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Information × Registration Number 0224U033497, (0124U002048) , R & D reports Title Rare nuclear processes in nuclides of natural radioactive series popup.stage_title Схема розпаду 234Ра. Пошук рідкісних розпадів радіонуклідів природних рядів Head Kasperovych Dmytro V., Кандидат фізико-математичних наук Registration Date 29-12-2024 Organization Institute of Nuclear Research of the National Academy of Sciences of Ukraine popup.description1 The purpose of this work is to study the decay scheme of 234Pa and 234mPa isomers, search for rare nuclear processes in radionuclides of the natural decay chains, precise measurement of the 214Po half-life, as well as the development of metal samples for the experimental search for variations in the decay constants of radionuclides in metal lattices at cryogenic temperatures. Implementation of the project will be following with new results: new or improved half-life limits for radionuclides of the natural decay chains relative to various rare modes of decay; precise values of energies and intensities of gamma transitions in the beta decay of 234Pa and 234mPa; the most accurate value of the half-life of nuclide 214Po. Also, R&D of a metal sample with 226Ra content on the level of background activity, embedded in a metal matrix, will be performed for further investigation of the temperature variation of 226Ra half-life. popup.description2 Several new lower partial-half-life limits are set on different modes of spontaneous-cold-fission process in the uranium nuclides on the level 5.0x10^10- 4.1x10^16 yr, taking into consideration the systematic uncertainties. Five limits for 235U and 238U are higher than the predicted values by a factors 1.6−227. Lower limits on cluster-decay partial half-lives are set for a number of channels on the level of 5.5x10^12−2.6x10^17 yr; particularly, several decay channels have been searched for at the first time. The absolute intensity value of the 387.8-keV gamma transition (0.00326(9)%) in the decay of 235U has been obtained, which is 1–2 orders lower than previous experimental values. Systematic effects that could cause overestimation of the emission intensity have been analysed. It has been noted that significant contributions to the 387.8-keV peak may come from decays of natural radionuclides with similar gamma-ray energies, such as 214Bi, 223Ra, 231Pa, and 234mPa, as well as the summation detection of gamma cascades emitted from the 387.8-keV level de-excitation in 231Th. The contribution of cascade summing in this measurement is estimated to be ~0.1% of the peak area, due to the low detection efficiency for low-energy gamma-rays (0.02% and 0.007%, respectively, for gamma-rays of 202.1keV and 185.7keV). However, in measurements with close geometry and without additional absorbers, the detection efficiency for gamma rays can reach ~1%. In this case, cascade summing constitutes a significant part of the full absorption peak, which could have been the cause of erroneous overestimation of the intensity of the direct transition in previous studies. A technology for preparation of low-activity sources of radium-226 in the metal form incorporated into the crystal lattice of metallic Ga with Hg and Ca admixtures has been developed. These sources will be used to search for a possible dependence of the alpha-decay constant of 226Ra in the metallic matrix on temperature. Product Description popup.authors Klavdiienko Volodymyr R. Rudakovskyi Anton V. Sokur Nazar V. popup.nrat_date 2024-12-29 Close