Experts: S. Suksi and T. Boal

The legal framework for the management of radioactive waste and decommissioning of nuclear facilities is provided by the 1984 Act and the Slovenian Act on Fund for Financing the Decommissioning of the Krš ko NPP and Radioactive Waste Disposal from the Krš ko NPP (Off. Gaz. RS 75/94). The 1984 Act is supported by fourteen regulations in the area of radiation protection and safety of which one is specifically related to radioactive waste: one concerning collecting, accounting, processing, storing, final disposal and release of radioactive wastes in the environment (Z3).

The existing documents provide the regulatory authority for SNSA to regulate the waste generated from the Krš ko nuclear power plant (NPP), the TRIGA research reactor of Još ef Stefan Institute (JSI), and the closed uranium mine and processing plant Zirovski vrh. The law also authorizes the SNSA to regulate waste which is collected from medical, industrial and research facilities. At present the SNSA is involved in the preparation of a new regulation for radioactive waste management in Slovenia.

The low and intermediate level radioactive waste (LILW) generated at the Krš ko NPP is stored in the adjacent radioactive waste building. At JSI Podgoriga, there is interim storage (Brinje) for low and intermediate level solid radioactive waste (LILW) from the reactor JSI center and other small waste materials from medical, research organizations, and industrial applications of ionizing sources. The responsibility for operation of the interim storage was transferred in 1999 from JSI to the Agency of Radioactive Waste Management (ARAO), which was founded in 1991 by the Decree of the Government, and has a status of public enterprise which reports to the government. Its budget comes from the state budget and the fund for decommissioning of the Krš ko NPP. The relationship of ARAO to SNSA is the role of an operator. ARAO is also responsible for Zavratec provisional radioactive waste storage facility and for abandoned radioactive sources. According to the new Decree on Rules of Procedure adopted in 1997, one of the tasks of ARAO is to provide public service in radioactive waste management, storing (except for radioactive waste from the Krš ko NPP and the Zirovski vrh Mine) and disposal (except for the Zirovski vrh Mine) in the Republic of Slovenia. The most important operational task of ARAO is to construct the repository for LILW in Slovenia.

The current main radioactive waste responsibility of the Division of Nuclear and Radioactive Material (DNRM) with support of other divisions within the SNSA is to develop a licensing approach for waste repositories and storages, e.g., modernization of Brinje, removal of radioactive waste (RW) from Zavratec to Brinje and closure of Zavratec, and a new building at the plant site for storage of the replaced steam generators. The most important recent licensing activities have been: return of spent fuel from TRIGA to US; transit licences for Italian and Romanian spent fuel; fresh fuel purchase for the Krš ko NPP; and approval of the “In Drum Drying System” (IDDS) for evaporation bottoms and spent resins from NPP. The mining and milling wastes at Zirovski vhr mine are under the regulatory control of the SNSA according to the 1984 Act.

9.1. CLASSIFICATION OF WASTE

Radioactive wastes are specified by the Regulation (Z3) as follows: “Solid radioactive wastes are materials with the specific activity greater than 10⁸ Bq/m³ for beta and gamma emitters, and greater than 10⁷ Bq/m³ for alpha emitters or, alternatively with the surface contamination greater than 5 kBq/m² for beta/gamma emitters and greater than 500 Bq/m² for alpha emitters”. Liquid and gaseous radioactive wastes according to (Z3) “mean waste substances in liquid and gaseous state containing radionuclides in amounts greater than derived concentrations for air and drinking water for groups of members of the public.” According to specific activity, radiotoxicity and technology for processing, solid and liquid radioactive wastes as well gaseous radioactive wastes are categorized into high level, intermediate level and low level radioactive wastes. The categorization is the same for all radioactive wastes, both generated in connection to the use of nuclear energy and for small user waste. The observance of the limits means that the radionuclide concentrations in liquid releases are required to be as low as concentrations in drinking water. Current procedure is relevant for environmental aspects but not appropriate due to the volume of radioactive waste produced.

The current Slovenian regulation does not accept the “dilute and disperse” principle of radioactive waste management. Waste and materials containing small amounts of radionuclides can be discharged to the environment, disposed to special dumpsites or released to restricted recycling or reuse by the authorization of the regulatory authority.

The classification system does not cover “natural” classification parameters, e.g. grouping the radioactive wastes in terms of their origin, physical properties or their management. The legislation does not define clearance levels for radioactive material as recommended in the International Basic Safety Standards for Protection against Ionizing Radiation and for the Safety of Radiation Sources (BSS-115).

The purpose of clearance levels is to reduce the amount of radioactive waste handled, stored and disposed of, taking full account of the requirements of radiation protection. It is important to segregate waste arising from different areas of the NPP to distinguish material that can be considered of being practically uncontaminated and may be cleared, from material, which needs a more controlled waste management approach. An important feature of decommissioning would also be the possibility to clear waste material for recycling, reuse or conventional disposal.

In operational work it is not practical to use the clearance criteria in terms of doses. Therefore, the regulatory authority should develop derived radionuclide or nuclide group specific clearance levels in terms of activity concentrations or activity. Although the radiological criteria of clearance are similar to the exemption criteria, derived clearance levels are generally less than to the exemption levels presented in the Basic Safety Standards (BSS).

9.2. REGULATORY AUTHORITY FOR HISTORICAL WASTE MATERIAL

There has been legislation covering the use of radiation sources in Slovenia since the 1950s. Radioactive waste has been stored for considerable time at a temporary waste storage facility at Zavratec and in a interim storage for low and intermediate waste repository at Brinje. The Ministry of Health has an inventory of all radiation sources in Slovenia. The Ministry of Health approves the transfer of sources from authorized users to the interim storage facility.

Zavratec storage facility is an old military barracks in Western Slovenia near the village of Zavratec, where drums containing materials contaminated by radium in an accident at the Oncological Institute in Ljubljana in the beginning of the 1960s were transported. An ampoule containing 10 mg of radium sulphate was accidentally opened. The content, with an estimated total activity of 370 MBq, was dispersed over several rooms. After decontamination, about 30 m³ of contaminated materials were transported to an old military barracks and stored in a barracks room. To prevent intrusion, the entrance was walled up. In 1996, remeasurement, inventory, and repacking of the waste was carried out. After repacking, the storage room and the room next to it were walled up. It is planned that all radioactive waste will be moved from the Zavratec facility to the interim storage facility Brinje by the end of 1999. On the 1 December 1999, 21 drums of material were transported to Brinje. There are still 54 drums at the Zavratec facility of which 10 are sorted and repacked. ARAO is responsible for the Zavratec storage facility and the SNSA is the regulatory authority to license the removal of RW from Zavratec to Brinje and to license the closure of Zavratec.

There is an old uranium mine in Slovenia. The mine is in the process of being decommissioned, and there are waste materials from the mining and milling of the radioactive ore to be rehabilitated. The Government of Republic of Slovenia decided in 1978 to develop the Zirovski vhr uranium mine to supply nuclear fuel for the Krš ko NPP. Uranium ore extraction began in 1982 and uranium concentrate production by acid leaching process started in 1984. During operation until 1990, when the Slovenian Government decided to close the uranium mine, 620000 tons of ore was mined. A law was issued in 1992 defining termination of uranium mining and on-site and environmental rehabilitation. In 1994, the Government approved the feasibility study for safe mine closure, decommissioning and remedial works. Due to a significant delay in the execution of the plan an updated programme, which was approved by the Government at the end of 1998, was prepared in co-operation with the Ministry of Environmental and Spatial Planning and the Zirovski vrh mine. In accordance with the new programme, all remedial works and mine waste disposal will be finished in 2005. The SNSA does not have developed a policy document setting out their requirements for the rehabilation of these wastes.

The licensing of uranium mining and yellow cake production was performed by the mining authorities. The operator is responsible for the decommissioning of the Zirovski vrh and the Ministry of Health gives the formal licence. On the basis of the 1984 Act the uranium mining and processing plant is not a nuclear facility. The SNSA is the regulating authority in waste disposal. There are presently three different approaches for disposing of the barren rock and mill tailings. The mining company would like to keep the tailings in place, covered. The suggested solution of the SNSA is the pumping of tailings back into the mine. The third solution presented is to move the tailings to other sites. Public acceptance also in this unresolved issue is one of the key problems.

In the frame work of the Regional Programme for Nuclear Safety Improvement of European Union (PHARE programme) an analysis of the situation of the radioactive waste management has also been performed in Slovenia. For performing the above project European Commission has granted the service contracts to CASSIOPEE. The report pointed out that the management of radioactive waste from the former uranium ore mining and milling activities in the context of future remedial action in Zirovski vrh site is one of the important issues in radioactive waste management in Slovenia.

9.3. FINAL WASTE DISPOSAL

At present there is no final repository for any type of radioactive waste available in Slovenia. The LILW storage at the Krš ko NPP was designed only for a temporary storage for five years. Because of the delay in siting and construction of LILW disposal facility, the available storage capacities at the NPP are close to exhaustion. At the end of 1998, 90% of the total capacity was occupied. Several volume reduction campaigns have been performed by the NPP requiring the approval of SNSA. The first supercompaction campaign was carried out in 1988-1989 and the second in 1994-1995. During these campaigns a total of over 10 000 standard drums were compacted into steel drums or special casks, so called Tube Type Containers (TTC), that are tested according to IAEA recommendations.

In order to further reduce waste volume arising from liquid effluents at the NPP, the so called IDDS process of evaporation bottoms and spent resins was introduced by the NPP. The process had a long licensing approval period because of a new type of waste produced a new packing material, which was not taken into account in the Performance Assessment (PA) or Safety Assessment (SA) of the LILW disposal. According to the tests the standard carbon steel drum without coating would corrode in one year. The stainless steel drums finally accepted will last at least 30 years without corrosion problems. The IDDS process has a permit from SNSA for experimental use for two years to produce 20 drums of dried residues per year. The operating licence for IDDS was issued under condition that operator will perform appropriate conditioning of waste to meet acceptance criteria for disposal. In addition, the operator shall establish a special control over 40 carbon steel drums in which the dried product was stored during the experimental phase. Under these arrangements the LILW storage capacity of Krš ko NPP will be sufficient until the commissioning of the final LILW repository, which should be sited, evaluated and constructed by the year 2007 according to the official programme of ARAO.

In order to reduce the volume of radioactive waste of NPP, the plant sent 228 drums of low-level radioactive waste (plastic, paper, textile materials) to be incinerated in Sweden in November 1998. The incinerated products were returned in summer 1999.

The interim LILW storage (Brinje) is a near surface concrete building covered with earth. Three kinds of solid radioactive waste are stored there. Contaminated laboratory materials and activated material due to irradiation in the TRIGA reactor are stored in closed drums. Other contaminated or activated bulky solid materials, which cannot be situated in drums due to their large size, are separately stored without packing. The third class are spent sealed sources stored in shielded containers. The volume of active parts in sealed sources is insignificant, but they take up substantially more space (90% of the occupied capacity) because of the protective containers in which they are kept. In recent years there has been a substantial increase in quantity of sealed radiation sources. The waste containers are distributed over the floor of the storage room occupying major part of the ground. The present capacity of the storage is sufficient to receive all the quantity of drums stored, e.g., of the temporary storage Zavratec. Rearrangement or repacking of sealed source is necessary. It would also be possible to reduce the waste volume by supercompaction, but due to small waste volume this waste will be directly transported to the disposal site in the standard drums. The ARAO has a temporary licence for the LILW storage at Brinje and is currently accepting waste in emergency situations. Documents for the final licensing will be submitted to the SNSA in May 2000 and the operation licence is expected to be issued after refurbishment.

At the moment there are no pre-selected or favored sites for LILW and HLW disposal in Slovenia. The first studies concerning the LILW repository started before the nuclear power plant went into operation. Mainly due to economic and technical reasons it was limited only to surface and near surface type of repository. In parallel with this work, a survey of abandoned mines and exploration drillings deeper than 50 meters was started. The technical part of the project, based on systematic technical screening of the territory to identify the most suitable areas or locations, was performed 1990-1993. As a result, five suitable locations were identified in the Eastern part of Slovenia. The technical confirmation step was stopped due to strong public opposition. The ARAO plans to identify ten possible locations for LILW disposal in near future. It is planned that the siting process will include both a surface and an underground repository. A programme of site selection, which should be adopted by the government, is under preparation. For the HLW disposal, ARAO has not performed any site selection studies. Because of that, it is not possible at the present time to develop site-related proposals for deep underground disposal of HLW.

The spent nuclear fuel at the Krš ko NPP is stored in the 12 metres deep pool. Two thirds (horizontally) of the pool is occupied by racks in one level that have 828 storage positions. At present there are 562 stored spent fuel assemblies. At the current annual discharge rate of 28 to 32 fuel assemblies, the capacity of the pool is sufficient up to the year 2003. For this reason NPP has plans to increase the capacity of the pool in 2002. One proposed solution is the re-rack the stored spent fuel assemblies and to utilize the unused section of the pool. This would increase the pool capacity, and it would then be sufficient to accommodate all the fuel discharges until expiration of the designed life of the Krš ko NPP in 2023 and beyond. The utility has presented plans for related activities but not submitted to the SNSA an official application concerning this modification for decision in principle. The SNSA is still uncertain of the modification level and how it would affect the design basis and safety criteria and margins.

The government of Slovenia adopted in 1996 a document entitled The Strategy on Spent Fuel Management. The document is to be reviewed and supplemented every three to five years. A revision of this document needs to be completed within the next few years. According to the current strategy, a decision on the long term spent fuel management is deferred. The final strategy on permanent nuclear fuel disposal will be accepted in Slovenia by the year 2020. The disposal of the nuclear waste in third countries will also be considered. A final solution is expected by the year 2050. If the high level nuclear waste repository is not available for direct disposal of spent fuel at the time of shut down of the NPP, a facility for dry interim storage of spent fuel would be needed. This facility could also be used to temporarily store highly contaminated and activated components from dismantling of the NPP.

The spent fuel from the TRIGA Mark II research reactor was stored in the pool of the reactor building. In July 1999, 218 spent fuel rods and one damaged fresh fuel rod were returned to the USA. For the future operation of TRIGA only low enriched uranium will be used. At present there are 94 fuel rods, approximately half in the reactor core and half in the fresh fuel storage. This will be sufficient to operate the reactor until 2006. The research reactor has, according to the contract US DOE, an option to return this fuel to USA until May 2009.

9.4. DECOMMISSIONING REGULATORY STRUCTURE

The legal framework for the decommissioning of nuclear facilities is provided by the 1984 Act and the Slovenian Act on Fund for Financing the Decommissioning of the Krš ko NPP (Off. Gaz. RS 75/94). The purpose of the Act (Off. Gaz. RS 75/94) is to provide funds for decommissioning of the NPP and for spent fuel and RW, originating from decommissioning, disposal. The NPP is obligated to pay a levy on every kWh produced into the Fund. In order to assess the levy the Government of Slovenia has to prepare a decommissioning plan. The Fund is already financing certain activities of the ARAO.

Pursuant to Law, the Government prepared a decommissioning programme for the Krš ko NPP in 1996. The programme has been prepared on the basis of the study performed by NIS Ingenieurgesellschaft mbH (NIS) - Development of a Site Specific Decommissioning Plan for Krš ko NPP, (April 1996). The plan covers decommissioning and disposal of spent fuel and radioactive waste (RW). Half of the costs are attributed to the spent fuel management. According to the plan, the decommissioning levy varies according to the chosen scenarios. Owing to the other uncertainties, the NPP is contributing a conservative levy (0.61 SIT/KWh), as set by the Law. The administrative measures for decommissioning are similar to administrative measures during operation. Programmes and procedures for quality assurance and quality control need to be established. All activities are to be carried out in accordance with the licensees and procedures, and controlled by the regulatory authority. The programme does not consider necessary measures pertinent to radiological and nuclear safety.

Decommissioning, as defined by the Slovenian Law means the removal and safe final storage of all radioactive parts and materials from the site. Contrary to the worldwide practice, the Krš ko decommissioning plans include also the disposal of spent fuel and other operational radioactive waste.

The selection of decommissioning strategy needs to be harmonized with the law of the Republic of Slovenia. When Slovenian legislation is completed, international guidelines, standards and good industry practices have to be taken into account. Immediate and later dismantling are of equal duration, whereas the entombment lasts longer. Immediate dismantling could be finished in approximately 14 years assuming that the LILW and HLW disposals are already available. The most time consuming phase of the strategy is the storage of components due to radioactive decay. If the cost analysis justifies it and if a final disposal repository is available, the temporary storage could be shorter or may not be required. The strategy of later dismantling lasts the same period of time. However, the activated materials are stored in place, until radioactivity sufficiently decays, regardless of whether the radioactive waste repository is available or not. For the Krš ko NPP decommissioning as the most recommendable strategy is regarded the strategy of immediate dismantling. An important safety aspect is that the decommissioning activities are carried out by the Krš ko NPP personnel using the experience of former plant operation and the earlier usage of the Krš ko site for new activities.

For the TRIGA research reactor a decommissioning plan has not been developed. The Ministry of Science and Technology is responsible for the financing the decommissioning of the research reactor.