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ORNL-TM-9780-V1.txt
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ORNL/TM--9780/V1
DE87 001615
NUCLEAR POWER OPTIONS VIABILITY STUDY
VOLUME],
EXECUTIVE SUMMARY
D. B. Trauger, Editor
. D. White
. S. Booth
. I. Bowers
. B. Braid
. A. Cantor
. C. Cleveland
. G. Delene
i Gat
T. Jenkins?
D. L. Moses
D. L Phung?
S. Rayner
I. Spiewak*
K. D. Van Liere’
=0 I
= C
-5
b
3
&
1The University of Tennessee
2Tennessee Valley Authority
3Professional Analysis, Inc.
4Consultant
5The University of Tennessee (now with
Heberlein Baumgartner Research Service,
Madison, Wisconsin)
Date Published - September 1986
Prepared for the
Office of the Assistant Secretary for Nuclear Energy
U.S. Department of Energy
Prepared by the
OAK RIDGE NATIONAL LABORATORY
Oak Ridge, Tennessee 37831
operated by
MARTIN MARIETTA ENERGY SYSTEMS, INC.
for the
U.S. DEPARTMENT OF ENERGY
under Contract No. DE-AC05-840R21400
e T
DISTRIBUTION OF THIS DOCUMENT 1S UNLIiwii izl
2P
-y
This report was prepared as an account of work sponsored by an agency of the
United States Government. Neither the United States Government nor any agency
thereof, nor any of their employees, makes any warranty, express or implied, or
assumes any legal liability or responsibility for the accuracy, completeness, or
usefulness of any information, apparatus, product, or process disclosed, or
represents that its use would notinfringe privately owned rights. Reference herein
to any specific commercial product, process, or service by trade name, trademark,
manufacturer, or otherwise, does not necessarily constitute or imply its
endorsement, recommendation, or favoring by the United States Government or
any agency thereof. The views and opinions of authors expressed herein do not
necessarily state or reflect those of the United States Government or any agency
thereof.
NOTICE
This report contains information of a preliminary naturc aad was
prepared primarily for internal use at the originating instaliation.
It is subject to revision or correction and therefore does not
represeat a final report. It is passed to the recipient in confidence
aad shouid nol be abstracted or further disclosed without the
spproval of the originating installation or USDOE Office of
Scieatific and Technical lnformation, Ouk Ridge, TN 17830
e A
o i AT R O D5
PREFACE
Systematic development of the information presented in this report was completed
in September 1985. Delays in funding and review have prevented timely publication. An
attempt has been made to include new information where substantial changes in programs
or designs have occurred, but it has not been possible to bring the report fully up to date.
Subsequent developments and events, particularly the Chernobyl accident, may alter some
of the findings.
111
AowoN
CONTENTS
Page
IN TR O DU T ON ... i ittt e et eeeie s eae e ereeeaaeearananns 1
CRITERIA FOR EVALUATION OF CONCEPTS ...oiiiiiiiiiiiiiiiiiiiiiieaen, 2
CONCEPT SELECTION AND CLASSIFICATION ...oiiiiiiiiiiiiiiiiciiiieeenee, 5
SUMMARY OF FINDINGS FOR CONCEPTS ..ottt 6
P U S . i i et e e e e aaaan 6
4.2 SMALL ADVANCED BWR. ... it e enraee e e 7
4.3 LMR CONCEPT ... i ettt e e ae, 7
4.4 MODULAR HIGH-TEMPERATURE GAS-COOLED
REACTOR (MHTR) SIDE-BY-SIDE CONCEPT..........ccoiiiiiiiiin.e. 9
UMMARY OF TOPICAL FINDINGS ..ot e ae 9
CONST RUCTION. ..t i i e aaeees 10
RGO (1% § (O T O U 11
REGULATION. ..t i e ettt et et e 12
SAFETY AND ECONOMIC RISK. ...ttt i eecaaane 13
NUCLEAR WASTE TRANSPORTATION AND DISPOSAL............ 14
PILOT STUDY OF MARKET ACCEPTANCE OF NEW
NUCLEAR TECHNOLOGIES. ..ot 14
5.6.1 General Conditions for a Future Nuclear Market................... 15
5.6.2 Public Acceptance Criteria. . .......ocvveiiiiiiiiiiiiiineiniinnenannnnn 16
5.6.3 Generalizations About the Electric Utility Industry................ 16
5.6.4 Constraining Preferences of Secondary Markets................... 16
5.6.5 Future Research Directions.........cccoviiiiiiiiiiiiiiiiiiniiiinnnn. 17
ACKNOWLEDGMENT S, ..t e e 18
LIST OF PUBLICATIONS RELATED TONPOVS. ..ot 20
REFERENCES . ... i i it it et r et e e e e e e aanaaas 21
ABSTRACT
Innovative reactor concepts are described and evaluated in accordance with criteria
established in the study. The reactors to be studied were selected on the basis of three
ground rules: (1) the potential for commercialization between 2000-2010, (2) economic
competitiveness with coal, and (3) the degree of passive safety in the design. The
concepts, classified by coolants, were light water reactors, liquid metal reactors, and high-
temperature reactors, and most were of modular design. Although the information
available is not adequate for a definitive evaluation of economic competitiveness, all of the
concepts appear to be potentially viable in the time frame selected. Public and institutional
acceptance of nuclear power was found to be affected primarily by four issues:
(1) operational safety, (2) waste handling and disposal, (3) construction and operating
costs, and (4) the adequacy of management and regulatory controls.
vii
1. INTRODUCTION
The Nuclear Power Options Viability Study (NPOVS) was initiated at the beginning
of calendar year 1984 by Oak Ridge National Laboratory (ORNL). The objective of
NPOVS was to explore the viabilities of several nuclear electric power generation options
for this country in the 2000-2010 time frame. The identification and development of
methods and criteria for evaluating new reactor concepts were important efforts. Innovative
concepts were identified that may be marketable at the time when studies show that the
demand for new electrical energy capacity is expected to have increased significantly.
These concepts were considered and evaluated with respect to the criteria and with
emphasis on cost, safety features, operability, constructibility, regulation, research needs,
and market acceptance. Nuclear reactors are recognized as a valuable resource to meet
future energy demands.
ORNL, recognizing the need for a broad base of knowledge and experience,
engaged the Tennessee Valley Authority (TVA) and The University of Tennessee to
participate as partners in the study. TVA concentrated its efforts on evaluation of the
concepts and licensing. The University of Tennessee assisted in the evaluation of
construction costs and public opinion issues. Both institutions contributed extensively to
the evaluation of issues and in review of the reports. In conducting the study, the authors
extensively contacted segments of the nuclear industry for current information concerning
the concepts studied and for other valued assistance.
Many of the problems encountered by the nuclear industry are institutional in nature
and relate to the way in which the utility companies, designers, constructors, and regulators
are organized and function. This study attempted to identify these institutional factors but
has not addressed them in all aspects. It was observed in the study that the institutional
problems derive in some measure from technical features, which, in turn, originate at least
in part from the large size, complexity, and exacting requirements for existing nuclear
plants. Emphasis in the study was placed on the technical aspects that have potential merit
and on improved design concepts that can help to alleviate institutional problems. Other
institutional factors are addressed, first, where they are judged to have a substantial impact
on technical features of design and construction and, second, with respect to market
acceptance. Consideration of additional institutional aspects is thought to be desirable,
perhaps necessary, but is beyond the scope of this study.
The study emphasized criteria by which nuclear power reactors can be judged and
which are considered appropriate for judging future commercial viability. Other design or
operational needs that are important but are more difficult to quantify were also considered.
These are presented as either essential or desirable characteristics. Several innovative
reactor concepts are described and evaluated with respect to these measures.
This study differs in several respects from other studies concerning the future of
nuclear power in the United States. The first is the time frame of interest. The NPOVS
effort was focused on a little later period (2000-2010) than most studies. For the near
term, existing Light Water Reactor (LWR) designs, or their evolutionary modifications, are
available nuclear choices if there is a sufficient demand for increased electrical generating
capacity. Projections by the electric industry indicate that new base load capacity will be
needed before the year 2000. Therefore, it is highly probable that decisions to order
2
baseload capacity will be made by 2000-2010 (Ref. 1) and, furthermore, that the reactor
concepts discussed in this report have the potential for competing with existing LWR
designs or coal-fired plants at that time. For the more distant future, nuclear plant concepts
incorporating more innovative, if not revolutionary, features could be the best choices.
The second aspect making this study different is the level of technical detail
considered in evaluating the specific designs. A significant amount of design information
was generated in the last three years by all of the nuclear designers involved with
innovative concepts, and much of this information was made available to the NPOVS.
Recognition has been given to the special features of each concept and thus to the role that
each may achieve in a mature nuclear economy.
The NPOVS program proceeded in steps: (1) a literature search and development
of a bibliography; (2) development of criteria for evaluation of nuclear plant designs and
plans; (3) evaluation of selected design concepts using these criteria as a guide; and (4)
recommendations for areas of research and development (R&D) needed to reduce
uncertainties in the viabilities of options. The approach used in evaluation was to compile
detailed information on the various reactor concepts of interest, synthesize that information
in accordance with specific technical areas, develop an understanding of how design
features influence the overall cost of generating power, and consider how changes in the
design might accomplish improved economic performance and acceptance by regulators
and the public. In addition to technical evaluations, assessments were made of the various
nontechnical factors that influence commercial use, for example, regulatory requirements,
industry perspectives on future technologies, market acceptance, electric power growth
needs, and economic conditions.
The report of the NPOVS is organized into four volumes, as follows:
* Volume I, Executive Summary
» Volume II, Reactor Concepts, Descriptions, and Assessments?
» Volume III, Nuclear Discipline Topics?
* Volume 1V, Bibliography
2. CRITERIA FOR EVALUATION OF CONCEPTS
An carly effort of the study was to develop criteria that reactor designs would have
to meet to become viable in the future. In the reactor assessments, these criteria were used
as a guide to assess nuclear concepts. In most cases, lack of data necessitated the use of
engineering judgment to determine the status of, or potential for, conformance with the
criteria. Often such judgments must be supplemented by the formulation of further R&D
needed to facilitate more reliable conclusions. These needs are identified for each of the
concepts.
The evaluative criteria established in this study are as follows:
1. The calculated risk to the public due to accidents is less than or equal to the
calculated risk associated with the best modern LWRs.
2. The probability of events leading to loss of investment is less than or equal to 10-4
per yvear (based on plant costs).
3
The economic performance of the nuclear plant is at least equivalent to that for coal-
fired plants. (Financial goals for the utility are met, and busbar costs are acceptable
to the public utility commissions.)
The design of each plant is complete enough for analysis to show that the
probability of significant cost/schedule overruns is acceptably low,
Official approval of a plant design must be given by the U.S. Nuclear Regulatory
Commission (NRC) to assure the investor and the public of a high probability that
the plant will be licensed on a timely basis if constructed in accordance with the
approved design.
For a new concept to become attractive in the marketplace, demonstration of its
readiness to be designed, built, and licensed and to begin operations on time and at
projected cost 1s necessary.
The design should include only those nuclear technologies for which the
prospective owner/operator has demonstrated competence or can acquire competent
managers and operators.
These criteria obviously are not independent since items 1 and 2 deal with the
probabilities for successful operation or failure, items 3 to 6 are primarily economic, and
item 7 relates to demonstrated operational experience. However, we deem each criterion to
have sufficient stand-alone merits to justify separate consideration.
The criteria are augmented by a list of characteristics that provide further guidance
for properties judged to be of importance to nuclear power viability. The characteristics
chosen are not as quantifiable or demonstrable as are the criteria and have been chosen to
include features that complement and amplify the criteria. The essential characteristics are
as follows:
* Acceptable front-end costs and risks
Construction economics
¢ Low and controllable capital costs (utilizing, for example, shop fabrication, a
minimum of nuclear grade components, and standardization)
» Designed for long lifetime
Investment economics, including risk
Low costs associated with accidents
Low costs associated with construction delays
Low costs associated with delayed or unanticipated actions by regulatory bodies
Low costs associated with delayed or unanticipated actions for environmental
protection
Unit sizes to match load growth
e Uncertainties in technology and experience not likely to negate investment
economics
e & & &
4
Minimum cost for reliable and safe operation
High availability
Minimum requirements for operating and security staffs
Designed for ease of access to facilitate maintenance
Simple and effective modern control system
Low fuel cycle costs
Adequate seismic design
Practical ability to construct
Availability of financing
Availability of qualified vendors
Availability of needed technology
Adequately developed licensing regulations applicable to the concept
Ease of construction enhanced by design
Public acceptance
Operational safety of power plants
Safe transportation and disposal of nuclear waste
Low radioactive effluent
Low effect on rates of construction and operation
Adequate management controls on construction and operation
Utility and regulatory credibility.
Related desirable characteristics are as follows:
S N N
PR OOONANE W
practical research, development, and demonstration requirements,
ease of siting,
load-following capability,
resistance to sabotage,
ease of waste handling and disposal,
good fuel utilization,
ease of fuel recycle,
technology applicable to breeder reactors,
high thermal efficiency,
low radiation exposure to workers,
high versatility relative to applications,
resistance to nuclear fuel diversion and proliferation,
on-line refueling,
low visual profile.
Several of these characteristics are not readily determined quantitatively and
therefore are applied primarily by judgment. They indicate areas and issues of interest and
importance. As a rule, an individual characteristic should not determine the fate or viability
of a concept.
3. CONCEPT SELECTION AND CLASSIFICATION
In selecting the concepts to be studied, three ground rules were used:
1. The nuclear plant design option should be developed sufficiently that an order could
be placed in the 2000-2010 time period.
2. The design option should be economically competitive with environmentally
acceptable coal-fired plants.
3. The design option should possess a high degree of passive safety to protect the public
health and property and the owner's investment. ["Passive safety" refers to the
reliance on natural physical laws and properties of materials to effect shutdown and
radioactive decay heat removal without relying heavily on mechanically or electrically
activated and driven devices as employed in active (engineered) systems.]
The concepts selected and described in Volume II of this report? are considered
advanced and have various degrees of innovation as compared to current concepts. For
convenience, the selected concepts were classified in the traditional way by their coolants
and respective generic names. The concepts selected are:
1. Light-Water Reactors (LWRs)
e PIUS (Process Inherent Ultimate Safety) - promoted by ASEA-ATOM of Sweden®
» Small BWR (Boiling Water Reactor) - promoted by General Electric (GE)®
2. Liquid Metal Reactors (LMRs)
e PRISM (Power Reactor Intrinsically Safe Module) - The GE advanced concept
supported by DOE?
» SAFR (Sodium Advanced Fast Reactor) - The Rockwell International (RI)
advanced concept supported by DOE?
e LSPB (Large-Scale Prototype Breeder) - The Electric Power Research Institute-
Consolidated Management Office (EPRI-CoMO) concept supported by EPRI and
DOE?
3. High-Temperature Reactor (HTR)
» Side-by-Side Modular - The core and steam generator in separate steel vessels in a
side-by-side configuration. The concept is supported by DOE and promoted by
Gas-Cooled Reactor Associates (GCRA) and industrial firms.?
These concepts are judged to be potentially available in the chosen time period, are
estimated by their promoters to be economically competitive with coal-fired power plants,
and have varying degrees of passive safety attributes. Although the designs are too
preliminary for a complete and definitive assessment, each is believed to have potential for
a significant future role. The Advanced Pressurized-Water Reactor (APWR), the Advanced
Boiling-Water Reactor (ABWR), and the large HTR are recognized as viable systems that
could meet electric power generating needs prior to or following the year 2000. These
6
reactors were not included in this study except for reference because they do not fully meet
the third ground rule and because they have already been the subject of extensive study and
development by industry.
4. SUMMARY OF FINDINGS FOR CONCEPTS
Most advanced reactor concepts are smaller than present LWRs; therefore, they
suffer the economic disadvantage, whether real or perceived, associated with economy of
scale. This disadvantage is claimed to be offset or compensated for in varying degrees
through an improved match with load growth, reduction in capital risk, increased shop
fabrication, shorter construction time, increased standardization, design simplification, and
less demanding construction management requirements. Licensing may also be simplified
if credit can be taken for passive safety features such that other traditional safety system:s,
required by the defense-in-depth philosophy, can be eliminated. A substantial problem in
achieving these compensations derives from the need for a large front-end investment for
certain of these features. Automated shop fabrication, in particular, will require a
substantial backlog of orders to be economically feasible. Nuclear plant standardization is
widely viewed as an important goal for viability.
To be concise in this summary, we have assumed that the reader is familiar with the
concepts. The claims, advantages, disadvantages, and important development needs will
be summarized in the order in which the concepts are described in Volume II of this
report.? It must be noted that each of these concepts is currently in design development.
The descriptions and assessments of this study reflect the status for each as of
September 1985 except that some updating has been done where information was readily
available. The reader should recognize that further development is expected to change
design features and thus affect the conclusions from future evaluations.
All the concepts chosen for the study appear to be potentially viable, but the
available information has been insufficient to fully assess their economic competitiveness.
Specific findings for each concept follow.
4.1 PIUS
The basic design premise of this concept is to achieve a very high degree of passive
safety with respect to equipment failure, operator error, and external threats. The large
pool of borated water, which can enter the core without mechanical, electrical, or operator
action, is to provide both shutdown and seven days of passive cooling for decay heat
removal. These claims appear to be justified, although questions remain concerning the
safety of fuel and equipment handling operations within the pool. The availability of water
for introduction to the pool after seven days is site dependent but potentially viable.
Overall, the concept appears to be licensable without major redesign, assuming that the
NRC will accept a reactor with no control rods. The features that promote safety also
appear applicable to protection of the investment. ASEA-ATOM claims that the plant can
be economically competitive with coal-fired plants. This may depend on further evaluation
of the identified problems that follow.
The steam generator located inside the Prestressed Concrete Pressure Vessel
(PCPV) is of a difficult design with respect to maintenance. This and the problems of
handling fuel and equipment deep (30 m) in the pool require careful design and detailed
7
assessment and are considered a disadvantage with respect to the potential availability of the
plant. Management of refueling appears difficult for the three-core design if the sequence
becomes out of phase.
Development and testing needs include further demonstration of fluid interface
stability, extensive study and testing of steam generator modules, thorough testing of
underwater fuel and equipment handling systems, steam flow and pressurizer stability for
the multimodular design, thermal insulation development and testing, and demonstration of
the PCPV design, particularly for the top closure. A demonstration reactor may be required
to adequately test the novel features of the concept; however, this plant may be determined
commercially viable following a successful test period.
4.2 SMALL ADVANCED BWR
This reactor obviously derives advantage from its many operating similarities to
existing BWRs. The gravity-fed Emergency Core Cooling System (ECCS) appears well
conceived and adequate to provide shutdown cooling for up to three days, although its
reliability is dependent on a relatively untried fail-open valve. A reliable site-dependent
supply of additional cooling water would be required beyond the three days. Operator
training should be straightforward since the basic operation is similar to that of existing
BWR plants, A first-of-a-kind demonstration whereby the plant would later be used for
power production may be practical and adequate for this concept. In this case, the first
plant essentially would be a commercial unit that is subjected to an extensive test program
prior to acceptance by the utility.
Cost competitiveness is difficult to assess at this early stage of design development.
Licensing requirements, although not thought to be particularly difficult, have not been
adequately addressed. Model testing for the gravity-drain ECCS, steam injector testing,
and thermal hydraulic and seismic analyses must be thorough. The depressurization valve
also requires design, development, and testing.
4.3 LMR CONCEPTS
The LSPB is an evolution of previous Liquid Metal Fast Breeder Reactor (LMFBR)
designs. Itincludes several innovations to reduce capital costs and to enhance safety. The
latter include diverse and independent reactor shutdown and dedicated decay heat removal
systems. Although this design offers lower costs than previous breeder concepts studied,
these features are yet to be evaluated fully with respect to construction methods and
licensability. The LSPB appears attractive in offering economy of scale and increased
passive safety.
Since PRISM and SAFR are both under development in a DOE program and are at
a preliminary stage, they were assessed primarily in common. LMRs benefit from the
inherent features of low system pressure and high thermal conductivity of the coolant,
which are common to all concepts. These features permit the design of primary
containment pool concepts with reliable passive natural convection decay heat removal to
atmospheric air. These smaller modular concepts provide potential for testing of the core
stability for conditions that might result from reactivity increases or from loss of flow of
primary sodium. In this respect, smaller reactors, in general, have an advantage over the
larger LMRs. Although the hypothetical core disruptive accident (HCDA) is claimed to be
incredible by the proponents, the case for disregarding this accident is yet to be approved
by the NRC. If the Clinch River Breeder Reactor (CRBR) can be taken as a precedent,
8
then it would be reasonable to expect that a HCDA would be a beyond design basis event
(BDBE). Acknowledging passive accommodation of HCDAs could significantly reduce
design complexity, facilitate licensing, and improve public acceptance. Reliable control rod
shutdown systems, feedback response from temperature increases, and the resulting
thermal expansion are important safety features. Although containments or confinements
are provided, careful design and perhaps testing will be required to ensure that air oxidation
of the sodium is unlikely. Such containments must be protected from external threats.
An advantage of the LMR is the extensive operating experience available from the
Fast Flux Test Facility (FFTF), the Experimental Breeder Reactor-1II (EBR-II), and from
European and Japanese plants. However, much of this experience base is not at the utility
level, and the loss of the Clinch River Breeder Reactor (CRBR) slowed the pace of
development of LMRs in the United States. Even though it appears possible to design,
construct, and operate a demonstration plant and to reach commercialization within the
2000-2010 time frame, it would require an early dedication to the task.
The availability of related experience, the simplicity of the proposed designs, and
the passive features mentioned above strongly suggest that the licensing of these LMRs
should be achievable. Standardization of reactor designs should enable a generic license to
be issued by NRC thus limiting licensing consideration, after the initial plant, to site-
specific issues. An obvious long-term advantage of the LMR is its potential for breeding
and thereby creating an essentially unlimited extension of uranium fuel resources. This is
not an immediate objective of the current program, but it should not be overlooked.
Historically, LMR concepts have had higher capital costs than LWRs. This cost
experience is manifested in European as well as U.S. designs. Although the current
concepts address this issue, it is not yet adequately resolved. The high burnup core
designs represent one approach to overall cost reduction. Another disadvantage is the
requirement for enriched uranium or plutonium as the starting fuel. The former is available
from U.S. enrichment systems. The latter is at an early stage of both institutional and
technical development for acceptable fuel reprocessing plants in this country, although
considerable experience exists abroad and in military facilities. Other countries offer the
prospect for purchase of plutonium fuel, but this is unlikely to be an acceptable continuing
source. Once-through cycles are not adequate for long-term nuclear energy viability;
therefore, reprocessing remains an important objective for future LMR concepts. Integral
Fast Reactors, which would be collocated with the supporting fuel reprocessing and
refabrication facility, face significant institutional problems for the combined operation.
LMR development needs include advanced core design and proven neutron
counting systems, improved shielding, and self-actuated shutdown systems. Testing of
heat removal systems is an obvious requirement. Depending upon the choice of initial fuel,
the fuel cycle development requirements may be extensive. The metal fuel cycle, which is
claimed to offer safety and operational advantages, requires an extensive fuel development
and testing program. Concepts under consideration could benefit from proposed safety
demonstration tests for licensing purposes; the experience would be valuable and analytical
methods could be tested. However, we caution against overly optimistic expectations from
this approach because many disturbances (such as the effects of severe seismic events,
interference with air cooling, and sabotage) cannot be fully tested and would require
extensive analysis for evaluation. A more desirable and convincing approach with respect
to utility acceptance may be to construct and operate a demonstration or prototype plant
based on an adequate program of analysis, component development and testing, and
design. This plant probably could achieve commercial operation, but some iteration would
no doubt be beneficial before selecting a specific design for standardization.
9
4.4 MODULAR HIGH-TEMPERATURE GAS-COOLED REACTOR (MHTR)
SIDE-BY-SIDE CONCEPT
A high degree of public protection is achieved through a capability for extended
afterheat removal through the vessel wall by convection, conduction, and thermal radiation
without operator, mechanical, or electrical intervention. This advantage is made possible
by the very high temperature capability of the fuel, including retention of fission products
and the slow thermal response of the core, which eliminates the need for a fast-acting
shutdown system. The same protection applies to the probability of events leading to a loss
of investment and offers the possibility for advantageous siting of plants. The "low-
enriched" fuel is beneficial for proliferation resistance but requires enrichment substantially
higher than that of a conventional LWR (20% vs ~4%). The potential for producing high-
temperature process heat is a long-term advantage.
A disincentive for the application of an MHTR in the United States is the poor
performance to date of the Fort St. Vrain reactor (FSVR). However, the difficulties with
this reactor are unique to its equipment and are not common with the new concept. (In
many ways, the MHTR design can benefit from the lessons learned at the FSVR.) Also,
the performance of the Peach Bottom Unit 1 reactor in the United States and of the AVR in
Germany has been satisfactory. Since the THTR-300 reactor in Germany is the latest HTR
to operate, its performance is important to watch.
The small base of operating experience in the United States suggests an important
need for a successful MHTR demonstration plant. Because of the ruggedness and
resiliency of the fuel and the inherently slow time response for temperature excursions, it
seems possible that a demonstration plant could be used extensively for experimentation in
safety and operability and could later serve as a first-of-a-kind power plant. However,
since the design experience is also limited, it is quite possible that a standardized plant
design might benefit from the experience of the demonstration.
Development needs include improved determination of fission product retention by
the fuel coatings, graphite, and metal surfaces under hypothetical extreme accident
conditions. Graphite development should include additional irradiation creep data, a
statistically determined physical property data base, and evaluated failure criteria. Fuel
fabrication development is far advanced in Germany and the FSVR fuel has been
successful; however, the reference fuel for the MHTR has higher performance
specifications than FSVR fuel. Process development and fuel testing are needed for
production methods to meet the higher specifications. Structural materials development
needs relate to obtaining physical property data to satisfy code requirements, including the
effects of neutron irradiation on physical properties. Another important area of
development is the testing of key components under actual conditions. This is especially
important in the case of the circulator to assure high availability. Materials and corrosion
testing for various projected impurity levels in the helium would also be desirable but
probably is not a requirement.
5. SUMMARY OF TOPICAL FINDINGS
Several subjects that were judged to be important in the evaluation of concepts
have been considered in detail, both for the evaluations and generically. These topics
(Construction, Economics, Regulation, Safety and Economic Risk, Nuclear Waste
Transportation and Disposal, and Market Acceptance of New Reactor Technologies) are
discussed in order in the following sections.
10
5.1 CONSTRUCTION
The various constructibility claims, both expressed or implied, of the six NPOVS-
selected reactor concepts were first reviewed and tabulated in a logical order (Table 2.1 in
Volume III).3 Factors that were considered include availability of information to support
claims; design complexity; standardization, modularization, and shop fabrication;
construction schedule; construction management; and new management techniques and
construction tools. Research and development needs in support of construction of these
concepts have also been explored.
A positive factor contributing to the potential success of the concepts studied is that
the designers included constructibility considerations from the outset. The construction
goals and criteria of most concepts include (a) simplicity of structural design; (b) optimal
standardization, modularization, and shop fabrication; (c) use of heavy-duty transport
means to ship shop-fabricated components to the site and heavy-duty cranes and/or air
casters to erect heavy modules at the site; (d) use of a limited-size, dedicated crew to
increase field productivity; (e) limitation of safety-grade construction to the nuclear island
with separation from the balance-of-plant (BOP) construction; (f) short construction
schedules; and (g) effective project management.
Several design features would facilitate achieving these goals. Most concepts have
built-in passive safety systems to cool the reactor core for several hours before additional
remedial measures must be taken. These passive safety features enable many concepts to
function with a smaller number of systems and structures than the number necessary for
current LWRs. Reducing the number of safety systems and confining them to the nuclear
island would permit savings in construction material, construction requirements,
construction schedule, and quality assurance documentation requirements.
On the other hand, additional data are needed to substantiate the claim that the
concepts studied could be constructed more easily, faster, and cheaper than current LWRs
because of the higher projected degree of standardization, modularization, and shop
fabrication. These meritorious cost-cutting, productivity- and quality-increasing techniques
are more dependent on the assurance of a large order than on specific reactor concepts.
Such a large order for reactors without customized demands would allow any concept,
including LWRs, to be standardized, modularized, extensively shop fabricated, and built in
a period of less than five years. The number of units to be manufactured for a given
addition of power is inversely proportional to the size of the units; hence, it is more likely
that the initial cost for factory automation can be justified for many small units than for a
few large reactors. However, there may be some drawbacks in the constructibility of the
concepts studied vis-a-vis large reactors: the commodity requirements per kilowatt
(electrical) of most of the concepts are higher; the steel vessels of the MHTR, SAFR, and
PRISM units are as large as those of LWRs, which have up to 10 times the power rating;
and the concepts may have to undergo several improvements before standardization and
modularization will bring any real benefits.
From the management viewpoint, the sequential construction of smaller units can
make the job more manageable and productive, but this approach is not the exclusive
characteristic of the concepts studied. The passive safety features of the concepts and the
proposed separation of the nuclear island and BOP construction should definitely help to
reduce construction costs. However, care must be taken to insure that the total plant
operates smoothly as a unit even if the BOP is not required to serve a safety function.
11
We recommend that more attention be paid to substantiation of the constructibility
claims, particularly in comparison with current LWR technology in the United States and
overseas. Recent studies concerning the capability of the Combustion Engineering heavy
component facility in Chattanooga, Tennessee, to manufacture vessels for the MHTR and
other concepts provide a step in this direction.
5.2 ECONOMICS
The goal of the economics effort was to gain an insight into the many factors that
are important to the economic competitiveness of the various NPOVS concepts. It was not
intended to rank one concept relative to the others but to form a basis for future efforts
when more is known about the design and costs of each concept. The economic evaluation
included analyses of capital investment costs, busbar power generation costs, and
commodities necessary to build the plants. The objective of the analyses was to provide a
perspective on the relative economics of the various concepts using traditional methods and
not to offer a judgment on their absolute competitiveness. The analyses indicated that
estimated capital investment costs for the modular plants generally fall below or at the the
best of current-experience LWRs when the LWRs are scaled to the size range of the
modular plants. The results of the analyses also showed that the power generation costs of
all the concepts fall in the same competitive range. There are, however, large uncertainties
in the cost information for all of the concepts.
The power generation cost comparisons are traditional busbar cost calculations and
may not take into consideration factors that are important to the economics of small plants.
Generic issues germane to the economic attractiveness of small modular plants relative to
large plants include plant availability and reliability, shop fabrication, safety separation of
the nuclear island and the BOP, modular construction and cost-size scaling, plant
standardization, and fuel cycle.
Although there is room for improvement in availability for plants of all sizes,
historically, small-size power plants appear to have had better experience than large-size
plants.10 Also, there is a smaller probability of losing generation from multiple small plants
compared to one large plant of the same capacity, and, therefore, less total capacity is
needed with multiple small plants than with one big plant.
Factory fabrication of plant modules is applicable for all sizes of plants, but the
economic benefits may be realized only if there is a large order for such plants. However,
factory fabrication is especially applicable to smaller plants since a larger percentage of the
plant may be factory built in individual modules. A greater automation potential exists for
construction of smaller units since a greater number of smaller units would be needed than
large units for a given total capacity. However, the additional costs connected with factory
fabrication, including costs for acquiring the factory facility and tooling up, transportation
of modules, and carrying charges must be accommodated.
The physical separation of the BOP from the nuclear island offers potential for
economic savings. A conservative analysis indicates that, if coal-fired plant placement rates
are applied to the nonnuclear BOP, the overnight costs of nuclear plants can be reduced by
nearly 10%, based on construction labor cost reductions alone. Additional savings in
indirect costs will result from reduced labor content and shorter construction time, but
additional costs may also be caused by dispersion of facilities and redundant construction
management and facilities.
12
Small plants may have additional economic advantages relative to large plants when
the utility system is included in the analysis. Some of these advantages include a better
match to electric growth, thereby lessening overcapacity; shorter lead times for small plants
than for large ones; better system reliability for a given capacity; and better accommodation
of demand changes. There is also less financial risk, which leads to a potential decrease in
the overall cost of money. Estimates indicate that utilities could afford to pay an additional
25% or more for a short-lead-time, modular plant than for a long-lead-time, large-size plant
with no increase in average rates to the consumer.11:12
Plant standardization offers large potential economic advantages. A principal
advantage is that the design and engineering costs are spread over a large number of units.
Also, learning takes place as additional units are designed, thus reducing design cost, labor
requirements, and lead time. The benefits of standardization apply to large-size plants as
well as to small ones, albeit probably to a lesser degree, since fewer units would be built.
The fuel cycles for the PIUS and small BWR are the same as for current LWRs and
will use similar fuel. The LMR and HTR fuel cycles will involve development and perhaps
considerable capital investment to implement. However, HTR requirements are primarily
for fuel testing and fabrication facilities since a once-through cycle is planned. Economic
issues involve the cost for reprocessing and fuel fabrication, the economics of integral
recycle facilities, use of enriched uranium for LMRs, plutonium value and tax treatment,
and waste disposal issues. Preliminary studies (Appendix E, Volume II)? indicate that
there is a cost disadvantage in small, integrated fuel recycle facilities relative to large,
common, central fuel recycle facilities.
Further information, studies, and analyses are needed to properly evaluate the
economic competitiveness of the concepts relative to current LWR technology and to coal-
fired power plants. Of primary importance is the development of basic cost information for
the concepts, applying consistent ground rules for all concepts. Also, each of the generic
issues needs to be explored quantitatively in depth to determine if small plants in fact have
an economic advantage relative to large plants.
5.3 REGULATION
A utility's confidence in its ability to obtain a license to operate a nuclear power
plant is paramount in any decision to undertake a nuclear project. Experience has shown
that the licensing process can be cumbersome and unpredictable. A number of steps have
been proposed which, taken either independently or in combination, would improve the
regulatory climate both for existing reactor types and for new designs. A better integration
of the design process, with a complete design available when a license is applied for,
would facilitate the regulatory review and would reduce the number of changes called for
during construction. The same design could be used for a series of plants, preapproved by
the NRC as a standard design. When combined with a preapproved siting policy,
preapproved standard designs would substantially reduce the front-end risk and would
accelerate project schedules. There are also strong economic incentives to adopt standard
plant designs. Several standardized plant programs were initiated in the 1970s but were
terminated by plant cancellations.
The extensiveness of regulatory, as well as nonregulatory, backfits to operating
plants and those under construction have been cited by utilities as major reasons for the
decline of the nuclear option in the United States. Stability and consistency in the NRC
regulatory process must somehow be achieved to make new nuclear plants viable.
13
The adoption of performance-based regulation, as contrasted with the present
prescriptive mode, has been proposed as a means of stabilizing the regulatory process. The
adoption of passive safety systems, such as are used in the concepts studied by NPOVS,
may increase the applicability of performance standards.
The NRC has proposed an advanced reactors policy calling for simpler, more
reliable reactor designs.!> We believe that the concepts studied by NPOVS are consistent
with that policy.
A number of licensing issues appear to be associated with the advanced concepts:
« The NPOVS reactor concept proponents, relying as they do on passive safety features
to prevent adverse effects of accidents, in most cases claim that nuclear safety-grade
equipment can be limited to the nuclear island.
* Proponents of some of the concepts believe that minimal or no containment can be
justified because of a lack of credible severe accident sequences.
« Some proponents believe that a safety demonstration plant would greatly facilitate
licensing.
» There is considerable support for the concept that very rare accident precursors, with
frequency below some particular value such as 107 per reactor year, need not be
considered as design basis events. However, current experience and probabilistic risk
assessment (PRA) methods may not be adequate to establish such values.
Potentially large costs are associated with the resolution of these issues; therefore, early
NRC consideration of these matters would be desirable.
5.4 SAFETY AND ECONOMIC RISK
The NPOVS criteria address safety and economic risk by providing limits for the
probability of events related to safety and risk. The criteria require PRA to ascertain
compliance. Since PRAs are not available for all of the advanced concepts, judgment has
to be substituted. The broad use of passive safety features may eliminate the adverse
consequences of many accident sequences, but the PRA would still be useful to identify
deficiencies and to assure safe designs.
As the result of passive safety features, much more time would be available to
reactor operators for the use of engineered systems or other emergency response (i.e., days
for most anticipated accident initiators). The designers of passively safe concepts have
responded to this characteristic in the following ways:
* Accident prevention as opposed to mitigation has been emphasized.
* Few or no operator actions are required.
» Simplified engineered safety systems, with few critical components, are used.
* In some cases, it is proposed to demonstrate safety by subjecting a prototype to
specified accident initiators.
14
Circumstances other than accident risk may put the capital investment at risk and
might be considered vital by investors. These include political actions (such as the Austrian
Zwentendorf Reactor), quality assurance deficiencies (such as at Zimmer), or financial
problems (such as at Marble Hill). Operation risk, related to unexpected events that affect
revenue, can have very high costs. New and untested concepts are particularly vulnerable
to operation risk. Preapproved standard plant designs with a good operational data base
would tend to minimize the above risks.
Proponents of the advanced concepts have not in general calculated source terms for
their systems. NRC regulations require that there be a containment system to mitigate the
release of an arbitrary fraction of the reactor's fission products, independent of reactor
design. This fraction is probably much greater than the actual release that would be
experienced in most accidents. It is desirable that containments be designed to mitigate
realistic source terms determined for the specific design.
Further investigation and research are required to reduce the uncertainties associated
with safety and economic risk. These include attention to issues such as:
» Development of quantitative risk criteria for advanced reactors.
e Consideration of the significance of passive safety features to risk reduction.
Determination of the frequency of rare events that would constitute a lower limit for
design basis.
» Appropriate treatment of source term and containment for very safe designs.
» Appropriate focus on safety and risk reduction in the development and application of
standard designs.
5.5 NUCLEAR WASTE TRANSPORTATION AND DISPOSAL
Legislation has been enacted that (if implemented as scheduled) would provide the
technology and facilities for waste disposal prior to the year 2000. Utilities choosing to
build one of the concepts studied by NPOVS should have firm guidelines on waste
management and disposal by that time frame. The only reactor types considered here that
may require special waste system development are the modular HTR and the metal-fueled
LLMR. For the former it may be desirable to reduce the high-level waste volume, and for
the latter a new waste technology is required.
The public risks due to potential accidents in the transportation and disposal of
nuclear wastes are exceedingly small according to conventional risk analysis.
Nevertheless, many members of the public consider the wastes a major hazard. Some of
these concerns are likely to persist into the time when concepts studied by NPOVS would
be deployed.
5.6 PILOT STUDY OF MARKET ACCEPTANCE OF NEW NUCLEAR
TECHNOLOGIES
This part of the NPOVS represents exploratory research designed to provide a basis
for assessing the market acceptability of new reactor concepts. The first part of the
research addressed whether issues are characterized as technical or institutional by
15
proponents and critics of nuclear power. Thus the market acceptance research dealt directly
with the conflicts that arise from the persistent debates over the technology. The other part
of the research sought to understand the conflict that emerges over nuclear power in the
process of choosing the capacity needed. This research was carried out through a series of
case studies of public utilities, public utility commissions (PUCs), and interest groups
critical of nuclear power. This second study was focused on the utilities' preferences and
the constraints imposed on these preferences by regulators and public interest groups. The
two parts of the research were drawn together to define a set of major issues that are likely
to be at the core of the acceptability question for new reactor technologies.
5.6.1 General Conditions for a Future Nuclear Market
The findings of this pilot study must be treated as provisional, especially as they are
not entirely consistent with some of the prevailing views of the nuclear power industry.
Analysis of the interviews conducted for the study indicate that a commercial market for
some sort of nuclear generation technology is feasible after the turn of the century, subject
to three necessary, but not sufficient, conditions. These are:
e aprojected need for new baseload capacity
e anarrowing of the gap in construction costs between environmentally acceptable fossil
and nuclear plants; and
« the absence of a third option for baseload power to compete with nuclear.
Even if all three necessary conditions are satisfied, there is no guarantee that nuclear
options will be chosen. There is a further set of facilitating conditions that would
substantially improve the position of nuclear technologies within the market. Thesc include
improvements in the following areas:
» stability of the regulatory environment
» improved accuracy and reliability of load forecasting techniques
improved cost controls in nuclear construction and operation, including standardized or
turnkey plants; and
e demonstrated technical feasibility of new nuclear reactors.
The first of these facilitating conditions has been highlighted by many utilities, only
one of which appeared in the study, as the primary condition for their ordering new nuclear
capacity. However, data from the utility respondents and economic behavior in other fields
suggest that if the economic incentives are strong enough, regulatory difficulties will be
overcome. This factor in market acceptability of new nuclear technologies, therefore,
requires further investigation.
Interviews with decision makers of five utilities revealed the skepticism of the
industry that these conditions will be met within the 2000-2010 time frame. Consequently,
utilities indicated no active interest at present in constructing new nuclear units. However,
nuclear options are retained in modeling possible alternatives for future baseload system
planning.
16 .