The Linearity Hypothesis

According to the linearity hypothesis, the cancer risk (above the normal rate) is proportional to the magnitude of the excess radiation dose, over the full range from zero dose to high dose, independent of the dose rate.14 Thus, if a dose of 1 Sv in a brief period corresponds to a 10 risk of a radiation-induced cancer, then a dose of 1 mSv (gradual or sudden) corresponds to a 0.01 chance. More generally, each increase of 1 mSv in dose would add 0.01 to the cancer risk. Sometimes, to be...

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,...

Extraction of Plutonium and Uranium

The alternative to disposing of the spent fuel is to reprocess it and extract at least the uranium and plutonium. In reprocessing, the spent fuel is dissolved in acid and the plutonium and uranium are chemically extracted into separate streams, for use in new fuel. The most widely used method for this is the suggestively named PUREX process. Most early U.S. plans for reprocessing assumed that 99.5 of the U and Pu would be removed. The remainder constitutes the high-level waste. In the...

Disposal or Storage of Spent Fuel

For many years, it had been assumed that all U.S. civilian nuclear waste would be reprocessed, but U.S. reprocessing plans have been abandoned. Instead, 25 An annual refueling shutdown of 2 months would mean a maximum capacity factor of 83 , which is well below the present U.S. average. official plans now call for disposing of the spent fuel directly, while retaining for many decades the option of retrieving it. The fuel is to remain in solid form and the fuel assemblies eventually placed in...

Back End of Fuel Cycle Handling of Spent Fuel Initial Handling of Reactor Fuel

Periodically, a portion of the fuel in the reactor is removed and replaced by fresh fuel. In typical past practice, an average sample of fuel remained in the reactor for 3 years, and approximately one-third of the fuel was removed each year, with a shutdown time for refueling and maintenance of up to about 2 months. The trend is now to extend the interval between refueling operations and to reduce the time for refueling.25 Currently, time intervals of 18 months and shutdowns of 1 month are...

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...

Burnup as a Measure of Fuel Utilization Thermal Efficiency of US Reactors

The thermal efficiency of a reactor is the ratio of the electrical energy produced to the total heat energy produced. Since 1973, the average thermal efficiency of U.S. reactors has ranged between 30.6 and 32.1 , according to DOE compilations 23, Table A6 . There has been a gradual improvement with time, and since 1985 it has been above 31.5 , reaching 32.1 for the years 1996-2002. We will use the approximate figure of 32 as the nominal average efficiency of LWRs. 19 For a discussion of the...

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...

Steps in the Nuclear Fuel Cycle

A schematic picture of the fuel cycle is shown in Figure 9.1, which indicates alternative paths, with and without reprocessing 2 . The steps in the fuel cycle that precede the introduction of the fuel into the reactor are referred to as the front end of the fuel cycle. Those that follow the removal of the fuel from the reactor comprise the back end of the fuel cycle. At present, there is only a truncated back end to the fuel cycle in the United States, as virtually all commercial spent fuel is...

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...

The Natural Reactor at Oklo

A remarkable discovery was made in 1972 by French scientists analyzing uranium extracted from the Oklo uranium mine in Gabon. The uranium was depleted in 235U, sometimes by large amounts, although, normally, the isotope ratios in uranium are nearly constant over the surface of the Earth. It was soon suspected and then demonstrated that this isotopic anomaly was due to a natural uranium chain reaction occurring more than a billion years ago. Conclusive evidence in support of this explanation was...

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...

Potential of U for a Thermal Breeder Reactor

The number of neutrons produced is significantly higher for 233U (no 2.296) than for 235U, and there have been serious suggestions for developing 233U thermal breeders. These date to as early as 1945, in work done by Eugene Wigner's group in Chicago 3, Chapter 6 . A cycle is envisaged in which 233U is produced initially in a reactor with 235U as the fissile fuel and 232Th as the fertile fuel. Subsequently, a 233U-232Th cycle could, in principle, be self-sustaining. Not only is no higher for...

Difficulty of Reaching a Conversion Ratio of Unity with U

As discussed in Section 7.4, the limiting condition for a breeder reactor is that the conversion ratio, C, be at least 1. This means that the number no of neutrons produced for each neutron absorbed in 235U, must be two or more.15 For thermal neutrons absorbed in 235U, no 2.075 (see Table 7.1). Were there no losses, this would suffice for breeding 1 neutron for continuing the 14 Sometimes, a distinction is made in terminology, with conversion ratio used when C < 1 and breeding ratio used when...

Characterization of Reactors

As discussed in Section 7.1.1, the condition for a chain reaction is that for every neutron initiating fission in one generation, one or more neutrons initiate fission in the next generation. If, in addition, another fissile nucleus is produced for every 235U atom consumed, then there is no decrease in the amount of nuclear fuel available. This is the principle of the breeder reactor. The conversion ratio C (or breeding ratio B) is defined as the ratio of the rate of production of fissile...

PWR Reactor Cores

We consider here the specific characteristics of a reactor core based on a Westinghouse Corporation PWR design, but the gross features are similar for all large LWRs.13 The reactor fuel is in the form of cylindrical uranium oxide (UO2) pellets, about 0.8 cm in diameter and 1.35 cm in length. The pellets are placed in tubes called fuel rods or fuel pins made of zircaloy, a zirconium alloy (98 Zr, 1.5 Sn, and small amounts of other metals 16, p. 234 ) selected on the basis of structural strength...

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...

PWRs and BWRs

The two types of LWR in use in the world are the pressurized water reactor (PWR) and the boiling water reactor (BWR). The difference between them, as embodied in the names, is in the condition of the water used as coolant and moderator. In the PWR, the water in the reactor vessel is maintained in liquid form by high pressure. Steam to drive the turbine is developed in a separate steam generator. In the BWR, steam is provided directly from the reactor. These differences are brought out in 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...

World Inventory of Reactor Types Reactor Sizes

The earliest reactors had generating capacities well below 100 MWe, but there was a rapid transition to 1000-MWe reactors and larger. The move to a larger size was motivated by the desire to capture economies of scale. Some analysts suggest that this escalation proceeded too rapidly, especially in the United States, and was responsible for some of the difficulties encountered in achieving short construction times and reliable operation. The mean capacity of all reactors in operation worldwide...

Control Materials

As discussed in Section 7.5.2, control materials are needed to regulate reactor operation and provide a means for rapid shutdown. Boron and cadmium are particularly good control materials because of their high cross sections for the absorption of thermal neutrons. These control materials are usually used in the form of rods. Control rods for pressurized water reactors (PWRs) commonly use boron in the form of boron carbide (B4C) or cadmium in a silver-indium alloy containing 5 cadmium. Control...

Coolants

The main function of the coolant in an electricity generating plant is to transfer energy from the hot fuel to the electrical turbine, either directly or through intermediate steps. During power plant operation, cooling is an intrinsic aspect of energy transfer. However, in a nuclear reactor, cooling has a special additional importance, because radioactive decay causes heat production to continue even after the reactor is shut down and electricity generation has stopped. It is still essential...

Moderators

As discussed in Section 7.2, a moderator is required if the reactor is to operate at thermal neutron energies. This means that most operating reactors use moderators, with the fast breeder reactor the exception. The options for moderating materials are limited Hydrogen (Z 1 . The isotopes 1H and 2H are widely used as moderators, in the form of light (ordinary) water and heavy water, respectively. 4 In particular, this fuel is for high-temperature gas-cooled reactors (see Section 16.4.3). Helium...

Fuels

There are few nuclides that can be used as reactor fuels. The paucity of possible candidates can be seen by examining the properties of the naturally occurring heavy elements 2 The fast breeder reactor program was subsequently sharply reduced, with the centerpiece of the U.S. fast breeder reactor program, the Clinch River Breeder Reactor, abandoned in 1975. 3 There has been speculation about a quite different sort of molten-salt reactor, driven by a proton accelerator. If pursued, this would...

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...

Western Hemisphere Other Than the United States

Canada embarked on a large program of nuclear construction, mostly in the late 1970s, and in 1995 had 22 operating reactors, all based on the CANDU reactors, which have made Canada a leading country in nuclear capacity and generation. However, in the 1990s, 8 of the 22 reactors in Canada were put into a temporary laid-up status, one in 1995 and 7 in late 1997 and early 1998. These eight were the oldest ones in operation, all having started up in the 1970s. This step was taken at the behest of...

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...

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...

Uranium from Seawater

Uranium from seawater represents a very large potential additional resource, but at a cost that may be considerably higher than that of any uranium resource considered earlier. The volume of seawater in the oceans is about 1.4 x 1021 L, with an average uranium concentration of 3.2 parts per billion (see Section 3.4.3), corresponding to 4 billion tonnes of uranium. However, the energy content is very dilute, and vast amounts of water would have to be processed to extract uranium. The cost of...

Adequacy of Terrestrial Uranium Resources

Adopting the probably conservative resource estimate of 20 million tonnes, uranium resources would suffice for the needs of LWRs for about 100,000 GWyr at a rate of 200 tonnes of U per gigawatt-year. Present world generation from nuclear power is roughly 300 GWyr yr. Thus, a resource of this magnitude could sustain four times the present rate of generation for 80 years. Such an increase does not appear to be imminent and, therefore, there is little pressure on uranium resources at this time....

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...

Uranium Prices and Electricity Costs

Uranium prices are now very low compared to those projected several decades ago. They dropped markedly in recent years, in large measure due to the lag in the expansion of nuclear power. U.S. prices peaked in 1978 at an average of 43 lb of U3O8 47 . In 2001, the average price paid by U.S. utilities was 10 lb U3O8 ( 26 kg U) 17, p. 11 . The relationship between uranium price and the contribution of uranium fuel costs to electricity costs depends on the effectiveness of fuel utilization. As was...

Conventional Units for Amounts of Uranium

The magnitude of uranium resources can be specified in terms of the amount of uranium oxide (U3O8) or the amount of natural uranium (U). Commonly, U.S. organizations expressed the resources in short tons of U3O8, whereas international organizations, such as the OECD, use tonnes of uranium. The units are related by the equivalence 30 In terms of the units in which uranium prices are usually couched, 1 kg of U is equivalent to 2.60 lbs of U3O8 therefore, a price of 100 lb of U3O8 is equivalent to...

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...

General Features of Reprocessing Options

Any fuel cycle that recycles the fissile components of the spent fuel (mainly the remaining 235U and the plutonium isotopes 239Pu and 241 Pu), increases the energy obtained from the existing uranium resources. If the minor actinides are included with the uranium and plutonium in the new fuel, the wastes will have much less long-term radioactivity than wastes in the once-through fuel cycle. The mass of the spent fuel is greatly reduced if the uranium is either returned to the reactor or is...

Pyroprocessing

The above-discussed chemical reprocessing processes are known as aqueous processes. An alternative approach, under active exploration for use in conjunction with future reactors, is the pyroprocess or electrorefining process. In this method, the spent fuel is dissolved at very high temperatures in molten cadmium, creating an electrolytic bath. Groups of chemical elements are separately extracted on the basis of differences in the potentials at which they dissolve and ionize. In particular, ions...

The UREX Process

An alternative to the advanced aqueous process is the uranium extraction process (UREX and UREX+). It differs in the means of separating out the uranium. Several output streams are specifically identified in this process 45, p. II-3 1. Uranium. The uranium is extracted in very pure form (at purity levels of 99.999 percent). The leaves it free of highly radioactive contaminants and makes it easy to handle for disposal or reuse in a reactor. 2. Plutonium and minor actinides. Neptunium, americium,...

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...

Isotopes and Elements

It is necessary to keep in mind the distinction between the atomic mass ME of the element, as it occurs with its natural mixture of isotopes, and the mass Mi of any particular isotope. The atomic mass of an element is given by where fi is the fractional abundance of the isotope, by number of atoms. For example, carbon has two stable isotopes 12C and 13C, with atomic masses Mi 4 In this expression, although A is ordinarily defined as a dimensionless integer, we attach to it the same units as the...

Atomic Masses and Energy Release A Atomic Mass and Atomic Mass Number

In describing a nuclear species for example, 238U one could specify either the mass of the nucleus or the mass of the atom (the nucleus plus the electrons). It is virtually universal practice to specify atomic mass. The mass M of an atom (expressed in atomic mass units) is not exactly equal to the mass number A of the atom, except for 12 C, where the equality is a matter of definition. However, the numerical difference between M and A is small. This is because the constituents of the atom the...

Mass Energy Equivalence

The equivalence of mass and energy is basic to nuclear and atomic physics considerations. The energy E associated with the mass m is E mc2, where c is the velocity of light. Expressing mass in kilograms and velocity in meters sec, the energy equivalent of 1 atomic mass unit is 2 1 keV 103 eV 1 MeV 106 eV. 3 Coulomb repulsion is the name commonly given to the repulsion, governed by Coulomb's law, between objects that carry charges of the same sign. E (1.66054 x 10-27) x (2.9979 x 108)2 (1.6022 x...

Energy

Energy is expressed in joules (J) in SI units, but it is much more common in atomic and nuclear physics to express energy in electron volts (eV), kilo-electron volts (keV), or mega-electron volts (MeV), where 1 eV is the energy gained by an electron in being accelerated through a potential difference of 1 volt.2 This energy is qAV, with q e and AV 1. Thus, In atomic physics, the convenient unit is usually the eV. In nuclear physics, where the energy transfer per event is much higher, the more...

Avogadros Number and the Mole

It is convenient in chemistry and physics discussions to introduce the gram-molecular weight or mole as a unit for indicating the amount of a substance. For any element or compound, a mole of the substance is the amount for which the mass in grams is numerically equal to the atomic (or molecular) mass of the substance expressed in atomic mass units. For example, the mass of one mole of 12C is exactly 12 g, and the mass of one mole of isotopically pure atomic hydrogen (1H) is 1.0078 g. The...

Mass

The SI unit of mass is the kilogram (kg). It also remains common in atomic and nuclear physics to express mass in grams (g) i.e., in the centimeter-gram-second (cgs) system when mass must be expressed in macroscopic terms. For most purposes in nuclear physics, however, it is more convenient to express mass in terms of the atomic mass unit (u), which is defined so that the mass of a hydrogen atom is close to unity. More precisely, the atomic mass unit is defined in the so-called unified scale by...

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...

Atomic Number and Mass Number

The chemical properties of an element are determined by the number of electrons surrounding the nucleus in an un-ionized atom, which in turn is equal to the number of protons in the nucleus. This number is the element's atomic number, Z. Each element can be identified in terms of its atomic number. Thus, Z atomic number no. of protons in nucleus no. of electrons outside. The natural elements range from hydrogen (Z 1) to uranium (Z 92). Beyond that, the next elements are neptunium (Z 93) and...

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,...

Competing Considerations

In the end, policies on nuclear power will depend on judgments of the relative risks of using it or of trying to do without it. With it, we may face risks of radioactive contamination from reactor accidents or waste disposal. Without it, we may face increased risks from climate change and energy shortages. In both cases, there are risks of nuclear bomb manufacture and use. Conclusions as to the magnitude of these risks and how they balance are likely to vary from country to country, given...

Past Failure of Prediction

It is interesting to look back almost 30 years and examine the prescience of predictions made then. Conveniently for this purpose, a conference was held in Paris in 1975, with the complacent title Nuclear Energy Maturity. The underlying premise of the conference was that nuclear power had arrived, and that it remained to consider how to proceed so that nuclear power could .represent a long-term-solution, that is for thousands of years rather than the few decades set by the uranium supply...

Predictions and their Uncertainty Summary of Factors Impacting Nuclear Power

As discussed earlier, the factors that will determine whether nuclear power moves ahead or regresses include the following The safety record of existing reactors, the progress of the Yucca Mountain repository, and the perceived safety of next-generation reactors. The level of concern about global climate change, oil or natural gas shortages, and the world's dependence on Persian Gulf oil. The perceived prospects of renewable energy, carbon sequestration, and fusion. 26 However, if the federal...

Constituencies For and Against Nuclear Power

In reaching a national decision as to the future of nuclear power, the role of a constituency is important. At present, there is a determined and effective constituency against nuclear power, including most environmental organiza-tions.25 There has been the image of a comparably active and determined constituency for nuclear power, namely the nuclear industry. However, with the decrease of nuclear reactor construction, the nuclear industry has shrunk, and this has not been a valid image for...

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...

Nuclear Power and a Desirable Society Feelings About Material Development

Attitudes toward nuclear power are also influenced by aesthetic or philosophical positions on the nature of a desirable world. Is it better for us (i.e., humans) and the planet to have copious energy supplies or is it preferable for energy limitations to restrain unbridled material development Individual answers to this rather vague question appear to influence the frame of reference in which people view energy issues. We live with a mix of conflicting attitudes toward technology. On the one...

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...

Perceptions of Need

Overhanging all of these considerations is the question of need. Logically or not, the perception of the dangers of nuclear power correlates with the perception of the need for it, including judgments as to the promise of the alternatives. Of course, considerations of danger and need are appropriately linked when a cost-benefit analysis is being made even an informal one. They are not appropriately linked when an estimate is being made of the absolute risk. It is therefore important to guard...

More Intractable Issues

If those were the only sorts of issues involved, the nuclear policy debate would be less difficult, notwithstanding the skepticism with which many people react to the conclusions of expert consensus. However, there are two nontechnical issues that cannot be authoritatively decided but that raise profound questions concerning nuclear power. These are the issues of weapons proliferation and of defining what might be called for want of a better description a desirable society. In the former case,...

Issues in Nuclear Decisions Categories of Issues Resolvable Issues

Contentious as nuclear disagreements are, some of the key issues are basically technical, and, in principle, conscientious people can eventually reach a common understanding. In particular, there are strong disagreements as to the safety of nuclear reactors and nuclear waste disposal, but it is possible to localize the points of disagreement and, with enough study and patience, it should be possible to resolve them. If one chooses to be optimistic, one can look forward to an eventual...

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...

The Decline in US Leadership

The United States was the world pioneer in nuclear energy and, by virtue of the size of its economy, is still the world leader in total nuclear power generation. However, it is not the leader either in the fraction of electricity that comes from nuclear power, or in rate of growth. The U.S. share of world nuclear generation was 50 in 1975 36 but had dropped to 30 by 2002, and U.S. DOE projections suggest that this share will continue to slip 17, p. 186 . Light water reactors of U.S. design...

World Picture

There is no substantial expansion of nuclear power underway at this time outside Asia (see Chapter 2). Many countries in Europe could undertake a program of nuclear reactor construction, but most lack the political impulse. Exceptions include Finland and, if announced plans materialize, Russia. The Finnish program will perforce be small, perhaps restricted to a single reactor, whereas the Russian program potentially could be much larger. The significance of the Finnish reactor will be one of...

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...

Conservation

Conservation, especially in the form of higher efficiency in energy use, can reduce the demand for electricity. It has already contributed importantly through the introduction of more efficient lighting, refrigeration, and motors. Further exploitation of efficient technologies can make major additional contributions. However, conservation measures are already presumed in the scenarios discussed above. For example, the WEC IIASA scenarios assume for the OECD countries improvements in energy...

Possible Expansion of Nuclear Power Projection of Demand Demand for Electricity

In planning for electricity growth, the time horizon is on the scale of decades, and the year 2050 has been selected in some recent publications as a target date for estimates. Such projections, although highly speculative, are useful in suggesting the scale of efforts required to meet future demand. A number of different scenarios were analyzed in a joint study by the World Energy Council (WEC) and the Institute for Applied Systems Analysis (IIASA). The estimates for world electricity...

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...

Fossil Fuels with Low CO Emissions Natural

The combustion of coal in electricity generation was responsible in 2001 for about one-third of the U.S. man-made CO2 emissions (see Section 1.2.3). These emissions would be greatly reduced if natural gas were to be substituted for coal. There are two gains (1) The CO2 production using natural gas is about 56 of the production using coal, at the same thermal energy output (see Section 1.2.3). (2) Gas-fired combined-cycle combustion turbines can operate at a thermal efficiency of over 50 ,...

Options for Electricity Generation Need for Additional Generating Capacity

The worldwide demand for electricity will almost certainly increase substantially in the coming decades. The increase will partly be driven by an expansion in conventional uses, as world population grows and the underdeveloped countries strive to raise their presently very low per capita use of electricity. It may also be driven by the expanded use of electricity in relatively new applications such as the production of hydrogen and the desalination of water. The demand for electricity would...

External Factors Impacting Nuclear Energy

Verdicts on the internal factors discussed earlier will be influenced by perceptions of need. Here, factors external to nuclear power determine the apparent need. These include the following Energy and electricity demand. Economic expansion and population growth act to increase the demand for additional energy, including nuclear energy. Effective conservation measures reduce it. Limitations on oil and gas resources. The need for alternatives is enhanced if these resources are seen to be...

Internal Factors Impacting Nuclear Power

The future acceptability of nuclear energy, which we restrict to energy from nuclear fission here, will depend, in part, on internal factors the strengths and weaknesses of nuclear power itself. Key factors are as follows Nuclear accidents. The sine qua non for the acceptance of nuclear power is a long period of accident-free operation, worldwide. Any major nuclear accident will heighten fears of nuclear power and each decade of accident-free operation helps to alleviate them. Reactor designs....

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...

Carbon

A direct way of discouraging fossil fuel use, and even discriminating among fossil fuel uses, is the imposition of a carbon tax a levy on fossil fuel use based on the magnitude of the CO2 emissions. Such a tax would automatically give a competitive gain to both nuclear and renewable sources. For example, a tax of 0.50 per tonne of carbon emitted would have the following consequences An increase in the cost of electricity of 1.3 kWh for a coal-fired plant operating at 33 efficiency and of 0.46...