Читать книгу Management of Radioactive Waste - Jean-Claude Amiard - Страница 9

Preface

The use of nuclear energy for military or civilian purposes inevitably leads to the production of radioactive waste. The management of this waste is one of the most serious problems facing industrialized nations.

As with all other wastes, radioactive waste can be disposed of in one of two ways: dilution or containment. A third method exists for radioactive waste with a very short physical life, less than 100 days, which is to wait, under safe conditions, for natural physical decay.

Dilution consists of reducing the radioactive risk by dispersing the radionuclides in vast compartments of the environment such as the lithosphere, the atmosphere or the hydrosphere. This can only be done for very low-level radioactive waste, even though it has been practiced more widely in the past.

Containment consists of immobilizing the waste as long as it remains radioactive. This is relatively easy for short-lived radionuclides, i.e. with a physical half-life of less than 30 years. On the contrary, it is much more difficult to ensure for long-lived radionuclides, for some of which the physical half-life is counted in millions of years. Currently, the only realistic and practicable solution found is the multiplication of physical barriers between the radioactive waste and the environment and the biosphere, the last barrier being geologically stable and impermeable layers of the lithosphere.

The classification of radioactive waste has been the subject of IAEA recommendations, but this has not prevented the multiplication of classifications in different states, which complicates possible comparisons. These classifications are based on a combination of two parameters: the waste’s level of activity and the half-life of the radionuclides constituting the waste.

A major difference in classification divides nations into two categories depending on whether they practice an open or closed nuclear fuel cycle. In the latter case, a portion of the radioactive waste is removed from this classification and is considered as usable nuclear material. However, the number of states using the closed cycle is steadily decreasing, which makes it necessary to review the quantities of radioactive waste to be actually managed.

The management of radioactive waste is specific to each state. The majority of nations manage short-lived radioactive waste in surface storage facilities and a minority in underground facilities.

On the contrary, for long-lived radioactive waste, few states have definitive solutions. This is due to the fact that the containment of the radionuclide must be guaranteed for thousands of years. For low-level waste, most countries opt for dry interim storage. For intermediate- and high-level waste, the solution generally envisaged is deep geological disposal, with some countries favoring deep geological drilling.

In the field of radioactive waste management, research is very active and innovations are numerous. This does not prevent gaps in our knowledge, uncertainties about the nature of the disposal to be adopted for certain categories of waste and often a negative opinion of the public to the proposed solutions.

June 2021