8
R, SCOTT RUSSELL
4.
ORGANIZATION OF SURVEY
It was suggested in the Introduction to this paper that the object of
continuing surveys in the environs of nuclear reactors is to satisfy both the
operators and statutory authorities that unacceptable quantities of radioactive materials have not been released; surveys in emergencies present
special, though technically simpler, problems which are not considered
here.
It is sometimes suggested that reactor site surveys should be expanded
above the minimum necessary for their primary purpose in the hope of
also obtaining scientific information on food chain mechanisms. While it
would be wrong to suggest that it is impossible to combine these two
objectives, the difficulty of doing so should be emphasized. It is unlikely
that important information on food chain mechanisms, or on the movement
of radioactive substancesin the soil, will be obtained unless the investigation
has been specifically designed for these purposes and elaborate methods
are employed; moreover,it is usually found that agricultural and meteorological information must also be assembled if interpretations are to be
adequate.
When the objective of a survey has been determined, it is important to
consider how the necessary information can be obtained with the minimum
expenditure of effort. The following suggestions, made with this aim in
mind, are directed to surveys the sole purpose of which is to ascertain
whether an unacceptable release has occurred:
A.
Information Necessary to Guide the Planning of Surveys
The appropriate starting point is an assessment of the mode of operation
of the establishment to ascertain firstly, what nuclides merit investigation,
secondly, at what distance from the establishment the maximum deposit
would be expected and, thirdly, the distance beyond which no appreciable
contamination can reasonably be expected. In this way “inner” and “outer”
sampling zones can be defined. A comparison of the levels of activity found
in them provides a basis for distinguishing the contamination due to the
operation of the plant from that which arises from world-wide fallout or
other causes. If an assessment of these matters leads to the conclusion
that any appreciable contamination would always be adequately detected
by monitoring equipment on the site it would be appropriate to consider
whether a continuing environmental survey were indeed necessary. It is
here assumed that this assessment leads to the conclusion that environmental levels of iodine 131 and strontium 90 should be examined.
Having defined the inner and outer sampling zones, the nature of agri-
cultural enterprises must be examined to reveal the sites at which critical
foods are produced. Local environmental factors which may influence the