A Wiser Arrangement
by Ward A. Young
Nuclear wastes in the United States are currently classified more for the convenience of the nuclear industry than by level of radioactivity or duration of radioactive hazard. The Nuclear Regulatory Commission (NRC) puts all waste generated by a nuclear power plant into the catch-all "low-level" category except for the spent fuel rods, which are classed as "high-level." [see box below]
This distinction is arbitrary since some of the fission products in the "high-level" spent fuel leak out into the surrounding water and become part of the wastes that are classified as "low-level." In addition to fission products, cesium and strontium are "activation products," which are formed from the absorption of neutrons and are extremely long-lived. Even plutonium is included in the "low-level" category.
In a similar way, the Department of Energy (DOE) puts all waste generated by nuclear weapons production into the "low-level" category except for reprocessing wastes and transuranic wastes. Again the result is that substantial quantities of intensely radioactive and long-lived wastes end up dumped into the ground near the surface.
These highly active and extremely long-lived wastes should be excluded from the "low-level" waste category. Countries such as Sweden mandate their exclusion, but not the U.S. because the NRC and DOE regulate more for the convenience of the nuclear industry than for public health and environmental safety.
So-called "low-level" waste can be managed (i.e., disposed of) according to the most lax standards imaginable, saving the nuclear industry billions of dollars. All low-level waste dumps built to date are simple landfills (with somewhat more elaborate structures now on the drawing boards). These near-surface dumps are regulated for a maximum of 100 years following closure, while high-level waste is usually required to be buried in deep geological disposal, with isolation of the waste mandated for thousands of years.
The current radioactive waste classification system must be rewritten based on duration of radioactive hazard (which can be calculated from the half-life) and level of radioactivity, not where the waste comes from or happens to end up in the nuclear fuel cycle. [see "Storage for Decay" and "Medical Waste," page 12]
HOW THE US CATEGORIZES WASTE
Summarized by Ward A. Young
The NRC regulates waste from commercial use, and the DOE regulates waste from the military. The Environmental Protection Agency has set standards for high-level waste repositories but has yet to do so for low-level sites.
- High-Level Radioactive Wastes include both commercial irradiated fuel (spent fuel) and military reprocessing wastes.
- Transuranic Wastes are wastes contaminated with elements heavier (i.e., higher on the periodic table) than uranium and which today come primarily from the DOE's military production activities.
- Uranium Mill Tailings come from processing uranium ore and contain about 85 percent of the radioactivity of the original ore.
- Low-Level Radioactive Wastes are all wastes, commercial and military, not included in any of the above categories. NRC regulations further subdivide commercial low-level waste into four categories, Class A, B, C, and Greater-than-Class C, according to a combination of level of concentration and half-life of radioactivity.
- Mixed Wastes combine radioactive and hazardous wastes and are generated by DOE and civilian use.
Goals of Reclassification
To begin building a hazard-based classification system, we would use all we know about various attributes of radioactive materials that relate to any known hazard. Radioactive elements are those elements with an unstable nucleus that spontaneously releases energy (or decays) on its way to a more stable form. This energy can take the form of alpha and beta particles, neutrons, and gamma rays, and is known to be very destructive to cells.
Therefore, any way we have of measuring particles and the radionuclides that emit them can assist us in ascertaining hazard. For example, we can measure how many particles are emitted by a given amount of a radioactive element; how often they are emitted; type of particles; their energy levels; the behavior of any particular radionuclide in the body; and so on.
Factors related to hazard include physical half-life, radioactivity (disintegrations per second per unit volume), biological half-life (the time required for the body to eliminate half of a radioactive dose received), type and energy of decay particle, and the specific behavior in the human body.
Probably the single most important way to measure the hazard of radioactive wastes is the longevity or half-life of the radioactive elements making up the waste. The principle difficulties of managing radioactive waste relate to the ability or lack thereof to assure long-term containment. When radioactive materials are present in substantial quantities, the danger can be said to persist for 10 to 20 half-lives. After 10 half-lives the material will have decayed one thousand-fold, and after 20 half-lives, a million-fold. What are the implications? The goal in managing radioactive wastes must be to isolate radioactive material from the environment for its entire hazardous life. In addition, all unnecessary exposures should be avoided.
Current regulations encourage generators to dilute waste to circumvent concentration limits or avoid stricter management requirements. On the contrary, long-lived radionuclides should be concentrated as much as possible, so that as much of the long-lived material can be included in the strictest long-term management option.
Probably the second most compelling measure of hazard of radioactive waste is its radioactivity. If the waste is highly concentrated in its radioactivity, or "hot," it requires shielding and cooling during handling and storage. If it is less concentrated, remote handling may not be necessary.
As we have seen, current standards for the various "low-level" waste classes allow for certain amounts of many very long-lived radionuclides. Using this limit, "low-level" dumps are allowed to accept a few hundred pounds of plutonium in total. Ideally, with plenty of citizen decision-making, concentration limits would be set more strictly for each radionuclide, and a large portion of wastes would be reclassified as intermediate or high-level.
A third measure of hazard is the type of decay particle that comes from the radioactive element. Alpha particles and neutron radiation are more effective in causing disease and other damage than beta or gamma radiation. Currently the International Commission of Radiological Protection recommends that alpha radiation should be considered 20 times more effective and neutron radiation six to 20 times as effective in causing diseases as beta and gamma radiation.
The first set of guidelines for a new classification policy would thus include:
- All wastes containing significant amounts of long-lived radionuclides should be isolated from the environment according to the most stringent long-term management option.
- Radionuclides should be segregated according to half-life.
- Radioactive waste should also be classified by level of radioactivity (as in Sweden, where low, intermediate and high-level categories require different levels of cooling and shielding necessary).
Public health and environmental safety should be the main concerns of any policy.
Ward A. Young has a degree in conservation of natural resources and is an educator and farmer. For six years he was editor of California's disarmament newspaper It's About Times.
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