Long-term RAW isolation strategy

The RAW isolation process is based on the principle of multi-barrier pro­tection at all stages. RAW conditioning allows the immobilization of radio­nuclides in durable matrix materials (such as glass, cement, ceramics, etc.), which are then placed into special protective casks, such as metal drums or metal and reinforced concrete containers, for transportation. Any voids are filled with special backfill. Conditioned RAW is then placed into hydro — isolating repositories, of which there are three types: near surface, well-type and drill-type. These constructions are supplied with a system of multifunc­tional barriers, which prevents any interaction between RAW and external factors. Interaction between the radionuclides and the environment is pre­vented by both man-made and natural barriers, with each performing its own shielding function. The multi-barrier system means that the safety of the repository is not dependent on one barrier alone, and is assured not only by technical means, but also by technical-organizational measures. The principle of multi-barrier protection guarantees the safe storage of RAW over the whole period during which they pose a radiological hazard.

In accordance with the recommendations of the International Atomic Energy Agency (IAEA), long-term RAW storage facilities must guarantee geo-ecological safety for the entire period of operation. In the national programmes of RAW management, most countries have set the normative period for low and average level activity RAW at 300 and 500 years. This can be explained by the fact that near-surface type repositories are only used for low — and intermediate-level RAW (LLW and ILW) with half-lives of less than 30 years. Over the course of the operation of these repositories, the activity due to natural decay will be lowered, in comparison with the initial level, by three orders for LLW and five orders for ILW.

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