Pulsed Reactor Research Articles

A Comparative Analysis of the Characteristics of Data Acquisition Systems From Position-Sensitive Neutron Detectors

Abstract—This article discusses the results of parallel measurements with two-coordinate position-sensitive He3 detectors with a delay line, which are installed on REFLEX and GRAINS neutron spectrometers of the IBR-2 pulsed reactor with the simultaneous use of three data acquisition systems: DeLiDAQ-1, DeLiDAQ-2, and a system based on the N6730 digitizer produced by CAEN.

Vertical Distribution of Major and Trace Elements in a Soil Profile from the Nile Delta, Egypt

Abstract The present study was conducted to highlight the elemental composition of ten soil samples collected at different depths along of a soil profile (0.25-17 m). The collected samples were subjected to epithermal neutron activation analysis at the pulsed reactor IBR-2 of Frank Laboratory of Neutron Physics - Joint Institute for Nuclear Research - Dubna - Russian Federation. The concentrations in mg/kg of 36 major and trace elements were determined. Symbatic behaviour of geochemically related elements was observed: Th and U; Cl and Br and Fe, Ti, Ca, Al, and Mg, etc. A sharp increase of certain concentrations at the depth of 8 m was observed. Significant mafic sources of elements were observed and mostly are attributed to Ethiopian High Plateau with small amount of felsic volcanic rocks.

Pulsed fast reactor neutron irradiation effects in Si doped n-type β-Ga2O3

The effects of pulsed neutron irradiation on Si doped n-type β-Ga2O3 films grown by halide vapor phase epitaxy (HVPE) on bulk Sn doped n+ β-Ga2O3 substrates are reported. This irradiation leads to an almost linear increase with neutron fluence of the density of deep electron traps E2* (Ec − 0.74 eV), E3 (Ec − 1.05 eV), and E4 (Ec − 1.2 eV), with an introduction rate close to 0.4–0.6 cm−1 while the density of the E2 traps (Ec − 0.8 eV) related to Fe was virtually unchanged. In addition, the increase in the density of deep traps with optical ionization threshold of 1.3 eV, 2.3 eV, and 3.1 eV with an introduction rate close to 0.8–2 cm−1 was observed. The carrier removal rate under our conditions was 28 cm−1. Neutron irradiation also led to a measurable decrease of the diffusion length of nonequilibrium charge carriers. The results are qualitatively similar to previous reports for proton and α-particle irradiation of HVPE β-Ga2O3. When comparing the findings with those described earlier for bulk neutron irradiated Ga2O3, we observe lower starting densities of electron and hole traps and lower introduction rates for these traps in the epitaxial structures. The carrier removal rates were comparable to those in bulk crystals.

Hydrogen production via catalytic pulsed plasma conversion of methane: Effect of Ni–K2O/Al2O3 loading, applied voltage, and argon flow rate

Despite industrial application of methane as an energy source and raw material for chemical manufacturing, it is a potent heat absorber and a strong greenhouse gas. Evidently reduction of methane emission especially in the natural gas sector is essential. Methane to hydrogen conversion through non-thermal plasma technologies has received increasing attention. In this paper, catalytic methane conversion into hydrogen is experimentally studied via nano-second pulsed DBD plasma reactor. The effect of carrier gas flow, applied voltage, and commercial Ni–K2O/Al2O3 catalyst loading on methane conversion, hydrogen production, hydrogen selectivity, discharge power, and energy efficiency are studied. The results showed that in the plasma alone system, the highest methane conversion and hydrogen production occurs at argon flow rate of 70 mL/min. Increase in the applied voltage increases the methane conversion and hydrogen production while it decreases the energy efficiency. Presence of 1 g Ni–K2O/Al2O3 catalyst shifts the optimum voltage for methane conversion and hydrogen production to 8 kV, reduces the required power, and increases the energy efficiency of the process. Finally in the catalytic plasma mode the optimum process condition occurs at the argon flow rate of 70 mL/min, applied voltage of 8 kV, and catalyst loading of 6 g. Compared with the optimum condition in the absence of catalyst, presence of 6 g Ni–K2O/Al2O3 catalyst increased the methane conversion, hydrogen production, hydrogen selectivity and energy efficiency by 15.7, 22.5, 7.1, and 40% respectively.

The design and optimisation of tokamak poloidal field systems in the BLUEPRINT framework

Abstract As part of our aim to develop a reactor design framework, we present here our approach to the optimisation of plasma equilibria and tokamak poloidal field systems. A 2-D, free boundary, ideal magneto-hydrodynamic plasma equilibrium solver is described. We use it within the BLUEPRINT reactor design framework to design plasma equilibria and poloidal field coilsets for future fusion reactors in an integrated way. Plasma shape parameters (R0, A, δ, κ) and integral parameters (Ip, βp, li) are controlled for. Constrained optimisation procedures for the positions and currents of the poloidal field coils are presented; these account for current, field, force, and positional constraints on the coils. A pulse length constraint is incorporated in the optimisation procedure in the case of pulsed reactors. We demonstrate our approach on three different reactor concepts: single-null, double-null and negative triangularity tokamaks.

Process intensification of 2-ethylhexyl caprylate/caprate synthesis via a pulsed loop reactor: Multi-objective optimization

This work proposes the optimization of 2-ethylhexyl (2-EH) caprylate/caprate synthesis in a pulsed loop reactor, and the energy efficiency of the reactor was assessed. 2-EH caprylate/caprate can be used as a biodegradable base fluid. Only 0.4 wt% catalyst concentration was used in the reaction. The face-centred central composite design (FCCD) experiment coupled response surface methodology (RSM) has been implemented to screen independent parameters. The optimization process showed that vacuum pressure was the most influential factor followed by oscillation speed, temperature and time. The maximum conversion of 98 % and yield of 89 % were achieved under optimal conditions of 78 °C, 10 mbar, 20 min and 155 rpm. Meanwhile, energy balance calculation indicated that the usage of low vacuum pressure not only significantly reduced the total heat duty from 1381 kJ (1 atm) to 823 kJ (10 mbar) but also alleviated the reaction temperature from 172 °C (1 atm) to 78 °C (10 mbar). The calculation also demonstrated that the reflux-stirred tank reactor produced a lower conversion and yield of ester yet 6 kJ higher total heat duty compared to the pulsed loop reactor, indicating a cost-saving with the pulsed loop reactor.

Evaluation of Radiation Effects on Residents Living Around the NSRR Under External Hazards

Abstract The nuclear safety research reactor (NSRR) is a research reactor of training research isotopes general atomics—annular core pulse reactor (TRIGA-ACPR) type, located in the Nuclear Science Research Institute (NSRI). The NSRR facility has been utilized for fuel irradiation experiments to study the behaviors of nuclear fuels under reactivity-initiated accident (RIA) conditions. Under the new regulation standards, which was established after the Fukushima Daiichi accident, research reactors are regulated based on the risk of the facilities. The graded approach is introduced in the regulation. To apply the graded approach, the radiation effects on residents living around the NSRR under the external hazards were evaluated, and the level of the risk of the NSRR facility was investigated. This paper summarizes the result of the evaluation in the case where the safety functions are lost due to a tornado, an earthquake followed by a tsunami. There is fuel in the reactor core, fresh fuel storage, and spent fuel storage. As the effects from reactor core, we evaluate the external exposure to radiation and exposure from the release of fission products assuming that loss of function to shut down the reactor, break of cladding tubes, loss of reactor pool water, and collapse of the reactor building. As the effects from fresh fuel storage, we evaluate the internal exposure assuming that the fresh fuel particles released into the air because of breaking into pieces. In addition, we evaluate the critical safety assuming that the critical safety shapes of the fresh fuel storage are lost. As the effects from spent fuel storage, we evaluate the critical safety assuming that the critical safety shapes of the spent fuel storage are lost. All in all, the risk is confirmed to be relatively low, since the effective dose on the residents is found to be below 5 mSv per event due to the loss of the safety functions caused by the tornado, earthquake, and the accompanying tsunami.

Assessment of novel rotating bipolar multiple disc electrode electrocoagulation-flotation and pulsed plasma corona discharge for the treatment of textile dyes.

The current study evaluates the performance of the designed novel electrolytic reactor with rotating bipolar multiple disc electrode (RBDE) in the electrocoagulation-flotation (EC-F) process and a pulsed plasma reactor for the removal of toxic textile dyes. Two different classes of dyes, Methyl Orange (MO), an azo group of dye, and Reactive Blue 19 (RB19), a reactive group of dye, were selected. Efficient removal of both the dyes at a faster rate was obtained with the designed RBDE reactor compared to the EC-F process with static electrodes. RB19 and MO were completely decolourized (100%) within 2 min of electrolysis time with rotating and 6 min with static (non-rotating) electrodes, respectively. Similarly, the maximum chemical oxygen demand removal of 86.4% and 93.2% was obtained for RB19 and MO, respectively, with the rotating electrode EC-F process. On the other hand, complete decolourization was obtained in 10 min and 12 min of pulsed corona discharge for MO (50 mg/L) and RB19 (50 mg/L), respectively. The comparison studies of RBDE and pulsed power plasma reactor (PPT) showed that MO removal was faster than RB19 removal in both RBDE EC-F and PPT processes. Relatively long treatment time was needed for RB19 compared to MO due to its complexity of structure and high solubility. RB19 and MO were completely degraded through pulsed corona discharge without any sludge production. The results show that the designed RBDE reactor performed much better than existing conventional electrocoagulation reactors. The RBDE reactor can be used as a pre-treatment unit for industrial wastewater, which can improve the treatment efficiency and reduces the energy consumption. Plasma technology showed complete degradation of pollutant without sludge production. The formation of a wide variety of reactive oxygen species during corona discharge helps in degrading the pollutants. Plasma technology can be used as a secondary treatment system along with the RBDE as pre-treatment process for complex industrial wastewaters. This will improve the quality of treated effluent and reduce the overall cost of treatment.

The Beta-Decay Induced by Neutrino Flux

Previously, it has been repeatedly suggested that the radioactive decay of nuclei is not a random phenomenon and can occur under the influence of a neutrino flux. Our recent experiment [1] showed that the neutrino flux created by a nuclear reactor affects the decay of nuclei in an isolated source 90Sr/90Y, whose beta-electrons have an average energy of the order of 1 MeV. This paper presents the results of searching for the effect of the neutrino flux generated by a pulsed nuclear reactor on the rate of decay of 63Ni nuclei. These nuclei were chosen as the object of research due to the fact that they have a low energy of beta-electrons of the order of 50 keV. Measurements have shown that the same flux of reactor neutrinos has approximately an order of magnitude stronger effect on 63Ni nuclei than on the previously studied nuclei 90Sr/90Y.

Neutron-induced displacement damage effect and mechanism of AlGaN/GaN high electron mobility transistor

In this paper, neutron-induced displacement damage effects of AlGaN/GaN High electron mobility ransistor (HEMT) device and heterostructure on the Xi’an pulse reactor are studied. The equivalent 1 MeV neutron fluence is 1 × 10<sup>14</sup> n/cm<sup>2</sup>. The direct-current characteristics and low frequency noise characteristics of the HEMT deviceare used to characterize the performances before and after being irradiated by the neutrons, and then the experimental results are analyzed theoretically. The analysis results showed that the displacement damage effect caused by the neutron irradiation will introduce the bulk defects into the device. The bulk defects at the channel cause the electrical performance of the device to degrade through trapping electrons and scattering electrons, which are mainly manifested as the drift of positive threshold voltage, the decrease of output saturation drain current, and the increase of gate leakage current. In order to further confirm the effect of neutron irradiation on the defect density of the device, we implement the low-frequency noise test and the calculation of the device, and the results show that the defect density at the channel of the device increases from 1.78 × 10<sup>12</sup> cm<sup>–3</sup>·eV<sup>–1</sup> to 1.66 × 10<sup>14</sup> cm<sup>–3</sup>·eV<sup>–1</sup>, which is consistent with the results of the electrical characteristics test, indicating that the new defects introduced by neutron irradiation do degrade the electrical performance of the device. At the same time, the capacitor-voltage test is also carried out to analyze the Schottky heterojunctions before and after neutron irradiation. It is found that the channel carrier concentration is significantly reduced after irradiation, and the flat band voltage also drifts positively. The analysis shows that after irradiating the device with neutrons, a large number of defects will be generated in the channel, and these defects will affect the concentration and mobility of the channel carriers, which in turn will influence the electrical performance of the device. These experimental results can be used for designing the AlGaN/GaN high electron mobility transistor for radiationhard reinforcement.

Pulsed plasma surface functionalized nanosilver for gene delivery.

Lack of suitable surface properties in biomaterials is an acute challenge for their utilization in nucleic acid delivery, since surface plays a vital role in cell adhesion/uptake and immunity. Low pressure cold plasma is a promising technology for functionalization and surface modification of materials, in an effective, environment friendly and economical way. In this investigation we have modified the surface of silver nanoparticles (AgNPs) with chitosan biopolymer, using plasma treatment, to extend their application scope in intracellular DNA delivery. The plasma functionalized; chitosan modified AgNPs (MetaloPolymeric Nanocarriers; MPNCs) possessed superior biocompatibility compared to unmodified AgNPs. Carboxylic groups were incorporated on the surface of nanosilver using 3600 rotating pulsed plasma reactor and acrylic acid vapors were used as precursor gas. Pulsed plasma polymerization process was optimized with respect to working pressure of the system, duty cycle for pulsing, time of treatment and flow rate. Biocompatibility of the plasma functionalized nanosilver was enhanced by coupling it with Chitosan Oligosaccharide (COS), using EDC (1-Ethyl-3-(3-dimethylaminopropyl) carbodiimide) to form amide linkages. The resulting MPNCs showed high cell viability and bio-stability, which was attributed to plasma processing of nanosilver and its association with COS. In vitro cellular studies illustrated significant uptake of nanoplexes. The study suggested the potential of plasma functionalization for manipulating surfaces of metallic nanoparticles to enhance their application in intracellular gene delivery.

Thermal neutron intensity measurement with fission chamber in current, pulse and Campbell modes

In thermal nuclear reactors, most of the power is generated by thermal neutron induced fission. Therefore, fission chambers with targets that respond directly to slow neutrons are of great interest for thermal neutron flux measurements due to relatively low sensitivity to gamma radiation. However, the extreme conditions associated with experiments at very low cross section demand highly possible thermal neutron flux, leading often to substantial design changes. In this paper we report design of a fission chamber for wide range (from 10 to 1012 n/cm2 sec) measurement of thermal neutron flux. Test experiments were performed at the first beam of IBR2 pulsed reactor using digital pulse processing (DPP) technique with modern waveform digitizers (WFD). The neutron pulses detected by the fission chamber in each burst (5 Hz repetition rate) of the reactor were digitized and recorded to PC memory for further on-line and off-line analysis. New method is suggested to make link between the pulse counting, the current mode and the Campbell technique.

Low counting rate measurement on thermal neutron induced fission using cross-correlation technique

The measurement procedure based on the continuous thermal neutron beam modulation with a mechanical chopper was developed for delayed neutron yield measurement of the thermal neutron induced fission of [Formula: see text]Np. The idea of the procedure is similar to that widely used in modern computer communications to prevent unauthorized data access. The data is modulated with a predefined pattern before transmission to the public network, and only the recipient that has the modulation pattern is able to demodulate it upon receipt. For thermal neutron induced reaction applications, the thermal neutron beam modulation pattern was used to demodulate the measured delayed neutron intensity signals on the detector output, resulting in nonzero output only for the detector signals correlated with the beam modulation. The comparison of the method with the conventional measurement procedure was provided, and it was demonstrated that the cross-correlation procedure has special features making it superior to the conventional one, especially when the measured value is extremely small in comparison with the background. Due to the strong sensitivity of the measurement procedure on the modulation pattern of the neutron beam, one can implement the modulation pattern of a specific shape to separate the effect of the thermal part of the beam from the higher energy part in the most confident way in the particular experiment. The remarkable property of our method is related to the unique possibility of separation of the effects caused exclusively by thermal neutrons using the neutron time-of-flight measurement available on the IBR-2 pulsed reactor.

Simultaneous measurements of heat flow rate and thermal properties of nano boron trioxide under neutron irradiation at the low and high temperature

In the present work, nano boron trioxide (B2O3) samples (purity of 99.5% and true density of 3.10 g/cm3) were irradiated by using neutron irradiation. Neutron irradiation of the samples was carried at the fast neutron flux 4·1012, 8·1012, 1.3·1013, 4·1014 n ⋅cm⁻2 s⁻1 and the neutron flux 1015 n ⋅cm⁻2 s⁻1 and energy of neutron flux E ≥ 1 MeV at room temperature to 350 h at the IBR-2 M pulsed reactor in Joint Institute for Nuclear Research, Dubna, Russia, was used. The unirradiation and after neutron irradiation the thermal kinetics and parameters changes with a differential mechanism. In the DSC curves at the low temperature for unirradiation and irradiation samples does not change. However, at the 100 ≤ T ≤ 900 K temperature range widely endo effects showed separation the water vapor, the absorbed water and hydroxide groups. Under neutron irradiation mechanism of separation of the hydroxide groups, water vapor and the absorbed water dependence of irradiation doses. The heat flow rate kinetics, specific heat capacity, thermodynamic function, degree of [OH] groups in the nano boron trioxide is a more completed.

Effect of Reactor Neutrinos on Beta-Decay

The pulsed nuclear reactor was used to measure the effect of neutrinos on the beta-decay of 90Sr/90Y nuclei. This measurement shows that some increase in the decay rate occurs in a few tens of milliseconds after reactor flashes.

Optical Materials and Fibers in Experiments on Pulsed Nuclear Reactors

The present work is a review of methods characterizing radiation resistance of optical materials and fibers designed for pulsed nuclear reactors.

X-ray structural and physical and mechanical studies of uranium-graphite fuel (IGR reactor)

The pulsed graphite reactor (IGR) is one of the oldest research reactors in the world. Since 1968, graphite with impregnated uranium with an enrichment of 90% in 235 uranium has been used as a fuel for the IGR reactor. Current conditions require the end of the use of highly enriched uranium (HEU) as fuel in research reactors, as this contradicts the concept of technologies resistant to the proliferation of nuclear weapons. For this reason, for more than two decades, international measures have been taken to phase out the use of HEU in research reactors by converting these plants to low enriched uranium fuel (LEU). This determines the relevance of research.Material science studies were conducted to determine the properties of non-irradiated fuel of high enrichment, which are important for the transportation of fuel and its subsequent dilution. Research LEU fuel was conducted in order to obtain information about the properties for comparison with the properties of HEU fuel. One of the tasks is to compare the X-ray structural and physicomechanical characteristics of HEU and LEU fuel in order to make a decision on replacing fuel cells while maintaining the energy release, power and stability of the IGR reactor.The paper presents the main results of material science research, the emphasis is on the analysis of x-ray structural and strength characteristics of uranium-graphite fuel. X-ray structural characteristics were determined by x-ray diffraction. Strength characteristics were established by determining the compressive strength.Significant results were obtained on the X-ray structural and physicomechanical characteristics of the high-enrichment IGR fuel material.X-ray structural characteristics (interlayer distance, degree of graphitization, x-ray density, texturing coefficient) and physicomechanical properties (ultimate compressive and deformation strength at maximum load) HEU of the IGR reactor fuel were determined for the first time. Research is important and can be applied in the design of fuel cells of uranium-graphite reactors.

Removal of simulated NOx from motor vehicle exhaust by high-voltage pulsed discharge coupled with LaMn1-xFexO3 catalyst

High-voltage pulsed discharge coupled with LaMn1-xFexO3 catalyst was used to remove simulation NOx from motor vehicle exhaust. A self-made line-tube pulsed discharge reactor was adopted. Several important parameters such as diameter of stainless steel cylinder of pulsed discharge reactor and diameter of the high-voltage pole were determined. The catalysts were prepared by citric acid-EDTA method, which were characterized by X-ray photoelectron spectroscopy (XPS), electron microscopy (SEM), X-ray diffraction (XRD) and BET. The characteristic results showed that the LaMn1-xFexO3 catalysts could be synthesized successfully. Besides, the effect of calcination temperature, catalyst dosage, gas temperature, and methane addition on removal efficiency of NOx was investigated. The results indicated that the removal efficiency could reach 62.2 % within 20 min treatment.

Investigation of dynamics of the IBR-2M pulsed reactor with energy-production up to 1200 MW·day

The operation of the IBR-2 pulsed reactor (1987-2006) showed that a total transfer coefficient of the power decreases during the operation of the reactor, therefore each reactor cycle has its own transfer coefficients [1] and stability margins. Hence, the study of dynamics of the new reactor IBR-2M (modernized version IBR-2, since 2011) is extremely important. In this paper, the results of an experimental and a modelling study of dynamics of the IBR-2M are presented, for the reliable and safe operation of reactor. For this purpose, model dynamics of the IBR-2M has been developed, which includes experimental data on reactor feedback parameters in period 2015-2017 at a mean power of 0.5 MW. Using the model dynamics of the IBR-2M, the stability margins of the reactor in different regimes its operation (self-regulating and automatic regulating) were estimated. It shown that during the analyzed time of the operation reactor with energy production up to 1200 MW·day significant changes in dynamics of reactor has not occurred. The reactor has been working in the stability region.

Theoretical Optimization of Neutron and Physical Characteristics of a Multiplying Pulsed Neutron Source Based on a Proton Accelerator

The neutron source operating at the Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research (JINR, Dubna, Russia), based on an IBR-2M pulsed reactor with a flux density of thermal neutrons of ~1013 n/(cm2 s) will exhaust its resource and be shut down by 2034. Optimizing this reactor to provide higher neutron flux density is practically impossible. Therefore, it is proposed to consider using a subcritical pulsed neutron source driven by a proton accelerator as a substitute for the IBR-2M. At present, nonmultiplying neutron sources based on high-current proton accelerators are mostly used around the world, for example, SNS or ESS with a beam power of 3 and 5 MW, respectively. In this paper, we present a theoretical comparative analysis of different categories of pulsed neutron sources driven by high-current proton beams, which can help to find the optimum solutions. It is shown that the subcritical one-zone booster with a tungsten target and a plutonium dioxide core can be a promising option. This type of source can provide an average thermal neutron flux density of more than 5.0 × 1014 n/(cm2 s) at a proton-beam power of 0.1–0.2 MW.