Nuclear Waste Has A Long History Of Confusing Definitions

Decades of legislation and court interpretations have left U.S. nuclear waste managers facing an intractable problem. Tasked with understanding science and skilled enough to work within constraints set by policy-makers, these managers sort various types of radioactive waste so they can be disposed of in accordance with the law. It’s a complicated job.

Now, waste management companies are urging the Nuclear Regulatory Commission (NRC) to take another look at the limitations of the current U.S. classification system and to possibly simplify it. This, in turn, raises questions about how the existing scheme works and how it compares with the international system.

“Waste classification is a really messy business to write about,” says Allen Croff, almost as soon as he answers a phone call from C&EN. Croff, now retired from Oak Ridge National Laboratory, led the National Council on Radiation Protection & Measurements (NCRP) in an effort to revamp the U.S. nuclear waste classification scheme more than a decade ago. But the U.S. government hasn’t adopted its recommendations.

The current classification system needs changing, the group concluded. NCRP called it “complex and not transparent to the public, who are increasingly involved in decisions about management and disposal of waste, and it is not understandable by anyone but a studied expert.”

Some of those waste classification experts work for NRC. Created by Congress in 1974, the commission regulates commercial nuclear waste and advises the Department of Energy on the management of DOE’s defense-related wastes, such as those from weapon production.

Commercial nuclear wastes are generally divided into high-level waste, low-level waste, and uranium mill waste. In addition to these, defense wastes also include a type of high-level material called waste incidental to reprocessing as well as transuranic waste, which is sometimes considered low-level waste depending on its radioactivity.

“The reason the system is so difficult to understand is because it has evolved based on qualitative definitions that are not intuitive,” Croff says. “The definitions that ended up in law are based on assumptions of what the nuclear enterprise would look like many decades ago, and those assumptions have not come to pass.”

In the U.S., all categories are defined in law based on the origin of the waste. For example, high-level waste is described as irradiated reactor fuel, highly radioactive material from reprocessing used nuclear fuel, and other high-level radioactive waste in the Nuclear Waste Policy Act of 1982.

Low-level waste, on the other hand, is defined by what it’s not. A 1985 law reserves the term low-level radioactive waste for material that is not high-level radioactive waste, spent nuclear fuel, or by-product material.

In its report, NCRP recommended that the U.S. set up three waste classes—exempt waste, low-hazard waste, and high-hazard waste. They would be based on chemical and physical properties of nuclear waste, including the type of radioactive decay and half-life. These considerations would affect the risk a particular waste poses to human health and the environment and would be used to determine the level of containment for storage or disposal, the council said.

The International Atomic Energy Agency (IAEA) has taken a similar approach to nuclear waste classification. Although the agency is not a regulatory body, it provides a set of generalized safety guidelines to governments that are intended to protect people and the environment, says Andrew Orrell, head of IAEA waste and environmental safety.

“Think in terms of safety,” Orrell says. “At the end, the requirements for protection are based on the potential radiological hazard the waste might pose to human health and the environment.”

IAEA has six categories for classifying waste that range from exempt waste to high-level waste and correspond to a recommended disposal path. The lowest class requiring radiation protection often is waste from the research and medical fields, and it can be disposed of as conventional waste once its radioactivity falls to an acceptable level for disposal in conventional landfills. The highest class contains short- and long-lived radionuclides that require disposal in an isolated, deep geological repository.

If the U.S. system for managing nuclear waste is confusing, that’s because the U.S. created the world’s first framework for sorting this material in all its varieties, Orrell says. Now long-standing laws and regulations governing this waste are intertwined and not easily undone, he adds.

But there’s a bright spot to that complex history.

“Other countries [that] are just beginning to have their very first research reactor have the luxury of a very simplified classification scheme,” the IAEA system, Orrell says. The U.S, which paved the way with nuclear technologies, has made it easier for countries with emerging nuclear energy programs to benefit from the experience, he says.