WASHINGTON — The Nuclear Regulatory Commission, citing improved knowledge of radiation's health effects, has proposed the first major revision in its radiation exposure limits in nearly 30 years.
The proposals primarily would affect nuclear industry workers by lowering occupational exposure levels for some radioactive materials, such as uranium, commonly used in nuclear fuel facilities.
But exposure limits for the average American would stay at the same level as before--roughly one-tenth of the allowable exposure for a nuclear industry worker.
Experts estimate that the average American receives 100 millirems of radiation exposure from radioactive elements that occur naturally in the environment, such as radon gas released from underground uranium deposits.
The proposed changes, updating radiation protection standards first issued by the agency in 1957, would apply to all activities regulated by the NRC, including nuclear power plants and nuclear fuel fabrication plants.
An NRC-licensed operation would face penalties if it emitted radiation exposing an average American to more than 500 millirems a year. A facility would have to report any exposure greater than 100 millirems incurred by an average person.
A nuclear industry worker would have a total whole body exposure limit of 5,000 millirems a year, the same as under the previous regulations.
However, the NRC said improved understanding of radiation's health effects and modern computer technology enable experts to set more accurate limits for individual body organs such as the lung, breast and gonads, among others.
Individual Body Parts
As a result, separate exposure limits for some body parts, such as external radiation to hands and feet, would be tightened. Exposure limits would be relaxed in other cases, such as radioactive elements absorbed by many internal organs.
In addition, NRC experts say improved knowledge led them to reduce occupational air concentration limits for some radioactive materials, including uranium. Limits for uranium would be reduced by 80% under the new regulations.
"Certain types of radioactive material are more efficient in causing cancer than previously thought," said Robert Alexander of the NRC's Division of Radiation Programs and Earth Sciences.
"Also, we have learned some chemical compounds remain in the lung and body longer than previously thought," he said.
Small Decreases Seen
An NRC notice in the Federal Register said that, because of the new regulations, "some small decreases are expected in the number of workers exposed at the higher levels and in the doses received by those workers engaged in milling and fabrication of uranium fuel."
The proposed regulations, subject for public comment until April 21, would also:
--Eliminate "dose-averaging" provisions that previously allowed workers to exceed yearly radiation limits as long as their lifetime exposure limit was not exceeded. In its place, the NRC would approve, on an individual basis, "special exposure" activities that might result in higher-than-permissible yearly doses.
--Establish lower radiation limits for women working in the nuclear industry who voluntarily notify their employers that they are pregnant.