Vol.28,

Some kinds of break in the reactor coolant system may cause the coolant to exit rapidly from the failure site, which leads to the loss of coolant accident (LOCA). In this paper, a stress analysis of an AP1000 reactor containment is performed in an LOCA, with the passive containment cooling system (PCCS) being available and not available for cooling the wall’s containment. The variations in the mechanical properties of the wall’s containment, including elastic modulus, strength, and stress are analyzed using the ABAQUS code. A general two-phase model is applied for modeling thermal-hydraulic behavior inside the containment. Obtained pressure and temperature from thermal-hydraulic models are considered as boundary conditions of the ABAQUS code to obtain distributions of temperature and stress across steel shell of the containment in the accident. The results indicate that if the PCCS fails the peak pressure inside the containment exceeds the design value. However, the stress would still be lower than the yield stress value, and no risk would threaten the integrity of the containment.

470

The solid-fueled thorium molten salt reactor (TMSR-SF1) is a 10 MW_th test reactor design to be deployed in 5 to 10 years by the TMSR group. Its design combines coated particle fuel and molten FLiBe coolant for great intrinsic safety features and economic advantages. Due to a large amount of beryllium in the coolant salt, photoneutrons are produced by (γ, n) reaction, hence the increasing fraction of effective delayed neutrons in the core by the photoneutrons originating from the long-lived fission products. Some of the delayed photoneutron groups are of long lifetime, so a direct effect is resulted in the transient process and reactivity measurement. To study the impact of photoneutrons for TMSR-SF1, the effective photoneutron fraction is estimated using k-ratio method and performed by the Monte Carlo code (MCNP5) with ENDF/B-VII cross sections. Based on the coupled neutron-photon point kinetics equations, influence of the photoneutrons is analyzed. The results show that the impact of photoneutrons is not negligible in reactivity measurement. Without considering photoneutrons in on-line reactivity measurement based on inverse point kinetics can result in overestimation of the positive reactivity and underestimation of the negative reactivity. The photoneutrons also lead to more waiting time for the doubling time measurement. Since the photoneutron precursors take extremely long time to achieve equilibrium, a "steady" power operation may not directly imply a "real" criticality.

552

Chrome-molybdenum steel (2·1/4Cr1Mo) is one of the main products of steam generation. The adsorption behaviors of radioactive fission products on 2·1/4Cr1Mo surface are critical in the analysis of HTR-PM. Here, the adsorption behavior of cesium, strontium, silver and iodine on 2·1/4Cr1Mo were investigated with first-principle calculations. The Ag and I atoms prefer to be adsorbed at the square hollow site of the face-centered cubic iron cell with a binding energy of about 1 eV and 3 eV, respectively. In contrast, Cs and Sr atoms are not adsorbed on the surface of the 2·1/4Cr1Mo. These results are again confirmed via analysis of charge density differences and the densities of state. Furthermore, the adsorption rates of these fission products show that only I and Ag have significant adsorption on the metal substrate. These adsorption results explain the amount of adsorbed radionuclides for an evaluation of nuclear safety in HTR-PM. These micro-pictures of the interaction between fission products and materials are a new and useful way to analyze the source term.

543

587

Film condensation is a vital phenomenon in the nuclear engineering applications, such as the gas-steam pressurizer design, and heat removing on containment in the case of postulated accident. Reynolds number in film condensation can be calculated from either the mass relation or the energy relation, but few researches have distinguished the difference between them at present. This paper studies the effect of Reynolds correlation in the natural convection film condensation on the outer tube. The general forms of the heat transfer coefficient correlation of film condensation are developed in different flow regimes. By simultaneously solving a set of the heat transfer coefficient correlations with Re_mass and Re_energy, the general expressions for Re_mass and Re_energy and the relation between the corresponding heat transfer coefficients are obtained. In the laminar and wave-free flow regime, Re_mass and Re_energy are equivalent, while in the laminar and wavy flow regime, Re_mass is much smaller than Re_energy, and the deviation of the corresponding average heat transfer coefficients is about 30% at the maximum. In the turbulent flow regime, the relation of Re_mass and Re_energy is greatly influenced by Prandtl number. The relative deviation of their average heat transfer coefficients are the non-linear function of Reynolds number and Prandtl number. Compared with experimental results, the heat transfer coefficient calculated from Re_energy is more accurate.

456

Ptychography is a diffraction-based X-ray microscopy technique in which an extended sample is scanned by a coherent beam with overlapped illuminated areas and complex transmission function of the sample is obtained by applying iterative phase retrieval algorithms to the diffraction patterns recorded at each scanned position. It permits quantitatively imaging of non-crystalline specimens at a resolution limited only by the X-ray wavelength and the maximal scattering angle detected. In this paper, the development of soft X-ray ptychography method at the BL08U1A beamline of Shanghai Synchrotron Radiation Facility (SSRF) is presented. The experimental setup, experimental parameters selection criteria, and post-experimental data analyzing procedures are presented in detail with a prospect of high resolution image reconstruction in real time. The performance of this newly implemented method is demonstrated through the measurements of a resolution test pattern and two real samples: Pt-Co alloy nanoparticles and a breast cancer cell. The results indicate that strong scattering specimens can be reconstructed to sub-20 nm resolution while a sub-25 nm resolution for biological specimens can be achieved.

482

Significant temperature difference (300 K to 77 K or even 4 K) can cause large deformations and displacements of the beam position monitors (BPMs), which affect BPMs measurement resolution or even cause their malfunction in cryogenic situations. In this paper, to check the offset from the mechanical to electrical center in low-temperature (77 K), Fourier's law and finite element method are used to simulate cryo-deformation. Laser tracker and micro-alignment telescope are employed in combined BPM calibration, installation and monitoring. The calibration error is <0.02 mm, and the installation and monitoring precision are 0.06 mm and 0.01 mm, respectively. The monitored cryo-deformation agrees well with the simulation results. These indicate that the combined alignment can improve performance of the BPM system. All these guaranteed the success of running the 9.55 MeV@2.14 mA cw protons.

682

The Water Cherenkov Detector Array (WCDA) is an important part of the Large High-Altitude Air Shower Observatory (LHAASO), which is in a research and development phase. The central scientific goal of LHAASO is to explore the origin of high-energy cosmic rays of the universe and to push forward the frontier of new physics. To simplify the WCDA’s readout electronics, a prototype of a front-end readout for an application-specific integrated circuit (ASIC) is designed based on the time-over-threshold method to achieve charge-to-time conversion. High-precision time measurement and charge measurement is necessary over a full dynamic range (1~4000 photo electrons [P.E.]). To evaluate the performance of this ASIC, a test system is designed that includes the front-end ASIC test module, digitization module, and test software. The first module needs to be customized for different ASIC versions, whereas the digitization module and test software are tested for general-purpose use. In the digitization module, a field programmable gate array based time-to-digital converter is designed with a bin size of 333 ps, which also integrates an inter-integrated circuit to configure the ASIC test module, and a universal serial bus interface is designed to transfer data to the remote computer. Test results indicate that the time resolution is better than 0.5 ns, and the charge resolution is better than 30% root mean square (RMS) at 1 P.E. and 3% RMS at 4000 P.E., which are beyond the application requirements.

430

A front-end electronics of dose monitor has been developed for measuring irradiation dose to the patient in Shanghai Advanced Proton Therapy Facility. The parallel plate ionization chamber (PPIC) is used for the dose monitoring. Unlike the traditional method of recycling capacitor integration and voltage-to-frequency (V/F) conversion, this dose monitor electronics uses the trans-impedance amplifier and analog-to-digital (A/D) conversion method. It performs satisfactorily, with the integral non-linearity (INL) of less than ± 0.04 nA in the range of−400 nA to 50nA and the resolution of about ± 0.6 nA.

376

Identifying the geometric information of an object by analyzing the detected radiation fields is an important problem for national and global security. In the present work, an inverse radiation transport model, based on the enhanced differential evolution algorithm with global and local neighborhoods (IRT-DEGL), is developed to estimate the unknown layer thickness of the source/shield system with the gamma-ray spectrum. The framework is briefly introduced with the emphasis on handling the enhanced differential evolution algorithm. Using the simulated gamma-ray spectra, the numerical precision of the IRT-DEGL model is evaluated for one-dimensional source systems. Using the detected gamma-ray spectra, the inverse investigations for the unknown thicknesses of multiple shielding layers are performed. By comparing with the traditional gamma-ray absorption method, it is shown that the IRT-EDGL model can provide a much more accurate result and has great potential to be applied for the complicated systems.

484

To improve the affinity between separators and electrolyte in lithium ion battery, micro-porous polyethylene (PE) separator was grafted of polyacrylamide (PAAm) by radiation. Chemical structure of the PAAm-grafted PE separators (denoted as PE-g-PAAm) was characterized by Fourier transform infrared (FT-IR) spectroscopy and X-ray photoelectron spectroscopy (XPS). Properties of the pristine PE and PE-g-PAAm were tested by scanning electron microscope (SEM), liquid electrolyte uptake and lithium-ion conductivity. Electrochemical performances of the grafted PE separators (up to 0.76×10⁻³S/cm of ionic conductivity at room temperature) was much better than pristine PE, and performance of the battery with the grafted separator behaved better than with the virgin PE separator, under the same condition (assembled in Ar-filled glove box).

453

Extractability and extraction mechanism of lanthanide ions were investigated by using a new extractant, N,N,N′,N′-tetrabutyl -3-oxa-diglycolamide (TBDGA), in toluene from nitric acid media. The effects of HNO₃ and TBDGA concentrations, and temperature, on extraction of lanthanide ions were studied. Soichiometries of the main extracted species were HNO₃·TBDGA and M(NO₃)₃·3TBDGA(M= Er, Dy, Tb, Gd, La, Ce, Nd, Sm and Eu). The extracted species for metal ions were established to be ionic complex. In this complex, nitrate anion was not coordinated to the central ion. The extraction pattern increased gradually across the lanthanide ions series, showing enhanced affinity of TBDGA toward heavy lanthanide ions. Thermodynamic parameters were investigated for the exothermic extraction reaction.

494

Fast neutron radiography (FNR) is an effective non-destructive testing technique. Due to the scattering effect and low detection efficiency, the detection limit of FNR under certain conditions cannot be determined. In order to obtain the minimum detectable thickness by FNR, we studied the contrast sensitivity of FNR lead samples, both theoretically and experimentally. We then clarified the relationship between pixel value and irradiation time, and sample materials and thickness. Our experiment, using a 4-cm-thick lead sample, verified our theoretical expression of FNR contrast sensitivity.

466

A minitype reference radiation (MRR) with dimensions of only 1m×1m×1m has been developed for the in situ calibration of photon dosimeters. The present work conducts a feasibility study on determining the conventional true air kerma (CAK) value for gamma-rays at the point of test in the MRR. Owing to its smaller dimensions, the scattered gamma-rays in the MRR are expected to induce a non-negligible interference with the radiation field compared with conditions in the standard reference radiation stipulated by ISO4037-1 or GB/T12162.1. A gamma-ray spectrometer was employed to obtain the spectra of scattered gamma-rays within the MRR, and the feature components of the spectra were extracted by principal component analysis to characterize the interference of a dosimeter probe in the radiation field. A prediction model of the CAK at the point of test was built by least squares support vector machine based on the feature component data obtained from nine sample dosimeters under five different dose rates. The mean prediction error of the CAK prediction model was within ±4.5%,and the maximum prediction error was about ±10%.

366

Multiphase flow meters as the potential alternatives to separation and metering techniques have been in rapid development since 1980s. Before its field operation, the instrument should be calibrated in a standard test-facility. In spite of the known medium and large scale facilities all over the world, we developed a laboratory scale instrument for component fraction measurements. It has a two-phase flow homogenizer loop with the clamp-on potential of the meters to provide a regime independent measurement. It is capable of delivering a complete homogenization by γ-ray densitometer. With an error of ±5% in component fraction measurements, this instrument is appropriate for testing and calibrating other meters.

511

In this study, a comprehensive investigation on different cluster configurations of the ⁹Be nucleus is performed with a simple cluster approach. With this goal, the elastic scattering angular distributions of ⁹Be by ²⁷Al, ²⁸Si, ⁶⁴Zn, ¹⁴⁴Sm, ²⁰⁸Pb, and ²⁰⁹Bi target nuclei are reanalyzed for α + α + n, d + ⁷Li, ³H + ⁶Li, ³He + ⁶He and n + ⁸Be cluster configurations of the ⁹Be projectile within the framework of the optical model. The theoretical results are compared with each other as well as the experimental data. The results provide an opportunity for a test of different cluster configurations in explaining the elastic scattering of ⁹Be nucleus.

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