Clearing Yugoslavia’s nuclear past

The 6.5MW heavy water moderated and cooled RA research reactor located at the Vinca Institute of Nuclear Sciences near Belgrade in Serbia, was in operation from 1959 until 1984. In 2002, the Serbian government decided to decommission the RA reactor and its ancillary facilities, and set up for that purpose the Vinca Institute Nuclear Decommissioning (VIND) programme [1].

According to the decommissioning plan for the RA reactor, the first activity was the removal of fresh and spent reactor fuel. The fresh fuel, containing 48kg of highly enriched uranium in about 5000 fuel elements, was repatriated to the Russian Federation in 2002 as a result of a joint project between the Serbian government, the USA, the Russian Federation and the International Atomic Energy Agency (IAEA) [2]. The removal of about 2500kg of spent fuel is currently ongoing and comprises a number of coherent actions starting from the removal of spent fuel from spent fuel storage facility and reactor core, the packaging into proper shielding and transport containers and the final repatriation to the Russian Federation.

The second action within the VIND programme is the decommissioning of the RA reactor. Besides the development of the decommissioning plan and the full radiological characterisation of the facility, several experimental facilities and supporting equipment have been dismantled and processed as radioactive waste during the preparatory phase for spent fuel removal. Further decommissioning steps will include the decontamination of the empty spent fuel pool, the dismantling of the remaining reactor supporting systems, internals and core shielding with the subsequent decontamination and eventual dismantling of the reactor tank. The final decision of the Government of the Republic of Serbia on the decommissioning or future use of the reactor concrete vessel and the reactor building has not been done yet.

The third principal action that is being implemented within VIND programme is establishing and equipping appropriate and modern facilities for processing the historical waste from former Yugoslavian nuclear programme that has been improperly stored at the site in unsafe conditions. The facility will be used for retrieving waste from old waste storage facilities and for processing of all kinds of radioactive waste, generated in decommissioning activities. As a part of this action, a new surface storage facility (storage building) for processed waste and disused sealed sources has been recently completed next to the waste processing facility and is expected to be ready in 2010 to accept the waste packages.

In parallel, a radiation protection infrastructure is being set up and equipped to ensure the safety of all decommissioning and waste handling operations.

As a result of the recent promulgation of a new Law on Ionizing Radiation Protection and Nuclear Safety

in Serbia in May 2009, two new organizations, playing a key role in the implementation of the VIND programme, have been established. They are the Agency for Radiation Protection and Nuclear Safety of Serbia (ARPNSS) and the Public Company ‘Nuclear Facilities in Serbia’ (PC NFS). The latter will take the responsibility for management of entire VIND project and for the implementation of the Serbian part of all decommissioning activities at the Vinca site.

It should be also underlined that without external aid from several countries (USA and UK) and international organisations (Nuclear Threat Initiative, IAEA and the European Commission), the VIND programme would have faced significant funding problems.

Reactor decommissioning

The decommissioning plan for the RA reactor was prepared after its shutdown and was revised at the end of the 1990s in cooperation with IAEA. In spite of that, this plan did not fully cover all supporting facilities of RA reactor and needed to be updated due also to delays in implementation and consequent growing prices. The current decommissioning plan was completed on 30 June 2008 under an IAEA contract. An initial decommissioning activity removed about 5000 fresh fuel elements from the site and sent them to the nuclear centre in Dimitrovgrad in the Russian Federation.

The basic steps of the decommissioning of the RA reactor are:

1. The removal of spent fuel from the site including dismantling of selected experimental facilities and processing of the generated waste.

2. The decommissioning of spent fuel cooling and storage pool and processing of the generated waste.

3. The dismantling, decontamination and management/processing of the reactor core, supporting facilities, pipelines of the primary and secondary systems, shielding and reactor vessel.

4. The decommissioning and decontamination of concrete reactor vessel and reactor building (the decision is still pending).

These steps are briefly described.

1. Removal of spent fuel

The lifetime operation of the RA nuclear research reactor generated about 2.5 tons of irradiated nuclear fuel. Part of the fuel elements contain highly-enriched uranium or HEU (up to 80% in U-235 of uranium dioxide dispersed in the aluminium matrix) leading to proliferation concerns. In addition, about 30% of the spent fuel, currently stored in the spent fuel pool, is leaking. For these reasons and in accordance with the USA-Russian Federation agreement on the research reactor fuel return programme, the Serbian government accepted to repatriate all irradiated nuclear fuel to the Russian Federation. The repatriation programme, coordinated by the IAEA comprises three main steps:

• Spent fuel characterisation, removal and packaging;

• Transportation to the Russian Federation;

• Reprocessing, storage and disposal in the Russian Federation.

The first step began in 2006 and should be completed by mid-2010. The preparation of the transportation started in 2008 and the transportation itself should take place by the end of 2010. This repatriation programme has been estimated to cost about EUR36 million. Funding is provided or planned to be provided by the Serbian government, the European Commission, USA, the Nuclear Threat Initiative, the Russian Federation, the Czech Republic, and several other EU countries, as well as the IAEA.

The decommissioning/dismantling of the RA reactor supporting facilities, experimental loops, and equipment has already started in order to provide free space for the packaging of the spent fuel elements. The generated waste is being decontaminated, fragmented and packaged into standard 200L drums or HH HL ISO containers. It has been noted that a significant part of the dismantled equipment falls within a low level waste category with only surface contamination. Therefore deep decontamination to allow clearance would be possible once the criteria for radioactive waste clearance will be defined by the Serbian Nuclear Regulatory Agency. Until now about 40 tons of clean waste (mostly metallic debris) was removed from the reactor hall.

2. Pool and waste processing

Once all spent fuel elements are removed from the cooling and storage pool, adjacent to reactor hall, reactor decommissioning will start. First, the highly contaminated spent fuel storage tubes and containers will be removed, fragmented, decontaminated and packaged as waste for storage. Then, the high level waste stored as debris in the dry basin of the storage facility (composed mainly of parts of experimental facilities and of reactor internals replaced during the reactor refurbishment), will be removed and processed. Finally the waste will be fragmented, decontaminated (if surface contamination is expected) and placed into shielded containers (e.g. 200L drums with special shielding) for storage in the new storage facility at the site.

There are several scenarios currently considered for the spent fuel pool decommissioning. The most frequently-used and proven procedure is to first remove and process the 200m3 of cooling water and the contaminated sludge from the pool bottom (the technology to be used has not been decided upon yet), and then to subsequently decontaminate the stainless steel plated pool walls and bottom. This procedure has been applied in similar conditions elsewhere. The clean, decontaminated pool space can be then used as a temporary storage if needed. A final decision on full dismantling or re-usage of the pool space for other purposes has not been made yet.

A revised safety analysis report should be prepared for proposed scenarios. The decommissioning of the storage pool is tentatively scheduled for 2011 and 2012, providing sufficient funding is available, and the cost has been estimated at EUR2 million.

3. The reactor core and vessel

Remote control operation, special shielding and isolation of workplace with special local ventilation will be considered on a case-by-case basis in preparation of the detailed decommissioning plan.

Clearance of non-contaminated or properly decontaminated waste to reduce a volume of generated waste will be considered, and relevant legislation, control procedures and quality system to support clearance procedures will be prepared and approved well in advance by the relevant authorities.

Currently, a recently completed (2008) draft version of the decommissioning plan is available. Following removal of the spent fuel, the technical part will be updated, and a financial plan and an updated safety analysis report will be written.

Radioactivity survey

Besides the main reactor facilities at the Vinca Institute site, there are several facilities (partially or completely abandoned) previously used for various nuclear research activities, such as a building for the Van de Graaf accelerator, a material research facility, special radiochemical laboratories and pilot plants, a radioisotope production facility, etc. The facilities can possess certain radiological risks, contain possible orphan sealed radioactive sources and contaminated surfaces or equipment. Contaminated hot spots outside the buildings have also been detected, the most important of which is the location of a former open-air radioactive waste storage facility of the Institute. The waste from the last facility was collected and moved in 1984 into one of the covered waste storage buildings (Hangar 2).

A radioactivity survey of the Vinca site is expected to start in 2010 and will enable prioritisation of subsequent decontamination, decommissioning recovery and remediation programmes, which can be addressed by the newly created PC NFS. This activity is expected to last several years and an overall cost has been so far estimated to EUR1-2 million.

Waste management

Radioactive waste inventory

The Vinca Institute of Nuclear Sciences was established at the end of the 1940’s to assure the whole spectrum of civil and military nuclear research activities in the former Yugoslavia. More than fifteen research laboratories, two research reactors, acceleration facilities and other nuclear facilities have been in operation, and most of them have generated radioactive waste, which was initially collected and stored in an outdated and unsafe manner in an open air repository close to the laboratory buildings. In 1962 the 200L drums with radioactive waste were moved to an open trench storage area. The trench is close to the current new waste storage buildings. In addition, the Institute served as a collecting place for all radioactive waste generated in the former Yugoslavia.

Two light construction metal-sided hangars, Hangar-1 (H-1) and Hangar-2 (H-2), were commissioned in 1968 and 1982 respectively to temporarily store the waste.

H-1 is now full but is not leak-tight or isolated from the environment. The construction is corroded and in some places mechanically damaged, and the inner space is very probably contaminated by the radioactivity released from the stored waste packages. This hangar contains almost 800m3 of packaged and non-packaged waste and in particular [3]:

• About 1500 pieces of 200L metal (carbon steel) drums;

• About 300 pieces of 30L plastic containers;

• About 300 pieces disused sealed sources (Co-60 and Cs-137) in lead containers;

• An unknown inventory of different kinds of radioactive waste in the drums, as well as some contaminated free loaded wastes and materials.

H-2 contains more than 1000m3 of fully containerized waste and shielded sealed sources, in particular [4]:

• About 1000 standard 200L drums with repacked (compacted) waste former open pitch repository (the average activity is about 185 MBq/drum);

• About 300 standard 200L drums with very low activity air filters gathered after the Chernobyl accident;

• About 450 standard 200L drums with waste from various users;

• 31 pieces of 200L drums with cemented sludge (of 1996) from the reactor spent fuel storage pool (with an average activity about 150 MBq/drum);

• 17 pieces of 200L with concrete shielded non-conditioned sludge (in 10L plastic bottles) taken from the RA spent nuclear pool in 2009;

• Almost 1000 spent sealed sources (the total activity inside the containers is 22.2TBq);

• A small amount of other (mostly low level) radioactive waste.

H-2 is, in general, in better conditions, and safe manipulation of the waste is still possible. Although all of the waste is poorly characterized, the records for principal categories of the waste are available.

Low level liquid waste from reactors and laboratory operations has been collected and is stored in four underground stainless steel-plated concrete tanks. The volume of liquid waste is about 125, 385, 225 and 140 m3 in tanks No 1, 2, 3 and 4, respectively, with the fourth tank having only residual activity from a cross-ventilation line. The average activity of the waste is about 0.25 MBq/L (mostly Co-60 and Cs-137) with a relevant content of Am-241 (about 500 Bq/L). The waste is highly acidic (pH ~ 1-2) as a consequence of a high concentration of decontamination agents. After processing of the stored waste (the final procedure has not been decided upon yet) and decontamination of the tanks, the facility will be decommissioned and the adjacent area decontaminated. These activities are planned to be carried out in 2011 and 2012.

Based on various estimations, the waste expected to be generated during the Vinca site decommissioning activities consists of 5000m3 of compactible waste (about 1500m3 after compaction), 1000m3 of non-compactible and 300m3 of liquid waste.

Radioactive waste processing

In the past, only very limited radioactive waste processing options such as a low pressure compactor and simple cementation facility have been available at the Vinca site.

Establishing a proper and well-equipped radioactive waste processing facility became one of the highest priorities of the VIND programme, considering the existing and foreseen waste inventory. Thanks to the financial support given by the Ministry of Science and Technological Development of the Republic of Serbia and a number of donor countries and international organisations, one of the existing buildings at the Vinca site was refurbished and transformed to a Waste Processing Facility (WPF). This new facility will become operational early in 2010 and will be equipped with simple and proven technologies, tailored to processing of existing and foreseen solid and liquid radioactive waste existing at the site. Functions performed will include:

• Sorting of radioactive waste.

• Fragmentation of solid radioactive waste.

• Packaging of sorted radioactive waste.

• Compaction (at medium pressure) of solid radioactive waste.

• Cementation (in drum or with external cement mixer – not yet decided).

• Extensive radioactive waste control and characterization.

The WPF will provide for reprocessing and if necessary for the repackaging of all the historical waste from H-1 and H-2 and will be also able to fully process all expected kinds of decommissioning radioactive waste generated during SNF shipment and RA and H1 decommissioning.

Radioactive waste storage

It has been clear from the beginning of the VIND programme that the existing H-1 and H-2 do not comply with present requirements for safe and sound storage of the radioactive waste. The basic options considered to solve the problem were: the decommissioning of H-1 and refurbishment of H-2; the extension of H-2; the use of another building at the site as storage facility, and the construction of the new storage facility. Based on a cost/benefit analysis of these options, it was decided to construct a new waste storage facility, comprising two buildings – a large one for low level waste (H-3) and a smaller one (SS) shielded for storage of intermediate and higher activity waste, including disused sealed sources.

Thanks to the concentrated effort of the VIND programme management and combined funding by the local resources and international donors from the IAEA and the USA’s NTI and NNSA, the storage facilities, capable of accommodating about 5000m³ of conditioned radioactive waste, will be licensed in the near future. A secured radioactive storage facility for intermediate and high activity waste and disused sealed radioactive sources is expected to be licensed in 2010.

Conclusion

Significant progress in decommissioning and in all radioactive waste management activities at the Vinca Nuclear Research site (VIND programme) has been made due to the coordinated effort of all involved parties (local, donor countries and international organizations).

The preparation of spent nuclear fuel from the research reactor RA for repatriation is in an advanced stage and preparatory decommissioning work has already been started. The Vinca site is progressively being equipped with modern technologies and facilities that constitute a prerequisite for a safe and efficient decommissioning of the RA nuclear research reactor.

The waste processing facility and two new waste storage facilities are in a final stage of completion and should be commissioned in 2010. The first treatment and conditioning campaign will be devoted to the backlog of about 1000m³ of the most critical historical solid radioactive waste currently stored in the old hangars No 1 and No. 2. The capacity of all new facilities is sufficient to provide for processing of all historical and newly generated (decommissioning) waste.

Author Info:

Andrea Bucalossi and Rudolf Burcl are scientific officers at the European Commission’s Joint Research Centre in Petten, Netherlands; Lucien Cécille is programme manager at the European Commission in Brussels; Jadranka Djuricic´ is senior advisor for radiation and nuclear safety at the Serbian Ministry of Science and Technological Development; John Kelly is senior programme manager, IAEA-TC Europe Division. Andrea Bucalossi, EC JRC, (JRC F.5) PO Box 2, 1755 ZG Petten, Holland

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References

[1] NTI. Country reviews. Yugoslavia: Nuclear overview, www.tinyurl.com/la8o5bl and M.Pesic ‘Status of the VIND Program, November, 2008 The ENS 13th International Topical Meeting on ‘Research Reactor Fuel Management, ENS RRFM 2009, Transaction, pp. ps.1 – ps.5 Vienna, Austria (March 22-25, 2009), www.euronuclear.org/meetings/rrfm2009/transactions.htm [2] M Pesic, O. Sotic, K. Subotic, W. Hopwood Jr., S. Moses, T. Wander, A. Smirnov, A. Kanashov, A. Eshcherkin, S. Efarov, C. Olivieri, N-E. Loghin: ‘Return of 80% HEU fresh fuel from Yugoslavia back to Russia,’International Journal of Radioactive Materials Transport, Vol. 14 (3-4), pp.173-179, NTP (2003) [3] ‘The Waste Management Strategy,’ Vinca Institute, Rev.3., June 2006. [4] E. Bradley, M. Pesic, J. Kelly, P. Adelfang, I. Goldman, D. Jinchuk: ‘Repatriation of the Vinca RA Reactor Spent Fuel,’ Packaging, Transport, Storage & Security of Radioactive Material, Vol. 20, No. 2 , pp. 55-59 (2009)