The Need for Nuclear Fusion

	Sign In Sign-Up

The Need for Nuclear Fusion

Introduction

The world's supply of fossil fuels is running out. There may only be 40 years left of oil, 60 years of gas and 200 years of coal. Renewables such as wind, solar, hydro-electric and biomass are estimated to be able to supply about 30% of demand at best.

Nuclear Fission

Nuclear fission is the splitting of an atom into two or more parts. When such an occurrence takes place, a very large amount of energy is released. This can occur very quickly as in an atomic bomb, or in a more controlled manner allowing the energy to be captured for useful purposes. Only a few naturally occurring substances are easily fissionable. These include uranium-235 and plutonium-239, two isotopes of uranium and plutonium. Isotopes are forms of the same chemical element that have the same number of protons in their nuclei, but a different number of neutrons.

Starting a fission reaction is accomplished by bombarding fissionable nuclei with neutrons. This causes the nuclei to fly apart, splitting into two fission products and emitting two or three neutrons of their own. These neutrons may break apart other nearby fissionable nuclei, starting a chain reaction, and resulting in the release of a great deal of energy in the form of radiation and heat. The major fragments of the split atoms are now different chemical elements, all highly radioactive. These fission products include such isotopes as iodine-131, caesium-137 and strontium-90. Naturally occurring uranium contains about 99.3% uranium-238, a non-fissionable isotope of uranium, and only 0.7% of the fissionable uranium-235. Uranium enrichment increases the proportion of uranium-235 in the mixture, enabling it to sustain a fission reaction. Most present day reactors use enriched uranium where the proportion of the U-235 isotope has been increased from 0.7% to about 3 or up to 4%. Such uranium fuel is placed in the core of a nuclear reactor, and the heat given off by the fission chain reaction is captured to produce electricity. Reserves of uranium are estimated at around 50 years.

In order to maximise the use of uranium, breeder reactors have been developed. The plutonium-239 breeder reactor is commonly called a fast breeder reactor, and the cooling and heat transfer is done by a liquid metal. The metals which can accomplish this are sodium and lithium, with sodium being the most abundant and most commonly used. The construction of the fast breeder requires a higher enrichment of U-235 than a light-water reactor, typically 15 to 30%. The reactor fuel is surrounded by a "blanket" of non-fissionable U-238 which is converted to P-239 by neutron irradiation. P-239 is a strong alpha emitter with a half-life of 24,000 years. Fuelling a fast breeder reactor with plutonium would require operation of a reprocessing plant that could handle large amounts of spent fuel with high plutonium concentrations. Very few of these reactors have been built due to their expense and the fire hazards associated with sodium.

Nuclear fission power is a very expensive method of generating electricity when taking into account the costs of decommissioning and storing nuclear waste. No new nuclear plants have been ordered in the US since the Three Mile Island accident in 1979 and in Europe the nuclear option has become less popular following the 1986 explosion at Chernobyl. Most nuclear power plants have been built by monopoly utilities, and the costs were passed through to consumers. But with governments around the world now opening electric power markets to competition for the first time, nuclear power is likely to decline.

Atomic Weapons

One spin-off from a nuclear power programme is the ability to produce nuclear weapons. Highly Enriched Uranium (HEU) contains at least 90% U-235 and is suitable for weapons use. Fission devices use uranium-235 or plutonium-239 as fuel. When a sufficient amount of the fuel is suddenly brought together, the fission of one nucleus causes the fission of others; these bring about the fission of still more in turn. The process continues until all the fuel is consumed. The amount of fuel needed for the chain reaction to occur is called the critical mass. The critical mass depends upon the type and purity of the fuel and upon the amount of the fuel present (3 kg HEU or plutonium-239). In gun-type devices, one subcritical-sized piece of fuel is fired down a gunlike barrel into another, so that there is a supercritical amount at the moment of impact that initiates the chain reaction. In implosion-type devices, explosives surround a hollow sphere of fissionable fuel, which at the moment of detonation is squeezed into one supercritical mass. The implosion technique is the more effective and requires less fuel.

Fusion devices are inherently vastly more powerful than those utilizing only fission. A typical fission device produces a blast equivalent to 20 thousand tonnes of TNT whereas a fusion device can produce a 60 million tonne blast. A fission bomb is used as a detonator, to generate the extremely high temperatures needed to induce the atomic nuclei of hydrogen isotopes (deuterium and tritium) to combine, or fuse.

Since it is extremely difficult to acquire HEU or P-239 governments can produce their own under the guise of a nuclear power programme. The pioneers of nuclear power - US, USSR and Britain - went on to develop hydrogen bombs in the 1950s. Since then China, France, India, Israel, Pakistan and probably South Africa have acquired nuclear weapons. It is obviously hypocritical for the western powers to sanction other nations for developing these weapons while maintaining their own arsenals.

As well as the unlikely threat from "rogue" states there is the real possibility of nuclear terrorism. Islamic militants have little difficulty acquiring high explosives and may one day procure nuclear material. The radioactive toxins that are the by-product of electricity generation may provide the source (spent fuel contains U-235 and P-239 and can be enriched). And continued US military and financial support for the fanatical Zionist regime can only increase the threat.

Nuclear Fusion

Nuclear Fusion is the energy-producing process which takes place continuously in the sun and stars. In the core of the sun at temperatures of 10-15 million degrees Celsius, Hydrogen is converted to Helium providing enough energy to sustain life on earth. For energy production on earth different fusion reactions are involved. The most suitable reaction occurs between the nuclei of the two heavy forms (isotopes) of Hydrogen - Deuterium (D) and Tritium (T); eventually reactions involving just Deuterium or Deuterium and Helium (³He) may be used.

At the temperatures required for the D-T fusion reaction - over 100 Million deg. C - the fuel has changed its state from gas to plasma. In a plasma, the electrons have been separated from the atomic nuclei (usually called the "ions"). Understanding plasma required major developments in physics. Plasmas are now used widely in industry, especially for semi-conductor manufacture.

Nuclear Fusion offers a vast, new source of energy with plentiful fuels. It is inherently safe since any malfunction results in a rapid shutdown. There is no atmospheric pollution leading to acid rain or "greenhouse" effect. Radioactivity of the reactor structure, caused by the neutrons, decays rapidly and can be minimised by careful selection of low-activation materials. Provision for geological time-span disposal is not needed. Deuterium fuel is abundant as it can be extracted from all forms of water. If all the world's electricity were to be provided by fusion power stations, deuterium supplies would last for millions of years. Tritium does not occur naturally and will be manufactured from Lithium within the machine. Lithium, the lightest metal, is plentiful in the earth's crust. If all the world's electricity were to be provided by fusion, known reserves would last for at least 1000 years. The by-product, helium, has no role in nuclear weapons production.

Funding

In 1996, the US Department of Energy (DOE) cut off contributions to the International Thermonuclear Experimental Reactor (ITER). The $14 billion project will instead be built with Canadian, European, Japanese and Russian support. The DOE has a $225 million-a-year budget for the Fusion Energy Science Program. Contrast this sum with the estimated $100 to $200 billion for National Missile Defence, which will offer no defence whatever against a nuclear device smuggled into the country. The estimated lifetime cost of Britain's Trident nuclear missiles and submarines is £23 billion. While Trident won't defend us against a nuclear attack it does enable us to get some serious retaliation in afterwards, although blitzing foreign capitals might not be morally justifiable, quite apart from the environmental consequences!

What is required is a diversion from profligate military expenditure into fusion research. Although the investment may not bear fruit within our lifetime it will offer future generations an unlimited supply of clean energy - without the prospect of nuclear annihilation.

Resources

Fast Breeder Reactors

The Threat of Nuclear Terrorism

Nuclear Power Nears Peak

Physical, Nuclear, and Chemical, Properties of Plutonium

ITER

Joint European Torus (JET)

Princeton Plasma Physics Laboratory

Fusion Energy Educational Web Site

University of California at Berkeley, Nuclear Fusion Home Page

Other sites by the same author: