Fast Flux Research Articles

A technique for conducting of reactor in-situ tests of optical fibres and FBG-sensors intended for in-vessel applications in thermonuclear facilities

A method for in-situ studies of the optical fibres (OFs) and the fibre Bragg grating (FBG) sensors radiation resistance under irradiation at the IVG.1 M research reactor (Kurchatov, Kazakhstan) was developed. For this purpose, an irradiation ampoule device (AD) was developed that makes it possible to carry out joint irradiation of investigated samples with a fast neutron flux of up to 2.4 1013 n/(cm2·s) and a dose rate of up to 1.57 kGy/s in the temperature range from 200 to 700 °C and pressures of 10–80 Pa.Studies of radiation-induced attenuation (RIA) of single-mode OF in various protective coatings (copper, aluminium and polyimide at a wavelength of 1.55 μm and in the spectral range from 1.1 to 1.7 μm were carried out. Fast neutron fluence and absorbed dose were ФE>0.1MeV=1.72·1017 n/cm2 and Dγ=11.3 MGy, respectively. It has been established that the method of fibre winding in AD has a critical influence and leads to a parasitic contribution of temperature-induced stress-related losses to optical losses arising during reactor irradiation.The operability of FBG sensors up to a temperature of 500 °C has been demonstrated.The developed methods make it possible to conduct in-situ studies of the radiation resistance of fibre-optic components under conditions close to their applications in thermonuclear and nuclear facilities.

Synergic effect of some waste pozzolans on the mechanical and shielding properties of geopolymer concretes

This work aimed to investigate the effect of raw materials to geopolymer concrete; such as silica fume, metakaolin, ground granulated blast-furnace slag, and quartz powder on mechanical (compressive strength, flexural strength), physical, transport, and nuclear radiation shielding properties. The silica fume, metakaolin, ground granulated blast-furnace slag, and quartz powder used singly and/ or in combination for geopolymer mixture along with sodium-based solutions. Four different geopolymer mixtures were prepared and cured at three different temperatures (30°C, 60°C and 90°C) for three curing periods (5, 7 and 9 h). Then, the mineralogical and morphological properties were considered with X-ray diffraction (XRD), Fourier transform infrared (FTIR) and scanning electron microscopy (SEM) tests. Based on the findings, the use of metakaolin in the geopolymer mixture increased both the compressive and flexural strengths. In addition, the compressive strength of 137.5 MPa was reached in the mixture using metakaolin at 90°C and in a short period of curing, like 9 h. The metakaolin (MK) is decreased the sorptivity coefficient of the geopolymer concrete samples. Withal, extensive experimental measurements were performed to investigate the gamma-ray and fast neutron shielding properties of fabricated concretes. The mass attenuation coefficient enjoyed values such as 0.2078, 0.2078, 0.2079 and 0.2081 cm2/g for M1, M2, M3 and M4 geopolymer concretes, respectively. It was reported that the geopolymer concretes attenuated the fast neutron flux with the energy of about 4.5 MeV by 35%. All inspected geopolymer concretes exhibited excellent neutron attenuation properties, as their values ΣR greater than those of commonly used ones as the neutron absorbers.

Time-Dependent Magnetic Flux in Devices for Circuit Quantum Electrodynamics

Time-dependent external flux is ubiquitous across circuit quantum electrodynamics and calls for accurate modeling. Contrary to long-held belief, it is recently predicted---but not yet verified---that the allocation of time-dependent flux cannot be arbitrary in the Hamiltonian. This study provides an experimental verification of this prediction by applying fast flux pulses to a fluxonium qubit and taking measurements of the quantum state following the pulses. Given the widespread use of time-dependent flux in experiments with superconducting qubits, verification of this theory is critical to our understanding of circuit quantum electrodynamics.

Concept Descriptions for the VTR Rabbit System and Driver Fuel Test Assemblies

Two of the experiment vehicles being developed for the Versatile Test Reactor (VTR) are presented here. The first is a rabbit system that will enable rapid insertion of small test capsules into the high fast flux of the VTR core for relatively short durations. The rabbit concept development includes the construction/demonstration of a near-full-scale system in a deep-water pool to demonstrate functionality, development of a concept of operations and initial procedures, and validation of thermal-hydraulic modeling. In addition, modeling efforts are underway to simulate the thermal and neutronic environment of a rabbit capsule. The second type of experiment vehicle presented here is a driver fuel test assembly for inserting fuel and materials tests into the core by replacing a driver fuel assembly. A novel design for dismountable test assemblies is proposed for the VTR.

Can strong substorm-associated MeV electron injections be an important cause of large radiation belt enhancements?

It has become well-established that strong outer radiation belt enhancements are due to wave-driven electron energization by whistler-mode chorus waves. However, in this study, we examine strong MeV electron injections on 10 July 2019 and find substantial evidence that such injections may be a crucial contributor to outer radiation belt enhancement events. For such an examination, it is essential to precisely separate temporal flux changes from spatial variations observed as Van Allen Probes move along their orbits. Employing a new “hourly snapshot” analysis approach, we discover unprecedented details of electron flux evolutions that suggest that for this event, the outer belt enhancement was not continuous but instead intermittent, mostly composed of 4 large discrete injection-driven flux increases. The injections appear as sharp flux increases when observed near apogee. Otherwise, by comparing hourly snapshots for different times, we infer injections and infer temporally stable fluxes between injections, despite strong and continuous chorus emission. The fast and intermittent electron flux growth successively extending earthwards implies cumulative outer belt enhancement via a series of repetitive inward transport associated with injection-induced electric fields.

Development of multiphysics coupling system for nuclear fuel rod with COMSOL and RMC

Coupling fuel performance and neutronics can help improve the prediction accuracy of fuel rod behavior, which is important for fuel design and performance evaluation. A fuel rod multiphysics coupled system was developed with multiphysics software COMSOL and 3D Monte Carlo neutron transport code RMC. The fuel performance analysis module was built on top of COMSOL with the ability to simulate the fuel behavior in two-dimensional axisymmetric (2D-RZ) or three-dimensional (3D) mode. RMC was innovatively wrapped as a component of COMSOL to communicate with the fuel performance analysis module. The data transferring and the coupling process was maintained using COMSOL’s functionality. Two-way coupling was achieved by mapping power distribution and fast neutron flux fields from RMC to COMSOL and the temperature and coolant density fields from COMSOL to RMC. A fuel rod pin lattice was modeled to demonstrate the coupling. Results show that the calculated power and temperature distributions are reasonable. Considering the flexibility of the coupled system, it can be applied to the performance evaluation of new fuel design.

Fast time-varying current triggering flux jumps of multi-filamentary Nb3Sn wire exposed to oblique magnetic field

Due to the oblique magnetic field and rapid time-varying current, the electromagnetic response and thermomagnetic instabilities of high-field superconducting dipole magnets are quite different from the solenoid coils. In this work, we theoretically investigate the flux jump of composite multi-filamentary Nb3Sn wire with high critical current density exposed to an oblique magnetic field and fast transport current. The thermomagnetic stability/instability regions are obtained with respect to flux creep factor and oblique ratios of magnetic field. It is found that the parallel component of the oblique magnetic field can suppress the flux jump. Unlike slow current, it is interesting to find that the fast variations of self-field by high ramp current can trigger flux jumps in Nb3Sn wire. The fast current triggering flux jumps can be tuned by the static oblique magnetic field. Furthermore, we demonstrate that current-like distribution is more likely to trigger quenches, while the magnetic field-like distribution is more likely to trigger flux jumps. The findings of this work are helpful for the optimization of the superconducting coils exposed to oblique magnetic field and fast time-varying current.

Evaluation of BISON metallic fuel performance modeling against experimental measurements within FIPD and IMIS databases

Simulations were conducted using the BISON fuel performance code on an automated process to read initial and operating conditions from two databases—the Fuels Irradiation and Physics Database (FIPD) and Integral Fast Reactor Materials Information System (IMIS) database. These databases contain metallic fuel data from the Experimental Breeder Reactor-II (EBR-II) and the Fast Flux Test Facility (FFTF). The work demonstrates use of an integrated framework to access EBR-II fuel pin data for evaluating fuel performance models contained within BISON to predict fuel performance of next-generation metallic fuel systems. Between IMIS and FIPD, there is enough information to conduct 1,977 unique EBR-II metallic fuel pin histories from 29 different experiments, and 338 pins from FFTF MFF-3 and MFF-5 with varying levels of details between the two databases. Each of these fuel performance histories includes a high-resolution power history, flux history, coolant channel flow rates, and coolant channel temperatures, and new model developments in BISON since the initial demonstration of this integrated framework. Fission gas release (FGR), cumulative damage fraction, fuel axial swelling, FCCI wastage thickness, cladding profilometry, and burnup were all simulated in BISON and compared to post-irradiation examination (PIE) results to evaluate BISON fuel performance modeling. Implementation of new fuel performance models into a generic BISON input file coupled with IMIS and FIPD yielded results with a better representation of physics than the initial evaluation of the integrated framework. Cladding profilometry, FGR, and fuel axial swelling were found to be in good agreement with PIE measurements for most of the pins simulated. The chosen mechanical contact solver was found to significantly impact the axial fuel swelling and cladding strain predictions when used in conjunction with the U-Pu-Zr hot-pressing model since it bound the fuel to prevent further swelling and increased hydrostatic stresses. This work suggests that fuel performance modeling in BISON under steady-state conditions represents the PIE data well and should be reassessed when new PIE data become available in IMIS and FIPD databases and when improved physical models to better capture fuel performance are added to BISON.

Multi-group analysis of Minor Actinides transmutation in a Fusion Hybrid Reactor

New nuclear technologies are currently being study to face High Level Waste treatment and disposal issues. Generally, GEN-IV fission Fast Reactors (FR) are considered the waste-burners of the future. In fact, a fast flux turns out to be the best choice for actinides irradiation in critical reactors because of favorable cross section conditions. Differently, Fusion Fission Hybrid Reactors (FFHR) are futuristic devices based on the combination of fusion and fission systems and could represent an alternative to FRs. In such systems, the choice spectrum of the neutron flux that irradiates HLW may be non-obvious due to some operational constraints which have to be considered. To design and optimize these systems as waste-burners, one should fully understand the transmutation dynamics occurring into the fission region. A multi-energy-group analysis by FISPACT-II code has been set to analyze the conversion processes in scenarios characterized by different neutron energy spectra and fluences. The results of this study show that, despite fast fluxes are characterized by better behaviors in terms of radiotoxicity treatment, the difficulties of reaching high reaction yields may require solutions involving moderators or broadened neutron fluxes to increase the reactions probabilities and, consequently, actinides mass conversion yield.

Defect-rich Mo2S3 loaded wood-derived carbon acts as a spacer in lithium-sulfur batteries: forming a polysulfide capture net and promoting fast lithium flux.

Due to the sluggish kinetics of sulfur conversion and the large volume change of the lithium anode, along with the formation of lithium dendrites, lithium-sulfur batteries (LSBs) usually exhibit severe capacity decay and poor cycle life. It is necessary to consider the factors associated with cathodes, separators and anodes in an integrated manner to solve the problems existing in LSBs. In this paper, a vertically aligned porous carbon decorated with transition metal sulfides was introduced between a cathode and an anode to comprehensively solve the problems of LSBs. Widely existing natural wood was used as the framework structure, and Mo2S3 with abundant sulfur vacancies was deposited into its channels. Theoretical calculations and experimental results have confirmed a low energy barrier for sulfur conversion and the presence of a strong electric field around the spacer, which benefits fast ion transportation. As a result, on employing the multifunctional spacer, LSB full cells delivered a high initial capacity and a long cycle life. This study provides a reference for reducing development cost, simplifying optimization steps and promoting the commercial application of LSBs.

Facile preparation of high performance GO/Mn3O4/PVDF composite membranes with intercalation of manganese oxide nanowires.

Polyvinylidene fluoride (PVDF) has been widely studied and applied in separation membranes due to its high thermal and chemical stability and mechanical strength. However, PVDF has strong hydrophobicity, resulting in easy contamination of the membrane surface and fast flux attenuation, so it is necessary to modify the membrane surface to improve its separation selectivity and service life. In this paper, PVDF microporous membrane was used as the matrix material and graphene oxide (GO) as the separation layer material. The GO/Mn3O4/PVDF composite membrane was prepared by layer self-assembly of GO nanosheets, and the functional layer spacing was adjusted by nanometer Mn3O4 intercalation. The prepared composite membrane showed high flux and separation selectivity in the filtration of organic compounds. The results showed that the rejection of methylene blue increased from 34% to 99.5%, and the flux decreased from 3000 L m-2 h-1 to 95 L m-2 h-1 when GO nanosheets covered the PVDF supporting membrane. After the introduction of Mn3O4 nanowires in the GO interlayer, the dye rejection reached 99.9% and the flux reached 612 L m-2 h-1. Compared with the unintercalated composite membranes, the flux of the prepared composite membranes showed good stability in the treatment of methylene blue, and the rejection remained unchanged.

Synthesis and characterization of PES/PSF/PEG by immersion precipitation for Mediterranean seawater desalination by FO membrane

AbstractIn the present study, a simple, inexpensive, nontoxic, and environmentally friendly polyethylene glycol (PEG) polymer was used to enhance the hydrophilicity of the forward osmosis (FO) membrane using various PEG concentrations as a pore forming agent in the casting solution of polyethersulfone/polysulfone (PES/PSF) blend membranes. A nonwoven PES/PSF FO blend membrane was fabricated via the immersion precipitation phase inversion technique. The membrane dope solution was cast on polyethylene terephthalate (PET) nonwoven fabric. The results revealed that PEG is a pore forming agent and that adding PEG promotes membrane hydrophilicity. The membrane with 1 wt% PEG (PEG1) had about 27% lower contact angle than the pristine blend membrane. The PEG1 membrane has less tortuosity (which reduces from 3.4–2.73), resulting in a smaller structure parameter (S value) of 277 μm, due to the presence of open pores on the bottom surface structure, which results in diminished ICP. Using 1 M NaCl as the draw solution and distilled water as the feed solution, the PEG1 membrane exhibited higher water flux (136 L m−2 h−1) and lower reverse salt flux (1.94 g m−2 h−1). Also, the selectivity of the membrane, specific reverse salt flux, (Js/Jw) showed lower values (0.014 g/L). Actually, the PEG1 membrane has a 34.6% higher water flux than the commercial nonwoven‐cellulose triacetate (NW‐CTA) membrane. By means of varied concentrations of NaCl salt solution (0.6, 1, 1.5, and 2 M), the membrane with 1 wt% PEG showed improved FO separation performance with permeate water fluxes of 108, 136, 142, and 163 L m−2 h−1. In this work, we extend a promising gate for designing fast water flux PES/PSF/PEG FO blend membranes for water desalination.

Discovery of circular polarization of the 6.7 GHz methanol maser in G33.641-0.228

AbstractThe 6.7 GHz methanol maser emitted by a high-mass star forming region G33.641-0.228 is known to exhibit fast flux density variability on timescales of less than one day. The mechanism of this variability, called burst, has not been known. We observed the circular polarization of this maser. As a result, we found that only the spectral components representing burst exhibit strong circular polarization exceeding 10%. This suggests that the two phenomena of the burst and circular polarization are related to each other.

Fast neutron induced gamma rays from (n,n’), (n,p) and (n,α) reactions on CaCO3

Emission of prompt gamma rays following (n,n’), (n,p) and (n,α) reactions induced by irradiation of a calcium carbonate (CaCO3) sample with a beam of fission neutrons was investigated with a modified version of the FaNGaS (Fast Neutron-induced Gamma-ray Spectrometry) instrument operated at the Heinz Maier-Leibnitz Zentrum (MLZ) in Garching. The neutron spectrum has an average energy of 2.30 MeV and at sample position the fast neutron flux was (1.13 ± 0.04) × 108 cm−2 s−1. The measurement was performed at an angle of 90° between neutron beam and detector. In total, we claim the identification of 38 prompt gamma lines, from which we have assigned 12 to the (n,n’) reaction in calcium (7 for 40Ca, 1 for 42Ca and 4 for 44Ca), 1 to the 12C(n,n’)12C reaction, and 2 to the (n,n’) reaction in oxygen (1 for 16O and 1 for 18O). The other observed gamma lines are attributed to the 40Ca(n,p)40K reaction (20 lines) and to the 40Ca(n,α)37Ar reaction (3 lines). Relative intensities and fast neutron spectrum averaged partial cross sections of the gamma lines are presented and compared with available literature data. Our results were found to be in good agreement with available literature data but also improved and complemented it, as we have pointed out possible errors and identified new lines. Additionally, for a counting time of 12 h the detection limits of calcium, carbon and oxygen were determined as 5, 13 and 64 mg, respectively.

Development of a calculation model to simulate the effect of bowing of the VVER-1000 reactor fuel assembly on power distribution

The Lateral deformation of Fuel Assembly (FA) under the operational conditions of the reactor cores is called FA bowing. This phenomenon is caused by factors such as thermal and hydraulic loads on FAs in the reactor core. It can lead to disturbances in the movement of control rods inside of FAs, cross-contact of FAs in refueling, and also changes in power distribution. Changing the distance between the fuels along the assemblies due to bowing, leads to non-uniform distribution of water (coolant) around the FAs and results in neutronic perturbation. In this research, by developing a calculation model for the bowed FAs of the VVER-1000 reactor, based on the distribution of water around FA at different heights. Macroscopic cross-sections are calculated by using the DRAGON cell calculation code and then the effect of bowing on the power distribution is calculated by using the PARCS core calculation code. To verify the model, the bowed FA geometry was simulated in MCNPX-2.7 Monte Carlo code. Results of DRAGON and MCNPX show the relative difference in all macroscopic cross-sections is less than 5%, except for scattering cross-sections (Σs,2), which is about 9%. Comparing the results with each other shows that the model to simulate the bowing effect of VVER-1000 reactor fuel has acceptable accuracy. Besides, for the central FA with C-shape bowing, the relative differences between the results of PARCS and MCNPX for thermal and fast flux are respectively less than 2% and 4%. Also, the effect of FA bowing in different states has been investigated. At last, results show the magnitude of power asymmetry depends on the size of the deformation of the FAs, bowing direction, and boric acid concentration. In addition, the effect of FAs bowing on power distribution and its resulting asymmetry is different during the cycle according to the concentration of boric acid.

A method to quantify the supersonic discharge of airbag cold gas inflators

We discuss a method to quantify the supersonic discharge of airbag cold gas inflators. Since one primary quantity of interest, the mass flow with time, is not directly measurable, a combined experimental and numerical approach was chosen. Shadowgraph and schlieren images visualize the gas dynamic process. Pressure measurements were conducted inside the inflator and downstream of the outlets in the supersonic jet. In this context, a method to measure the pressure of the flow without effects of shock reflection is presented. The temperature inside the inflator was estimated using a fast response heat flux probe and assuming different scenarios for the unknown heat transfer coefficient. Then, a numerical model of the inflator was created. The experimental results served as boundary conditions and some basic sensitivities remaining unknown from the measurements were studied to verify the numerical outcome. The numerical model was verified using experimental results. Finally, the mass flow rate was derived from the numerical model and compared to an analytical model. The method can reconstruct the temporal evolution of the mass flow discharging from the inflator, the pressure and the topology of the flow field within acceptable bounds. Furthermore, the method can deliver inflow data for subsequent airbag inflation studies.Graphical abstract

A Method to Identify the Heat Flux From Photons and Neutrals at the Divertor Target

The surface eroding thermocouple (SETC) is a diagnostic designed for fast surface heat flux measurement and has been successfully applied in DIII-D tokamak to investigate divertor detachment. A novel method has been developed of using a combination of surface-facing and recessed SETCs to distinguish between the heat flux from charged particles, and that from neutrals and radiative heating. This technique suggests that at least 20% of the total incident heat flux is attributable to the latter sources not trapped in the magnetic field in a fully detached open divertor condition. It not only indicates the noncharged particle heating significantly contributes to the total surface heat flux in detached divertor conditions but also demonstrates the feasibility of using two operational modes of SETCs to distinguish between the two surface heating mechanisms.

The effect of cold work on irradiation creep of Zircaloy-2 alloys at low temperature

Internally pressurized capsules made from Zircaloy-2 tubing were irradiated in the National Research Universal (NRU) reactor at Chalk River Laboratories (CRL) at a temperature of approximately 57°C (330 K) in a fast neutron flux of about 3.37 × 1017 n·m−2·s−1 (E>1 MeV). The purpose of this experiment was to study the effect of cold work and crystallographic texture on biaxial stress irradiation creep. The creep capsules were cold worked in both transverse and axial directions. The applied hoop stress during irradiation ranged from 0 to approximately 200 MPa. Two irradiation cycles were completed with a fast neutron fluence of 3.18 × 1025 n·m−2 (E >1 MeV). Diametral and axial strains were measured after each irradiation cycle.This experiment has provided the following insights on Zircaloy-2 alloys irradiated at low temperature. The axial strain increases with fast neutron fluence, while the diametral strain either increases or decreases with fluence depending on the value of hoop stress and the amount of cold work. Both the diametral and axial strain rates increase non-linearly with the hoop stress. There is a weak dependence of the strain rate on cold work at low hoop stresses (50-150 MPa) suggesting that dislocation slip is not a dominant strain producing mechanism at irradiation temperature of about 57°C. The non-linear dependence of the strain rate on cold work that is observed at 200 MPa indicates that dislocation slip mechanisms start to dominate at this stress level.Dislocation densities of the creep capsules were measured by X-ray line broadening, and their structures were further analyzed using transmission electron microscopy (TEM). From these results, the weak dependence of the creep rate on cold work at low stresses can be explained using rate theory model formalism.

Active fast ion charge exchange measurements using a neutral particle analyzer and multiple beam species in C-2W.

In order to measure the fast ion using neutral particle analyzers (NPAs) in the low neutral density core region of a magnetic confinement fusion device, active change exchange measurements are often performed using a neutral beam (NB) as a charge-exchange (CX) target. One of the complications with this approach is that an NB injected as a CX target can also contribute to the total fast ion source. C-2W has a unique solution to this difficulty in that it is equipped with both eight NB injectors, which can inject beams of different particle species, and an electro-magnetic NPA (EM-NPA), which can measure multiple ion species simultaneously. This enables the active and passive fast ion CX components to be clearly distinguished. The decrease in amplitude of the CX spectra when a hydrogen NB is terminated was clearly observed by the EM-NPA in both hydrogen and deuterium channels. This reduction of observed fast ion flux was mainly caused by the diminished fast ion source, not crosstalk or a general reduction in fast ion confinement. As an example application of this technique on C-2W, fast ion behavior during a periodic density drop is explored. The large difference between the active and passive CX components of the EM-NPA signals clearly demonstrates the usefulness of the active fast ion CX measurement.

Fast Flux Entangling Gate for Fluxonium Circuits

We analyze a high-fidelity two-qubit gate using fast flux pulses on superconducting fluxonium qubits. The gate is realized by temporarily detuning magnetic flux through fluxonium loop away from the half flux quantum sweet spot. We simulate dynamics of two capacitively coupled fluxoniums during the flux pulses and optimize the pulse parameters to obtain a highly accurate $\sqrt{i\mathrm{swap}}$-like entangling gate. We also evaluate the effect of the flux noise and qubit relaxation on the gate fidelity. Our results demonstrate that the gate error remains below $10^{-4}$ for currently achievable magnitude of the flux noise and qubit relaxation time.