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Other advantages include greater abundance of natural reserves of thorium, less radioactive waste and higher utilisation of fuel in thorium reactors. While compelling at first glance, the details reveal a somewhat more murky picture.
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The molten salt architecture which gives certain thorium reactors high intrinsic safety equally applies to proposed fourth-generation designs using uranium. It is also true that nuclear physics technicalities make thorium much less attractive for weapons production, but it is by no means impossible; the USA and USSR each tested a thorium-based atomic bomb in Other perceived advantages similarly diminish under scrutiny. There is plenty of uranium ore in the world and hence the fourfold abundance advantage of thorium is a moot point. Producing less long-lived radioactive waste is certainly beneficial, but the vexed question remains of how to deal with it.
Stating that thorium is more efficiently consumed is the most mischievous of the claimed benefits. Fast-breeder uranium reactors have much the same fuel efficiency as thorium reactors. None of these factors are reasons to ignore thorium, which may yet prove to have a significant role to play. New thorium-based reactors under construction in India and China will focus attention once again on the viability of thorium power. However, only time will tell whether thorium can strike a disruptive path forward.
From a national perspective, the development of thorium technology would be a major boost. Developing a market for thorium would also solve a serious problem for the green-technology rare earth industry. Thorium is an unwelcome contaminant in rare earth ores, making the tailings slightly radioactive. This leads to social and political problems in the processing phase as seen recently in the licensing struggles of Australian-owned Lynas Corporation in Malaysia.
Having an avenue to sell the extracted thorium would change the whole dynamics of rare earth processing. As for whether thorium might reframe the discussion of nuclear power in Australia, the question comes too soon. The engineering and economics of thorium must first be demonstrated. If Australia does eventually decide to build nuclear power plants, the best choice would almost certainly be a proven design based on existing third-generation uranium technology.
Such a decision is, however, a long way down the road. The real question is whether Australia can find a way forward to have a civilised discussion about how to generate non-fossil baseload power. Low pay, earnings mobility and policy — Manchester, Lancashire. Edition: Available editions United Kingdom. Thorium has its advantages over uranium nuclear power, but is it right for Australia?
Nigel Marks , Curtin University. Thorium: critically different Thorium atomic number 90 shares several similarities with its neighbour two doors down on the periodic table, uranium atomic number This experience has called attention to two principal difficulties that must be overcome.
Sodium reacts with water to generate high heat, a possible accident source. This characteristic has led sodium-cooled reactor designers to include a secondary sodium system to isolate the primary coolant in the reactor core from the water in the electricity- producing steam system.
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Some new designs focus on novel heat-exchanger technologies that guard against leaks. The second challenge concerns economics. Because sodium-cooled reactors require two heat-transfer steps between the core and the turbine, capital costs are increased and thermal efficiencies are lower than those of the most advanced gas- and water-cooled concepts about 38 percent in an advanced sodium-cooled reactor compared with 45 percent in a supercritical water reactor.
Moreover, liquid metals are opaque, making inspection and maintenance of components more difficult. Next-generation fast-spectrum reactor designs attempt to capitalize on the advantages of earlier configurations while addressing their shortcomings. The technology has advanced to the point at which it is possible to envision fast-spectrum reactors that engineers believe will pose little chance of a meltdown.
Nuclear energy has arrived at a crucial stage in its development. The economic success of the current generation of plants in the U. Novel reactor designs can dramatically improve the safety, sustainability and economics of nuclear energy systems in the long term, opening the way to their widespread deployment. Nuclear Power Primer Most of the world's nuclear power plants are pressurized water reactors. In these systems, water placed under high pressure atmospheres to suppress boiling serves as both the coolant and the working fluid.
Initially developed in the U. The reactor core of a pressurized water reactor is made up of arrays of zirconium alloy—clad fuel rods composed of small cylinders pellets of mildly enriched uranium oxide with the diameter of a dime. A typical bysquare array of fuel rods constitutes a fuel assembly, and about fuel assemblies are arranged to form a reactor core. Cores, which are typically approximately 3. The nuclear fission reactions produce heat that is removed by circulating water. The coolant is pumped into the core at about degrees Celsius and exits the core at about degrees C.
To control the power level, control rods are inserted into the fuel arrays. Control rods are made of materials that moderate the fission reaction by absorbing the slow thermal neutrons emitted during fission. They are raised out of or lowered into the core to control the rate of the nuclear reaction. To change the fuel or in the case of an accident, the rods are lowered all the way into the core to shut down the reaction. In the primary reactor coolant loop, the hot water exits the reactor core and flows through a heat exchanger called a steam generator , where it gives up its heat to a secondary steam loop that operates at a lower pressure level.
The steam produced in the heat exchanger is then expanded through a steam turbine, which in turn spins a generator to produce electricity typically to 1, megawatts. The steam is then condensed and pumped back into the heat exchanger to complete the loop. Aside from the source of heat, nuclear power plants are generally similar to coal- or fuel-fired electrical generating facilities.
There are several variants of the light-water-cooled reactor, most notably boiling-water reactors, which operate at lower pressure usually 70 atmospheres and generate steam directly in the reactor core, thus eliminating the need for the intermediate heat exchanger. In a smaller number of nuclear power plants, the reactor coolant fluid is heavy water containing the hydrogen isotope deuterium , carbon dioxide gas or a liquid metal such as sodium. The reactor pressure vessel is commonly housed inside a concrete citadel that acts as a radiation shield.
The citadel is in turn enclosed within a steel-reinforced concrete containment building. The containment building is designed to prevent leakage of radioactive gases or fluids in an accident. In the U. Although no new nuclear facilities have been ordered in the U. In the past 10 years alone, American nuclear plants have added more than 23, megawatts—the equivalent of 23 large power plants—to the total electricity supply despite the lack of any new construction.
In the meantime, the production increase has lowered the unit cost of nuclear power generation. This improvement has led to growing interest among the business community in extending plant operating licenses and perhaps purchasing new nuclear facilities. It may be surprising to some that the use of nuclear energy has direct benefits to the environment, specifically air quality. Unlike fossil-fuel power plants, nuclear plants do not produce carbon dioxide, sulfur or nitrogen oxides.
Nuclear power production in the U. A very straightforward approach is to use the energy from a high-temperature nuclear reactor to drive a steam reforming reaction of methane.
This process still creates carbon dioxide as a by-product, however. Several direct thermochemical reactions can give rise to hydrogen using water and high temperature. Research on the thermochemical decomposition of sulfuric acid and other hydrogen-forming reactions is under way in Japan and the U.
Thorium in Australia
The economics of nuclear-based hydrogen remain to be proved, but enormous potential exists for this route, perhaps operating in a new electricity-hydrogen cogeneration mode. Achievement of this aim would make them competitive on a unit-cost basis with the most economical alternative, the combined-cycle natural gas plant. Any next generation facilities must in addition be completed within about three years to keep financing costs to a manageable level. New streamlined, but as yet untried, licensing procedures should speed the process. Given the past experience with nuclear projects in the U.
To achieve the cost objective, nuclear engineers are seeking to attain higher thermal efficiencies by raising operating temperatures and simplifying subsystems and components. Speeding plant construction will require the standardization of plant designs, factory fabrication and certification procedures; the division of plants into smaller modules that avoid the need for on-site construction; and the use of computerized assembly-management techniques. In this way, the building work can be verified in virtual reality before it proceeds in the field. The Three Mile Island accident in focused the attention of plant owners and operators on the need to boost safety margins and performance.
The number of so-called safety-significant events reported to the Nuclear Regulatory Commission, for example, averaged about two per plant per year in but had dropped to less than one tenth of that by In the meantime, public confidence in the safety of nuclear power has been largely restored since the Chernobyl accident in , according to recent polls. Long-term safety goals for next-generation nuclear facilities were formulated during the past year by international and domestic experts at the request of the U.
Thorium Nuclear Reactors: A safer alternative? | HowStuffWorks
Department of Energy. They established three major objectives: to improve the safety and reliability of plants, to lessen the possibility of significant damage during accidents, and to minimize the potential consequences of any accidents that do occur. Accomplishing these aims will require new plant designs that incorporate inherent safety features to prevent accidents and to keep accidents from deteriorating into more severe situations that could release radioactivity into the environment.
The Yucca Mountain long-term underground repository in Nevada is being evaluated to decide whether it can successfully accept spent commercial fuel. It is, however, a decade behind schedule and even when completed will not accommodate the quantities of waste projected for the future. This approach results in only about 1 percent of the energy content of the uranium being converted to electricity.
It also produces large volumes of spent nuclear fuel that must be disposed of in a safe fashion. Both these drawbacks can be avoided by recycling the spent fuel—that is, recovering the useful materials from it. Most other countries with large nuclear power programs—including France, Japan and the U. In these countries, used fuel is recycled to recover uranium and plutonium produced during irradiation in reactors and reprocess it into new fuel. This effort doubles the amount of energy recovered from the fuel and removes most of the long-lived radioactive elements from the waste that must be permanently stored.
It should be noted, though, that recycled fuel is today more expensive than newly mined fuel. Current recycling technology also leads to the separation of plutonium, which could potentially be diverted into weapons. Essentially all nuclear fuel recycling is performed using a process known as PUREX plutonium uranium extraction , which was initially developed for extracting pure plutonium for nuclear weapons.
In PUREX recycling, used fuel assemblies are transported to a recycling plant in heavily shielded, damage-resistant shipping casks. The fuel assemblies are chopped up and dissolved by strong acids. The fuel solution then undergoes a solvent-extraction procedure to separate the fission products and other elements from the uranium and the plutonium, which are purified.
The uranium and plutonium are used to fabricate mixed oxide fuel for use in light-water reactors. Recycling helps to minimize the production of nuclear waste. To reduce the demand for storage space, a sustainable nuclear fuel cycle would separate the short-lived, high-heat-producing fission products, particularly cesium and strontium These elements would be held separately in convectively cooled facilities for to years, until they had decayed to safe levels. An optimized closed fast-reactor fuel cycle would recycle not just the uranium and plutonium but all actinides in the fuel, including neptunium, americium and curium.
In a once-through fuel cycle, more than 98 percent of the expected long-term radiotoxicity is caused by the resulting neptunium and plutonium with half-lives of 2. Controlling the long-term effects of a repository becomes simpler if these long-lived actinides are also separated from the waste and recycled. The removal of cesium, strontium and the actinides from the waste shipped to a geological repository could increase its capacity by a factor of Because of continuing interest in advancing the sustainability and economics of nuclear fuel cycles, several countries are developing more effective recycling technologies.
Today an electrometallurgical process that precludes the separation of pure plutonium is under development in the U. Advanced aqueous recycling procedures that offer similar advantages are being studied in France, Japan and elsewhere. When nations acquire nuclear weapons, they usually develop dedicated facilities to produce fissile materials rather than collecting nuclear materials from civilian power plants. Commercial nuclear fuel cycles are generally the most costly and difficult route for production of weapons-grade materials. New fuel cycles must continue to be designed to guard against proliferation.
From Ashes to Honey: Nuclear Alternatives
How Secure are Nuclear Plants from Terrorists? The tragic events of September 11, , raise troubling questions about the vulnerability of nuclear facilities to terrorist attacks. Although stringent civilian and military security countermeasures have been implemented to stop determined assaults, the deliberate crash of a large commercial airliner looms in the imagination.
- Contes et Légendes des Mille et Une Nuits (French Edition).
- Opening the Door to Immortality.
- The Thing About Thorium: Why The Better Nuclear Fuel May Not Get A Chance.
- Earthy Realism: The Meaning of Gaia (Societas).
- Considering an Alternative Fuel for Nuclear Energy - The New York Times.
- Il Sudario da Vinci (Italian Edition).
So, should Americans be worried? The answer is no and yes. A nuclear power plant is not an easy target for an airliner flying at high speed, because an off-center hit on a domed, cylindrical containment building would not substantially affect the building structure. Located at or below grade, the reactor core itself is typically less than 10 feet in diameter and 12 feet high. It is enclosed in a heavy steel vessel surrounded by a concrete citadel. Despite not being designed to resist acts of war, containment enclosures can withstand crashes of small aircraft.
Even though the reactor core is protected, some of the piping and reactor cooling equipment, the auxiliary apparatus and the adjacent switchyard may be vulnerable to a direct hit. Nuclear power stations, however, are outfitted with multiple emergency cooling systems, as well as with emergency power supplies, should power be disabled.