Pulsed Reactor Research Articles

Problem of nuclear-laser power engineering and methods of their solution

The concept of a high power reactor-laser system based on a nuclear pumped optical quantum amplifier (OKUYaN) was formulated at IPPE in the mid-1980-ies. The idea amounted to the use of wide-aperture OKUYaN as an amplifier within the already well-known “master laser – two-pass amplifier with phase conjugation” scheme. The structure of such an amplifier includes a system of two neutron-coupled units – an ignition reactor (RB) and a nuclear pumped laser amplifier (LB). The ignition unit is a compact multi-core pulsed fast neutron reactor. The laser amplifier unit operates on thermal neutrons and, with regard to the neutronics, it is a subcritical booster zone of the ignition reactor unit. Unique reactor-laser complex incorporating demonstration sample of a pulsed reactor-laser system based on OKUYaN (test facility “Stand B”) having no analogues anywhere in the world, was developed and put into operation at IPPE in 1999 for the purpose of substantiation of basic principles of the OKUYaN concept and demonstration of the possibility of its practical implementation, as well as verification of calculation codes and development of relevant equipment elements. Problems overcome in the development and construction of “Stand B” test facility, the choice and justification of the neutronics and laser characteristics of the OKUYaN demonstration sample are discussed in the present paper. Provided are the results of a detailed computational-experimental study of the demonstration sample characteristics, the data from systems studies of direct conversion of nuclear fission energy into laser radiation energy in complex reactor-laser devices and the results of examination of prospects for the development of nuclear-laser power engineering.

The CRANK System—A Simple, Robust Apparatus for Measurement of Cherenkov Light at Open-Pool Reactor

Recently, techniques for qualitative inspections of spent fuel using Cherenkov light have advanced the International Atomic Energy Agency’s ability to perform defect verification measurements following discharge of the fuel from the reactor. Unfortunately, these measurements are limited in their value for safeguards and nuclear material accountancy since they do not quantify the fissile material quantities and cannot characterize a reactor during operations. The Cherenkov Radiation Assay for Nuclear Kinetics (CRANK) system has been devised to quantify the fissile material in the Oregon State TRIGA Reactor (OSTR) during two or more reactor pulses through the measurement of Cherenkov light. The results from the OSTR experiments have shown that the CRANK system is capable of determining the ratio of reactor kinetics parameters (RKP) through the measurement of Cherenkov light in an assay of a research reactor capable of pulsing. There exists excellent agreement between the declared value of the RKP ratio in the OSTR Final Safety Analysis Report and four separate reactor pulse comparisons using the CRANK system. Future applications of the CRANK system can provide independent determination of a pulsing research reactor with an unknown RKP ratio.

First results on transient plasma-based remediation of nanoscale particulate matter in restaurant smoke emissions

Recent studies have shown that nanoscale particulate matter produced in commercial charbroiling processes represents a serious health hazard and has been linked to various forms of cancer and cardiopulmonary disease. In this study, we propose a highly effective method for treating restaurant smoke emissions using a transient pulsed plasma reactor produced by nanosecond high voltage pulses. We measure the size and relative mass distributions of particulate matter (PM) produced in commercial charbroiling processes (e.g., cooking of hamburger meat) both with and without the plasma treatment. Here, the plasma discharge is produced in a 3” diameter cylindrical reactor with a 5–10 ns high voltage (17 kV) pulse generator. The distribution of untreated nanoparticle sizes is peaked around 125–150 nm in diameter, as measured using a scanning mobility particle sizer (SMPS) spectrometer. With plasma treatment, we observe up to a 55-fold reduction in relative particle mass and a significant reduction in the nanoparticle size distribution using this method. The effectiveness of the nanoscale PM remediation increases with both the pulse repetition rate and pulse voltage, demonstrating the scalability of this approach for treating particulate matter at higher flow rates and larger diameter reactors.

Analysis of displacement damage effects on bipolar transistors irradiated by spallation neutrons

Displacement damage induced by neutron irradiation in China Spallation Neutron Source (CSNS) is studied on bipolar transistors with lateral PNP, substrate PNP, and vertical NPN configurations, respectively. Comparison of the effects on different type transistors is conducted based on displacement damage factor, and the differences are analyzed through minority carrier lifetime calculation and structure analysis. The influence of CSNS neutrons irradiation on the lateral PNP transistors is analyzed by the gate-controlled method, including the oxide charge accumulation, surface recombine velocity, and minority carrier lifetime. The results indicate that the total ionizing dose in CSNS neutron radiation environment is negligible in this study. The displacement damage factors based on 1-MeV equivalent neutron flux of different transistors are consistent between Xi’an pulse reactor (XAPR) and CSNS.

Light yield and radiation hardness studies of scintillator strips with a filler

Detectors based on polystyrene scintillator strips with WLS fiber readout are widely used to register charged particles in many high-energy physics experiments. The fibers are placed into grooves or holes along the strip. The detection efficiency of these devices can be significantly increased by improving the optical contact between the scintillator and the fiber by adding an optical filler into the groove/hole. This work is devoted to the study of the light yield of a 5-m-long scintillator strip with a 1.2-mm-diameter Kuraray Y11(200)~MC WLS fiber inserted into the strip's co-extruded hole filled with synthetic silicon resin SKTN-MED(E). The light yield was studied using cosmic muons and a $^{60}$Co radioactive source. Radiation hardness study of viscous fillers and short strip samples were performed on the IBR-2 pulsed research reactor of fast neutrons at JINR.

Isomerization of linear C5–C7 over Pt loaded on protonated fibrous silica@Y zeolite (Pt/HSi@Y)

Abstract A novel fibrous silica Y zeolite (HSi@Y) loaded with Pt has been studied based on its ability to produce protonic acid sites originating from molecular hydrogen. The Pt/HSi@Y was prepared using seed assisted crystallization followed by protonation and Pt-loading. The product formed had a spherical morphology with bicontinuous lamellar with a diameter in the range of 500–700 nm. The catalytic activity of the Pt/HSi@Y has been assessed based on light linear alkane (C5–C7) isomerization in a micro-catalytic pulse reactor at 423–623 K. A pyridine IR study confirmed that the introduction of fibrous silica on Y zeolite increased the Lewis acid sites corresponding with the formation of extra-framework Al which led to the generation of more protonic acid sites. A hydrogen adsorbed IR study showed that the protonic acid sites which act as active sites in the isomerization were formed via dissociative-adsorption of molecular hydrogen releasing electrons to the nearby Lewis acid sites. Thus, it is suggested that the presence of Pt and HSi@Y with a high number of Lewis acid as well as weak Bronsted acid sites improved the activity and stability in C5, C6 and C7 isomerization via hydrogen spill-over mechanism.

A dual nanosecond-pulsed laser setup for nanocomposite synthesis—Ag nanoparticles in Al2O3/VO2 matrix

A reactor based on the association of a pulsed laser nanoparticle source and a pulsed laser deposition process is presented. This process uses two independent nano-second pulsed lasers. The nanoparticle source, based on a quenching of a plasma plume, is accurately described. Nanoparticles produced by this dedicated laser-based source present intrinsically quasi-monodisperse size in the range of 1–10 nm. This monodispersity is essential to correlate nanoparticle size and related properties. For silver nanoparticles, a change in a characteristic parameter, the opening t-time of the quenching valve, (conditioning the species residence time) from 280 μs to 580 μs, leads to a nanoparticle size increase by a factor of about two (from 2.5 nm to 4.3 nm). Consequently, the size modulation allows the synthesis of nanoparticles and resulting nanocomposites which present drastically different properties. A kinetic model in good agreement with the experiment shows two nanoparticle growth modes, i.e., a monomer accretion and a cluster coagulation. Revealing the potential of the pulsed laser reactor, different nanocomposite materials constituted by Ag nanoparticles associated with oxide thin films (Al2O3, VO2) matrix are optically characterized. A surface plasmon resonance (λSPR) in the visible–near IR regime is evidenced, and huge modulation and tunability are obtained linked to the host matrix nature and nanocomposite architecture. Moreover, the metal insulator transition capacity of a vanadium dioxide matrix makes λSPR tunable as a function of temperature. This type of nanocomposite appears pertinent for their great potential in both nano-photonics and nano-sensors.

Influence of plasma nitriding pressure on microabrasive wear resistance of a microalloyed steel

Microalloyed steels have been studied not only by the advent of the pre-salt, but also by the continuous search for improvement of their tribological properties. In this work, the influence of the plasma nitriding (PN) pressure on the nitrided layer formed on top of an API 5L X70 microalloyed steel was studied. PN treatments were carried out using a pulsed plasma reactor at temperatures of 410°C and 440°C, in a gas mixture of N2 and H2, for 3h and under different pressures. Results showed that the pressure has a significant effect on the uniformity and width of the plasma sheath and, consequently, on the structure and thickness of the resulting nitrided layer. It has been observed that higher pressures and temperatures have led to the formation of nitrided layers containing a thinner white layer and without nitride needles. The best wear results were offered by the thicker nitrided layers, besides thinner white layer. This type of structure can be produced when PN treatments are performed using low-width plasma sheaths.

Surface chemical reactions during atomic layer deposition of ZnO, ZnS, and Zn(O,S)

Thin films of oxide, sulfide, and oxysulfide of zinc can be deposited with atomic layer deposition (ALD) using diethylzinc with H2O and H2S. While the atomic ratio between O and S in zinc oxysulfide can be arbitrarily tuned by varying the supercycles of oxide and sulfide ALD, it is known that the fraction of S incorporated in the film is higher than its ratio in the reactant pulses. To understand the mechanism controlling the composition of ALD zinc oxysulfide thin films, its surface chemical reactions are investigated using density functional theory calculations. It is observed that all half reactions of both oxide and sulfide ALD would be facile and spontaneous, while the reactions for deposition of sulfide are more favorable over those for oxide. Furthermore, an *OH group on the surface can be easily substituted into *SH by reaction with H2S, but the inverse reaction is less likely. As a result, excess S can be contained in the Zn(O,S) ALD thin films due to the exchange reactions between surface moieties. The authors suggest that the differences in the bond energies of O–H versus S–H moieties are the key governing factor for the composition of ALD zinc oxysulfide films.

Effects of oxide supports on the CO2 reforming of ethane over Pt-Ni bimetallic catalysts

Catalytic reduction of CO2 by ethane creates an opportunity to use the shale gas and CO2 as the raw materials to produce syngas via dry reforming. In the present work, Pt-Ni bimetallic catalysts were investigated on reducible (CeO2, TiO2) and irreducible (γ-Al2O3, SiO2) oxides. The results showed that catalysts supported on reducible oxides, especially CeO2, were more active than those supported on irreducible oxides. Pulse and flow reactor studies and infrared spectroscopy experiments revealed a bi-functional Mars-Van Krevelen redox mechanism on PtNi/CeO2 and a mono-functional Langmuir-Hinshelwood mechanism on PtNi/SiO2, providing insights into the effects of reducibility of oxide supports on the reaction kinetics. Additionally, compared with the non-reducible SiO2, in situ X-ray diffraction (XRD) and pulse reactor analysis revealed that CO2 could be effectively activated on the reducible CeO2 and formed surface oxygen species to promote ethane dissociation into active carbon species. Thermogravimetric analysis (TGA), Transmission electron microscopy (TEM) and Raman spectroscopy showed that cokes formed on PtNi/CeO2 were primarily disordered/amorphous carbon species that could be easily removed during reforming.

Radiation-induced separation and accumulation of electric charge in supercapacitors

In current sources with a radioactive isotope (CSRI), nuclear energy is directly converted into electricity due to the separation of electric charges during the decay of radioactive isotopes. It was previously shown that asymmetric supercapacitors can be used as CSRI prototypes if, after being exposed to pulsed reactor irradiation, the electric charge on their plates increases to several coulombs as a result of internal induced activity. In this paper, the electric charge separation and accumulation in supercapacitors were studied directly in the process of neutron irradiation. The study was focused on the electrophysical characteristics of cylindrical supercapacitors with an organic electrolyte produced by JSC “ELEKOND”. A comparison of symmetric and asymmetric supercapacitors showed that an effective charge accumulation occurs in the asymmetric capacitors: it is independent of the neutron flux density and determined by the absorbed radiation dose. The electrical voltage between the plates of a symmetrical supercapacitor with a capacity of 100 F during irradiation up to an absorbed dose of 50 Gy reaches 1.24 mV. When asymmetric supercapacitors are irradiated with the same dose, a significant increase in the potential difference up to 1.15 V is observed during irradiation and for a long time afterwards (1.5·105 s) due to the electric charge redistribution (~ 5·10–3 C) in the electrolyte and carbon particles with the formation of a double electrical layer. The post-radiation increase in the capacity of asymmetric supercapacitors is ~ 5 mF.

Neutron Physics Experiments at the BIGR and BIR-2M Pulsed Reactors

While the primary purpose of the BIR and BIGR reactors is to generate neutron and gamma irradiation pulses, they were also used regularly to conduct experiments aimed at enhancing the parameters of radiation of pulsed reactors, making them safer, and examining various topics in neutron physics. The present review addresses the following issues: long-term performance of BIR and BIGR in the mode of self-adjustment of power; generation of fission pulses when the rod passes through the core; coupled systems (BIR + a subcritical assembly); experiments with ultracold neutrons at the BIGR reactor; and fast-acting emergency protection and the pulse delay time in the BIR reactor with a weak neutron source in the core.

The Types of Plasma Reactors in Wastewater Treatment

Water pollution is a serious problem in the development of society of China. The plasma technology is one of the advanced oxidation technologies which is an efficient method in wastewater treatment. In this paper the degradation mechanism of organic pollutants in water by plasma is suggested, which is the main chemical reactions and physical effects, the different types of discharge and the corresponding reactors have been mentioned, including pulsed discharge plasma reactor, gliding arc discharge reactor and contact glow discharge electrolysis plasma reactor, especially the reactions in dielectric barrier discharge plasma. The plasma combined with another oxidation reaction processes also are reviewed, including catalyst, Ultraviolet radiation and Fenton reaction combined with plasma reactor.

History of Formation and Practical Realization of the Coupled Reactor Concept

The history of formation and practical realization of the concept of the coupled reactor facilities that was embodied in the domain of aperiodic pulsed reactors is traced back. It is demonstrated that the application of the concept of coupled reactor facilities extends significantly the potentialities of the experiments executed on reactors.

A study on the reaction mechanism of non-oxidative methane coupling in a nanosecond pulsed discharge reactor using isotope analysis

We present a study on the reaction pathways involved in non-oxidative methane coupling in a nanosecond pulsed discharge reactor using isotope analysis. Specifically, plasma-assisted reactions with isotopes, serving as tracers, are performed in two ratios (CH4:D2 = 1:1 and CH4:D2 = 1:3) and elevated pressures (up to 5 bar). Acetylene hydrogenation reactions are also performed in a tubular reactor under conventional furnace heating to simulate post plasma zone conditions. Depending on the pressure applied the major product formed changes. At ambient pressure, acetylene is the major product through thermally driven methane coupling to ethane in gas phase followed by stepwise dehydrogenation of ethane to acetylene (C2H6 → C2H5 → C2H4 → C2H3 → C2H2). At higher pressures (>3 bar), acetylene is formed via the same sequence of paths. However, the higher bulk gas temperature attained when operating at overpressure also activates gas phase methane coupling to ethylene and acetylene hydrogenation to ethylene catalyzed by the copper-based electrode of the reactor. These two reaction paths shift product selectivity from acetylene to ethylene at higher pressures.

High-resolution neutron Fourier diffractometer at the IBR-2 pulsed reactor: A new concept

The High Resolution Fourier Diffractometer (HRFD) is a neutron time-of-flight spectrometer with a fast Fourier chopper and a correlation mode of data acquisition designed to study atomic and magnetic structures of crystalline materials with high resolution in reciprocal space. The HRFD was constructed in the early 1990s by a collaboration of JINR (Dubna), PNPI (Gatchina) and VTT (Espoo) and began operating routinely in 1994 at the IBR-2 pulsed reactor in Dubna. If correlation analysis is used, the HRFD Δd/d resolution is determined by the maximum rotational speed of the Fourier chopper. For Vmax = 6000 rpm, “high-resolution” patterns are measured by backscattering detectors with Δd/d ≈ 0.0015 despite a very short flight path (L ≈ 20 m) between chopper and sample. Switching to a regular TOF-mode (without Fourier chopper) makes HRFD one of the world’s best high-intensity diffractometers, capable of measuring diffraction patterns in the range of ∼1 min and less. In this paper, the experience of using HRFD at IBR-2 is considered and a possible solution for some technical and methodical problems of Fourier diffractometry at a long-pulse neutron source recognized during its operation is discussed. New possibilities appearing after the recent substantial HRFD upgrade and further perspectives on the method are also presented.

Neptunium-Based High-Flux Pulsed Research Reactor

The design principles and parameters of a promising neutron source, based on the fission reaction of the isotope 237Np, for use in research in extracted beams are presented. Such a source can operate as a pulsing reactor or super-booster or as a super-booster multiplying the neutrons from the target of a proton accelerator by using a reactivity modulator. Owing to the threshold character of 237Np fission such a neutron source will possess significantly higher characteristics than a similar setup with plutonium, and in terms of utilization efficiency it will be the leading source in the world for research employing neutron spectroscopy.

Coupled Experimental and Computational Approach for CABRI Power Transients Analysis

CABRI is an experimental pulse reactor, funded by the French Nuclear Safety and Radioprotection Institute and operated by Commissariat a l’Energie Atomique et aux Energies Alternatives at the Cadarache Research Center. It is designed to study fuel behavior under reactivity-initiated accident conditions. In order to produce the power transients, reactivity is injected by depressurization of a neutron absorber (3He) situated in the so-called transient rods inside the reactor core. The CABRI reactivity injection system allows us to generate structured transients based on specific sequences of depressurization. For such transients, the time difference between the openings of two valves of the reactivity injection system has an important impact on the power pulse shape. A kinetic point code, SPARTE, was developed in order to replace the older DULCINEE code dedicated to the modeling and prediction of CABRI power transients. The SPARTE code includes new models of 3He depressurization based on CFD calculations, variable Doppler coefficient based on Monte Carlo calculations, and variable axial neutron flux profile. The density and Doppler models have a large impact on power transient prediction. For low initial pressure transients, the major uncertainty comes from the reactivity injected by the 3He depressurization. For high initial pressure transients, the 3He heating during the power pulse (“TOP effect”) is responsible of an additional injection of reactivity that needs to be modeled precisely.

Modeling of the 3He Density Evolution Inside the CABRI Transient Rods During Power Transients

CABRI is an experimental pulse reactor, funded by the French Nuclear Safety and Radioprotection Institute and operated by CEA at the Cadarache research center. It is designed to study fuel behavior under reactivity-initiated accident conditions. In order to produce the power transients, reactivity is injected by depressurization of a neutron absorber (3He) situated in transient rods inside the reactor core. The shapes of power transients depend on the total amount of reactivity injected and on the injection speed. The injected reactivity can be calculated by conversion of the 3He gas density into units of reactivity. So, it is of upmost importance to properly model gas density evolution in transient rods during a power transient. The 3He depressurization was studied by computational fluid dynamics (CFD) calculations validated by measurements using pressure transducers. The CFD calculations show that the density evolution is slower than the pressure drop. Studies also show that it is harder to predict the depressurization during the power transients because of neutron/3He capture reactions that induce a gas heating. Surrogate models were built based on CFD calculations and validated against preliminary tests in the CABRI transient system. Two methods were identified to evaluate the gas density evolution: CFD calculations and reverse point kinetics (PKs). The first one consists in adding a heat source in transient rods based on the experimental power conversion. The second one consists in using the measured power by boron ionization chambers to evaluate the net reactivity by a reverse PKs method and to subtract the reactivity feedbacks calculated with the DULCINEE multiphysics code.

Neutron RTOF Stress Diffractometer FSD at the IBR-2 Pulsed Reactor

The diffraction of thermal neutrons is a powerful tool for investigations of residual stresses in various structural materials and bulk industrial products due to the non-destructive character of the method and high penetration depth of neutrons. Therefore, for conducting experiments in this research field, the neutron Fourier stress diffractometer FSD has been constructed at the IBR-2 pulsed reactor in FLNP JINR (Dubna, Russia). Using a special correlation technique at the long-pulse neutron source, a high resolution level of the instrument has been achieved (Δd/d ≈ 2 ÷ 4 × 10−3) over a wide range of interplanar spacing dhkl at a relatively short flight distance between the chopper and sample position (L = 5.55 m). The FSD design satisfies the requirements of a high luminosity, high resolution, and specific sample environment. In this paper, the current status of the FSD diffractometer is reported and examples of performed experiments are given.