Radiation Protection Experience in RA Heavy Water Research Reactor Important for Decommissioning

The RA reactor has been in service since the end of 1959. The beginning of the eightieth using of the reactor was interrupted because of some irregular deposits on the fuel elements in the core. Since that time, for about 20 years, the reactor has not been in service and is now being prepared for decommissioning. There have been no serious accidents to the RA reactor during the operation period, but a few small accidents or incidents, which affected the reactor systems and higher exposure of personnel. These incidents were: contamination of the heavy water cooling system by 60Co; flooding of a few hundred liters of heavy water from the heavy water cooling system; the first and single case of fuel element failure in the reactor core. A specific accident called “phantom”; and finally, some irregular deposits on the fuel elements inside the reactor core that were registered. In this paper more detailed data is given on the above mentioned accidents or incidents, their consequences on the reactor systems and personnel and countermeasures taken for reducing danger radioactivity. According to the opinion of the author, these data and lessons learned would be very interesting in general, and especially, for radiological characterization, as one of the first steps in the process of reactor decommissioning.