Aquatic Pollution and Coastal Management

Unit 10 : Radioactive pollution

10.7.Control of Radioactive Pollution
Out of all the sources only artificial radioactivity can be controlled. However, little can be done when the radioactivity is already released into the environment from the source.
Radioactive wastes concerned with water pollution are usually in liquid or solid state. All low or high level wastes have a tremendous capacity to pollute the environment. Low level wastes are produced in large quantities and their containment is not possible and high level wastes on the other hand can not be disposed off free in the environment but have to be concentrated, contained and sorted out of the environment.

Critical Path Analysis
A more stringent safeguard is provided in setting limits to radioactive discharges to the sea by directing attention to “the most likely route by which radionuclide may reach the human population and dose likely to be received by that section of the population most at risk”.
Critical path analysis is used to determine discharge standards in a number of countries and this accounts for a great variation in the limits set for each installation, which must take account of local circumstances and the critical pathways of exposure of the human population to radioactivity.
Example: A large range of radionuclide is included in the liquid effluent, which is discharged from reprocessing plant in to the Irish Sea. The Irish Sea supports a variety of commercial fisheries and the most critical pathway to man through the consumption of contaminated seafood from the area proved surprisingly, to be by the seaweed, Porphyra.

• Use of the critical path approach requires constant vigilance to take account of changing circumstances and increasing knowledge of the behaviour of radionuclide.
• During 1970’s Porphyra ceased to be significant pathway and Porphyra was no longer used in the preparation of laver bread. Locally caught fish then assumed critical position.
• Maximum exposure of the individual in the critical population from fish consumption was 34% of the dose limit recommended by ICRP.
• 1976-24% of ICRP recommended dose.
• Subsequent years 10% of ICRP recommended dose.
• 1982 F.A.O. reported that estimated consumption of molluscs had increased threefold. Intake radionuclide had increased by a similar factor.
• Exposure 24-39% of ICRP annual dose limits.
• Steps were taken to reduce the discharge of radionuclides.