<Superscript>212</Superscript>Pb/<Superscript>212</Superscript>Bi Generator for nuclear medicine

A scheme for producing the α-emitters ²¹²Pb and ²¹²Bi, to be used in a promising method of diagnostics and therapy in oncology – radioimmunotherapy, is proposed. The technology is based on two generators operating in tandem: ²²⁸Th/²¹²Pb and ²¹²Pb/²¹²Bi. The first one is based on separation from an initial solution containing thorium isotopes and gaseous ²²⁰Rn, which secures the purity of the desired products ²¹²Pb and ²¹²Bi. For a ²²⁸Th/²¹²Pb model generator, the efficiency of ²²⁰Rn extraction from solution was ~60%. After conditioning, the ²¹²Pb solution from the ²²⁸Th/²¹²Pb generator was used to charge a column, which functioned as a ²¹²Pb/²¹²Bi generator, with a cation exchanger.     

Double Differential Proton and Alpha Emission Cross Sections for Structural Fusion Materials <Superscript>94,95,96</Superscript>Mo

In this study, double differential alpha and proton emission cross sections, which is necessary in determination of heating and damages in structural fusion material research, of ^94,95,96Mo target nuclei have been theoretically calculated by the TALYS 1.8 code at 14.8 MeV neutron incident energy and also compared with available experimental data in EXFOR library. The compound nucleus formation process and pre-equilibrium contribution were found as dominant in the emission of proton and alpha particles, the direct reaction contribution also was seen as dominant in higher particle emission energies.     

Analysis of the characteristics of <Superscript>238</Superscript>U, <Superscript>232</Superscript>Th, <Superscript>237</Superscript>Np,and <Superscript>231</Superscript>Pa radiators for fission ionization chambers for measuring the neutron flux density in the ITER diverter

Computational results, obtained by analyzing possible schemes of nuclear transformations of each of four threshold fission radiators ²³⁸U, ²³²Th, ²³⁷Np, and ²³¹Pa, for fission ionization chambers are presented. The influence of the nuclear reactions (n, ƒ), (n, γ), and (n, 2n) on the characteristics of fission ionization chambers is taken into account in the nuclear transformation schemes for all four radiators. The results are presented in the form of a dependence of the sensitivity of the fission ionization chambers on the neutron fluence in the range 10²¹–10²⁴ cm⁻². The effect of 0.2 and 1 g/cm² thick boron screens is examined. Translated from Atomnaya énergiya, Vol. 106, No. 1, pp. 42–47, January, 2009.     

Assessment of <Superscript>137</Superscript>Cs decontamination of concrete by the reagent method

The particulars of radioactive contamination of concrete wastes by ¹³⁷Cs were studied. x-Ray phase analysis and chemical analysis show that clayey materials, including Al₂O₃, Fe₂O₃, K₂O, and MgO, on which ¹³⁷Cs sorption is possible, were present in the concrete wastes. The content and form in which ¹³⁷Cs was found in radioactive concrete wastes from nuclear power facilities as well as in model samples were determined. When the wastes were treated with nitric acid the binder dissolved and a polydisperse suspension formed. The suspension consisted of three phases: solution, fine suspension, and rapidly settling precipitate of heavy filler particles. x-Ray phase analysis was performed and the ¹³⁷Cs mass ratio and distribution in the phases were determined. The possibility of decontaminating the concrete by a reagent method was evaluated.     

Investigations of the regularities in the tranport of <Superscript>137</Superscript>Cs, <Superscript>60</Superscript>Co,and <Superscript>24</Superscript>Na photons in iron,lead, bismuth,tungsten, and uranium

The methods and results of benchmark experiments and calculations of the transport of ¹³⁷Cs, ⁶⁰Co, and ²²Na photons in iron, lead, bismuth, tungsten, and uranium are described. The results are photon spectra which served as the basis for determining the photon absorption coefficients in a wide geometry and the accumulation factors. A comprehensive analysis of the experimental and computational results revealed the regularities in the differences between the experimental and computational photon absorption coefficients in a wide geometry.Translated from Atomnaya Ènergiya, Vol. 97, No. 4, pp. 293–299, October, 2004.     

Use of γ Radiation from Short-Lived Fission Products for Detecting <Superscript>235</Superscript>U and <Superscript>239</Superscript>Pu

It is suggested that γ radiation with E _γ > 4900 keV from short-lived fission products produced by thermal neutrons be used to detect ²³⁵U and ²³⁹Pu in samples. A time regime is substantiated: 120 sec irradiation, 60 sec holding time, and 120 sec measurement time. The contribution of the reaction (n, p) on fast neutrons is studied.__________Translated from Atomnaya Energiya, Vol. 98, No. 5, pp. 365–370, May 2005.     

Effect of <Superscript>3</Superscript>He and <Superscript>6</Superscript>Li accumulation in beryllium blocks on the neutron-physical characteristics of the MIR reactor

Reactions resulting in the accumulation of ³He and ⁶Li, whose thermal neutron capture cross-section is large, occur under the action of neutron radiation in the beryllium blocks of the MIR reactor core. When a neutron absorber accumulates in the moderator of a reactor, important physical characteristics change: reactivity access, efficiency of safety and control rods, and reactivity effects; in addition, energy release is redistributed. An algorithm for calculating ³H, ³He, and ⁶Li in each beryllium block of the core has been developed and implemented. This algorithm makes it possible to follow the change in the concentration of these nuclides during reactor operation and shutdown. The ³He and ⁶Li concentrations are used as initial data for calculating the neutron-physical characteristics of the MIR reactor using the MCU and BERCLI programs. The computational results for the effect of the accumulation of the nuclides indicated on the neutron-physical characteristics of the core are presented. __________ Translated from Atomnaya énergiya, Vol. 104, No. 2, pp. 84–88, February, 2008.     

<Superscript>63</Superscript>Ni-based β-electric current source

The possibility of developing a β-electric atomic battery with microwatt power based on ⁶³Ni with a lifetime of at least 30 years is analyzed. A method is proposed for large-scale commercial production of ⁶³Ni with concentration 80–90% in the final product. A design of a β-electric transducer based on macroporous silicon with optimized configuration and macropore depth (microchannels) is presented and analyzed. ⁶³Ni is deposited on the inner surface of the microchannels. A laboratory model of an atomic battery based on ⁶³Ni has been fabricated. The working parameters and the current-voltage characteristics of a 500 μW(e) atomic battery based ⁶³Ni (90% concentration) are presented. __________ Translated from Atomnaya énergiya, Vol. 103, No. 6, pp. 353–356, December, 2007.     

Determination of impurity radionuclides in <Superscript>131</Superscript>Cs solutions

The radiochemical purity of a ¹³¹Cs solution used in brachytherapy is studied. After separating ¹³¹Cs from the neutron irradiated targets BaO, Ba(NO₃)₂, and BaCO₃, the contribution of impurities was evaluated: 0.015% for ¹²⁴Sb and 0.012% for ¹³²Cs. The contribution of the parent ¹³¹Ba to cesium solutions was, on average, 0.0067% for BaO, 0.01% for Ba(NO₃)₂, and 0.011% for BaCO₃.     

<Superscript>239</Superscript>Pu prompt fission neutron spectra

Calculations of ²³⁹Pu(n, F) prompt fission neutron spectra have been performed for neutron energy up to 20 MeV. The exclusive spectra of pre-fission neutron reactions (n, xnf) were calculated on the basis of the Hauser-Feshbach model simultaneously with the cross sections of (n, F) and (n, 2n) reactions. The spectra of neutrons emitted by fission fragments were approximated by a sum of two Watt distributions. The components of the prompt fission neutron spectra due to pre-fission neutrons are manifested in the prompt fission neutron spectra and the average neutron energy. A correlation is established between this effect in the contribution of emissive fission (n, xnf) in the fission cross-section of ²³⁹Pu(n, F) and ²³⁵U(n, F). It is shown that the ²³⁹Pu(n, F) prompt fission neutron spectra used in applied calculations do not correspond to the experimental differential data and the systematic regularities in the spectra and their average energy found for the most carefully studied nuclei ^235,238U and ²³²Th. __________ Translated from Atomnaya énergiya, Vol. 103, No. 2, pp. 119–124, August, 2007.     

Stepped decontamination of <Superscript>137</Superscript>Cs-contaminated sandy soil

The possibilities of reagent-based processing of sandy soil contaminated with ¹³⁷Cs are examined. To attain a high decontamination factor, the process is conducted in several steps. First, water-gravity separation is used to separate finely dispersed matter (first step). The main goal of the next (second) reagent-based processing step is to destroy the strongly bound fragments and hydroxide films with which a part of the finely dispersed fraction is bound. At the next step, part of the ¹³⁷Cs is extracted into the reagent solution from the purely sandy fraction; repeated water-gravity separation (third step) makes it possible to completely separate the finely dispersed substance. The subsequent steps of reagent-based processing give ¹³⁷Cs concentration in the sandy fraction of the initial soils that meets the sanitary norms.