Maximum Permissible Activity (MPA) for Fission Products in Air and Water

Abstract

When mixed fission products are present in air and water, the maximum permissible activity (MPA) is dependent on the relative activtty of the individual isotopes. This, in turn, is dependent on the age of the products. The MPA can be determined most accurately from measurements of the isotopic concentrations; however, the separation of mixed fission products into their constituent activities is extremely complicated and costly. In order to provide a simple method of evaluating the internal radiation hazard, MPA's for an ideal mixture of fission products vs. its age were calculated and plotted. The resulting curves show that the MPA's change appreciably with time. Between 1 day and 3 years for 40 hr per week occupational exposure, they decrease from 2.7 x 10/ sup -//sup 7/ to 1.2 x 10/sup -//sup 9/ mu c/cm/sup 3/ (microcuries per cubic centimeter) for air, and from 1.6 x 10/sup -//sup 3/ to 1.7 x 10/sup -//sup 5/ mu c/cm/sup 3/ for water. From the curves a first approximatton of the MPA-s and therefore the allowable fission product activity in air and water, can be obtained. In order to use the curves, one needs to know only the disintegration rate per unit volume andmore » the approximate age of the products. (auth)« less