910 J. cl. Reissland et al. force but with no mitial exposure and no ex-workers with radiation exposure. ‘The steady state exposure pattern and ex-worker distribution is built wp by calculating the annual number of radiation deaths for each year up to 50 years. The results are summarized in fig. 3 and table 4. 1-0 a oe AM eg 0-8 _ x13 zl /. ae 0-6 i ME [4i/ 0-4 of 0 Wig. 3. [er oo af if / 5 0 1 The growth to steady state. 20 25 30 35 40 4&5 56 Time ,/ lyears) Curve I represents the growth of the number of ex-workers with radiation exposure. Curve Il is the growth of the expected miumber of radiation-induced cancer deaths among in-service workers and curve I] mmonge ox-workers. N(é) is the nuniber in year é and N (co) the mamberin tho steady stale as in tablo 2, coluinn A. ‘Table 4. Showing the accumulated numberof radiation-induced deaths in 5-year intervals following time zcro when radiation exposure becan. Also shownis the number of people involved for our standard 100000 workers exposed to 1 rad} year cach and for 3000 workers exposed to $radfycar cach Time (years) 10 15 20 25 30 159 $61 175 749 197 543 216 279 231 905 Lb 7 35 47 103 4526 5272 5 926 G 488 G 957 0-06 0-235 0-57 1-0 1-5 Working population 100 000 (1 rad/year) Volal workers IM -|- eX Accuinulated tu deaths Agg Working population 3000 (4 vrad/ycar) ‘Ratal workers IN + EN Aecumulated rt deaths Ay 3. Observation time ‘3.1. Pane required for a survey We are interested in an estimate of the number of years over which cancer deaths among radiation workers must be observed to show a significant difference between them and a corresponding group of non-radiation workers.