AEC Authorizing Legislation

It developed later that these apportioned dose values came

to be regarded as having greater significance than the ICRP originally intended and they gave the impression also that it would be acceptable to permit exposures to rise to these levels.

As a

result, ICRP's illustrative apportionment has now been deleted

(3)

from the Commission's latest recommendations, including indica-
tions of the magnitude of the main contributors to genetic dose
instead. This change should not be taken to mean that the ICRP
has abandoned the idea of genetic dose apportionment, but rather
that it has decided this is a matter best left to national author-

ities.

4.0 General Approach to Plowshare Guides

We tend to look upon Plowshare exposure situations, particularly those likely to result from nuclear excavations, as "transient" or transitory, in contrast to occupational exposure situations, although this will not always be the case as, for example, when radionuclides of long effective half lives are released during some Plowshare detonation and subsequently taken into the body. Hence, we define transient exposures, here, as exposures to external radiation and intakes of radionuclides resulting from the release of radioactive materials to the environment during and following some Plowshare event, and having

a duration, say, of a few minutes to a few hundred hours, which result in a radiation dose or dose commitment to man clearly attributable to the event in question. Our so-called transient exposure may produce a radiation dose or dose commitment in man via any one or all of the exposure pathways and exposure modes familiar to us from our experiences with exposures of longer duration, as from reactor effluents routinely discharged to the atmosphere or to some nearby body of water. However, the order of importance of various exposure pathways and exposure modes may be unique to Plowshare situations, although those encountered during and following a nuclear excavation may be similar in some respects to those following a reactor accident. It seems reasonable, therefore, to search for guidelines* specific for transient exposure situations that may be applied in either or both cases.

Our aim will be to derive a "Cumulative Exposure Index"* that is

We shall

as consistent as possible with the ICRP's official guides. follow the same general approach to the development of "CUE" values as the ICRP did in deriving its MPC values for air and water:

The only important difference in the search for CUE values will be the considerations and interpretations that relate primarily to

*We have adopted the term, "Cumulative Exposure Index" (CUE) for our Plowshare guides go avoid confusion with terms used by the ICRP and other recognized authorities to designate their official guides.

transience, as contrasted with the continuous, long-term (50 years)

exposures in the occupational exposure case:

MPD → MPBB → CUE!

In the first phase of our search for CUES, we shall limit our consideration to a relatively simple exposure situation, viz., the release of radioactive material to the atmosphere and the subsequent exposure of man by submersion in the "cloud" and inhalation of some of the airborne radioactivity. Here, we are dealing with one exposure pathway (airborne radioactivity), and two exposure modes: submersion resulting in an external dose and inhalation producing an internal dose or dose commitment. This is an exposure situation one would expect

to encounter "close in" or "shortly after" a nuclear excavation detonation. The radiation doses or dose commitments to be expected from these exposure modes can be estimated from a knowledge of radionuclide concentration in the cloud and the time interval during which submersion and inhalation take place, along with certain physiological and biological parameters characterizing the individuals exposed.

Other exposure pathways and exposure modes will be considered

later (e.g., external exposure to contaminated land surface, external exposure due to submersion in contaminated water, and internal exposures resulting from the ingestion of contaminated food and water), but these must await a fuller understanding of how CUES relate to relatively

simple pathways before we proceed to internal exposure situations involving complex food-chain pathways.

Guideline Format

The form chosen for the expression of our transient exposure guides (CUES) is rather important. The CUES will be of little value unless they are in a form which is readily understood and easily measured. More importantly, they must facilitate the interpretation of air monitoring data in some plausible relation to the basic standards for permissible dose and/or permissible organ burden. Such interpretations will then support judgments concerning the need for protective actions, or the testing of compliance with regulations governing environmental releases which have the same basis.

In the case of inhalation exposure, total intake is a function of both radionuclide concentration in the inhaled air and the duration

of intake. This suggests use of an exposure "index" with units of

concentration (μ Ci/cm3) and time (minutes or hours). Similarly, in

the case of external exposure due to submersion in the radioactive "cloud" or in contaminated air, the resulting dose delivered externally to the body is both a function of radionuclide concentration in air and the time interval during which the individual is submersed. Therefore, our "cumulative exposure index" (CUE) should be expressed in unites of Ci - hours/cm3.

5.0 Calculation of CUE

Two methods of calculating CUE values are presented here: (1) a method which limits both the annual dose and the corresponding organ burden; and (2) one which limits the annual dose only.

Our intent is

to provide a range of CUE values by both methods of calculation, from which we can select the most conservative or restrictive values for