The MCNP5 computer code with the ENDF/B6 neutron data library is validated for problems which are of current importance at the Russian Federal Nuclear Center -All-Russia Research Institute of Technical Physics. Comparative calculations performed with the MCNP5 code and its preceding version MCNP4c are identical within the limits of computational error. This confirms that the MCNP5 code can be used instead of the previous versions.
Technical Physics [1]. However, this method does not permit identifying either the material itself or its isotopes. The identification can be made from measurements of the spectrum of the γ rays emitted by the material in the energy range 0.1-1 MeV [2]. Methods for detecting and identifying γ-emitting fissioning material and its isotopes, including under field conditions, on the basis of analysis of the measurements of the neutron and/or γ rays in wells drilled near the proposed location of the material have been developed at the Russian Federal Nuclear Center -All-Russia Scientific-Research Institute of Technical Physics. In the mathematical simulation of the experiment, and choosing the form of the material and the intensity of the radiation, the PRIZMA.D program with the BAS library and the MCNP program with the ENDF-BV library, which were verified on calibrated experiments, were used to obtain the best agreement between the computed and experimental dependences obtained by detecting neutrons and γ rays.The calibration experiments (2001 and 2003) on detecting fissioning material in soil were performed under laboratory conditions using measurement cavities with sand simulating "infinite" soil. In the experiments, the density of the sand was measured, the chemical composition of the sand was investigated, the water content was determined, and the measurement errors were estimated. The γ-ray source was assembled from several small objects of fissioning material. A γ spectrometer with a coaxial semiconductor detector GX3019 made of 50 × 50 mm germanium with energy resolution 0.8 keV/channel (E γ = 122 keV), relative detection efficiency 32%, and a γ spectrometer with a scintillation detector with 40 × 40 mm NaI(Tl) single crystal with energy resolution ~10% in the energy range 350-450 keV (BDÉG-20R), and an analyzer based on an ATsP-8K-2M spectrometric amplitude-to-digital converter, were used for detection.The semiconductor spectrometer gives better energy resolution and makes it possible to detect and identify fissioning material at large distances, but it requires expensive hardware and software, and the detector must be cooled with liquid nitrogen. The scintillation spectrometer with a NaI(Tl) crystal makes it possible to use relatively simple hardware in a wide temperature range, it is smaller and can be used in small wells, but its energy resolution is worse. To search for fissioning material under field conditions, the neutron method and both spectrometers should be used; the scintillation spectrometer is best used for rapid detection of anomalies in the background radiation and the semiconductor spectrometer is best used for careful identification of these anomalies. When the counting rate of the scintillation detector exceeds the background in the
A method is proposed for identifying a cylindrical case with a jacket containing 17 spent fuel assemblies from the AMB reactors at the Beloyarskaya nuclear power plant on the basis of measurements of the radiation characteristics in lateral surface of the jacket opposite the fuel assemblies in the outer and inner rows. Computational validation using the PRIZMA and MCNP computer codes is given for the method. It is shown that the collection of signals from detectors is specific to each jacket, and this makes it possible to use it as an identifying indicator.The No. 1 power-generating unit at the Beloyarskaya nuclear power plant was stopped in 1981 and the No. 2 unit in 1989. The spent fuel of the AMB reactor was partially removed and shipped to the Industrial Association Mayak, partially loaded into 17-and 35-place jackets and placed into storage in a holding pond near the reactors. The problem of further longterm storage of the fuel has become acute because it is impossible to repair the facing of the ponds without unloading them and because the jackets undergo substantial corrosion as a result of being submerged in water for a long time. In connection with the transition to dry storage, the spent fuel must be removed from the storage sites near the plant and transferred either to the Industrial Association Mayak for reprocessing or to the Integrated Mining and Chemical Plant in Krasnoyarsk for longterm storage and subsequent reprocessing.Each 17-place jacket consists of a set of 17 steel tubes (Fig. 1). A single spent fuel assembly, 13.5 m long, is placed inside each tube. The construction and composition of each tube are shown in Fig. 2 [1]. The relative arrangement of the tubes is fixed with the aid of several steel tubular separation boards.To place the jacket with the fuel into long-term storage, it is removed from the pond and placed into a steel cylindrical case whose wall is 1 cm thick. The cylindrical case must be equipped with an individual indicator so that it can be identified even after being in storage for several decades. The possible solutions where paint, engraving, securing plates with test or bar code, and so forth are used are simple, inexpensive, and certainly should be used, since they make it possible to identify a cylindrical case for at least the first 20-30 yr of storage. After this time, because of corrosion, these methods of identification can become less reliable and ultimately useless.In the present article, we propose a method for identifying the jackets on the basis of measurements of n and γ radiation from the spent fuel assemblies inside a jacket and we provide computational validation. For identification, n and γ radi-
The mass of a fissioning material and its distribution in soil can be estimated by analyzing the results of the detection of neutron and/or γ radiation in wells drilled in a clean zone near the assumed location of the material [1]. The PRIZMA.D program [2] with the BAS library [3] and the MCNP program [4] with the ENDF-BV library, which were verified on calibration experiments, are used in the mathematical simulation of an experiment, choosing the forms of the material and the power of the radiation to obtain the best agreement between the computational and experimental dependences obtained when working under field conditions.Calibration experiments when working out the procedure were performed in 2001 and 2003 under laboratory conditions with a point source -an IBN-8 constant Pu-Be source with neutron yield ∼1.6·10 6 sec -1 or a small object made of the fissioning material. The main purposes of the experiment were to check the utility of the method for detecting fissioning materials in soil, on the basis of neutron detection, and obtain experimental data suitable for verifying the computational procedures. Sand with a known chemical composition was used as the soil.Experimental Arrangement. The experiments were performed on a 175 × 80 × 114 cm measurement volume with a well simulator in the form of an aluminum tube with outer diameter 95 mm and wall thickness 7.5 mm, inside which a SNM-18 neutron detector was positioned (Fig. 1). The tube was placed perpendicular to the plane of the bottom along the entire height of the container. Two tubes, made of aluminum alloy with one tube placed inside the other, were laid in the central plane of the container. The outer stationary tube functioned as a casing; its outer diameter was 38 mm and its wall thickness was 2 mm. A second tube, with outer diameter 30 mm and wall thickness 1.5 mm, was placed inside the casing tube. A capsule with the source or an object made of the fissioning material was secured at the center of the inner tube. When the inner tube is moved only the distance between the capsule and the detector changes; the rest of the configuration remains unchanged.To increase the water content, sand was poured from the measurement container into two boxes, water was added, and the mixture was manually mixed, after which it was reloaded, taking samples to determine the water content. Three series of measurements were performed with water content in the sand 0.3, 3.8, and 8.1 mass% (dry, moist, and wet sand) and density 1.39, 1.45, and 1.47 g/cm 3 , respectively. A sample of hard rock (stone) with known chemical composition and water content and a cavity -air and water -were used as nonuniformities; they were buried in sand near the detector. The cavity was made from a 1.5 liter household plastic container. Water was poured into and out of the cavity along two hoses, so that its position during the experiments remained unchanged for one load of sand.The experiments were performed in the building where the fissioning material is stored. Despite the thickness, the co...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.