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UNITED STATES OF AMERICA
NUCLEAR REGULATORY COMMISSION
- - -
BRIEFING ON PART 100 FINAL RULE
ON REACTOR SITE CRITERIA
- - -
PUBLIC MEETING
Nuclear Regulatory Commission
One White Flint North
Rockville, Maryland
Wednesday, June 12, 1996
The Commission met in open session, pursuant to
notice, at 10:00 a.m., Shirley A. Jackson, Chairman,
presiding.
COMMISSIONERS PRESENT:
SHIRLEY A. JACKSON, Chairman of the Commission
KENNETH C. ROGERS, Commissioner
GRETA J. DICUS, Commissioner
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STAFF AND PRESENTERS SEATED AT THE COMMISSION TABLE:
JOHN C. HOYLE, Secretary of the Commission
KAREN D. CYR, General Counsel
JAMES TAYLOR, EDO
THEMIS SPEIS, Deputy Director, Office of Nuclear
Regulatory Research
ANDREW MURPHY, Chief, Structural and Geological
Engineering Branch, RES
LEONARD SOFFER, Technical Assistant, Office of the
EDO
THOMAS KING, Deputy Director, Division of Systems
Technology, RES
FRANK MIRAGLIA
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P R O C E E D I N G S
CHAIRMAN JACKSON: Good afternoon everyone. The
purpose of this meeting is for the NRC staff to brief the
Commission on a final rule to amend reactor siting
requirements in 10 CFR Parts 50, 52, and 100. This includes
the establishment of a new Appendix S to 10 CFR Part 50 for
use by future applicants.
The Commission recognizes that much effort has
been expended on these rule changes which were originally
published, I understand, for public comment in 1992.
I have requested the staff to respond to several
questions which I had given after a Chairman's briefing in
order to clarify aspects of the proposed rule changes.
In general, the questions were related to three
aspects of the proposed rule changes.
First, the application of Part 100 to operating
reactors and future use of the proposed rule changes. For
example, new source term applications.
Second, the difference of opinion between Research
and NRR regarding the time frame for when the new source
term should be applied, namely, the question of the first
two-hour period or worst two-hour period.
Third, the less prescriptive aspects of the new
rule. For example, population density and the changes to
the operating basis earthquake.
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The Commission is interested in discussing how
these issues are dealt with in the proposed final rule
before the Commission, and we are also interested in your
consideration of input from the Advisory Committee on
Reactor Safeguards regarding these issues.
The Commission realizes the significance of the
Part 100 rule. One of the briefing papers referred to this
rule as the regulatory pillar for reactor safety and public
health and safety, a pedigree of those features inherent in
the design that prevent or mitigate consequences of
accidents. That shows you that all these things are read
deeply.
We look forward to discussing the aspects of these
rule changes with you today. I understand that copies of
your presentation are available at the entrance to the
meeting.
Do my fellow Commissioners have any opening
comments?
COMMISSIONER ROGERS: Nothing.
COMMISSIONER DICUS: No.
CHAIRMAN JACKSON: Mr. Taylor, please proceed..
MR. TAYLOR: Good afternoon. With me at the table
are frank Miraglia, Andy Murphy, Themis Speis, Len Soffer,
and Tom King.
The staff considers this to be an important rule
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since it reflects not only the experience gained over more
than 30 years in siting and licensing of over 100 nuclear
power plants, but also because it incorporates major
advances in our understanding of the earth sciences and
reflects significant research insights in the area of
fission product releases resulting from severe accidents.
The rule also states basic reactor site criteria
and makes explicit the Commission's longstanding policy that
reactors should be located away from very densely populated
centers.
With that, I will ask Themis Speis to continue.
MR. SPEIS: Thank you, Mr. Taylor.
Chairman Jackson, Commissioners. I don't want to
repeat what has been said, but we will be able to give you
some of the salient aspects of this proposed final rule. Of
course the details are described here and we will be
addressing the questions that Chairman Jackson raised. We
are asking for approval from the Commission about this as a
final rule.
[Slide.]
MR. SPEIS: The first viewgraph shows the outline
of the presentation.
I will briefly go over the chronology of the
events that have brought us here today. Also, I will give
you an overview of the present rule.
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Then we have broken the presentation down into two
parts, one covering the seismic aspects and the other one
covering the radiological aspects.
As you can see, under the seismic aspects we will
cover the seismic and geologic siting criteria, the use of
probabilistic seismic hazards in determining the design
basis ground motion, and also will address the earthquake
engineering criteria.
Then we will go to the radiological part of the
rule and we will discuss in some more detail some of the
major developments and experience in reactor siting and
explicitly address the proposed revisions and then give you
the final elements of the rule that we are asking permission
from the Commission to publish.
[Slide.]
MR. SPEIS: The chronology.
Some of these things will be discussed later on by
Len and Dr. Murphy. I just want to give you kind of a brief
capsule.
As has been said already, this may be one of the
oldest. I will defer that to our general counsel if that is
the oldest or one of the oldest. That was back in 1962.
Then, 11 years later, the Atomic Energy Commission
put out Appendix A, which dealt with the seismic issues.
Both of these rules where when the AEC was in charge.
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In 1990 we came up with a plan to revise Part 100,
but the first proposed revision went out in October 1992.
We had grandiose ideas at that time of decoupling, siting
from design, and as you will hear later on from Len, it
didn't quite materialize that way because of the extensive
comments that we received.
The proposed rule was withdrawn in 1994, and then
the second proposed revision was issued for comment in 1994.
Here we are in front of you to discuss the final
rule.
[Slide.]
MR. SPEIS: I think it is very important to
provide the context of phase 1. This is viewgraph number 4.
I hope you see the color copy in front of you.
For background, I would like to say that from the
knowledge and the insights that we have gained from
extensive research on severe accident processes and
phenomena as well as the many risk studies that have been
performed we have learned that risks are dominated by severe
accidents, that is, core melt accidents where the
containment has either failed or bypassed. Therefore, one
might ask why these risk insights have not been totally
taken into consideration in this proposed rulemaking but
instead this rulemaking only partially addresses the
insights gained from severe accident research.
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When I am talking about partially, we are
addressing the behavior of the release of radioactivity as a
nuclear power plant undergoes a severe accident. Also, it
is fair to say that the distance itself, which is addressed
in the rule, which Len will talk about, takes severe
accident into consideration to some extent.
The answer is that the final rule which we will be
discussing today is the first step in our overall plan to
address this issue. That is the upper part of the drawing.
The middle part shows the insights, the technology
that went into the final rule that we will be talking about
today.
The later part, step 2, is something else that
will be coming in the future. This is taken completely into
consideration, the severe accident challenges. As all of us
know, a severe accident has two attributes, the radioactive
part and the energy part, the pressures and temperatures.
So right now we are only taking into account the radioactive
part.
Those other attributes of a severe accident
already have been considered in the staff's review of GE
advanced boiling water reactor and the Combustion
Engineering System 80+ design. Those things now are going
through the certification process.
We already have put out an advanced notice of
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proposed rulemaking to codify generically the severe
accident challenges into our regulations, but the Commission
told us back in 1993 in an SRM to wait for the outcome of
the certifications where severe accident considerations are
considered on a plant-specific basis instead of generically,
and then we will come back and see how and to what extent we
can address the totality of severe accident challenges, that
is, the radioactive part and the loads part, generically in
Part 50 or Part 100.
I know that when you people discussed this issue
with the ACRS they raised this question. Also, when this
rule was reviewed by the CRGR in their letter to Mr. Taylor
they raised this question. But I want to make sure that you
have the complete picture in front of you now.
[Slide.]
MR. SPEIS: With that, I will summarize the
current rule.
Basically, the current rule requires that a
determination be made of an exclusion area which is
immediately around the reactor. No residents are allowed in
it.
Also a determination has to be made of the low
population zone which is outside the exclusion area. Even
though it may contain some residents, no densely populated
centers are allowed.
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There is, of course, the population center
distance, which may be no closer than one and one-third
times the low population zone radius.
The way the exclusion area and the LPZ are
determined is a postulated source term is assumed to go into
the containment, to exist in the containment
instantaneously. It is constant; it's flat; it does not
have the time behavior that the new source term has. Then,
by using that source term and the criteria of 25 rem to the
body and 300 rem to the thyroid, one determines the
exclusion area size and the LPZ radius.
There are no numeric criteria in the rule itself,
but there is guidance in reg. guides 1.3, 1.4, 1.145, and
4.7, and 4.7 are the reg. guides that contain the .4 miles
as the distance between the reactor and the exclusion area.
The present Appendix A specifies seismic and
geologic site criteria.
With those brief remarks, I would like to turn it
over to Dr. Murphy, who will go forward and discuss the
seismic aspects of the rule.
MR. MURPHY: I will start on page 7.
[Slide.]
MR. MURPHY: My presentation will include a
description of the reasons why we got involved in the
revision to Appendix A, the objectives to that revision, and
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then I will touch on the highlights both in the earth
sciences and in earthquake engineering aspects of it.
As noted already, Appendix A has been around since
1973 and since that time there have been significant
advances in both the earth sciences and seismic engineering.
Within the earth sciences the two items that are
of particular note in my mind are the advances in the use of
probabilistic techniques to keep track of the uncertainties
that are involved in the parameters in setting out a safe
shutdown earthquake ground motion, which is the parameter
that we are looking for here, and also in the occurrence of
ground motions in excess of one G that have been observed
principally in the last five to ten years.
Under the seismic engineering we are looking at
advances in well studied after shock studies, I will call
them, where we have had an opportunity to go in and see what
damage has occurred to industrial facilities and then to
factor that into use for critical facilities such as nuclear
power plants.
A second item would be that the current regulation
contains requirements as well as regulatory guidance. Part
of the difficulty with the guidance actually is that it is
in the rule and in a number of cases it has been treated as
if it were actually requirements, and that has led to some
difficulties within the licensing arena.
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The third item is the conflicting interpretations
that are given to some of the terminology that is used
within the current rule. This would be terms like tectonic
province or capable fault or understanding what micro and
macro seismicity was all about. Here we have ended up with
an extremely time-consuming and protracted licensing
process.
Another item of specific note are the difficulties
that have been associated with the operating basis
earthquake definition and requirements. The current
regulation has in effect three definitions of the operating
basis earthquake, and these have been in a number of cases
conflicting definitions.
Another note here is that we have both the
operating basis earthquake and the safe shutdown earthquake
ground motions that are used for design. It has occurred in
a number of cases where the operating basis earthquake has
controlled factors in the design process. We found that
that is not appropriate.
Another requirement associated with the operating
basis earthquake is that if the operating basis earthquake
is exceeded, if the ground motion is exceeded at the power
plant, the plant is required to shut down. It had been the
staff interpretation for a long time that this was a
decision that was made by the licensee, but there had been a
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legal determination that this was not actually the case and
that if an operating basis earthquake happens today it is
incumbent upon the staff to require the utility to shut
down. There is no guidance at this stage on exactly what
exceedance means, and this has led to difficulty in a number
of cases with small nearby earthquakes producing apparently
large accelerations that in fact were non-damaging
accelerations.
[Slide.]
MR. MURPHY: On viewgraph 8 we look at the
objectives of the proposed revision. To a large extent
these mirror the reasons why we undertook the revision.
The first one was the decoupling of the siting
requirements from the design and engineering requirements.
This was initially undertaken to facilitate Part 52
applications. For the seismic case we have been able to
decouple the siting from the engineering requirements. The
siting requirements are contained within the new section
100.23 and the engineering requirements are in Appendix S of
Part 50.
We have also moved the detailed guidance from the
regulation to a series of reg. guides so that this guidance
would be available and it would actually be guidance rather
than additional requirements.
We have updated the technical requirements in the
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regulation to reflect the knowledge gained in the last 20
year or 25 years or better. Again, for the earth sciences
this has principally been the introduction of the option to
use probabilistic seismic hazard analysis techniques.
We have redefined the operating basis earthquake
and are providing guidance on restart after an OBE triggered
shutdown. We are also providing guidance on what is an OBE
and when exceedance has occurred.
[Slide.]
MR. MURPHY: This viewgraph highlights the
requirements that are proposed to be in the regulation for
geological siting criteria. The current regulation amounts
to approximately eight pages in the Code of Federal
Regulations. The new streamlined section 100.23 is now
about a column or a half a page in that document.
We have maintained the four items that we felt
were specifically critical to the requirements. That is the
requirement for investigation of the geological,
seismological and geotechnical characteristics of the site,
guidance on how these investigations to be carried out are
included within the reg. guide 1.165.
We have provided guidance on determining the safe
shutdown earthquake ground motion. Another significant
point there is that we have provided guidance on carrying
out the required uncertainty analysis with making this
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determination.
We have maintained a requirement to investigate
the potential for surface deformation and for the occurrence
of seismically induced floods or water waves. So indeed we
have taken a fairly cumbersome and detailed document and
reduced the requirements in the regulation itself to a very
streamlined document.
[Slide.]
MR. MURPHY: The next viewgraph touches on the
earthquake engineering aspects of this revision. Very
definitely, the most important thing that we have done in
this revision is to redefine the operating basis earthquake.
In redefining this one we have provided an option to any
applicant.
The first is that if the applicant chooses to have
the OBE equal to or less than 1/3 of the SSE, there is no
explicit requirement for design or response analysis. This
alleviates a considerable burden on the applicant.
If the applicant chooses to have an operating
basis earthquake larger than 1/3 of the SSE, they are
required to in effect go through the same analysis that is
on the books today. An applicant might choose to have an
operating basis earthquake larger than 1/3 for economic
reasons, to balance the cost of potentially having to shut
down if an operating basis earthquake occurs versus the
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up-front costs of carrying out the OBE analysis according to
the various codes.
The next item within the earthquake engineering
aspects is that we have now taken care of the lack of
guidance that has been out there for determining whether or
not an OBE has been exceeded and what the plant operator has
to do in shutting down the facility, and then providing
guidance on what has to be done after the facility has been
shut down to bring it back on line.
The two documents that provide this guidance are
endorsements of documents prepared by the Electric Power
Research Institute.
[Slide.]
MR. MURPHY: The last page in my viewgraphs,
number 11, is a list of the regulatory guidance that we are
providing to go along with this new regulation.
The first one is a fairly comprehensive document
that tells how to carry out the required geological and
seismological investigations and then how to proceed with
the determination of the safe shutdown earthquake and how,
if the applicant selects to go this route, to use the
probabilistic techniques to track the uncertainty that has
been involved in determining the safe shutdown earthquake
ground motion.
The next document is a revision of the Standard
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Review Plan Section 2.5.2, which outlines, as it says here,
the staff duties in carrying out a review, including use of
the probabilistic procedures.
The next two standard review plan sections, as it
says here, have conformable changes.
The next regulatory guide is a revision of an
existing guide that tells the applicant about what kind of
seismic instrumentation we expect to be at the plant.
The next two reg. guides are the ones I referred
to just a while ago about the plant shutdown procedures for
exceeding the OBE and then the plant restart facilities.
If there are no questions, I will turn it back.
CHAIRMAN JACKSON: There are questions. I want to
be sure that the Commission understands what is to be in the
reg. guides versus in revisions to the regulation. I am
going to ask you about some areas that I am interested in.
The definitions of very densely populated and low
population density, where are they? Are they in the rule or
are they in the reg. guides?
MR. MURPHY: I would defer that question to Len
Soffer. We do not address them in the seismic portions.
MR. SOFFER: We are getting into the radiological
aspects, Madam Chairman.
CHAIRMAN JACKSON: If you want me to wait, then
I'll wait.
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Let's talk about the safe shutdown earthquake.
You kind of talked about the guidance is primarily
probabilistic. Can you be a little more explicit?
MR. MURPHY: Yes, I can. What we have suggested
through the regulatory guide is that the applicant carry out
probabilistic seismic hazard analysis. What this in effect
means to start with is that the applicant has a choice of
using the EPRI or the Livermore techniques for carrying out
an analysis. Those techniques are acceptable at this stage
because the staff has already examined the databases and the
computer codes that are used for those techniques.
If the applicant chooses, they can go and use in
effect their own probabilistic analysis techniques. The
only requirement would be that they would have to be
reviewed by the staff before the results would be accepted.
CHAIRMAN JACKSON: How do they migrate from the
use of EPRI and Livermore techniques to the actual selection
of a safe shutdown earthquake?
MR. MURPHY: Let's step through the Livermore
process, and it would be very similar to the EPRI process.
Basically, they make the calculations and then carry out a
thing we call de-aggregation, which is to find out what
rings or annuli around a site with different magnitude for
each ring, how much contribution they make to the ground
motion at the site or to the seismic hazard at the site.
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The applicant may carry out a set of calculations
looking at the contribution from an annulus that is from 25
to 30 kilometers from the site with magnitudes from 5 to
5-1/2 and then from 5-1/2 to 6 and look at the contributions
that these would then make to the ground motion at the site,
hazard at the site.
On this basis the applicant will in effect graph
or plot this information, some of it in a computer format,
so that they are able to tell what earthquake would control
the ground motion at the site. This would then be
equivalent to the magnitude and distance pairs that we in
effect use currently. The significant contribution, the
ground motion for a particular site may come from a
magnitude 5.3 earthquake at about 25 kilometers from the
site.
The applicant then would use this information to
develop and scale a spectra that would describe the ground
motion, and this spectra would be the spectra that would be
used to judge whether or not the design spectra for the
facility was enveloped by this probabilistically determined
spectra. In effect, if it passes, the design spectra that
went along with the plant would be acceptable.
CHAIRMAN JACKSON: I'm not particularly familiar
with these techniques, but the techniques to which you
refer, they have included in them some kind of uncertainty
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analysis that helps to provide the envelope that then
propagates back into the design criteria?
MR. MURPHY: That's correct. The probabilistic
techniques provide a vehicle for carrying the uncertainties
about the various parameters on through the process so that
we can put bounds on the magnitude and distance pairs that
we achieve and also the bounds on the spectra that are used
to check the design spectra.
CHAIRMAN JACKSON: In doing that bounding, are
there confidence intervals that we specify or that would be
specified?
MR. MURPHY: There would be confidence bounds that
would come out of the analysis, that would go along as part
of the analysis.
CHAIRMAN JACKSON: But we don't have any that we
say are required?
MR. MURPHY: No, we do not.
CHAIRMAN JACKSON: Given whatever those confidence
intervals are, the design in the end has to accommodate
that; is that the point?
MR. MURPHY: That's correct.
MR. SPEIS: Chairman Jackson, on the SECY paper we
briefly summarize the seven steps that we go through. If
you and the Commissioners want to hear more about it, we can
go through these.
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CHAIRMAN JACKSON: Dr. Murphy has answered my
questioned.
MR. SPEIS: We knew that was an important part of
this and we tried to highlight it in pages 8 and 9 of the
SECY paper.
CHAIRMAN JACKSON: Thank you. Why don't you go
on. I'm probably going to come back to you on some of this
later, but I want to hear the full story.
MR. SOFFER: Thank you.
Viewgraph 13, please.
[Slide.]
MR. SOFFER: I would like to briefly describe the
experience that we have in reactor siting in this country
and the role of reactor siting.
Virtually every power reactor in the United States
has been sited using Part 100. The construction permit for
Big Rock Point was granted before Part 100 was promulgated.
However, the operating license was issued after Part 100.
At the present time there are 110 operating
reactors in the United States on 69 sites. There are about
2,000 reactor years of U.S. operating experience. However,
this doesn't constitute the entire base of our experience on
reactor siting.
It's important to recognize there have been about
an additional 20 reactor sites approved but where there are
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presently no operating reactors, where operating reactors
have been decommissioned or shut down. There are about ten
sites that were reviewed but were not approved for a variety
of reasons, some of them seismic, some of them population
considerations, a number of other considerations. Even this
does not represent the entire base, because there are a
number of sites that I haven't quantified here where the
review process was ongoing when the review terminated and
consequently there was no decision.
Consequently, we have to recognize that there is
very substantial basic siting experience that exists in the
United States and numerous risk studies that have taken
place since Part 100 was issued. These all indicate to us
that the primary factors that influence public health and
safety are reactor design, construction and operation.
Nevertheless, the siting factors are important for
assuring, along with reactor design, that radiological doses
from normal operation as well as postulated accidents would
be acceptably low, that natural phenomena and potential
man-related hazards in the site vicinity are described and
are appropriately accounted for in the plant design, that
the site characteristics are amenable to developing
emergency plans and adequate security plans, and finally, to
maintain the Commission's policy of siting reactors away
from densely populated centers.
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If I can go on the next viewgraph.
[Slide.]
MR. SOFFER: Part 100 has a number of important
aspects, and it is important to recognize those.
First of all, it functions as a siting rule. It
determines the important site parameters that are in the
rule itself: The distance to the exclusion area boundary,
the low population zone outer radius and the population
center distance that provide acceptable separation distances
between the plant and various members of the public.
In addition to its acting as a siting rule, it is
important to recognize that it also serves as an important
performance measure of the accident mitigation capability of
the plant. It sets the requirements for things like
containment leak rate, for the performance measure of
fission product systems; it serves in a way as the
radiological challenge for control room habitability for the
operators, and a number of other important areas.
It also serves as one test of adequate protection
of the public for a postulated degraded core accident and
fission product release into containment as long as
containment remains intact. It is important to recognize
that before the Commission's safety goal Part 100 in a sense
was one of the measures of adequate protection of the public
by virtue of the fact that a postulated accident was
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postulated and evaluated considering the site as well as the
plant design.
It is also important to recognize those things
that Part 100 doesn't do. It does not determine the
containment design. This is done by the pressure and
temperature conditions of either the loss of coolant
accident or the steam line break accident, whichever one is
more limiting. So the pressure and temperature conditions
associated with a severe accident, as was mentioned by
Dr. Speis, are not considered in determining the containment
design.
It does not control severe accident risk. That
risk is dominated by core melt accidents where containment
fails or is bypassed, but neither does Part 100 totally deal
with design basis accidents. It does reflect consideration
of severe accidents by virtue of the population center
distance criteria.
It has been very clear from the statement of
considerations going back over 30 years that the population
center distance criteria was added as a reflection of
accidents that could occur beyond the design basis accidents
that were contemplated at the time. This has been one of
the reasons why the staff has continued to issue population
guidance in the form of regulatory guides and kept this
aspect in the forefront.
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It also reflects consideration of severe accidents
in the nature of the postulated fission product release. It
is intended, as the regulation says, to represent a
substantial core meltdown with appreciable release of
fission products. Originally this was given in an
accompanying document, TID 14844, that was issued along with
the rule, and as our knowledge of severe accidents has
improved over the years we are supplementing this with a
revised accident source term formulation as well.
CHAIRMAN JACKSON: Before you go on, let me ask
you this question and clarify something. You say that Part
100 does not determine containment design and the fact that
pressure/temperature conditions of a LOCA or steam line
break determine that, but your second bullet says that it de
facto determines containment performance, because you are
saying it does set requirements for containment leak rate;
is that correct?
MR. SOFFER: That's right. It does set
requirements for allowable containment leak rate. That is
correct.
CHAIRMAN JACKSON: So while it does not specify
containment design, it de facto specifies containment
parameters?
MR. SOFFER: Yes.
CHAIRMAN JACKSON: I will come back to this with
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another question. Thank you.
MR. SOFFER: Let's go on to viewgraph 15.
[Slide.]
MR. SOFFER: The reasons for revising part 100
are, first, to facilitate along with the issuance of Part 52
its use of standardized design and early site permits, as we
mentioned earlier.
Second, there was a recognition that the dose
calculation was in effect regulating plant design in some
ways more than siting in terms of regulating allowable
containment leak rate, as we just mentioned, fission product
cleanup system performance such as sprays and filters,
isolation valve timing, drawdown time on a secondary
containment annulus. All of these things were being
influenced and strongly determined by the nature of the Part
100 calculation.
We also wanted to revise Part 100 to incorporate
some of the changes in siting practice and to allow for
updated accident source terms, to make explicit the
Commission's policy of requiring plants to be away from
densely populated centers; to make explicit the fact that
the staff has evaluated man-related hazards in the site
vicinity, and yet this is not explicitly mentioned in Part
100; to require that sites be amenable to the development of
adequate security plans and emergency plans; and to update
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the dose criterion to be more in accord with modern
radiation protection practices and to be amendable with the
development of a revised accident source term.
In addition, as Dr. Murphy mentioned, there were
significant advances made in seismic analysis and earthquake
engineering. Basically this effort was initiated about 1990
with a staff recommendation to decouple siting from design.
[Slide.]
MR. SOFFER: This brought us to this first
proposed revision that was issued in 1992. In this revision
there was a genuine effort at decoupling. There were no
dose calculations proposed for siting. There were numerical
criteria for the exclusionary boundary size and there were
numerical criteria on population density that were included
and specified in the rule itself.
Subpart A would apply to current plants and
Subpart B would apply to future plants. There were no
proposed changes made for current plants.
This proposed revision elicited some very, very
strong comments from a number of people, the major comment
of which was that almost everyone -- in fact, I should say
everyone did not favor the idea of eliminating dose
calculations for siting purposes.
Generally speaking, industry felt that this
provided a flexible performance-based measure and they
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wanted to see it retained.
The public interest groups felt that it provided a
valuable piece of insight and risk knowledge and felt that
this should be retained by the Commission in its criteria.
In addition, a number of people felt that the rule
itself was too prescriptive, that it was highly
conservative, and that the incorporation of fixed numerical
criteria in the rule was incompatible with the concerns of
many in the international community. As a result, with
consultation with the Commission at that time, the rule was
withdrawn in March of 1994.
The second proposed revision was issued in October
of 1994, and source term and dose criteria were relocated to
Part 50.34 and retained for siting.
We proposed a new section 100.21, which would
contain basic non-seismic criteria but without numeric
values.
Numerical values for population density are in
proposed Regulatory Guide 4.7.
And the dose criterion was changed from 25 rem
whole body and 300 rem thyroid to 25 rem total effective
dose equivalent, TEDE, and evaluated over any two-hour
period.
[Slide.]
MR. SOFFER: Going on to the next viewgraph, I
. 29
want to give you some of the highlights of the public
comments. The more detailed discussion of the highlights
was provided to the Commission in a memorandum from
Mr. Taylor sometime ago.
The industry comments were generally favorable but
there were significant concerns in a number of areas. All
of the industry felt that the use of TEDE was an appropriate
measure but there was concern that the dose criterion of 25
rem was more restrictive than the current criteria, although
there was one comment that it was appropriate.
In the industry comments, there was no need felt
for an organ capping dose or a separate organ dose.
And there was also a belief that the use of any
two-hour period to evaluate the dose was confusing and
illogical and introduced some inconsistencies.
The one public interest group that did comment
found the rule generally unfavorable, believed that it was a
significant retreat from decoupling, considered the use of
TEDE acceptable and 25 rem appropriate, but believed that
there should be a dose to any single organ, but no comment
on the dose evaluation period itself.
CHAIRMAN JACKSON: Let me stop you there. I note
that you are moving the dose criteria to Part 50 for future
applicants, but it has been stated that the dose criteria
are used not only for reactor siting but to assess whether
. 30
the plant continues to meet its design basis. How do you
handle that dichotomy in terms of the use of the criteria
and whether or not it should be highlighted at least in some
descriptive way in regulations for operating reactors?
MR. MIRAGLIA: The intent of the final rule is to
apply for only future designs.
CHAIRMAN JACKSON: I appreciate that. What I am
saying is, if it is currently being used to assess whether
currently operating reactors continue to meet their design
bases, then de facto are you not using them for operating
reactors?
MR. MIRAGLIA: Our current plan with respect to
the application of the new source term insights for
operating reactors is that we are working with the industry.
The industry has proposed a framework for examining how this
new source term would be used for operating reactors.
As a way of background, the siting rule in Part
100 and our evaluation of plants that are currently
operating are based upon design-basis accidents that go back
long term into the regulations in our regulatory history.
That requires a very stylized analysis of these kinds of
accidents.
Because there were large uncertainties at the
time, the application of these stylized analyses had lots of
conservatisms in terms of release of material into
. 31
containment and how they were evaluated.
What we have done, consistent with the two phases
that Dr. Speis indicated, is to do an integrated review of
these changes of source term for the new designs. We have
done that substantially and it is completed for the ABWR and
the System 80+ in that we have examined that design against
required design-basis accidents.
We have analyzed the severe accident
considerations and insights against that design, which is a
robust design because of the conservatisms in that process
and superimposed those to say that the margins that we are
providing by the design-basis accidents are also sufficient
to consider severe accident considerations and accident
management. So it has been an integrated package for those
two designs.
That is an ongoing effort with respect to the
AP-600, the passive design, and the application of these
same kinds of concepts to operating reactors needs that kind
of integegrated approach: if we back off from certain
conservatism margins, what impact does it have in terms of
measuring the overall effectiveness of the design?
CHAIRMAN JACKSON: Apparently you already have
some applications from licensees who want to utilize the new
source term.
MR. MIRAGLIA: What we have done with those, Madam
. 32
Chairman, is we have expressed this concern of doing an
integrated review to fully understand it. As a result, NEI
has proposed a framework for piloting certain of these
potential uses so that we could take a look at what pieces
can we deal with, what is important for them on a priority
basis from an industry perspective, what pieces of those
source term changes the staff feels are firmly based on
science that we understand what the impact would be that we
could move at perhaps a faster pace, to evaluate that, come
to the Commission in the fall and say here is our plan for
implementing these changes for current reactors in an
integrated kind of sense. That's the current plan.
CHAIRMAN JACKSON: Would this be in any sense
taking you down a path of granting exemptions relative to
operating reactors whose licensees want to make use of the
new source term?
MR. MIRAGLIA: Since we haven't completed all of
that review, I think one of the products that we would like
to produce is what kind of changes would that be. Would it
be change in guidance only? It may have to be changes in
rules as well.
That is one of the things that we would try to
look at and propose to the Commission in this integrated set
of how we are going to look at the pilots, what do they
suggest in terms of what is the appropriate regulatory
. 33
vehicles to move forward.
We didn't want to do it on a piecemeal basis for
an individual plant because of what are the implications,
the full plethora of regulatory implications such as
exemptions, change in guidance, generic letters, or whatever
the case may be.
CHAIRMAN JACKSON: With the plan that you have in
mind or that you are going to be proposing, other than the
pilots, you would not be contemplating changes for existing
operating reactors until you have worked out the whole
plethora of the implications; is that correct?
MR. MIRAGLIA: That's correct. I think there have
been some instances where we have done some changes in terms
of timing which are clearly consistent with previous
Commission guidance that any changes we make need to be well
founded on the technology and the research that supports the
source term pieces, but to make major modifications and
changes to that, we would come forward with a plan to say
here's how we are going to work with the industry.
CHAIRMAN JACKSON: When you say changes, do you
mean exemptions or do you mean changes in framework?
MR. MIRAGLIA: I think what we are looking at is
modifications to the regulatory framework.
CHAIRMAN JACKSON: Let me go back to Mr. Soffer.
Has there been resolution of this difference of opinion
. 34
between NRR and Research with respect to the "any" versus
the first two-hour time frame?
MR. SOFFER: I will defer to Dr. Speis.
MR. SPEIS: I would say yes. The staff position
as presented in the SECY paper is that we will go forward
and recommend to the Commission any two hours.
I think the views were very clear. They were
expressed and clarified. Both of them lead to a safe
design. Our position dealt mostly with the issue of risk
versus design basis.
CHAIRMAN JACKSON: And "any" addresses risk?
MR. SPEIS: Yes. I think it was helpful to all of
us to put some of those things on the table. The Commission
has all the information. We will be happy whichever
direction the Commission decides to go.
MR. TAYLOR: Although we recommend "any."
[Laughter.]
MR. MIRAGLIA: I think Dr. Speis has accurately
characterized it. One is a risk; the other is design basis.
Since there is this design basis attribute left in the rule
in terms of the efficacy of the design, the worst would be
conservative.
CHAIRMAN JACKSON: So your unified position is
any; is that what you are telling us?
MR. TAYLOR: Yes.
. 35
MR. SPEIS: Yes.
CHAIRMAN JACKSON: It's important that you come to
some overall concurrence that makes sense as reflected in
the SECY paper, because you are asking the Commission to
make a decision based on that particular recommendation, and
it has implications relative to things such as emergency
planning, et cetera, and so it is very important that you
have clarified any issues here. This is your opportunity if
there is any additional clarification that needs to be made.
MR. MIRAGLIA: No.
CHAIRMAN JACKSON: Let me ask you about the 25 rem
total effective dose equivalent. There was an ACRS letter
that recommended that a careful definition of the TEDE
limits that are mindful of organ dose weighting factors
should be -- and some of this was referred to in some of the
public comments -- included in the final rule. The question
would be, is it clear that you recommend this particular
dose limit based on latent cancer fatality risk?
MR. SOFFER: Yes. We are recommending this based
on latent cancer fatality risk. We believe that this is
consistent with other Commission regulations in this regard.
The industry raised a point of apparent
contradiction in the sense of a conversion of 25 rem whole
body and 300 rem thyroid to a latent cancer fatality risk.
The staff computed that that would be approximately
. 36
equivalent to 27 rem, which we then rounded down,
admittedly, and said that was pretty near equivalent to 25
rem.
However, there are organ weighting factors in Part
20 which would make the 25 rem whole body and 300 rem
thyroid equivalent to 34, that is, the thyroid weighting
factor is 0.03. So 25 times one plus 300 times .03 would
give you 34. And the industry felt that there was a certain
amount of unfairness in this where one equivalency came to
27 and yet they were being asked to hold to 34.
There is a certain amount of inconsistency in
this. The organ weighting factors in Part 20, we have
discovered, are not entirely due to latent cancer fatality;
they include additional factors as well.
However, we do not feel that this is a more
restrictive criterion because the thyroid criterion has
always been the limiting criterion in licensing. The
highest dose that I can recall to which we have licensed a
plant was approximately 10 rem whole body and very close to
300 rem thyroid. When one equates this in a TEDE dose, this
comes out to approximately 19 rem. So the use of 25 rem
TEDE and converting the thyroid dose to a TEDE equivalent
is, practically speaking, a slight relaxation.
CHAIRMAN JACKSON: In effect it is a slight
relaxation relative to the potential thyroid dose; is that
. 37
correct?
MR. SOFFER: Yes, it is.
MR. MIRAGLIA: That's the rate for plants we have
examined to date.
MR. SOFFER: Although in theory it can be argued
that it is a restriction, in fact the thyroid dose has been
the more limiting and it acts practically as a slight
relaxation. Nonetheless, we feel that 25 rem is the
appropriate dose criterion, and that is what the staff is
recommending.
CHAIRMAN JACKSON: Thank you.
MR. SOFFER: If we can go on to number 18.
[Slide.]
MR. SOFFER: I would like to discuss some of the
elements of the draft final rule. We are proposing to
incorporate basic reactor site criteria in a new section,
100.21. I will just go over these very briefly.
Site atmospheric dispersion characteristics must
be such that doses for normal operation would be met and the
consequences of postulated accidents would meet the dose
criteria that are given in section 50.34.
Second, that potential hazards associated with
physical characteristics of the site as well as man-related
or human-related activities nearby must be shown to pose no
undue risk to any plant that would be located on that site.
. 38
The site characteristics must be such that
adequate security plans and measures can be developed and
adequate emergency plans can be developed.
And finally, that reactor sites should be located
away from very densely populated centers, that low density
areas are preferred, and that other sites may be acceptable.
CHAIRMAN JACKSON: Let me reinstate my earlier
question. Where are the definitions of these terms?
MR. SOFFER: If we can go to the next viewgraph,
we will get there.
[Slide.]
MR. SOFFER: The proposed population criteria are
in proposed revision of Regulatory Guide 4.7. I would like
to say that, first of all, these reflect some consideration
of severe accidents as well as reflecting conditions that
are reflective of U.S. geography and demography.
What we are saying is that sites where the
population density does not exceed 500 persons per square
mile out at any distance out to 20 miles, that is, circular
area out to 20 miles, are preferred sites.
The guide also states that reactors should not be
located where the population density is well in excess of
this above value.
Population projections are to be considered for
about five years from initial site approval and the
. 39
transient population is to be factored in.
Population growth after site approval is expected,
but changes should be factored into the site emergency
plans.
As you will see, and I hope I am answering your
question, the guide does not directly address the question
of what is a densely populated site; it rather addresses the
question by saying a population density below 500 people per
square mile is a preferred site and that sites above this
may be approved, depending upon safety or environmental
considerations, but sites should not be located in areas
that are well above this value.
It is interesting to recognize that the criterion
of 500 people per square mile in effect does represent some
kind of a standoff distance from cities of significant size.
For example, a population center of about 100,000
people in practical terms cannot be located closer than ten
miles because anything significantly closer than that would
get you above 500 people per square mile. Similarly, a
major metropolitan center of about a half a million or more
in practical terms would have to be at least 20 miles away.
These are the kind of standoff distances that the regulatory
guide basically sets in terms of preferred distances, but it
does not directly address the question of what is a densely
populated area.
. 40
In part this is due to the fact that from
demographic considerations it is very difficult to define
densely populated areas in terms of density. Cities vary
all over the place in terms of population density.
For example, cities in the Northeast tend to be
rather high in population density. The District of
Columbia, for example, has a population density of almost
10,000 people per square mile. Manhattan has a population
density of over 50,000 people per square mile. On the other
hand, Los Angeles has a population density that is just a
little over 2,000 people per square mile.
So trying to define a densely populated center in
terms of density has often not worked out very well, and the
guide does it in a much better way, in my opinion, by
describing the total number of people within a fixed
distance to the plant so that it tends to count all of the
people and gets around some of the obvious difficulties of
looking at political boundaries and subdivisions and
suburbs. So I think this is a better way of doing it.
CHAIRMAN JACKSON: But even that is not totally
disqualifying.
MR. SOFFER: Even that does not totally disqualify
it. That is correct.
CHAIRMAN JACKSON: Let me ask you one other
question. How is emergency planning actually to be factored
. 41
into site evaluation? In particular, I am thinking about
the Commission's Seabrook decision that said that emergency
planning is not site disqualifying. Is this going to
overrule that decision or conflict with it?
MR. MIRAGLIA: I don't believe so. I think the
emergency plans are looked at as another measure of defense
in depth beyond the regulations in terms of safety. The
defense in depth is the design, the siting of the facility,
meeting the safety goals. The emergency plan is another
aspect of defense in depth.
CHAIRMAN JACKSON: Would you provide the
Commission with an explicit answer to that question.
MR. MIRAGLIA: Sure.
MR. SPEIS: Yes.
CHAIRMAN JACKSON: The other question I have is,
how is the major accident for site evaluation purposes
chosen?
MR. SOFFER: I'm sorry.
CHAIRMAN JACKSON: When you are doing site
evaluations as opposed to design evaluations, how do you
choose or decide what a major accident is?
MR. SOFFER: The major accident is essentially the
same for both. It is a large fission product release into
containment. The current licensing basis was essentially
the source term formulation that was given in TID 14844.
. 42
For new plants we would probably propose using the revised
source term, which is an amalgam of severe accident
evolutions based on current plant understanding. But they
are basically the same. They represent a significant
degraded core accident, and the fission product release in
that bounds what was released into containment from Three
Mile Island, for example.
CHAIRMAN JACKSON: Okay.
MR. SOFFER: If we can go to viewgraph number 20.
[Slide.]
MR. SOFFER: There are a number of risk insights
that were developed as part of our thinking in developing of
this rule. I would like to mention several of them.
The staff investigated how the size of the
exclusion area would comport with meeting the Commission's
safety goal. We examined this using risk insights from the
NUREG-1150 plants.
It was determined that the prompt fatality
quantitative health objective, the QHO of the safety goal,
was met for all exclusion area boundary sizes of about 0.1
mile or greater. We did not look at any exclusion area
boundary sizes smaller than 0.1 mile. So for all the sizes
that we looked at from 0.1 mile or greater the prompt
fatality QHO was met.
The latent cancer fatality quantitative health
. 43
objective was also very easily met.
It is important to note that this size, 0.1 mile,
encompasses all of our current operating plants and all of
the sites that have been reviewed and approved by the staff.
Another important insight that comes out of this
is that the staff investigated the individual risk of
permanent relocation as a result of land contamination.
Using the insights from NUREG-1150, a severe
accident release was examined that was characteristic of our
present operating plants, and it was found that the risk of
permanently relocating an individual was low at all
distances, that it was less than about ten to the minus six
per year. This is a reflection of the low frequency of such
an event. And that this risk itself declined significantly
beyond about 20 miles. This is a reflection of the effect
that distance and wind direction have on mitigating such a
severe event.
Consequently this distance of 20 miles has been
factored into and considered in our revision of Regulatory
Guide 4.7, and this is why I said Reg. Guide 4.7 represents
not only the demographic considerations of the United States
but also represents and reflects some consideration of
severe accidents as well.
[Slide.]
MR. SOFFER: This is just finishing up the draft
. 44
final rules. I believe most of these have been mentioned
and I don't want to go into great detail.
As has been mentioned, the source term and dose
criteria for future plants have been relocated to Part
50.34.
It is also important to recognize that we have
left the licensing basis for current plants alone in Subpart
A of Part 100. So the dose criteria really appear in two
places.
Subpart A of Part 100 still contains 25 rem and
300 rem thyroid for current plants and does not change the
current licensing basis for those plants
Subpart B, which is applicable for future plants,
moves the dose criteria to Part 50.34 and changes it to 25
rem total effective dose equivalent, and that the dose to an
individual is not to exceed that value for any two-hour
period at the exclusion area boundary or for the course of
the accident at the low population zone.
I would also like to mention in conclusion that
both the Advisory Committee on Reactor Safeguards as well as
our management review group, the Committee to Review Generic
Requirements were briefed. ACRS recommended issuance of the
rule and CRGR indicated that it had no objection to
issuance.
The additional view by Research has been discussed
. 45
already. So unless there are any more questions, that
concludes my presentation.
CHAIRMAN JACKSON: Commissioner Rogers, do you
have anything?
COMMISSIONER ROGERS: Just a couple. Did you get
any comments from the international community on the new
version of the rule?
MR. SOFFER: Only indirectly. We received a
comment from one law firm that has a number of international
clients, and they were rather favorable and believe that
this revision addressed most of their concerns.
COMMISSIONER ROGERS: That is good. We did hear a
lot about the first version and it apparently did give some
serious concerns elsewhere in the world.
You referred on slide 20 to your investigation of
the safety goal versus the size of the exclusion area. How
available will those studies be?
MR. SOFFER: The study is a NUREG that is in draft
form and is presently undergoing a final review by the
staff. We should be issuing it fairly soon, I believe.
CHAIRMAN JACKSON: I think that also would be very
interesting to the international community. The fact that
you have come down to a tenth of a mile would probably give
considerable comfort to some of the people that were very
concerned about the earlier version of the rule.
. 46
That's all I have.
CHAIRMAN JACKSON: Commissioner Discus.
COMMISSIONER DICUS: On slide 19, I was curious
about how many of the current sites would meet this
population density preference.
MR. SOFFER: You mean the preferred number of 500
people per square mile?
COMMISSIONER DICUS: Yes.
MR. SOFFER: There are currently about six or
seven sites that are above 500 people per square mile.
These were all reviewed and approved before the current
version of Reg. Guide 4.7 was issued in 1975. The three
highest population density sites, of course, are Indian
Point, Limerick and Zion, but there are a few others. I
don't remember all of them by name, but I can get that
information if you wish.
MR. SPEIS: I would like to add something to that
point that is very important. These are the sites that the
previous Commission ordered special restudies specific to
Indian Point and Limerick and Zion.
CHAIRMAN JACKSON: If you look at the safety goal
versus the exclusion area, they are bounded by that.
MR. SPEIS: Yes.
MR. SOFFER: Yes.
MR. SPEIS: In some cases changes were made to the
. 47
design to enhance it and make it more robust for severe
accident challenges.
MR. MIRAGLIA: As Dr. Speis has indicated,
specific PRA reviews were done on those three facilities
that were mentioned.
CHAIRMAN JACKSON: This is a question I am not
sure you can answer, but you did speak of your 30 years of
license experience.
MR. MIRAGLIA: The Chairman is looking at me.
[Laughter.]
CHAIRMAN JACKSON: Mr. Taylor was looking down.
[Laughter.]
CHAIRMAN JACKSON: Is there any area that you
think is particularly litigious?
MR. MIRAGLIA: In terms of the old plants, we just
want to be cautious and make sure that we fully understand
the ramification of any changes. In terms of the new
plants, those processes have been open to the public and
those issues have been considered in the context of the two
design certifications and are ongoing for the AP-600.
CHAIRMAN JACKSON: I would like to thank you very
much for briefing the Commission. You have presented to us
a lot of information today that shows how much work you have
done to improve these regulations and to lay the groundwork
for future siting applications.
. 48
This is just a reiteration of an earlier point,
but I know you have placed the dose criteria in Part 50 for
future applicants, and that is appropriate, but particularly
with respect to the new source term tackling this issue for
operating plants remains open. As in some sense the ACRS
has said, we have been using the Part 100 dose criteria as a
surrogate for estimating certain of the consequences of
design basis accidents.
The Commission looks forward to the work that you
have outlined, Mr. Miraglia, and we would like you to come
back to the Commission for guidance as you proceed, also to
not proceed down a path where you are doing de facto
exemptions. I think the pilots will help you address a lot
of the issues.
Having said that, I think we would just urge you
to continue to work on the open issues so that the rule is
clear in how we apply it. I think the various reg. guides
should be ready and promulgated as close to the rule,
assuming we approve it, as possible, and that the rule can
accommodate future applications where appropriate.
I do believe that the improvements in the seismic
area are comprehensive and allow a clearer assessment of the
issues. Very important and something that all of us are
concerned about is that our regulations stay abreast of
advances in the science, but it is also important that the
. 49
clarifications of the type presented today, for instance,
clearly differentiating between safe shutdown earthquakes
and operating basis earthquakes, are addressed in a timely
manner.
I think we understand the rationale for moving to
the use of the TEDE, but I think we should continue to study
the issue of the organ dose weighting factors as used in
Part 20 and evaluate whether their use may be warranted
across the board for consistency.
Other than asking you for the specific answer to
the question with respect to how emergency planning is
treated and the fact that it is not site disqualifying a la
the Commission's earlier Seabrook decision is an important
answer you should provide to the Commission.
Are there any further comments from fellow
Commissioners?
[No response.]
CHAIRMAN JACKSON: We are adjourned.
[Whereupon, at 4:15 p.m., the briefing was
adjourned.]
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