HLRW Management During MR Reactor Decommissioning in NRC “Kurchatov Institute”

Abstract

A program of decommissioning of MR research reactor in the Kurchatov institute started in 2008. The decommissioning work presumed a preliminary stage, which included: removal of spent fuel from near reactor storage; removal of spent fuel assemble of metal liquid loop channel from a core; identification, sorting and disposal of radioactive objects from gateway of the reactor; identification, sorting and disposal of radioactive objects from cells of HLRW storage of the Kurchatov institute for radwaste creating form the decommissioning of MR. All these works were performed by a remote controlled means with use of a remote identification methods of high radioactive objects. A distribution of activity along high radiated objects was measured by a collimated radiometer installed on the robot Brokk-90, a gamma image of the object was registered by gammavisor. Spectrum of gamma radiation was measured by a gamma locator and semiconductor detector system. For identification of a presence of uranium isotopes in the HLRW a technique, based on the registration of characteristic radiation of U, was developed. For fragmentation of high radiated objects was used a cold cutting technique and dust suppression system was applied for reduction of volume activity of aerosols in air. The management of HLRW was performed by remote controlled robots Brokk-180 and Brokk-330. They executed sorting, cutting and parking of high radiated part of contaminated equipment. The use of these techniques allowed to reduce individual and collective doses of personal performed the decommissioning. The average individual dose of the personnel was 1,9 mSv/year in 2011, and the collective dose is estimated by 0,0605 man×Sv/year. Use of the remote control machines enables reducing the number of working personal (20 men) and doses. X-ray spectrometric methods enable determination of a presence of the U in high radiated objects and special cans and separation of them for further spent fuel inspection. The sorting of radwaste enabled shipping of the LLRW and ILRW to special repositories and keeping of the HLRW for decay in the Kurchatov institute repository.

The CdZnTe Detector with Slit Collimator for Measure Distribution of the Specific Activity Radionuclide in the Ground

“…To measure the distribution of specific activity in the soil, the CdZnTe detector (volume 500 mm 3 SCD move along the hole in the ground with discrete steps and make two measurements in each point. After carrying out measurements, the values of the specific activity of a soil are calculated in specially developed software.…”

“…If we assume that the thickness of the contaminated layer is, for example, 0.2 m, the volume of radioactive waste will be ~ 260 m 3 . Measurement of detailed distribution of specific activity of radionuclides in soil by the area and by depth will allow significantly reduce the amount of the radioactive waste.…”

“…The dismantling of reactor internal constructions was started in 2014. In 2015 the vessel of the MR reactor and the graphite stack of the RFT reactor were dismantled [1][2][3][4][5][6].…”