Victor Potapov

A scintillation γ-ray detector based on a solid-state photomultiplier

A scintillation detector based on a silicon photodetector of a new type—a solid-state photomultiplier—and a single-crystal CsI(Tl) scintillator was investigated. The effect of temperature on the low-energy detection threshold and the energy resolution of the detector and the influence of the radiation level on the detector efficiency (i.e., the influence of the counting rate of the distortion in the recorded spectrum shape) were estimated. A mathematical model of the detector was developed in order to assess its parameters.

A dip detector for in situ measuring of /sup 137/Cs specific soil activity profiles

A field method for measurement of Cs-137 contamination depth profiles is described. The method is based on the use of a collimated dip detector created as a gamma-ray probe: CsI(Tl) scintillating crystal + PIN photodiode + front-end electronics. The presented method allows determination of specific activity distribution with vertical spatial resolution of 5 cm. Exposure time for one point in the distribution profile is less than 180 s if the level of specific activity is more than 50 Bq/kg. This method may be applied for efficient and quick inspection of a contaminated rivers flood planes in areas with leakage of radioactive wastes. Application of the method for such a task gives an effective solution to obtain qualitative and quantitative characteristics of contamination.

Method to improve angular resolution of portable gamma camera with pinhole collimator

We have developed a method to restore the image obtained by the pinhole camera, which allows to increase the angular resolution by about 3-4 times and to obtain uniform sensitivity in the all field of view without a noticeable increase in noise in the gamma-ray image. The method is based on the use of the inverse problem solution for finding the distribution of incident photons with the measured apparatus functions of the camera.

Environmental monitoring using large-volume CsI(Tl) scintillation counters

The new scintillation detectors, CsI(Tl) + Si PIN photodiode, were developed in the Kurchatov Institute. The current state of the developed spectrometric probes are large volume (10-300cm3) scintillation detectors intended for gamma-ray spectroscopy. These detectors consist of a spherical CsI(Tl) crystal packed in MgO powder within a cylindrical aluminum housing and a Hamamatsu photodiode. Environmental devices based on the above probes uses methods of field spectrometry. They include spectrometric electronics and algorithms for spectra processing to obtain particular characteristics of environmental radioactivity or radioactive contamination. The description of measurement techniques used with devices, their performance parameters and results of their practical applications are presented.

The image processing for improvement of angular resolution and sensitivity of the portable gamma camera with medipix detector

We consider the special treatment of the gamma-ray images obtained by a portable gamma cameras with detector Medipix. The processing of gamma images was conducted to improve the angular resolution using the developed iterative method. The elimination of muon tracks in the shadow patterns to increase the sensitivity was considered also.

Extra-light gamma-ray imager for safeguards and homeland security

Gamma-ray imaging is the most important way to identify unknown gamma-ray emitting objects in decommissioning, the solving the security tasks, overcoming of accidents. Over the past two decades the systems for producing of gamma images in these conditions became more or less portable devices. However, in recent years, these systems have become converted into the hand-held devices. This is very important, especially in emergency situations, and measurements for safety reasons. We describe the first integrated handheld instrument for emergency and security applications. The device is based on the coded aperture image formation, position sensitive gamma-ray (X-ray) detector CdTe-Medipix2 (detectors produces by X-ray Imaging Europe) and tablet computer. The development was aimed at creating a very low weight system with high angular resolution. We present some sample gamma-ray images by camera. Main estimated parameters of the system are the following. The field of view video channel ~ 49°. The field of view gamma channel ~ 30°. The sensitivity of the system with a hexagonal mask for the source of Cs-137 (Eγ = 662 keV), is in units of dose D ~ 30 μR. This option is less then order of magnitude worse than for the heavy, non-handheld systems (e.g., gamma-camera Cartogam, by Canberra.) The angular resolution of the gamma channel for the sources of Cs-137 is about 1.20.

Application of Underwater Spectrometric System for Survey of Ponds of the MR Reactor (NRC Kurchatov Institute)

The underwater spectrometric system for survey the bottom of material science multi-loop reactor MR ponds was elaborated. This system uses CdZnTe (CZT) detectors that allow for spectrometric measurements in high radiation fields. The underwater system was used in the spectrometric survey of the bottom of the MR reactor pool, as well as in the survey located in the MR storage pool of highly radioactive containers and parts of the reactor construction. As a result of these works irradiated nuclear fuel was detected on the bottom of pools, and obtained estimates of the effective surface activity detected radionuclides and created by them the dose rate.Copyright

Characterisation of MR Reactor Pond in NRC “Kurchatov Institute” Before Dismantling Work

In this work complex α-, β-, γ-spectrometric research of water, bottom slimes and deposits on walls of the reactor pond and the storage pond of the MR reactor was made. Identify, that the main dose forming radionuclide, during dismantling work on the reactor MR, is Cs-137. It is shown, that specific activity of radionuclides in bottom slimes considerably exceed specific activity of radionuclides in water from ponds, and near to high level radioactive waste. It is detected that decreasing the water level in reactor ponds on 1m, increase the exposure dose rate at a distance 1m from the pond in 2 times. The observed increase in exposure dose rate can be explained by contribution on dose rate the cesium-137 deposed on walls of the storage pond. Effectiveness of cleaning of walls of the pool of storage from deposits by a water jet of high pressure is investigated.Copyright

The Simulation of Decontamination Works in Premises of the Research Reactor in NRC “Kurchatov Institute”

Application of remote sensing methods using a spectrometric collimated system allows obtaining information about features of a formation of radiation fields in contaminated premises. This information helps in a preparation of a phased plan for dismantling of contaminated equipment. When the survey of technological premises of the research reactor at the Russian Research Centre “Kurchatov institute” was conducted the remote controlled collimated spectrometric system was used [1]. With its help the scanning of surveyed premises were carried out. As a result of this work, the distribution pattern of radionuclides activity was restored. The simulation of decontamination works was carried out and maps of the distribution of activity and dose rate for surveyed premises were plotted and superimposed on its photo for situations before and after decontamination. The use of obtained results will allow significantly reduce radiation dose for staff at work on dismantling.Copyright

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

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.Copyright