Nuclear Energy

Other Fuel Types

The focus here has been on UO2, which is the usual fuel for LWRs. Other fuel types are of interest, however, even if not widely used at present (see, e.g., Ref. 1 ). Possibilities include the following Mixed-oxide fuel (MOX). MOX fuel, a mixture of uranium and plutonium oxides, uses plutonium in order to exploit its energy content, reduce the stocks of potential weapons materials, or both (see Section 9.4.2). Metal alloy fuels. Metallic fuel, in the form of alloys of uranium, provide an...

The Shape of the Dose Response Curve Alternative Models

Extrapolation Supralinear

In the absence of direct evidence on the rate of cancer induction at low doses, estimates are made by extrapolation from observations at high doses. The extrapolation is couched in terms of a dose-response curve, namely an expression that relates excess cancer mortality to radiation dose. The curve is anchored at the bottom by definition There is zero excess if there is zero dose. It is anchored reasonably well at the top e.g., an excess lifetime cancer mortality risk of 0.10 for a dose of 1 Sv...

Water Dilution Volume for Spent Fuel

Nuclear Fuel Reconstitution

To compare the hazards from the various radionuclides in the waste, it has been common to plot the WDV values for individual radionuclides as a function of time since discharge of the fuel. An example of such a plot is given in Figure 10.3, copied from a 1983 National Academy of Sciences (NAS) study 13 .16 The results are presented in terms of the amount of water (in m3) needed to dilute the wastes in 1 MTHM of spent fuel.17 Although the activity falls by a factor of more than 1000 in the first...

Very HighTemperature Reactor VHTR

Reactor Nuclear Vhtr

The VHTR is a graphite moderated, helium-cooled reactor and, thus, it is a descendant of the HTGRs discussed in Section 16.4. As indicated by its name, the purpose of the VHTR is to achieve high temperatures. These are of importance in a variety of applications, with especially high stakes involved in its potential for the production of hydrogen (see Section 20.3.2). These reactors could also be used for electricity generation, and a particular reactor could be built for one or both of these...

Risk Models Absolute and Relative Risk

As suggested earlier, the cancer risk from a given exposure depends on a variety of factors other than the dose itself. For instance, the BEIR V report cites sex, attained age, age-at-exposure, and time-since-exposure as relevant parameters in determining risk 11, p. 166 . Further, the risk varies from organ to organ. The risk can be related to dose using either an absolute or relative risk model. In the absolute risk model, the risk depends on the dose. In the relative risk model, the risk...

Radiation Standards and Health Criteria Standards for the General Public

From about 1960 to 1990, the standard established in the United States and internationally was that the average additional exposure for members of the general population should not exceed 1.7 mSv yr, and for any individual, it should not exceed 5 mSv yr (excluding radiation workers). This was the maximum permitted dose, over and above the dose received from natural and medical sources. Not coincidentally, this limit for additional dose was about equal to the background from natural and medical...

Evolution of the TMI Accident

Over the next few days, the accident continued to unfold, with continued difficulty in establishing proper cooling conditions. There were some small releases of radioactivity outside the plant, as well as one misinterpreted report of radiation levels that led to the incorrect belief that there had been a large release. There was a great sense of emergency both at the site and in the surrounding area, as no one was willing to give unequivocal assurances that matters were under control. This led...

References

Garwin and Georges Charpak, Megawatts and Megatons A Turning Point in the Nuclear Age (New York Alfred A. Knopf, 2001). 2. Robert F. Mozley, The Politics and Technology of Nuclear Proliferation (Seattle, WA University of Washington Press, 1998). 3. National Academy of Sciences, Nuclear Arms Control Background and Issues, Report of the Committee on International Security and Arms Control (Washington, DC National Academy Press, 1985). 4. William Epstein, Indefinite Extension with...

General Approach

Although the above discussion has emphasized probabilistic measures for specifying reactor safety, the NRC the agency responsible for U.S. reactor safety has been reluctant to adopt probabilistic criteria in setting reactor licensing requirements. Nuclear reactor safety is regulated using a deterministic approach, which, in recent years, has been modified to risk inform the application of the deterministic criteria. As described by the NRC in 1995 The NRC established its regulatory requirements...

Separation Energies and Fissionability

The striking qualitative fact that thermal neutrons can produce fission in 235 U but not in 238 U is explained by rather small differences in the excitation energies of the nuclei 236U and 239U, produced when neutrons are absorbed in 235U and 238U, respectively. Consider, for example, the neutron-capture process in which the excited 236U nucleus is formed, followed by gamma-ray 5 In addition, spontaneous fission occurs for both 235U and 238U, but at rates that are very slow the respective...

Classification of Reactors by Generation

After a period of seeming indifference to the development of nuclear power, the U.S. DOE launched in 1998 a Nuclear Energy Research Initiative NERI , prodded in part by a recommendation from the President's Committee of Advisors on Science and Technology 11, p. 5-13 . The DOE in 1998 also established a Nuclear Energy Research Advisory Committee NERAC . The DOE's nuclear efforts have evolved into a multipronged program that includes three interrelated components 1 an effort for near-term i.e.,...

Production of Plutonium in Reactors

The production of plutonium is accomplished most effectively if the reactor has a high conversion coefficient. This means the use of heavy water or graphite as the moderator. These are better moderators than light water for plutonium production, because their cross sections for neutron capture are low and their relatively slow moderation rates gives more time for neutron capture in 238U see Section 8.3.2 . Most weapons programs have obtained their plutonium from graphite-moderated reactors the...

Types of Studies

Much has been learned from the long array of studies and analyses, but as discussed here, some crucial questions remain inadequately resolved. The most direct means of study is the observation of the effects of radiation on humans. There have also been numerous experiments on animals. Although the human and animal studies have provided considerable information on radiation damage at reasonably high doses, they have not led to clear-cut conclusions at low doses. The lower the dose, the smaller...

Radon Radiation Doses from Radon

As discussed in Section 3.5.1, indoor radon is the largest contributor to the radiation dose that the average person receives from natural or other sources. The UNSCEAR estimate of 1.3 mSv yr (the lower of the two estimates quoted in Table 3.5) corresponds to an annual collective dose of about 8 million person-Sv for the world population of 6 billion people. This is more than 10 times the estimated global dose commitment from the Chernobyl accident of roughly 600,000 person-Sv over a 70-year...

Historical Overview of Reactor Accidents

Despite the largely successful precautions taken to avoid nuclear reactor accidents, the record is not perfect. We list here the more important known reactor accidents, excluding accidents in submarine reactors and possible accidents in the former USSR and Soviet Bloc countries, other than the Chernobyl accident.1 The decision as to which accidents qualify as major accidents is somewhat arbitrary. In particular, ordinary industrial non-nuclear accidents are omitted. For example, in 1972 two...

Observations of Health Effects of Chernobyl Accident Overall Summary up to

Subsequent to the Chernobyl accident, there have been many studies of its health impacts, and studies are likely to continue for many decades. A succinct summary of current knowledge was presented in the 2000 Report of the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) in an Overview section on The Radiological Consequences of the Chernobyl Accident The accident at the Chernobyl nuclear power plant was the most serious accident involving radiation exposure. It...

Childhood Thyroid Cancer

The accident led to high thyroid exposures, primarily due to 1311 in the cloud of radionuclides from the reactor. The relatively short half-life of 131I (8.02 days) means that the dose was received within several weeks of the accident. The main pathways for this dose were through inhalation and consumption of milk or locally grown produce.16 High thyroid cancer rates began to be seen among children in the early 1990s. Sixty-two cases were observed in 1990 and the number of cases grew steadily...

Desalination of Seawater

Many parts of the world are faced with water shortages, as populations and standards of living rise and groundwater resources are depleted. Desalination of seawater offers a solution that is being increasingly employed. An IAEA document published in 2000 reported that in 1997 there were about 12,500 desalination plants in the world operating or under construction, with capacities ranging from the very small to over 400,000 m3 per day 22, Section 2.4 .14 Total world capacity was given as 23...

Federal Advisory Bodies

In addition to the main federal agencies with administrative responsibilities, there are a large number of groups and organizations with official advisory status. Some of these report to the individual agencies, some to Congress, and some to the public at large. They include bodies with broad responsibilities, of which nuclear waste studies are a relatively small component, as well as a number of boards and committees established specifically to advise on nuclear waste issues. These include the...

Congressional Role in the Site Selection Process Nuclear Waste Policy Act of

In response to the failure of the federal waste program to reach any clear and final decisions, Congress enacted the Nuclear Waste Policy Act (NWPA) of 1982, which was intended to put the program on a new footing 10 . Key provisions of this act were as follows Geologic sites. Geologic repository sites were confirmed as the leading choice for nuclear waste disposal. Designation of candidate sites. The Secretary of Energy was directed to nominate five sites for initial study. Following study and...

The Planned Yucca Mountain Repository Schedule for the Yucca Mountain Project

The path to be followed by the Yucca Mountain project was set forth in November 1989, when the Secretary of Energy issued a Reassessment of the Civilian Waste Management Program 12 . The revised plan included a prolonged period of iterative scientific investigations of the site to examine its suitability 13, p. 2 . If found suitable, the schedule called for the opening of the repository by 2010, following a series of intermediate administrative steps set out in the NWPA of 1987 a recommendation...

Studies of Health Effects of TMI

The release of radioactivity from the Three Mile Island plant and the resulting radiation exposures were too small to have produced any observable effects, if one accepts official accounts of the magnitude of the releases and standard dose-response relationships. One or even 10 cancer deaths would be lost among a total of over 300,000 natural cancer deaths. Nonetheless, there have been persistent claims of health problems from TMI. In response to some of the early concerns, the Pennsylvania...

Us Doe Near Term Deployment Roadmap

Lists of prospective reactor candidates have been developed in the recent initiatives by the U.S. DOE and in parallel international efforts. The reactors have been divided into those available for near-term deployment i.e., by 2010 or 2015 , and the Generation IV reactors for deployment after 2020. The U.S. thinking about the near-term was put on a formal footing in February 2002 with the announcement of the Nuclear Power 2010 program The Nuclear Power 2010 program, unveiled by the Secretary on...

Reactor Grade Plutonium as a Weapons Material Difficulties in Use of Reactor Grade Plutonium

It is clear, from the above-reviewed arguments and from a long history of less detailed but authoritative statements about the possibilities, that reactor-grade plutonium can be used to make an explosive device that would release a substantial amount of energy. This would be enough to create an explosion that would do great damage due to the blast itself, the heat and radiation produced in the chain reaction, and the radionuclides dispersed in its aftermath. It does not seem very likely that...

Countries with Nuclear Power But No Weapons

Many countries exhibit the other side of the coin they have nuclear power but do not have nuclear weapons. Some have not shown any inclination toward weapons e.g., Canada, Germany, and Japan .28 All have strong, comprehensive nuclear power programs and could easily develop weapons with no external aid. Sweden, which also has a strong civilian nuclear power program and technological base, embarked on a sophisticated program of weapons development, but the effort was abandoned before attracting...

Sequestration of Carbon Dioxide

The reduction of carbon dioxide production would be less of a priority were it possible to sequester the carbon dioxide after it is produced (i.e., to capture 2 It is often pointed out that fossil fuel energy is used in constructing the non-fossil-generating facilities. However, at most, this is a small correction. it before it enters the atmosphere and permanently dispose of it in a secure location). The amounts involved are large. For each GWyr of coal-fired electric power, there is a release...

Generation Costs and External Costs

A major reason for the decreased interest in the building of new nuclear power plants in recent years has been the relatively high cost of nuclear power. In this section, we will consider the role of costs in electricity generation choices, particularly in the context of the situation in the United States. The usually specified cost of electricity is the generation cost, namely the sum of the costs of constructing the plant, purchasing the fuel, and maintaining and operating the plant. All of...

Full Actinide Recycle

A fuel cycle based on the nearly complete extraction of plutonium and minor actinides collectively, the transuranic elements and their consumption by fission in fast reactors has been sketched in the MIT report The Future of Nuclear Power 46 . This cycle envisages a global nuclear economy in 2050 with a capacity of 1500 GWe based on a balanced combination of thermal and fast reactors. The thermal reactors are assumed to be LWRs, fueled by enriched uranium oxide. The fast reactors, undefined as...

The Impact of Reprocessing

The nature of the long-term waste storage problem is substantially changed if reprocessing is undertaken to remove plutonium and uranium from the waste. Plutonium removal would also reduce the contributions from americium-241 (241 Am) and neptunium-237 (237Np), because most of their abundance in the spent fuel derives from the decay of 241Pu. To use the extraction of plutonium to reduce the abundance of 241Am and 237Np, it is necessary to reprocess the fuel promptly, before an appreciable...

Reprocessing of Spent Fuel

The difficulties of making nuclear weapons from reactor plutonium are significantly reduced if the reactor fuel has already been reprocessed and the plutonium extracted. This is an argument against reprocessing. Without reprocessing, there is no separated reactor plutonium available for theft or diversion. Reprocessing has been opposed in the context both of possible weapons development by nations and theft by terrorist groups. Any country with facilities for reprocessing, gained as part of a...

Means for Obtaining Fissile Material

A nation that seeks to develop nuclear weapons has several options for obtaining fissile material Isotopically separating natural uranium to obtain uranium highly enriched in 235U. Operating a uranium-fueled reactor and extracting 239Pu from the spent fuel. Producing 239 Pu or 233 U by irradiating externally placed targets of uranium or thorium in the neutron flux emerging from a reactor. Obtaining the material from another country by purchase, friendly transfer, or theft. Methods for...

North Korea

North Korea illustrates how a country with a relatively small technical base may be able to go it alone in weapons development, given sufficient determination and some small initial help. North Korea began with a small light-water-moderated research reactor, its IRT reactor, received from the USSR in 1965 26 . It had an initial capacity of 2 MWt it was later upgraded to 4 MWt and then to 8 MWt 27 . North Korea also was helped by the USSR with small-scale reprocessing equipment, and a small...

Xenon Poisoning

Reference has already been made to the buildup of poisons as the fuel is used. A particularly interesting example is xenon-135 135Xe the cause of the xenon poisoning that for a brief time threatened operation of the first large U.S. reactors in World War II, which were designed to produce 239Pu.17 The first large reactor for this purpose went into operation in September 1944. After a few hours of smooth operation, the power level of the reactor began to decrease, eventually falling to zero. It...

Components of a Light Water Reactor

Siemens Bwr Grand Gulf Nuclear

The containment structure and enclosed components for a typical PWR and a typical BWR are shown schematically in Figures 8.2 and 8.3.12 The most conspicuous difference between them is the absence of a steam generator in the BWR. At the heart of the reactors, literally and figuratively, is the reactor core, contained within the reactor pressure vessel. The pressure vessel encloses three vital components The fuel itself, contained in many small fuel rods comprising the reactor core. The...

Other Indications of Performance

Following the Three Mile Island nuclear accident, the U.S. nuclear industry established the Institute for Nuclear Power Operations (INPO) designed to coordinate the industry's efforts to remedy existing problems and achieve safer and more economical reactor operation. As part of this activity, INPO monitors and reports upon various performance indicators. Results comparing 2001 to early years include the following 28 Unplanned scrams. Automatic shutdowns of a reactor, initiated by a failure in...

Level Widths and Doppler Broadening

The level width r, as seen from Eq. 5.5 , is the full width at half-maximum of the resonance peak that is, when En Eo r 2 the magnitude of the cross section is one-half of its maximum value. There is a minimum width for any level, the natural width rn.11 A typical width for an isolated resonance for neutrons interacting with 235U or 238U nuclei is about 0.1 eV. At nonzero temperatures, the actual level width is increased over the natural width by the thermal motion of the uranium nuclei in the...

Passive or Inherent Safety

A distinction is made between active and passive safety systems. An active safety system is one that depends on the proper operation of reactor equipment, such as pumps or valves. For example, active safety systems include the pumps and valves that control the water supply for emergency core cooling and the motors used to insert control rods in emergency shutdowns. Passive safety features are aspects of the system that are arranged to come into play automatically, without the action either of...

State See energy state

A heat exchanger used to produce steam in a pressurized water reactor. (See Section 8.2.1.) Stochastic. In radiation protection, a stochastic effect impacts individuals randomly the probability of a given impact on an individual (e.g., cancer induction) depends on the magnitude of the dose received. (See Section 4.1.3.) Subcritical. For nuclear fuel, having an effective multiplication factor that is less than unity. Supercritical. (a) For nuclear fuel, having an effective...

Comments From Peer Review Panels

At the request of the DOE, the Yucca Mountain TSPA program more specifically, the TSPA-SR was reviewed by a 10-member international review team (IRT) in a study that was organized by the Nuclear Energy Agency of the OECD and by the International Atomic Energy Agency and carried out in the second half of 2001 43 . The report made a large number of suggestions for improving the detailed information that goes into the TSPA as well as for making its results more transparent. However, its overall...

Trends in Burnup of LWR Fuel

Average burnup values for past years are shown in Table 9.1 along with the average projected for the fuel to be deposited at the Yucca Mountain waste repository. Overall, there has been a trend with time toward higher burnup, on average roughly doubling in the 25 years from 1973 to 1998 and projected to continue to rise. Thus, in a 1993 DOE projection, it was expected that the median PWR fuel burnup for standard assemblies would be about 43 GWd t in the year 2000 a value actually achieved in...

Uranium Consumption and Plutonium Production

In uranium-fueled reactors, there is a continual destruction of 235U, through fission and neutron capture, and buildup of plutonium isotopes through neutron capture and beta decay. The plutonium sequence starts with 239Pu, following neutron capture in 238U, and continues to include plutonium isotopes up to 242Pu, as well other heavy radionuclides for example, 241Am (atomic number Z 95), which is produced primarily from the beta decay of 241 Pu (T 14.39 yrs). Similarly, radionuclides of atomic...

High and Low Level Wastes

Nuclear wastes are sometimes divided into high-level and low-level waste, along with a separate category of transuranic waste High-level waste (HLW) is the highly radioactive fission and neutron-capture product of the nuclear fuel cycle. It may be in the form of either spent fuel or liquid and solid products from the reprocessing of spent fuel.1 (In some alternative definitions, spent fuel is in a category by itself. Many DOE tabulations reserve the term HLW for reprocessed wastes alone, and...

Measures of Waste Magnitudes

The inventories of wastes have been described earlier in terms of mass. However, several different sorts of measure can be used to describe the amount of nuclear wastes Mass. The most common mass measure for nuclear waste is the mass of the uranium in the initial fuel, more broadly designated as metric tonnes of initial heavy metal (MTIHM or just MTHM) (see Section 9.3.1). The fuel is held in cylindrical fuel rods, usually made of zircaloy, which are grouped in assemblies. The total mass of an...

Radioactivity in Waste Products Activity of Spent Fuel

Beta Particle Energy Curve

When a reactor is just shut down, there are extremely high levels of activity The actual activity at the moment of shutdown depends on the recent history of the reactor operation and is dominated by the decay of the short-lived radionuclides. These radionuclides, especially those with half-lives of the order of hours or days, are important for the heat budget of the reactor immediately after shutdown, and their role is crucial in reactor accidents in which there is difficulty in maintaining the...

Heat Production

The handling of the nuclear wastes is significantly complicated by the heat generated in the decay of the radionuclides. On occasion, it has been suggested that the heat from the wastes could be used constructively as a heat source (e.g., for direct warming of arctic installations). However, until there is more confidence in our ability to retain the wastes safely within their containers, it is unlikely that such applications will be considered prudent. The main interest in the heat generation...

General Considerations

In parallel with the move toward on-site dry storage in the United States, there have been continued efforts to establish one or more centralized facilities. Much of the impulse for this has come from utilities that do not wish to remain responsible for the spent fuel over long time periods. They point to the provisions of the Nuclear Waste Policy Act which stipulates that the DOE would begin to remove spent fuel from reactor sites by January 1998. With neither a permanent nor an interim...

Efforts to Find a MRS Site in the United States

Members of Congress made a number of proposals in the late 1990s to establish an interim storage site at Yucca Mountain, culminating in legislation passed in March 2000 that called for an interim facility which would begin receiving wastes at Yucca Mountain as soon as possible after NRC granted a construction permit for a permanent underground repository 10, p. CRS-5 . However, this legislation was vetoed by President Clinton on the grounds that this step should not be taken before a decision...

Nuclear Waste Transportation Waste Transportation Plans

The prospect of large amounts of spent fuel being transported from the reactor sites to a centralized location whether an interim facility or a permanent repository has led to a debate over the dangers that might result. The shipments, from many parts of the country, would have to pass through numerous governmental jurisdictions. Unless a public consensus develops that the dangers posed by these shipments are small, political and legal challenges could complicate the implementation of any...

Thermal Loading of the Repository

One of the key decisions in the planning of a geologic repository is the choice of the desired temperature profile for the repository region, as a function of time and location. The temperature profile is controlled by the density with which the heat-dissipating wastes are placed in the repository, the time delay before their placement, and the ventilation if any. The overall plan constitutes the thermal loading strategy. For a fixed waste inventory, this strategy is important in determining...

The Nuclear Waste Fund

The fee of 0.1 kWh charged against nuclear-generated electricity now produces a revenue of roughly 750 million yr for civilian waste management essentially the Yucca Mountain project. From FY 1983 through FY 1999, the fees totalled 8.3 billion 19, p. 3 . The expenditures have lagged far behind. This relatively low rate of spending on Yucca Mountain has been criticized as having impeded progress on important parts of the program including, e.g., the study of the waste packages 20, p. 6 . The...

Engineered Barriers The Waste Package

As discussed in Section 11.2.5, in the first years of planning for the Yucca Mountain repository, the goal of waste canister design was to contain the radionuclides for 1000 years. This was a relatively modest goal but sufficed if enough reliance could be placed on the natural barriers for long-term protection. However, after the early 1990s, the DOE planning shifted to the goal of a robust waste package, designed to retain its integrity for much longer than 1000 years. This shift was...

Acronyms and Abbreviations

Advisory Committee on Nuclear Wastes U.S. NRC Agreed Framework U.S. and North Korea Advanced Gas-Cooled Graphite-Moderated Reactor also AGR Advanced Passive PWR or Advanced PWR 600 MWe approx Advanced Passive PWR or Advanced PWR 1000 MWe approx Atomic Safety and Licensing board U.S. NRC Atomic vapor laser isotope separation Arbeitsgemeinschaft Versuchs Reaktor Biological Effects of Ionizing Radiations BNL Brookhaven National Laboratory BRWM Board on Radioactive Waste Management National...

Human Population and Impact

An underlying matter that consciously or not may figure in the nuclear debate is our feeling as to the desirability of satisfying the energy demands of a world population that was 2.5 billion in 1950, was 6 billion at the beginning of the 21st century, and appears headed to 9 billion or more in 2050. Nuclear power is pointed to as an aid in meeting these demands. However, some may take that as a curse instead of a blessing. It raises the question of the size of the population that we would...

Conversion Ratio and Production of Plutonium in Thermal Reactors

With uranium fuel, 239Pu is produced by the capture of neutrons in 238U see Section 5.1.1 . This provides a means of obtaining 239Pu for possible use in weapons or in other reactors. It also contributes fissile material which is consumed in the reactor before the fuel is removed, supplementing the original 235U in the fresh fuel. The rate of 239Pu production is described in terms of the conversion ratio, which is defined in general terms as the ratio of the number of fissile nuclei produced to...

Broad Themes in the Generation IV Program

Overall, the systems have a number of specific themes, although these are not reflected in every one of the reactors types. Table 16.2. Generation IV nuclear reactor systems, selected by GIF as being the most promising. (NA Not Applicable) Table 16.2. Generation IV nuclear reactor systems, selected by GIF as being the most promising. (NA Not Applicable) Moderator only for case of thermal spectrum. Source Ref. 19 . Moderator only for case of thermal spectrum. Source Ref. 19 . For each of the...

The Generation IV Program Overview of the Program Goals of the Program

DOE inaugurated in 1999 a new program to explore possibilities for future reactors that are substantially more attractive than present reactors in terms of sustainability, economy, safety, and proliferation resistance. The contemplated reactors are the so-called Generation IV reactors. The goal has been to have the reactors ready for commercial deployment in two or three decades, with target dates set in the 2020-2030 time frame 19 . The dates are sufficiently far in the future to give...

Methods for Enrichment

The leading enrichment methods in terms of past or anticipated future use are as follows 13 Gaseous diffusion. The average kinetic energy of the molecules in a gas is independent of the molecular weight M of the gas and depends only on the temperature. At the same temperature, the average velocities are therefore inversely proportional to M. For uranium in the form of UFg, the ratio of the velocities of the two isotopic species is 1.0043.14 If a gas sample streams past a barrier with small...

High Temperature Gas Cooled Reactors HTGR Options

Planned high-temperature, gas-cooled reactors (HTGR) are carbon moderated and helium cooled. The use of carbon and helium allows the reactor to operate at higher temperatures than can be reached in LWRs, giving higher efficiencies in electricity generation about 45 in HTGRs, compared to 35 or less for LWRs 14, p. G-1 . The high temperatures can also be an advantage in applications making direct use of the heat. For instance, one of the Generation IV reactors is an HTGR intended to operate at...

Hydrogen as a Fuel

A major attraction of hydrogen as a fuel is its cleanliness Combustion of hydrogen leaves no waste product other than water (H2O). As such, it has 11 An earlier review (1976) listed nine such cycles, although it did not include the I-S cycle 24, p. 287 . 12 1 normal m3 (Nm3) has a mass of 0.090 kg and a combustion energy of 12.8 MJ. been urged as an automotive fuel in vehicles powered by hydrogen fuel cells, as well as a source of electricity or heat for the home (see, e.g., Ref. 27 ). The use...

Nuclear Power Since Trends in Nuclear Growth

Trends Nuclear Energy

Worldwide nuclear power generation grew rapidly from the 1970s through the 1980s and then slowed. Details on the growth from 1973 to 2000 are shown in Table 2.4 for the world, Western Europe, and the Far East, as well as for the three countries with the greatest individual outputs of nuclear energy. Looked at broadly, one sees a rapid expansion in the 1970s and 1980s followed by a marked slowdown in the pace of growth in the 1990s. World generation excluding the former Soviet Union (FSU) and...

Event Trees and Fault Trees

Psa Fault Trees

The PRA tools used in the RSS were event-tree analyses and fault-tree analyses. In an event-tree analysis, one imagines the occurrence of some initiating event and traces the possible consequences. We illustrate in Figure 14.1 the event tree for studying the consequences of a major pipe break, following which the emergency core-cooling system ECCS must operate successfully for damage to be avoided 12, Main Report, p. 55 . The worst case in this example would be the electric power failing to...

Ieanea Compilation of Innovative Reactors

The International Energy Agency and Nuclear Energy Agency7 published a report in 2002 with a compilation of an Illustrative List of Innovative Reactor Designs 20, Table 2-1 . Thirty-six reactors were listed. They can be classified in several ways By type. The 36 reactors included 9 light water reactors, 9 liquid metal fast reactors, 4 gas-cooled reactors, 5 reactors for district heating only no electrical output , 3 molten salt reactors, 2 heavy water reactors, and 4 reactors of other types. By...

Accelerator Driven Fission

In the early 1990s, a quite different approach was suggested for obtaining energy from fission. In this approach, a high-energy beam from a proton accelerator produces a large number of neutrons in collisions with heavy nuclei, in a process known as spallation. A geometric arrangement is used so that the spallation neutrons irradiate uranium or thorium, initiating fission. The configuration of fissile material is subcritical, and the number of neutrons decreases in successive fission...

Problems Facing Nuclear Energy

The decline in the growth of nuclear power in recent years can be attributed to both a less favorable economic environment and concerns about its overall safety. The nuclear decline is not universal, with a very heavy reliance on nuclear power in some counties most notably, France and continuing construction programs in others, especially in Asia. Nevertheless, for the world as a whole, there is a dramatic difference between the expectations of 1970 and the reality of today. Some of the reasons...

Types of Nuclear Bomb

Fission Bomb Design

The minimum mass sufficient to sustain a chain reaction is known as the critical mass. This is the mass for which the neutrons produced in fission just balance the neutrons that are absorbed or escape. For an effective nuclear weapon, the critical mass must be assembled quickly. Two general approaches are used to achieve this, as pictured in Figure 17.1 Fig. 17.1. Schematic sketches of fission bomb designs top, gun-type bomb bottom, implosion-type bomb. From Paul P. Craig and John A. Jungerman,...

Defensein Depth

A special kind of redundancy is sometimes singled out as being at the heart of nuclear safety. This is the reliance on multiple barriers or defense-in-depth, which is described as a hierarchically ordered set of different independent levels of protection 6, p. 109 . The principle of defense-in-depth is seen in considering the barriers that prevent or minimize exposures due to the release of radioactivity from a reactor The UO2 fuel pellets retain most radionuclides, although some gaseous...

Reactors Listed in the Near Term Roadmap

The reactors listed in Table 16.1 fall into several groups Evolutionary LWRs that have been design certified by the U.S. NRC. The ABWR and the System 80 PWR reactor became in 1997 the first reac- Table 16.1. Reactors considered by the U.S. DOE's Near-Term Deployment Group 2001 , arranged by the NTDG's assessment of their deployability. Reactor Designationa Sorted by Deployability Advanced Boiling Water Reactor BWR Advanced Passive-600 AP600 PWR Advanced Passive-1000 AP1000 PWR Pebble Bed...

System Reactor

Three System 80 reactors, which are forerunners of the System 80 reactor, were put into operation in the United States in the 1980s the Palo Verde plants in Arizona. They were designed and built by the Combustion Engineering Company. The System 80 reactor is slightly larger than the System 80 1350 MWe versus about 1245 MWe and incorporates changes for improved safety. It was designed by the combined Combustion Engineering and Asea Brown Boveri companies, but in subsequent reorganizations of the...

Innovative Light Water Reactors General Considerations

The innovative LWRs that are under consideration are simpler, and in the first versions they were smaller, than the current generation of LWRs. In the United States, two designs led in the early development, initially with support from the DOE and the Electric Power Research Institute (EPRI) the West-inghouse AP600 and the General Electric SBWR. Both reactors were about 600 MWe in size. Special features of this category of reactors, as summarized by Forsberg and Weinberg, include the following...

The Recent Trend to Larger Reactors

In the countries that have had the strongest programs of reactor construction in recent years, the new reactors are quite large 4 In 2000, France put into operation four PWRs the so-called N4 reactors each with a capacity of about 1450 MWe. Four ABWRs, each with a capacity of over 1300 MWe, are under construction two in Japan and two in Taiwan. South Korea has two 1000-MWe PWRs under construction that are near-ing completion. Much of the tangible industry planning appears to continue to favor...

Comparison Between the AP and AP

The motivating factor in going from 600 to 1000 MWe is cost. Westinghouse expects that construction costs would increase only modestly, compared to 9 The IRWST has a capacity to provide cooling for 1 h before boiling, after which the escaping steam condenses on the interior of the containment and is returned to the IRWST 27 . the increase in output. In consequence, the expected electricity cost would drop from an estimated 4.1-4.6 kWh to about 3.0-3.5 kWh a reduction deemed necessary for...

Volcanic or Igneous Activity

Igneous activity, also referred to as volcanism, involves the transport of molten rock (magma) through the Earth's crust. The passage of magma through the Yucca Mountain repository could lead to the release of radionuclides in two ways 15, p. 4-476 Eruptive volcanism. In an eruptive event, magma can pass through the repository region and rise to the Earth's surface. The hot magma would damage the waste packages, entrain radionuclides in the material that is emitted into the atmosphere, and fall...

Dry Storage of Spent Fuel at Reactor Sites

Nuclear Plant Palisades Storage Casks

In U.S. dry storage systems, the spent fuel rods are transferred to special casks when the total activity and the heat output are reduced enough for air cooling to suffice.1 This solves the problem of limited cooling pool capacity and is an option that can be implemented pending decisions on the establishment of centralized facilities. It also defers the contentious issue of transportation 1 In some other countries, and for the fuel from the U.S. reactor at Fort St. Vrain, the spent fuel is...

The Thermal Loading of the Repository

The importance of thermal loading strategy for a geologic repository was discussed in Section 11.2.4. Yucca Mountain planning during most of the 1990s was based on the assumption that the repository would operate in an above-boiling mode. However, more recently, increased consideration has been given to the possibility of operating at lower temperatures. Background on thermal issues is provided in White Paper Thermal Operating Modes, a study document prepared for the DOE and issued in February...

Nucleosynthesis

The existence of natural radioactivity (i.e., the formation of the radionuclides found in nature) cannot be understood in isolation, apart from the understanding of the formation of the stable nuclides. They were produced in the same processes of nucleosynthesis, primarily in the evolution and explosion of stars. Only matters of relatively fine nuclear detail make some species stable and some unstable. A sketch showing the relationship between the atomic number and atomic mass number for the...

NRC Analysis Nureg Analysis Procedure in NUREG

A further step in the development of reactor safety analysis methods in the United States was marked by the publication in 1990 of the NRC report Severe Accident Risks An Assessment for Five U.S. Nuclear Power Plants, also known as NUREG-1150 11 . Five LWRs were analyzed in detail for this study. These are in some sense typical of LWRs in the United States, but the reported results are specific to the individual reactors. In NUREG-1150, an explicit distinction was made between internal and...

Use of Mixed Oxide Fuel

The fuel manufactured from the output of the reprocessing phase is generally a mixture of plutonium oxides and uranium oxides, with 3 to 7 PuO2 and the remainder UO2. It is called a mixed-oxide fuel or MOX. At the higher 239Pu enrichments, a burnable poison would be added to the fuel to reduce its initial reactivity. Due to differences in the nuclear properties of 239Pu and 235 U, most LWRs are limited to using only about a one-third fraction of MOX Table 9.4. Reprocessing plants for commercial...

Effects of the TMI Accident Core Damage and Radionuclide Releases

In retrospect, several major aspects of the Three Mile Island accident were not fully appreciated at the time and might seem to be in conflict There was very little release of radioactivity and very little exposure of the general population. According to the Kemeny Commission, the maximum estimated radiation dose received by any one individual in the off-site general population (excluding the plant workers) during the accident was 70 millirems three TMI workers received radiation doses of about...

Adopted Enrichment Practices

During World War II, not knowing which method would be the most effective, the United States embarked on both diffusion and electromagnetic separation, as well as still another method that was later discarded (namely thermal diffusion, which exploits temperature gradients). The electromagnetic separation technique was abandoned in the United States after World War II and was widely considered to be obsolete. However, it was found in 1991, after the Gulf War, that Iraq had been secretly using...

Disposition of Excess Fissile Material from Weapons Programs

With the end of the cold war in the 1990s, the United States and Russian governments concluded that they had more nuclear weapons and more weapons-grade fissile material than were needed for security. In fact, it could be argued that their security would be improved by reductions, because there would be less chance of the accidental or intentional misuse of the weapons or the diversion of stock-piled materials. This conclusion led to the START I and START II treaties under which each country...

Heat Removal

Normally, the core is cooled by the flow of helium. If the coolant flow stops (i.e, there is a loss-of-coolant accident) the reactor will be shut down by control rods, but heat will continue to be produced by radioactivity in the core. Because graphite is a relatively poor moderator and has a low cross section for neutron absorption, the ratio of moderator mass to fuel mass is much larger in an HTGR than in a LWR. The core, therefore, has a high heat capacity, which limits the rate at which the...

Standards for Future Reactors How Safe Is Safe Enough

There is no universal answer to the question of how safe is safe enough The acceptability of a given risk depends on circumstances, including the risks involved in alternative options. Many auxiliary factors enter, including but not limited to whether the risk is created by one's own actions, the actions of external institutions, or the actions of nature. Experience suggests that, at any level of numerically calculated danger, risks associated with nuclear energy are far less acceptable to the...

Risk Coefficient

The most serious long-term effect of exposures at doses below the 1 Gy (or 1 Sv) region is an increased risk of cancer. This is a stochastic effect because the chance of cancer depends on the magnitude of the dose. There is strong evidence of increased risk down to 0.1 or 0.2 Sv, but there is considerable uncertainty about the effects of smaller doses as discussed at length below. To fill in the picture, extensive efforts have been made to determine the cancer rate as a function of radiation...

Design Features of the AP

Ap1000 Irwst

The AP600 was designed to be simple in configuration and relatively inexpensive to build.8 Part of the savings comes from modular construction, in which components are built and to some extent assembled off-site, substantially reducing the construction time at the reactor site itself. When compared 8 This discussion is based primarily on information from Westinghouse, including published documents and private communications with Ronald P. Vijuk. to conventional PWRs, the design simplifications...

Supercritical WaterCooled Reactor SCWR

Schematic Nuscale Reactor

Conventional light water reactors use steam to drive the generating turbines. In PWRs, the steam is produced in separate steam generators. In BWRs, the steam is produced in the pressure vessel, making a separate steam generator unnecessary but requiring a pumping system to circulate the water through the core. The SCWR operates at a high temperature where water is in a supercritical state and thus is a single-phase fluid. There is no need for either the PWR's steam generator or the BWR's...

Reactor Deployment Since the Mids

The picture changed abruptly in the mid-1970s. In contrast with the 4-year period from 1971 to 1974, when 129 reactors had been ordered, only 13 reactors were ordered during 1975-1978. After 1978, new orders ceased entirely and all reactors ordered after 1973 have been canceled. The de facto moratorium on commercial reactor orders has continued in subsequent years, and at the time of this writing (early 2004), no new orders are in clear prospect. A major factor in this change was a sharp drop...

Special Issues in Considering Waste Disposal The Decision Making Process Attitudes Toward Science and Experts

Immediately after World War II, experts and scientists, in particular were held in high regard in the United States. U.S. military successes in the war and the technological accomplishments that contributed to those successes helped to form a prevailing view that scientists and engineers knew what they were doing and could be trusted in terms both of their competence and their intentions. There was a broad, if not unanimous, trust in the establishment of which scientists had become a key part....

Interaction of Fuel with

Nuclear Energy Drawings

A concern with HTGRs is the possible entry of air into the reactor and the resulting oxidation of the hot graphite. This possibility is discounted in the description of the PBMR provided in the Near-Term Deployment Roadmap Any concern of fire in the graphite core is avoided by showing that there is no method of introducing sufficient oxygen into a high-temperature core gt 1000 C to achieve sustained oxidation. This 16 If heating of the graphite or loss of the helium has any appreciable effect...

Alternative Host Rocks for a Geologic Repository

A large number of different types of rocks have been considered for waste repositories. There is no single overall best choice, as evidenced by the different choices made by different countries (see Section 11.4). Among the physical factors that go into the consideration of a particular rock formation are the extent to which water entry would be inhibited, its retardation of the flow of any escaped radionuclides, and its behavior when heated by the repos itory wastes. Rocks that have been...

International Approaches

The stricture that each country should dispose of its own wastes is driven primarily by the expected unwillingness of potential hosts to accept foreign wastes. Nonetheless, there have been suggestions for international solutions Remote islands. Given local opposition to waste disposal sites near populated areas, it has been suggested that underground repositories be placed on remote islands. Such a plan would face difficulties in identifying a geologically suitable site, overcoming...

The Three Mile Island Accident The Early History of the TMI Accident

Tmi Diagram

The Three Mile Island TMI accident occurred in one of two similar reactors at the Three Mile Island site in Pennsylvania.7 The accident was in the second 4 The number of fatalities is in question, given the uncertainties surrounding the effects of radiation at low doses and dose rates, but in the discussion of these accidents, we quote numbers based on the adoption of the linearity hypothesis see Section 4.3 . 5 This summary is based largely on an IAEA report prepared shortly after the accident...

Calculation of Capital Charges

If a plant could be built instantaneously, its cost would be the sum of the base construction cost, also known as the engineering, procurement and construction cost, together with a contingency cost. This constitutes the overnight cost. However, a plant cannot be built instantaneously and so-called time-related charges must be added, namely interest on the investment and the escalation of costs during the period of construction. For example, in a study by the DOE-sponsored Near Term Deployment...

Preface to the Second Edition

This second edition represents an extensive revision of the first edition, although the motivation for the book and the intended audiences, as described in the previous preface, remain the same. The overall length has been increased substantially, with revised or expanded discussions of a number of topics, including Yucca Mountain repository plans, new reactor designs, health effects of radiation, costs of electricity, and dangers from terrorism and weapons proliferation. The overall status of...

The Range of Terrorist Threats

Potential terrorist attacks, including attacks using nuclear bombs or carried out against nuclear facilities, have long been a matter of concern. However, the events of September 11, 2001 have greatly heightened the sense of concern. The emergence of Al Qaeda has demonstrated the existence of a large terrorist group that appears to have access to skilled and dedicated personnel and ample financial resources. The willingness of individual terrorists to die in their attacks broadens the scope of...

The Nature of the Nuclear Terrorist Threat

The influential book Nuclear Power Issues and Choices (NPIC) published in 1977 as a report of a Ford Foundation-sponsored study devoted a full chapter to Nuclear Terrorism 23 . The concerns that were reflected in NPIC about nuclear weapons proliferation and terrorism had already led President Ford in 1976 to call for a deferral of the reprocessing of spent nuclear fuel 24, p. 117 . Less than a year later, the new Carter administration decided to terminate support for reprocessing and it has...

Other Countries The Former Soviet Union

The breakup of the Soviet Union left nuclear reactors in a number of the new states, mostly in Russia and Ukraine, but also two in Lithuania and one each in Armenia and Kazakhstan. The 1986 Chernobyl accident led to a cutting back of reactor construction in Russia. Nonetheless, six reactors that had been started before the accident were connected to the grid in Russia between the time of the accident and the end of 2001 five of which were 950-MWe PWRs and one was a 925-MWe RBMK reactor...

Uranium and Nuclear Weapons

It is considerably simpler to make a bomb using enriched uranium than to make one using plutonium, and uranium may be becoming the material of choice for countries or groups that want to build a bomb with minimal effort and chance of detection. The fission cross section, af, and the average number of neutrons per fission, v, are both somewhat smaller for 235U than for 239Pu, making the critical mass larger see Table 17.1 . However, premature detonation caused by neutrons from spontaneous...

Fast Breeder Reactors Plutonium as Fuel for Fast Breeders

A thermal breeder reactor is not possible using 239Pu due to the high ratio a of the capture cross section to the fission cross section for thermal neutrons.17 However a fast breeder reactor is possible. It relies on a chain reaction in which the neutrons are not thermalized but instead produce fission at relatively high energies. If 239Pu is the fissile fuel, the cycle uses 238U as the fertile fuel and 239Pu is both consumed and produced in the reactor. The cycle is started using 239Pu...

Fuel Temperature Feedback Doppler Broadening

Although we have been tacitly treating the nuclei of the fuel as motionless targets undergoing bombardment by neutrons, this is not a precise description. The uranium nuclei are in thermal motion, with an average speed that increases as the temperature increases. The result is to increase the effective cross section for neutron absorption in 238U if the temperature of the fuel rises, through the Doppler broadening of the absorption resonances see Section 5.2.3 . The number of neutrons available...

Recent Developments in Individual Countries

Despite the overall negative recent history for nuclear power, there were favorable developments in some countries France added 10 new reactors from 1990 through 2002. These were large reactors, each 1300 MWe or more. In most of this period, nuclear power Czech Republic (Temelin-2). Construction had started in 1996 or later on the Asian reactors and in 1987 on the Czech reactor. accounted for more than 75 of France's electricity generation, and France was an exporter of electricity to its...