 |
Business | Industries | Finance | Tax |
| Index: > A B C D E F G H I J K L M N O P Q R S T U V W X Y Z |
|
|||||
| First Prev [ 1 2 3 ] Next Last |
The radioactivity of all nuclear waste diminishes with time. All radioisotopes contained in the waste have a half-life - the time it takes for any radionuclide to lose half of its radioactivity. Eventually all waste decays into non-radioactive elements.
The faster a radioisotope is decaying, the more radioactive it will be. Another factor in deciding how dangerous a pure radioactive substance will be is the energy of the radiation. Some decays yield more energy than others. This is further complicated by the fact that few radioisotopes decay immediately to a stable state, but rather to a radioactive decay product leading to decay chains.
The main objective in managing and disposing of radioactive (or other) waste is to protect people and the environment. This means isolating or diluting the waste so that the rate or concentration of any radionuclides returned to the biosphere is harmless. To achieve this for the more dangerous wastes, the preferred technology to date has been deep and secure burial. Transmutation, long-term retrievable storage, and removal to space have also been suggested.
Low level Waste (LLW) is generated from hospitals and industry, as well as the nuclear fuel cycle. It comprises paper, rags, tools, clothing, filters etc which contain small amounts of mostly short-lived radioactivity. It does not require shielding during handling and transport and is suitable for shallow land burial. To reduce its volume, it is often compacted or incinerated before disposal.
Intermediate level Waste (ILW) contains higher amounts of radioactivity and some requires shielding. It typically comprises resins, chemical sludges and metal fuel cladding, as well as contaminated materials from reactor decommissioning. It may be solidified in concrete or bitumen for disposal. Generally short lived waste (mainly from reactors) is buried in a shallow repository, while long lived waste (from fuel reprocessing) will be disposed of deep underground.
High level Waste (HLW) arises from the use of uranium fuel in a nuclear reactor and nuclear weapons processing. It contains the fission products and transuranic elements generated in the reactor core. It is highly radioactive and hot. It can be considered the "ash" from "burning" uranium. HLW accounts for over 95% of the total radioactivity produced in the process of nuclear electricity generation.
Transuranic Waste arises mainly from weapons production, and consists of clothing, tools, rags, residues, debris and other such items contaminated with small amounts of radioactive elements -- mostly plutonium. These elements have an atomic number greater than uranium -- thus transuranic (beyond uranium). Because of the long half-lives of these elements, this waste is not disposed of as either low level or intermediate level waste. It does not have the very high radioactivity of high level waste, nor its high heat generation. The United States currently permanently disposes of transuranic waste at the Waste Isolation Pilot PlantThe Waste Isolation Pilot Plant or WIPP is an underground repository, that handles the permanent and safe disposal of transuranic radioactive waste that is left from the production of nuclear weapons. It is located near Carlsbad, New Mexico. Waste is plac.
Uranium oxide concentrate from mining is not significantly radioactive - barely more so than the granite used in buildings. It is refined to form yellowcake (U3O8), then converted to uranium hexafluoride gas (UF6). As a gas, it undergoes enrichment to increase the U-235 content from 0.7% to about 3.5%. It is then turned into a hard ceramic oxide (UO2) for assembly as reactor fuel elements.
The main by-product of enrichmentIsotope separation is the process of concentrating specific isotopes of a chemical element by removing other isotopes. While in general chemical elements can be purified through chemical processes, isotopes of the same element have nearly identical chemic is depleted uraniumDepleted uranium DU is uranium which contains a reduced proportion of the fissile isotope U-235 and (usually) the highly radioactive but rare isotope U-234, compared to natural uranium. Like natural uranium, it is almost entirely composed of U-238. During, principally the U-238 isotope, which is stored, either as UF6 or as U3O8. Some is used in applications where its extremely high density makes it valuable, such as the keels of yachts, and anti-tankAnti-tank or simply AT refers to any method of combating military armored fighting vehicles, notably tanks. The most common forms of anti-tank systems are cannons with a high muzzle velocity, wire guided missiles in various forms, and various autocannon f shells. It is also used (with recycled plutonium) for making mixed oxide fuelMixed Oxide or MOX fuel is an alternate to lightly enriched uranium fuel in the light water reactors which predominate nuclear power generation. Mixed oxide fuel is a blend of plutonium-239 into natural or depleted uranium which behaves similarly (though and to dilute highly enriched uranium from weapons stockpiles which is now being redirected to become reactor fuel. This dilution means that any nation or group that acquired the finished fuel would have to repeat the (very expensive and complex) enrichment process before assembling a weapon.
| Politics | Business | Finance |
 |
 |
 |
|