Decommissioning of the Spent Fuel Storage at the RA Reactor Facility, Serbia

Nuclear research reactor RA was constructed in the second half of the 1950s. It was designed in the former Union of Soviet Socialist Republics (USSR), where the main components were also manufactured. The reactor became the largest research nuclear facility in the former Yugoslavia, and was a multipurpose research reactor providing a relatively high neutron flux in the core. It belonged to the second generation of research reactors that gave an important contribution to nuclear technology development in the country. The RA reactor was a tank type reactor using heavy water as a primary coolant and as a moderator. The primary cooling system circulated heavy water to cool the fuel elements in the core and remove heat by upward forced circulation. Its nominal power was 6.5 MW. The facility went critical in December 1959 and was temporarily shut down in August 1984. During this period of operation, the reactor was successfully used for scientific research, but also for commercial purposes. From its first commissioning in 1960, until 1975, the reactor used low enriched uranium fuel (2% of ²³⁵U). In 1976, the original fuel was gradually replaced by a high enriched fuel (80% of ²³⁵U) that was developed and qualified in the former USSR. After temporary shutdown in 1984, followed by a set of thorough examinations of its systems and equipment, it was decided to reconstruct the reactor systems to enable safe and continuous operation in the future. The reconstruction, with financial help from the IAEA, started in 1986, but owing to international sanctions imposed upon the former Yugoslavia in 1992, the reconstruction work has never been finished. The facility was then left in an extended shutdown regime under passive care and maintenance