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In this section we look at the technological issues that must be addressed to ensure that nuclear power continues as an economical energy option for the foreseeable future.
Considerable effort is now being applied to improve the commercialized thermal neutron reactors and to develop FBRs. A compendium of the characteristics of the technology of these advanced reactors and their fuel cycles and of the status of development appears in the APPENDIX TABLE.
Conventional thermal neutron reactors will supply more than 90% of nuclear power in the first half of the twenty-first century even if the FBR is introduced worldwide in 2030. Therefore, making evolutionary changes to upgrade conventional nuclear reactor design could produce significant gains. The scene will change in the second half of the twenty-first century if fossil fuels (except coal) and uranium for thermal reactors become scarce and if the projected greenhouse effect is confirmed, requiring a drastic reduction in fossil fuel use. The FBR is likely to be needed to supply a major part of world energy needs. Thus, development of the FBR should proceed expeditiously so that it will be available when needed.
There are concrete targets for the development of advanced thermal neutron reactors, both light and heavy water types. The targets are evolutionary and designed to introduce improvements in the near future. The goals include cost reduction, efficient site use, greater reliability, simplification of maintenance, passive safety features, and design for nonproliferation. Research must be continued on advanced reactors not only to enhance performance but also to adapt them to rising standards in areas such as environmental impact, safety, and nonproliferation.
The commercialization of the FBR is the first priority task of long-term development. Metallic, nitride, and carbide fuels of mixed plutonium and uranium are being developed for FBRs as well as the more familiar mixed-oxide (MOX) fuel. It is important to keep the development of reactors in step with the development of the fuel cycles, including both the front end and the back end of the fuel cycles. The development of oxide fuel is further advanced than that of other fuel types and cycles, and the performance of oxide fuel has already been demonstrated. Therefore, the most realistic and reliable way to pursue early commercialization is with MOX fuel and the current method of Purex reprocessing.
The importance of recycling plutonium has been recognized since the beginning of nuclear power development. Development of the FBR and the associated fuel cycle began in the United States in the 1940s, in the United Kingdom and Soviet Union in the 1950s, and in France and Japan in the 1960s. A total of 21 fast reactors have been constructed so far; the 9 listed in Table 5 are working at present.
| Reactor | Power(MWe) | Criticality | Country |
|---|---|---|---|
| Superphenix | 1240 | 1985 | France |
| BN-600 | 600 | 1979 | Russia |
| MONJU | 280 | 1994 | Japan |
| Phenix | 250 | 1973 | France |
| BN-350 | 150* | 1972 | Kazakhstan |
| JOYO | 100** | 1977 | Japan |
| FBTR | 15 | 1985 | India |
| BOR-60 | 12 | 1969 | Russia |
| BR-10 | 10** | 1972 | Russia |
Experience with construction and operation of large FBRs has been obtained since 1980 with the 600-MWe BN-600 in Russia and since 1986 with the 1200-MWe Superphenix in France. Many technical problems have been solved through research and development and reactor operations.
All of the small fast reactors that have operated for a number of years proved to be safe, reliable, and easy to operate. The large ones have been more difficult. Only the large fast reactors built in the former Soviet Union have been able to achieve consistently high load factors, and these are low-rated and low-burnup plants. The large reactors in the United Kingdom and France have not achieved acceptable load factors. Such a pattern of performance is not uncommon in developing new power systems, and experience with the thermal reactors has shown that it takes a few decades to identify and correct all the operating problems with a particular design concept. The course of development will be no easier for the fast reactor.
The safety and reliability of FBRs have been explored in the prototype reactor stage. The economics will be determined in the demonstration reactor stage, which is currently being evaluated in the design studies of the European Fast Reactor (EFR) conducted jointly by France, the United Kingdom, and Germany, and of the Demonstration Fast Reactor (DFR) by Japan.
The EFR study projects that the construction cost of series-introduced plants will be 10 to 40% more than that of an LWR, depending on the country in which it is sited (Ref.9). The electricity generation cost (including fuel cycle cost) of the EFR is about 10% higher than that of an LWR in France. Construction cost estimates from the Japanese DFR study are 40% higher than that of the LWR for a first plant, falling to 10% higher for series-introduced plants of 1300 MWe (Ref.10).
If the results of research and development now under way in Europe and Japan, and previously in the United States, are applied to the FBR plant design, the construction cost might be cut to less than that for LWRs. The operating cost (including fuel cycle cost) for FBRs is generally lower than that of LWRs when reliability is acceptable, based on European experience. Thus, the total generation cost of FBRs may be more favorable than that for LWRs.
Construction of the next FBR demonstration plants, being designed in Europe and Japan, is expected to start in the early 2000s; the commercialization of FBRs by series construction could be demonstrated in the 2010s. Therefore, the global introduction of the FBR and its fuel cycle around 2030 could be technically feasible.
Status of Fast Reactor Fuel Cycle Development
Fuel reprocessing technology has been developed by the United Kingdom and France, beginning with the reprocessing of spent fuel from experimental reactors in the 1960s, followed by spent fuel from prototype reactors in the 1980s. The cumulative amounts of FBR fuel reprocessed are about 30 tonnes in France and about 10 tonnes in the United Kingdom. Based on this experience, reprocessing plants of 60 to 80 tons per year capacity are being designed in both countries.
| Plant | Capacity | In Operation | Country |
|---|---|---|---|
| EDRP | 80 tonne/yr | In design | United Kingdom |
| MAR-600 | 60 tonne/yr | In design | France |
| Dounreay | 30 kg/day | 1980 | United Kingdom |
| SAP/APM | 20 kg/day | 1975 | France |
| RETF | 10 kg/day | In construction | Japan |
| CPF | 1 kg/day | 1982 | Japan |
| AT1 | 1 kg/day | 1969 | France |
The fuel for the current fast reactors is mixed plutonium and uranium oxide (MOX). Metallic and nitride fuels are being developed. A nitride fuel core gives better neutron economy than an oxide fuel core because the neutron energy spectrum is harder. Therefore, a nitride fuel FBR can respond more flexibly to requirements such as conversion/breeding ratio, actinide burning, long core life, or compact core. Furthermore, the Purex reprocessing process used for oxide fuel can be applied to nitride fuel. However, it may be necessary to use enriched nitrogen-15 in the nitride fuel in order to avoid, for environmental reasons, the formation of carbon-14 from nitrogen-14 during irradiation. In the future, if technologies such as granulated fuel, vibration packing, and sodium-bonded fuel pins and the dry reprocessing process can be applied commercially to nitride fuel, then the nitride fuel systems are likely to become superior in cost-competitiveness to oxide fuel systems. The nitride fuel systems are currently being investigated in France and Japan.
A metallic fuel core has neutronic characteristics similar to a nitride core. Its total fuel cycle has a number of advantages. At the Argonne National Laboratory in the United States, a pyroprocessing technique has been developed whereby spent metallic fuel is reprocessed at the reactor site. The plutonium is not separated from the higher, radioactive actinides; they are recycled together in the reactor and never leave the reactor site. The long-lived radioactive minor actinide elements that otherwise would be disposed of as waste are irradiated in the fast breeder core and transmuted into elements with shorter half-lives, thereby lightening the burden of radioactive waste disposal. Because the actinides do not become part of the waste, the heat load on the waste repository can be reduced by a factor of 4 or more, thus greatly reducing the size and cost of the repository. In addition, because the plutonium is never separated from the actinides or transported from the site, the metallic fuel cycle can be a major means of reducing the threat of clandestine plutonium diversion into weapons.
The dry reprocessing methods, if commercialized, may have economic advantages over aqueous Purex reprocessing. The dry reprocessing methods can be applied not only to the FBR fuels - metallic, nitride, and oxide - but also to the oxide fuels of LWRs. Thus, dry reprocessing may bring new options to the overall fuel cycle.
The oxide fuel FBR and fuel cycle systems are in the prototype-to-demonstration stage of development. On the other hand, both nitride and metallic fuel FBRs and their fuel cycle systems are in the development-to-testing stage. Therefore, the commercial feasibility of these systems can only be evaluated after substantial progress has been made.
Unfortunately, the U.S. fast reactor program, which for the past two decades has been successfully developing the advanced liquid metal fast reactor and the metallic fuel cycle, is being canceled. This could be a serious blow to satisfying future world energy need in a safe, economical manner with minimal proliferation risks. It may be important, indeed vital, to future world welfare that the program be reinstated, either in the United States or elsewhere.
The increased use of nuclear power in the future will produce increased quantities of radioactive waste. Further, the use of nuclear radiation in other applications will produce a greater variety of radioactive waste materials. It is desirable, on the one hand, to reduce the amount of waste generated and, on the other, to treat and dispose of wastes safely under sound policies.
By far the largest amount of radioactivity is contained in the spent fuel discharged from reactors. The current reprocessing operation separates irradiated nuclear fuel into three streams: uranium, plutonium, and high-level radioactive waste consisting of fission products and transuranic elements (actinides). At present, all irradiated fuel and high-level wastes are kept aboveground in engineered stores, i.e., facilities that shield against the radiation and remove the heat generated by the wastes.
Proposals for longer-term management envisage the two steps of immobilization of the wastes in a stable chemical form and their ultimate disposal in deep underground repositories. Methods of immobilization have been developed, and there has been considerable research into the suitability of stable geologic formations. Further work is required primarily to demonstrate disposal and to aid in the selection of sites and the construction of repositories.
The removal of long-lived radioactive elements from wastes could reduce the environmental burden on repositories. Accordingly, methods of destroying the long-lived elements in high-level radioactive waste by transmuting them in nuclear reactors or accelerators are being researched. Although the actual implementation of transmutation disposal methods may well be an extremely long term objective, the demonstration of its potential would reduce concerns about the long life span of radioactive waste.
Apart from improving the technology of shallow-ground disposal, work on low-level wastes should seek to reduce the amount of wastes generated. This entails reviewing, rationalizing, and standardizing plant design, operation, and maintenance with the specific objective of reducing waste volumes and recycling them in the plant where possible.
In addition to the low- and high-level wastes being created today, another form is expected to become important - ultra-low-level radioactive waste that comes from the decommissioning of radioactive facilities. Here, it is necessary to set a critical value, below regulatory concern, and treat the wastes under a consistent international policy. The reuse of these materials as a means of reducing waste volumes should also be considered.
Like today's global disapproval of biological weapons development, considered unacceptable on moral grounds, the possession of nuclear weapons is likely to have the same connotation of being morally wrong. In the next 50 years, we shall witness a general evolution toward universal nonproliferation and ultimately the banning of nuclear weapons. It is likely that nuclear weapons states will ultimately eliminate their nuclear arsenals through disarmament agreements, and the nonnuclear weapons states will commit themselves to global nonproliferation either by international treaties, like the NPT, or by regional or bilateral agreements enabling full-scope safeguards in their territories.
Thus, development and utilization of nuclear power will evolve together with the implementation of nuclear disarmament and nonproliferation systems to allow all nations to objectively confirm that nuclear power is being used for peaceful purposes only.
There is no panacea, such as one single framework, that can resolve all the issues related to nuclear disarmament and nonproliferation. Instead, the most likely approach will be to systematically combine various international, regional, and bilateral arrangements and to strive for overall harmonization among them.
The core of these arrangements will remain within an international agreement of the NPT type, verified by means of a safeguards system carried out by a globally accepted organization like the United Nations IAEA. Such an agreement will also likely evolve into an international verification of nuclear disarmament to achieve a world free of nuclear weapons.
In view of an increasingly multipolar and regional international political scene, regional nonproliferation systems suited to the characteristics of their respective geographical areas (such as the Treaty of Tlatelolco, which covers Latin America) will become important supplements to international systems. In addition, conditions set forth in bilateral agreements will aid in reducing nuclear weapons proliferation. For instance, one of the criteria used by Japan in its Overseas Development Aid Program is a commitment by the recipient country to prevent nuclear proliferation. Import and export restrictions on nuclear-related equipment, such as those of the London Nuclear Suppliers Group, and safeguards against the theft of nuclear materials, applicable in accordance with the Treaty on Physical Protection of Nuclear Materials, are other examples of such accessory instruments.
Regional treaties, like those of Euratom and the Brazilian-Argentine Agency for Accounting and Control of Nuclear Materials (ABACC) (recently established for mutual inspection), have proved to be effective for nonproliferation. Asia, where the use of nuclear power will expand rapidly, could benefit from a regional system of that kind. However, "Asiatom," or other similar systems that have been proposed, will not provide for the monitoring of individual countries by a central organization, as in the case of Euratom. To help establish credibility, a system that takes into account the autonomous nature of each country will be gradually introduced.
Because the increasing energy demand in developing countries will account for the largest portion of future world energy requirements, many countries will launch nuclear power programs. The situation will necessitate an international system for plutonium control as one of the international systems for preventing weapons proliferation described previously. This issue has been the source of much debate since the International Nuclear Fuel Cycle Evaluation of the late 1970s. Recently, to ensure transparency in plutonium usage, priority has shifted from an initial objective of controlling excess plutonium by supplementing IAEA's safeguards to the objective of plutonium management. Such an objective may be attained through a system that recognizes each country's right to own, use, and/or trade plutonium but requires each country to deposit any excess plutonium that it is not using in internationally controlled facilities.
Development and practical experience have brought the safety technology of nuclear power plants to a higher level than that of any other type of power plant. Research and development are continuing, making more advanced nuclear safety technology available to plant designers and operators.
The WEC reference case projects an increasing number of countries using nuclear power. An objective for nuclear safety is to ensure that a consistent standard of advanced safety technology is applied to all the nuclear power plants in the world. Both institutional and technical measures are necessary to ensure safety at an adequate and improving level globally.
Institutional Measures
The principal responsibility for the safety of a nuclear facility lies with the operator of the facility. Each government is responsible for safety regulations that govern nuclear facilities within its country and also has the international obligation of preventing any accident that could affect other countries.
The World Association of Nuclear Operators (WANO) and similar organizations enable nuclear power plant operators to exchange information about operating experience and other matters. Such organizations are currently considering expanding their range of activities to encompass emergency support and peer reviews, where operators can state their opinions frankly. Information exchange using computer networks, event reports, seminars, workshops, and other activities of WANO will promote the building and use of a worldwide database on nuclear safety.
In addition, the International Nuclear Safety Advisory Group (INSAG) of the IAEA, the INSC, the International Nuclear Energy Academy, the International Nuclear Law Association, and the Pacific Nuclear Council provide important international cooperative mechanisms. These organizations help to promote the harmonization of safety concepts. An especially significant contribution is the Basic Safety Principles prepared by INSAG.
Industrialized nations using nuclear power have supported developing nations in the field of safety technology by training personnel with proper safety awareness and supplying safety-related equipment. Recently, the G-7 nations, acting in agreement, have begun to help nations with Soviet-designed nuclear reactors to enhance the safety of these reactors. Cooperative efforts in safety technology, whether operated continuously through institutions or set up to meet particular needs, will continue to be the core of international institutional measures to raise levels of safety technology.
The Nuclear Safety Convention has been available for ratification by governments since it was signed in the fall of 1994 and is expected to go into effect by 1997. It is based on the belief that nuclear safety should be approached from the perspective of worldwide linkage. The convention includes a range of guidelines for ensuring nuclear safety and calls for actions that conform with these guidelines. Specifically, the convention requires the signatories to apply internationally recognized principles of nuclear safety, adopts the INSAG Basic Safety Principles as the standard to be applied, and requires signatories to submit their implementation of safety measures to international verification by means of peer reviews. Implementation of this revolutionary convention is an important step to ensure worldwide nuclear safety. The INSC is making an important contribution by preparing a list of experts throughout the world who are competent to participate in reviews of safety.
Technical Measures
As the use of nuclear power broadens around the world, some technical directions to ensure safety merit special attention. These include human factors, equipment reliability, and the use of probabilistic safety assessment (PSA) in the design and operation of plants.
It is desirable to reduce reliance on the human factor in the operation and maintenance of nuclear facilities, recognizing that human error is a major factor in many situations. The human factor may be reduced first by selecting designs with an optimum combination of active safety features (by dynamic mechanisms) and passive safety features (by static mechanisms). Second, operating procedures during normal and anticipated transient operations should be automated to prevent erroneous human intervention.
The use of high-reliability equipment and components is a prerequisite for safety in nuclear facilities. This necessitates making advances in base technologies, such as materials and structures, and in quality assurance applied to design, fabrication, inspection, and construction. Countermeasures against aging and deterioration are also important to ensure that equipment and components maintain designed performance levels throughout their service life. These actions should be pursued to develop international standards.
Plant designs and operational procedures should be selected on the basis of quantitative evaluation, making full use of PSA.
Each nation must gain public acceptance of nuclear power and satisfy the technical, institutional, and international requisites for its use. The basis of public acceptance is public understanding. To achieve public understanding, accurate information on the benefits and risks of nuclear power must be provided to the public, in whose eyes the credibility of nuclear technology must be established, and must include the credibility of the information itself and of the organizations providing it. To establish credibility, it is necessary to provide objective and logical explanations as well as examples of past achievement in safety and cost-effectiveness that substantiate these explanations. It is also important to make accurate and prompt disclosure of information and to use decision making that involves the public.
A public information approach with a specific target offers the advantage of conveying information that is suited to the attributes of the target. Types of targets include
Among the opinion leaders, persons involved in education are especially important. They should provide the young, who represent the next generation of adults, with proper information for judging the use of nuclear power. Of particular importance is accurate information about nuclear energy and radiation in textbooks, which are a primary source of knowledge.
The understanding and cooperation of communities around the sites are essential preconditions to the siting of a nuclear facility. While central and local governments use legislative and other means to guarantee that the facility can coexist with the surrounding region, continuous communication after siting is needed, including the dissemination of information on plant operations.
When there is a serious accident at a nuclear power plant, as happened at Three Mile Island and Chernobyl, information is transmitted around the world instantaneously, generating anxiety among people and affecting countries all over the world. To respond effectively to such incidents, it is necessary to establish an international information system organized by public organizations that share reliable information.
(To be continued)
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