ML19309G453
| ML19309G453 | |
| Person / Time | |
|---|---|
| Issue date: | 04/10/1980 |
| From: | NRC COMMISSION (OCM) |
| To: | |
| Shared Package | |
| ML19309G451 | List: |
| References | |
| SECY-79-300, NUDOCS 8005060331 | |
| Download: ML19309G453 (66) | |
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UNITED STATE 5 N UCLE AR REG UL ATO RY COMMISSION l
In the matter of:
BRIEFING ON INFORMATION REPORT SECY-79-300 l
I Place: Bachesda, Md.
Date:
April 10, 1980 Pages:
1 - 50 INTERNATIONAL VtmeATsw Raposmots. INC.
- 430 SOUTH CAPITOL STREET. 5.W. SUITE 107 WASHINGTON D. C. 20001 3 1 484-35 0
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I UNITED STATES OF AMERICA l
NUCLEAR REGULATORY COMMISSION l
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In the matter of:
BRIEFING ON INFORMATION REPORT :
I SECY-79-300 i
I 3
-_------x 9
IO Room 550, East-West Towers, II Bethesda, Maryland t
Thursday, April 10, 1980 i
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1:
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is The Comission met, pursuant to notice, for tJ r
presentation of the above-encicled matter, at 2:00 p.m.,
ts John F. Ahearne, Chairman of the Comission, presiding.
I' l
BEFORE:
- s i
JOHN F. AHEARNE, Chairman of the Comission is i
PETER A. BRADFORD, Comissioner Oc VICTOR GILINSKY, Comissioner
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CHAIRMAN AHEARNE:
This afternoon is a Bethesda 7
meeting of the NRC, and we have several items to cover this 2
afternoon.
Under the assumption that some other commissioners 4
i i will be here at a later point, we will get to an 3
1 6
affirmation session.
The two main items are two items that 7
were presented by standards.
And the-first is a briefing 8
on the information report called SECY-79-300.
I 7
I've asked for this more from the standpoint that 10 there are a number of seismic issues that are around in l
il several of the cases before us, and also as an issue that j
i I:
has come up in some matters relating to siting policy.
l 13 But the Commission in its budget decision last year did j
U defer formal staff resources ceing applied to it.
We did t
have a very large Commission paper presented to us approxi-f4 mately a year ago, and I thought it would be certainly useful' 17 i
for me, and I hope for the other people in NRC, to attemot is I
ro get some summary of the informacion.
And I gather that's.'
19 what you will be providing this afternoon for us.
- D Bill, did you want to make any opening comments?
i
- 1 MR. DIRCKS:
No, nothing.
l
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l MR. MINAGUE:
Thank you, Mr. Chairman.
As you l
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said, the purpose of this briefing is to provide a summary
- A for the Commission of some of the seismic and geologic issues.
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i that were identified in the information report SECY-79-300, l
which was sent up to the Commission about a year ago, and on i i
3 which serves no current significant staff effort.
I'm accompanied today, so we're prepared, however l
4 i
the discussion goes, wherever it goes, by Mr. Dave Budge, j
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4 who is here as a consultant, but in a orevious incarnation he.
7 was a member of the staff of both NRI and Standard.
1 I'm also accompanied by Bob Jackson, chief of 9
the Geosciences Branch of NRI; and Franz Shauer, who's to chief of the Civil Engineering Branch.
So I think we're i
well prepared to go into detail on any specific point that 12 tne Commission wants to explore further, although I do plan 33 to handle most of the briefing myself.
I' The SECY paper referred to summarizes a joint effort between NRR and SD, aimed at reassessing Appendix A, l
14 part 100.
It was a very broad based reassessment; that is, 17 I
it involved a very extensive staff review, solicitation of la i
public comment to which there was a great deal of response, i
19 i
review at the ACRS, and review by the ACRS and staff
- o consultants.
l
- 1 1
As a result of this, we were able in this informa-
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tion paper to really lay out and clarify some of the issues t
and problems that had arisen over the years in the use of
- 4 Appendix A.
And the report -- when the decision was made i
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not to pursue further at this time was given very, very wide i
t distribution.
And I think that's helped a great deal to t
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at least frame a common underctanding of some of the issues, 3
1 l and clear the air on some of the problems.
4 In the briefing I'm going to stress the 3
l technical rather than the procedural issues that the report l
i raises because I felt that was the primary interest of l the Commission.
And among the technical issues I'll stress 3
- the seismic and geologic issues rather than engineering 9
i 10
- issues, because the main thrust of Appendix A and the main l
i 3
thrust of the report was seismic and geologic.
I'm going to begin by describing some of the l
f 13 background on the development of Appendix A, because I l
14
- ,think if you understand the background, the way some of 13 these issues arose becomes much clearer.
The initiating 14 event that led to the development of Appendix A was concern 17 about siting problems on a number of sites in California, 18 many of which were ultimately rejected Bodega Bay, 19 h San Hanofray, Malibu, Bolsa Island.
Although eastern sites
'O were considered in the review, the general perception at I
I 21 the time was that the big issues were not really concerned with eastern sites.
So that right from the beginning there U
was an orientation in the development of Appendix A for l
- 4 a California, and California geology, and questions of what l
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- f were then called active faults.
i The technical foundation for the regulation was
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laid in late 1960's.
Again, this is a very imcortant point, 3
because that says that it really relates to the stata of the 4
art in the 1950's, the then current understanding of geolo-l 2
gic and seismic issues, the exploration techniques that were f 0
available, the quality of inscrumentation, and so on.
l l
In developing the crit,eria there was major input from the U.S. Geological Survey, both here and in Denver, and also the people at Menlo Park and San Francisco
- g area, as well as the, what was then the U.S. Coast and Geodetic Survey.
At least that part of it has been gg assimilated into,U.S.G.S.
Plus a very extensive review l
14 by the public and by a number of professionals.
In fact, i
13 the seismic and geologic professionals that participated in i
14 the development of this criteria would really read like i
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17 a who's who.
18 The criteria began to be used, or the underlying 19 thinking began to be used in 1969 with the provocation of l
20 the March, 1969 addition to the criteria.
And in a very j
21
' real sense, that, more or less, closed the books in terms l
l of further development and incorporation of state of the art,
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although the goal was to not publish for comment until '71,
- s and not publish as an effective rule until 1973.
Most of the.
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changes that occurred between the March,1969 draft which I
was used by the Staff and the final version were relatively minor.
So what you have here is a regulation that funda-3 mentally was developed in the late '60's.
4 Particularly important points that I wanted to I
I really red-flag in the development of it was, first, i
6 i
underlying the perception of the late '60's was the presump-7 r
- tion that seismic events of significance could clearly 8
be correlated with geological structures.
There was I
g not any real recognition that the -- that this correlation to j
might, in fact, in some cases be quite difficult.
i The second mv.c thing that needs to be recognized j i
is the almost total lack of strong motion records from real earthquakes.'
There were a few records available in I
ts i
specific geological environments, but there was not any i
extensive data base on this.
34 g.
And last, the concept of plate-tectonics, which i
is has sense achieved much wider acceptance, was not generally l
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accepted at that time within the geologic profession, at 3
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- o least not well enough accepted to use as the basis for t
21 regulation.
So even when the regulation was issued, there were already some inherent presumptions ahead.
Because before the regulation was issued the
'A geologic review was very much a matter of looking at the
'l seismological record, there was a bit of an over-corrective u
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emphasis in the regulation on structural geology and the i
! importance of structural geology.
And I'll say more about 1
l that later as I go on.
2 Next slide.
In recent years the use of Appendix A j
4 l
has caused a very large number of problems in the l
licensing process, indicating a need for re-evaluation.
f I've summarized on this view graph the sources of some of 7
these needs.
The first two speak to changes in the earth i sciences.
During that period of ten years, there were 9
to a number of major improvements in geophysical techniques, the use of the energy pulse method for mapping of sub-11 t;
surface geologic structure, the development of computer l
I 13 enhancement techniques to assist the interpretation of l
14 the kind of data'that's attained by these geophysical t
13 measurements, techniques of studying crystal warping and i
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! other ways of assessing stress accumulation.
There's been also in that same period enormous 7
i I3 expansion -- it's hard to exaggerate it in the measurement l
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- data base of earthquake data.
For example when Appendix A f
U was developed, there were no strong motion seismographs at l
anywhere on the eastern United States.
Not only no l
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I records.
There were no strong motion seismographs.
Since then, partly because all reactors are required to have strong l 1
- 4 motion seAsmographs, because other networks have been put in, and because of a lot of concern about the detection of
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t and because--I should add a major one, the building codes I
in some areas, like in Los Angeles, require the installation 3
i of strong motion seismographs in tall buildings.
As a 4
result of this, in the last ten years there's just been a A
flood of reccrds of real earthquakes, measured records of 4
i earthquake response.
7 CHAIRMAN AHEARME:
But,that increase in date base has been, therefore, current data.
It's not some mechanism to find old records, for instance.
gg MR. MINAGUE:
No, that's right.
There were no 1:
old records.
I should make that clear.
I'm really 1
distinguishing i,nstrumental records, such as you get with I
strong motion seismograph. And of course, che kind of ta t
IJ records from human observation of earthquakes, the data 14 base of past years, the large part of that is human observa-t 17 tion, damaged records, and reports of that type in which i
la intensity is inferred.
And much of the seismological i
19 l data base is historic in that sense.
What I'm talking about !
U with strong motion records is instrumental measurements.
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And similarly, the seismograph systems that were
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put in because of the bcmb test question, if given a good data base on distant earthquakes.
A strong motion
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accalograph, of course, measures much closer to the earth.
2 CHAIRMAN AHEARNE:
Yes.
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MR. MINAGUE:
In that same context, the world-I
' wide recognition of the importance of this data, and the I
degree of international cooperation in exchanging records 2
of this type has again just skyrocketed.
They may net have
- the name exactly right.
There's a group calle d the International Earthquake Engineering Association, or t
something like that, and they've certainly spearheaded the 7
f creation of a lot of data exchanged on this.
And last, the concept of plate < tectonics are becoming better under-to
- stood, and they've achieved wider acceptance.
So I think 11 there's been a big improvement in the utility practices t:
and site exploration related to the seismic review of sites, is l
You ad,d all that together and you've had a la tremendous advance in the state of the art.
l i3 The third item on this speaks to geoscience s
to issues which were not foreseen.
And certainly the prolifera-i i
I7 tion of technological advancas wasn't foreseen, and because l
l 18 l of that the criteria -- and this maybe reflects the problem l
1 19 when you put that kind of stuff into a regulation -- there's !
l
.O not enough latitude in the criteria to. fold in the new i
l techniques, new understanding, and new approaches.
The i
wording tends to lock in on an approach that --
CHAIRMAN AHEARNE:
I guess I'm not following you,
- 4 Bob.
What kind of a gaoscience issue has arisen?
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MR. MINAGUE:
Well, I give you -- it's an example IsrFWuumam Vguest9an h %
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really just chosen at random.
No, I'm sorry.
Let me -- becadse t
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it will track my briefing.
I'll give you the next item.
I The tectonic province concept is a very, very good l
3 i example of this.
The tectonic province concept was stuck 4
in Appendix A as an afterthought.
It viasn't foreseen that S
this would become a major common issue among sites.
- Now, t
6 i
when you go to a assess that issue what you're really looking 7
l at is a process of looking at a past block of geologic data about some region of the country -- data on lithography, old geology, recent geology, et cetera, with a lot of
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[ seismic material.
The idea of really sitting down and 11 g.
trying to categorize a province with some sort of a mixed I
interpretation o,f structural geology and seismology really
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l ta isn' t spcken to in the criteria.
In other words, the way l
I 14 that they' re written you could infer, but you shouldn't 1
3 14 really look at the seismic record.
You look at the totality 17 of geology, and you don't make any selection of what's old ta and not terribly relevant, and what's recent and is quite i
19 relevant.
You don't assess it in terms of the seismic i
j i
"U record.
You just look at it in terms of the total geologicali 21 picture, and you define provinces that way.
This is a case -- the wording in the criteria --
i the wording is on a later slide -- appears to imply that you j
4 don't take tectonics into account.
Seismicity, I'm sorry.
- J Another example one might give, I think the questions i=v.%%
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s relating to the better understanding that arises from the I
l strong motion records, which is built more and more a data I
base on which you could develop site-specific response 2
i factor, although not precluded by the regulation, this 4
wasn't really foreseen as the way things would go.
The maia
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thrust of the regulation is the presumption you use a I
smooth response spectrum that just applies to all sites.
7 j And in fact, over the years the data base has been s
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' expanding rapidly and the analysis techniques that would 9
permit you to develop site-specific response, and so on.
11
. I could give other examples, but that's basically the point.
CHAIRMAN AHEARNE:
Could I have a couple of I
i others?
i 13 i
MR. MINAGUE:
Another one I think would be the g,
is question of looking at offshore geology, although people
- 4 have kind of done this in cases.
All Appendix A really I
says you should do is to make some effort to identify i
is and categorize offshore faults.
In fact. the techniques, l
19 l the geophysical techniques for exploring offshore faults, 1
M including great depth, and using somenof the techniques l
21 that the oil companies have developed, and interpreting f
i l
and evaluating this data to develope a true picture in U
three dimensions of structural geology, and the relationship i I'
of faults to each other; the capability, the present state o f the art, is far beyond what was foreseen when Appendix A tw=mx e p eadwrm flWWF. E e. StarPE 'er g
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amer.%c was drafted.
People have done that -- a lot of the things I've touched on here have been done by the licensing i
I reviewers, and have been considered.
I'm not trying to l
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2 suggest that nobody's paid any attention to the developments in the state of the art.
But what I am trying to suggest 3
is that the wording of the criteria was such that the i
5 appropriateness of using this stuff and how they used it was 7
what caused a lot of problems for the staff.
t
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Now, another point that I should mention before I 9
leave this area; there are areas of the country where the
!Q geology was not really considered that well in the 11 development of the criteria.
This might also be relevant 1:
to the question you just raised.
Let me give some M
specific examples.
Volcanism, which is a problem in the i
northwest, was explicitely not considered.
It was left U
to be handled case by case.
There was very little real te l
attention given to the great basin, to the Rocky Mountains, l
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to the Texas coast, because these were felt to be areas l
18 that were not likely to be reactor sites, and there's a 19 real problem in dealing with a country as large and
,c diverse as this, to come out with criteria that apply to f
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just any place in the country you want it to.
The tendency i
to not really consider those parts.
I would put New England l
3 in the same category. As a matter of fact, the geology of g
New England was not carefully considered in the development v
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It was not seen as being a problem area, and i
it just wasn't focused on. So that says, as the words are I
I applied in any of these four areas of identified, there was 3
always a question of possible relevance to those areas.
CHAIRMAN AHEARNE:
Say again what incidental I
' handling means.
MR. MINAGUE: I'm going to come to that.
That's i
l my next one.
The last issue -- and it's given kind of out I
i of the seismic and geologic areas -- Appendix A ends up 9
! with a discussion of some engineering requirements.
That to was added at the request of the ACRS for reasons that could 11
' have some merit.
They thought that the seismologists and 1:
I geologists who would use this fundamental earth science l
I:
oriented regulation needed some insight as to how this 14 i
I material would be used in design; and that you needed to 12 say enough about that so that they could understand that ultimate application.
g-i That's fine, except the problem is that what's
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in there is really too much to do that, but too little to I9 i
i i really define the engineering approach.
It's literally j
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I what I've called in here -- it's an incidental handling of l
g engineering, and it would suggest to the reader that you've done a lot more on defining the engineering requirements 4
than you really have.
I g
Now, the set of considerations that was issued with.
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the regulations made this clear, but such considerationc kind of get set aside; that is, they make clear that the I
- engineering requirements were not complete, were not i
2 detailed, and there was a lot more coming.
l I think this has caused a lot of problems in i
e I
the engineering area, because it just doesn't go far enough I
6 2
to really lay the issues, but yet it goes far enough to l
cause some problems.
And the people say, well,-have you 3
l
- shown this, and have you shown that, that's in the regula-P 9
tions.
i i
to Let's go on to the next one.
This is in the way i
11 of a very brief primer on what you' re looking for and I:
how you go at getting it.
There are a number of objectives i
1:
i you're af ter in doing the seismic and geologic assessment.
is First, you're trying to establish the design basis for I
12 1
ground shaking, shaking from earthquakes.
Second, you're 14 concerned about assessing the potential for ground rupture 17 l
because of fault movement, or it might be because of i
4 1
I I
subsidence phenomena or other things, but fault movement j
t certainly is where the major emphasis was.
The problem j
,0 there, of course, is that this is the kind that can both g
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breach the containment and cause a major loss of cooling.
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Seismic sea waves is another -- any coastal
- 4 site you have the problem of bcth distance seanominy a
and locally generated seanominy.
And last, you're i,
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concerned to define the foundation stability of the material i
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you build on, and the potential for landslides, subsidence, i
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liquifaction, anything that might cause some substantial foundation failure.
So these are really the four kinds 4
- of things that you're trying to develop in order -- as the I
end product of your seismic and geologic assessment.
4
- i Now, the next view graph identifies four conceptual!
7 elements that are important elements in assessing these points that -- and later on I'm going to discuss each of I
9 l
to these in turn and the problems that have arisen from it.
I i
g; The next view graph --
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CHAIRMAN AHEARNE:
Are these -- several of these
- g concepts, are they original with us?
14 MR. MINAGUE:
Well, can I answer that question as i
13 I go through them individually?
I think that would be I
f I4 the best place to answer.
i 17 CHAIRMAN AHEARNE:
Sure.
Fine.
18 MR. MINAGUE:
Let me just very briefly discuss l'
the methodology, and I'll try to be very brief on this.
IO These elements are used in assessing earthquakes by a 21 methodology that you basically have several alternate t
' procedures.
First, if the earthquakes that have occurred in a region can be related to geologic str::ctures, you go
- 4 through a methodology that's spelled out in some detail in 2
the regulations; where first you assess the ability to u,
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correlate the structures; you estimate the potential energy i
i i release from each of the structures using all of the 1
I available seismologic and geologic information.
Then you 3
calculate the attenuation from that point of origin of the i
A earthquake to the site.
You characterize the frequency 3
response of the shaking at the site, and then from thau, I
i in association with that, you specify the horizontal 7
acceloration that you're going to design for it.
This is I
all in the context of structure."
9 The second category is that you're not able to 10 relate the earthquakes to structures.
Then you use a 11 regional approach, or a tectonic province approach, which 12 i
is really an eastern problem.
When you do that, first you l
13 have to define tIhe province in which the occurrence of te i
earthquakes could have a significant effect.
You determine 12 the maximum potential earthquake in that province based on i
14 I
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the geological and historic seismic records.
You then assume, at least partly, that the maximum earthquake inten-i la i
! sity that can occur in that province occurs right at the l
19 l
i site, with the exception that in practice it's not treated I
as a near field earthquake in terms of the spectoral distribution.
In addition to that, you look at nearby provinces f
3 to make sure that there might not be an earthquake in one u
of them that would have a bigger effect at the site than the i m m ', m f9as Aguereget last as ImWTee tuu9% fruer, t e sesyt =W t
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! one in the province that you're in.
You characterize the l
i response spectrum, the frequency content of the shaking, i
I and then you specify the horizontal acceloration.
So it's 3
l a very deterministic method.
You go through some very 4
specific steps in sequence taking either of these two i
I tracks, depending on whether you can associate with I
I structures or not associate with structures.
7 The other issue that capable faults, of offshore a
faulting as they might generate'seanomie, and foundation 9
I stability, you do somewhat similar things.
The capable l
faults is really a very specific targeted geologic 11 j
' investigation of that fault to determine -- I'll be coming 10 back to that later, so I'll talk about what you look at 13 i
there.
But you' re trying to assess its capability.
The i
same thing with offshore faulting where you add to that the IJ l
phelup of looking at the characteristics of the faulting 14 as they might be at seanominie generator, the characteristics:
!7 of the coastline and so on as it might tend to intensify the }
is I
run-up effects.
l And last, the foundation and site investigation is,
Oc very much a matter, and you knew that in any case of a 1
i very, very detailed investigation of a site we're going to
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build to determine the exact properties and material as
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- 2 a basis for determining their characteristics under earth-n quake situations.
So that's the methodology that you go larrgnas h '/gmanets h !4 aus e M frWWP. E e. 3d,FT *EP
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,,c, through using these elements.
What I'm going to do is talk f
I to each of these elements in turn.
And as I do that, I'll I
try to touch on some of the questions that you've raised i
1 3
i earlier that I hadn't fully answered.
And if you're not 1
A satisfied with something, please holler, l
3 The first is the idea of tectronic province.
i i
6 Appendix A defines a tectonic province as a region in the I
North American continent characterized by a relative I
consistency of the geological st$ructural features contained 9
i therein.
That definition was literally written in about 10 five minutes, because it was not perceived as being a 11
- common situation that you would actually have to assess I
a site on a province basis.
It was an underlying presump-13 i
tion that earthquakes of significance could be correlated j
ta with structure.
Because of that, a lot of thought was not IJ given to it.
The definition as worded
-- let's go on i
14 to the next view graph.
17 The definition as worded implies, or can be read i
to imply --
19 i
CHAIRMAN AHEARNE:
Before you begin --
MR. MINAGUE:
Yes.
}
l CHAIRMAN AHEARNE:
I think what you're saying is I
~
l that it is not something that's widely used in the geological l 3
community.
2 MR. MINAGUE:
Not in the sense that it's used here.
i
= v
- m. m :=
m m Cass9%,FWWT. E e. SaffT N m-
19 o
s nusa no.
s t
I think the term -- the phraseology -- an'd you'll run into i
this.
This is the curse of geology.
When I first started l
I working on these criteria I went and got my dictionary 3
of geologic terms, and the first lesson I had was that nobody agreed with that dictionary.
I think you'll find e
' a lot of geologic terms are used in a very different sense l
f by different geologists.
It depends on what part of the 0
7
' country they work in.
It depends on where they went to 8
i school, what their predisposition is, how much they're 3
9 i
- related to engineering questions, how much they're oriented 1
1 to l
towards seismology.
11 I'm sure you could find sources where you'd find 1:
these words, tectonic province.
But I think that concept 13 as it's used in our regulation, or as it was intended to be 14 i
i used, is a novel concept.
As it was intended to be used.
's i
What it was intended to be used as would certainly have 14 recognized the significance of seismology, and would have 17 recognized the importance of when the geologic events occurred, 18 would have recognized that recent geologic situations are l
l
,9 6
more important than something that occurred 150 million
,0 1
years ago.
That didn't end up in the final wording.
It wasn"!
t
- 1 seen as being widely used.
It wasn't thought about as I
=
=
carefully as you normally would think about something like
- 4 that before you put it in a rule.
It just got stuck down, frankly, for the sake of completeness.
You know, well, what lef'ense. 'dNffes h M est & M frWWF. & W.
sWTT fer 0
J. 4. m
20 e
i if something like this arises. We'd better stick a r
definition in on that.
t This view graph on the orablems is the first one i
j 3
that reflects what we were just discussing, because you l
4 certainly can leave -- the concept that underlay this l
definition was to define regions of uniform earthquake 3
i 6
hazard.
It's really that simple.
That's what we were j
7 trying to'do.
But as I said, the wording wasn't carefully i
3 thought out'in the context of the eventual application, so i
the implication is that structural geology, and the con-to sistency of structural geology represents uniform seismi-i 11 potential.
And then when you've looked at that, you've done the job. And there's a counter implication of that, that somehow mapbe you don't really need to consider l
14 seismicity, or assess that structural geology in light of i
IJ seismicity.
Neither of these was intended, but that's the r
id way the words could be read.
[7 It doesn't reflect some very specific-issues.
18 Certainly neotectonic -- that is -- recent is a very l
I' l
relative term.
In this case, recent is -- my notes here i
- o l
say 15 million years.
In other contexts I've seen recent 21 I
as being within the last 10 or 20,000 years.
But j
certainly the idea is that tectonic processes within the last!
15 million yearn are more important to something that occurred hundreds of millions of years ago.
So the tuvipunaisemaa. 'essenme e puerwa !=
s as e Shim % STWWP. L a. theffT ter I
g
_ _ - J.4. aus
21 e o a
nas sc.
l
, orientation that you ought to have toward considering the I
more recent events, and not attributing so much significance
' to paleotectenic events, is not that clear in the regulation.
I 3
CHAIRMAN AHEARNE:
When you list that as the i
need for consideration in neotectonic processes in the eastern U.S., you're saying that a problem with the i
1 5
Appendix is that it doesn't focus on that?
7 MR. MINAGUE:
Oh, yes.
It doesn't focus on it 1
I at all, because if you really -- well, that's the only 9
i
' place it's been applied.
I'm sorry, I didn't catch the to t
eastern.
No, the only place this has ever really been an ti l issue is in the eastern U.S.
In the west, the geology is r:
typically, you've got a lot of active faults, and it's 13 l
l
' highly expressed.
g 14 The trouble is, the definition, you see, talks 12 in terms of a relative consistency of the geological 14 17 That's the end of it.
structural features.
And it stoos.
And that would suggest that all geological structural i
is
' features are equally important regardless of age, which is 19 l
1 nonsense. It would also suggest that all geological features are equally important, whether they have anything
{
g
=
to do with earthquake generation or not.
And there's
=
not even a relationship to the structural geologic 4
features to earthquake generating mechanisms.
And it doesn't-J go beyond that.
It also doesn't address the question of Imv4useationne. *dusastres agmauregung [g me mart'te 4M*T4n.,FuWP. L e marTT ter
-f4Ba. J. 4. ammt
I e
a 22 i
nas sc.
intraplate seismicity.
t u,w, at about the time this was done, oddly enough i
t I
a then commissioner, Commissioner Jim Ramey, I think, had some sense of what we were getting into.
He's maybe wiser than Staff, because he asked Staff to initiate t
an effort to try to develop a regionalization map, at least l
7 i in partsuof the eastern United States where the idea was l to start, as I recollect, in the southwest.
My memory 5
may be --I'm sorry, southeast -- my memory may be playing to tricks on me on that.
So generally, to begin with the it easier areas, and try to map the eastern U.S. using all i:
the available data to develop maps that would identify l
l 1:;
provinces in the context of equal seismic rifts.
The idea i
i 14 i was that if that were done successfully, Appendix A would IJ be revised to permit an alternate track, so that anyone 14 that was in one of those regions could use that as the i
37 design basis, and not go through this very extensive 18 l investigation program.
That effort and successor efforts, which have been :!
M i
0 going on to this day, none have succeeded.
Each has i
~t I
advanced the understanding, and has improved the recognition :
I
~
of some of these things I've tried to touch on in a rather 1
nontechnical way, but considering all of these diverse 4
factors as a method of assessing the seismic potential of a i=
w,
= w x
-l an emwww m sraer, t e. meres :er n
O 23 0
3 suss na.
' region.
But as of today we still do not have a generic i
f i
[mapthatidentiestheseprovinces.
But there's been I some real progress made, I think, in terms of a better l
2 understanding of how to go at the problem, the building of l basis for -- let's say, making comparitive -- comparisons e
~
of relative risk, hazards, among regicns using probabilistic 6
analysis techniques and so on.
There's been some 7
- progress.
8 l
CHAIRMAN AHEARNE:
Does the USGS, for example, 9
accept the basic underlying concept of the tectonic to provinces?
tt MR. MINAGUE: Well, I'm not sure -- accept is t:
a strange word.
The defindtion was written by Dr. Colter.
13 He was - I understand he recently retired, but he was a ta major --
13 CHAIRMAN AHEARNE:
Well, for example, do they
)
14 i
ag ee in their -- when you analyze with regard to i
17 l
i earthquake hazards for power plant siting, that taking --
' you can describe certain regions, and then apply the g
translation of earthquake, largest earthquake --
i 3
i 21 MR, MINAGUE:
Oh.
No, I don't think they would l
i
=
agree with that, nor would I.
I think I haven't presented i
- =
it quite correctly.
The methodology is an element of
{
t
- 4 artificiality.
When you deal with many of these areas in 2
the east, the geology is not all that clearcut.
% think the lef5 Mas?9estee.'#Weea m h Ing de m M ffWWT E e. SMTT ?W
&&M
24 i
4 sess me.
~
' GS would argue _aat any earthquake is' associated with some I
' causitive mechanism.
They're not truly random phenomena.
l 2
But if you don't know what the causitive mechanism is, you 2
may not be able to localize it within some region. So it
. may well be that the state of your knowledge is such that a
you have to treat a region in a way that kind of lumps it together.
And tdie. procedures in the criteria basically are 7
- based on that kind of thinking.
s i
l CHAIRMAN AHEARNE:
Have they -- was any mention made 9
to difficulty of getting any kind of agreed-up map together?
10 I
l Do they agree where the types of boundaries are?
11 MR. MINAGUE:
No, that's part of the problem.
I:
That's part of the problem.
It's a very difficult problem, is j
not just in terms of how big the groups are, how big the --
l 14 well really, there are geologic features that may be 12 common to adjoining regions that have other geologic 14 features that are different.
And now the question is, are g
the ones that are different the ones that are imoortant to I
gg i
' earthquake generation, or the ones that are common?
And i
you just run into that everyplace.
So --
l g
l Let me leave this by emphasizing though, that l
the procedure in the criteria is intentionally very deter-
}
=
ministic.
It's a do this, then do this, then do this, and
- 4 it's based on the assumption that you may be dealing with a 2
situation where the geology is buried, or there's inadequate l
i
=,v
==
u
~,.. -.
m.
25 o
s nas.no.
I l surface expression, and that you're speculating.
You know, i
I that you're not -- let me phrase that more precisely --
I that you're not in a cosition to localize.
And if you're noti I
in a position to localize, then you should assume it can be t
anyplace, because that's the conservative direction to go, j
1 And that does underly this methodology.
The next -- should I go on?
The next element is l
7 tectonic structures.
The criteria defines tectonic 3
$ structures as large-scale dislocations or distortions 9
i within the earth's crust with their extent measured in 1
to l
miles.
That's -- to call that definition broad is an it understatement.
And that's actually intentional.
The I:
number of types of structural geological configurations is j
that that would be intended to cover is extremely broad.
l 1s The wording was that broad right from the first drafts of I
13 I
the criteria.
Nobody really balked on that because I think 14 it was more the basic concept of relating earthquakes to j
t some kind of specific geological situation that that was I
la i
intended to speak to.
But there have been problems with
,9 l
l it, and I think these problems arise from a lack of any i
.o t
s I
real definition as to how you decide what constitutes a tectonic structure; you know, how you -- let me give some n
specific examples.
- 4 The criteria rather indirectly recognized that in a
some cases the evidence may be buried, in others it may be me
, v r % %
g age m M 2TWWF.L8. BefrW *W
& 2. aum
1 I
26 o
=
.m expressed on the surface.
But how you a'ssess structural
)
l f geology taking that into account is not spoken to very l
I I
! clearly.
There's no real clear recognition of consideration 2
of correlating patterns of seizmicity, of which there's a growing data base, to better understand the structural a
geology.
l Earlier you asked for examples of things in the 7
j regulations that have been kind of counter to advances in g
t itechnology.
That would be, again, such an example, as 9
you've built a better and better data base of seismic to events.
There's nothing really in the criteria that l
11 j speaks to how you correlate these.
I:
The intended thrust of the criteria, of course, 13 i was -- and it's not at all explicit -- is to say that the u
- seismic record, the historical seismicity, should be l
13 i considered in the light of structural geology.
But the I4 i
l way that was stressed in the criteria, what we're really i
I 17 f
i l
saying is that the reverse.cncept -- the structural geology should be assessed in light of the seismic reccrd -- I
,9 i
5 r
just got kind of lost, got submerged.
l t
21 Another matter in this same context -- it's not at l l all clear -- and this was intentional -- was, what's the i
i
=
scope of investigation?
How much is enough?
The emphasis
{
- 4 in the criteria is what you look for.
It's good on that, 2
really lays it out good.
When have you looked long enough, ow x
]
de se,He M #fBWF. E s. ment 'er e
u a. c.==
pass.we.
27
.I o
s
' and when do you close the books and say I can now make a i
t i
' decision?
Not at all clear, not e'ren really addressed 2
very clearly.
2 l
)
i So the scope of the info::mation required to say 4
l I've identified a structure or not identified a structure is r l
just not clearly spoken to.
l i
And the last point -- and this is common to all of these -- there's lack of any real guidance of what one I
?
means when one talks about correlating earthquakes with i
structures.
The term is used, but it's not explained.
And some of my geological associates may want to g
correct me on this, but I don't think that term either, the g
i 12 idea of correlating the structures, would be a widely l
7, used -- would be. understood the same way by all geology 14 types.
I don't notice any disagreement, so I think there's I-i r4 another example of terminology that's used that is not 17 common to the entire geologic profession.
i l
14 MR. JACKSON:
I could expand on that a little bit.
i l
19 MR. MINAGUE:
Please do.
20 MR. JACKSON: The --
1 I
21 MR. MINAGUE:
This is Bob Jackson.
j MR. JACKSON:
Just an example would be an argument i
of correlation of earthquake epicenters with structure.
And '
I#
at the time the Appendix was written, you would be relying on primarily historical intensity data around a given fault is,
= v es ns.,rne ens **4h. ftWWF. E e ma,rt te,
_ 2. 4. agit
28 i
- a nax.sa.
I zone. Under present day techniques and more accepted I
techniques, good seismologist would go out and require a I
dense seismographic network around that fault zone.
And i
2 i then even with that, in the location ability of a dense I
network, still not be able to pinpoint that epicenter as occurring or falling right on a projection of a fault l
4 I
plane at depth, the hypocenter occur;ing.
So you.-- does 7
- that regulation really speak to that earthquake hypocenter, s
should fall right on the projection of the fault at 7
depth?
Is it within plus or minus 1 kilometer good enough?
i to l
And that's where it's not addressed in here, and that has 11
,' become, you know, a point of contention.
i-12 MR. MINAGUE:
Thank you very much.
A major scurco 1
i of this kind of problem, of course, is the data base that 14 people used in the last '60's, was largely historical l
l seismicity that was based on human observations, not i
instrumental determinations.
So a lot of the correlation i
17 I
was basically just gut feeling.
Well, it was somewhere in l
I that area, it's probably related to that structure.
It's not,i
- 9
.g the kind of very scientific thing that Mr. Jackson has commented on.
l Let me go on to the next concept of capable
- =
fault.
This concept is clearly unique to Appendix A.
It
- 4 obviously met a long-felt need.
It's used world-wide.
It's been picked up in just exactly the context it's used,
- tow,
% t=.
l me sun, vie c.us.4a. fruer. i e. asNT te, m-
29
~ o
=
pass.*e because what it really talks about is something --
CHAIRMAN AHEARNE:
Used world-wide by I
geologists?
2 MR. MINAGUE:
Yes, it's used world-wide in the geologic profession.
The term has gotten very wide
,f I
e i
acceptance.
I've heard it in all kinds of wierd contexts.
l t
8 l
It's used in the IAEA criteria.
It's -- I think the 7
- reason is that it bespeaks a focus on the possibility of 1
surface movement, and a looking back in geologic time 9
i
- that goes beyond the normal term of active.
Active fault to doesn't mean the same as capable fault.
Capable fault is r
11 something beyond that.
You've looked harder, you've looked 1:
, back more in geologic time.
13 I
1 CHAIRMAN AHEARNE:
Is there wide-spread acceptance la of the criteria used?
I4 MR. MINAGUE:
Yes.
The criteria or something l
14 l
very much like them are fairly widely used.
Yes.
A lot l
17 depends on the level of risk you're concerned about.
The j
ta i
contert in which you would use criteria like this would be relocing reactors, locating major dams and stuff like that.
,0 1
You wouldn't use these criteria to put in a housing l
.)
)
l development.
You'd think more in terms of insurance risk, t
so you think in terms of 10,000 years, not 35,000 years, or 4
a something like that.
But yes, I think this general u
approach, partly because it met a need, has been very widely i
ri v
,,a x
{
m sun, rte taasve, fruer. L e, as,rt 'st
30 a
I russ.sc.
used.
I COM. BRADFORD:
Just how is it used, Bob, in our I
I own -- for our own purposes?
I MR. MINAGUE:
Well, it's used to define whether a fault is capable or not.
Now, if the fault --
4 COM. BRADFORD:
what then does that mean?
6 I
MR. MINAGUE:
Capable means that that fault has
- the characteristics that there's a high enough liklihood 8
i that you will get surface disruption because of it that I
9 i
you have to do other things that the regulations spell out to l
' relating to considering designing for faulting, or giving 11 l extra attention to the geologic history of the structure t:
i in assigning an earthquake to it.
13 i
COM. BRADFORD: Let's see, have we ever approved a' 14 plant on a. capable fault?
f 13 MR. MINAGUE:
No, not knowingly.
COM. BRADFORD:
So that does -- so that you don't 1,,
then get into what other things you do,. except perhaps --
1 18 i
MR. MINAGUE:
Well, I'11 come to that.
That's I
an important point.
I'm going to come to that on the next g
I view graph.
l i
3 i
=
CHAIRMAN AHEARNE:
Is number -- the third part of
=
your definition, is that kind of relationship clear?
l
- 4 MR. MINAGUE: Same problem.
Same problem.
We keep u
coming to that.
That just recurs over and over again.
i imen.nen Veenme meewma!=
ass e daarum, ifB47. E e, mMTR 'O
& f., M
- 0
31 l
o a
nas no.
Let me give you a little background.
An obvious question here is why are there so many tests.
And I think a
I
- it's important there to recognize that the perception was--
2 and it's a true perception -- that on specific sites you're often not able to obtain data on any one of these tests.
3
' So you really need a multiple set of tests.
If one failed, i
i then you looked at other things.
And you put them all 7
i
- together and you could begin to get t.he level of assurance 3
that you would really like to have.
9 9
The emphasis on recency of movement, in a sense, to was Commission direction, because in the Malibu decision I
l
' that's what they stressed, recency of movement. So that I:
really was the beginning criterion. And as we worked on 13 that it became more and more clear that age dating wasn't 14 i
all that straight forward; that the applicability of the 13 i
14
' date was-not all that straight forward, and we began to look l
for other tests.
They are relatively independent of each 17 5
other, although that isn't made. clear in the criteria.
I There's a fourth test that's mentioned in the M
i paper that's a reverse test, and that's a noncapability i
,0 test, structural association with geologically old struc-l
,1 4
i tures.
And that's identified with eastern geology.
That's
=
3 the only place in the criteria that there remained a 4
residual recognition that eastern geology was different 3
from western geology.
Earlier versions made a sharp lmfugnine, 'tWeesfnis h !sur.
eng m Gass *m.#fBWF.E a. marFWfSF 1& M
32 4
e ammt.we di'stinction between eastern and western at the Rocky i
' Mountain front.
But that eventually was taken out, and I
' the only real differentiation is that it's rather clear i
i 3
that the test or noncapability test of geologically old j
structures is clearly related to the eastern geology.
I I
CHAIRMAN AHEARNE:
It's a link to a geologically l
i i
old structure, with lack of evidence of --
T MR. MIhAGUE:
YEs.
The wording is that it
{ shall be considered not capable, lacking clear evidence 7
to the contrary. The emphasis on the burden is pretty 10 clear.
You know, a showing of relationship to an old II l
structure almost says you can stop looking because it 1:
I uses terms, as I recollect, clear evidene to the I
I is contrary. It's very strong wording.
l ts l
'The next view graph summarizes some of the issues.
12 I think the first cne is really an important one.
There's I
14 no really clearly thought out rationale as to why this age dating has any real relationship to the liklihood of i
l ts movement tomorrow.
That's just sort of an assumption.
f 20 21
=
l e
- 4
- 3 levgumam Vaness9es h 14 g
me sun,fte sam *4t. #TuWP. & e. marfT 'er eassummas*alun. J. C. amit
a Sc 33 i
nez.wa. _
l Tape 2/ 1 l
PL I
MR. MINAGUE:
I'm going to run through this one fairly quickly.
There are a number of problems that immediately arise when you try to apply these criteria.
4 3
For example, they use the term like recurrent movement.
"*11' the evidence of successive episodes is not always j
6 i
l all that clear.
But very often you get a total sense 7
i of displacement that just physically impossible to have 8
occurred in one episode.
So that seems fairly clear cut.
9 I think that the displacement may occur at different to times along different parts of the fault system.
Faults 11 are extremely complex systems and you're going to quickly I
get yourself into real problems because of the correlation j
i 12 of movement on different parts of the fault, deciding la j
what significance to give to the amplitude of movement, 13 the application of age dating samples from other parts 14 of the fault is that really applicable or not, there j
z.
are all kinds of problems th.t arise from this.
l The next item is relative age-dating.
I think g
I this is to some extent a personal group.
It's not so j
19 strongly read in the paper.
The criteria relegated age-dating techniques to a footnote.
As an afterthought.
21 It was back in a different section.
We find in the real t
~
world the problems of getting good solid, and I'm really talking about the techniques of going out in the field l
I#
l and taking the samples, the problems of getting good,
-s levennartense. ',euenme Superegnut !=
j as sauves e.aa ve. srauerr. t e. marrs *w
- a..===
.~
l PMsg No.
PL 2
i l
2 solid data frcm which you can get age dating are really 2
i pretty serious.
And it's not all that clear that what i
l you've got really means anything.
At the same time 4
the criteria kind of downplays the fitting cf displace-r 3
ments into some kind of geologic time record.
If you look at relative techniques, looking 7
i at geomcphologic effects and things of that type, you I
l j
can get more of a sense of how this all fits into some 9
ongoing process.
You're really now talking about 10 something that's more realistically part of assessing 11 the likelihood of movement occurring tomor:cw which is tI l
really what you're worried about, something happening now not what happened 35,000 years ago.
13 I4 l
The next one is a question of what's macro-i t.!
seismicity, the criteria used that term.
Again, this 14 is not really a standard term.
It was generally felt among the staff that that meant greater than magnitude j
i 3, but it's not stated explicitely and not everybody 7,
would agree on that cut-off point.
Structural relationship I think we've discussed
- o and in the interest of time I'll just zip right en.
One 21 point I might mention is the issue of whether structural i
relationship necessarily implies a physical connection l
or not.
It wasn't intended to but it was read by some I'
at least that that is required.
- 3 langanatienea. '#WeenfMe h Isus.
de M 4MuT4. ffMWP, L e, SMTR !aly 2 4. m I
l
0 2
30 I
asas no, f
PL 3
f l
l 2
The Eastern U.S.
treatment of faults relating to old structures I've commented on.
2 l
Let me talk to the one that Ccmmissioner 4
i Bradford raised.
The question of designing and constructing 3
i for faulting and whether the intant of these criteria l
was to prohibit building on a capable fault.
First of all, 7
l there was a clear presumption on the part of the staff 3
i l 'that I think most in industry would agree to that you 9
really can't design for a fault.
If you look at the to data fran what's happened c, taults where there's been it movement in the last some odd years, and I meant to l
C comment earlier that the major data base that was used C
l in developing these criteria was that.
It was a study ta of movements on. actual faults done by Doctor -- he's f
13 not a doctor, they call him Dr. Nella of the Geological r4 Survey -- was a very large part of the basis.
i
- 7, When you look at how faults move, what jumps l
out at you right away is that the movement can be 10, 15, 20, 40 feet.
Well, it's not really practical to i
I' i
design for that.
So I think there was a presumption you i
- S couldn't design for it.
21 As the Commission focused on this, they were I
~~
I think somewhat bothered by the fact that the way j
the zone in which faulting investigation detail was l
I' required or was determined was extremely conservative
- 3 i=== % v m.= m a x mwm summ.fuer.s new:n
?
_- A t au
E l
\\
o o
pass se.
PL 4
l i
t 2
I and that we were really going to far if we turned that 2
into a flat prohibition.
So the regulation ended up 4
coming out saying if you were within that zona you had 3
to do some sort of super investigation that would be l
3 based on the investigation up to that point.
7 As,a practical matter, I think the practicality of doing such an investigation is probably questionable.
t So my own view is that the effect of the criteria is prohibition on building within a zone requiring detailed to investigation of a design basis for surface ~ faulting.
11 The 4.7 context makes it a prohibition since that's j
I within five miles, forget it.
And the Task Force, the l
U Siting Policy Task Force has made a similar recommendation. '
I4 Different distances but the concept is the same.
I!
COMM. BRADFORD:
Let's see, and that's regard-t 14 less -- as I understand the definition, regardless of t-the cause of the movement.
jg MR. MINAGUE:
Well, no it would be fault move-ment associated with some kind of deep-seated crustal l
l II I
disturbance.
You can get movement because of localized t
subsidence and particularly on the coast from pecple 21 withdrawing oil.
Long Beach has had lots of problems 22 with this. It's ccmmon on the Texas coast.
You can get i
~~
l relatively small surface disruptions there for which i
you could design efficiently I think.
lesTWunaf'tennae. Venantgas h lang, me marfte 4aarT4a. #TWWF. & e, mart's tar
- 2. 4. amm
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PL 5,
I 2
What I'm talking about here is in the context l
2 i
of major fault movement associated with deep-seated i
l crustal disturbance.
Not localized fractures caused 4
3 by subsidence phenomena which is really a different ball game.
6 l
The underlying ccncern was -- I remember well 7
when the data first began to come in and the amplitude i
of the movement became clear, it's startling large.
The 9
40 foot figure was not pulled out of the air.
There to have been displacements of 40 feet.
Does that answer the question you raised earlier?
I' COMM. BRADFORD:
Well, the only case that I'm I
l 13 at all familiar with in dealing with this concept was l
i I4 Sears Island in. Maine where they had a great controversy i
!3 over whether glacial rebound in fact was a cause of I
t4 movement that one would worry about.
And I'm not sure g-that a clear answer was given, and if given it certainly was never received.
MR. MINAGUE:
Yes, I think that the question I
of the magnitude of displacement associated witn the phenomena in that case that wouldn't be in the 40 foot 21 range.
The issue as I recollect it was whether or not l
that fault was a capable fault according to these criteria,;
i l
and the answer is it 1s.
l l
- a I think here's a case in point where one might i
3 n
v m
,,ai e
j
. men.
sv==r. s
m :
i
suss no. &
PL 6
I I
i argue that the Commission was wise not to not make it a 3
l flat prohibition because I think it would be debatable l
l whether or not one could design for the kind of displace-4 l
ment you might get there.
That would put that more in 3
a category with the fluid withdrawal phenomena that you j
get.on some of the coastal sites, j
COMM. BRADFORD:
But if it is a capable fault 8
i l
I gather frca what you say then that regard 4.7 9
MR. MINAGUE:
Well, they'd have to review the to applications.
M Well, in context -- it's analagous to the C
demographic criteria in 4.7.
It doesn't say it's a C
flat prohibition.
It says if you don't meet this test j
14 then special attention is to be given to alternate sites.
l i
y COMM. BRADFORD:
What about the Siting Policy
?
Task Force?
g MR. MINAGUE:
They would argue for a flat g,
prohibition the distance being -- they don't talk in terms of zones, but faults.
I'm not quite clear how l
l one can apply that, but it's a 12 mile from the fault t
20 is the figure although I don't think they would fight
- 1 for the 12 miles.
I think that's a fairly arbitrary i
figure that would be developed.
U It's more a concept to prohibit locating on j
22 capable faults.
Again, I'm sure they had in mind deep 2
4 i=
=v m
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_n
- r. s== :n s s==
i
o nsas no.
39 PL 7
l t
I l
I I
seated crustal disturbance.
They're not talking about i
2 local subsidence phenomena.
4 There have been a number of cases and all of 3
which the applicant has withdrawn that have involved capable fault.
This is not a minor issue.
A lot of t
6 sites have been scrubbed because of this issue.
7 COMM. BRADFORD:
But is glacial rebound, for 3
i example, a deep-seated crustal?
j MR. MINAGUE:
Not in the sense of these criteria
'i 10 contemplated.
i 11 COMM. BRADFORD:
They would not be, I see.
g.
.I'll exaggerare and put it in MR. MINAGUE:
I3 the context of the San Andreas Fault.
That's pretty id far in the other extreme, but it's that kind _of situation.
14 The Newport /Inglewood Fault or, you know, rather major',
i to through-going systems that, reflect some deep-seated l
g-effect.
Not localized phenomena.
MR. JACKSON:
I could comment on the Sears
- g Island case and admit the problem there was one of 19 with the utilities.
As I understood it, was concerned
- o with the literal interpretation of the regulation i
21 l
and would conclude that the fault at the site was a I
capable fault, whereas the staff probably would not have j
concluded that that <as a capable fault.
l 4
l Being two different classes and usually l
i
% v.
o x
i
_2 s s --
0
40 l
o s
u.=
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PL 8
i i
I I
2 l
confuses people, but not all hazardous faults are necess-I arily capable faults.
The view is that a capable fault 2
i l
is equivalent to an earthquake fault.
That the surface 4
i 3
offset aspect and the earthquake aspect go together.
You i
can gave other faults, such as the faults you have in i
3 the Houston area, which have movement on them and surface 7
displacement but don't necessarily generate earthquakes 3
i of a damaging nature which would fit into the literal 9
interpretation of Appendix A, but as viewed within this to regulation and in consideration with the USGS would not 11 necessarily be a capable fault on the consideration of t **
ground motion or surface displacement under a plan.
l
!s MR. MINAGUE:
I have to take a slight exception i
I4 i
to that because. capable fault is a legal term.
e 13 MR. JACKSON:
That's right.
14 MR. MINAGUE:
If they meet the criteria, they're j
- 7 capable.
What you're scying, and I don't disagree with j
that, is that it's possible for a fault to be capable 3,
and not be a hazard.
Not be a hazarl that you couldn't i
19 l'
i design to accommodate.
- o MR. JACKSON:
This is the problem.
MR. MINAGUE:
But the ter a is a legal term.
=
CHAIRMAN AHEARNE:
What is a hazardous fault?
9 MR. MINAGUE:
One you cannot design for is i
- s the way I chose to define it.
One that you can't i
- 3
- i. % = v e me.-wai=
umn. mmer.s
=res,.
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'a 41 esas.~ea, PL 9
l
I i
I accommodata in design.
3 I
I think it's important -- I know I keep coming I
4 back to Malibu, but recognize that Malibu is what l
started all of this off.
And the desire was to get some kind of a "go" "no-go" type criteria because most sites 4
l where capable faults had been at issue they had been 7
i hazardous faults by anybody's definition.
There was a 8
l desire to close that.
7 CHAIRMAN AHEARNE:
My ignorance is such that --
10 was Malibu at Malibu?
11 MR. MINAGUE:
Malibu was near Los Angeles.
It's tI on the coast.
I3 CHAIRMAN AHEARNE:
I know where Malibu is.
14 MR. MINAGUE:
Yeah.
13 CHAIRMAN AREARNE:
It's near that area.
to MR. MINACUE:
Well, it's near that area.
I g
think Coral Canyon, I think, was the correct name of the
]
site.
The case is commonly called the Malibu case.
CHAIRMAN AHEARNE:
How far from Los Angeles?
MR. MINAGUE:
I really don't know.
- 0 i
MR. DIRCKS:
About 30 miles.
I 21 COMM. BRADFORD:
Not quite in a class with i
-~
Ravenswood.
3 m
(Laughter.)
i I'
MR. MINAGUE:
I can't stress that too strongly.
I
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& & Juuat l
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42 PL 10 i
l I
j There have been a lot of sites dropped because of this 2
issue.
It's one where one should be very conservative.
l If you're really wrong and you've just had an accident 4
3 that boggles the mind because you've breached the contain-i i
3 ment at the same time that you have the accident.
There's l
no containment.
7 Let me zip along I'll try to be brief on the 4
1 l
next one I think it's been touched on.
The extent of 9
the investigation necessary -- I touched on that earlier.
The last one is important.
All these good 11 new techniques that give a lot of insight into the kind t*
of things we're worried about and if we persist it here l
t*-
I'm to be very much supportive of what Mr. Jackson just 14 said.
If you insist on applying the understandings 13 and techniques of the criteria of the
'60's, you're going l
i 16 to categorize faults in a way that dcasn't completely i
conform to what you now recognize as being their true l
g, hazard because you're not taking advantage of all this other souce of data.
That would be another example that you asked earlier for examples of where the new techniques -- if you sat down today to develop tests for 21 capable faults, I think they might look very, very
=
different.
Essentially everybody's copying these because I
they don't use a lot of new data.
5 The next one I think we've discussed this
- 2 in n
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- e. s w.
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o e
43
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i l
I correlation sheet.
I'd like to just go ahead and just touch very briefly on some of the engineering issues t
4 that I can at least identify for you.
3 The first is a number of issues that relate to laboratory geometry.
At the time the criteria was l
4 developed it,wasn't really practical to develop site 7
specific response spectra although that clearly would 3
have been a better way to go.
We would have been much 9
more comfortable with that, but there just was not a data base.
Because of that the direction of the criteria it is sort of generalized response spectra.
That's been clarified in the Regs l'.60 after some evolution in is i
between.
There've been several versions prior to that Id version that's in 1.60.
And it's based on the assess-i 13 ment of some earthquake records, but as time has gone l
i 14 -
on and more and more earthquake records have been s
g7 developed there's a distinct move toward site specific g,
response spectra.
A number of current sites are being evaluated that way.
It's not precluded by Appandix A and, in fact, they use a site specific response spectra as essential for some features of assessment dealing 21 with things like the fracture phenomena and so on.
I
~
The next issue relates to the variation of l
l
'~
ground motion with depth.
The data base of the mid '60's l
4 and premid-60's with regard to the intensity data, that's
- 2 ic,%r:
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+
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44 nus.w PL 12 i
I l
I all surfa.qe data.
The Regulations speak to defining I
T the acceleration at the level of that accommodation l
4 meaning material present is soon to be at surface --
3 ground surface material.
The material on which you build the level of foundation.
Well, that's okay in a 0
rather crude sense of. assessing intensity data.
It's 7
not really that useful.
If you want to do as you often 3
are required to do more sophisticated analysis of 9
soil structure interaction, liquid fraction phenomena 10 and so on, you've got to build in an additional element 11 i.
of precision in this definition that just isn't even g.
recognized in the criteria.
l r
is Another.one is specification of time history.
14 If you do a computer analysis of time motion history is and now as to what you would get are a family of an i
!a analysis which you would get from the strong motion seismograph is a good way to define your input, not a l
is response spectra which reflects a cruder methodology e
of analysis.
19 Expanded guidance in this area would be
- o useful.
A lot of people have taken the smooth response 21 recommendation at 1.60 and developed an artificial family
-~
of time motion history, but this is an area that I t
I think that the crude data base could be examined further.
l I'
The other one is the question of duration of l
i-v
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l l
I shaking.
This is important both in terms of the signifi-2 l
cance of isolated high G peaks and the question of sus-l tained shaking.
I think the present methodology that's 4
3 used tends to possibly be excessively conservative in this area.
3 i
The next general area is the so-called OBE or 7
The criteria basically define 1
f a shutdown earthquake or an SSE to protect the public in 7
the event of a severe earthquake.
The plant may not be 10 i
operation after it's over, but the public is protected.
11 The OBE is a rather different concept as the I2 regulation presents it.
That is, there it's defined as I3
{
the most severe earthquake following which you can go la l
back under operation without an extensive inspection i
13 of the plant.
- Now,
'n practice the uses of the OBE f
t4 are much more complex than that just described.
And this is an area that there's considerable confusion on.
g;.
It almost warrants a separate briefing.
There's an f
additional attachment to s.c paper that I think U
l l
summarizes it pretty well.
i 32 l
Aftershocks is another area.
I don't 1
21 i
think this is terribly important because the examiner l
that's used now will permit only very limited deforma-i
~~
tion, but certainly aftershocks can be as severe or i
nearly as severe as the initial shock.
And if ycu get --
- 2 i
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e sente c,aseTun_rfuMP E e mart 4 ist
- & & mm i
o a
46 naz.4 PL 14 t
2 particularly if you get extensive deformations you can 2
change the natural frequencies or you can get situations l
where you had to work about the number of cycles of 4
3 i
shaking.
I don't consider this as a major problem.
Anodier problem that's kind of related back l
3 i
to the CBE question is the problem of potential damage 7
}
from earthquakes less than say a shutdown earthquake.
8 l
The OBE generally is applied as a design perameter only j
to the same stuff that's designed for say shutdown earth-to quakes.
So this is the same issue of what safety equip-11 ment and what isn't.
You've heard a lot about this 1
1' recently in another context and in much the same mode.
13 If you think of it in terms of shaking the hell out of I4 l
a whole facility, you have the potential there for j
1.!
common failures of a lot of the equipment and interactive r
t f4 systems.
And if none of this stuff has been designed l
e
- 7 for any kind of earthquake level at all, there's an issue there you really need to be concerned about.
3, I
Because earthquakes -- this is a rather seismic country, 19 they're not all that unusual.
t
- o The last element, in combining loads probability 21 considerations have not been done on a rigorous basis.
=
The last one I want to touch on and then I'11 I
close is the question of the need for seismic scram.
This has been a back and forth between the ACRS and the I
( 6 h '# Ween 19ee h !4 me saffee SMsTW. fTWWF. 3, e. marFE 'er 9
- -14 m 0
ee 9
6
i 47 I
G cm o.
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I l
1 I
Staff for a number of years.
I think there's a slow 3
evolution in thinking on it.
In a sense it's a nevermind i
4 question because the likelihood of the plant tripping 3
out on turbine vibration is so high as to be almost i
i 4
a certainty so you're going to scram anyway.
9 i
So, people actually talk about seismic scram 7
l is early initiation, some kind of a seismic measuring 5
f system that senses the earthquake coming and some are 7
able to differentiate if this is a big one and starts to l
to shut down early.
If you could do that, that would 11 clearly be useful.
1:
l COMM. GILINSKY:
Isn't that something that i
13 I
I at least I've heard of in Japan.
They have something i
l 6
l N
of that sort.
I3 MR. MINAGUE:
I was going to come tc that.
14 The drawback of that is the possibility of spurious f
17 scrams.
And the concern about superimposing transients.
la l
There have been analysis made by Livermore several years I
ago that indicated the net was not all that valuable.
g But in the meantime there've been a lot of improvements in instrumentation.
21 l
The Japanese have a rather complex system j
l involving multiple detectors and basically a technique j
m
~
of kind of screening out so you don't get so many spurious 24 scrams as I understand.
I'm getting this secondhand.
J t - em ven.,====-wa x de taffte 4pFTM ff4IWF. E e. AsfTT tet f
De
48 f casa m PL 16 I
2 l
I think generally that this is an issue that isn't completely closed out.
It may well be that instrumenta-2 tion techniques might be improved enough.
This has always been kind of a borderline l
A 6
question which way you went.
It may well be that there might be improvements in techniques that would warrant 7
l going to seismic scram.
I i
Appendix A on the subject of seismic scram 7
requires instrumentation to measure the earthquake.
It IO says the issue of seismic scram will be resolved at I
11 some future date.
So that question was left open for 1:
other criteria.
13 In summary if I may, I think that this report i
14 has already achieved a great deal in the sense chat I think a lot of the discussion of these issues now f
14 by the parties who have given very wide distribution to l
g it is now at least on some common base.
17 l
The recommendation was that we take a lot 18 of this up out of the Regulations and proceed te develop 19 guidance type documents like red guides and put the 20 major basic principles in the Regulations but do the 21 details in guides.
That program has been deferred for
~.
several years.
There are a number of guides out though, 3
if you look at the stack some of these are fairly i
- 4 detailed technical reports including numbers on
- 3 lesegumsfinnae. Venant9te h last, as agWTes abaseTm. spuWF. & e. masTE ter
_- & & mm
I e
a 49 asas ~ea.
PL 17 i
e i
t intensities and so on.
It's not quite as impressive as the seismic.
I l
In addition to that the IAEA has put out 4
guidelines on earthquakes, much the same coverage as Appendix A that correct many of these problems.
So i
4 there is a document in existence that's mors recent 7
and I think certainly much of the issue we talked about here of the proper consideration of seismicity i
is dealt with in the IAEA document.
So we're not 10 without guidance during this interim period.
II CHAIRMAN AHEARNE:
I gather that your
~
i C
conclusion would be that as far as the basic regulation i
I m
l and the Appendix is concerned, the knowledge has far i
14 surpassed what's there.
f.
MR. MINAGUE:
Oh, yes, that's the bottcm I
g The state of the art has just gone -- I think I
line.
it's a good job.
I put a lot _of time in on it, and I j
L.
make no apologies for it.
The state of the art is just I
ts t
such that it's behind.
19 CHAIRMAN AREARNE:
Would you say that it i
- 0 represents a unconservative, overly conservative, or 21 mixed bag?
MR. MINAGUE:
It's a mixed bag.
I think the j
U tendency probably in terms of shaking in the East it's 24 probably if not right on probably a tad on the 1
- 3 Imf'tesnaa. Veumaften h 14 e m m iTWWF. & e. SIMTT 'SF s'
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I i
4 1GL.:
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na
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1
(
nonconservative side.
In the West it's probably the other 2
way around, it's probably too conservative.
l When it was being developed there was a lot 4
3 criticism that it was unfair to the West.
That because the geology there was clearer that we applied tougher l
4 tests to them than we did to Eastern states.
7 Besides the geologic question it's not that t
l far off one way or the other from where it ought to-be7 l
In the area of the designs that results from it, I think to there's a lot of excessive conservatism.
Research has g
T1 got a major study going to try to get a handle on this, but some of the design procedures for which this is IU implemented just cascade with conservatism.
They pile 14 on top of each other to the point of being ridiculous.
j i
13 As far as the seismology and geology is l
}
- 4 concerned, I'm not a geologist but in my opinion is l
- 7 it's probably just about right.
Maybe a little high in some areas a little low in others.
It's in the right ballpark.
CHAIRMAN AHEARNE:
Vic, you have a question?
i
,0 Bob, thank you very much.
21 (Whereupon, the Commission was adjourned I
at 3:00 o' clock p.m.)
l
- 4
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_2===
Outline of briefing for Comission on information report, " Identification of Issues Pertaining to Seismic and Geologic Siting Regulation, Policy, and Practice for Nuclear Power Plants," SECY-79-300.
l I.
INTRODUCTION A.
Purpose To provide the Comissioners witi, information pertaining to Appendix A to 10 CFR Part 100 contained in the report as it relates to NRC's reassessment of Appendix A and to the issues identified to date.
Specifically, the earth science issues of " tectonic province," " tectonic structure," " capable fault," correlation and relation of seismicity to tectonic structure or capable faults.
B.
Participant Robert B. Minogue, Director Office of Standards Development C.
Representative 1.
Dr. Robert Jackson, Chief Geosciences Branch D.
Organization of SECY-79-300 (handout report)
Three major enclosures of the five (no need to elaborate).
1.
Enclosure A - issues stemming from geoscience requirements in Appendix A (most significant enclosure).
2.
Enclosure B - issues arising from engineering requirectants in Appendix A (next most significant enclosure).
3.
Enclosure C - issues concerning a broad spectrum of policy and technical issue bearing on the implementation of Appendix A.
4.
Enclosures D and E - backup material.
E.
Rela tive Importance of the 'R'eport 1.
Report marks the first time old and new issues have been placed in a single document.
2.
Report issues were developed from a broad spectrum of views covering several disciplines (geology, seismology, and engineer-ing) gathered from NRC staff, ACRS, U.S. Geological Survey (informally), consultant comments and public comments (Federal Register Notice Vol. 43, No.13,' January 19,1978).
3.
Report serves to provide staff, public, and industry an idea of the issues and how the earth science and engineering disciplines interface with one another.
4.
Report serves to give applicant; and their consultant some idea of how proper planning might help to avoid future trouble.
5.
The report is fairly complete, about 100 copies were mailed out; only two coments have been received. One indicated several areas for possible improvement.
F.
Original reasons for Appendix A 1.
To provide guidan::e to alleviate problems discovered in the early site evaluations (Bodega, Malibu, etc.).
2.
To provide guidance for scientists and engineers. Also, to provide a standard or measure for determining the size of an earth science hazard.
3.
To provide guidance for applicants.
4.
To provide guidance for Commission staff reviews.
5.
To provide guidance for establishing legal framework for legal decisions.
e G.
Historical Development of Appendix A 1.
Regulation came about from siting problems and needs encountered in California in the mid 1960's.
2.
Work undertaken in 1966 or 1968?
3.
About 18 major drafts.
4.
The bases for the regulation were established in the late 1960's (mostly by USGS).
5.
Methodology and thinking started to be used in reviews in 1969.
6.
Published in 1971 for comment.
7.
Appendix A methodology began to be regularly employed in early 1970's and to be reviewed by applicants, public, etc. (Mendocino, 1972).
i 8.
Appendix A became regulation in December 1973.
a.
Represented synthesis of broad spectrum of professional views.
b.
Compilation of procedures and methods developed from experil ence gained during review of early sites.
9.
Framers recognized state of the art, data base, and future need for revision when warranted.
- 10. Since December 1973, advances in the sciences of geology and seismology, and engineering procedures along with issues not foreseen in the development of Appendix A have occurred which make the application of the regulation more difficult today.
. 11. While it may appear from the following discussion that Appendix A has not served its function, this is not the case. Most scientists l
and engineers agree that the Appendix shows great insight into l
the kinds of potential problem areas that should be considered in l
efforts to site and design a nuclear power plant. However, the methods and procedures set forth to achieve these objectives are the source of much of the debate.
- 12. Finally, there is a basic problem with the meaning of the word endings -ology and -graphy and the law:
-ology deals with the interpretive aspect of a given scientific a.
area.
b.
-graphy deals with description in a given discipline.
Some individuals would, since we are dealing with nuclear power plants, require that we,can only deal in realities. This is almost never possible in the early science area and causes major problems in the legal area where black and white conditions are the general rule and shades of gray are not easily tolerated.
H.
NRC Concern in the Earth Science Area is Mainly Two-Fold l.
Establishment of seismic design (SSE and OBE), determine if there is localization of earthquakes or high vibratory ground motion -
shaking.
i 2.
Assessing geologic hazards, ground rupture through capable fault -rupture of safety related systems. Also, concerns are given to hazards such as seismic sea waves and ground or foundation failure (landslidesandsubsidence).
a.
Damage to reinforced concrete structures at about magnitude six and higher.
.' I.
Methodology (for Paragraph H) 1.
Two levels of design protection (SSE and OBE).
2.
Determined by four conceptual elenants - tectonic province, tectonic structure, capable fault, and reasonable correlation of seismicity with geologic structure.
a.
Above carried out by:
(1)
If earthquake can be related (reasonable correlation or association) to geologic structure (tectonic structure, capable fault) within a given area (tectonic province) then:
(a)
Estimate potential energy release from all geologic structures in the region using all available seismological and geological informatien.
(b)
Estimate attenuation of energy during transmission to site (from closest point on structure).
(c) Characterize the frequency response spectrum at the site.
i (d) Specify the horizontal ground acceleration to be used for design purposes (SSE and OBE).
b.
Or:
(1)
If earthquake cannot be related (reasonable correlation) 1 l
to geologic structure (tectonic structure or capable l
tault) then go with tectonic province method which is mostimportantineast(paleotectonicandneotectonic features).
(a)
Establish the region (tectonic province) in which the occurrence nf earthquakes could have significant effect at the site.
6-(b) Determine the maximum potential earthquake in the tectonic province in which the site is located, based on geology and historical earthquake records.
(c) Assume the maximum earthquake intensity occurs at (under) the site.
(d) Determine maximum potential earthquake in adjacent provinces assume they occur on boundary at point closest to site, and calculate effect at the site.
(e) Characterize the response spectrum of the earthquake with the maximum potential occurrence at the site.
(f) Specify the horizontal ground motion to be used for design purposes (SSE and OBE).
(g) Other hazards - volcanism.
II.
DISCUSSION A.
Impact of Issues 1.
Delay.
2.
Manpower.
l 3.
Restrict advances in science and engineering by codification of procedures which are not state of the art.
Limits professional judgment and experience.
4.
Backfitting is difficult to determine because Appendix A lacks guidance on a quantitative measure of conservatism to be met.
l l
5.
Conflict betwan case-by-case approach of regulation and more generic concepts of early site review, limited work authorizations, and alternative site review.
6.
Uncertainty for applicants because of lack of clear guidance regarding what constitutes acceptability for various aspects and
7.
Safety margins difficult to ascertain in a rigorous sense because of professional judgment and experience (changing NRC reviewers a problem), and differing opirdons existing as to the adequacy of determinations and level of conservatism achieved.
B.
Tectonic Province is defined as "A Region of the North American Continent Characterized by a Relative Consistency of Geologic Structural Features Contained Therein."
1.
Staff thinks it's an area of uniform earthquake hazard as was original intent.
2.
Only geologic structural features are mentioned.
Use of geologic structure without regard for its geochronologic or seismologic significance has led to a variety of tectonic province schemes (both paleotectonic and neotectonic structures used to define boundaries).
3.
Concepts of physiographic province, geologic province and structural province related to, but confused with NRC's province.
The type of assessment called for in Appendix A does not adequately.
provide for vitally important factors bearing on the determination of a tectonic province and the ground motion at a site.
a.
Seismicity - this is recent tectonism. Patterns, frequency, and size important, but frequently not considered.
6 b.
Neotectonic (last 15 x 10 years) development of a region is important to the determination and assessment of a province.
California and in the. rest of world younger structuras and earthquakes are related.
Frequently, geologic structures hundreds 'of millions of years old are given more significance than they are due.
c.
Since the basic format was established (1969-1973 period) our understanding of intraplate seismicity and size of the data base has increased (platetectonics one important element notconsidered).
Hard to use this new information within out present regulatory framework.
' d.
NRC has not succeeded in developing a tectonic province siting map on which there is agreement within the earth science consnunity.
For example, use of a probabilistic procedure for assessing earthquake distribution does not appeal to some experts.
Appendix A terminology allows for more conservative assessments e.
than might be normally. determined in areas of "csmplex geology" and "high seismicity" (undefined relative terms) also "where geologic and seismic data warrant" (again, meaning open to despute).
f.
Appendix A also requires the most severe earthquake associated with structures and provinces be identified considering historical earthquakes that can be associated with the structures and provinces and "other relevant factors" (undefined as to meaning).
C._
Tectonic Structure is Defined as "A Laroe Scale Dislocation or
. Distortion of Within the Earth's Crust.
Its Extent is Measured in Miles."
1.
Definition given in Appendix is broad and little guidance is given as to how it is to be interpreted (in geology the broad architectural features of the earth's crust).
2.
Regulation implies that it may be buried or expressed at surface (accordingly, both descriptive and interpretively recognized).
Many disputes on this latter part of concept with site intervenors.
l 3.
Patterns of seismicity and rates of historical seismicity are not recognized in the regulation but are important in determining tectonic structure.
4.
Sometimes the distinction between whether or not one is dealing l
with a tectonic province or a tectonic structure is not clear (latter is less rigorously defined - requires no defined boundaries).
v
g.
5.
Appendix A does not define the degree of conservatism to be used in establishing a tectonic structure.
Staff thinks geophysical data, geological data, tectonic history, and seismicity to be valid tools for defining a structure and determining its currelation with seismicity..
6.
Guidance is not given in Appendix A for assessing the size of an earthquake that may be generated by a tectonic structure.
D.
A Capable Fault is Distinguished by Four Basic Elements:
(1)
Movement on a Fault Within Past 35,000 Years or Multiple Movements Within the Past 500,000. Years, (2) a Correlation (Direct Relationship)
With Macro-Seismicity, (3) Relationship, To ~a Knovn capable Fault and (4) for Non-Capability, a Structural Association With Geologically Old Structures.
1.
Term unique to Commission.
2.
Based mainly on geology and seismic observations in the western United States.
3.
Appendix A applies concept uniformly across U.S.
4.
Probabilistic analyses, calculations of recurrence values for earthquakes and fault movement, micro-earthquake monitoring, stress analyses and strain measurements are state-of-the-art tools not foreseen in Appendix A for assessing faults. Some argue that since they are not mentioned they cannot be used.
5.
Concept based on empirical knowledge of numerous active faults, not based on rigorous assessment of deformational activity.
6.
Specified numerical values (35,000, etc.) appear to be straight forward but in practice exact age data is difficult to obtain (radiometric or stratigraphic dates) - causing extensive professional judgment to be used (geologic history, denudation rates, fluid inclusions,etc.).
~
D
~-
l 7.
Recurrent movement criterion, difficult to use for faults in ranging from several inches to tens of feet - where most faults
(
occur (movementonce,twice,etc.).
l 8.
Numerical values (35,000 and 500,000) selected imply a certain rate of earthquake activity which may not necessarily correspond to that inferred from seismicity element of capable fault criteria (macro-seismicity). One GSB staff member came up with two magnitude 2 events /100 years for capability (might occur anywhere).
9.
The term macro-seismicity is unique to Commission and not defined.
Word's roots mean large or long seismicity.
Staff thinks this means large = earthquake size and/or rate of earthquake activity or long = persistency - in geologic sense. Also, it implies significant,.
sustained, coherent activity representing major deformational movement in earth's crust.
10.
If another fault is structurally related (attached) to a capable fault it must be considered capable - it's resonable to expect movement on one and is expected to produce movement on the other.
However, what about two parallel faults, properly oriented, in the same stress field? Staff thinks if one is capable the other might be capable too. Also, staff experience indicates that first relationship may be difficult to show. How conservative do you have to bei
- 11. Monoclinal flexture, not clear from Appendix A how this charac-teristic should be used in assessing the length of faulting, earthquake potential, or potential for surface displacement.
- 12. "Not withstanding" phrase in Appendiv A is not clear, words imply that you can have some elements of capability if pre-Quarternary and not be capable. Also, can be used to imply that faults that have no known Quarternary or younger tectonism should be considered capable if they have the characteristics of capability.
f
11 _
- 13. Above can also be used ta question whether 'or not it is the intent of the Appendix to require as extensive fault investigations in the eastern U.S.
- 14. Appendix A does not provide an explicit prohibition for use of a site with a capable fault which would require designing for surface displacement; however, in fact, the extensive investigations required a result in such a. prohibition. Alternatively, Regulatory Guide 4.7 states that sites within five miles of a capable fault are generally not suitable and that sites that include capable faults are not suitable for nuclear power stations.
E.
Reasonable Correlation of' Seismicity with Tectonic Structure and a Direct'Relationshio of Macro-Seismicity to a Capable Fault.
1.
What constitutes a reasonably correlation or direct relationship between earthquakes or macro-seismicity, and tectonic structure and capable faults, respectively, is not defined in Appendix A and no. guidance is given.
2.
Correlation = degree of equivalence, may range from a demonstrated
+-
causal relationship, to a close spatial proximity of earthquakes with tectonic structure, to an entirely interpretive relationship between the two. Staff thinks this means that a sound scientific basis must be established to correlate particular earthquakes with tectonic structure or to establish within the strength of seismicity data that an identified causative structure exists.
f l
Application of this requires interpretation which has been controversial in several instances. Some interpretations have required epicenters of earthquakes to fall on well-mapped, well-defined geologic stnicture and that a causative relationship be demonstrated (such precision is currently rarely obtained and it can cause a potential hazard to be overlooked because the above '
conditions cannot be rigorously met).
3.
Staff thinks that zones and clusters of seismicity are significant in eastern U.S. for evaluating areas at present day crustal instability, surface offset potential and high earthquake hazard
pountial. Many zones and clusters are clearly anomalous with respect to regional background seismicity, broad-scale geologic structure, and known tectonic history.
In some such cases they also can be related to geologic and geophysical data suggesting instability in the area.
4.
Microearthquake. surveys and stress measurements in identification and assessment of seismically active structures are not mentioned in Appendix.
5.
In showing that " macro-seismicity [is] instrumentally determined with records of sufficient precision to demonstrate a direct relationship with the fault Appendix A is not clear on " records of sufficient precision (how many, etc.)," " direct relationship" i
(right on fault-most events have several kilometers of scatter; and.makes no mention of using historical earthquakes).
F.
Specification of SSE and OBE Vibratory Ground Motion 3,
1.
Procedure.
a.
Taking an earthquake of some size magnitude or intensity..
b.
Assume the event to occur at some defined location relative to site.
c.
Detemine an acceleration level at the site representative of the event.
d.
Specify design ground motion for that acceleration level representative of the postulated earthquake description.
G.
Other Less Significant Issues 1.
(SSE) Appendix A calls for magnitude using the Richer +
Scale - other scales are used in certain parts of the country.
2.
Appendix A permits the earthquake size of historical events to be expressed as an intensity value on the Modified Mercalli Scale.
This scale is highly subjective - skills, objectivity, and biases effects results. One must continually go back to original data l
sources, which is frequently not done (acceptance at face value).
3.
Concerning methodology of taking largest historical earthquake associated with a tectonic structure or a tectonic province, the regulation implies that the earthquake rather than the intensity of the events is moved to the site.
If this is the case then the site would always be in the nearfield.
In practice intensity is used.
4.
Considerations of nearfield effects is not stated in Appendix A as a requirement; however, Regulatory Guide 1.60 implies that it should be considered.
5.
Raising minimum acceleration level of.lg to.2g has been suggested (ACRS) - to provide additional conservatism, help with backfitting problems, etc.
6.
Appendix A requires ground motion to be represented by response.
spectra corresponding to accelerations at the foundation level
(.does this mean some elevation below ground surface or the strata upon which the plant is founded - latter interpretation followed). Additionally, almost all of data on ground motion are from measurements at or near ground surface. Some soil structure interaction finite element techniques developed to analyze variations of motion with depth produce unrealistic results when used at foundation depth.
7.
(OBE) concept interpreted differently by scientific and engineering disciplines.
i Geology / seismology - probabilistic assessment over 40 year l
a.
life span of a plant of an earthquake can be less than 1/2 l
the SSE (staff has accepted less).
. b.
Engineers - earthquake expected during lifespan at plant whose likelihood is great enough that economic considerations would dictate that a structure must be designed to accomodate it.
Not less than 1/2 half the SSE.
c.
In terms of capital investiment 300 to 500 years interval sought.
d.
For most of U.S. data indicate that one-half the SSE does not correspond to a reasonable 40 year event, but rather to a 300 to 1,000 year event. Also, in seism Mally active areas of the !I.S. one-half the SSE may not represent a conservative estimate of what mipt be expected because of the higher frequency of occurrence.
e.
In accepti.ng less than one-half, the SSE staff was following of Appendix A, but used probabilities not deterministic methods of SSE.
f.
Regulation does not specify what constitutes exceedance at OBE for shutdown and inspection purposes.
(1)
Is it exceedance of the freefield OBE acceleration level?
l l
(2) Exceedance of design response spectra at different elevations in the plant?
(3). Exceedance of response spectra at a si.ngle frequence of several frequencies by a certain amount?
8.
No specific criteria fer inspection in event an OBE has been developed.
9.
If probabilities are used can set OBE so low that large areas having an OBE value exceeded duri.ng an earthquake could experi-ence blackouts.
15 -
H.
Engineering Issues
- ~ ~
1.
The relatien of the OBE to SSE.
2.
The OBE in controlling design.
- 4 3.
The use of probability for calculating the OBE and SSE.
4.
The use of probability for considering comninaedtef Of.,1 pads.
~
5.
Use of explicit time histories.
I 6.
Defining the input motion in the free field at finished grade.
7.
Use of seismic scram instrumentation.
~
~
8.
The use of instrumentation for determining OBE exceedance and recuired time interval to shutdcwn for inspection.
9.
Use of other vibratory ground motion parameters besides that of.
~
acceleration.
Need for aftershock engineering specifications.
,+i 10.
- e :..
3.e 11.
Hydrology in the r.egulation since its covered elsewhere.
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