Effect of the VVR-SM neutron spectrum on the radioactivity and color of natural topazes

Abstract

The neutron flux density from 0.025 eV to 12 MeV has been measured experimentally in all channels of the VVR-SM core by the activation method using threshold monitors (Au, Ni, Fe. Ti, Mg, Y). Comparing with a calculation of the neutron flux density at different energy using the IRT-2D computer code showed agreement to within 5%. The distribution of the neutron fluxes and spectra in the core, which is of practical utility for radiation technologies, was obtained. A series of irradiations has been conducted and experimental dependences of the irradiation time on the channel position in the core as well as on the size of the stones for obtaining a standard light blue and dark blue color have been obtained. The irradiation conditions making it possible to lower the induced radioactivity of the minerals three-fold as a result of increasing the ratio of the fast to thermal neutron fluxes are found.The main parameters characterizing research reactors are the neutron flux density in the core and the neutron energy spectrum. The flux density of the main neutron energy groups in the experimental channels of water moderated and cooled reactors is of great interest for practical applications of activation analysis, radiation technology, as well as testing of different materials and semiconductor devices for radiation resistance of their functional characteristics. In this connection, the prime problem is finding the distribution of the neutron flux and spectrum over the channels inside the core of the reactor; the difficulty is that it is impossible to detect neutrons directly and determine their energy.It is known that the thermal neutron flux density can be determined from the (n, γ) reaction products, which are formed when a monitor is irradiated, as the difference of the indications of a counter without and with a filter. Threshold reactions are used to recover the fast-neutron spectrum. Since the differential measurements of a neutron spectrum are difficult to perform, and there is no need for them in analytical measurements, ordinarily the integral fluxes of neutrons above some threshold value are evaluated.The structural features of some irradiation channels in research reactors make it impossible to determine the neutron flux experimentally and to reconstruct the neutron energy spectrum. In such cases, these parameters are determined by, for example, solving a system of differential equations governing diffusion [1]. Several types of applied programs are available for calculating the neutron flux density. A program for calculating the neutron flux density in three-dimensional space by the Monte Carlo method has been developed at the Los Alamos National Laboratory (USA) [2]. This program is considered to be universal and is the only program that takes account of published data on neutron-physical interaction constants for neutrons interacting with different atoms at different energies as well as the energy spectrum of neutrons formed as a result of the fission of 235 U nuclei in fuel. In addition, it permits setting t...

Optimization of conditions for topaz irradiation in the WWR-K reactor

“…In recent years, radiation treatment of semiprecious stones, in particular, topaz based on research reactors, has been actively developed as one of the methods for radiation processing of materials [1][2][3][4][5][6][7]. This is due to the fact that most of the semiprecious stones mined are colorless, as a result of which they have practically no jewelry value.…”

“…The presence of such induced activity leads to an increase in the time of sedimentation of stones after irradiation, which is a negative effect. Based on this, it is necessary to create conditions in the irradiation position for effective Optimization of conditions for topaz irradiation in the WWR-K reactor coloring of topazes (fast "hard" neutron spectrum) and minimizing the activation of impurities [3,5,6]. Another important factor in topaz irradiation is the irradiation temperature, since at high temperatures (>200°C), stones crack and/or defects in the lattice anneal, which leads to a change in the optical and mechanical properties of topaz [1,7].…”

Investigation of Neutron-Physical Characteristics of the Irradiation Capsule Designed for Radiation Coloring of Topaz in the WWR-K Reactor

“…Такая активация радионуклидов приводит к увеличению времени охлаждения/отстоя камней и соответственно к увеличению времени оборота камней (время поставки Заказчику). [2][3][4][5].…”

Computational Study of Radiation Characteristics in the Niche of the Experimental Devices of the WWR-K Reactor

“…The scope of such technologies is very wide. For example, the production of radioisotopes for medicine [1][2][3][4][5][6], radiation coloring of semiprecious stones for the jewelry industry [7][8][9][10], neutron transmutation doping of semiconductors for the electronics industry [11][12][13][14], and radiation treatment of seeds for the agricultural industry [15][16][17]. Nuclear and radiation technologies are implemented based on nuclear and electrophysical installations, in particular, on the basis of research reactors.…”