Advanced Laser-Photoionization Scheme of Separation of Heavy Isotopes in the Gases Separator Devices

An effective approach to determining the parameters of the optimal schemes of the method of laser selective photoionization of atoms (elements and isotopes) with finite ionization due to collisions, ionization by a pulsed electric field, ionization through high (Rydberg) states and narrow autoionization resonances for the separation of heavy isotopes has been proposed. in gas separator devices. On the basis of the theory of optimal control and previously developed quantum models for calculating the characteristics of elementary atomic processes, optimization models of isotope separation are numerically implemented in the scheme of selective laser photoionization with ionization due to collisions in gas mixtures, ionization by a pulsed electric field, autoionization, etc. etc. The data obtained quantitatively confirm the promise of the method of laser photoionization with finite ionization due to collisions, ionization by a pulsed electric field, ionization through high-lying (Rydberg) states and narrow autoionization resonances and give a set of parameters for the desired optimal schemes, in particular, the laser pulse optimal shape for rubidium and uranium isotopes.

Anoxic depositional overprinting of 238U/235U in calcite: When do carbonates tell black shale tales?

The fidelity of uranium isotopes (δ238U) in marine carbonates as a paleoredox proxy relies on whether carbonates can record and preserve seawater δ238U. Although modern carbonate sediments deposited under oxic conditions have been shown to track seawater δ238U, it remains unknown whether this is true for carbonates deposited under anoxic conditions. This is a crucial question because many ancient carbonates were likely deposited or reworked under anoxic bottom waters. To better understand the behavior of uranium isotopes under this scenario, we investigated U isotope geochemistry in the meromictic Fayetteville Green Lake (FGL; New York, USA), where primary calcite is precipitated from oxic surface waters, sinks past the chemocline, and is deposited under anoxic bottom waters. We observed significant depletions of dissolved U concentration (from 2.7 to 0.9 ppb) and δ238U (from –0.55‰ to –0.96‰) below the chemocline in FGL. Parallel with these depletions, δ238U of sediment traps increased progressively from –0.51‰ to –0.16‰, suggesting that U(VI) reduction was occurring in the anoxic water column. Carbonate sediments deposited under anoxic bottom waters were enriched in U by 6–18× compared to primary calcite. Our data suggest that such significant authigenic U enrichments resulted from U(VI) reduction in the anoxic water column and below the sediment-water interface. The δ238U value in the top 0.25 cm of sediments was –0.29‰ ± 0.10‰, overprinting original δ238U in primary calcite (–0.51‰ ± 0.02‰). Future applications of carbonate δ238U as a paleoredox proxy should consider depositional environments (oxic vs. anoxic) of carbonates.

Studying the treatment processes of soil samples from radionuclides

Object of research: Soil samples contaminated with radionuclides and processes for treatment of contaminated soil. The problem to be solved: Isolation of radionuclides from contaminated soil samples by extraction with weak solutions of acids and alkalis. Main scientific results: Treatment of soil samples contaminated with uranyl nitrate using extraction with weak solutions of nitric and hydrochloric acid, caustic sodium and subsequent washing of soil residues with distilled water is effective process and leads to a more than tenfold decrease in the content of uranium isotopes (U238, U235, U234 and U236) in the soil samples. At the same time, there is a decrease in the content of natural radionuclides (Na22, K40, Zn65, Sn113, Sn126) in the extracted soil samples. An increase in their content in the extract of the analyzed soil samples corresponds to a decrease in their content in the residue of the extracted soil samples. The analysis of the values of the decrease in the content of natural radionuclides in the soil contaminated with uranyl nitrate corresponds to the values of the decrease in their content in the identical soil, but not contaminated with uranium isotopes. The combined extraction with weak solutions of acids and alkalis leads to the enrichment of the soil with nitrates and chlorine-containing compounds. The area of practical use of the research results: Subdivisions of the Ministry of Emergency Situations and Chemical Troops specializing in the study of emergencies and natural disasters can use the results of these studies in the elimination of the consequences of global environmental disasters and incidents that pose a threat to the life of the civilian population and the personnel of paramilitary units. Innovative technological product: The proposed method for treatment of soil contaminated with radionuclides makes it possible to more than tenfold reduce their concentration in the soil. Scope of application of an innovative technological product: treatment of contaminated soil in areas affected by nuclear tests or accidents at nuclear power plants.

STUDY OF PURIFICATION PROCESSES OF SOIL CONTAMINATED WITH URANYL NITRATE

The extraction of uranyl nitrate contaminated soil with weak solutions of nitric and hydrochloric acid, caustic sodium and subsequent washing of soil residues with distilled water leads to a more than tenfold decrease in the content of uranium isotopes (U238, U235, U234, and U236) in the soil. At the same time, there is a decrease in the content of natural radionuclides (Na22, K40, Zn65, Sn113, Sn126) in the extracted soil samples. An increase in their content in the extract of the analyzed soil sample corresponds to a decrease in their content in the residue of the extracted soil sample. The combined extraction with weak solutions of these acids and alkalis leads to the enrichment of the soil with nitrates and chlorine-containing compounds of non-radioactive metals.