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The emergence of powerful sources of ionizing radiation, the needs of nuclear energy, technology and medicine, as well as the need to develop reliable methods of protection against the harmful effects of penetrating radiation stimulated the development of such branches of science as radiation chemistry, radiation biology, radiation medicine. When an organic dye solution is exposed to ionizing radiation, it irreversibly changes color. As a result, the absorbed dose can be determined. The processes of interaction of neutron fluxes with an aqueous solution of an organic dye methyl orange (МО) – C14H14N3О3SNa, containing and not containing 4% boric acid, have been investigated. The work was carried out on a LINAC LUE-300 at NSC KIPT. A set of tungsten plates was used as a neutron-generating target. The electron energy was 15 MeV, the average current was 20 μA. The samples were located behind the lead shield and without it, with and without a moderator. Using the GEANT4 toolkit code for this experiment, neutron fluxes and their energy spectra were calculated at the location of experimental samples without a moderator and with a moderator of different thickness (1-5 cm). An analysis of the experimental results showed that when objects without lead shielding and without a moderator are irradiated, the dye molecules are completely destroyed. In the presence of lead protection, 10% destruction of the dye molecules was observed. When a five-centimeter polyethylene moderator was installed behind the lead shield, the destruction of dye molecules without boric acid on thermal neutrons was practically not observed. When the fluxes of thermal and epithermal neutrons interacted with a dye solution containing 4% boric acid, 30% destruction of dye molecules was observed due to the exothermic reaction 10B (n, α). The research has shown that solutions of organic dyes are a good material for creating detectors for recording fluxes of thermal and epithermal neutrons. Such detectors can be used for radioecological monitoring of the environment, in nuclear power engineering and nuclear medicine, and in the field of neutron capture therapy research in particular.

The processes of interaction of an aqueous solution of an organic dye: methylene blue (MB)  C16H18N3SCl with gamma quanta and electrons were investigated. A model has been developed and the passage of electrons with an energy of 15 MeV through tungsten layers with a thickness of 1…8 mm has been simulated. Based on the simula-tion results, a number of experiments were carried out. Analysis of the calculated and experimental data showed that one incident electron destroys 4 times more dye molecules than one incident gamma quantum.

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We review the current status of the development of sources of epithermal neutrons sources based on reactors and accelerators for boron neutron capture therapy (BNCT), a promising method of malignant tumor treatment. The scheme is proposed of the source prototype for the production of thermal and epithermal neutrons using the delayed neutrons generated with help of linear electron accelerator at the target containing the fissile material. The results of an experiment are presented in which the half-life curves of radioactive nuclei formed during fission and emitting delayed neutrons are measured. It is shown that an activated target containing fissile material is a compact small-sized source of delayed neutrons. It can be delivered to the shaper, where, using a moderator, an absorber, and a collimator, neutrons of thermal or epithermal energies are formed over a certain period of time, after which this target is sent to the activator, and another target comes in its place. Thus, a pulsed neutron flux is formed. Such a neutron beam can be used in nuclear medicine, in particular, in neutron capture therapy in the treatment of cancer. An important task in the implementation of neutron capture therapy, when irradiating patients, is to control both the intensity and the energy spectrum of the neutron flux. To solve this problem, an earlier developed activation-type neutron ball spectrometer can be used, which will allow optimization of various parameters of the shaper, collimator and filters in order to obtain the most powerful neutron fluxes.