Information about Nuclear Technology

Nuclear technology is technology that involves the reactions of atomic nuclei. It has found applications from smoke detectors to nuclear reactors, and from gun sights to nuclear weapons. There is a great deal of public concern about its possible implications, and every application of nuclear technology is reviewed with care.

History

Discovery

In 1896, Henri Becquerel was investigating phosphorescence in uranium salts when he discovered a new phenomenon which came to be called radioactivity. He, Pierre Curie and Maria Sklodowska-Curie began investigating the phenomenon. In the process they isolated the element radium, which is highly radioactive. They discovered that radioactive materials produce intense, penetrating rays of several distinct sorts, which they called alpha rays, beta rays and gamma rays. Some of these kinds of radiation could pass through ordinary matter, and all of them could cause damage in large amounts - all the early researchers received various radiation burns, much like sunburn, and thought little of it.

The new phenomenon of radioactivity was seized upon by the manufacturers of quack medicine (as had the discoveries of electricity and magnetism, earlier), and any number of patent medicines and treatments involving radioactivity were put forward. Gradually it came to be realized that the radiation produced by radioactive decay was ionizing radiation, and that quantities too small to burn presented a severe long-term hazard. Many of the scientists working on radioactivity died of cancer as a result of their exposure. Radioactive patent medicines mostly disappeared, but other applications of radioactive materials persisted, such as the use of radium salts to produce glowing dials on meters.

As the atom came to be better understood, the nature of radioactivity became clearer: some atomic nuclei are unstable, and they can decay, releasing energy (in the form of gamma rays, high-energy photons) and nuclear fragments (alpha particles, a pair of protons and a pair of neutrons, and beta particles, high-energy electrons).

World War 2

During World War II, nuclear reactions were sufficiently well understood that all the factions began to see the possibility of constructing a nuclear weapon. Nuclear reactions release far more energy per reaction than chemical reactions, so if large numbers of reactions could be induced to occur at once, tremendous amounts of energy could be released. The British and the Americans set up the Manhattan Project under the direction of Robert Oppenheimer to build such a device.

Nuclear Fission

Radioactivity is generally a slow and difficult process to control, and is unsuited to building a weapon. However, other nuclear reactions are possible. In particular, a sufficiently unstable nucleus can undergo nuclear fission, breaking into two smaller nuclei and releasing energy and some fast neutrons. This neutron could, if captured by another nucleus, cause that nucleus to undergo fission as well. The process could then continue in a nuclear chain reaction. Such a chain reaction could release a vast amount of energy in a short amount of time.

Nuclear Weapons

The design of a nuclear weapon is more complicated than it might seem - it is quite difficult to ensure that such a chain reaction consumes a significant fraction of the fuel before the device flies apart. The construction of a nuclear weapon is also more difficult than it might seem, as no naturally-occurring substance is sufficiently unstable for this process to occur. One isotope of uranium, namely uranium-235, is naturally-occurring and sufficiently unstable, but it is always found mixed with the more stable isotope uranium-238. Thus a complicated and difficult process of isotope separation must be performed to obtain uranium-235. Alternatively, the element plutonium possesses an isotope that is sufficiently unstable for this process to be usable. Plutonium does not occur naturally, so it must be manufactured in a nuclear reactor. Ultimately, the Manhattan Project manufactured nuclear weapons based on each of these.

The first atomic bomb was detonated in a test code-named "Trinity", near Alamogordo on July 16, 1945. After much debate on the morality of using such a horrifying weapon, two bombs were dropped on the Japanese cities Hiroshima and Nagasaki, and the Japanese surrender followed shortly.

The nations that could afford to began nuclear weapons programs, developing ever more destructive bombs in an arms race to obtain what they called a nuclear deterrent. Throughout the Cold War, the opposing powers had huge nuclear arsenals, sufficient to kill hundreds of millions of people. Generations of people grew up under the shadow of nuclear devastation.

However, the tremendous energy release in the detonation of a nuclear weapon also suggested the possibility of a new energy source.

Nuclear Ships

Nuclear submarines were built, able to travel at speed while submerged for months at a time. Nuclear ships were built, primarily aircraft carriers, although a few icebreakers were built. Research projects were started into the possibility of nuclear-powered aircraft and nuclear thermal rockets.

Nuclear Power

Main article: Nuclear power

Commercial nuclear power began in the early 1950's in the US, UK, and Soviet Union. The first commercial reactors were heavily based on either research reactors, or military reactors. The first commercial nuclear reactor to go online in the US was the Shippingport Atomic Power Station in Western Pennsylvania. In some contries any form of nulear power is banned.

Types of nuclear reaction

The vast majority of everyday phenomena do not involve nuclear reactions. Most everyday phenomena only involve gravity and electromagnetism. Of the fundamental forces of nature, these are the weakest, but the strong nuclear force and the weak nuclear force are essentially short-range forces so they do not play a role outside the atomic nucleus. Atomic nuclei are generally kept apart because they contain positive electrical charges and therefore repel each other, so in ordinary circumstances they cannot meet.

Most natural nuclear reactions fall under the heading of radioactive decay, where a nucleus is unstable and decays after a random interval. The most common processes by which this can occur are alpha decay, beta decay, and gamma decay. Under suitable circumstances, a large unstable nucleus can break into two smaller nuclei, undergoing nuclear fission.

If these neutrons are captured by a suitable nucleus, they can trigger fission as well, leading to a chain reaction. A mass of radioactive material large enough (and in a suitable configuration) is called a critical mass. When a neutron is captured by a suitable nucleus, fission may occur immediately, or the nucleus may persist in an unstable state for a short time. If there are enough immediate decays to carry on the chain reaction, the mass is said to be prompt critical, and the energy release will grow rapidly and uncontrollably, usually leading to an explosion. However, if the mass is critical only when the delayed neutrons are included, the reaction can be controlled, for example by the introduction or removal of neutron absorbers. This is what allows nuclear reactors to be built. Fast neutrons are not easily captured by nuclei; they must be slowed (slow neutrons), generally by collision with the nuclei of a neutron moderator, before they can be easily captured.

If nuclei are forced to collide, they can undergo nuclear fusion. This process may release or absorb energy. When the resulting nucleus is lighter than that of iron, energy is normally released; when the nucleus is heavier than that of iron, energy is generally absorbed. This process of fusion occurs in stars, and is the way all elements heavier than helium were produced. Because of the very strong repulsion of nuclei, fusion is difficult to achieve in a controlled fashion. Fusion bombs obtain their enormous destructive power from fusion, but obtaining controlled fusion power has so far proved elusive. Controlled fusion can be achieved in particle accelerators; this is how many synthetic elements were produced. The Farnsworth-Hirsch Fusor is a device which can produce controlled fusion (and which can be built as a high-school science project), albeit at a net energy loss. It is sold commercially as a neutron source.

Nuclear Accidents

Three Mile island Incident (1979)

The Three Mile Island incident, coupled with the release of the disaster film The China Syndrome greatly impacted the public's perception of nuclear power. Many human factors engineering improvements were made to American power plants in the wake of Three Mile Island's partial meltdown.

Chernobyl Accident (1986)

The Chernobyl accident in 1986 further alarmed the public about nuclear power. While design differences between the RBMK reactor used at Chernobyl and most western reactors virtually eliminate the possibility of such an accident occurring outside of the former Soviet Union, it is only recently that the general public in the United States has started to embrace nuclear energy.

Examples of Nuclear Technology

Nuclear Power

See Nuclear Power

Medical Applications

Imaging - medical and dental x-ray imagers use of Cobalt-60 or other x-ray sources.

Industrial Applications

Oil and Gas Exploration- Nuclear well logging is used to help predict the commercial viability of new or existing wells. The technology involves the use of a neutron or gamma-ray source and a radiation detector which are lowered into boreholes to determine the properties of the surrounding rock such as porosity and lithography.[1]

Road Construction - Nuclear moisture/density gauges are used to determine the density of soils, asphalt, and concrete. Typically a Cesium-137 source is used.

Food Processing and Agriculture

In an effort to find new markets for isotopes, the Canadian nuclear industry is promoting the use of intense radiation from cobalt-60 to kill insects and microbes in spices, fruit, poultry, grain and other foodstuffs. The purpose is to prolong shelf life. A similar technology is used to sterilize medical equipment.

A Parliamentary committee recommended against the use of food irradiation without further study. Irradiation creates new chemical substances (radiolytic products) in the food, some of which are carcinogenic. Children fed irradiated wheat have shown chromosome damage. As well, irradiating food reduces the vitamin content.

The industry proposes that irradiated food be labeled inconspicuously to minimize consumer anxiety.^[1]

References

See also

• Nuclear Energy Institute – Beneficial Uses of Radation
• Nuclear Technology

•  • [ e] Major fields of technology
Applied science	Artificial intelligence • Ceramic engineering • Computing technology • Electronics • • Energy storage • Engineering physics • Environmental technology • Materials science & engineering • Microtechnology • Nanotechnology • Nuclear technology • Optical engineering
Information and communication	Communication • Graphics • Music technology • Speech recognition • Visual technology
Industry	Construction • Financial engineering • Manufacturing • Machinery • Mining
Military	Bombs • Guns and Ammunition • Military technology and equipment • Naval engineering
Domestic	Domestic appliances • Domestic technology • Educational technology • Food technology
Engineering	Aerospace • Agricultural • Architectural • Bioengineering • Biochemical • Biomedical • Ceramic • Chemical • Civil • Computer • Construction • Cryogenic • Electrical • Electronic • Environmental • Food • Industrial • Materials • Mechanical • Mechatronics • Metallurgical • Mining • Naval • Nuclear • Petroleum • Software • Structural • Systems • Textile • Tissue
Health and safety	Biomedical engineering • Bioinformatics • Biotechnology • Cheminformatics • Fire protection engineering • Health technologies • Pharmaceuticals • Safety engineering • Sanitary engineering
Transport	Aerospace • Aerospace engineering • Marine engineering • Motor vehicles • Space technology • Transport

•  • [ e] Nuclear technology
Nuclear engineering	Nuclear physics Nuclear fission Nuclear fusion Radiation Ionizing radiation Atomic nucleus Nuclear safety Nuclear chemistry
Nuclear material	Nuclear fuel Fertile material Thorium Uranium Enriched uranium Depleted uranium Plutonium
Nuclear power	Nuclear reactor technology Radioactive waste Fusion power Future energy development Inertial fusion power plant Pressurized water reactor Boiling water reactor Generation IV reactor Fast breeder reactor Fast neutron reactor Magnox reactor Advanced gas-cooled reactor Gas-cooled fast reactor Molten salt reactor Liquid-metal-cooled reactor Lead-cooled fast reactor Sodium-cooled fast reactor Supercritical water reactor Very high temperature reactor Pebble bed reactor Integral Fast Reactor Nuclear propulsion Nuclear thermal rocket Radioisotope thermoelectric generator
Nuclear medicine	PET SPECT Gamma (Anger) Camera Radiation therapy Tomotherapy Proton therapy Brachytherapy BNCT
Nuclear weapons	History of nuclear weapons Nuclear warfare Nuclear arms race Nuclear weapon design Nuclear explosion Effects of nuclear explosions Nuclear testing Nuclear delivery Nuclear proliferation List of states with nuclear weapons List of nuclear tests