Answer to Question #8375 Submitted to "Ask the Experts"
The following question was answered by an expert in the appropriate field:
"Since it seems well established that there is no threshold dose for the production of gene mutations by radiation, it follows that strictly speaking there is no such thing as a tolerance dose when all possible effects of radiation on the individual and future generations are included."A 1957 change extended this nonthreshold concept to somatic effects of radiation, and it reemphasized the NCRP's "long-standing philosophy that radiation exposures from whatever sources should be as low as practical."
The 1954 edition of Handbook 59 "Permissible Dose from External Sources of Ionizing Radiation" has the following paragraph:
"The present report deals primarily with the protection of persons occupationally exposed to ionizing radiation from external sources. An attempt has been made to cover most of the situations encountered in practice. However, it has not always been possible to make recommendations in quantitative terms. In such cases, the recommendations are intended to serve as practical guides. The recommendations are based on presently available information and cannot be regarded as permanent. For this reason and on general grounds it is strongly recommended that exposure to radiation be kept at the lowest possible level in all cases."
It seems that early the philosophy was based on the dynamics of new and fast-changing recommendations of limits (tolerance versus permissible doses) and thresholds, as compared to it being based on the later linear no-threshold (LNT) theory.In an Atomic Energy Commission (AEC) (predecessor to NRC) Statement of Consideration (SOC) published 3 December 1970, 35 FR 18385, the proposed regulation addressed control of releases of radioactive material to the environment. This Statement indicates that on 1 April 1970, the AEC published in the Federal Register (35 FR 5414) a proposed amendment to Parts 20 and 50 which would, inter alia, improve the framework in 10 CFR Part 20 for assuring that reasonable efforts are made by all licensees to continue to keep exposure to radiation, and releases of radioactive effluents, as low as practicable. This philosophy, SOC continues, was based on the Federal Radiation Council's (FRC) recommendations. FRC was established around 1959, and the SOC mentions its Report No.1 dated 13 May 1960.
In addition, between 1975 and 1976, the term in 10 CFR 20.1(c) changed from "as far below the limits specified in this part as practicable" to "as low as reasonably achievable." It stated in 20.1.(c):
"In accordance with recommendations of the Federal Radiation Council, ... persons engaged activities under licenses issued by the NRC ... should, in addition to complying with the requirements set forth in this part, make every reasonable effort to maintain radiation exposures, and releases of radioactive materials in effluents to unrestricted area, as low as reasonably achievable."The next sentence goes on to expand for clarification that the concept considers the state of technology, economics of benefit versus risk, and other societal and socioeconomic considerations.
As for the last part of the question, ALARA is a general requirement for all NRC licensees, since Part 20 applies to all licensees, and therefore is applied in all NRC-licensed activities. All licensing organizations, such as other federal agencies and the states, also have it as a requirement. Application of the requirement, though, may not be uniformly stringent or equally visible in all industries, for a number of complex reasons.
The design objectives in Part 50, Appendix I, were issued in 1975, and these were based on application of the idea of ALARA. However, this application differs from what we now understand the term to mean because, at that time, the design criteria were selected by NRC staff after applying cost-benefit considerations and then using these considerations to formulate the final rule. The requirement to keep doses ALARA as a basis for radiation protection in general was as indicated above.
Cynthia G. Jones, PhD
Joseph DeCicco, CHP
Sami Sherbini, PhD