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J. A. Reissland et al.
In section 2 we describe the model we have used to represent a work force of
raciation workers and the way in which we have estimated their chances of
dying from an induced cancer. Section 3 discusses the time necessary to
achieve sufficient data to be able to draw conclusions with some specified level
of confidence. We also consider the magnitude of risk that is detectable in a
given time.
Results of calculations are presented and discussedin section 4 and we make
comments on possible conclusions in the final section.
2.
The model
There are three aspects to be settled before any calculations can be carried
out:
(i) the age distribution of the work force and the rate at which workers leave,
(ii) the natural incidence of deaths from causes which may also be induced by
radiation, and
(iii) the risk of death due to exposure to radiation and howthis risk is distributed in time.
2.1. Lhe work force
Our calculations refer to a work force of 100000 distributed in age as shown
in fig, 1. This distribution is based on the actual distribution at an established
nuclear energy site ancl does not differ greatly from any typical British industry.
We have assumed for simplicity that the annual percentage Jeaving radiation
work other than by death or retirement is the same for cvery age group.
Stability of the distribution is maintained by introducing new workers (with no
previous industrial radiation exposure) to replace those leaving any group by
death, resignation or retirement. ‘The total number of ex-radiation workers is
dependent on the leaving rate. Irom the records of the National Radiclogical
Protection Board (NRPB) and from informai discussions with employers, we
have arrived ab a figure of between 8 and 10%for the annual percentage of
workers who cease radiation work other than by death or retirement. We have
considered 5 and 10%which, understeady state conditions, lead respectively to
171000 and 330000 living ex-workers. We have assumed also that those
leaving radiation work do not return to ib within the latent period of risk
following their last exposure.
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Wig. 1. he age distribution of the work foree used throughout this paper.