System 80+ Standard [nucl. powerplnt] Design - Vol 12

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Except in rare ores, uranium was a trace material, and it would take a large amount of ore to produce relatively small amounts of reactor fuel, especially given that uranium was only about 0. Further, uranium ore was always mixed with other radioactive materials that would be discharged as waste in large quantities.

Plutonium produced in nuclear reactors could be used to make nuclear weapons, if separated from spent fuel. Safeguarding plutonium presented challenges that were not encountered with fossil fuels. The technological and resource base needed for nuclear weapons was to a very large extent the same as that needed for nuclear power. Thus, the problem of preventing proliferation of weapons while using nuclear power as an energy source would be a crucial security issue. These problems seem clear enough in hindsight. But how many were apparent in the early days?

Was the romance with the atom a case so intense that it blinded engineering judgment? Was it propaganda waged for economic or military purposes? Or was it a mixture of both? Chapter 2: Electricity Production and Nuclear Reactors An energy source cannot be inexhaustible in the economic sense unless it is priced so low that it can be used in essentially unlimited quantities.

After all, solar energy is "inexhaustible" in a physical sense in that we have a continual, huge, and, from a human point of view, essentially endless supply. Yet it is not in widespread use as an energy source because of the relatively high cost of putting it into a usable form, such as electricity. Thus, for solar energy or any other energy source to be "too cheap to meter" it must not only be plentiful in physical terms; it must also satisfy minimal economic criteria.

Even fossil fuels resources are huge, if resources such as oil shale are included. But oil shale and similar low-grade resources are generally not included in estimates of the recoverable fossil fuel resource base because they are economically and environmentally unviable. Let us take a look at the elements of the cost of a large scale electricity generating system, such as would be typical of nuclear power. Electricity on a large scale is produced by forcibly spinning conducting wires usually made of copper through a magnetic field.

Such a device is called an electric generator. The energy required to spin the generator and supply the current to the devices that use electricity must come from somewhere. This is the energy source for the electric power station. For instance, falling water is an energy source that is used to spin water turbines, which, in turn, drive electric generators. The most common energy sources for electricity generation are fossil fuels, which release their energy in the form of heat upon being burned.

This heat is converted into mechanical energy in a "heat engine. A boiler combined with a steam turbine is another way in which the chemical energy in fuels is converted into mechanical energy. The electricity from a large-scale generating station is transmitted at high voltage to minimize transmission losses to the areas where it will be used.


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Finally, there are extensive networks of wires and transformers that distribute electricity to consumers at the voltages they require for their applications. This scheme is used in all central-station electricity generation. The basic arrangement of a coal-fired power plant is the same, except that the reactor and steam-generator are replaced by a coal-fired boiler.

The cost elements of an electricity generation system based mainly on central station plants such as that diagrammed in Figure 1 are: capital cost of the power plant, including the boiler and steam turbine or other source of mechanical energy to drive the electricity generator and the generation system transmission lines distribution network for connecting the main electricity grid of transmission lines to consumers operating and maintenance cost other than fuel fuel cost.

The most important thing to note about this list when evaluating the official claims that nuclear energy could one day be too cheap to meter, is that all the cost elements of a nuclear electricity system other than the fuel would be common between an electric power station that used coal or another fossil fuel and one that used nuclear fuel either uranium or plutonium or some combination of the two. The principal difference between a nuclear power station and, say, a coal-fired power plant, is in the nature of the fuel.

In the one case, it is coal, which is burned in a boiler to generate hot gases, which in turn heat up water to produce steam. The boiler for using coal or oil or natural gas is designed to burn the fuel chemically. Nuclear energy does not come from chemical reactions, such as burning, but from nuclear reactions. The nuclear reactor merely replaces the boiler in a conventional fossil fuel power station. It generates the steam that drives the turbine. In other words, a nuclear power station differs from a conventional power station only in the fuel and the details by which the fuel is used in the boiler to generate heat.

An important detail here is that the nuclear fuel is much more compact because each fission releases about MeV megaelectron volts of energy, while burning one atom of carbon and turning it into carbon dioxide releases about 4 electron volts eV.

DungenessB | Cross Section | Nuclear reactor, Nuclear engineering, Nuclear power

The higher energy per fission means that the volume of nuclear fuel per unit of power output is far smaller than for fossil fuels. Let us now look at the actual costs of electricity generation at the time that Lewis Strauss made his famous "too cheap to meter" remark.

The price of electricity in to very large industrial consumers which is close to the cost of generation, since transmission and distribution costs for these consumers tend to be low was about 1 cent per kilowatt-hour of electric energy generated about 5. Subtracting the fuel cost for coal of about 0. This amounts to about 0.

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Since all other aspects of electricity generation were common between coal-fired and nuclear power station, the minimum conceivable charges for nuclear electricity as calculated for costs prevailing in would be 0. Thus, for the largest industrial consumers with factories near generating stations, the costs of nuclear electricity could be expected to be at least 60 percent of the costs of coal under assumptions so optimistic that they were considered unrealistic.

For small consumers, the cost reduction from this most optimistic assessment of nuclear energy would be far lower. This is because transmission and distribution constituted the lion's share of the cost of electricity for households and small businesses, that is for the overwhelming majority of consumers. The average price of electricity to small consumers in , the year of Strauss's speech, was 2. Thus, even if all fuel costs were eliminated, the average price of electricity to homes and small businesses would still have been 2. That was the best that nuclear energy could be expected to do.

Such cost estimates had, even on the surface, two unrealistic assumptions: Nuclear fuel would be so plentiful and so easy to produce that its costs would be insignificant compared to coal. Nuclear reactors and associated equipment would cost no more than conventional boilers, despite the greater technical complexity, high energy density, and radioactivity associated with nuclear energy. Let us take a look at each of these elements of the cost of nuclear power that were readily apparent in the s. At that time, radioactive waste disposal issues were not forecast to pose serious economic or political constraints on the development of nuclear energy.

Nuclear Fuel There are two basic fuels that are used in nuclear power reactors: uranium and plutonium. Thorium, which occurs in nature, is also potentially a nuclear energy resource. Like uranium, thorium is not fissile and cannot sustain a chain reaction. However, neutron absorption by a thorium nuclear converts it into uranium in a manner analogous to the conversion of uranium into plutonium Uranium is fissile and can be used for both nuclear weapons and nuclear power. However, no schemes for using thorium as an energy source have been commercialized. Nor has uranium been used in nuclear weapons, so far as public information indicates.

Uranium fuel Uranium is ubiquitous in very low concentrations. For instance, it is present in surface waters at concentrations of about 0. But it is too costly to extract pure uranium for use in nuclear reactors from such sources. Uranium ores typically contain two-tenths of one percent to roughly one-half percent uranium by weight. Of this, only about 7 kilograms is the fissile isotope uranium Uranium is present in nature in many different chemical forms.

The ores are processed in factories called uranium mills, where the other minerals and materials are separated from uranium. The wastes, containing thorium and radium, which are radioactive materials associated with the decay of uranium see Factsheet on Uranium , are discharged into tailings ponds.


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  • These tailings also contain non-radioactive toxic materials such as arsenic, molybdenum, and vanadium. For most reactors, the proportion of uranium in reactor fuel must be considerably greater than the 0. A large amount of processing is needed to accomplish this. The most expensive step is uranium enrichment, so called because it increases the proportion of uranium in the fuel.

    This process produces another stream of uranium, called depleted uranium, which has a uranium content far lower than natural uranium usually about 0. Figure 2 not available in on-line version of report shows the steps in converting uranium into a fuel for light water reactors, the most common kind of nuclear reactor used in power generation today. As a consequence of the practical necessities of uranium extraction and processing, the reality of the amounts of materials that needed to be handled and processed is far different than the romantic accounts of pellets the size of vitamin pills. While one gram of uranium was equivalent to 3 metric tons of coal, it typically required grams of natural uranium to obtain a gram of uranium in a practical fuel.


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    • And it took on the order of 50 kilograms of uranium ore to produce grams of uranium. Roughly an equal amount of low grade material littered the mine sites. In sum, about kilograms of ore and rejects had to be unearthed to produced a single gram of uranium fuel. Coal typically came in far richer seams, so that, for high-grade deposits, such as are commonly found in the western United States and elsewhere, the amount of additional material handled at the mine site was not far greater than the end product.

      Plutonium Fuel In the minds of its promoters, the promise of endless nuclear energy depended centrally on the conversion of uranium into plutonium A suitably romantic term was given to uranium, which was not a fissile material and hence not suitable as a reactor fuel. Uranium was called a "fertile" material because it gave birth to plutonium, a fissile nuclear fuel. As we have noted, uranium is converted into plutonium by bombardment with neutrons. Since a very large number of atoms of uranium nuclei must be so converted to produce substantial quantities of fuel, uranium must be placed in a situation where a correspondingly great numbers of neutrons are being continually generated.

      This happens in a nuclear reactor when uranium or another fissile material is undergoing fission at a suitable rate. Some of the plutonium produced in a nuclear reactor also undergoes fission, contributing to energy generation.

      But the rest cannot be directly used as a nuclear fuel because it is mixed with large quantities of unconverted uranium, residual uranium and highly radioactive fission products. In order to use plutonium as a reactor fuel or as a material for nuclear weapons , it must first be separated from the fission products and remaining uranium in the reactor fuel. Table 1 shows an example of one possible composition of reactor fuel when it is inserted into a reactor and the final composition when it is discharged from the reactor when it is called "spent fuel," though irradiated fuel would be a more accurate term.

      Table 1: Fresh enriched uranium fuel and spent fuel composition Substance Initial percentage by weight in fuel Percentage by weight in spent fuel after 3 years Uranium 97 Figures are rounded.

      Small quantity of uranium present in fresh and spent fuel is not listed because, while it is radiologically important, it is not relevant as an energy source. The set of steps required to extract plutonium from spent fuel is called "reprocessing" because it involves processing the fuel a second time around the first time being when the fuel is first fabricated for use in a reactor. Reprocessing is very costly for five reasons: Fission products are highly radioactive and must be handled remotely. Large quantities of corrosive chemicals are needed to separate the plutonium from the fission products and then from the residual uranium.