V.S. Pronskikh

Transmutation studies using ssntd and radiochemistry and the associated production of secondary neutrons

Abstract Experiments using 1.5 GeV, 3.7 GeV and 7.4 GeV protons from the Synchrophasotron, LHE, JINR, Dubna, Russia, on extended Pb- and U-targets were carried out using SSNTD and radiochemical sensors for the study of secondary neutron fluences. We also carried out first transmulation studies on the long-lived radwaste nuclei 129I and 237Np. In addition, we carried out computer code simulation studies on these systems using LAHET and DCM/CEM codes. We have difficulties to understand rather large transmutation rates observed experimentally when they are compared with computer simulations. There seems to be a rather fundamental problem understanding the large transmutation rates as observed experimentally in Dubna and CERN, as compared to those theoretical computer simulations mentioned above.

Studies on neutron production in the interaction of 7.4 GeV protons with extended lead target

Abstract A cylindrical lead target of diameter 8 cm and length 20 cm was irradiated with 7.4 GeV protons along the axis of the cylinder. The lead target was surrounded with a paraffin layer of thickness 6 cm to moderate the neutrons produced in p + Pb reactions. The spatial distribution of the slow and fast neutrons on different surfaces of the moderator were determined using LR 115 2B detectors (through 10 B(n,α) 7 Li reactions) and CR39 detectors (through proton recoils) respectively. Such results can be valuable in the studies and design of Accelerator Driven Subcritical Nuclear Reactors and Nuclear Waste Incinerators.

Precision half-life measurement of 140La with Ge-detector

Abstract Half-life is one of the fundamental properties of radioactive nuclei, and the precision required for its numerous applications in modern physics sometimes approaches the level of 10−4–10−5. Most part of the T1/2 measurements performed up to now was made with proportional chambers, and the results were sometimes hardly reproducible within the error limits. Using Ge-detectors for that purpose brought some significant advantages but electronic unit related effects and spectra analysis procedures still remain the sources of the errors influencing the accuracy of the T1/2 attained. In this work, 140 La samples were obtained in the 139 La(n,γ) 140 La reaction, employing a microtron as a neutron source and the half-life measurements were performed with a HPGe-detector. Influencing factors such as photopeak and background shape, electronic circuitry dead time and deadtime variations during the measurements, as well as pulse pileup are studied altogether. Values of the 140 La T1/2=1.6808(18) d, λ=0.47749(20)×10−5, agreeing within the uncertainities with the most accurate evaluated ones (T1/2=1.6781(3) d, λ=0.47807(9)×10−5) [2] were obtained in two series of measurements.

Determination of the cross section for nuclear reactions in complex nuclear decay chains

In the present paper decays of genetically connected nuclei are considered and equations for their independent cross sections are derived. An optimisation parameter is proposed for an experiment where spectra of the residual nuclei are studied by the induced activity method. This parameter depends on irradiation time, delay time and spectrum measurement time.

Investigation of the Formation of Residual Nuclei in Reactions Induced by 660 MeV Protons Interacting with the Radioactive 237Np, 241Am and 129I Targets

241Am, 237Np and 129I radioactive targets were irradiated by proton beams with energy 0.66 GeV. The cross- sections of formation of 80, 53 and 86 residual nuclei from 241Am, 237Np and 129I are determined. The experimental results are compared with the theoretical cross-sections calculated by the cascade-evaporation model (CEM).

Investigation of the formation of residual nuclei from radioactive 237Np and 241Am targets in reactions with 660-MeV protons

The burning of radioactive waste is investigated. Targets from 241Am and 237Np were irradiated with 0.66-GeV proton beams. The cross sections for the formation of 60 and 80 residual nuclei from 237Np and 241Am are determined. The experimental results are compared with the theoretical cross sections calculated by the cascade-evaporation model.

Interaction of 12C ions with nuclei of enriched tin isotopes at an energy of 2.2 GeV per nucleon

The formation cross sections for about 110 products of interaction between a 12C ion beam of energy 2.2 GeV per nucleon and tin targets from the isotopes 112,118,120,124Sn were calculated. Massyield and charge distributions were obtained for 112,118,124Sn targets. An analysis of these charge distributions reveals that the positions of their maxima, Zp, are different for targets having different nucleon compositions. The formation cross sections for neutron-rich products originating from neutron-rich targets are found to increase in all product-mass regions considered in our study. Mass distributions are compared for proton-, deuteron- and ion-nucleus reactions.

Formation of close-to-target products in reactions induced by 12C ions on tin isotopes at the energy of 2.2 GeV per nucleon

Cross sections for charge-exchange reactions induced by the interaction between 12C ions of energy

Transmutation of 129I and 237Np using spallation neutrons produced by 1.5, 3.7 and 7.4 GeV protons

E_{^{12} C} = 2.2