A. V. Chesnokov

Determination of surface activity and radiation spectrum characteristics inside buildings by a gamma locator

Abstract A gamma locator designed to conduct contamination survey inside buildings connected with nuclear production is developed. The device consists of a detector head and a remote control unit connected with a cable (>150 m). The detector head (200 × 200 × 250 mm 3 ; the weight is nearly 40 kg) is a collimated scintillated gamma detector installed on a scanning unit. The gamma detector is placed in a lead shielding with the collimator having an entrance angle near 10°. The detector head contains a TV camera and laser distance device. The remote control unit provides operation and processing of the acquired information. The gamma detector is based on a system of CsI(Tl) scintillators and an Si photodiode. The detector energy resolution (nearly 9% for radiation of 137 Cs) provides identification of gamma radiating isotopes such as 57 Co, 137 Cs, 40 K, 60 Co, 131 I and 154 Eu. The gamma locator threshold of determination is 250 Bq/cm 2 for a 10 cm 3 scintillator and 137 Cs radiation. The system allows one to measure the effective surface activity density (for 137 Cs radiation) of all building surfaces and to reconstruct an exposed dose rate distribution within the volume of the investigated space.

A gamma locator for remote radioactivity mapping and dose rate control

The automatic system for remote measurements of radiological conditions at territories of rehabilitation activity was developed. The apparatus is realized as computer controlled collimated gamma-locator. The methods of exposure dose rate (EDR) calculation in 3-D space around territory of activity and analysis of relative input of main gamma-sources into EDR are developed. The results of application of the system during rehabilitation activity at RRC Kurchatov Institute for exposure dose rate monitoring and control are presented and discussed.

Calculation of the Equivalent Dose Rate Distribution Using Data Obtained with a γ Locator

A method is presented for calculating the equivalent dose rate for the interior spaces in enclosures. The method uses the results of remote measurements, performed with a γ locator, of radioactive contamination levels. The spectral characteristics of photon radiation are taken into account. The results of a calculation of the equivalent dose rate in the reactor room of the No. 4 unit of the Chernobyl nuclear power plant, which are based on measurements performed in the fall of 1996, are presented as an example.

Distribution of137Cs inventory in the floodplain of the techa river in the muslyumovo village region

Within the Urals Programs of MinChS and in conformance with the findings of the commission in a previous paper, in 1995-1996 a radiation survey and large-scale mapping of the distribution of surface activity (inventory) of 137 Cs in the soil of the Techa River floodplain were carried out in the Muslyumovo village region. This work is a continuation of the large-scale mapping of the contamination of the Techa River floodplain begun in Fall 1994 within the boundaries of population centers using an RKG-09N radiometer (CORAD), which makes it possible to measure the 137 Cs inventory in soil taking into account its penetration depth.

Measurements of photon ionizing radiation fields in the reactor room of the 4th power-generating unit of the chernobyl nuclear power plant

A radiation examination of the reactor room of the damaged fourth unit of the Chernobyl nuclear power plant was performed. The most strongly radiating surfaces were determined. Digital maps of the distribution of the effective surface activity on the inner surfaces of the room were constructed from the measurement results. 4 figures, 1 table, 10 references.

Characteristic features of the137Cs and90Sr distributions in the floodplain of the Techa river near the village of Brodokalmak

Digital maps of the distribution of137Cs accumulation in the soil of the floodplain of the Techa river near the village of Brodokalmak are constructed on the basis of more than 800 field measurements. The total length of the surveyed section is greater than 15 km. The total accumulation and the area of the floodplain, whose contamination corresponds to definite ranges of the surface activity values, are calculated for half-kilometer sections of the floodplain of the river. The specific activity of90Sr in the soil is measured at individual locations and its accumulation for sections of the floodplain near the village of Brodokalmak is estimated from the correlation coefficients. 5 figures, 1 table, 16 references.

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

History of development and application of gamma-ray imagers in Russia since 1986

Abstract Devices for remote mapping of radioactive contamination developed at RECOM Ltd., the daughter institution of Kurchatov Institute, since 1986 are described and typical examples of their application are shown. The following devices are discussed: Spectrum-sensitive collimated devices for mapping of radioactivity on contaminated surfaces – scanning collimated Gamma Locator and device for field 137 Cs contamination mapping – CORAD; devices for gamma-ray imaging – computer-controlled High-Energy Radiation Visualizer (HERV) and Coded Mask Imager.