Radioactivity and Radiation
Radioactivity is both natural and man-made. The decay process gives radiation in the form of alpha particles, beta particles, and gamma rays. We all are exposed to natural background radiation from cosmic rays and minerals in the ground. Radon is an important source of exposure.
Radiation can be harmful to the body and to genes. Several methods of protection are available, including time, distance and shielding.
Radioactive Wastes
In nuclear plants the fission process yields energy that is converted to electricity. At the same time it generates wastes in the form of radioactive fission products and activation products. It is difficult and expensive to destroy wastes.
There is a large volume of defense waste, stemming from wars, and weapon production. Its disposal is yet to be completed, and a massive cleanup of facilities will be required. Low-level radioactive waste comes from nuclear reactors, industry, and health-related institutions. The most radioactive of the wastes to be disposed of is spent fuel from nuclear power reactors. It will accumulate at reactors in water pools or dry storage containers until a repository is built.
(p. 176)
Waste Management
Research and development on the waste disposal process will continue. Plans for disposal set by Congress are to be carried out by the Department of Energy for spent fuel, and by the sates for low-level waste. Decisions must be made about what is best to do with plutonium and highly enriched uranium produced by the US and the former USSR during the Cold War.
To protect the public and future generations from harm due to radiation exposure, design goals are to isolate reactor wastes until they are no more dangerous than the ore from which nuclear fuel came, to keep the hazard as low as reasonably achievable, and to limit exposure to a small fraction of that due to normal background.
Waste management involves application of science and engineering, but also requires that the public participate in selecting disposal sites and technology. Adherence to regulations is vital to the success of any waste management project.
Disposal Methods
Several methods for disposing spent fuel have been studied, with the conclusion that geologic disposal in a mined cavity deep in the earth is preferable. Interstate compacts have been formed in the US to handle all aspects of low-level waste disposal. For low-level wastes several alternatives to shallow land burial are available. Examples: intermediate-depth disposal, mine-cavity disposal, earth-mounded concrete bunkers, shaft disposal, above-ground vault, and earth-mounded above ground vault.
(p.177)
A legal structure exists to manage wastes safely, including laws specifying policy, requirements, and schedule; environmental protection standards; and licensing and regulation by federal and state government.
Challenge:
It is a challenge for us to enhance the benefits, and reduce the risks in the applications of the nucleus. This will involve dedicated and sincere efforts by program leaders to provide accurate and complete information, to understand and response to concerns, and to establish meaningful dialog with those who are affected.
(p.178)
Biological Effects of Radiation
We are familiar with some forms of radiation in our daily life and activities: sunburn, visible light(both natural and artificial), microwave ovens, radio, television.... When high-speed particles such as alphas, betas, gammas, or neutrons strike living tissues, they slow down and stop. The energy of the particles is imparted to the biological cells as localized heat. Molecules of the cells are changed, atoms are converted to ions, or the atomic nuclei are displaced from their positions. The disruptive action caused by absorbed energy impairs human body cell functions. If the amount of radiation is very large, radiation sickness, genetic effects, or death may result.
The biological effect of radiation (dose or dosage)depends on the amount of energy absorbed, and on the type of radiation. Neutrons are about ten times as damaging as x-rays, gamma rays, or low-energy beta particles. Alpha particles are about 20 times as damaging. The dosage is expressed in rems. Low radiation levels are expressed in the millirem (mrem) as 1/1000 rem.
The average individual American's annual exposure is estimated to be 360 mrems, according to the National Council on Radiation Protection and Measurements Report No. 93, 1988. A single radiation dose of around 400 rems is fatal to half of those who receive it, while half will survive with some impairment of function.
There are two general classes of radiation effects: somatic (damage to body tissue), and genetic (hereditary characteristics). The main somatic effect is cancer (leukemia or tumors), and genetic effects involve transmitted abnormalities of early death.
(Chapter 5, pp.20-22)
Source:
Raymond L. Murray. Understanding Radioactive Waste (Columbus, OH: 1994), 4th ed. Edited by Judith A. Powell.
Raymond L. Murray is Professor Emeritus in the Nuclear Engineering Department, North Carolina State University, Raleigh, NC.
Judith A. Powell
Battelle Pacific Northwest Laboratories
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