What are the objectives and basic principles of radiation protection?

Objectives of radiation protection

The objectives of radiation protection are to minimize the health effects due to radiation. Before formulating the appropriate countermeasures, we have to understand the biological effects of ionizing radiation.

Biological effects of radiation are mainly classified into "Tissue Reactions (Deterministic effects)" and "Stochastic effects". For the former, a threshold level of absorbed dose exists, above which the radiation will bring detrimental effect to the health. For the stochastic effect, a threshold does not exist, but the probability of having detrimental effect is proportional to the dose absorbed.

Based on the characteristics of the above biological effects, aims of radiation protection are to:

1. avoid the deterministic effects; and
2. lower the probability of stochastic effects to an acceptable level.

Principles of radiation protection

Any practice resulting in increased exposure to radiation should be carefully planned in accordance with the three basic radiological protective principles as set out by the International Commission on Radiological Protection (ICRP) in 1991 (ICRP Publication No. 60). These basic principles are:

1. Justification of a practice - any practice involving exposure should be justifiable, i.e. it produces more benefit to the exposed individual or society than harm;
2. Optimisation of protection - the magnitude of individual doses and the number of people exposed should be kept as low as reasonably achievable, economic and social factor being taken into account; and
3. Individual dose limits - the exposure of individuals will be subjected to dose limits to ensure that no individual is exposed to radiation risks that are judged to be unacceptable.

In the unlikely event of a nuclear accident resulting in an increase of environmental radiation level, both ICRP Publication No. 60 and No. 63 recommended implementation of interventions i.e. human activities to reduce the overall exposure by altering the existing causes of exposure. The basic principles for intervention are:

1. Justification - the proposed intervention should do more good than harm, i.e. the reduction in detriment resulting from the reduction in dose should be sufficient to justify the harm and the costs, including social costs, of the intervention.
2. Optimisation - the form, scale, and duration of the intervention should be optimized so that the net benefit of the reduction of dose, i.e. the benefit of the reduction in radiation detriment, less the detriment associated with the intervention, should be maximised.