CHAPTER 4
ENVIRONMENTAL STUDIES
4.1
CHEMICAL AND PHYSICAL CHARACTERISTICS OF THE FALLOUT MATERIAL
The fallout material consisted largely of calcium carbonate and calcium oxide particles.
The fission products were adsorbed mainly on the smaller particles. The fallout material was
found to be 10 per cent water soluble and almost completely soluble in acid. An extensive
physical and radiochemical analysis of the fallout material, and determination of its gamma
and beta spectrum, was performed by the Chemical Technology and Nucleonics Division of the
NRDLand will be issued as separate reports.
4.2
4.2.1
RADIOCHEMICAL ANALYSIS OF FOODSTUFFS, WATER,AND SOIL
Methods
Radiochemical analyses of the food, water, and soil samples reported here were performed
by the Chemical Technology Division of the NRDL. Additional analyses were made by NYOOAEC and the NMRI. Since a complete radiochemical analysis of all biological samples was not
feasible, only Sr*®, Ba!“ fissile material, and the rare-earth groups were measured in addition to the total beta activity. These measurements were found to be the most useful for determining the nature of the contamination.
Theinitial external activity of the samples, as detected with a rapid survey instrument
(1M-57/PDR~27 Radiac meter), is listed in Table 4.1. The values are given in milliroentgens
per hour at surface contact unless otherwise stated. For the food plants with large surface
areas, a range of activities is given.
A moreaccurate estimate of the activity of environmental samples was obtained by using
a 47 gammaionization chamber. A number of samples were first evaporated to dryness and
wet ashed with fuming nitric acid. The residues were made up to volume in HCl, and an aliquot
evaporated to dryness for beta-activity determination. The samples were then counted with a
proportional counter, with appropriate corrections made for mass absorption, backscatter, and
geometry of the counter. The disintegration rate determined was plotted against millivolt
reading of the ionization chamber for the samples. This ratio was then used to convert the
gammaionization chamber readings into disintegrations per minute.
The values obtained in this mannerarelisted in Tables 4.2, 4.3, and 4.4, discussed below.
An empirically derived ratio of alpha activity to ionization chamber reading was also obtained
on a number of samples. An estimate of the alpha activity of the remaining samples was then
obtained by applying this ratio.
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