ML25167A206
| ML25167A206 | |
| Person / Time | |
|---|---|
| Issue date: | 08/14/1984 |
| From: | Ebersole J Advisory Committee on Reactor Safeguards |
| To: | Dircks W NRC/EDO |
| References | |
| Download: ML25167A206 (1) | |
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UNITED STATES NUCLEAR REGULATORY COMMISSION ADVISORY COMMITTEE ON REACTOR SAFEGUARDS WASHINGTON, D. C. 20555 August 14, 1984 Mr. killiam J. Dircks Executive Director for Operations U. S. Nuclear Regulatory Conrnission Washington, DC 20555
Dear Mr. Dircks:
SUBJECT:
ACRS COMMENTS ON TASK ACTION PLAN A-45, 11SHUTDOWN DECAY HEAT REMOVAL REQUIREMENTS" During its 29'nd meeting, August 9-11, 1984, the Advisory Conrnittee on Reactor Safeguards received a status report by the NRC Staff and its contractor on the Task Action Plan {TAP) for resolution of USI A-45, "Shutdown uecay Heat Removal Requirements."
The Subconrnittee on Decay Heat Removal Systems had considered the status of the TAP during a meeting on June 5, 1984.
Th1s subject has been reviewed by the Convni ttee and the Decay Heat Remova 1 Systems Subcommittee on severa 1 other occasions since inception of the program.
The objectives of TAP A-45 have been described as an evaluation of the decay heat removal systems in current nuclear power plants to determine their adequacy and to evaluate the feasibility of alternative systems or methods, to determine the cos ts and benefits of the most promising alternatives, and finally, to develop a plan for implementing any new licensing requirements.
The Task is complicated by the great variety and complexity ot decay heat removal systems in existing plants.
We believe the issue being addressed by TAP A-45 is of major signifi-cance to the safety of nuclear power plants and should receive high priority in the allocation of agency resources.
While the program appears to us to be addressing the major issues, and progress toward resolution is evident, we have several comments.
l)
Because there is evidence that each nuclear power plant in the U.S.
may have a nearly unique decay heat removal system and associated support systems, it may not be possible to develop a generic set of requirements, except at an abstract level, e.g., numerical re-liability and cost goals.
The present program is attempting to agglomerate all existing plants into a manageable number of groups, so that a representative system improvement can be defined for each.
The NRC Staff should attempt to determine, early in the remainder of the program, whether this grouping to form generic types will ultimately be feasible. If not, an alternative approach must be developed in a timely manner.
- 2)
We endorse attempts to make quantitative estimates of costs and benefits of proposed improvements.
However, we caution that such 2028
Mr. William August 14, 1984 estimate~ can be used only as guides to judgment and should not be the sole basis tor decisions.
Serious consideration should be given to the way in which these estimates are developed.
Unfor-tunately, for lack of other guidance, the NRC Staff has been evaluating health benefits by carrying the impact of any proposed change in a plant to the end consequence of human radiation ex-posure, and then using the ALARA standard of $1000/man-rem. This kind of bottom-lining reflects the weakest use of probabilistic risk assessment, ana may, in the end, damage the credibility of an entire program.
- 3)
We endorse the effort to apportion quantitative reliability goals among plant subsystems.
We believe an attempt to be explicit can lead to a better understanding of the safety importance of the various systems and components ana therefore holds promise for cost-effective improvements.
We t1a ve some concern that the too-li tera 1 deve 1 opment of these reliability values from quantitative guidance of the present NRC trial safety goal may be burdening the A-45 program with the many ramifications ot the safety goal issue.
This quantitative use of the safety goal, or even of the reliability goals, se~ms to be an important policy decision.
lri'e suggest that, if such quantitative goals are to be important to resolution of uSl A-45, some means be developed to have this policy thoroughly reviewed by the NRC on an expeditious basis.
- 4)
The eight plants being studied ir, oetail were judged by a qualita-tive screening method to be among those having the greatest weak-nesses in existing decay heat removal systems.
We think it is appropriate to concentrate further study on this end of the spec-trum, but sug9est that one or two plants from the middle or the other end of the spectrum should be included.
The qualitative screening method, while seemingly appropriate, was judgmental and partly subjective. A study of a few plants outside of those chosen would provide additional confidence in the screening process.
- 5)
In developing the accident scenarios, equipment environmental conditions should be considered which place demands on systems and components that might be subjected to hot water, steam, or ra-diation.
This is especially important if feed and bleed is con-sidered an effective mear,s for removing decay heat.
We urge a high level of management attention to this important program and request that the Committee continue to be kept fully informed.
~erely,
~
~. If..,,~
Jesse C. Ebersole Chairman 2029/2030