Plutonium can be obtained from special purpose plutonium production reactors, or as a by-product of commercial power or research reactors. At left is the loading face of the world's first plutonium production reactor, the B-Reactor located at Hanford Washington. Uranium fuel rods were inserted in the holes for irradiation. Essentially all of the plutonium currently in weapons throughout the world was produced in special purpose plutonium production reactors.
Initially each of the five declared nuclear powers began producing plutonium for weapons on a large scale many years before they developed significant numbers of commercial power reactors. Special purpose reactors were required for weapons production because there was no other sources of plutonium available. These special purpose reactors produce "weapon grade" plutonium, as opposed to grades with higher Pu concentrations, for two reasons: Economics: the only reason the reactor exists is to produce plutonium.
Burning plutonium up in fission, or transmuting it to less fissile Pu reduces output and increases cost up to a point, this must be balanced against the cost of processing fuel with low plutonium concentrations. Handling problems: although neutron emissions do not create serious problems in weapon design, it can produce problems with weapons manufacture and handling.
This property is used when reprocessing irradiated nuclear fuels. The subsequent absorption of a neutron by plutonium results in the formation of plutonium Absorption of another neutron by plutonium yields plutonium The higher isotopes are formed in the same way.
Since plutonium is the first in a string of plutonium isotopes created from uranium in a reactor, the longer a sample of uranium is irradiated, the greater the percentage of heavier isotopes. Plutonium must be chemically separated from the fission products and remaining uranium in the irradiated reactor fuel. This chemical separation is called reprocessing.
It is important to remember that this classification of plutonium according to grades is somewhat arbitrary. The ability of countries to build nuclear arsenals from reactor grade plutonium is not just a theoretical construct. It is a proven fact. All grades of plutonium can be used as weapons of radiological warfare which involve weapons that disperse radioactivity without a nuclear explosion.
Posted on July, Last modified April, Download this page as a PDF. Table 1. C Boiling point: deg. Table 2. Chemical properties and hazards of plutonium. Table 3. Humid, elevated temperatures PuO2 readily reacts to form plutonium dioxide Important Plutonium Compounds and their Uses Plutonium combines with oxygen, carbon, and fluorine to form compounds which are used in the nuclear industry, either directly or as intermediates. Ring of refined This image, by the U. Department of Energy, is in the public domain.
Elsewhere we've explored uranium enrichment , a dual-use technology which can be used either to enrich natural uranium for use in civil nuclear power reactors or, through further enrichment, for use in nuclear weapons. Now, let's examine the other path to the bomb: the production of plutonium from natural uranium by irradiation in a nuclear reactor and chemical separation. Let's begin with some basics.
If you want to build a nuclear fission weapon either for use by itself or as the trigger for a thermonuclear weapon , you need a critical mass of fissile material which is kept in a sub-critical configuration until the weapon is to be detonated, then rapidly assembled into a critical configuration where the nuclear chain reaction can run away, producing an explosive yield. A variety of elements and isotopes can theoretically be used in nuclear fission weapons, but since the start of the nuclear age, only two have ever actually been employed in weapons: uranium U and plutonium Pu Uranium exists in nature, but only 0.
Plutonium does not exist in nature. The half-life of Pu is just 24, years, so even if any were present when the Earth formed, it would have long ago decayed to other elements. But if you take U, which makes up the overwhelming fraction of natural uranium and bombard it with neutrons , some nuclei will absorb a neutron, transforming them into U a nucleus with the same 92 protons as U but an additional neutron.
But this nucleus has too many neutrons to be stable, and decays with a half-life of Np, while more stable than U, remains unstable and with a half-life of 2. Here is how nuclear chemists write this sequence of reactions. This seems pretty simple. 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.
Half-life is the time it takes for a radionuclide to lose half of its own radioactivity. The fissile isotopes can be used as fuel in a nuclear reactor, others are capable of absorbing neutrons and becoming fissile i. Alpha decays are generally accompanied by gamma radiation.
The term 'fissionable' applies to isotopes that can be made to undergo fission. If a fissionable isotope only requires neutrons with low kinetic energy to undergo fission, then it is said to 'fissile'.
Thus, all fissile isotopes are fissionable. Pu is fissionable, as it undergoes fission in a fast neutron reactor — but it is not a fissile isotope. It is theoretically possible, but very unlikely, that some UK civil plutonium may have been transferred to the US and used in the US nuclear weapons programme before See also I.
Gurban and M. HV Henderickz, Plutonium: blessing or curse? Plutonium Updated April Over one-third of the energy produced in most nuclear power plants comes from plutonium. It is created in the reactor as a by-product. Plutonium recovered from reprocessing normal reactor fuel is recycled as mixed-oxide fuel MOX.
Plutonium has occurred naturally, but except for trace quantities it is not now found in the Earth's crust. There are several tonnes of plutonium in our biosphere, a legacy of atmospheric weapons testing in the s and s. Plutonium is a vital power source for deep space missions.
Plutonium and nuclear power Plutonium is formed in nuclear power reactors from uranium by neutron capture.
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