Study of photonuclear reactions with the alpha particles' emission on zirconium, niobium, and molybdenum.

Photonuclear reactions with the emission of protons and alpha particles have been little studied experimentally since their cross-sections are much smaller than those of the (γ, n) channel due to the Coulomb barrier. However, the study of such reactions is of great applied interest to producing medical isotopes. Besides, experimental data on photonuclear reactions with the emission of charged particles for nuclei with Z = 40, 41, 42 open up great opportunities for learning the role of magic numbers. In the presented article, we obtained the weighted average yields of (γ, αn)-reactions for natural zirconium, niobium, and molybdenum at bremsstrahlung γ-quanta of 20 MeV boundary energy for the first time. A significant effect of a closed N = 50 shell was established on the reaction yield with the emission of alpha particles. Our research shows that the semi-direct mechanism for (γ, αn) reactions dominates in the energy range below the Coulomb barrier. As a result, we can note the prospects of applying (γ, αn)-reaction on 94Mo to produce the 89Zr promise medical radionuclide isotope using electron accelerators.

Investigation of Radionuclide Migration at Sites Adjacent to the 30-km Exclusion Zone of the Chernobyl Nuclear Power Plant.

ABSTRACT: This paper reports the study of the vertical migration of radionuclides in soils at test sites adjacent to the 30-km Chernobyl Exclusion Zone. The results of this effort demonstrate that the migration processes for studied pollution occur similarly to the fuel fallout behavior at the vicinity of the Chernobyl Nuclear Power Plant (ChNPP) Unit 4. It was also observed that the main fallout component, 137Cs, originated from aerosol fallout and was bound in the surface layer. The authors determined a significant increase of 60Co, 94Nb, and 241Am radionuclide concentrations in soils near the ChNPP Unit 4 and suggested their appearance due to the installation of the New Safe Confinement. Niobium-94 activity is proposed as a marker for monitoring the "fresh" fallout in the Chernobyl Exclusion Zone.

Determination of the long-lived 10Be in construction materials of nuclear power plants using photoactivation method.

The problem of handling nuclear power plant irradiated structural materials holds one of the central places in the nuclear power industry. High toxic 10Be with a half-life of T1/2 = 1.6 × 106 years is discovered in NPP structural materials after reactor operating. 10Be decays through only electrons' emission. Pure beta emitters are extremely difficult to determine in irradiated structural materials and radioactive waste. We proposed a photoactivation approach for determining the 10Be activity in NPP samples. The proposed method involves determining 9Be and 10B concentrations and subsequent recalculation of 10Be activity formed in 9Be(n, γ)10Be and 10B(n, p)10Be reactions. The amount of 9Be and 10B is determined by samples' photoactivation using an electron accelerator and 9Be(γ, 2n)7Be-, 10B(γ, p2n)7Be-reactions. These reactions' experimental yields were measured for 20, 40, and 55 MeV boundary energies of the bremsstrahlung beam. The proposed technique was tested on samples of ChNPP 2nd unit irradiated structural materials. The technique's calculated error is about 15-20%; the sensitivity is 1 Bq × g-1.

Spectroscopy of Radiostrontium in Fuel Materials Retrieved from the Chernobyl Nuclear Power Plant.

ABSTRACT: Some basic methods of measuring radiostrontium activity by spectroscopic methods are considered in this study. These methods of assessing beta spectra and the characteristic radiation that accompanies the breakdown of radiostrontium are described. The sensitivity of these methods based on the assessments of beta spectra both after radiochemical procedures and without radiochemistry is presented. The objective of this paper is to review the spectroscopic procedures that have been developed and used to determine radiostrontium in various matrices; they are focused on modern methods. Samples of fuel particles of different origins, obtained from the Chernobyl Nuclear Power Plant Unit 4, were analyzed using the methods presented in this study.

The plutonium isotopes and strontium-90 determination in hot particles by characteristic X-rays.

This paper reports the developed non-destructive methods for the plutonium isotopes and strontium-90 content determination in hot particles and other samples. The proposed methods are based on the measurement of the characteristic X-rays accompanying the decay of these radionuclides. For hot particles of NPP accident origin, the proposed method's error limits are 10-15% for hot particles (samples) with activity above 100 Bq and 15-20% for hot particles (samples) with activity less than 100 Bq. For explosive particles, the determination accuracy is 10-15% for activity more than 5 Bq and 20-30% for 0.1-5 Bq activity. The accuracy of the proposed method for determining 90Sr in samples with its specific content of more than 104 Bq/sample is 5%, with ~102 Bq/sample its content is 15-20%. The cost of one sample measurement and the processing time of these methods are significantly reduced compared to traditional studies. The proposed methods are reasonably simple measurement methods and can be carried out even in the field condition. They open up new possibilities for the quick search and study of hot particles and environmental samples.