From these ICRP recommendations the AEC has set regulatory limits for the United States. These are derived from Federal Radiation Council interpretations of ICRP values.

These are set for radioactive levels due to normal nuclear plant operation and for operational transients which might be expected to occur and also for radioactive levels following accident situations. These two sets of regulatory limits are embodied in Section 10 of the Code of Federal Regula­tions (8), Part 20 and Part 100, respectively,+

a. 10 CFR 20. This limits the exposure of individuals to radiation in restricted areas during normal operation of the plant.

(1) For the whole body, head and trunk, active blood forming organs, lenses of the eyes, and gonads: 1.25 rem/quarter.

(2) For the hands and forearms, feet and ankles: 18.75 rem/quarter.

(3) For the skin of the whole body: 7.5 rem/quarter.

A greater exposure than this may be incurred only if:

(1) During any calendar quarter the dose to the whole body does not exceed 3 rem; and

(2) the dose to the whole body when accumulated does not exceed 5(N — 18), where N is the age of the individual.

+ See Note added in proof on p. 325.

b. 10 CFR 100. This limits the exposure of individuals to radiation follow­ing an accident. The site will have two boundaries inside which lie an exclu­sion area and a low population zone, respectively. These boundaries are detailed in Section 5.2.1. The Federal regulations limit radioactivity at these boundaries in the following way.

(1) Whole body dose to an individual at the boundary of the exclusion zone during the two hours following the incident shall not exceed 25 rem.

(2) The thyroid dose at the same point shall not exceed 300 rem.

(3) The whole body dose to an individual located at the boundary of the low population zone during the whole passage of the cloud (assumed to be 30 days) shall not exceed 25 rem.

(4) The thyroid dose at the same point shall not exceed 300 rem.

(5) A distance limitation is set around the plant so that population centers of more than 25,000 persons are not involved (see Section 5.2.1).

The fast reactor contains plutonium and the 10 CFR 100 accident limits do not yet provide limits for ingested plutonium. In fact plutonium is an extremely long-lived (120-yr half-life)+ bone seeker so that any ingested plutonium will give the individual a continuous dose throughout his life­time. At present, limits of plutonium release are governed by ICRP limits on radiation exposures to the general public of 1.5 mrem/yr (9). Assuming a 50-year lifetime, and that ingested plutonium stays with the carrier for life, then a total of 75 mrem in any one exposure would seem an upper limit. The AEC has yet to set such a regulatory limit for plutonium.

The 10 CFR 20 limits are essentially the ICRP ones slightly undercut by taking the maximum annual permissible dose levels and dividing by four for the quarter’s dose. The 10 CFR 100 doses are higher than these because of the much lower probability, and therefore frequency, of occurrence.

These limitations are, as following sections will show, met by the contain­ment design bases with considerable safety margin. However, actual plant releases prove, in practice, to be as much as two orders of magnitude lower than even the design values for operational releases. Accidental releases have been insignificant.