The basic approaches used in handling and disposal of radioactive wastes are;
Delay and decay
Dilute and disperse
Concentrate and contain
Delay and decay:
It is based on the fact that radionuclides lose their radioactivity through decay, and this fact maybe utilized in the treatment not only of intermediate and high level solid, liquid and gaseous wastes but in some cases also in that of low level wastes. The aim is to ease problems in subsequent handling or to lessen risks of releases to the environment, taking advantage of the decay of some radionuclides particularly those having short half-lives with the passage of time. The principle is especially useful for those installations where a substantial reduction in the activity level of a waste stream can be achieved by delaying discharge of effluents for a few days.
Dilute and disperse:
The principle of dilution and dispersion is based on the assumption that the environment has a finite capacity for dilution of radionuclides to an innocuous level. The application of this principle requires an understanding of the behaviour of radioactive materials in the environment and of the ways in which the released radionuclides, particularly those that are considered to be critical, may lead later to the exposure of man. It is especially important to take into consideration environmental processes which may cause re-concentration of radionuclides.
The above figure Radioactive wastes containment
Concentrate and contain:
The principle of concentration and containment derives from the concept that the majority of the radioactivity generated in nuclear programs must be kept in isolation from the human environment. Since some radionuclides take a long time to decay to innocuous level, some wastes must be contained for extended period of time.
The principle is invoked in techniques for air and gas cleaning the treatment of liquid wastes by scavenging and precipitation; ion-exchange and evaporation; the treatment of low level, solid wastes by incineration, baling and packaging the treatment of intermediate level solid and liquid wastes by in-solubilisation in asphalt; conversion of high level solid and liquid wastes to insoluble solids b high temperature calcinations or incorporation in glass; tank storage of intermediate and high level liquid wastes; storage of solid wastes in vaults or caverns; and disposal of solid and liquid wastes in deep geological formations.
1. Delay and decay method is used for
A) Intermediate level wastes
B) Short half-life radionuclides
C) High level wastes
1. b) Short half-life radionuclides.
1. The Textbook of Radiological Safety, first edition, by Dr. k.Thayalan.