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Information × Registration Number 0225U005242, (0124U002048) , R & D reports Title Rare nuclear processes in nuclides of natural radioactive series popup.stage_title Період напіврозпаду 214Ро Head Kasperovych Dmytro V., Кандидат фізико-математичних наук Registration Date 29-12-2025 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 New experimental values of the absolute intensities of γ-rays accompanying the decay of 235U and 231Th were obtained on the basis of high-statistics measurements of a certified U3O8 sample enriched in 235U. Precise efficiency calibration of the detection system was performed, and summing effects were taken into account. The high exposure and the use of absorbers minimized the contribution of cascade summing, which could have led to overestimated intensities for certain transitions in previous studies. The intensities of the transitions with energies 142.40 keV, 182.1 keV, and 291.2 keV were for the first time constrained at the level of (10^–2–10^–5)%. Several other transitions were found to be by factors of 3.2–2.8·10^4 weaker than recommended intensities. The transitions at 179.297 keV and 428.71 keV were observed for the first time. A search for spontaneous fission of plutonium and americium isotopes was carried out using a spectrum from the IAEA open database, obtained in 2015 for a 6.6 g certified plutonium oxide sample (HPGe, 41.7 h). No peaks attributable to fission products of 238–242Pu or 241Am were detected, and lower limits were set for the partial half-lives of these processes. In several cases, the obtained limits exceed theoretical predictions for cold-fission channels. The feasibility of high-precision determination of the half-lives of short-lived α-active nuclides of the uranium–thorium decay chains has been demonstrated using a gadolinium orthosilicate scintillation crystal. Owing to its internal radioactive contamination, favorable scintillation properties, and the application of time-amplitude analysis, decay curves were obtained for event chains with time intervals ≳0.2 μs. Based on data measured in the Solotvyno underground laboratory, preliminary half-life values were determined for 214Po, 215Po, 216Po, 219Rn, and 220Rn; for 216Po, the obtained value of 142.6(14) ms exceeds the currently recommended one in terms of statistical precision. Product Description popup.authors Anton V. Rudakovskyi Volodymyr R. Klavdiienko Nazar V. Sokur popup.nrat_date 2025-12-29 Close