Who has tad who mines uranium?

Uranium is widespread in many rocks, and even in seawater. However, like other metals* it is seldom sufficiently concentrated to be economically recoverable. Where it is, we speak of an orebody. In defining what ore is, assumptions are made about the cost of mining and the market price of the metal. Uranium reserves are therefore calculated as tones recoverable up to a certain cost Although it has more than any other country, Australia is not the only one with major deposits. Others in order are: Kazakhstan (15% of world total), Canada, South Africa, Namibia, Brazil, Russia and USA (3%). Many more countries have smaller deposits which could be mined if needed. Uranium is sold only to countries which are signatories of the Nuclear Non-Proliferation Treaty, and which allow international inspection to verify that it is used only for peaceful purposes. Customer countries for Australia's uranium must also have a bilateral safeguards agree­ment with Australia. Canada has similar arrangements.

Other uses of nuclear energy

Many people, when talking about nuclear energy, have only nuclear reactors (or perhaps nuclear weapons) in mind. Few people realize the extent to which the use of radioisotopes has changed our lives over the last few decades.

Radioisotopes

In our daily life we need food, water and good health. Today, radioactive isotopes play an important part in the technologies that provide us with all three. They are pro­duced by bombarding small amounts of particular elements with neutrons.

In medicine, radioisotopes are widely used for diagnosis and research. Radioactive chemical tracers emit gamma radiation which provides diagnostic information about a person's anatomy and the functioning of specific organs. Radiotherapy also employs radioisotopes in the treatment of some illnesses, such as cancer. More powerful gamma sources are used to sterilize syringes, bandages and other medical equipment. About one in two Australians is likely to experience the benefits of nuclear medicine in their lifetime, and gamma sterilization of equipment is almost universal.

In the preservation of food, radioisotopes are used to inhibit the sprouting of root crops after harvesting, to kill parasites and pests, and to control the ripening of stored fruit and vegetables. Irradiated foodstuffs are accepted by world and national health authorities for human consumption in an increasing number of countries. They include potatoes, onions, dried and fresh fruits, grain and grain products, poultry and some fish. Some prepacked foods can also be irradiated.

In the growing crops and breeding livestock, radioisotopes also play an important rote. They are used to produce high yielding, disease and weather resistant varieties of crops, to study how fertilizers and insecticides work, and to improve the productivity health of domestic animals.

Industrially, and in mining, they are used to examine welds, to detect leaks, to study the rate of wear of metals, and for on-stream analysis of a wide range of minerals and fuels.

There are many other uses. A radioisotope derived from the plutonium formed in nuclear reactors is used in most household smoke detectors.

Radioisotopes are used by police to fight crime, in detecting and analyzing pollut­ants in the environment, to study the movement of surface water and to measure water runoffs from rain and snow, as well as the flow rates of streams and rivers.

Other reactors

There are also other uses for reactors. Over 200 small nuclear reactors power some 150 ships, mostly submarines, but ranging from icebreakers to aircraft carriers. These can stay at sea for long periods without having to make refueling stops. The wordless first nuclear powered container ship was built in Russia. The heat produced by nuclear reactors can also be used directly rather than for generating electricity. In Sweden and Russia, for example, it is used to heat buildings and to provide heat for a variety of in­dustrial processes such as water desalination.

Military weapons

Both uranium and plutonium were used to make bombs before they became impor­tant for making electricity and radioisotopes. But the type of uranium and plutonium for bombs is different from that in a nuclear power plant. Bomb-grade uranium is highly-enriched (>90% U-235, instead of about 3.5%); bomb-grade plutonium is fairly pure (>90%) Pu-239 and is made in special reactors. Today, due to disarmament, a lot of military uranium is becoming available for electricity production. The military uranium is diluted about 25:1 with depleted uranium (mostly U-238) from the enrichment pro­cess before being used.

URANIUM ENRICHMENT

The uranium enriched in uranium-235 is required in commercial light water reac­tors to produce a controlled nuclear reaction. Several different processes are used to enrich uranium.

Enriching Uranium

Gaseous Diffusion

Gas Centrifuge

Enriching uranium increases the amount of "middle-weight⁵⁵ and "light-weight" uranium atoms. Not all uranium atoms are the same. When uranium is mined, it con­sists of heavy-weight atoms (about 99.3% of the mass), middle-weight atoms (0.7%), and light-weight atoms (< 0.01%). These are the different isotopes of uranium, which means that while they all contain 92 protons in the atom's center (which is what makes it uranium). The heavy-weight atoms contain 146 neutrons, the middle-weight contain 143 neutrons, and the light-weight have just 142 neutrons. To refer to these isotopes, scientists add the number of protons and neutrons and put the total after the name: ura-nium-234 or U-234, uranium-235 or U-235, and uranium-238 or U-238.

The fuel for nuclear reactors has to have a higher concentration of U-235 than exists in natural uranium ore. This is because U-235 is the key ingredient that starts a nuclear reaction and keeps it going. Normally, the amount of the U-235 isotope is enriched from 0.7% of the uranium mass to about 5%. Gaseous diffusion is the only process being used in the United States to commercially enrich uranium. Gas centrifuges can also be used to enrich uranium. Although this enrichment process is not used in the United States, the NRC is conducting licensing activities concerning two planned centrifuge facilities.

Gaseous Diffusion

Process: In the gaseous diffusion enrichment plant, the solid uranium hexafluoride (UF6) from the conversion process is heated in its container until it becomes a liq­uid. The container becomes pressurized as the solid melts and UF6 gas fills the top of the container. The UF6 gas is slowly fed into the plant's pipelines where it is pumped through special filters called barriers or porous membranes. The holes in the barriers are so small that there is barely enough room for the UF6 gas molecules to pass through. The isotope enrichment occurs when the lighter UF6 gas molecules (with the 13-23 and U-235 atoms) tend to diffuse faster through the barriers than the heavier UB6 j molecules containing U-238. One barrier isn't enough, though. It takes many hundreds of barriers, one after the other, before the UF6 gas contains enough uranium-235 used in reactors. At the end of the process, the enriched UF6 gas is withdrawn ft the pipelines and condensed back into a liquid that is poured into containers The UF6 is then allowed to cool and solidify before it is transported to fuel fabrication facilities where it is turned into fuel assemblies for nuclear power reactors.

Hazards: The primary hazards in gaseous diffusion plants include the chemical and radiological hazard of a UF6 release and the potential for mishandling the enriched uranium, which could create a criticality accident (inadvertent nuclear chain reaction).

Gas Centrifuge

The gas centrifuge uranium enrichment process uses a large number of rotating cylinders in series and parallel formations. Centrifuge machines are interconnected to form trains and cascades. In this process, UF6 gas is placed in a cylinder and rotated at a high speed. This rotation creates a strong centrifugal force so that the heavier gas molecules (containing U-238) move toward the outside of the cylinder and the lighter gas molecules (containing U-235) collect closer to the center. The stream that is slightly enriched in U-235 is withdrawn and fed into the next higher stage, while the slightly depleted stream is recycled back into the next lower stage. Significantly more U-23 enrichment can be obtained from a single unit gas centrifuge than from a single unit gaseous diffusion stage. No gas centrifuge commercial production plants are operating in the United States.

Fuel fabrication

Fuel fabrication facilities convert enriched UF6 into fuel for nuclear reactors. Fab­rication also can involve mixed oxide (MOX) fuel, which is a combination of uranium and plutonium components. NRC regulates several different types of nuclear fuel fab­rication operations.

Types of nuclear fuel fabrications are:

Light Water Reactor Low-Enriched Uranium Fuel

Reactor Mixed Oxide Fuel

Non-Power Reactor Fuel

Other Types of Fuel Fabrication