SELL
logical protection criteria which
ntal surveys is that the highest
small groups of any age should
ished by measuring the critical
I'D CRITICAL FOODS
in any establishment determines
1 the potential magnitude ofrisk.
Ticultural practices and dietary
the United Kingdom alone are
ed with a single broad dietary
of which are that about 75 per
3 of biological origin is usually
is particularly important in the
production it is of great signifialy of a localized community,
tom nearby farms, many other
amercial channels largely from
ized emergency, such as might
terials from a nuclear establishmilk will be enhancedrelative
Stances in food chains is now so
») that only a brief summary is
Fission Yield
RADIOACTIVITY IN AGRICULTURAL PRODUCTS
7
that cereals may sometimes deserve special concern, for example, if a
release occurs shortly before the crops mature. With the passage of time
strontium 90 may be present to some extent in all foods. However, if the
deposited material is in a finely divided freely soluble form, and thus
readily transferred to milk in the early period, the radiation doses then
received will appreciably exceed those caused subsequently by its presence
in other foods.
Caesium 137 is likely to be next in importance to the isotopes of iodine
and strontium, though to a considerably smaller extent.
B.
Fission Products Released from Nuclear Reactors
Because volatile nuclides are likely to escape into the environment
considerably more readily than other fission products, the significance of
iodine 131 relative to other nuclides is likely to be much enhanced and
possibly also that of caesium 137 though it is not likely to be of major
concern.
:
C.
Release of Other Radioactive Materials
At chemical separation plants it may be necessary to consider the possi-
bility that fission products not enumerated in the preceding sections, or
other radioactive materials, may deserve particular consideration. No
generalization can be made; each situation should be considered on its
own merit.
D.
Special Problems due to Sparingly Soluble Materials
In the preceding paragraphs it was assumed that the released radioactive
material is in a freely soluble form so that it can enter readily into food
chains. If, however, sparingly soluble materials are released, the maximum
radiation dose rates may occur only after the passage of an appreciable
period of time during which the material is rendered soluble in the soil.
ducts will be released in fission
This is important only with long-lived nuclides, for example, strontium 90.
In such cases it will be obviously desirable to obtain information on the
n the early period and, if the
ypen pastures, milk will be the
of the critical food by itself will not provide this information. Where this
£ point.
fed on fresh milk may receive
If deposition occurs during the
red food, the risk will be very
ther critical nuclides in mixed
‘ source of concern if the mean
ut 6 weeks and the release of
nuclear establishmentis highly
ical food, though it is possible
possible magnitude of risk in advance of its occurrence and the examination
type of situation is likely to occur it is therefore necessary to Measure not
only the critical food but also the total deposit on the ground surface.
E.
The Problem of Drinking Water
In view of the importance whichis rightly attached to the purity of water
supplies, it is worthy of note that the omission of any reference to drinking
water in this section is mot accidental. It is well established that when
radioactive substances have been released in the atmosphere the contami-
nation of water or aquatic produce makes only a very small contribution to
the total intake.