Calculations of Proton Emission Cross Sections in Deuteron Induced Reactions of Some Fusion Structural Materials

The growing demands for energy consumption have led to the increase of the research and development activities on new energy sources. Fusion energy has the highest potential to become a very safe, clean and abundant energy source for the future. To get energy from fusion are needed for development of fusion reactor technology. Particularly, the design and development of international facilities as International Thermonuclear Experimental Reactor and International Fusion Material Irradiation Facility requires for the cross-section data of deuteron induced reactions. Moreover, the selection of fusion structural materials are an indispensable component for this technology. Therefore, the cross-section data of deuteron induced reactions on fusion structural materials are of great importance for development of fusion reactor technology. In this study, reaction model calculations of the cross sections of deuteron induced reactions on structural fusion materials such as ²⁷Al, ⁵⁹Co, ⁵⁵Mn, ⁵⁰Cr, ⁵⁴Cr, ⁶⁴Ni, ¹⁰⁹Ag, ¹⁸⁴W and ¹⁸⁶W have been carried out for incident energies up to 50 MeV. In these calculations, the pre-equilibrium and equilibrium effects for (d,p) stripping reactions have been investigated. The pre-equilibrium calculations involve the new evaluated the geometry dependent hybrid model and hybrid model. Equilibrium effects are calculated according to the Weisskopf-Ewing model. In the calculations the program code ALICE/ASH was used. The calculated results are discussed and compared with the experimental data taken from the literature.     

Improved Formula for (<Emphasis Type="Italic">n</Emphasis>,<Superscript>3</Superscript>He) Fusion Reactions Cross Sections Using Optical Model

Non-elastic cross-sections have been calculated by using optical model for (n, ³He) reactions at 14–15 MeV energy. The new empirical formula including optical model non-elastic effects by fitting two parameters for the (n, ³He) reaction cross-sections have been suggested. The excitation function character and reaction Q-values depending on the asymmetry term effect for the (n, ³He) reaction have been investigated. The obtained cross-section formula with new coefficients has been compared with the experimental data and the other fitting formulae existed in the literature and discussed. It has seen that the fit of new formula in this paper is greatly improved with the experimental data.     

New method of producing <Superscript>99</Superscript>Mo in molten-salt fluoride fuel

The status and the problems of world ⁹⁹Mo production are presented. A comparative analysis is made of reactor methods of ⁹⁹Mo production. It is noted that the currently used technologies and research reactors are not satisfying the growing demand in medicine for this isotope. It is underscored that the role of alternative production technologies has grown. In the development of new ⁹⁹Mo production technologies, the experimental results obtained on the basis of research program conducted on the MSRE reactor with molten-salt fluoride fuel have been analyzed. The analysis revealed a special behavior of certain fission products including ⁹⁹Mo: they leave the melt spontaneously and enter the gas phase. The authors hypothesize that highly volatile fluorides of the indicated products are formed in the melt; this explains the effect indicated. The effect is used as a basis to propose a new reactor method of producing fissionproduced ⁹⁹Mo. Concrete examples of a way to implement the new method of producing fission-produced ⁹⁹Mo using molten-salt fluoride nuclear fuel are presented.     

<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.     

Controlling Energy Flow and Loss in p<Superscript>6</Superscript>Li Fusion Plasma

The proton-Lithium-6 (p⁶Li) fusion reaction is significant because it produces energy through charged particles. By selecting this reaction, the problems of tritium processes and 14 MeV neutron fluxes will be reduced. One of the main concerns for p⁶Li plasma is the control of energy flow and loss that occur in fusion reactor. The calculations of energy balance are essential for investigating the energy flow and loss in p⁶Li plasma. It has a fundamental role for describing the material conditions in this plasma. Energy production must compete with inevitable losses in plasma. The losses perform a principal role in determining the operating temperature of thermonuclear plasma. Some losses of energy can be minimized by the suitable selection of designing parameters while some are intrinsic in reactant system. Calculations of energy flow and loss suggest an operating point at 800 keV for p⁶Li plasma. The effect of electron temperature on ion–electron energy transfer and the bremsstrahlung losses is reviewed. It is indicated that the bremsstrahlung radiation losses resulting from large mean electron energies are a serious difficulty for p⁶Li fusion reactor. It would be highly desirable to reduce the electron temperature below their normal equilibrium values. If the ion–electron energy transfer be reduced from the classical value, the electron temperature and thus bremsstrahlung radiation losses would be reduced substantially and as a result the performance of a p⁶Li fusion reactor would be improved significantly. Meanwhile, the bremsstrahlung radiation losses can be minimized with suitable mixture for p⁶Li plasma in a fusion reactor.     

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.     

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.     

Plasma Focus Device as a Breeder of Proton to Produce Short Lived Radioisotope <Superscript>18</Superscript>F

In a plasma focus device, the nuclear fusion products are created through the thermal and non-thermal (beam-target) mechanisms. The beam target character of the pinched plasma is used to determine the yield of 3.02 Mev protons (when deuterium filling gas is used) at the optimized regime. For this situation, a combination of “moving boiler” model and a shock wave theory are employed. The numerical simulations for the production of the positron emitter nuclide, ¹⁸F (T _1/2 = 110 min; widely used in positron emission tomography), for two Mather type devices (NX2 and PF1000) show that, the rules of the drift velocity as well as the drive parameters have an high impact on the final yields.     

Neutron,Proton and Alpha Emission Spectra of Nickel Isotopes for Proton Induced Reactions

The fusion energy is attractive as an energy source because the fusion will not produce CO₂ or SO₂ and so fusion will not contribute to environmental problems, such as particulate pollution and excessive CO₂ in the atmosphere. The fusion reaction does not produce radioactive nuclides and it is not self-sustaining, as is a fission reaction when a critical mass of fissionable material is assembled. Since the fusion reaction is easily and quickly quenched the primary sources of heat to drive such an accident are heat from radioactive decay and heat from chemical reactions. Both the magnitude and time dependence of the generation of heat from radioactive decay can be controlled by proper selection and design of materials. Nickel (Ni) is an important structural material in fusion (and also fission) reactor technologies and many other fields. So, the working out the reaction cross sections of the Ni isotopes is very important for selection of the fusion materials. In this study, ⁵⁸Ni(p,xn), ⁵⁸Ni(p,xp), ⁶⁰Ni(p,xp), ⁶⁰Ni(p,xα) and ⁶²Ni(p,xp) reactions have been investigated using nuclear reaction models. And also the ⁵⁸Ni(p,xn) reaction has been calculated through a method of offered by Tel et al. The calculated results are discussed and compared with the experimental data taken from EXFOR database.     

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.     

Pre-equilibrium Emission Spectra Calculations of <Superscript>232</Superscript>Th(n,xn) Using New Evaluated Method

The knowledge of the thorium (²³²Th) cycle potentialities are required for the design of a fusion-fission (hybrid) reactor. Pre-equilibrium nuclear reactions have been used to investigate the effect of initial exciton numbers on the nucleon emission spectra. In this study, the initial exciton numbers for the target nucleus of ²³²Th were calculated through a method of offered by Tel et al. and then were used to obtain the effect cross section of the neutron emission spectra. Using this new method, a different way from the literature, the initial exciton numbers calculated with the theoretical neutron and proton densities have been obtained with SKM* on the ²³²Th(n,xn) reaction at 14.1 and 18.0 MeV incident neutron energies. The results were analyzed by comparing the empirical results in the literature.     

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>243</Superscript>Am neutron fission cross section and resonance parameters

The SVZ-100 lead moderation time neutron spectrometer at the Institute of Nuclear Physics of the Russian Academy of Sciences was used to measure the fission cross section for ²⁴³Am in the neutron energy range E_n = 0.3 eV – 10 keV. The resonance fission integrals and the area and fission width of the resolved resonances were calculated. The properties of the intermediate-structure resonances were evaluated. The results were compared with existing data and recommended evaluations.     

Examination of Various Kinds of Systematics of Double-Differential Particle Emission Cross Sections for Medium-Heavy Nuclei Important to Fusion Neutronics

Various kinds of systematics used to calculate the double-differential light particle emission cross sections from nuclear reactions induced by light particles are examined for medium-heavy nuclei important in fusion neutronics applications. Fixing the incident and outgoing particles to neutrons, and the incident energy at 14 MeV, results calculated by the systematics, supplemented by the statistical model calculation, are compared with experimental data measured by two Japanese groups. It is concluded that systematics derived by Kumabe et at. and Kalbach has good accuracy in reproducing these data. Discrepancies in the experimental data are pointed out, and suggestions to future compilation of a special purpose file of JENDL for fusion neutronics are made.