Vol.29,

To carry out accurate burnup calculations for a pebble-bed fluoride-salt-cooled high-temperature reactor, the energy-dependent cross section model based on the Doppler broadening rejection correction method has been proposed to develop the energy-dependent elastic scattering cross section model. In this study, the Monte Carlo continuous energy code PSG2/Serpent was used to examine the difference between the constant cross section model and the energy-dependent cross section model during burnup. For the cases analyzed in this study, numerical simulations show that the multiplication coefficient was improved by hundreds pcm and ²³⁹Pu concentration was improved by approximately 1~2% during burnup when the energy-dependent elastic scattering cross section model is considered.

430

Two tests initiated by unscrammed control rod withdrawal (CRW) were performed on the High Temperature Gas-cooled Reactor-Test Module (HTR-10) in November 2003 after the reactor achieved its full power, and the test conditions represented a typical transient scenario of modular high temperature reactors (HTRs), called pressurized loss of forced cooling (PLOFC), and anticipated transient without scram (ATWS). Based on the test parameters, the HTR-10 thermal behaviors under the test conditions were studied with the help of the system analysis code THERMIX. The combination of the test results and the investigation results makes the HTR-10 safety potential better understood. Key phenomena, such as the helium natural circulation and the temperature redistribution in the reactor, were revealed. As the safety feature of most significance, there is a large margin between the maximum fuel temperature and its safety limit in each test. Temperatures of thermocouples in different components were calculated by THERMIX and compared with the test values. The applicability of the code was verified by good agreement obtained from the comparison.

312

The analysis of the fuel depletion behavior is critical for maintaining the safety of accelerator-driven subcritical systems (ADSs). The code COUPLE2.0 coupling 3-D neutron transport and point burnup calculations was developed by Tsinghua University. A Monte Carlo method is used for the neutron transport analysis and the burnup calculation is based on a deterministic method. The code can be used for the analysis of targets coupled with a reactor in ADSs. In response to additional ADS analysis requirements at the Institute of Modern Physics at the Chinese Academy of Sciences, the COUPLE3.0 version was developed to include the new functions of 1. a module for the calculation of proton irradiation for the analysis of cumulative behavior using the residual radionuclide operating history, 2. a fixed-flux radiation module for hazard assessment and analysis of the burnable poison, and 3. a module for multi-kernel parallel calculation, which improves the radionuclide replacement for the burnup analysis to balance the precision level and computational efficiency of the program. This paper introduces the validation of the COUPLE3.0 code using a fast reactor benchmark and ADS benchmark calculations. Moreover, the proton irradiation module was verified by a comparison with the analytic method of calculating the ²¹⁰Po accumulation results. The results demonstrate that COUPLE3.0 is suitable for the analysis of neutron transport and the burnup of nuclides for ADSs.

422

Thermal neutron albedo has been investigated for different thicknesses of mono-material and bi-material reflectors. An equation has been obtained for a bi-material reflector by considering the neutron diffusion equation. The bi-material reflector consists of binary combinations of water, graphite, lead, and polyethylene. An experimental measurement of thermal neutron albedo has also been conducted for mono-material and bi-material reflectors by using a ²⁴¹Am-Be (5.2 Ci) neutron source and a BF₃ detector. The maximum value of thermal neutron albedo was obtained for a polyethylene-water combination (0.95 ± 0.02).

449

Fractional stochastic kinetics equations have proven to be valuable tools for the point reactor kinetics model, where the nuclear reactions are not fully described by deterministic relations. A fractional stochastic model for the point kinetics system with multi-group of precursors, including the effect of temperature feedback, has been developed and analyzed. A major mathematical and inflexible scheme to the point kinetics model is obtained by merging the fractional and stochastic technique. A novel split-step method including mathematical tools of the Laplace transforms, Mittage-Leffler function, eigenvalues of the coefficient matrix and its corresponding eigenvectors have been used for the fractional stochastic matrix differential equation. The validity of the proposed technique has been demonstrated via calculations of the mean and standard deviation of neutrons and precursor populations for various reactivity: step, ramp, sinusoidal, and temperature reactivity feedback. The results of the proposed method agree well with the conventional one of the deterministic point kinetics equations.

354

In this study, Li₃AlF₆ was employed to simulate the molten salt LiF-BeF₂ to explore its pyrohydrolysis behavior and that of its components, i.e., LiF and AlF₃, respectively. The influence of the accelerators α-Al₂O₃ and AlF₃ on the pyrohydrolysis of LiF and Li₃AlF₆ was investigated. Finally, the solid pyrohydrolytic products were characterized by means of X-ray diffraction (XRD), and the corresponding reaction mechanisms were proposed. These experimental results indicated that AlF₃ was completely hydrolyzed to the corresponding oxide α-Al₂O₃ at 650°C in 1 h, whereas the complete hydrolysis of LiF and Li₃AlF₆ required the assistance of either α-Al₂O₃ or AlF₃ under the same conditions. The influence of the accelerator α-Al₂O₃ and AlF₃ on the pyrohydrolytic behavior of Li₃AlF₆ provides references for future research studies on the pyrohydrolysis of LiF-BeF₂ and multi-component molten salts.

351

Iron-ore-imbedded silicone rubber materials were produced for radiation shielding. Samples were tested against a Co-60 gamma source, which is widely used in nuclear technology and medicine. Decreasing the particle size of iron ore resulted in better gamma radiation protection owing to more homogenous distribution. In addition, the materials had flexible properties up to the addition of 60 wt.% iron ore content. Further, 0.5 mmPbE gamma protection was provided by using 2.06 mm thick SDT_60 as the Co-60 source. Iron ore–silicone rubber composites are candidate materials for lead-free flexible radiation protection systems owing to their relatively inexpensive and easy production.

441

An electron cyclotron resonance ion source model that use a coaxial antenna to inject the RF power was simulated, and the corresponding hydrogen plasma densities of the ion source were calculated at different magnetic field distributions via a fluid model. The results show that most of the microwave power is absorbed around the resonance surface near the antenna when the plasma density is below the cut off density of 7.4 × 10¹⁶ m^-3 for 2.45 GHz microwaves, and the simulation results also show that the plasma density is strongly influenced by the position and shape of the resonance surface, where a larger resonance surface would improve the plasma density.

334

To meet the demands on proton therapy in Russia and China, JINR and ASIPP have started to develop a proton therapy facility based on an isochronous superconducting proton accelerator. A 200 MeV/500 nA proton beam will be extracted from the SC200 superconducting proton cyclotron. Due to the energy of the cyclotron being fixed, an energy selection system (ESS) is employed to degrade such energy in order to match the particle energy to a shallower depth. In this article, calculation of beam optics, analysis of beam transmission and correction of orbit distortion are presented. Studies show that the main factors influencing transmission efficiency of the SC200 ESS beamline are the degrader, collimator, slit, vacuum system, beam diagnostic system, and trajectory correction system. Through the beam optics study, the designed ESS beamline can provides 70 MeV to 200 MeV proton beam to a treatment room, with a maximum emittance of 24 π mm mrad. Also, the controllable momentum spread ranges from 0.1% to 1.0%, which is equivalent to an energy spread from 0.193% to 1.93%. The transmission efficiency about 0.204% can be obtained when the emittance is 24 π mm mrad with an energy spread of ±0.6%.

341

A small-angle scattering neutron spectrometer for material research is under construction at the China Spallation Neutron Source. An intervening neutron beam monitor behind the sample is needed to measure the beam intensity in order to reduce the measurement uncertainty caused by beam fluctuation. Considering the mobility requirement and limited space, we proposed a compact monitor using a type of lithium-glass scintillator provided by China Building Materials Academy. Its performance was studied experimentally using ²⁵²Cf and ⁶⁰Co sources. The neutron light yield of the selected scintillator was measured to be 5.3× 10³ photons/neutron. The feasibility of n-gamma discrimination using the charge comparison method was verified. By using the Geant4 toolkit, the monitor was modeled with precise physical processes including neutron tracking, scintillation, and optical photon transmission. The gamma sensitivity and detection efficiency were investigated in the simulation. It was concluded that a 0.5-mm-thick lithium-glass scintillator with natural lithium is an appropriate choice to satisfy both the neutron detection efficiency and gamma elimination requirements.

356

The design, field quality optimization, multipole field analysis, and field measurement of a dipole for a newly developed superconducting proton cyclotron (SC200) beamline are presented in this paper. The maximum magnetic field of the dipole is 1.35 T; the bending radius is 1.6 m with a proton beam energy in the range of 70–200 MeV. The magnetic field was calculated with 2D and 3D simulations, and measured with a Hall mapping system. The pole shim and end chamfer were optimized to improve the field quality. Based on the simulated results, the multipole field components in the good-field region were studied to evaluate the field quality. The results showed that the field quality is better than ±5×10^-4 at 1.35 T with shimming and chamfering. For the transverse field homogeneity, the 3^rd-(B3)- and 5^th-(B5)-order components should be controlled with symmetrical shims. The 2^nd-(B2)-order component was the main disturbance for the integral field homogeneity; it could be improved with an end chamfer. The magnet manufacturing and field measurement were performed in this project. The measurement results demonstrated that the magnetic design and field quality optimization of the 45° dipole magnet can achieve the desired high field quality and satisfy the physical requirements.

529

SwissFEL is a Free Electron Laser (FEL) under commissioning at the Paul Scherrer Institut (PSI) in Switzerland. Digital Low-Level RF (LLRF) systems are used in SwissFEL to control more than 30 RF stations with either standing wave cavities (e.g. RF Gun) or travelling wave structures working at different frequencies. After conditioned to desired power levels, the RF stations need to be setup for beam operation and the LLRF parameters need to be optimized for maximizing the beam stability. Several beam based algorithms were developed to facilitate the setup, calibration and optimization of the SwissFEL RF stations for beam operation. The algorithms were implemented as automation procedures in the framework of Experimental Physics and Industrial Control System (EPICS) and were used in commissioning and daily operation of SwissFEL. In this paper, the algorithms and the implementation will be introduced together with the test results during the commissioning of SwissFEL.

337

The control system of Hefei Light Source II (HLS-II) is a distributed system based on the experimental physics and industrial control system (EPICS). It is necessary to maintain the central configuration files for the existing archiving system. When the process variables (PVs) in the control system are added, removed, or updated, the configuration files must be manually modified to maintain consistency with the control system. This paper presents a new method for data archiving, which realizes the automatic configuration of the archiving parameters. The system uses microservice architecture to integrate the EPICS Archiver Appliance and RecSync. In this way, the system can collect all the archived meta configuration from the distributed input/output controllers (IOCs) and enter them into the EPICS Archiver Appliance automatically. Furthermore, we also developed a web-based GUI to provide automatic visualization of real-time and historical data. At present, this system is under commissioning at HLS-II. The results indicate that the new archiving system is reliable and convenient to operate. The operation mode without maintenance is valuable for large-scale scientific facilities.

331

A general method was developed for promoting peptide assembly and protein polymerization to form nanoscale patterns on various surfaces with an atomic force microscope (AFM) operated in a liquid. By scanning solid surfaces with an AFM tip, we showed that peptide monomers assemble at a higher rate in the tip-scanned area compared to other regions. The promotion is attributed to the mechanical force applied by the scanning tip. This kind of mechanical-force–promoted assembly was also observed with different peptides on various substrates. The force promoting peptide assembly provides a simple and practical solution for preparing and building peptide and protein architectures for future nanodevices.

368

We report the multiplicity dependence of charged particle production for the π^±, K^±, p, p¯, and ϕ mesons at |y| < 1.0 in p+p collisions at s = 200 GeV from a PYTHIA simulation. The impact of multiple parton interactions and gluon contributions is studied and found to be a possible source of the splitting of the particle yields as a function of p_T with respect to the multiplicity. No obvious particle species dependence of the splitting is observed. The multiplicity dependence of the ratios K^-/π^-, K⁺/π⁺, p¯/π−, p/π⁺, and Λ/Ks0 at mid-rapidity in p+p collisions is found to follow a tendency similar to that in Au+Au collisions at sNN = 200 GeV at the Relativistic Heavy Ion Collider, indicating similar underlying initial production mechanisms despite the differences in the initial colliding systems.

415