Cosmogenic <Superscript>7</Superscript>Be fallout near Samarkand in 2002–2009

⁷Be fallout measurements performed around Samarkand in 2002–2009 are presented. The calendar period included in this research covers the ascending part of the 23rd solar activity cycle; this part of the cycle corresponded to a decrease of the monthly average value of the Wolf number from 60 to <5. The linear correlation observed between the fallout and amount of wet precipitation indicates that the latter plays the main role in the removal of ⁷Be from the troposphere. The average seasonal ⁷Be fallout is 223 ± 46 Bq/m² during winter, 324 ± 66 Bq/m² during spring, 75 ± 29 Bq/m² during summer, and 189 ± 43 Bq/m² during fall. These measurements make it possible to evaluate the contribution of precipitation in the form of dust and dew to the total ⁷Be fallout during the summer. The correlation between the solar radiation and ⁷Be fallout is confirmed.     

<Superscript>246–248</Superscript>Cm Neutron fission cross sections and resonance integrals

The fission cross sections of ^246–248Cm nuclei for neutron energies 0.1 eV–20 keV have been measured using an SVZ-100 lead moderation time neutron spectrometer at the Institute of Nuclear Research of the Russian Academy of Sciences. The fission resonance integrals have been calculated. The results are compared with the existing data and recommended evaluations.     

Pre-Equilibrium <Superscript>3</Superscript>He-Emission Spectra at 62 MeV Proton Incident Energy

In this study, the ³He-emission cross sections for ²⁷Al, ^54,56Fe, ¹⁹⁷Au, ²⁰⁸Pb and ²⁰⁹Bi target nuclei have been calculated at 62 MeV proton energy. In these calculations, the pre-equilibrium effects have been investigated. The pre-equilibrium calculations involve the geometry dependent hybrid model and hybrid model. A comparison with theoretical calculations (ALICE/ASH) has been performed and the empirical formulas for the ³He- emission cross sections produced at 62 MeV proton energy have been derived.     

Parameters of <Emphasis Type="Italic">s</Emphasis>-resonances in <Superscript>246–248</Superscript>Cm fission cross sections

The fission cross sections of ²⁴⁶Cm, ²⁴⁷Cm, and ²⁴⁸Cm isotopes measured with an SVZ-100 spectrometer, based on neutron moderation in lead, at the Institute of Nuclear Research of the Russian Academy of Sciences are analyzed. The area of the resolved resonances is calculated, and their neutron and fission widths are determined. The results are compared with existing data and recommended evaluations.     

Calculation of Cross-sections and Astrophysical S-Factors for <Superscript>62</Superscript>Ni(α,n) and <Superscript>62</Superscript>Ni(α,γ) Reactions of Structural Fusion Material Nickel

Nickel is an important element in fusion reactor technologies and astrophysical applications. Therefore, the knowledge of astrophysical S-factors and cross-sections on nickel isotopes is needed. In this work, the cross sections of the ⁶²Ni(α,n) and ⁶²Ni(α,γ) reactions have been calculated. The alpha capture cross sections was calculated up to 10 MeV. In these theoretical calculations, the TALYS 1.6 and NON-SMOKER codes were used. Also for the ⁶²Ni(α,n) and ⁶²Ni(α,γ) reactions, we calculated the astrophysical S-factors that determine the probability of reaction in low energies. Results of our calculations were checked to the experimental data obtained from EXFOR database.     

A Study on <Superscript>8–18</Superscript>Be Isotopes Used on Neutron Multiplier in Reactor Design

Neutronic characterization and development of structural materials, neutron multiplier materials, tritium breeders are primarily important for fusion and hybrid reactors. In order to improve neutron economy, beryllium, lead, bismuth, zirconium are considered and used as neutron multiplier materials in fusion and hybrid reactor design. In this study, rms charge radii, neutron radii, mass radii and neutron skin thickness were calculated for ^8–18Be isotopes nuclei. The neutron and proton density are calculated for Be isotopes. The results obtained were compared with the experimental and theoretical results of other researchers by using Hartree–Fock method with an effective interaction with Skyrme forces.     

The Comparison of (n,p), (n,α), (n,2n) and (α,n) Reaction Cross-Sections for <Superscript>7</Superscript>Li and <Superscript>9</Superscript>Be Target Nuclei

The knowledge of the cross-section is important especially for the fusion and fission reactor technology. In the absence of experimental data or in the difficulty of measuring data, theoretical predictions of nuclear cross-section data are needed to be improved using model calculations or semi-empirical formulas and to be compared with model and formulas to obtain sensitive approaches. In this work, for ⁷Li and ⁹Be target nuclei used as blanket materials in fusion reactors, (n,p), (n,α), (n,2n) and (α,n) reaction cross-section data have been evaluated by using some available empirical and semi-empirical cross-section formulas. The (n,p), (n,α), (n,2n) and (α,n) reaction cross-section formulas developed for medium and heavy mass nuclei by some scientist in literature are applied to ⁷Li and ⁹Be light nuclei and then results obtained from any systematics are compared with each other and the existing experimental data.     

Neutron Emission Spectra of <Superscript>104,105,106,108,110</Superscript>Pd Isotopes for (p,xn) Reactions at 21.6 MeV Proton Incident Energy

Palladium, which is a rare and lustrous silvery-white color from precious metals, plays important role in fusion–fission reactions and different fields of nuclear technology. In addition, it is used for not only cold fusion experiments but also separation of hydrogen isotopes researches for fusion reactors. In this study, neutron-emission spectra produced by (p,xn) reactions for structural fusion material ^{104,105,106,108,110}Pd isotopes have been investigated by a proton beam at 21.6 MeV. Moreover, multiple pre-equilibrium mean free paths constant from internal transition, and the pre-equilibrium and equilibrium level density parameters have been analyzed for some (p,xn) neutron-emission spectra calculated. New evaluated hybrid model and geometry dependent hybrid model, full exciton model and cascade exciton model were used to calculate the pre-equilibrium neutron-emission spectra. For the reaction equilibrium component, Weisskopf–Ewing model calculations were preferred. The obtained results have been discussed and compared with the available experimental data and found agreement with each other.     

Computations of (α,xn) Reaction Cross-Section for <Superscript>107,109</Superscript>Ag Coated Materials with Possible Application in Accelerators and Nuclear Systems

Silver plated shields are used in components and structures of fusion reactors that may be effected due to the huge radiation. For this reason, we focused on excitation functions of ^107,109Ag on alpha induced reactions. For simplicity to examining the events of nuclear physics, nuclear reaction codes such as ALICE/ASH, TALYS, CEM, EMPIRE, PCROSS, GEANT4 and FLUKA that includes different models have been used for many years. In this study, the cross-sections of (α,xn) reactions, where x = 1–5, for ^107,109Ag by using nuclear reaction codes ALICE/ASH and TALYS 1.6 were computed. Hybrid and Geometry Dependent Hybrid Models were used in ALICE/ASH whereas Two-Component Exciton Model was used in TALYS 1.6 reaction codes. Energy ranges of alpha particles for ¹⁰⁷Ag and ¹⁰⁹Ag were taken into computations as 9.2–96.8 and 10.2–71.2 MeV, respectively. Computed results are also compared each other and with experimental data existing in the literature for each reaction.     

Comparison of Level Density Models for the <Superscript>60,61,62,64</Superscript>Ni(p,n) Reactions of Structural Fusion Material Nickel from Threshold to 30 MeV

The knowledge of level density for reaction cross-section calculations are needed for various applications such as fission and fusion reactor design, accelerator driven sub-critical systems, nuclear medicine, neutron capture and astrophysics. In this study, the excitation functions for (p, n) reactions from reaction threshold to 30 MeV proton incident energy on ⁶⁰Ni, ⁶¹Ni, ⁶²Ni and ⁶⁴Ni isotopes were calculated using TALYS 1.6 nuclear code involving the level density models. This is of importance to the validation of nuclear model approaches with increased predictive power. There are several models of level density that can be used to predict cross-section. In this work, the (p, n) cross-sections would be calculated using three different model of level density, such as constant temperature model, back-shifted fermi gas model and generalized superfluid model on ^60,61,62,64Ni reactions. The (p, n) reaction cross-section calculations for ^60,61,62,64Ni target nuclei were compared with each other and the experimental nuclear reaction data obtained from EXFOR database.     

Investigation of Orbits and Stability of Negative Ions of Hydrogen (H<Superscript>−</Superscript>) in Simulated Main Magnetic Field of AVF Cyclotrons

This paper describes equilibrium orbit and stability of negative hydrogen ions (H⁻) on a four sector of tight design giving 30 MeV protons. We simulated radial and vertical changes of main magnetic field of Cyclone-30 by multi degree and Fourier functions. Based on measured main magnetic field by IBA (Ion Beam Application), we calculated coefficients of these functions and investigate equilibrium orbit and stability includes Betetatron frequency, radial and vertical motion and etc. Advanced graphical tools of MATLAB give good visualization features to created models. The simulation results are in good agreement with experimental data.     

Remote-controlled collimated <Emphasis Type="Italic">γ</Emphasis>-ray detector for measuring radioactive contamination

A remote-controlled spectrometric collimated detector has been developed for remote radiation examination of reactor rooms. The apparatus consists of a collimated γ-ray detector, a color video camera and a controller, all secured on a rotating apparatus and rods. An on-board computer, a SKS-08 Kolibri spectrum analyzer, a power supply for the apparatus, and a controller for rotating apparatus are arranged in the controller. Three interchangeable sensors for changing the sensitivity of the apparatus – two CsI(Tl) scintillators – 20 and 5 cm³ photodiodes of the scintillator and a 60 mm³ CdZnTe semiconductor sensor. The collimated detector is for remote measurement of the radiation of high-level radwastes extracted from the storage pool in the reactor room. At the stage of preparation for and planning of the work, it can be used to determine the main sources of contamination and evaluate the dose distribution fields.     

Investigation of Some Structural Fusion Materials for (<Emphasis Type="Italic">n</Emphasis>, <Emphasis Type="Italic">α</Emphasis>) Reactions at the 14–15 MeV Energy Region

In fusion reactor structures, a serious damage mechanism has been gas production in the metallic resulting from diverse nuclear reactions, mainly through (n, α) and (n, p) reactions above a certain threshold energy. The neutron incident energy around 14–15 MeV is enough to excite the nucleus for the reactions such as (n, p), (n, d), (n, 2n), (n, t), and (n, α). Design of the fusion reactor, about the 14–15 MeV neutron incident energy reaction cross sections is of great importance for various target nuclei. In this study, the experimental data have been taken only at 14–15 MeV energy regions from EXFOR database. The (n, α) reactions for some structural fusion materials such as ²⁷Al, ⁵¹V, ⁵²Cr, ⁵⁵Mn, ⁵⁶Fe and ⁵⁸Ni have calculated by using evaluated empirical formulas developed by Tel et al. at 14–15 MeV and calculated with the pre-equilibrium models up to 20 MeV. The calculated results are discussed and compared with the experimental data taken from EXFOR database.     

Investigation of Some Structural Fusion Materials for (<Emphasis Type="Italic">n</Emphasis>, 2<Emphasis Type="Italic">n</Emphasis>) Reactions up to 40 MeV

The knowledge of (n, 2n) cross section is very important and necessary in the reactor technology since a significant portion of the fission neutron spectrum lies above the threshold of (n, 2n) reaction for the most of the reactor materials. The (n, 2n) cross section is neutron multiplier reaction in fusion reactor design. Therefore, (n, 2n) reactions of the selected blanket materials can play a key role for multiplying neutrons in reactor environment. In this study, for some structural fusion materials (n, 2n) reactions such as ²⁷Al(n, 2n)²⁶Al, ⁵¹V(n, 2n)⁵⁰V, ⁵²Cr(n, 2n)⁵¹Cr, ⁵⁵Mn(n, 2n)⁵⁴Mn, ⁵⁶Fe(n, 2n)⁵⁵Fe and ⁵⁸Ni (n, 2n)⁵⁷Ni have been carried out up to 40 MeV incident neutron energy. In these calculations, the pre-equilibrium and equilibrium effects have been investigated. Also in the present work, the (n, 2n) reaction cross-sections have calculated by using evaluated empirical formulas developed by Tel et al. at 14–15 MeV energy. The calculated results are discussed and compared with the experimental data taken from EXFOR database.     

Calculations of Excitation Functions of Some Structural Fusion Materials for (<Emphasis Type="Italic">n</Emphasis>, <Emphasis Type="Italic">t</Emphasis>) Reactions up to 50 MeV Energy

Fusion serves an inexhaustible energy for humankind. Although there have been significant research and development studies on the inertial and magnetic fusion reactor technology, there is still a long way to go to penetrate commercial fusion reactors to the energy market. Tritium self-sufficiency must be maintained for a commercial power plant. For self-sustaining (D-T) fusion driver tritium breeding ratio should be greater than 1.05. So, the working out the systematics of (n, t) reaction cross sections is of great importance for the definition of the excitation function character for the given reaction taking place on various nuclei at different energies. In this study, (n, t) reactions for some structural fusion materials such as ²⁷Al, ⁵¹V, ⁵²Cr, ⁵⁵Mn, and ⁵⁶Fe have been investigated. The new calculations on the excitation functions of ²⁷Al(n, t)²⁵Mg, ⁵¹V(n, t)⁴⁹Ti, ⁵²Cr(n, t)⁵⁰V, ⁵⁵Mn(n, t)⁵³Cr and ⁵⁶Fe(n, t)⁵⁴Mn reactions have been carried out up to 50 MeV incident neutron energy. In these calculations, the pre-equilibrium and equilibrium effects have been investigated. The pre-equilibrium calculations involve the new evaluated the geometry dependent hybrid model, hybrid model and the cascade exciton model. Equilibrium effects are calculated according to the Weisskopf–Ewing model. Also in the present work, we have calculated (n, t) reaction cross-sections by using new evaluated semi-empirical formulas developed by Tel et al. at 14–15 MeV energy. The calculated results are discussed and compared with the experimental data taken from the literature.     

New Evaluated Semi-Empirical Formula Using Optical Model for 14–15 MeV (<Emphasis Type="Italic">n</Emphasis>, <Emphasis Type="Italic">t</Emphasis>) Reaction Cross Sections

In the next century the world will face the need for new energy sources. Nuclear fusion can be one of the most attractive sources of energy from the viewpoint of safety and minimal environmental impact. Fusion will not produce CO₂ or SO₂ and thus will not contribute to global warming or acid rain. Achieving acceptable performance for a fusion power system in the areas of economics, safety and environmental acceptability, is critically dependent on performance of the blanket and diverter systems which are the primary heat recovery, plasma purification, and tritium breeding systems. Tritium self-sufficiency must be maintained for a commercial power plant. The hybrid reactor is a combination of the fusion and fission processes. For self-sustaining (D-T) fusion driver tritium breeding ratio should be greater than 1.05. So working out the systematics of (n, t) reaction cross-sections are of great importance for the definition of the excitation function character for the given reaction taking place on various nuclei at energies up to 20 MeV. In this study, we have calculated non-elastic cross-sections by using optical model for (n, t) reactions at 14–15 MeV energy. We have investigated the excitation function character and reaction Q-values depending on the asymmetry term effect for the (n, t) reaction cross-sections. We have obtained new coefficients for the (n, t) reaction cross-sections. We have suggested semi-empirical formulas including optical model nonelastic effects by fitting two parameters for the (n, t) reaction cross-sections at 14–15 MeV. We have discussed the odd–even effect and the pairing effect considering binding energy systematic of the nuclear shell model for the new experimental data and new cross-sections formulas (n, t) reactions developed by Tel et al. We have determined a different parameter groups by the classification of nuclei into even–even, even–odd and odd–even for (n, t) reactions cross-sections. The obtained cross-section formulas with new coefficients have been discussed and compared with the available experimental data.     

The Equilibrium and Pre-equilibrium Triton Emission Spectra of Some Target Nuclei for (<Emphasis Type="Italic">n</Emphasis>,<Emphasis Type="Italic">xt</Emphasis>) Reactions up to 45 MeV Energy

Although there have been significant research and development studies on the inertial and magnetic fusion reactor technology, there is still a long way to go to penetrate commercial fusion reactors to the energy market. Tritium self-sufficiency must be maintained for a commercial power plant. For self-sustaining (D-T) fusion driver tritium breeding ratio should be greater than 1.05. So, working out the systematics of (n,t) reaction cross sections and triton emission differential data are important for the given reaction taking place on various nuclei at different energies. In this study, (n,xt) reactions for some target nuclei as ¹⁶O, ²⁷Al, ⁵⁹Co and ²⁰⁹Bi have been investigated up to 45 MeV incident neutron energy. In the calculations of the triton emission spectra, the pre-equilibrium and equilibrium effects have been used. The calculated results have been compared with the experimental data taken from the literature.     

Determination of the neutron flux and <Emphasis Type="Italic">γ</Emphasis> radiation in the core of operating and shut-down reactors using quartz glasses and element monitors

The neutron fluxes and the intensity of γ radiation are measured in 26 channels of a VVR-SM reactor and its thermal column. The fast neutron fluxes in the channels are determined using Ni, Fe, Co, Au, and Mn element monitors with different threshold energies, together with a theoretical calculation using the MCNP-4C program. The energy distribution of the neutron flux inside the fuel assembly is obtained for selected channels around the core. The flux of neutrons with energies >1 MeV is in the range (0.5–43)·10¹² cm⁻²sec⁻¹, depending on the location of the channel. A linear correlation is discovered between the induced optical absorption at the 215 nm line (E′ center) of SiO₂–BaO glass and the fast neutron flux in the channels. The γ-ray intensity in the thermal channel is estimated for the reactor during operation (∼38.4 Gy/sec) and 24 hours after it is shut down (∼24.7 Gy/sec) using the E′ centers induced in pure quartz glasses. The observed difference in the efficiency with which oxygen defects are formed during dry and wet irradiation of glass owing to the radiolysis of water must be taken into account when developing radiation technology and during the burial of radioactive waste. Translated from Atomnaya énergiya, Vol. 105, No. 3, pp. 160–164, September, 2008.