Source for In Situ Positron Annihilation Spectroscopy of Thermal—And Hydrogen-Induced Defects Based on the Cu-64 Isotope

This work aims to investigate the 64Cu isotope applicability for positron annihilation experiments in in situ mode. We determined appropriate characteristics of this isotope for defect studies and implemented them under aggressive conditions (i.e., elevated temperature, hydrogen environment) in situ to determine the sensitivity of this approach to thermal vacancies and hydrogen-induced defects investigation. Titanium samples were used as test materials. The source was obtained by the activation of copper foil in the thermal neutron flux of a research nuclear reactor. Main spectrometric characteristics (e.g., the total number of counts, fraction of good signals, peak-to-noise ratio) of this source, as well as line-shaped parameters of the Doppler broadening spectrum (DBS), were studied experimentally. These characteristics for 64Cu (in contrast to positron sources with longer half-life) were shown to vary strongly with time, owing to the rapidly changing activity. These changes are predictable and should be considered in the analysis of experimental data to reveal information about the defect structure. The investigation of samples with a controlled density of defects revealed the suitability of 64Cu positron source with an activity of 2–40 MBq for defects studies by DBS. However, greater isotope activity could also be applied. The results of testing this source at high temperatures and in hydrogen atmosphere showed its suitability to thermal vacancies and hydrogen-induced defects studies in situ. The greatest changes in the defect structure of titanium alloy during high-temperature hydrogen saturation occurred at the cooling stage, when the formation of hydrides began, and were associated with an increase in the dislocation density.

Structural Changes in Concrete under the Influence of Reactor Spectrum Neutrons

The paper considers structural changes in the concrete composition that occur under the influence of neutrons of the reactor spectrum, using the example of the IR-100 research nuclear reactor, taking into account its real time and operating conditions. Thus, taking into account the energy output, power operation modes, and neutron flux density in the core, over time, nuclides that are not characteristic of the original composition of the concrete component are formed in the nodes of the crystal lattice. However, these changes do not lead to significant structural changes.

Reevaluation of Spectral Parameters and Neutron Fluxes in IC-7 Irradiation Channel of TRIGA MARK I IPR-R1 Research Nuclear Reactor

The core configuration of the TRIGA MARK I IPR-R1 nuclear research reactor, Brazil, has been modified six times since the first criticality and the neutron fluxes have been determined using experimental and semi theoretical methodologies determining the neutron fluxes in different irradiation channels and devices, applying different procedures and materials. This reactor operates at 100 kW, however, after new configuration for 250 kW in 2001, the carousel no longer rotates during irradiations aiming at preserving the rotation mechanism. In 2003, the spectral parameters were determined experimentally by the "Cd-ratio for multi-monitor" in five specific channels aiming at the application of NAA k0-standardized method. The determinations were repeated applying the same procedure in 2016, 2018 and 2019. Values for thermal and epithermal neutron fluxes as well as f and a spectral parameters were determined. The experimental results for CRM BCR-320R were calculated by the k0-method of NAA, using the spectral parameters for irradiation channel IC-7 obtained in 2003, 2016, 2018 and 2019 and evaluated by En-score. The values showed that the differences in the results compared to those in 2003 were lower than 2.5%, inside the uncertainty of the method. It shows that the k0-method installed in CDTN is reliable and useful for various purposes. The results of the spectral parameter f presented small differences, in a period of 16 years, pointing out the stability of operation of the reactor TRIGA MARK I IPR-R1.

HOW TO ISOLATE RADIONUCLIDES? ON THE ELECTROCHEMICAL PURIFICATION OF TECHNOLOGICAL EQUIPMENT FROM RADIONUCLIDE CONTAMINATION — DEVELOPMENT BY CHEMISTS OF THE ACADEMY

Scientists of the V.I. Vernadskii Institute of General and Inorganic Chemistry of National Academy of Sciences of Ukraine developed a method of electrochemical removal of radionuclide contamination from the surfaces of the technological equipment of nuclear power plants. The method was successfully tested at the Chornobyl nuclear power plant and on the Research Nuclear Reactor of the Institute of Nuclear Research of the National Academy of Sciences of Ukraine. Based on the results of the tests, a device for the electrochemical decontamination of metal surfaces of equipment in non-stationary conditions was created and design and technological documentation for its serial production was developed.

The Use of Polycarbonate as Dosimeter of High Doses

Dosimetry of high doses of ionizing radiation is a method widely used not only in the field of basic and applied research but also in various industries. High-dose irradiation is used in the sterilization of foodstuffs and prolongation of their shelf life, sterilization of tools, materials and wastewater, treatment of antiquities attacked by woodworm organisms, biological and genetic research, inhibition of seed germination, and retardation of fruit ripening. Furthermore, it has been applied in radiation resistance testing of materials, defectoscopy, industrial irradiation of materials (e.g., crosslinking and grafting of polymers or gemstone coloring by ionizing radiation), and last but not least, of course, nuclear energetics. In this work, the dosimetric properties of polycarbonate are studied. They are compared with a standardized and certified method using alanine dosimeters. In the case of gammas, the testing was realized for 60Co and neutron radiation was studied in the light water research nuclear reactor (LVR-15).

Probing neutron-hidden neutron transitions with the MURMUR experiment

MURMUR is a new passing-through-walls neutron experiment designed to constrain neutron-hidden neutron transitions allowed in the context of braneworld scenarios or mirror matter models. A nuclear reactor can act as a source of hidden neutrons, such that neutrons travel through a hidden world or sector. Hidden neutrons can propagate out of the nuclear core and far beyond the biological shielding. However, hidden neutrons can weakly interact with usual matter, making possible for their detection in the context of low-noise measurements. In the present work, the novelty rests on a better background discrimination and the use of a mass of a material – here lead – able to enhance regeneration of hidden neutrons into visible ones to improve detection. The input of this new setup is studied using both modelizations and experiments, thanks to tests currently performed with the experiment at the BR2 research nuclear reactor (SCK$$\cdot $$ · CEN, Mol, Belgium). A new limit on the neutron swapping probability p has been derived thanks to the measurements taken during the BR2 Cycle 02/2019A: $$p<4.0\times 10^{-10} \; \text {at 95}\%\text { CL}$$ p < 4.0 × 10 - 10 at 95 % CL . This constraint is better than the bound from the previous passing-through-wall neutron experiment made at ILL in 2015, despite BR2 is less efficient to generate hidden neutrons by a factor of 7.4, thus raising the interest of such experiment using regenerating materials.

The Local Seismoacoustic Wavefield of a Research Nuclear Reactor and Its Response to Reactor Power Level

We describe the seismoacoustic wavefield recorded outdoors but inside the facility fence of the High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory (Tennessee). HFIR is a research nuclear reactor that generates neutrons for scattering, irradiation research, and isotope production. This reactor operates at a nominal power of 85 MW, with a full-power period between 24 and 26 days. This study uses data from a single seismoacoustic station that operated for 60 days and sampled a full operating reactor cycle, that is, full-power operation and end-of-cycle outage. The analysis presented here is based on identifying signals that characterize the steady, that is, full-power operation and end-of-cycle outage, and transitional, that is, start-up and shutdown, states of the reactor. We found that the overall seismoacoustic energy closely follows the main power cycle of the reactor and identified spectral regions excited by specific reactor operational conditions. In particular, we identified a tonal noise sequence with a fundamental frequency around 21.4 Hz and multiple harmonics that emerge as the reactor reaches 90% of nominal power in both seismic and acoustic channels. We also utilized temperature measurements from the monitoring system of the reactor to suggest links between the operation of reactor’s subsystems and seismoacoustic signals. We demonstrate that seismoacoustic monitoring of an industrial facility can identify and track some industrial processes and detect events related to operations that involve energy transport.