The behavior of structural materials of nuclear and fusion reactors during operation largely determines their safe and economical work. Structural materials of nuclear and fusion reactors are operating under conditions of interaction with various chemical active elements (gases, vapor-gas mixtures, fission products, etc.) in a wide temperature range; they are subject to high requirements in terms of their thermal and corrosion resistance. This paper presents the new methodology of complex studies on structural materials corrosion resistance of nuclear and fusion reactors with different gases and vapor-gas mixtures by thermal-gravimetric analysis (TGA), differential-scanning calorimetry (DSC) and mass spectrometry (MS) methods simultaneously.

Radiation-induced attenuation (RIA) at wavelength λ=1.55 μm as well as the RIA spectra were investigated in optical fibers during and after irradiation at the IVG.1M nuclear reactor (Republic of Kazakhstan). The fibers studied were single-mode at λ=1.55 μm, had an undoped-silica-core and an-F-doped-silica cladding (”pure-silica fibers, PSFs”), and were provided by different manufacturers. In addition to five PSFs, a single-mode revolver hollow-core fiber was also studied. The PSFs had different coating materials: polyimide, copper, or aluminum. All fibers were exposed to three runs of reactor irradiation at enhanced temperature (155-355 °C) so that by the end of the 3rd run, the fast-neutron fluence amounted to Φ=4.46∙1017n/cm2 and γ-dose to D=2.91∙107 Gy. The total induced loss at λ=1.55 μm was found to be composed of 1) RIA, 2) bending loss (BL), caused by thermal expansion of the copper cylinder the PSFs were wound on, and 3) thermo-induced microbending loss (ML) in Cu-coated PSFs. At the end of the irradiation campaign, the net RIA in PSFs proved to lie in the interval of 0.12-0.16 dB/m, which appears to be admissible to intrareactor transport fibers. It was confirmed that long-wavelength RIA tail is the only RIA origin at λ=1.55 μm in PSFs in such strong radiation fields. The hollow-core fiber was found to feature zeroth RIA throughout the campaign.

Almost all experimental studies of the characteristics of nuclear-excited plasma formed by excitation of gaseous media with nuclear reactions products are conducted at pulsed nuclear reactors that differ in the composition and design of the core, the duration, flux and fluence of the neutron pulse, the impulse repetition frequency, the volume and configuration of the irradiation space. This paper presents a description of the experimental (methodical and hardware) base of the National Nuclear Center of RK (Kurchatov) to conduct experiments on studying the threshold characteristics of laser action at the p-s-transition of noble gas atoms upon ⁶Li(n,α)³H nuclear reaction products excitation in conditions of a pulsed nuclear IGR reactor. To conduct in-pile reactor experiments, a special experimental facility was developed and constructed. The experimental facility functionally includes: in-pile experimental device, a gas–vacuum system, information and measurement system consisting of a system for registering and controlling the temperature of the device housing, and a system for registering optical radiation. The paper also briefly describes the methodology of in-pile reactor experiments on the pulsed nuclear reactor.

The luminescence of Kr-Xe, Ar-Kr, and Ar-Xe mixtures was studied in the spectral range 300–970 nm when excited by ⁶Li (n, α)³ H nuclear reaction products in the core of a nuclear reactor. Lithium was deposited on walls of experimental cell in the form of a capillary-porous structure, which made it possible to measure up to a temperature of 730 K. The temperature dependence of the radiation intensity of noble gas atoms, alkali metals, and heteronuclear ionic noble gas molecules was studied. Also, as in the case of single-component gases, the appearance of lithium lines and impurities of sodium and potassium is associated with vaporization during the release of nuclear reaction products from the lithium layer. The excitation of lithium atoms occurs mainly as a result of the Penning process of lithium atoms on noble gas atoms in the 1s states and subsequent ion-molecular reactions. Simultaneous radiation at transitions of atoms of noble gases and lithium, heteronuclear ion molecules of noble gases allows us to increase the efficiency of direct conversion of nuclear energy into light.

Research results of luminescence spectra of noble gases and Ar–Xe, Ar–Kr, and Kr–Xe mixtures under the excitation by products of nuclear reaction in the core of a stationary nuclear reactor with 0.87 × 10¹⁴ n/cm²s thermal neutron flux are described in the article. The emission spectra of noble gases are similar to the obtained spectrum under the excitation by the ⁴⁰Ar⁺⁷ ion beam from the DC-60 accelerator. Bands in spectra of the binary mixtures of noble gases are connected with the radiation on heteronuclear ion molecule transitions. The appearance of the lines of alkali metal atoms at the temperature increase of gas chamber is explained by sputtering of the lithium layer via nuclear reaction products as well as ionized and excited particles of the buffer gas.

The paper describes the technology of creating a surface source of high-energy tritium ions and alpha particles formed as a result of a nuclear reaction of the interaction of the ⁶Li isotope with thermal neutrons ${\hspace{0.17em}}_3^{6}Li+n\to {\hspace{0.17em}}_2^{4}He\left(2.05MeV\right)+{\hspace{0.17em}}_1^{3}H\left(2.73MeV\right)$. Different design versions of the developed irradiating ampoule devices are presented, and a description of the experimental reactor facility is given. The paper also describes the scheme of reactor experiments to study the spectral-luminescent characteristics of nuclear-excited plasma of argon. The results of test experiments are presented, and they show the applicability of high-energy tritium ions and alpha particles for nuclear excitation of luminescence of inert gas mixtures.