Vol.29,

Annular centrifugal extractors (ACEs) offer advantages including excellent hydraulic and mass-transfer performance, small hold-up volume, short residence time, and thus low solvent degradation, high nuclear criticality, easy start-up and shut-down, high compact structure, etc. Therefore, ACEs have attracted increasing interest for future nuclear processing schemes, including the partitioning of high level liquid waste (HLLW). Laboratory-scale and pilot-scale ACEs have been applied in demonstration tests of the trialkyl phosphine oxide (TRPO) process for HLLW partitioning. In this study, an industrial-scale ACE (260 mm in rotor diameter) with magnetic coupling and a "hanging" rotor structure was developed for the TRPO process. Moreover, a series of hydraulic and mass transfer tests were carried out in the industrial-scale ACE. The maximum throughput can reach 10 m³/h under suitable operation parameters when kerosene is used as the organic phase, and water is used as the aqueous phase. The influence of the total flowrate, the flow ratio (aqueous/organic, A/O), and the rotor speed on the liquid hold-up volume was determined. The extraction stage efficiency is higher than 98% under test parameters for extraction of Nd³⁺ and HNO₃, using 30% TRPO-kerosene as the extractant from an HNO₃ solution containing Nd. All results show good performance of the industrial-scale ACE for the TRPO process.

438

The Molten Salt Reactor (MSR) has received much recent attention. The presence of beryllium and the mixing of actinides with light nuclei in the fuel salt results in a relatively strong neutron source that can affect the surveillance at subcritical and transient characteristics during operation. In this study, we predict the inherent neutron sources based on a MSR model. The calculation shows that in the fresh core, the inherent neutron sources are mainly from alpha-induced neutrons. After power operation, the inherent neutron sources become remarkably stronger due to photoneutrons. Despite being an insignificant part in the total neutron population during operation, the inherent neutron sources can be used as the installed neutron source after shutdown. If the MSR has continuously operated at full power (2 MWt) for 10 days, then there would be no need for the installed source within 80 days after shutdown. After operating constantly for 500 days, the installed neutron source can be eliminated within two years after shutdown.

741

The fast and maximum thermal neutron fluxes from the DD-109 neutron generator at the University of Sharjah were experimentally measured by the activation technique using different neutron reactions. The thermal and fast neutron fluxes were found to be 2.960 × 10⁶ and 6.186 × 10⁷ n/cm²s respectively. This was done to verify the modeling results for the optimum moderator thickness needed to maximize the thermal neutron flux. The optimum moderator thickness was found to be between 3.5 and 4 cm. The present data were compared with the detailed MCNP model based calculation performed in earlier work to simulate the generator.

475

In this study, the mass attenuation coefficient of boron-containing ores in the Liaoning province of China was calculated using WinXCOM software to investigate the shielding effectiveness of these ores against gamma rays. The mass attenuation coefficients were also calculated using MCNP-4B code and compared with WinXCOM results; consequently, a good consistency between the results of XCOM and MCNP-4B was observed. Furthermore, the G-P fitting method was used to evaluate the values of exposure buildup factor (EBF) in the energy range of 0.015–15 MeV up to 40 mean free paths. Among the selected ores, boron bearing iron concentrate ore (M3) was determined to be the best gamma ray shielding ore owing to its higher values of mass attenuation coefficient and equivalent atomic number and lower value of EBF. Moreover, American Evaluated Nuclear Data File (ENDF/B-VII) was used to analyze the shielding effectiveness against thermal neutrons. It was determined that Szaibelyite (M2) is the best thermal neutron shielding material. This study would be useful for demonstrating the potential of boron-containing ores for applications in the field of nuclear engineering and technology.

445

Real-time monitoring of the Bragg peak location of carbon ions is urgently required for the quality control of hadron therapy. In this study, we design an annular detector to monitor the Bragg peak location of carbon ions with Geant4 simulation. This 360° surrounding structure has a high detection efficiency for the small-dose situation. The detector consists of a multi-layered collimator system and an NaI scintillator for prompt gamma counting. The multi-layered collimator includes a lead layer to prevent unwanted gammas and the paraffin and boron carbide layers to moderate and capture fast neutrons. An inclination of the detector further diminishes the background signal caused by neutrons. The detector, with optimized parameters, is applicable to carbon ions of different energies. In addition, the scintillator is replaced by an improved EJ301 organic liquid scintillator to discriminate gammas and neutrons. Inserting thin Fe slices into the liquid scintillator improves the energy deposition efficiency. The Bragg peak location of 200 MeV/u carbon ions can be monitored by prompt gamma detection with the improved liquid scintillator.

641

Based on 3D-TCAD simulations, single-event transient (SET) effects and charge collection mechanisms in fully-depleted silicon-on-insulator (FDSOI) transistors are investigated. This work presents a comparison between 28-nm technology and 0.2-μm technology to analyze the impact of strike location on SET sensitivity in FDSOI devices. Simulation results show that the most SET-sensitive region in FDSOI transistors is the drain region near the gate. An in-depth analysis shows that the bipolar amplification effect in FDSOI devices is dependent on the strike locations. In addition, when the drain contact is moved toward the drain direction, the most sensitive region drifts toward the drain and collects more charge. This provides theoretical guidance for SET hardening.

475

In this study, a novel phoswich detector for beta–gamma coincidence detection is designed. Unlike the triple crystal phoswich detector designed by researchers at the University of Missouri-Columbia, this phoswich detector is of the semi-well type, so it has a higher detection efficiency. The detector consists of BC-400 and NaI:Tl with decay time constants of 2.4 and 230 ns, respectively. The BC-400 scintillator detects beta particles, and the NaI:Tl cell is used for gamma detection. Geant4 simulations of this phoswich detector find that a 2-mm-thick BC-400 scintillator can absorb nearly all of the beta particles whose energies are below 700 keV. Further, for a 2.00-cm-thick NaI:Tl crystal, the gamma source peak efficiency for photons ranges from a maximum of nearly 90% at 30 keV to 10% at 1 MeV. The self-absorption effect is also discussed in this paper in order to determine the carrier gas’s influence.

511

Readout electronics is developed for a prototype time-of-flight (TOF) ion composition spectrometer for in situ measurement of the mass/charge distributions of major ion species from 200 to 100 keV/e in space plasma. By utilizing a constant fraction discriminator (CFD) and time-to-digital converter (TDC), challenging dynamic range measurements were performed with high time-resolution and event-rates. CFD was employed to discriminate the TOF signals from the micro-channel plate (MCP) and channel electron (CEM) multipliers. TDC based on the combination of counter and OR-gate delay-chain was designed in a high-reliability flash field programmable gate array (FPGA). Owing to the non-uniformity of the delay-chain, a correction algorithm based on integral non-linearity (INL) compensation was implemented to reduce the time uncertainty. The test results showed that the electronics achieved a low timing error of <200 ps in the input range from 35 to 500 mV for the CFD, and a time resolution of ~550 ps with time uncertainty < 180 ps after correction and a time range of 6.4 μs for the TDC. The TOF spectrum from an electron-beam experiment of the impacting N₂ gas further indicated the good performance of this readout electronic.

437

We demonstrated a novel method to measure the unloaded quality factor (Q factor) of high-Q resonant cavities. This method was used to obtain data with low errors and calculate the unloaded Q factor. This procedure was more reliable than traditional methods. The data required for the method were near the resonant frequency, not at the half-power points of the reflection coefficient curve or Smith chart. We applied the new method to measure a resonant cavity with an unloaded Q factor of ~100,000, obtaining good agreement between the measured and theoretical results.

666

The transport characteristics of a space charge dominated multi-species deuterium beam consisting of D1+, D2+, and D3+ particles in an electrostatic low energy beam line are studied. First, the envelope equations of the primary D1+ beam are derived considering the space charge effects caused by all particles. Second, the evolution of the envelope of the multi-species deuterium beam is simulated using the PIC code TRACK, with the results showing a significant effect of the unwanted beam on the transport of the primary beam. Finally, different injected beam parameters are used to study beam matching, and a new beam extraction system for the existing duoplasmatron source is designed to obtain the ideal injected beam parameters that allow a D1+ beam of up to 50 mA to pass unobstructed through the electrostatic low energy beam transport line in the presence of an unwanted (D2+, D3+) beam of 20 mA; at the same time, distortions of the beam emittance and particle distributions are observed.

534

Cross-sectional investigation is an important method to study ion irradiation effects in the depth direction. In this study, 2 MeV H⁺ was implanted in 6H-SiC single crystals to investigate the effects of light ion irradiation on SiC. Raman spectroscopy and scanning electronic microscopy (SEM) were carried out on cross-sectional samples to reveal the in-depth damage states and dopant behavior. The most damaged region is a little shallower than that predicted by the SRIM procedure, owing to the uncertainty in SRIM simulations. Layered structures representing zones of varying damage after 2 MeV H ion irradiation are clearly observed. Two bands are observed in SEM images, of which on band corresponds to the damage peak, while the other band at the end of the H ions affected area is probably a result of H diffusion propelled by a hydrogen-rich layer during irradiation. A charge accumulation effect related with conductivity on the sample surfaces during SEM tests is observed in the H implanted area. A model is proposed to explain these phenomena.

421

The intensity and number of transmitted multiple scattered photons are calculated for 0.123, 0.320, 0.511, 0.662, and 1.115 MeV gamma photons normally incident on slabs of carbon, aluminum, iron, copper, water, muscle, bone, and concrete with thicknesses varying from 1 to 10 mean free paths. The dependence of the transmission probability and energy distribution on the incident energy and material are examined. In general, the obtained results show good agreement with the other values calculated by the Monte Carlo method.

480

The Ω and ϕ production in relativistic heavy-ion collisions is studied in a dynamical quark coalescence model using the phase space information of strange quarks from a multiphase transport (AMPT) model. Enhanced local parton density fluctuation is implemented in the AMPT to simulate the QCD phase transition dynamics. By studying the transverse momentum p_T spectra and the elliptic flow of the multi-strangeness particles, such as Ω and ϕ, and the Ω/ϕ ratio as a function of p_T in the AMPT, we find that the new development improves the description of experimental data. The study motivates further experimental investigations of Ω and ϕ production in Phase-II of the Beam Energy Scan program at RHIC.

544

A cross section database on excitation functions of reactions produced by charged particles is essential for many areas of nuclear research. Particularly, accurate knowledge on nuclear cross sections for the cyclotron production of radioisotopes is very important for nuclear medicine. In the present paper, the cross section calculations for the production of ^43,44Sc, ⁴⁵Ti, ⁵¹Cr, ⁵⁴Mn and ⁵⁵Fe radioisotopes were carried out by the use of ALICE/ASH code using the Fermi gas model, Kataria Ramamurthy Fermi gas model, and Superfluid nuclear model for nuclear level density. Thereby, these model calculations were compared with the available measured data.

584

Elemental calcium plays important role in human physiology. In order to study the relationship between Ca-intake, Ca-chemical formulation and Ca-absorptivity, a balance experiment using a ⁴¹Ca tracer technique in SD rats was conducted to measure the endogenous fecal calcium and true absorption of calcium. Apparent absorption of calcium was measured as a control to the endogenous calcium labelling experiment. These results show that by using ⁴¹Ca labeled endogenous calcium in vivo, researchers could obtain the true calcium absorption data without extrinsic labeling. Therefore, the method was not affected by the chemical structure or type of calcium supplement and might be used in evaluating the absorptivity of marketed calcium supplements.

496