Nuclear waste products

Evidence gathered in 1997 at the Hanford facility for nuclear waste storage shows some leaking into the surrounding soil. On the other hand, the most potent nuclear waste products (plutonium, cesium, and strontium) do not move far (they become adsorbed on soil), although technetium (with a half-life of 250,000 years) has reached the water table. 

The stabilization of the nuclear waste products is usually performed by immobilizing the oxides of the radioactive material in glass. This process is known as vitrification. The environmental aspects of storing large quantities of radioactive glass logs are related to the leachability of the elements from the glass structure. 

Now imagine the problem with nuclear waste. We cannot alter the rate at which it decays. This is defined by the half-life. We can t heat it, stir it, or add a catalyst to speed up the process as we can with chemical reactions. Furthermore, the half-lives of many nuclear waste products are very long plutonium, for example, has a half-life in excess of 24,000 years. Ten half-hves are required for the radioactivity of a substance to reach background levels. So we are talking about a very long storage time. 

But, in this chapter, I do discuss the nucleus and the changes it can undergo. I talk about radioactivity and the different ways an atom can decay. I discuss half-lives and show you why they are important in the storage of nuclear waste products. I also discuss nuclear fission in terms of bombs, power plants, and the hope that nuclear fusion holds for mankind. 

Nuclear wastes are classified according to the level of radioactivity. Low level wastes (LLW) from reactors arise primarily from the cooling water, either because of leakage from fuel or activation of impurities by neutron absorption. Most LLW will be disposed of in near-surface faciHties at various locations around the United States. Mixed wastes are those having both a ha2ardous and a radioactive component. Transuranic (TRU) waste containing plutonium comes from chemical processes related to nuclear weapons production. These are to be placed in underground salt deposits in New Mexico (see... 

Transuranic Waste. Transuranic wastes (TRU) contain significant amounts (>3,700 Bq/g (100 nCi/g)) of plutonium. These wastes have accumulated from nuclear weapons production at sites such as Rocky Flats, Colorado. Experimental test of TRU disposal is planned for the Waste Isolation Pilot Plant (WIPP) site near Carlsbad, New Mexico. The geologic medium is rock salt, which has the abiUty to flow under pressure around waste containers, thus sealing them from water. Studies center on the stabiUty of stmctures and effects of small amounts of water within the repository. 

Nuclear Waste Reprocessing. Liquid waste remaining from processing of spent reactor fuel for military plutonium production is typically acidic and contains substantial transuranic residues. The cleanup of such waste in 1996 is a higher priority than military plutonium processing. Cleanup requires removal of long-Hved actinides from nitric or hydrochloric acid solutions. The transuranium extraction (Tmex) process has been developed for... 

Nuclear power production involves bringing fissionable material together to react nuclearly, removing the heat, converting the heat to steam to drive a turbogenerator. and managing the wastes. 

The main drawback to nuclear power is the production of radioactive waste. Spent fuel from a nuclear reactor is considered a high-level radioactive waste, and remains radioactive for a veiy long time. Spent fuel consists of fission products from the U-235 and Pu-239 fission process, and also from unspent U-238, Pu-240, and other heavy metals produced during the fuel cycle. That is why special programs exist for the handling and disposal of nuclear waste. 

In 1976 the Swedish government stipulated that no new nuclear reactors should be charged until it had been shown how the radioactive waste products could be taken care of in an "absolutely safe manner" (8). Consequently, the nuclear power industry (through their joint Nuclear Fuel Supply Co, SKBF) embarked on a program referred to as the Nuclear Fuel Safety (KBS) Project (8). In one of the schemes (9) a repository for spent nuclear fuel elements in envisaged at a depth of 500 m in granitic bedrock. The repository will ultimately contain 6000 tonnes of uranium and 45 tonnes of plutonium. The spent fuel elements will be stored in copper cylinders (0.8 m in diameter and 4.7 m in length) with a wall thickness of 200 mm the void will be filled with lead. 

A general conclusion from the review of the distribution of plutonium between different compartments of the ecosystem was that the enrichment of plutonium from water to food was fairly well compensated for by man s metabolic discrimination against plutonium. Therefore, under the conditions described above, it may be concluded that plutonium from a nuclear waste repository in deep granite bedrock is not likely to reach man in concentrations exceeding permissible levels. However, considering the uncertainties in the input equilibrium constants, the site-specific Kd-values and the very approximate transport equation, the effects of the decay products, etc. — as well as the crude assumptions in the above example — extensive research efforts are needed before the safety of a nuclear waste repository can be scientifically proven. 

Chemistry is the key to the safe use of nuclear power. It is used in the preparation of the fuel itself, the recovery of important fission products, and the safe disposal or utilization of nuclear waste. 

There is some dispute among analysts as to whether world production of conventional oil will peak before the year 2020 or whether the peak will be delayed by another decade or two (Kerr, 1998), but in either case the current era of relatively cheap oil will end within several decades. A similar scenario is likely to follow for natural gas, although at a slower pace, and at a still slower pace, for coal. If our responsibilities to future generations include the relatively small problems that nuclear waste repositories may create in 10,000 years, they also include preparing for fossil fuel scarcity that will occur very much sooner. 

Learn how to concentrate and securely deal with the radioactive waste products from nuclear energy plants. 

Nuclear explosions and nuclear power production are the major sources of anthropogenic activity in the environment. But radionuclide use in medicine, industry, agriculture, education, and production and transport, use, and disposal from these activities present opportunities for wastes to enter the environment (Whicker and Schultz 1982a Table 32.6). Radiation was used as early as... 

Nuclear reactors are useful in the production of electricity, but they are not without their problems. These problems include disposal of nuclear wastes, accidents, and sabotage. The eventual answer may lie in nuclear fusion. 

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