Final product of activities with radioactive materials is radioactive waste. A large amount of radioactive waste is produced in operation and decommissioning of nuclear facilities. Largest amounts of radioactive waste are produced in operation of Ignalina nuclear power plant. A large amount of it will be produced in future when decommissioning will begin. Radioactive waste is also produced by small users of radioactive materials – all waste producers, except of nuclear facilities (nuclear power plant, storage facilities of nuclear and radioactive material, treatment facilities and facilities for final disposal of radioactive waste – repositories).

 

Radioactive waste – it is a material that contains radionuclides or is contaminated with radionuclides at concentrations or activities higher than clearance levels as established by the regulatory body, and for which no use is foreseen.

 

The main goal of radioactive waste management – to manage radioactive waste in such a way, that individuals, society and the environment would be adequately protected now and in the future against negative impact of ionizing radiation.

 

 

Following the recommendations of International Atomic Energy Agency, radioactive waste shall be managed in accordance with principles, which states, that:

These principles are legalized in Lithuania in the Law on the Management of Radioactive Waste.

 

Lithuania, seeking to implement internationally accepted principles of radioactive waste management, at the end of 2003 signed and ratified the Joint Convention on the Safety of Spent Fuel Management and on the Safety of Radioactive Waste Management.

 

Radioactive waste management is described as activity related to management and utilization, involving the pre-treatment, treatment, conditioning, transportation, storage and disposal of radioactive waste, decommissioning of a radioactive waste management facility, and the permanent closure of a radioactive waste repository.

 

When ways and methods of radioactive waste treatment are chosen, radiation protection measures shall be used in such a way, that the doses, which can be received by the workers and population, should be as low, as reasonably achievable, economic and social factors being taken into account.

 

The International Atomic Energy Agency (IAEA) recommends implementing two strategies of radioactive waste management:

 

 

With the aim to implement the main goal of the radioactive waste management and in accordance with basic principles of radioactive waste management, radioactive waste shall be managed under the general consistent radioactive waste management scheme. Separate stages of the radioactive waste management are associated and complementary. In this case it is especially important, that sequence of the radioactive waste management stages would be hold.

 

The “good” radioactive waste management system consist of technological links between waste management stages which should be exercised consecutively, one after another, - from the moment of originating of radioactive waste until its disposal.

Fig 1. The components of radioactive waste management system

Classification of Radioactive Waste at Nuclear Facilities

A large amount of radioactive waste is produced in operation and decommissioning of nuclear facilities. The most of radioactive waste is produced in operation of Ignalina nuclear power plant. A large amount of it will be produced in future when decommissioning will begin.

 

Radioactive waste can be solid, liquid or gaseous, therefore, taking into account its state, the ways and methods of waste treatment and disposal (discharge) are chosen.

 

Liquid radioactive waste shall be classified and segregated in accordance with:

 

 

Solid waste shall be classified and segregated in accordance with the radiological classification parameters given in Table 1.

 

 

Table 1. Classification of solid radioactive waste

* Containing beta and/or gamma emitting radionuclides with half-lives less than 30 years, including Cs137, and/or long lived alpha emitting radionuclides with measured and/or calculated, by using approved methods, activity concentration less than 4000 Bq/g in individual waste packages on condition that an overall average activity concentration of long lived alpha emitting radionuclides is less than 400 Bq/g per waste package
** Containing beta and/or gamma emitting radionuclides with half-lives more than 30 years, not including Cs137, and/or long lived alpha emitting radionuclides with measured and/or calculated, by using approved methods, activity concentration more than 4000 Bq/g in individual waste packages on condition that an overall average activity concentration of long lived alpha emitting radionuclides exceeds 400 Bq/g per waste package.
*** Depending on acceptance criteria applied to sealed sources.

 

 

 

After assessment of radiation protection criteria, the radioactive waste, which meets these criteria, is classified as cleared waste. Radiation protection requirements are no longer applicable, therefore waste is treated as non-radioactive.

 

 

Radioactive waste is classified as very low level waste, if the dose rate at the 10 cm from the surface £0,5 mSv/h. It is disposed at the landfill type disposal facility. Landfill type disposal facility is trenches, excavated at the ground surface. Radioactive waste packages are disposed in these trenches. The disposal facility of such type is planned to be erected at the Ignalina NPP site in the near future.

 

 

A large amount of short lived low and intermediate level radioactive waste is generated in operation of Ignalina nuclear power plant and amount of it will be generated in future when decommissioning will begin. Since this waste is less hazardous than long lived high level radioactive waste, facilities for its disposal are installed at the ground surface, or near the ground surface (up to a few tens of meters) under ground level.

 

Since the beginning of operation of Ignalina nuclear power plant all the waste produced by the plant are storied at not very safe interim storage facilities, in which the safety is warranted for only limited period of time. The Government of the Republic of Lithuania in the Strategy on Radioactive Waste Management (approved in February 6, 2002) has foreseen to install new disposal facilities in Lithuania, to perform investigations and to prepare recommendations how to create near surface disposal facility.

 

After summarizing the world experience in the field of radioactive waste disposal, RATA has developed a conception of the near surface disposal facility. The choice was made on the barrow type construction (see fig. 2).

Fig. 2. Near surface, barrow type construction of disposal facility (Source: www.rata.lt)

 

 

High level long-lived waste and spent nuclear fuel, because of the properties of its radionuclide content, shall be disposed in the deep geological repositories. The repositories shall be installed not less than 500 meters under the ground level. Now the sitting for the repositories is in place in Lithuania.

 

Here are a few suitable geological formations for deep repositories in Lithuania: crystal foundation, clay and anhydrite, rock salts. Investigations showed that probably most suitable are the rocks of clay and crystal foundation. For spent nuclear fuel disposal it is proposed to use copper containers, which are very resistant for corrosion, and to fill the interspaces between containers and geological environment with special material.

 

 

The Maisiagala repository is a radon type disposal facility in the District of Širvintai, Barkuškis forest (about 30 km to north-west from Vilnius), which has been operated from 1963 to 1988 in Lithuania. The waste produced in research, medicine and industry was disposed in this facility. The waste consists of calibration instrument, chemical compounds, charge eliminators, high activity gamma sources, smoke detectors, solid radioactive waste (such as plastic, special closes, wood etc.). The facility consists of a subsurface concrete vault with an overall volume of about 200 m³. The vault was filled to about 60% with waste (total volume about 60 m³). Waste were grouted inside the disposal cells and the repository has been covered by a concrete blocks, bitumen, asphalt and earth. The horizontal dimensions of the vault measured between the middle of the walls are 5 m×15 m. The inner height is 3 m.

 

At present this facility is closed and all radioactive waste, produced in research, medicine and industry (so-called ”small producers”) is transported to Ignalina NPP for disposal to the interim storage facilities.

 

At present the safety assessment of Maišiagala disposal facility is performed and improvements in the safety systems will be performed on the basis of Safety Analysis Report.

Fig. 3. Maišiagala Radioactive Waste Disposal Facility

 

According to the Law on the Management of Radioactive Waste, the Radiation Protection Centre takes part in the process of issuing the license (for RATA) for surveillance of Maišiagala disposal facility.

 

 

According the Law on Radiation Protection, the Law on Nuclear Energy, Law on the Management of Radioactive Waste, the Radiation Protection Centre: