I remembered the line from the Hindu scripture, the Bhagavad-Gita. Vishnu is trying to persuade the Prince that he should do his duty and to impress him takes on his multi-armed form and says, 'Now I am become Death, the destroyer of worlds. The explosion had the energy equivalent of approximately 20, tons of TNT. The first war-use atomic bomb dropped on Hiroshima, Japan, on August 6, That atomic bomb, dubbed "Little Boy," had a uranium core, though.
The second bomb, dropped on Nagasaki, Japan, in August 9, , had a plutonium core. Freshly prepared plutonium metal has a silvery bright color but takes on a dull gray, yellow, or olive green tarnish when oxidized in air.
The metal quickly dissolves in concentrated mineral acids. A large piece of plutonium feels warm to the touch because of the energy given off by alpha decay; larger pieces can produce enough heat to boil water. At room temperature alpha-form plutonium the most common form is as hard and brittle as cast iron. It can be alloyed with other metals to form the room-temperature stabilized delta form, which is soft and ductile.
Unlike most metals, plutonium is not a good conductor of heat or electricity. It has a low melting point and an unusually high boiling point. Plutonium can form alloys and intermediate compounds with most other metals, and compounds with a variety of other elements. Some alloys have superconductive abilities and others are used to make nuclear fuel pellets.
Its compounds come in a variety of colors, depending on the oxidation state and how complex various ligands are. In aqueous solution there are five valance ionic states. Plutonium, along with all of the other transuranium elements, is a radiological hazard and must be handled with specialized equipment and precautions. Animal studies have found that a few milligrams of plutonium per kilogram of tissue are lethal.
Plutonium generally isn't found in nature. Trace elements of plutonium are found in naturally occurring uranium ores. Here, it is formed in a way similar to neptunium: by irradiation of natural uranium with neutrons followed by beta decay. Primarily, however, plutonium is a byproduct of the nuclear power industry. Early heart pacemakers used Pu as the power source, and after 30 years some were still running well. It takes about 10 kilograms of nearly pure Pu to make a bomb though the Nagasaki bomb in used less.
Producing this requires 30 megawatt-years of reactor operation, with frequent fuel changes and reprocessing of the 'hot' fuel. Allowing the fuel to stay longer in the reactor increases the concentration of the higher isotopes of plutonium, in particular the Pu isotope, as can be seen in the Table above. For weapons use, Pu is considered a serious contaminant, due to higher neutron emission and higher heat production.
It is not feasible to separate Pu from Pu The operational requirements of power reactors and plutonium production reactors are quite different, and so therefore is their design. An explosive device could be made from plutonium extracted from low burn-up reactor fuel i. Typical 'reactor-grade' plutonium recovered from reprocessing used power reactor fuel has about one-third non-fissile isotopes mainly Pu d. In the UK, the Magnox reactors were designed for the dual use of generating commercial electricity as well as being able to produce plutonium for the country's defence programme.
A report released by the UK's Ministry of Defence MoD says that both the Calder Hall and the Chapelcross power stations, which started up in and respectively, were operated on this basis 3. The government confirmed in April that production of plutonium for defence purposes had ceased in the s at these two stations, which are both now permanently shutdown. The other UK Magnox reactors were civil stations subject to full international safeguards. International safeguards arrangements applied to traded uranium extend to the plutonium arising from it, ensuring constant audits even of reactor-grade material.
This addresses uncertainty as to the weapons proliferation potential of reactor-grade plutonium. The 'direct use' definition applies also to plutonium which has been incorporated into commercial MOX fuel, which as such certainly could not be made to explode.
As can be discerned from the attributes of each, it is the first which produces weapons-usable material. Total world generation of reactor-grade plutonium in spent fuel is some 70 tonnes per year. About one-third of the separated Pu has been used in mixed oxide MOX fuel. The UK's plutonium stockpile is tonnes of separated civil plutonium from historic and current operations and foreign swaps.
At the end of France had about 75 tonnes of separated civil plutonium stored domestically. Some Japan at the end of had about 9 tonnes of separated civil plutonium stored domestically, plus The USA had no reactor-grade plutonium separated, but had at the end of about 45 tonnes of weapons-grade material destined for MOX.
China at the end of had about 41 tonnes of separated civil plutonium. Worldwide stocks of civil plutonium are estimated as around tonnes. In June , the USA and Russia agreed to dispose of 34 tonnes each of weapons-grade plutonium by Generation IV reactor designs are under development through an international project. Four of the six designs are fast neutron reactors and will thus utilize plutonium in some way. Despite being toxic both chemically and because of its ionising radiation, plutonium is far from being "the most toxic substance on Earth" or so hazardous that "a speck can kill".
On both counts there are substances in daily use that, per unit of mass, have equal or greater chemical toxicity arsenic, cyanide, caffeine and radiotoxicity smoke detectors.
There are three principal routes by which plutonium can get into human beings who might be exposed to it:. Ingestion is not a significant hazard, because plutonium passing through the gastro-intestinal tract is poorly absorbed and is expelled from the body before it can do harm. Contamination of wounds has rarely occurred although thousands of people have worked with plutonium.
Their health has been protected by the use of remote handling, protective clothing and extensive health monitoring procedures. The main threat to humans comes from inhalation. While it is very difficult to create airborne dispersion of a heavy metal like plutonium, certain forms, including the insoluble plutonium oxide, at a particle size less than 10 microns 0.
If inhaled, much of the material is immediately exhaled or is expelled by mucous flow from the bronchial system into the gastro-intestinal tract, as with any particulate matter. Some however will be trapped and readily transferred, first to the blood or lymph system and later to other parts of the body, notably the liver and bones.
It is here that the deposited plutonium's alpha radiation may eventually cause cancer. However, the hazard from Pu is similar to that from any other alpha-emitting radionuclides which might be inhaled.
It is less hazardous than those which are short-lived and hence more radioactive, such as radon daughters, the decay products of radon gas, which albeit in low concentrations are naturally common and widespread in the environment.
In the s some 26 workers at US nuclear weapons facilities became contaminated with plutonium. Intensive health checks of these people have revealed no serious consequence and no fatalities that could be attributed to the exposure. In the s plutonium was injected into and inhaled by some volunteers, without adverse effects.
In the s Queen Elizabeth II was visiting Harwell and was handed a lump of plutonium presumably Pu in a plastic bag and invited to feel how warm it was. Plutonium is one among many toxic materials that have to be handled with great care to minimize the associated but well understood risks. A supercritical mass is bigger than a critical mass, and is capable of achieving a growing chain reaction where the amount of energy released increases with time.
The amount of material necessary to achieve a critical mass depends on the geometry and the density of the material, among other factors. The critical mass of a bare sphere of plutonium metal is about 10 kilograms. It can be considerably lowered in various ways. The amount of plutonium used in fission weapons is in the 3 to 5 kilograms range. According to a recent Natural Resources Defense Council report 1 , nuclear weapons with a destructive power of 1 kiloton can be built with as little as 1 kilogram of weapon grade plutonium 2.
The smallest theoretical critical mass of plutonium is only a few hundred grams. In contrast to nuclear weapons, nuclear reactors are designed to release energy in a sustained fashion over a long period of time. This means that the chain reaction must be controlled—that is, the number of neutrons produced needs to equal the number of neutrons absorbed.
This balance is achieved by ensuring that each fission produces exactly one other fission. All isotopes of plutonium are radioactive, but they have widely varying half-lives. The half-life is the time it takes for half the atoms of an element to decay. For instance, plutonium has a half-life of 24, years while plutonium has a half-life of The various isotopes also have different principal decay modes.
The isotopes present in commercial or military plutonium are plutonium, , and Table 2 shows a summary of the radiological properties of five plutonium isotopes. The isotopes of plutonium that are relevant to the nuclear and commercial industries decay by the emission of alpha particles, beta particles, or spontaneous fission. Gamma radiation , which is penetrating electromagnetic radiation, is often associated with alpha and beta decays.
Various sources give slightly different figures for half-lives and energies. Table 3 describes the chemical properties of plutonium in air. These properties are important because they affect the safety of storage and of operation during processing of plutonium. The oxidation of plutonium represents a health hazard since the resulting stable compound, plutonium dioxide is in particulate form that can be easily inhaled.
It tends to stay in the lungs for long periods, and is also transported to other parts of the body. Ingestion of plutonium is considerably less dangerous since very little is absorbed while the rest passes through the digestive system.
Plutonium combines with oxygen, carbon, and fluorine to form compounds which are used in the nuclear industry, either directly or as intermediates. Table 4 shows some important plutonium compounds.
Plutonium metal is insoluble in nitric acid and plutonium is slightly soluble in hot, concentrated nitric acid.
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