ML19308A439
| ML19308A439 | |
| 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 | |
| ML19308A440 | List: |
| References | |
| NUDOCS 7910170452 | |
| Download: ML19308A439 (2) | |
Text
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UNITED STATES s,
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SEP 2 71979 Mr. J. R. Wallis, President-Elect Section of Hydrology knerican 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 Flood estima tes. 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 Comission staff to develcp 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 Nuclear 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 comunity, that the Probable Maximum Flood thus 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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=the-operators"of' the plant.have before regard: to your supplementa.l. concernsyg g
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plant.well in advance of' the. flood. The f sland -itself is founded on erosion. X ~
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' MT d-Q As wastmentioned prevfously' in MrpDenton'sEletter we do not'use the ^~ U D
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Water Resources Council Bulletin 17 procedures to estimate. extreme flood:
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events. Thus, we cannot provide the relief which you to seek with regard to this procedure. We recomend that you take your concerns to the professional comunity to seek resolution.
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i We are unable to provide the information you requested for your future ~
research. That infomation has-not been compiled. The infomatio'n is -
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i..W. N. It follo..w.s :tha "si. ncef.ay Protiable/,Mhat;tts: use"at Three. Mile' rsla MaximumM.lo.od.wreprese.nts?an accept.a 9~ u J
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' provides 'adequateJafety ma@ ins.. Un'a-ll ~ cases?at:Tiir
' ' Mile Island,.whethe the protection: beinffered. by' the levees 'oF by :
~to building-deshn,: thei plant acconnodate's; +.he :Tff y" h 57 features-incorporatedu i.
. Probable Maximum Flood.
~ 1.6 million-c.ibici feet per :econd.. In additionV.
Wyb the plant.is designed to comodate the effects _of wind generated wai/e's(.
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coincident' with that) peak.
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before them Technical Specifications which O e ulcimate event at the plant should t require themTtortake. flo'od pro
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Probable Maximum Flood occur-.The-land itself is founded up on erosion M D-resistant. bedrock.
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s riprap on the levees keyed into the ri r bottom in a manner consistent with good engineering practice.
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As was mentioned previously in Mr. Denton's tter, we do not use the pi Water Resources Council Bulletin 17 procedures-to estimate extreme flood 7@f.
events. Thus, we.cannot provide the relief whic you seem to seek with
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BM regard to this procedure. We. would recomend str gly that you take "
- , #p M your concerns to the professional comunity to seek solution of your apparent dissatisfaction.
Ne are unable to provide the information you requested f your future r
research. That information has not been compiled. The in orr.ation is i
available to you, through the Public Document Room on an ad oc basis for each reactor site.
Sincerely, 4
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~ Daniel R. Muller, Acting Director -
.# 3W' Division of~ Site Saf'ty and-
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25F FROM OATE OF DocuwtNT -
DATE mECtevers NO i
g J. R. Wallis 8/21/79 NRR-3220 i
LTR utMO R EPOR Y OTwER X
TO OR'4 CC-OTHEn-I H. R. Denton
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Post OFFICE FILE CODE REG N1 DESCRIPTION iMuse Se Unces.sefeel REFERRED TO Op3,
NECElvf D ev OATE DISCUSSES NRE 790518-LTR RE MPF
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ESTIMATES, EXTREME QUANTILE EXTIMATES D. Muller 9/127 j' BY NRC PROCEDURES, TMI LEVEE DESIGN t8 g
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& FUIURE NRC RESEARCH INTO FLOOD RISKS Copies To:
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0.41 A,,
EaO7 ANUCLEAR FLANI Sut,5, RtQUE5I5 1Nt 0 H. R. Denton
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RE NUCLEAR PLANTS BUILT ON FLOOD PLA21 E. G. Case OF RIVERS H. Berkow/W. Russe L1 t
F. Schroeder D. Vassallo t
D. Eisanhut I
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yellow control ticket to ?.C' Grof t when actioncc:aleted.
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4 REGMLAVORY INFORMATION DISTRIBUTION SYSTEP (RIDS)
ACCESSION NBR 7908280677 00C.DATE: 79/08/21 NOTARIZED: NO DOCKET
- FACIL'-
AUTH.NAME AUTH0R AFFILIATION WALLIS,J.R.
American Geophysical Union RECIP.NAME RECIPIENT AFFILIATION DENTON,H4R.
Uffice of' Nuclear Reactor Regulation
SUBJECT:
Discusses NRC 790518 Itr ce MPF estimates,ewtreme quantile estimates ey nRC procecures,TMI levee ces19F & future NRC researen into flood risks of nuclear plant sites. Requests into re nuclear plants ouilt on flood plain of rivers.
DISTRIBUTION CODE: XE01S LUPIES NECEIVED LTR.l. ENCL Q.
SIZE _2......
TITLE: Exec. C o r r e sp on rie n c e (No specific Dkt. Trans. to Depto /
NOTES:..._______.._______......,______
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i August 21,1979 i
Harold R. Denton s
Director
'i Office of Nuclear Regulation Nuclear Regulatory Commission Malomic Building 1717 H Street NW Washington, D.C. 20555 i
Dear Mr. Denton,
You evidently read my letter of May 18th addressed to Mr. Hendrie very carefully, but judging from your reply we have failed to communicate. It appears that we are philosophically poles apart.
Your letter is couched in terms of certainties, that is of probabilities of one or zero, (P-1, or
~
P=0), whereas in contrast I prefer to think of rare events having probabilities greater than zero but less than one. In particular, I believe that there are very few, (P > 0), reliable deterministic l
models in geophysics, and that MPF estimates are not a members 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 will be overtopped, (P-1). I would prefer to give this eventuality a high probability, (P near 1), as the recurrence 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 cfs, not the 1.6 million cfs that I was given to believe. But in any case we are almost in agreement, when you state that "...failur, of the levees is anticipated.. ", whereas I d DUPLICATE DOCUMENT JZference amounts to a quibble.
Entire document previously entered into system under:
ANO h WD$O4 77 No. of pages:
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UNITED STATES y7 j
NU LEAR REGULATORY COMMISSION
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WASHINGTo N, D. C. 20555 8,
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JUL 2 61979
-Mr. J. R. Wallis-President-Elect Section of Hydrology l
American Geophysical Union c/o P.O. Box 218 Yorktown Heights, NY 10598
Dear Mr. Wallis:
Your letter of May 18, 1979 to Chairman Hendrie has been referred to me for l
response.
During the licensing reviews of the site the staff shared your concern over site flooding.
As I interpret your letter, your principal concerns I
are (1) inappropriate use of statistical estimates to assess flood risks at nuclear power facilities, (2) the " flexibility" of the MPF estimate at Three Mile Island, (3) whether we are aware of how the flood estimates are developed, and (4) why an alternate site was not chosen.
I appreciate the opportunity to consider and respond to your comments, and I'm providing the following background information and explanations.
While we do not concur with your characterization of the Water Resources Council's flood frequency estimating technique, we agree that contemporary statistical techniques are not appropriate for estimating rare flood events because (1) available streamflow records are short-term and may not be repre-sentative of the extreme flood producing potential of a watershed; and (2) we can establish no rational basis for the selection of confidence levels to minimize the residual error in estimates of severe flood event magnitude or likelihood.
These shortcomings preclude the quantification of flood risks from extreme events in any meaningful way.
The deterministic approach which we use also prohibits useful quantification of risk.
(Our approach is discussed below.)
Because we view the quantification of risk as a desirable goal, NRC has initiated a research program towards this end.
To date, the results are not promising.
All this does not imply, however, that the risk of flooding is high.
It simply means that the probability of occurrence while small is, in your words, unknowable.
The. Probable Maximum Flood (PMF) estimate, which you term the MPF, did not change as a result of Tropical Storm Agnes.
The applicant based the original peak flood discharge estimate of 1.1 million cubic feet per second (cfs) on a I
preliminary and unapproved Corps of En
- h sl nd flood j
protection levee system was designed f i
dently reviewed the PMF estimate and q time, the Chief of Engineers, Corps of DUPLICATE DOCUMENT the original Baltimore District 1.1 mil l
concluded that the Susquehanna River PF Entire document previously entered I
be about 1.6 million cfs.
The NRC sta
- nto system under:
and concurred.
g No. of pages:
1
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