Energy States and Photons

One of the great breakthroughs of early 20th-century physics, embodied in the Bohr model of atomic structure, was the recognition that atoms can exist only in certain states or configurations, each with its own specific energy. In the simple Bohr picture of the hydrogen atom, different states correspond to electron orbits of different radii, each with a well-defined energy equal to the sum of the kinetic and potential energies of the electron in its orbit. This very simple mechanical picture...

David Bodansky

David Bodansky Department of Physics University of Washington Seattle, WA 98195 USA Library of Congress Cataloging-in-Publication Data Bodansky, David. Nuclear energy principles, practices, and prospects David Bodansky. 2nd ed. p. cm. Includes bibliographical references and index. ISBN 0-387-20778-3 (hc alk. paper) 1. Nuclear engineering. I. Title. TK9145.B54 2003 ISBN 0-387-20778-3 Printed on acid-free paper. 2004, 1996 Springer-Verlag New York, LLC. AIP Press is an imprint of Springer-Verlag...

Energy Relations in Alpha Particle Emission

In the decay of 238U, about 77 of the alpha particles are emitted with a kinetic energy of 4.20 MeV and 23 with an energy of 4.15 MeV. For the 4.20-MeV alpha particle, which corresponds to a transition to the ground state of 234Th, Ea + ETh M(238U) - M(234Th) - M(4He) c2, (A.11) where the mass M is the atomic mass of the species in question, and Ea and ETh are the kinetic energies of the alpha particle and thorium nucleus, respectively. The 4.15-MeV alpha particle corresponds to a transition to...

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...

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...

The Uranium Series

The uranium series, headed by 238U, includes two radionuclides of some special importance, in addition to 238U itself. One of the progeny, 226Ra, was the source of the intense activity found in uranium ore in the early studies carried out by the Curies. It appears as a strong source (i.e., one with a high specific activity), because of its intermediate half-life of 1600 years. A longer half-life would reduce the specific activity. A much shorter half-life would have made it harder to notice in...

Radioactive Series in Nature The Occurrence of Three Series

The radioactive decay series are groups of radioactive nuclei that arise from the production in nucleosynthesis of long-lived alpha-particle emitters. The head of each series is either a direct product of nucleosynthesis or a remnant of the synthesis of short-lived parents. As it decays, it feeds a set of radioactive progeny which decay by either alpha-particle or beta-particle emission. In alpha-particle decay, the atomic mass number A is reduced by 4. In beta-particle decay, A is unchanged....

Radioactive Products of Nucleosynthesis

The material of the solar system was formed by several generations of such synthesis processes, possibly including the explosion of a supernova near the protosolar nebula shortly before the formation of the Sun and the condensation of the planets. In the 4.6 billion years since the formation of the Earth, any nucleosynthesis products with short half-lives have disappeared. The only naturally radioactive relics of nucleosynthesis are nuclei that have very long half-lives or are decay products of...

Specific Activity

A radioactive substance can be characterized in terms of its specific activity, S, defined as the activity per unit mass. The specific activity of a radioactive species (in Bq g) is where N is the number of nuclei per gram, M is the atomic mass of the radionuclide (in atomic mass units, u), T is its half-life (in seconds), and Na is Avogadro's number. Specific activities for selected radionuclides are given in Table 3.2. As follows from its definition, and as exhibited in Table 3.2, high...

Dose Equivalent Rem and Sievert

Biological harm is not determined solely by the total energy deposition per unit mass. It is found also to depend on the linear energy transfer (LET) rate, where the LET rate is the ratio of energy deposition by an individual particle to the distance it traverses.7 It is alternatively referred to as the density of ionization. Greater density corresponds to more localized damage to the tissue and leads to more harm per unit energy (except at very high density where there is a saturation effect)....

Basic Units of Exposure and Dose Ionization Measure of Exposure The Roentgen

Historically, radiation exposures were first expressed in terms of the roentgen (R). The definition was based on the ionization produced by X-rays or gamma rays in air.4 This definition made one R equivalent to the deposition of 87 ergs per gram of air. Historically, the roentgen was a convenient unit to introduce because early work with radiation was concerned primarily with X-rays, and radiation was commonly detected with instruments that measured the amount of ionization produced in air.

Radiation Exposure and Radiation Dose

Radiation hazards are related to the magnitude of the radiation exposure or radiation dose incurred. The two terms are often treated in casual usage as interchangeable, but, in fact, their definitions are quite different. The dose is a quantitative measure of the impact of radiation, closely related to the energy deposited by incident radiation. Exposure is now used in two senses (1) in a specialized sense in connection with the roentgen unit (see Section 3.2.2) 2 Such health spas can be...

Brief History

Radioactivity and the associated radiation exposures are sometimes thought of as environmental problems that have been created by modern science and technology.1 However, substantial amounts of radioactivity exist in nature and have existed on Earth since its original formation. All biological species evolved on Earth, for better or worse, in this radioactive environment. Radioactivity could be plausibly termed the oldest pollutant if one chooses to describe an integral part of the natural...

Failures of Prediction

In the preceding discussions, the trends of events for nuclear power has been reviewed, and such discussions may appear to suggest the nature of future trends. However, any suppositions as to how nuclear power will develop over 1965 1970 1975 1980 1985 1990 1995 2000 Fig. 2.5. Comparison of U.S. nuclear capacity, projected in 1972 and actual. 1965 1970 1975 1980 1985 1990 1995 2000 Fig. 2.5. Comparison of U.S. nuclear capacity, projected in 1972 and actual. the next several decades should be...

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...

National Programs of Nuclear Development France

France is widely cited as the leading success story for nuclear power. Each year since 1986, nuclear power has accounted for over 70 of electricity generation in France. Another large fraction, averaging about 15 , but with considerable year-to-year variations, has come from hydroelectric power. Therefore, France is virtually saturated in terms of the replacement of fossil fuels. Taking advantage of its ample nuclear capacity, France now exports substantial amounts of electricity to its...

Planned Construction of New Reactors

The pace of reactor construction is now quite slow. According to an IAEA compilation, 32 reactors were under construction as of November, 2003 with a total capacity of 26 GWe. Completion of all these reactors would add 7 to the then existing capacity of 360 MWe, and if accomplished within 5 years, the Table 2.5. Nuclear reactors under construction as of November, 2003. Table 2.5. Nuclear reactors under construction as of November, 2003. average annual rate of increase would be about 1.4 ....

Nuclear Power Since Trends in Nuclear Growth

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...

Discovery of Fission

Prior to the actual discovery of the neutron in 1932, it had long been suspected, in part due to a suggestion by Ernest Rutherford in 1920, that a heavy neutral particle existed as a constituent of the atomic nucleus.1 The discovery of the neutron, as with many of the early discoveries in nuclear physics, was accidental. In the bombardment of beryllium by alpha particles from a naturally radioactive source, a very penetrating radiation had been observed in experiments begun in 1928. In view of...

Thermal Neutrons

In many reactors, a succession of elastic collisions with the nuclei of the so-called moderator (see Section 7.2) reduces the neutron energies to lower and lower values as the neutrons impart some of their kinetic energy to the target nuclei. Ultimately, the thermal motion of the nuclei in the reactor cannot be neglected, and the neutron energies then approach a Maxwell-Boltzmann distribution (qualitatively, a bell-shaped curve), characteristic of the temperature of the fuel and moderator. This...

Competition Between Capture and Fission

For neutrons in a nuclear fuel, such as uranium or plutonium, the most interesting reactions are fission and capture. (Elastic scattering in the fuel changes the neutron energy only slightly, due to the high mass of the target nuclei, and has little importance.) If the goal is fission, as it is with 235U or 239Pu, capture has the effect of wasting neutrons. The ratio of the capture cross section to the fission cross section is therefore an important parameter. It is commonly denoted by the...

Reaction Cross Sections Definition of Cross Section

The neutrons in a reactor may interact with a variety of target nuclei. Possible reactions are elastic scattering, capture, and, in some cases, fission or inelastic scattering. Which of these reactions occurs for an individual neutron is a matter of chance. The probability of each outcome is commonly couched in terms of the reaction cross section a for the event. The term cross section suggests an area, and the reaction cross section for a given reaction can be thought of as the effective...

Neutron Capture

In the first stage of many reactions, the neutron combines with the target nucleus to form an excited compound nucleus. The term neutron capture is usually restricted to those cases where the excited compound nucleus decays by the emission of gamma rays. For example, again taking 238U as the target nucleus, neutron capture leads to the formation of 239U Here, the compound nucleus is 239U*, where the asterisk again indicates an excited state. The number of gamma rays emitted in the de-excitation...

Elastic Scattering

In elastic scattering, a neutron and nucleus collide with no change in the structure of the target nucleus (or of the neutron). An example, the elastic scattering of neutrons on carbon-12 (12C), is Although the structure of the 12C nucleus is unchanged, the neutron changes direction and speed, and the 12C nucleus recoils. The total kinetic energy of 1 See Section A.2.4 of Appendix A for the definition of the electron volt (eV) and the related terms keV (equal to 103 eV) and MeV (equal to 106...

References

Klaus Becker, Book Review of NCRP Report 136, Health Physics 82, no. 2, 2002 257-258. 2. United Nations Scientific Committee on the Effects of Atomic Radiation, Sources and Effects of Ionizing Radiation, Volume I Sources, UNSCEAR 2000 Report (New York United Nations, 2000). 3. United Nations Scientific Committee on the Effects of Atomic Radiation, Sources and Effects of Ionizing Radiation, Volume II Effects, UNSCEAR 2000 Report, (New York United Nations, 2000). 4. National Council on Radiation...

Neptunium

The difficulties in accurately establishing the dose caused by the ingestion of radionuclides is illustrated by the case of 237Np.29 It is an extreme case because the changes over time in the assessment of 237Np hazards have been exceptionally large. It is of particular interest because in current calculations for the Yucca Mountain nuclear waste repository, 237Np is the largest contributor to the potential radiation dose after 100,000 years. The dose from the ingestion of a given amount of a...

Effects of Radon Exposure in the General Population

The discrepancy discussed in the previous subsection is of lesser immediate importance than the disagreement between the results of two approaches to relating lung cancer rates in the general population to residential radon concentrations. One method for studying the relationship is through case-control epidemiological studies. A case group, composed of people who have been diagnosed as having lung cancer, is compared to a control group of randomly selected people from the same general area....

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...

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...

Genetic Effects

There is no evidence that directly demonstrates genetic damage to the offspring of people exposed to radiation, although in the 1950s and earlier, there was considerable emphasis on the potential genetic effects of radiation, based on animal studies. Since then, in the words of NCRP Report No. 116 the genetic risks were found to be smaller and cancer risks larger than were thought at the time 6, p. 12 . A 2001 UNSCEAR Report summarizes the current evidence as follows No radiation-induced...

Hormesis and Adaptive Response

The simplest criticism of the LNT hypothesis is that it has not been proven, namely, that there is little evidence from studies of exposed populations that directly demonstrates that low doses of radiation cause cancer. In fact, the converse has also been argued that there are reasons to believe that low doses of radiation do not cause cancer. One argument that is advanced in support of this thesis is based on the existence of biological mechanisms to repair the cellular damage that occurs at...

Difficulties in Obtaining Observational Evidence of Low Dose Effects

In general, there are major difficulties in trying to identify a small number of radiation-induced cancers in the presence of the background of many natural cancers. One difficulty is statistical, especially if the data are subdivided to study cancers for particular age groups or in a particular organ. For example, if a population is divided into 6 age groups and one separately considers 5 cancer types and both genders, there are a total of 60 categories. On average, there should be three cases...

Nuclear Industry Workers

A comprehensive study of cancer mortality workers in the nuclear industry analyzed aggregated data from seven laboratories three in the United States, three in the United Kingdom, and one in Canada 20 . Among the 95,673 workers included, there were 15,825 deaths of which 3976 were from cancer. The population was subdivided by dose and an expected number of deaths was calculated for each group, based on its size, with adjustments for factors such as gender and age. Most of the workers (60 ) had...

Observational Evidence for Cancer at Low Dose Rates Range of Studies

The atomic bomb survivor data, while the best available for the effects of radiation at high doses and high dose rates, become ambiguous for doses below 50 or 100 mSv, and may not be applicable to doses delivered over a protracted period of time. For that reason, there have been extensive studies of the cancer rates in populations other than the atomic bomb survivors that have been exposed to radiation at above-average rates. These include populations living in regions of elevated levels of...

Effects of Low Radiation Doses Importance of Low Doses

From a policy standpoint, it is unfortunate that the available information on the effects of low doses is as inadequate as it is. Virtually all of our direct evidence on the harmful stochastic effects of radiation, for studies in both animals and humans, comes from observations at high doses or high dose rates, most notably the Hiroshima-Nagasaki studies. However, most of the exposures of concern, such as those from nuclear weapon tests, nuclear energy, and indoor radon, involve much lower...

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...

Types of Effects Deterministic and Stochastic

In radiation studies, a distinction is made between deterministic and stochastic effects.4 Deterministic effects depend on the killing of many cells over a relatively short period of time. They are induced by intense exposures, and the outcome of this exposure is reasonably well defined. The magnitude of the dose determines the intensity of the effect. The most obvious deterministic outcome is the death of the victim within a short time (a few months, or less) after the exposure. Stochastic...

Agencies and Groups Carrying out Radiation Studies

In recognition of the importance of determining the dangers that ionizing radiation may pose for humans, the health consequences of radiation exposures have been studied almost since the first discovery of X-rays and radioactivity. The studies greatly intensified during and after World War II, with contributions from many individuals and groups throughout the world. Official advice as to radiation protection is provided internationally by the International Commission on Radiological Protection...

Nuclear Fuel Cycle

The civilian nuclear power fuel cycle, involving mining, fuel fabrication, and reactor operation, contributes a negligible dose to the general public. If calculated on the basis of 1980s practices, as in the NCRP estimate in Table 3.5, it averages about 0.0005 mSv yr for the United States.29 The world average for the 1990s reported in Table 3.5 is even lower. The largest contributions to the dose are from uranium mining and processing operations, including the 27 The United States, USSR, and...

Other Sources of Radiation Consumer Products

A variety of other human activities involve radiation exposures. One broad group is listed in Table 3.5 as consumer products. These are considered by the NCRP but not included in the UNSCEAR compilation. Sources of exposure in this category most notably include natural radionuclides in the water supply and in building materials 3, p. 31 . Another large but uncertain source of exposure is tobacco. Tobacco leaves collect lead-210 (210Pb) from the air and this radionuclide and its immediate decay...

Survey of Radiation Exposures Natural Sources of Radiation Overview

Average radiation exposures resulting from natural sources are far greater than those that result from human technology (especially if one omits medical exposures), although the latter usually attract greater attention. The important natural sources include inhaled radon and its progeny, radionuclides in the Earth's crust, radionuclides in the body, and cosmic rays. The resulting doses are summarized in Table 3.5, in terms of averages for the United States and the world.18 The two sets of...

Concentrations of Radionuclides in the Environment Radionuclides in the Earths Crust

There are substantial variations in the concentrations of chemical elements and, hence, of radionuclides in different parts of the Earth's crust. For example, for the crust as a whole, the uranium abundance by mass is about 3 parts per million (ppm) (i.e., 0.0003 ), with common rocks having ura nium concentrations ranging from 0.5 to 5 ppm 14, p. 61 . Concentrations in uranium ores commonly exceed several hundred ppm, and there are deposits that are reported to have concentrations as high as 65...

Status of Reprocessing Programs

Until the late 1970s, reprocessing had been planned as part of the U.S. nuclear power program. A reprocessing facility at West Valley, New York was in operation from 1966 to 1972, with a capacity of 300 MTHM yr. This is enough, roughly speaking, for the output of 10 large reactors. There were plans for further facilities at Morris (Illinois) and Barnwell (South Carolina) which would have substantially increased the reprocessing capacity. However, all these plans have been abandoned.27 In part,...

Energy per Unit Mass of Fuel

The discussion in the preceding subsection is incomplete, because it omits many crucial factors that significantly modify the amount of 235 U required by a reactor. These include the following 1. Not all of the 235U is consumed in the reactor. For example, for the case described in Table 9.2, the 235U content per MTHM is 37.5 kg in the fresh fuel and 8.6 kg in the spent fuel (i.e., a consumption of only 77 of the 235U). 2. About 14 of the thermal neutron-absorption reactions in 235U result in...

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...

Separative Work

In a 235U enrichment process, there are three streams of material the input or feed, the output or product, and the residue or tails. The system operates with a cascade of steps, with the enrichment of the product increasing successively in each step.17 As the enrichment cascade progresses, the tails from an intermediate stage have a higher 235U concentration than the original feed material, and these tails can profitably be returned to the cascade. There are different strategies for reusing...

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...

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...

Degrees of Enrichment

Natural uranium has an isotopic abundance by number of atoms of 0.0055 234U, 0.720 235U and 99.275 238U.9 In the remainder of the discussion of uranium isotopic enrichment, we will follow the standard practice of describing the 235U fraction in terms of 'mass rather than, as is common in many other scientific applications, of number of atoms.10 For natural uranium, the 235U abundance by mass is 0.711 . The presence of the small amount of 234U is often ignored, because corrections on the order...

Radon Exposures from Uranium Mining and Mill Tailings

In the early days of uranium mining, little attention was paid to radiation safety. In the Middle Ages, long before uranium had been identified as an element, metal miners in southern Germany and Czechoslovakia contracted lung ailments, called Bergkrankheit (mountain sickness). Modern scientists have attributed the ailment to lung cancer caused by a high uranium concentration 4 U3O8 is not yellow in its pure form. Yellowcake is about 85 U3O8 5, p. 241 , and the yellow color results from another...

Front End of the Fuel Cycle Uranium Mining and Milling Uranium Deposits in the Earths Crust

The concentration of uranium varies greatly among geological formations. The average concentration in the Earth's crust is about 3 parts per million (ppm) by weight, but extremes extend from under 1 ppm to something in the neighborhood of 500,000 ppm.3 Uranium resources are widely distributed, with substantial uranium production in many countries, including Australia, Canada, Kazakhstan, Namibia, 3 For example, one deposit in Canada is identified as having zones of over 50 U3O8, which...

Characteristics of the Nuclear Fuel Cycle Types of Fuel Cycle

The nuclear fuel cycle is the progression of steps in the utilization of fissile materials, from the initial mining of the uranium (or thorium) through the final disposition of the material removed from the reactor. It is called a cycle because in the general case, some of the material taken from a reactor may be used again, or recycled. Fuel cycles differ in the nature of the fuel used, the fuel's history in the reactor, and the manner of handling the fuel that is removed from the reactor at...

High Conversion Ratios Without Breeding

Before turning to fast breeder reactors, it may be noted that even if breeding is not achieved with thermal reactors, a high conversion ratio can still be desirable. One motivation could be plutonium production. Another motivation is the extension of fuel resources. As the conversion ratio increases, the energy output increases for a given original 235U content. A high conversion ratio means a high ratio of capture in 238U to absorption in 235U. This must be accomplished without losing...

Components of a Light Water Reactor

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...

History of Commercial Reactor Development

After World War II, the leading countries in nuclear reactor development were the United States, the United Kingdom, Canada, and the Soviet Union. Each went in a different direction. The first U.S. power reactors, beyond plutonium-producing or experimental reactors, were built for submarines, not for civilian electricity generation. The earliest were a PWR for the submarine Nautilus, commissioned in 1955, and a sodium-cooled reactor for the submarine Seawolf. The Seawolf reactor had...

Types of Reactors

A variety of different reactors are in use in the world today, although there was greater diversity in the early days of reactor design. Table 8.1 lists the types of nuclear power plant in operation in late 2003 as well as those reported to be under construction or on order 10 . The dominant reactor is the light water reactor (LWR), which uses ordinary water as both the coolant and moderator and enriched uranium in UO2 pellets as the fuel. There are two types of light water reactor the...

Nuclear Weapon Tests

Extensive aboveground nuclear weapons tests were carried out by the United States, the Soviet Union, and other countries, particularly in the period from 1952 to 1962.27 The resulting worldwide average effective dose peaked at 0.11 mSv yr in 1963 and dropped to 0.0055 mSv yr by 1999 7, pp. 228-230 . The average cumulative dose from 1945 to 1999 (i.e., the sum of the annual average doses over the 55-year period) was 1.1 mSv in the northern hemisphere, 0.3 mSv in the southern hemisphere, and 1.0...

Components of Conventional Reactors Overall

Any generating plant consists of an array of structural components and a system of mechanical and electrical controls. In a nuclear plant, there are special demands on structural integrity and reliability. In addition, a nuclear reactor is characterized by the use of specialized materials, some aspects of which were already discussed in Chapter 7. In standard reactors, these are the fuel itself, the coolant, the moderator, and neutron-absorbing materials used to control the power level. A main...

Inventories of US Nuclear Wastes

Inventories of U.S. commercial and military wastes are summarized in Table 10.1. They include the wastes that are planned for the Yucca Mountain repository as well as further amounts expected to be produced. The commercial wastes constitute 90 of the total slated for Yucca Mountain, measured in terms of the mass of the initial uranium used to generate the wastes (in MTHM). In general, they are the hottest wastes, so they contain more than 90 of the total activity 3, p. A-9 . When the...

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...

Military and Civilian Wastes

As discussed in Chapter 2, the first nuclear reactors were those built during World War II to produce plutonium for weapons. In order to extract the plutonium, it is necessary to reprocess the spent fuel, first converting it to liquid form. The residue remaining after the plutonium and uranium (and sometimes other elements) are extracted constitutes the reprocessed wastes. Reprocessing increases the volume of the residue and puts it in a form that can more readily escape into the environment....

Categories of Nuclear Waste The Nature of the Problem

The term nuclear waste embraces all residues from the use of radioactive materials, including uses in medicine and industry. The most highly radioactive of these are the spent fuel or reprocessed wastes from commercial nuclear reactors and reactors that produced plutonium for nuclear weapons. The other wastes have much lower levels of activity and have far less potential to cause harm, although the establishment of sites for the disposal of these wastes has encountered public opposition in many...

Impact of Fuel Cycle Changes and Breeder Reactors

The question of changes in the fuel cycle and particularly the question of breeder reactors is closely connected to the issue of resources. For the most part, we have assumed a once-through fuel cycle using uranium. If, instead, a comprehensive reprocessing plan is implemented, such as the full actinide recycle option discussed in Section 9.4.3, the situation would be somewhat relieved. In this cycle, the uranium required for a given electricity output is roughly halved, which effectively...

Estimates of Uranium Resources Classification of Resources

An extensive description of the world uranium industry is provided by the Red Book series, published by the OECD since the 1960s under the title Uranium Resources, Production and Demand (see, e.g., Ref. 4 ). It is common to classify resources in terms of the degree of knowledge of the location and extent of identified or expected uranium deposits. So-called conventional resources are divided in the Red Book into four groups reasonably assured, estimated additional (in two categories of...

Waste Disposal

All countries with announced plans for disposing of high-level radioactive wastes are planning on eventual disposal in deep geologic repositories, typically made by excavating caverns or holes in favorable environments. Many of the plans for these permanent disposal facilities include a period during which the waste could still be retrieved. Deep geologic disposal has been the favored course in U.S. thinking since the first attempts to formulate plans. There have been continuing efforts to...

Alternative Reprocessing and Fuel Cycle Candidates Advanced Aqueous Process

In the widely used PUREX process, the plutonium and uranium are extracted and the fission products and minor actinides constitute the wastes. The advanced aqueous process is a modification of the PUREX process in which the minor actinides are recovered as well. Uranium is crystallized out at an early stage to reduce the bulk of the material that must be dealt with in the further chemical processing 44, p. 60 . The two product streams, one of uranium and the other of plutonium and the minor...

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...

Units in Atomic and Nuclear Physics A Electric Charge

In the International System of Units (SI), the unit of charge is the Coulomb, itself defined in terms of the unit of current, the ampere. In atomic and nuclear physics, it is usually more convenient to express charge in terms of the magnitude of the charge of the electron, e, where1 The charge of the electron is e, and the charge of the proton is +e. The atomic number of carbon is 6, and therefore the charge on the carbon nucleus is 6e, or 9.61 x 10 19 Coulombs.

Isotopes and Isobars

For a given element (i.e., same Z), nuclei with different numbers of neutrons (i.e., different A) are called isotopes of the element. Nuclei with the same mass number A but different atomic number Z are called isobars. Different isotopes of an element are virtually identical in chemical properties (although small differences may arise from their different masses and therefore their different mobilities). In nature, the relative abundances of different isotopes are usually closely the same for...

Simple Atomic Model A Atoms and Their Constituents

Before 1940 scientists had identified 92 elements. These were commonly arranged in the classical periodic table, which organized the elements into groups with similar chemical properties. The last element in this table was uranium, and for many years it seemed as if this table provided a full representation of matter. Then, with new facilities and insights, attempts were made to produce elements beyond uranium, the so-called transuranic elements. These efforts eventually proved successful,...

Differences Among Countries

Although all countries are impacted by some of the same economic factors and resource pressures, it is not to be expected that they will all reach the same decisions. The differences in the nuclear policies of different countries can arise from basic aspects of their physical environment or from the political and economic character of their societies. In terms of its environment, Japan is in a particularly difficult situation. It is poor in fossil fuel resources and it has a population density...

The Road to Decisions One Path or Many

A variety of solutions to the world's energy problems are on the table, and each has its enthusiasts and detractors. In the background, and complementing all of the solutions, is conservation. Reduction of wasteful or inefficient uses of energy can substantially reduce the demand for energy. However, at any plausible degree of conservation, world energy consumption will rise and even without a rise in consumption, replacing present fossil fuel use is desirable. The options for the required...

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...

Proliferation Risks and Nuclear Power

Some of the detailed issues bearing on the connection between nuclear power and proliferation of nuclear weapons have been discussed in Chapter 18 and earlier in this chapter. Two contrasting assessments can be made as to the nature of this connection. In one view, any country with nuclear power has a headstart as a potential proliferator. Whether or not it has nuclear weapons at the moment, possession of nuclear power makes its path to nuclear weapons easier in terms of both professional...

Institutional Issues

Some observers, including most advocates of nuclear power, believe that the crucial issues in the United States are more institutional than technical or even economic. The division of authority and initiative among many levels of government has made it difficult to adopt and implement policies that would permit rapid development of nuclear power (or even its prompt curtailment). Important roles are played by the president, Congress, the courts, and a host of federal agencies, including the...

Projections for Future Growth

The long-standing uncertainty about the future of nuclear power in the United States is illustrated by alternative DOE projections made in 1993 for the growth of nuclear power up to the year 2030 38, p. 9 . Three scenarios from these projections are presented in Figure 20.1 (1) a no new orders scenario, in which nuclear capacity decreases as existing reactors are phased out (2) a lower reference case in which there is a cautious resumption of nuclear expansion and (3) an upper reference case...

Weapons Proliferation

The most serious objection to nuclear power, in the view of many technical people, is its link to the spread of nuclear weapons, either to additional countries or to terrorists, as was discussed at some length in Section 18.3. A large worldwide expansion could increase proliferation risks, because the greater the number of countries with nuclear power, the greater the number of actual or latent proliferators (see, e.g, Ref. 19 ). For example, more countries could assert the need for...

Nuclear Wastes

The nuclear waste problem can be considered in the context of the U.S. experience. The Yucca Mountain repository has a planned capacity of 70,000 metric tons of heavy metal (MTHM). Typical spent fuel output is now about 30 MTHM GWyr. The contemplated expansion to an annual 325 GWyr would mean, were there no changes in reactor performance, a U.S. spent fuel output of about 10,000 MTHM per year. Thus, one Yucca Mountain scale repository would be needed every 7 years. However, future reactors may...

Uranium Resources

An immediate concern in contemplating such an expansion is the uranium supply. World uranium resources were estimated in Section 9.5.2 to be about 20 million tonnes, enough for 100,000 GWyr of reactor operation for present reactors. This would suffice to sustain a linear buildup to 2700 GWyr in 2050 and roughly another 15 years of continued operation. However, it would make little sense to bring reactors on line in 2050 that would run out of fuel in 2065. The hypothesized expansion could be...

Possible Difficulties in Nuclear Expansion The Pace of Reactor Construction

An expansion to 3000 GWe of nuclear capacity in 2050 may seem a very ambitious goal, especially when at present there is little reactor construction in the world. For a future world population of 9 billion people, the hypothesized per capita nuclear output would correspond to about 40 that of France in 2000. Most of the French increase in nuclear generation occurred in a 20-year period starting in about 1977. It should be possible for the world to achieve less than one-half the present French...

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...

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...

Production of Hydrogen Methods of Hydrogen Production

Hydrogen is sometimes referred to as the energy source of the future. This is a misnomer, or at least misleading. Hydrogen is not a fundamental energy source, in that there is very little hydrogen on Earth in a pure elemental form. Most of the hydrogen is trapped in water (H2O) or in hydrocarbons, and energy must be provided to produce it in elemental form. Once produced, hydrogen has the advantage of having a very high heat of combustion per unit mass 142 megajoules per kilogram (MJ kg) for...

Possible Additional Applications

The preceding discussions have mentioned the possible expanded use of nuclear energy in two important applications, namely the production of hydrogen and the desalinization of seawater. Each addresses limitations in the availability of a key resource. Hydrogen is a potential substitute for oil in transportation and desalinization offers a remedy for regional scarcities of water. They are discussed in the immediately following subsections. In each application, depending upon the method used, the...

Demand for Nuclear Power

Given the uncertainties in the world demand for electricity and the even greater uncertainties in the future acceptance of nuclear power, any estimate of nuclear power use in 2050 is highly speculative. However, we consider here several estimates for 2050 that suggest the possible scale of nuclear capacity and generation if there is to be a large expansion of nuclear power In the highest of the WEC IIASA projections discussed earlier, annual electricity generation in 2050 was projected to be...

Wind Power

Wind is a rapidly growing source of electricity in some countries, particularly in Denmark, and the available resource is large. For the OECD as a whole, wind energy output rose from 0.5 GWyr in 1992 to 3.9 GWyr in 2001, an average rate of increase of 25 per year 1 . Some studies indicate that the wind resources in the United States are adequate to produce more electricity than is generated today from all sources.5 However, wind still makes only a very small contribution in most of the world...

Hydroelectric Power

Hydroelectric power is the most important renewable energy source, and it dominates the renewable contribution to electric power generation. It has played an important role in many countries, including the United States, where in the past it accounted for a large share of all electricity generation (e.g., 32 in 1949 12 ). Some major new hydroelectric dams are still being developed, notably China's project on the Yangtze River, which is expected to provide an annual output of about 10 GWyr....

Direct Use of Solar Energy

All direct uses of solar energy for electricity generation suffer from the dilute nature of the solar source. The average flux of solar energy at the surface of the Earth is about 200 W m2. Thus, it requires about 5 km2 to collect 1 GW of incident solar energy. The area required for electricity generation depends on the efficiency of conversion from solar energy to electricity. One potential source of electricity is biomass, used as a fuel in a steam turbine plant. The main source of biomass...

Renewable Sources Overview of Renewable Sources

In principle, renewable energy sources offer an alternative that avoids the CO2 produced by fossil fuels and the radionuclides produced by nuclear power. The terms renewable energy and solar energy are sometimes used interchangeably, but renewable energy includes the nonsolar sources of tidal and geother-mal power. Tidal power ultimately is based on gravitational forces, with the tides arising from the motions of the Earth and Moon. Geothermal power is ultimately derived from the decay of...

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...

The Nuclear Debate Nature of the Debate

Debates about nuclear energy have sometimes appeared to have the aspect of a religious war, especially in the 1970s and 1980s when an expanding nuclear enterprise came into conflict with a growing antinuclear movement. Nuclear energy was discussed as if it were intrinsically good or evil, and for many of the protagonists, it became instinctive to oppose or support it. That debate has since become more muted. This does not mean that the basic issues are settled. Rather, it means that less...

Reactor Longevity

A private reactor operator whether a utility or an independent power producer has a responsibility to provide an adequate return to the investors within a reasonable period of time. The amortization period for nuclear power plants is typically 40 years. However, prospective investors today have a shorter time horizon. A discount rate of 12 , as adopted in the NTDG Roadmap, reflects the need to compensate investors relatively quickly. For a 40-year stream of payments at this rate, 90 of the...

Tax Credits

Renewable energy has received benefits in the form of tax credits, beginning with credits established by the federal government and California in the 1970s. These lapsed, but the federal Energy Policy Act of 1992 instituted an inflation-adjusted tax credit that started at 1.5 kWh and has risen, with inflation, to 1.8 kWh in 2003 15, p. 20 . It favors wind power and some biomass producers (see also Section 19.2.2). These credits have been extended on an annual basis since their original...

Nuclear Powers Need for Federal Support

Given present conditions, it appears unlikely that a new nuclear power plant will be built in the United States in the near future without federal action 16 Net imports represented 53 of petroleum supply in 2002 14, Table 1.7 . to reduce some of the financial risks of such a project. Even if nuclear power had, say, a 1 kWh cost advantage over the main competing source most likely natural gas that might not be enough to encourage a reactor order. The strength of public and government opposition...

Costs and Electricity Choices The Role of Cost Differences

The estimated generation costs for the four main options considered in Table 19.1 are mostly between about 4 kWh and 5 kWh. The MIT estimates overlap this range, although the base nuclear estimate is higher. Overall, the differences among the sources are probably less than the uncertainties in the estimates for each source and are small compared to the variations in the average U.S. cost of electric power over the past several decades and to regional variations (see Section 19.3.4)....

Comparative Cost Estimates

Several estimates of future electricity costs are presented in Table 19.1 for new U.S. plants going into operation in 2010.14 Costs projected by the U.S. DOE's Energy Information Administration are given for advanced coal, advanced gas, nuclear, and wind generation. For nuclear plants, two estimates are made, a reference case and an advanced cost case which assumes that the construction costs are reduced in a manner consistent with goals endorsed by the DOE's Office of Nuclear Energy 15, p. 71...

Major Factors Impacting Costs of Gas Coal and Nuclear Electricity

The major question mark surrounding the attractiveness of natural gas for electricity generation is that of natural gas prices. The prices have been quite volatile in the past, and we may face both volatility and a long-term increasing trend if there is increasing natural gas use for electricity generation and other applications. Figure 19.2 displays simulated fuel costs in constant 1996 dollars for coal and natural gas at the prices prevailing from 1973 to 2001, assuming thermal efficiencies...

Costs of Nuclear and Fossil Fuel Electricity Sources Recent Trends in Comparative Costs

For nuclear power to be of interest to commercial companies in a competitive electricity market, its generation costs must be as low as those of coal or natural gas. In the past, the main cost competition has been between nuclear power and coal. From 1975 to 1982, the generation costs of nuclear- and coal-powered plants were about the same, but from 1982 to the late 1980s, nuclear costs rose rapidly while coal costs decreased slightly, both measured in current dollars.11 The rise in nuclear...

Recent Trends in Electricity Prices

The history of electricity prices in the United States since 1960 is shown in Figure 19.1, which gives average prices expressed in both current (or nominal) dollars and constant (or real) 1996 dollars 9, p. 241 . Although the price Fig. 19.1. Average U.S. retail electricity prices, 1960-2001, expressed in current dollars and in constant 1996 dollars. (From Ref. 9, Table 8.6 . Fig. 19.1. Average U.S. retail electricity prices, 1960-2001, expressed in current dollars and in constant 1996 dollars....

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...