Experimental determination and computational modeling of threshold reaction rates in 0.8 GeV proton-irradiated lead target

The results of an experimental determination and computational modeling of the rates of threshold reactions on ²⁰⁹Bi, Pb, ¹⁹⁷Au, ¹⁸¹Ta, ¹⁶⁹Tm, In, ⁹³Nb, ⁶⁵Cu, ⁶³Cu, ⁶⁴Zn, ⁵⁹Co, ²⁷Al, ¹⁹F, and C on the external surface of and inside a thick lead target irradiated by 0.8 GeV protons are presented. The reaction rates were measured by γ spectrometry using Ge and (Ge–Li) detectors with resolution 1.8 and 2.9 keV, respectively, on the 1332 keV γ-line. Measurements of 2467 independent and cumulative threshold reaction rates were performed with 244 samples. The LAHET program was used for computational modeling of the results. The MENDL and MENDL2p libraries, the EXFOR databases, and the LAHET program were used to construct the excitation functions of the nuclides formed. The experimentally measured reaction rates are compared with the computed rates. The neutron and proton fluxes along the target, both on its external surface and in the interior volume, were calculated using the experimental threshold reaction rates and the computed cross sections of the reactions averaged over the spectrum of the neutrons and protons. The reaction rates measured inside and on the surface of a natural-lead target were used to determine the accuracy with which the target’s activity is measured.     

Check of the Application of the Monte Carlo Method for Spectrometry of Human Body Radiation in an Experiment on Large Animals

This paper is devoted to an experimental check of a method for performing individual calibration of a spectrometer for human body radiation, using the Monte Carlo method, on 35–40 kg pigs. The ²⁴¹Am content was measured on a low-energy γ spectrometer with a detector based on highly pure germanium. Tomographic images of pigs were used to calculate, using the MCNP4c2 program, the spectra of absorbed energy in a detector. The experimental results are reproduced with an error of less than 30% for injection of ²⁴¹Am and less than 10% for ²⁴¹Am introduced in a capsule. __________ Translated from Atomnaya Energiya, Vol. 99, No. 1, pp. 63–70, July 2005.     

<Superscript>59</Superscript>Ni Accumulation in Corrosion-Resistant Steel under the Action of Neutron Flux

A γ-ray line with energy E_γ = 11.3 MeV was detected during an experiment, performed on a nuclear reactor, investigating the characteristics of the energy spectrum of γ-rays. The most likely source of this line is radiative capture of thermal neutrons by ⁵⁹Ni nuclei, which accumulated in the corrosion-resistance steel as a result of the more than 20 years of irradiation in the reactor, via the reaction ⁵⁸Ni(n, γ)⁵⁹Ni. It was found that for thermal-neutron fluence 10²¹ cm⁻² the ⁵⁹Ni concentration is 0.47% of the ⁵⁸Ni concentration. __________ Translated from Atomnaya Energiya, Vol. 99, No. 4, pp. 268–272, October, 2005.     

Radiation sterilization of mail

The results of sterilization of mail in typical packages using ⁶⁰Co γ rays with average energy 1.33 MeV and in an electron accelerator with electron energy 9 MeV are presented. __________ Translated from Atomnaya énergiya, Vol. 100, No. 1, pp. 63–68, January, 2005.     

Integral cross sections of photonuclear reactions near the giant dipole resonance

The total cross sections of (γ, n) reactions were measured for 12 nuclei from⁴⁵Sc to²⁰⁸Pb using an activational method on bremsstrahlung from a microtron with maximum energy 25 MeV. Calculations of the total cross sections were performed on the basis of a modified preequilibrium decay model. Good agreement was obtained between the experimental and computed cross sections in the mass number range 100–208. 1 figure, 3 tables, 13 references. Translated from Atomnaya énergiya, Vol. 88, No. 5, pp. 391–396, May, 2000     

Neutron-capture therapy with ultra-cold neutrons

The status of neutron-capture therapy of malignant tumors and its problems – damage to healthy tissue as a result of neutron transport to the irradiation location and presence in the therapeutic beam of a background consisting of γ rays and fast neutrons – are presented. To solve these problems, the authors have proposed using ultracold neutrons with energy less than 10^–7 eV, whose unique capability is to undergo total reflection from the surface of a condensed substance at any angle of incidence. Numerous works have demonstrated that such neutrons can be transported along neutron guides. The cross section for inelastic scattering of neutrons by hydrogen-containing substances – water, ethyl alcohol, and biological tissue – has been measured in an IR-8 beam of ultracold and very cold neutrons. At temperature 200–300 K, the experimental data are in very good agreement with calculations, but as temperature decreases further a discrepancy appears, which could be due to the inaccuracy of the model spectra of the oscillations hydrogen-containing substances used in the calculations. The use of ultracold neutrons opens up new possibilities of neutron-capture therapy for treating malignant tumors localized in body cavities or organs.     

Determination of the plutonium mass in containers with plutonium dioxide according to the γ radiation from spontaneous-fission products

A nondestructive method of determining the mass of large plutonium samples which is based on measuring their characteristic γ radiation is presented. The mass and the isotopic composition of the plutonium were determined according to a single measured γ spectrum in two energy ranges: the middle range, where the isotopic composition of plutonium is determined from the lines of the plutonium isotopes, and high-energy, where the radiation of the products of the spontaneous fission of plutonium gives information about the mass of the sample. The dependence of the counting rate in the peaks of the fission products on the effective mass of ²⁴⁰Pu was calibrated according to measurements performed with standard samples of the enterprise. As a result of the measurements, corrections were made for the self-absorption of γ radiation and induced fission, which were calculated by the Monte Carlo method. The error in determining the plutonium dioxide mass is 3–10% for containers with different cool-down times and isotopic composition of plutonium.     

γ-X-ray-spectrometric investigation of plutonium and241Am content in the soil in regions where peaceful nuclear explosions were conducted

A brief exposition of the γ-x-ray spectrometric method and apparatus for analyzing the content of plutonium and²⁴¹Am in samples of soil and vegetation is presented. The results of an analysis of some samples from the regions where peaceful nuclear explosions were conducted in Yakutiya and Perm oblast' are presented. It is concluded that the γ-x-ray spectrometric method can be used to perform large-scale measurements in regions where peaceful nuclear explosions have been conducted, 2 figures, 3 tables, 8 references. Translated from Atomnaya énergiya, Vol. 88, No. 1, pp. 52–55, January, 2000.     

Use of TlBr crystals for x- and γ-ray detectors

The development and investigations of uncooled semiconductor x- and γ-ray detectors based on thallium bromide crystals grown by the Bridgman–Stockbarger method are reported. The procedure for preparing Me–TlBr–Me (Me = Au, In) detector structures is described, and the current–voltage characteristics are investigated. The counting and spectrometric characteristics of the detectors fabricated have been measured. The best energy resolution was 0.54, 1.3, 1.41, 2.1, and 7.1 keV at energy 5.8 (⁵⁵Fe), 22.1 (¹⁰⁹Cd), 59.6 (²⁴¹Am), 122 (⁵⁷Co), and 662 keV (¹³⁷Cs), respectively. Translated from Atomnaya énergiya,Vol. 106, No. 4, pp. 214–217, April, 2009.     

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.     

Fission vacuum chambers and secondary-emission detectors as effective tools for measuring the characteristics of <Emphasis Type="Italic">γ</Emphasis> and neutron radiation from intense sources

The results of measurements of the flux of fast neutrons in the density range 2·10⁸–2·10¹⁹ sec^–1·cm^–2 and γ-ray dose rate in the range 2·10^–3–1·10⁹ Gy/sec in different operating regimes of pulsed nuclear reactors and accelerators are presented. The parameters of the delayed photon radiation are presented.     

Reactor radiation dosimetry using fused quartz

The characteristics of quartz glass for separate dosimetry of γ radiation from a VVR-SM reactor in the presence and absence of neutron fluxes are investigated. Comparing the absorption and photoluminescence spectra of samples irradiated with γ rays from a stopped reactor and mixed with neutron and γ radiation from an operating reactor shows that in both cases oxygen defects are produced and the dose dependences are linear. The dosimetric bands are stable with respect to light and temperatures up to 400°C. The stationary γ-ray flux from the reactor, after the reactor is stopped, is calibrated according to a known source of γ-ray source ⁶⁰Co and is ≈15 Gy/sec. __________ Translated from Atomnaya énergiya, Vol. 100, No. 3, pp. 216–220, March, 2006.     

Correlation relations for estimating the content of plutonium isotopes in fallout due to the Chernobyl accident

The possibility of determining the total α activity A(^239,240Pu) of ²³⁹Pu + ²⁴⁰Pu according to the γ radiation of ¹⁰³Ru and ¹⁰⁶Ru is examined. The statistical properties of the experimental ratios of the activities ρ = A(¹⁰⁶Ru)/A(¹⁰³Ru) are investigated. The distribution of the experimental ratios is similar to the theoretical ratios for fuel and close to a Gaussian distribution with average value 〈p〉 = 0.22 and standard deviation Δ ∼ 0.06. This ratio is used to obtain a relation for estimating A(^239,240Pu) from the γ activity A(¹⁰³Ru). A theoretical analysis is made of the experimental data for the southern raions of Gomel oblast. It is shown that given a good statistical sample of measurements of the γ activity of ¹⁰³Ru it is possible to estimate the average value of the γ activity A(^239,240Pu) and with probability 0.95 the interval of the possible values of this activity. __________ Translated from Atomnaya énergiya, Vol. 103, No. 4, pp. 255–259, October, 2007.     

Determination of γ-ray flux in a stopped VVR-SM reactor from the color-center formation in LiF

The absorption and photoluminescence of LiF crystals, irradiated by γ radiation from a stopped reactor and a wet repository, are studied and compared with the corresponding spectra obtained by irradiation with ⁶⁰Co γ rays with known power. The contribution of neutron and γ radiation of the reactor to the formation of point and complex radiation defects is determined. The dose dependences of the optical bands are used to determine the intensity of the γ radiation from the reactor and the repository. __________ Translated from Atomnaya énergiya, Vol. 100, No. 5, pp. 388–393, May, 2006.     

Microstructure and Surface Properties of Silver after High Dose Nitrogen Ion Implantation

In this paper the effect of nitrogen ion implantation at the energy of 50 keV and doses in the range between 10¹⁷ and 2 × 10¹⁸ ions/cm² on silver surface has been discussed. X-ray diffraction (XRD) analysis was used to characterize microstructure of implanted layer. The XRD results confirmed that by such implantation AgN₃ has been produced. Silver trinitride with orthorhombic structure was formed on cubic structure of silver surface. RMS roughness of implanted samples have been obtained using atomic force microscopy (AFM) analysis and compared with un-implanted sample. Microhardness properties of implanted samples measured by Vickers test. The results show that by increasing the ion dose up to 1 × 10¹⁸ ions/cm² hardness enhances. Finally, reflection changes at the UV–Vis-NIR region measured by diffuse reflectance accessory of a spectrophotometer. The results of spectrophotometry analysis show reduction in diffused reflection spectrum of nitrogen implanted samples.     

Effect of prior structural defects in quartz fiber lightguides on defect formation by γ radiation

The absorption spectra of unirradiated and irradiated (to fast neutron fluence 10¹² and10¹⁴ cm⁻² in VVR-SM) quartz-quartz fibers after additional irradiation with ⁶⁰Co γ rays to 10⁸ rad are investigated. It is shown that neutrons transform E′ centers into ≡Si-Si≡ centers. The kinetics of accumulation of bridge oxygen atoms under the action of γ radiation exhibits two stages. The first stage is due to neutron irradiation and the manifestation of preliminary potential centers of nonbridge oxygen atoms. The second stage is associated with the creation of additional nonbridge oxygen atoms under the action of γ radiation. The γ-ray dose for the onset of the second stage decreases as the fluence of the preliminary neutron irradiation increases. __________ Translated from Atomnaya énergiya, Vol. 104, No. 1, pp. 23–26, January, 2008.     

Estimation of Neutronic Performance in a Hybrid Reactor with Regression Analysis

This study presents regression analysis method used for prediction and investigation of neutronic performance in a hybrid reactor using UO₂ fuel and Flibe (Li₂BeF₄) coolant. The ²³⁵U fraction is increased gradually from 0 to 4% stepped by 1% and the ⁶Li fraction within the Flibe coolant is enriched gradually to 30, 60 and 90% from 7.5%. Relations between ²³⁵U fuel fraction and lithium (⁶Li) enrichment are investigated for the estimation of neutronic performance as the tritium breeding ratio (TBR), energy multiplication factor (M), total fission rate (Σ_f), ²³⁸U (n,γ) reaction and fissile fuel breeding (FFB) in the hybrid reactor. Regression analysis by results obtained by using the code (XSDRNPM/SCALE5) for TBR, M, Σ_f, ²³⁸U (n,γ) and FFB are performed. The results of the regression analysis and the values obtained by using the code (XSDRNPM/SCALE5) are compared with respect to the TBR, M, Σ_f, ²³⁸U (n,γ) and FFB of the reactor. The values calculated from the obtained formulations with regression analysis are found to be in good agreement with results obtained by using the code (XSDRNPM/SCALE5). It is observed that the derived equations from regression analysis could provide an accurate computation of the neutronic performances so that these equations could use for the prediction of TBR, M, Σ_f, ²³⁸U (n,γ) and FFB. In addition, correlation matrix is calculated to determine the degree of relationship between variables as TBR, M, Σ_f, ²³⁸U (n,γ) and FFB.     

Comprehensive Study of Neon HXR and SXR Emitted from APF Plasma Focus Device

Experimental results related to HXR and SXR properties of Neon plasma on the APF plasma focus device is presented. The experiments were carried on over a wide range of neon pressure and at voltages 11, 12 and 13 kV using plastic scintillator (NE102A) coupled with high gain PMT and six filtered photo PIN diodes. For the charging voltages of 11–13 kV with 2.17–3.04 kJ stored energy, the optimum operating pressure in neon is found to be in the range of 3.5–5 torr and the highest HXR emission was observed in the pressure of 5 torr at the voltage 13 kV and the maximum average HXR production is (9.84 ± 0.59) ×10^–7 volt sec. The behavior of SXR intensities were registered by different filters and it was found out that Al-Mylar 6 μm and Cu 10 μm has the highest and lowest amount of X-ray transmission.     

Decomposition of a metastable solid solution in uranium-molybdenum alloy

The process leading to the decomposition of a metastable solid solution (γ² phase) in uranium alloys with 13.6 and 20 at.% molybdenum under isothermal holding conditions at the temperature of the phase regions α+γ′ and α+γ of the phase diagram was examined. The proces was studied by the methods of metallography and x-ray crystallographic analysis. The changes in the microstructure and phase composition of the alloys as a function of the temperature and holding time were indicated. The decomposition process was represented in the form of C-shaped diagrams of the isothermal transformation of the γ² phase, which characterize the structural changes occurring in the aloy in the direction of the equilibrium state. It was found that the process occurs in stages, 6 figures, 7 references. Deceased. Federal Science Center of the Russian Federation—A. A. Bochvar All-Russia Scientific-Research Institute of Standardization in Machine Building. Translated from Atomnaya énergiya, Vol. 88, No. 1, pp. 43–48, January, 2000.     

In search of nuclear fusion in electrolytic cells and in metal/gas systems

It has been reported recently in the literature that unexpected thermal and nuclear effects (production of excess heat, neutrons, γ-rays, and tritium) can occur during the electrolysis of heavy water at palladium or titanium electrodes, or during temperature and pressure cycling of the titanium/deuterium gas system. We have attempted to reproduce some of these experiments. A variety of electrochemical cells having palladium cathodes in the form of wires, tubes, sheets, and rods have been used to electrolyze heavy water containing 0.1 mol.dm⁻³ LiOH, 0.1 mol.dn⁻³ LiOD or 0.5 mol.dm⁻³ D₃PO₄. Current densities of up to 200 mA.cm⁻² were applied. The mass of the palladium cathodes covered the range from 1–40 grams and the surface area varied from 8–140 cm². Neutron detection systems with low constant backgrounds were used to search for neutron emission during electrolysis. These included³He- and¹⁰BF₃-based detectors. After running some of the cells for more than 30 days, no neutron emission above background could be detected. This puts upper limits of 0.5 s⁻¹ and 2×10⁻²³ fus. D-D.s⁻¹ on the neutron emission and the fusion rate, respectively. A sensitive and accurate heat-flow calorimeter was built and used to monitor the energy balance of some of the cells during electrolysis. No unexpected heat effects were observed. This puts an upper limit of 0.13 W.cm⁻³ on the specific excess power. No enrichment of the electrolyte in tritium was evident after electrolysis. Experiments were also performed with the titanium/ deuterium gas system. These consisted of exposing titanium metal to a deuterium gas pressure of 40 atmospheres, lowering the temperature to −196°C, releasing the pressure and gradually warming the titanium to room temperature. No neutron emission above background was observed during these experiments, which puts upper limits of 0.5 s⁻¹ and 4×10⁻²⁵ fus.D-D.s⁻¹ on the neutron emission and fusion rate, respectively. Submitted toJournal of Fusion Energy as part of the Proceedings of the Workshop on Cold Fusion Phenomena held in Santa Fe in May 1989.