Practical experience has shown that the efficiency of radioactive waste management is greatly improved if the system of waste classification is aligned with the proposed method of disposal. Because near-surface disposal is reserved for short­lived waste (half-life less than about 30 years), this requires that the system should reflect the half-life of the radionuclides in the waste. The classification scheme recommended by the IAEA5 follows this model (illustrated schematically in Fig. 18.1) with six specific categories, as briefly described in Table 18.1.

Table 18.1 Brief description of the various waste categories in the IAEA scheme

Category Description/typical Disposal route

maximum specific activity

Can be treated as non­radioactive

A key feature of the IAEA classification scheme is that it is based on the intended disposal route. For this purpose, short-lived wastes are defined as having half-lives of ‘less than about 30 years’. This allows caesium-137 (half-life 30.17 y) to be classified as short lived.