Abstract
In 2003, the work on environmental rehabilitation of the former coastal technical base of the Russian Navy in Gremikha town, with technical and financial support of the State Atomic Energy Corporation “Rosatom” and the French Alternative Energies and Atomic Energy Commission had begun. In 2017, the task of searching, characterization and packaging in transport containers for export to the long-term storage of high-level waste containing 152Eu was set as part of this program. These wastes were presented as fragments of reactor control and safety system rods of first generation nuclear submarine reactors and were placed in temporary storage containers mixed with other radioactive waste and construction garbage on the territory of the Gremikha branch of the North-West Center “SevRAO”. To accomplish the task, the spectrometric system “Gamma-Pioneer” was developed and made at National Research Center “Kurchatov Institute”. The system consist of a collimated spectrometric gamma-ray CdZnTe detector 500 mm3 volume, a dosimeter for continuous measurement of ambient equivalent dose rate at the instrument location and a color video camera with zoom lens. The device is placed in a protective frame and installed as an attachment implements on robot Brokk-90. Communication between the measuring system and the control computer is carried out using USB extender and 100 meters cable. The video camera is connected to the control computer via Ethernet. To search for the most active sources of gamma radiation, an equivalent dose rate calculation program using the results of measured instrumental spectra was developed. The characterization of the extracted fragments was carried out by activity evaluation of the main radionuclides polluting the samples under investigation. The paper describes design and operating principles of the system, as well as methods for the equivalent dose rate calculation and the activity evaluation of the fragments of reactor control and safety system rods based on spectral measurements obtained using the developed radiometric system
Highlights
Environmental rehabilitation of the former coastal technical base of Russian Navy in Gremikha town is currently one of the largest projects addressed to solve the “nuclear legacy” problems in the North-West region of Russia
In concrete containers and in two packages with radioactive waste highly active sources with 152Eu lines in spectra were placed. This suggest that the founded sources are fragments of reactor control and safety system rods of first generation nuclear submarine reactor [2]
The main objects of search were reactor control and safety system rods stored in abnormal conditions in temporary packages and concrete containers in building 19 and in the open area of temporary storage of solid radioactive waste (SRW)
Summary
Environmental rehabilitation of the former coastal technical base of Russian Navy in Gremikha town (today, this is Gremikha branch of the North-West Center “SevRAO” branch of FSUE “RosRAO”, the closed city Ostrovnoy) is currently one of the largest projects addressed to solve the “nuclear legacy” problems in the North-West region of Russia. In conditions of an increased radiation situation, in building 19 and in the open site for storage of spent nuclear fuel (SNF) and solid radioactive waste (SRW), remote identification of γ-radiation sources was carried out. In concrete containers and in two packages with radioactive waste highly active sources with 152Eu lines in spectra were placed. This suggest that the founded sources are fragments of reactor control and safety system rods of first generation nuclear submarine reactor [2]. The main objects of search were reactor control and safety system rods stored in abnormal conditions in temporary packages and concrete containers in building 19 and in the open area of temporary storage of SRW. For the searching and sorting of radioactive waste by category and activity, NRC “Kurchatov institute” developed the spectrometric system “Gamma-Pioneer”
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