ML19308A452
| ML19308A452 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 09/27/1979 |
| From: | Muller D Office of Nuclear Reactor Regulation |
| To: | Wallis J AMERICAN GEOPHYSICAL UNION |
| Shared Package | |
| ML19308A451 | List: |
| References | |
| NUDOCS 7910190216 | |
| Download: ML19308A452 (1) | |
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SEP 2 7 1979 Mr. J. R. Wallis, President-Elect Section of Hydrology American Geophysical Union c/o P. O. Box 218 Yorktown, fi. Y.
10598
Dear Mr. Wallis:
Your letter of August 21, 1979, to Harold R. Denton has been referred to me for response.
I appreciate the opportunity to speak to your continued concerns about the Nuclear Regulatory Commission's criteria for the flood protection of Three Mile Island and to other concerns related to water resources.
Your current concerns address the effects of flooding at Three Mile Island, the underlying philosophy and bases for Probable Maximum Flood estimates, and the Water Resources Council's flood frequency procedures.
Finally, you request information for research in the area of flood prediction.
I will address the concerns in a somewhat different order than you raised them in order that the responses may be tied together.
You have raised a number of issues with regard to the Probable Maximum Fiaod estimates.
These include the historical naming of the event through your concerns over whether or not the event is deterministically or statistically derived.
The procedures used by the Nuclear Regulatory Commission staff to develop the Probable Maximum Flood estimates, are consistent with those used by Federal water resource agencies as well as numerous private organizations.
Our procedures are codified in Regulatory Guide 1.59, " Design Basis Floods for fluclear Power Plants" and the American National Standard-N170, " Standards for Determining Design Basis Flooding at Power Reactor Sites."
It is our position, which is supported by the majority of the water resources community, that the Probable Maximum Flood thus
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defined provides a conservative upperbound estimate to the flooding potential of a given river basin.
As such, it is appropriate for use in evaluating flood impacts on nuclear power plants.
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SEP 2 7 1979 Mr.d.R.Wallis It follows that since a Probable Maximum Flood represents an acceptable upperbound on the flood estimate, its use at Three Mile Island to design the flood protection provides adequate safety margins.
In all cases at Three Mile Island, whether the protection is offered by the levees, or by features incorporated into building design, the plant accommodates the Probable Maximum Flood of 1.6 million cubic feet per second.
In addition, the plant is designed to accommodate the effects of wind generated waves coincident with that peak flood.
With regard to your supplemental concerns, the operators of the plant have before them Technical Specifications which require them to take protective actions which assure the safety of the plant well in advance of the flood. The island itself is founded on erosion resistant bedrock.
In addition, the reactor facilities are protected by riprap on the levees keyed into the river bottom in a manner consistent with good engineering practice.
As was mentioned previously in Mr. Denton's letter, we do not use the Water Resources Council Bulletin 17 procedures to estimate extreme flood events. Thus, we cannot provide the relief which you to seek with regard to this procedure.
We recommend that you take your concerns to the professional community to seek resolution.
We are unable to provide the information you requested for your future research.
That information has not been compiled.
The information is available to you, through the Public Document Room on an ad hoc basis for each reactor site.
Should you have any questions concerning this letter you may wish to contact Mr. L. G. Hulman, Chief, Hydrology-Meteorology Branch (492-7288).
Sincerely, tUI
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g Daniel R. Muller, Acting Director Division of Site Safety and Environmental. Analysis Office of Nuclear Reactor Regulation 2219 551
August 21. 2-Harold R. Denton Director Office of Nuclear Regulation Nuclear Regulatory Commission Malomic Building 1717 H Street NW Washington, D.C. 20555
Dear Mr. Denton,
You evidently read tny letter of May 18th addressed to Mr. Hendrie very carefu from your reply we have failed to communicate. It appears that we are philoso Your letter is couched in terms of certainties, that is'of probabilities of one or zero, P=0),,vhereas in contrast I prefer to think of rare events having probabilities greate less than one. In particular, I believe that there are very few, (P > 0), reliable deter models in geophysics, and that MPF estimates are not a me65ers of this set.
In this letter I shall reiterate and amplify my previous concerns.
Three Mile Island, (3MI)
You state that the NRC anticipates that the levee protecting the 3MI site w (P= 1). I would prefer to give this eventuality a high pr96 ability, (P near 1), as the recur interval of the flood necessary to overtop the levee, is not particularly extreme
. By the way it appears from your letter that overtopping would occur at 1.1 million efs, not the 1.6 m I was given to believe. But in any case we are almost in agreement, when yo of the levees is anticipated.... ", whereas I define the event as one with a high p difference amounts to a gitibble.
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