for PWRs have been changed in any way after the T.'il j
accident. My response is that the DRC staff has reviewed the TMI-2 l
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 emergency core cooling system did 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.
l 6 ever, our evaluation of the TMI-2 accident and the lessons to be i
learned are continuing. Short-tenn requirements in a variety of areas, both design and analytical, have been specified and implemented. Addi-I tionally, some long-term requirements have been identified.
It is possible that as a result of such ongoing work, further ECCS require-nents could evolve. For example, on page VIII-4 of huREG-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 pumps. We state that the automatic tripping may not be an ideaf 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 l
associated with the prediction of ECCS performance are properly treated in small break evaluations.
I l
Other areas potentially affecting ECCS design do exist, and will continue V'
to be a possible outgrowth of our assessment of TMI-2 consequences. How-
-c-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 jf I
OFFICE >
SURNAME >
DATE >
NRC Form 318A (449) NRCM O2040 e........ --. =,...=vm. o..e. r i m-- m.
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Dr. Richarc E. Uebb..., E
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system (ficw or capacity), such is not the case to cate. Our enclosed evaluation of Westinghouse operating reacters is :r~idad to indicata tha iccus ci tha T::I-2 related issuas t.hich nera ---_ mtad. Also 2nclosed
!:..L?.20-0573, "T:::-2 Las. cas Learna; Tas:c Forca ;:
a.,eport and W r:-
Tara Recc:.=encaticas," which specifias ;:naric ragt. ire. cnts for all 1
pressurized water reactors.
I trust the above information adequately responos to your inquiry.
Sincerely.
Oriri al signed by Roger J.1,13ttson Roger J. !!attson, Director Divisica of Systems Safety Office of Nuclear Reactor Regulation
Enclosures:
As stated cc:
R. Denise l
T. Novak i
S. Israel e
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