Vol.28,

Effective atomic numbers for photon energy absorption (ZPEAeff) and their corresponding electron numbers (NPEAeff), and effective macroscopic removal cross-sections of fast neutrons (Σ_R) were calculated for 27 different types of three-dimensional (3D) dosimeters, four types of phantom materials, and water. The values of ZPEAeff and NPEAeff were obtained using the direct method for energies ranging from 10 keV to 20 MeV. Results are presented relative to water, for direct comparison over the range of examined energies. The effect of monomers that are used in polymer gel dosimeters on the water equivalence is discussed. The relation between Σ_R and hydrogen content was studied. Micelle gel dosimeters are highly promising because our results demonstrate perfect matching between the effective atomic number, electron density number, and fast neutron attenuation coefficient of water.

529

The extraction chromatography–electrodeposition (EC–ED) process was proposed for the quantitative recovery of palladium from high level liquid waste (HLLW) in this study. The process coupled the extraction chromatography method to obtain the decontamination of Pd(II) from HLLW with the electrochemical method to recover metallic palladium from the concentrated solution. Separation of Pd(II) from a nitric acid medium by extraction chromatography using isoBu-BTP/SiO₂-P adsorbent and the electrochemical behavior of Pd(II) in nitric acid solution in the presence of thiourea (TU) were investigated. isoBu-BTP/SiO₂-P exhibited a high selectivity for Pd(II) over other fission products (FPs) and Pd(II) could be desorbed by TU from loaded BTP/SiO₂-P. The adsorbent performed good stability against HNO₃ because the adsorption performance kept Pd(II) after extended contact with HNO₃ solution. The column experiment achieved the separation of Pd(II) from simulated HLLW successfully. The electrochemical behavior of Pd(II) in palladium desorption solution containing TU and nitric acid was investigated at a platinum electrode by cyclic voltammetry. A weak reduction wave at -0.4 V was due to the reduction of Pd(II) to Pd(0) and the deposition process was irreversible. In electrowinning experiments, a maximum of 92% palladium could be obtained.

351

The exact calculation of point kinetic parameters is very important in nuclear reactor safety assessment and most sophisticated safety codes such as RELAP5, PARCS, DYN3D, PARET, are using these parameters in their dynamic models. These parameters include effective delayed neutron fractions as well as mean generation time. These parameters are adjoint weighted, and adoint flux is employed as a weighting function in their evaluation. Adjoint flux calculation is an easy task for most of deterministic codes, but its evaluation is cumbersome for Monte Carlo codes. However, in recent years, some sophisticated techniques have been proposed for Monte Carlo based point kinetic parameters calculation without any need of adjoint flux. The most straightforward scheme is known as the "Prompt Method" and has been used widely in literature. The main objective of this article is dedicated to point kinetic parameters calculation in Tehran Research Reactor (TRR) using deterministic as well as probabilistic techniques. WIMS-D5B and CITATION codes have been used in deterministic calculation of forward and adjoint fluxes in the TRR core. On the other hand, the MCNP Monte Carlo code has been employed in the "Prompt Method" scheme for effective delayed neutron fraction evaluation. Deterministic results have been cross checked with probabilistic ones and validated with SAR and experimental data. In comparison with experimental results, the relative differences of deterministic as well as probabilistic methods are 7.6% and 3.2%, respectively. These quantities are 10.7% and 6.4% respectively in comparison with SAR report.

381

The embrittlement of nickel-based structural alloys by fission-produced tellurium (Te) is a major challenge for molten salt reactors (MSR). In this study, the effects of thermal exposure time on tellurium diffusion in a candidate MSR structural alloy (Ni-16Mo-7Cr-4Fe) and the consequent mechanical property degradation of the alloy were investigated through surrogate diffusion experiments at 700°C. The results show that some tellurium reacted with the alloy to form tellurides on the surface, while some tellurium diffused into the alloy along grain boundaries. Ni₃Te₂ and CrTe were the most stable reaction products at the tested temperature, and the formation of CrTe on the surface induced the Cr depletion at grain boundaries of the alloy. The diffusion depth of Te increased gradually with thermal exposure time, and the diffusion rate kept stable within the test duration of up to 3000 h. The Te diffusion in the alloy caused the embrittlement of grain boundaries, inducing crack formation and strength degradation in tensile test at room temperature.

359

Electron beams of 0.5, 1.5, 2.0 and 5.0 MeV were used to irradiate n-Si diodes to fluences of 5.5×10¹³, 1.7×10¹⁴ and 3.3×10¹⁴ electrons/cm². The forward voltage drop, minority carrier lifetime, and deep level transient spectroscopy (DLTS) characteristics of silicon p-n junction diodes before and after irradiation were compared. At the fluence of 3.3×10¹⁴ e/cm², the forward voltage drop increased from 1.25 V at 0.5 MeV to 7.96 V at 5.0 MeV, while the minority carrier lifetime decreased significantly from 7.09 μs at 0.5 MeV to 0.06 μs at 5. 0 MeV. Six types of changes in the energy levels in DLTS spectra were analyzed and discussed.

587

A design for precise scanning magnetic field control for the beam delivery system of the Shanghai Advanced Proton Therapy Facility (APTRON) is presented in this paper. With a novel feedforward algorithm to compensate for magnet hysteresis, the scanning magnetic field can be controlled to within a precision of ±2.5 G. The main advantage of the proposed feedforward algorithm is that the average settling time is shorter compared with that of a conventional feedback algorithm with acceptable tolerance.

533

Eddy currents produced by a time-varying magnetic field will introduce time delay, and thus affect field quality. This effect leads to drifting of the beam position over time, especially for a compact synchrotron. Simulations and measurements of different dipoles have been performed, to investigate the time delay and field quality. The simulations are conducted using OPERA software. The measurements are conducted using a long coil and Hall sensor. All results show that the magnetic field deviation is up to 0.4% for the dipole with stainless steel endplates. The simulations show that the main sources of eddy current are the field saturation effect and the field component B_z, introduced by the bedstead-type coil. Field correction using a power supply is adopted to reduce the deviation to less than 0.02%.

444

Surface morphology, compositions, microstructure and optical properties of GaN film irradiated by highly-charged Kr^q+ (q=23, 15, 11) in two geometries to a fluence of 1×10¹⁵ kr^q+/cm² were studied using AFM, XPS, PL,Raman scattering and UV-visible spectroscopy. The AFM observation shows that the irradiated GaN area is a swollen terrace. The swelling rate increased with the charge state (potential energy). For the same charge state, the swelling rate of tilted incidence was greater than that for normal incidence. The XPS measurements reveal that N deficiency, Ga enrichment and Ga-O and Ga dangling bonds generated on the irradiated GaN surface increased with the charge state, and more N were lost for normal incidence than that for tilted incidence. The UV-vis results show that the transmittance decreased with increasing charge state. For the same charge state, the transmittance for tilted incidence is higher than that for normal incidence. The PL spectra present that, with increasing charge state, the YL band intensity decreased, with a blueshift in its peak position; while the NBE peak intensity increased first and then reduces, and a blue luminescence band appeared. A rapid quenching of both the YL and the NEB for normal incidence was observed. Raman spectra display that screw dislocations perhaps were produced near the surface for normal incidence.

376

This paper is aimed at detecting the neutron spectrum of ²⁴¹Am-Be, a widely used neutron source, with the SP9 ³He proportional counter, which is a multi-sphere spectrometer system of eight thermal neutron detectors embedded in eight polyethylene (PE) spheres of varying diameters. The transport processes of a neutron in the multi-sphere spectrometer are simulated using the Geant4 code. Two sets of response functions of the PE spheres are obtained for calculating the ²⁴¹Am-Be neutron spectrum. Response Function 1 utilizes the thermal neutron scattering model G4NeutronHPThermalScattering for neutron energies of ≤4 eV, and Response Function 2 has no thermal treatment. Neutron spectra of an ²⁴¹Am-Be neutron source are measured and compared those calculated by using the response functions. The results show that response function with thermal treatment is more accurate and closer to the real spectrum.

388

452

Ab initio calculations of nuclei face the challenge of simultaneously describing strong short-range internucleon correlations and the long-range properties of weakly-bound halo nucleons. Natural orbitals, which diagonalize the one-body density matrix, provide a basis which is better matched to the physical structure of the many-body wave function. We demonstrate that the use of natural orbitals significantly improves convergence for ab initio no-core configuration interaction calculations of the neutron halo nucleus ⁶He, relative to the traditional oscillator basis.

492

As the high density nuclear equation of state (EOS) is not very well constrained, we suggest that the structural properties from the finite systems can be used to extract a more accurate constraint. By including the strangeness degrees of freedom, the hyperon or anti-kaon, the finite systems can then have a rather high density core which is relevant to the nuclear EOS at high densities directly. It is found that the density dependence of the symmetry energy is sensitive to the properties of multi-Λ hypernuclei, while the high density EOS of symmetric matter correlates sensitively to the properties of kaonic nuclei.

565

We examine critically how tightly the density dependence of nuclear symmetry energy E_sym(ρ) is constrained by the universal equation of state (EOS) of the unitary Fermi gas E_UG(ρ) considering currently known uncertainties of higher order parameters describing the density dependence of the Equation of State of isospin-asymmetric nuclear matter. We found that E_UG(ρ) does provide a useful lower boundary for the E_sym(ρ). However, it does not tightly constrain the correlation between the magnitude E_sym(ρ₀ and slope L unless the curvature K_sym of the symmetry energy at saturation density ρ₀ is more precisely known. The large uncertainty in the skewness parameters affects the E_sym(ρ₀ versus L correlation by the same almost as significantly as the uncertainty in K_sym.

422

With taking electromagnetic field into account for the transport model of Boltzmann-Uehling-Uhlenbeck, electromagnetic effects are studied for ²⁰⁸Pb+²⁰⁸Pb collisions around 100A MeV. Electromagnetic field evolution during the collisions was estimated. It was found that the electric field has an obvious effect on the transverse momentum (p_T) spectra of nucleons during heavy ion collisions, and leads to different minimum position for the peak of p_T spectra of nucleons versus beam energy when the electric field is switched on. For the magnetic field, it affects the z-axis direction distributions of nucleons for central heavy ion collisions at lower energy.

410

Recent progress in nuclear data measurement for ADS at Institute of Modern Physics (IMP) is reviewed briefly. Based on the Cooler Storage Ring of the Heavy Ion Research Facility in Lanzhou (HIRFL-CSR), nuclear data terminal was established. The nuclear data measurement facility for the ADS spallation target has been constructed, which provides a very important platform for the experimental measurements of spallation reactions. A number of experiments have been conducted in the nuclear data terminal. A Neutron Time-of-Flight (NTOF) spectrometer was developed for the study of neutron production from spallation reactions related to the ADS project. The experiments of 400 MeV/u ¹⁶O bombarded on a Tungsten target were presented using a NTOF spectrometer. Neutron yields for 250 MeV protons incident on a thick grain-made tungsten target and a thick solid lead target have been measured using the water-bath neutron activation method. Spallation residual productions were studied by bombarding W and Pb targets with a 250 MeV proton beam using the neutron activation method. Benchmarking of evaluated nuclear data libraries was performed for D-T neutrons on ADS relevant materials by using the benchmark experimental facility at the China Institute of Atomic Energy.

571

Within the nonlinear relativistic mean field (NL-RMF) model, we show that both the pressure of symmetric nuclear matter at supra-saturation densities and the maximum mass of neutron stars are sensitive to the skewness coefficient, J₀, of symmetric nuclear matter. Using experimental constraints on the pressure of symmetric nuclear matter at supra-saturation densities from flow data in heavy ion collisions and the astrophysical observation of a large mass neutron star PSR J0348+0432, with the former favoring a smaller J₀ while the latter favors a larger J₀, we extract a constraint of -494 MeV≤J₀≤-10 MeV based on the NL-RMF model. This constraint is compared with the results obtained in other analyses.

470