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i19

Routine releases of radioactivity

Significance

Routine releases are the authorized intentional discharges ofradioactive effluents from nuclear power plants, reprocessing plants and other nuclear installations. On daily base these releases may not seem significant, but because they are going on day after day, year after year, considerable amounts of radioactive materials are cumulating in the environment. As far as known no systematic investigations have been performed on the health effects of the cumulation of radioactivity by routine releases in the human environment. Recent reports in Germany and France proved that routine releases are far from harmless [more i23].

Discharges from reactors

During the fission process in the nuclear reactor tens of different kinds of radionuclides come into being in the fuel, in the coolant and in the construction materials. Operating reactors release in the liquid and gaseous effluents some fission products and activation products, such as tritium, carbon-14, noble gases (mainly krypton-85) and iodine-129. The fission products originate from leaking fuel pins and uranium contamination on the outside of the pins. The activation products are produced by neutron reactions on light elements in the cooling water and on corrosion products.

Data on operational discharges of nuclear power plants are scarce and incomplete; extremely little direct measurements have been published. Some small quantities of iodine-129 are undoubtedly present in gaseous and liquid effluents from power reactors, but it measurement is difficult because of high concentrations of other fission and activation products.

Interim storage of spent fuel

After removal from the reactor spent fuel elements have to be stored in water-filled cooling ponds for a long period, this is called interim storage. Due to the radioactive decay of the fission products and actinides the spent fuel generates so much heat, that fuel elements will melt within a short time if not effectively cooled. After some 30 years interim storage in cooling ponds the heat production has decayed sufficiently to handle the fuel elements for further processing.

Interim storage may become a source of inadvertent emission of radioactivity. During the storage 80-90% of the tritium in the fuel will diffuse from the fuel and released into the environment. Other nuclides are released into the cooling water from leaking fuel pins. The number of leaks will rise over time, due to ageing, corrosion and deterioration of the materials.

Operation and maintenance of the interim storage facilities are expensive. The water in the pools has to be actively cooled and decontaminated during een period of at least 30 years. The spent fuel of the new generation of reactors, such as the EPR, has to be cooled for a period of at least 60 years. The basins deteriorate and may go leaking, as happened at several occasions in the past, and have to be replaced. These activities do not generate financial profits for the company which operated the nuclear power plant during its productive life. Does that company still exist 30-60 years after closedown of the plant?

Reprocessing plants

Reprocessing plants discharge large quantities of radioactive materials into the environment. All gaseous fission and activation products from the processed spent fuel are routinely released into the atmosphere: radioactive noble gases krypton and xenon, tritium, carbon-14 and iodine. Substantial amounts of chemically mobile radionuclides, which do not easily form stable and/or insoluble compounds are discharged into the sea via the waste water streams. As separation processes never go to completion, significant amounts of actinides are released, in addition to the discharged soluble or gaseous fission products [more i31]. The standards of permitted releases, which are formulated by the nuclear industry, are dimensioned in such way that the reprocessing plants are permitted to discharge into the environment all radionuclides which are difficult to retain.

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