Management and final disposal of short-lived low- and intermediate-level radioactive waste

The category of low-level radioactive waste often includes such examples as overalls, paper, wood, filters, used appliances, scrap-iron, concrete. The waste of this type emits radiation which is not high. Thus, it may be managed and transported without using special protective screens. The waste of this type is usually disposed of in repositories constructed on earth surface. These repositories contain a multiple-barrier safety system ensuring that radionuclides contained in the waste decay inside the repositories and do not spread outside in the environment.

Spent ion-exchange resins, liquid waste concentrates, reactor components, ashes, and suchlike are often attributed to the category of intermediate-level radioactive waste. However, radiation emitted by the waste of this type is much higher. Therefore, reliable protective measures such as protective screens or remote-controlled equipment are required. The waste of this type is usually disposed of in the same way as low-level radioactive waste.

A near-surface repository consists of reinforced concrete vaults established on the earth surface. Radioactive waste packages are placed into the vaults and covered with a multi-layer shelter resistant to atmospheric effects. This method is universally accepted and has been used by different nations. Before disposal, waste is managed and packaged.

Figure 1: A near-surface repository for short-lived low- and intermediate-level radioactive waste.

The repository’s conceptual design in Lithuania was developed after scrutinizing analogous designs and operational experience of near-surface repositories existing in other countries (Japan, France, Spain, and Slovakia). After the advantages and disadvantages of each design were analyzed, the climate conditions of Lithuania were evaluated, and the environmental impact assessment was carried out, a design of mould type with multiple barriers was selected. That is the construction containing a system of engineered and natural barriers which complement one another. The system reliably isolates the radioactive waste and protects the environment against potential pollution. In Lithuania a near-surface repository will be constructed using natural materials that are steady and long-lived. Waste packages placed into reinforced concrete vaults will be covered with a layer of clay and soil. Reinforced concrete helps retard migration of radionuclides and prevents people or animals from intruding into the repository. The barriers of clay and soil preclude the damp from penetrating into the vaults. The planned repository will contain separate sections which will be easily applicable for disposal of a smaller or larger amount of waste.

Reinforced concrete vaults containing waste will be covered by a moveable shelter. An overhead crane will be mounted under the shelter. The crane will be remote controlled. When the vault will be completely loaded by the waste, it will be sealed and the shelter will be moved to the next vault. The loaded and sealed vaults will be covered with a layer of clay and soil.

It has been estimated that such repositories remain stable long enough until the activity of short-term low- and intermediate-level radioactive waste naturally decreases.

The Government of the Republic of Lithuania issued its decree following which a site most suitable for a near-surface repository for short-term low- and intermediate-level was approved. The site is located in the territory of Visaginas municipality, namely the Stabatiske site, in close vicinity to the Ignalina Nuclear Power Plant (NPP). This location was approved based the results of environmental impact assessment, the conclusions of experts, the reasoning and comments expressed by experts from neighbouring countries – Belarus and Latvia. The designing works are expected to begin in 2008, the start of the construction works is foreseen in 2012, while operation of the repository for radioactive waste is expected to commence in 2015.

To enlarge the picture, click it.

Figure 2: A map of the Ignalina NPP environs.

  Stabatiske, the site of repository for short-term low- and intermediate-level radioactive waste.