Monitoring For Danger After Nuclear Accident

Press, Volume CII, Issue 30287, 13 November 1963, Page 19

Monitoring For Danger After Nuclear Accident

Maximum permissable levels of exposure to radioactivity from fission products deposited in the ground or present in food and water, after an accident leading to the contamination of a large area, were described yesterday to the annual meeting of the New Zealand Hospital Physicists’ Association by Mr J. F. McCahon, of the National Radiation Laboratory, Department of Health, Christchurch. Figures for continuous exposure published by the International Commission on Radiological Protection could not be directly applied in this connexion, he explained, because an accident was unlikely to be repeated. The commission’s figures for short-term exposure were based on accidents to individuals or a small fraction of the community, or to a desperate situation where immediate survival was the only criterion; either case was different from that he was considering. Taking as a basis the commission’s recommended maximum permissible exposure, cumulative over a long period, for a large population, Mr McCahon derived three levels of increasing danger from radioactivity in the surroundings, and three corresponding levels in the food supply. With general contamination of the ground and environment, the lowest level was a warning level calling for increased monitoring so that changes would be detected quickly. The second level necessitated immediate action, and the third level radical action.

With contamination of food supplies, the lowest level was again set to give a warning. Minor action might be taken and the sampling programme intensified. The second level

would require action which should be deflnite even though not immediate or imperative. Protective procedures were necessary but should not seriously disrupt the normal lives of the population. At the third level, evacuation would be indicated or the provision of uncontaminated food and water.