The heavy-water reactor RA at the Vinca Institute of Nuclear Science, Serbia, was commissioned in the middle of the last year and shut down more than 20 years ago. As there had been no standard procedure for the SNF removal, the highly enriched fuel (8030 TVR-S SFAs) had never been removed from the reactor remaining in the SNF storage pool adjacent to the reactor. For various reasons, the SNF storage conditions could never meet standards and regulations, thus making the health of the fuel unsatisfactory. The observations of the water reactivity in the storage pool suggested worsening the situation from year to year.
In 2005, the IAEA called for an international tender whereby the damaged SNF had to be made transportable to a repressing facility in line with current safety requirements and regulations.
During 2003–2006, the Sosny staff took several missions to do a more detailed study of the SNF health and safety issues on the reactor site. These visits demonstrated that the quantity and complexity of the tasks associated with the SNF preparation and shipment from the Vinca Institute match the Sosny staff. skills. They prepared technical proposals on the SNF repackaging into canisters, loading into casks, transportation to a reprocessing facility, performed feasibility studies, and developed the project schedule. In June 2006, the Sosny R&D Company participated in the tender in cooperation with the Mayak PA and the Techsnabexport and won it.
In the period 2007-2008, a procedure for removal of the spent fuel stored in the reactor channels and aluminum barrels at the Vinca Institute was worked out in much detail.
Main safety aspects in preparing and transporting the spent fuel, i. e. the nuclear and radiation safety, thermal modes, fire- and explosion safety issues, were the focus areas. The VNIIEF calculations demonstrated that the time-bound transportation of the damaged spent fuel would be safe if loaded in specialized ventilated canisters for the TUK-19 and SKODA VPVR/M casks.
The SNF temporary storage and transportation required that dedicated ventilated canisters be developed to ensure regular ventilation and prevent an explosive hydrogen and oxygen concentration in the package. New large-capacity baskets for the SKODA VPVR/M casks were also designed.
All operations of the SNF preparation and loading into canisters were performed remotely by specialized equipment and tools. The storage basin accommodated a multi-tiered platform with the operators working on the middle tier. The middle tier also comprised video monitors and seats for accommodating long-length tools. The underwater tier accommodated equipment, i. e. a tilter for aluminum barrels and sets for canisters and SRW containers.
A separate shielded room was available for the fully automated cropping operations with the reactor channels. The operations were monitored from the operator's room that accommodated video monitors, control units for the radiation monitoring system, and communication equipment.
More than 150 types of specialized equipment – from relatively simple long-length grapples of different designs to sophisticated automated equipment electric and pneumatic units – were developed for handling the SFAs and canisters.
Prior to loading into shipping casks, the SNF canisters moved onto racks underwater. A system for water purification from cesium-137 maintained the allowed volumetric water activity during interim SNF storage in the ventilated canisters.
The SNF handling and loading in the SKODA VPVR/M cask required the development of a self-balancing grapple to handle the canisters regardless of their weight.
The SNF loading into the TUK-19 cask was done through a transfer cask designed under the BBR-S SNF removal project (Romania) and adapted for operation at the RA reactor facility.
The repackaging campaign for the damaged RA SNF took the Sosny and Vinca staff a year and a half. Over that period, no incidents happened to cause the personnel overdose or a radioactive release into the environment. The actual individual radiation doses were ten times lower than the values allowed by Russian and Serbian standards and regulations.
The Sosny staff developed the transit route for the spent fuel from Serbia, taking into account its feasibility, safety, and cost-effectiveness. The selected route was supported by all necessary authorizations, i.e. Russian certificates for the package design and transportation endorsed in Serbia, Hungary, and Slovenia, and licenses for the transit through Hungary and Slovenia. The multimodal transportation of the spent fuel was by road, rail, and sea.
In December 2010, Russia received nearly 2.5 tons of the spent fuel. This event evoked a broad response and appraisal of the international community.
Nuclear & Enviromental Safety, No. 1, 2011: Defective spent fuel management at the Vinca Institute
Nuclear & Enviromental Safety, No. 1, 2011: Serbia: Complex Project, Long Transport Route
BBC - News Europe: A secret journey to take Serbian nuclear fuel to safety
BBC - News Europe: Inside Serbia's decommissioned Vinca nuclear facility
IAEA.Org - Top Stories & Features: Massive Operation Safely Secures Serbian Nuclear Fuel in Russia
IAEA.Org - Video Clips: Vinca - Nuclear Fuel Leaves Serbia
IAEA.Org - Top Stories & Features: Q&A: Fuel Repatriation Project from Vinca Institute
IAEA - A newsletter of the Division of Nuclear Fuel Cycle and Waste Technology. Vol.7,No.1,May 2011
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