SOLID PHASE EXTRACTANTS BASED ON POROUS POLYMERS IMPREGNATED WITH MULTIDENTATE CHELATING LIGANDS FOR ACTINIDE AND LANTHANIDE REMOVAL

Introduction. Treatment and disposal of radioactive wastes as well as monitoring of radioactive isotope content in environmental objects are actual tasks in the developed world. Lanthanide and transuranium element removal from spent nuclear fuel of nuclear power plants allows decreasing waste amount to be dumped and diminishing the risk of environmental pollution by radionuclides. Problem Statement. Considering extreme radiotoxicity of transuranium elements and tight standards restricting their activity in air and water, there is an urgent need to develop accurate and highly sensitive methods for pollution control. Purpose. Development of solid phase extractants (SPEs) based on porous polymers impregnated with multidentate chelating ligands for lanthanide, uranium and transuranium element removal from aqueous solutions. Materials and Methods. The materials used are porous divinylbenzene polymers of POROLAS brand and styrene-divinylbenzene copolymers from Smoly SE (Kamianske); multidentate chelating ligands of actinides and lanthanides such as N,N,N´,N´-tetra-n-octyl-oxapentane-1,5-diamide (TODGA) and carbamoyl phosphine oxides (CMPO); sorbent from TrisKem (France) based on TRU Resin (Eichrom Industries, Inc.). The research techniques are inductively coupled plasma atomic emission spectrometry, IR spectroscopy, scanning electron spectroscopy, spectrofluorimetry. Results. The solid-phase extractants (SPEs) for actinide and lanthanide removal from aqueous solutions have been synthesized by impregnation of porous polymeric POROLAS matrices and TODGA, CMPO-(PhOct) and CMPO-(Ph2). Sorption kinetics has been studied and capacity values for the different sorbents have been estimated. Extractive columns for uranium and europium concentration have been manufactured. Conclusions. SPEs studied demonstrate a high efficiency in removing uranium and europium from aqueous solutions. Due to their characteristics obtained materials may be used for preconcentration of target ions in radioecologycal monitoring procedures.

Modeling of fine structures in the mass distribution of nuclear reaction products and their recognition by machine learning methods

The article is devoted to the analysis of manifestations in rare multibody decays of heavy nuclei. Together with physicists from the FLNR JINR, a computer model of the fine structure was developed, which they found on the basis of experiments on with transuranium element Californium. To test the hypothesis that the structure found is a meaningful, and is not a noise artifact, it was proposed to use a deep convolution network as a binary classifier trained on a large sample of model and noise images. Preliminary results of using the developed neuroclassifier show prospects of the proposed approach.

A Neutronics Concept Design of Lead-Bismuth Cooled Accelerator-Driven System for Minor Actinide Transmutation

Pursuing a high minor actinide (MA) transmutation rate, this paper proposes a neutronics concept design of lead-bismuth (LBE) cooled accelerator-driven system (ADS) with burnup reactivity swing less than 1% and proton beam current smaller than 17mA. After a comparison with other types of fuels, Uranium-free metallic dispersion fuel (TRU-10Zr)-Zr* is selected to obtain a harder neutron spectrum to transmute MA. With a MA initial loading, the suitable proportion of initial Plutonium to transuranium element (TRU) is found around 33% to make sure that the burnup reactivity swing is less than 1%. The location of the spallation target is optimized to guarantee high external spallation neutron source efficiency and to lower proton beam current. For the subcritical system, initial effective multiplication factor is 0.97, and the thermal power is 1000 MW. For the accelerator, proton with energy of 1.5GeV and a parabolic spatial profile is provided by proton linac. It is demonstrated by the numerical results that the transmutation rate of MA is about 28% after 600 effective full power days (EFPD) while the support ratio for LWR units with the same power is about 46.

Low Temperature Sintering of Si3N4 Ceramics and its Applicability as an Inert Matrix of the Transuranium Elements for Transmutation of Minor Actinides

For the transmutation of the very long half-lived isotopes which are separated from the spent nuclear fuels, it is necessary to find proper inert matrices these are stable under heavy neutron irradiation at high temperature. Silicon nitride ceramics is a candidate since it is very tolerant for heavy neutron irradiation and keeps relatively high thermal conductivity. For these reasons, we try to sinter Si3N4 ceramics containing large amounts of CeO2 as a simulant for Am2O3, a typical transuranium element. The low-temperature pressureless-sintering behavior of the ceramics and chemical and thermal properties of the obtained sintered bodies are reported.

Transuranium Element Incorporation into the β-U3O8 Uranyl Sheet

ABSTRACTSpent nuclear fuel (SNF) is unstable under oxidizing conditions. Although recent studies have determined the paragenetic sequence for uranium phases that result from the corrosion of SNF, there are only limited data on the potential of alteration phases for the incorporation of transuranium elements. The crystal chemical characteristics of transuranic elements (TUE) are to a certain extent similar to uranium; thus TUE incorporation into the sheets of uranyl oxide hydrate structures can be assessed by examination of the structural details of the β-U3O8 sheet type.The sheets of uranyl polyhedra observed in the crystal structure of β-U3O8 also occur in the mineral billietite (Ba[(UO2)3O2(OH)3]2(H2O)4), where they alternate with α-U3O8 type sheets. Preliminary crystal structure determinations for the minerals ianthinite, ([U24+(HO2)4O6(HO)4(H2O)4](H2O)5), and “wyartite II” (mineral name not approved by IMA committee on mineral names), {CaCo3}[U4+(UO2)2O3(OH)2](H2O)4, indicate that these phases also contain β-U3O8 type sheets. The β-U3O8sheet anion topology contains triangular, rhombic, and pentagonal sites in the proportions 2: 1:2. In all structures containing β-U3O8 type sheets, the triangular sites are vacant. The pentagonal sites are filled with U6+O2 forming pentagonal bipyramids. The rhombic dipyramids filling the rhombic sites contain U6+O2 in billietite, U4+O2 in β-U3O8U4+(H2O)2 in ianthinite, and U4+O3 in “wyartite-II” (in which one apical anion is replaced by two O atoms forming a shared edge with a carbonate triangle of the interlayer). Interlayer species include: H2O (billietite, “wyartite II”, and ianthinite), Ba2+ (billietite) Ca2+ (”wyartite II”), and CO3−2 (”wyartite II”); there is no interlayer in β-U3O8. The similarity of known TUE coordination polyhedra with those of U suggests that the β-U3O8 sheet will accommodate TUE substitution coupled with variations in apical anion configuration and interlayer population providing the required charge balance.