Tài liệu miễn phí Năng lượng
Download Tài liệu học tập miễn phí Năng lượng
Interaction of NpOþ 2 with Cle in NaeCaeCl-type solutions at ionic strength of 6M: Effect of presence of Ca ion on interaction
The interaction of NpOþ 2 with Cle was studied using visibleenear-infrared spectroscopy in NaCleCaCl2eNaClO4, NaCleNaClO4, and CaCl2eNaClO4 solutions with ionic strength (I) of 6M. The spectra of NpOþ 2 around 980 nm varied with Cle concentration in the NaCleCaCl2eNaClO4 and NaCleNaClO4 solutions at [Cle] 3.5M, but not in the CaCl2eNaClO4 solution. Assuming the 1:1 interaction between NpOþ 2 and Cle, the apparent equilibrium constants at I ¼ 6M were evaluated.
7/4/2019 5:06:47 AM +00:00
Effect of high-energy neutron source on predicting the proton beam current in the ADS design
The results show that high-energy neutrons with En > 20 MeV are of small fraction (2.6%) in the neutron source, but their contribution to the source efficiency is about 23% for the large scale ADS. Based on this, a neutron source efficiency correction factor is proposed. Tests show that the new correction method works well in the ADS calculation. This method can effectively improve the accuracy of the prediction of the proton beam current.
7/4/2019 5:06:27 AM +00:00
A lumped parameter method of characteristics approach and multigroup kernels applied to the subgroup self-shielding calculation in MPACT
The neutron transport code, MPACT, is currently using the subgroup self-shielding method, in which the method of characteristics (MOC) is used to solve purely absorbing fixed-source problems. Recent efforts incorporating multigroup kernels to the MOC solvers in MPACT have reduced runtime by roughly 2. Applying the same concepts for self-shielding and developing a novel lumped parameter approach to MOC, substantial improvements have also been made to the self-shielding computational efficiency without sacrificing any accuracy
7/4/2019 5:06:10 AM +00:00
Clustering and traveling waves in the Monte Carlo criticality simulation of decoupled and confined media
In this paper we will build a timedependent diffusion equation that takes into account both spatial correlations and population control (fixed number of neutrons along generations). We will show that its solution obeys a traveling wave dynamic, and we will discuss the mechanism that explains this biasing of local tallies whenever leakage boundary conditions are applied to the system.
7/4/2019 5:05:46 AM +00:00
A multilevel in space and energy solver for multigroup diffusion eigenvalue problems
n this paper, we present a new multilevel in space and energy diffusion (MSED) method for solving multigroup diffusion eigenvalue problems. The MSED method can be described as a PI scheme with three additional features: (1) a grey (one-group) diffusion equation used to efficiently converge the fission source and eigenvalue, (2) a space-dependent Wielandt shift technique used to reduce the number of PIs required, and (3) a multigrid-in-space linear solver for the linear solves required by each PI step.
7/4/2019 5:05:25 AM +00:00
Particle tracking acceleration via signed distance fields in direct-accelerated geometry Monte Carlo
This work describes the adaptation of a rendering data structure, the signed distance field, as a geometric query tool for accelerating CAD-based transport in the direct-accelerated geometry Monte Carlo toolkit. Demonstrations of its effectiveness are shown for several problems. The beginnings of a predictive model for the data structure's utilization based on various problem parameters is also introduced.
7/4/2019 5:05:05 AM +00:00
Multilevel acceleration of scattering-source iterations with application to electron transport
Acceleration/preconditioning strategies available in the SCEPTRE radiation transport code are described. A flexible transport synthetic acceleration (TSA) algorithm that uses a low-order discrete-ordinates (SN) or spherical-harmonics (PN) solve to accelerate convergence of a high-order SN source-iteration (SI) solve is described. Convergence of the low-order solves can be further accelerated by applying off-the-shelf incomplete-factorization or algebraic-multigrid methods.
7/4/2019 5:04:48 AM +00:00
Integral nuclear data validation using experimental spent nuclear fuel compositions
Measurements of the isotopic contents of spent nuclear fuel provide experimental data that are a prerequisite for validating computer codes and nuclear data for many spent fuel applications. Under the auspices of the Organisation for Economic Co-operation and Development (OECD) Nuclear Energy Agency (NEA) and guidance of the Expert Group on Assay Data of Spent Nuclear Fuel of the NEA Working Party on Nuclear Criticality Safety, a new database of expanded spent fuel isotopic compositions has been compiled.
7/4/2019 5:04:29 AM +00:00
Hydrogen's influence on reduced activation ferritic/martensitic steels' elastic properties: density functional theory combined with experiment
Reduced activation ferritic/martensitic (RAFM) steels are widely applied as structural materials in the nuclear industry. To investigate hydrogen's effect on RAFM steels' elastic properties and the mechanism of that effect, a procedure of first principles simulation combined with experiment was designed. Density functional theory models were established to simulate RAFM steels' elastic status before and after hydrogen's insertion.
7/4/2019 5:04:12 AM +00:00
In-line (a,n) source sampling methodology for monte carlo radiation transport simulations
The new method uses a continuous-slowing-down model coupled with (a,n) cross section data to precompute the expected neutron yield over the alpha particle lifetime. This eliminates the complexity and computational cost associated with explicit charged particle transport. When combined with an integrated alpha particle decay source sampling capability.
7/4/2019 5:03:52 AM +00:00
A new approach to the stabilization and convergence acceleration in coupled Monte CarloeCFD calculations: The Newton method via Monte Carlo perturbation theory
This paper proposes the adoption of Monte Carlo perturbation theory to approximate the Jacobian matrix of coupled neutronics/thermal-hydraulics problems. The projected Jacobian is obtained from the eigenvalue decomposition of the fission matrix, and it is adopted to solve the coupled problem via the Newton method.
7/4/2019 5:03:33 AM +00:00
Recent developments in the GENESIS code based on the Legendre polynomial expansion of angular flux method
This paper describes recent development activities of the GENESIS code, which is a transport code for heterogeneous three-dimensional geometry, focusing on applications to reactor core analysis. For the treatment of anisotropic scattering, the concept of the simplified Pn method is introduced in order to reduce storage of flux moments.
7/4/2019 5:03:13 AM +00:00
Processing and benchmarking of evaluated nuclear data file/b-viii.0b4 cross-section library by analysis of a series of critical experimental benchmark using the monte carlo code MCNP(X) and NJOY2016
The results obtained with the ENDF/BVIII.0b4 library were compared against those calculated with ENDF/B-VI.8, ENDF/B-VII.0, and ENDF/BVII.1 libraries using the Monte Carlo N-Particle (MCNP(X)) code. All the MCNP(X) calculations of keff values with these four libraries were compared with the experimentally measured results, which are available in the International Critically Safety Benchmark Evaluation Project. The obtained results are discussed and analyzed in this paper.
7/4/2019 5:02:59 AM +00:00
Neutron and gamma-ray energy reconstruction for characterization of special nuclear material
Characterization of special nuclear material may be performed using energy spectroscopy of either the neutron or gamma-ray emissions from the sample. Gamma-ray spectroscopy can be performed relatively easily using high-resolution semiconductors such as high-purity germanium. Neutron spectroscopy, by contrast, is a complex inverse problem. Here, results are presented for 252Cf and PuBe energy spectra unfolded using a single EJ309 organic scintillator; excellent agreement is observed with the reference spectral.
7/4/2019 5:02:44 AM +00:00
Dynamics and control of molten-salt breeder reactor
A brief overview of the model followed by results from simulations performed to validate the model is presented. Simulations illustrate stable behavior of the reactor dynamics and temperature feedback effects to reactivity excursions. Stable and smooth changes at various nodal temperatures are also observed. Control strategies for molten-salt reactor operation are discussed, followed by an illustration of the open-loop load-following capability of the molten-salt breeder reactor system. It is observed that the molten-salt breeder reactor system exhibits “self-regulating” behavior, minimizing the need for external controller action for load-following maneuvers.
7/4/2019 5:02:24 AM +00:00
Beta particle energy spectra shift due to self-attenuation effects in environmental sources
In order to predict and control the environmental and health impacts of ionizing radiation in environmental sources such as groundwater, it is necessary to identify the radionuclides present. Beta-emitting radionuclides are frequently identified by measuring their characteristic energy spectra. The present work shows that self-attenuation effects from volume sources result in a geometry-dependent shift in the characteristic spectra, which needs to be taken into account in order to correctly identify the radionuclides present.
7/4/2019 5:02:07 AM +00:00
Mechanical analysis of surface-coated zircaloy cladding
This study suggests that the compatibility of the high temperature irradiationinduced strains (axial growth and creep) between zircaloy and the coating layer and the capability to undergo plastic strain should be taken as key metrics, along with the traditional focus on chemical protectiveness.
7/4/2019 5:01:43 AM +00:00
Atomistic simulations of nanocrystalline U0.5Th0.5O2 solid solution under uniaxial tension
The simulated nanocrystalline U0.5Th0.5O2 exhibited a breakdown in the HallePetch relation with mean grain size varying from 3.0 nm to 18.0 nm. Moreover, the elastic modulus of U1-yThyO2 solid solutions with different content of thorium at 300 K was also studied and the results accorded well with the experimental data available in the literature. In addition, the fracture mode of nanocrystalline U0.5Th0.5O2 was inclined to be ductile because the fracture behavior was preceded by some moderate amount of plastic deformation, which is different from what has been seen earlier in simulations of pure UO2.
7/4/2019 5:01:16 AM +00:00
Effect of emergency core cooling system flow reduction on channel temperature during recirculation phase of large break loss-of-coolant accident at Wolsong unit 1
The feasibility of cooling in a pressurized heavy water reactor after a large break loss-of-coolant accident has been analyzed using Multidimensional Analysis of Reactor Safety-KINS Standard code during the recirculation phase. Through evaluation of sensitivity of the fuel channel temperature to various effective recirculation flow areas, it is determined that proper cooling of the fuel channels in the broken loop is feasible if the effective flow area remains above approximately 70% of the nominal flow area.
7/4/2019 5:00:52 AM +00:00
On the effect of temperature on the threshold stress intensity factor of delayed hydride cracking in light water reactor fuel cladding
This work studies the threshold stress intensity factor (KIH) to initiate DHC as a function of temperature in Zry-4 for temperatures between 227C and 315C. The experimental technique used in this study was the pin-loading testing technique. To determine the KIH, an unloading method was used where the load was successively reduced in a stepwise manner until no cracking was observed during 24 hours.
7/4/2019 5:00:38 AM +00:00
The mechanical design and fabrication of 162.5 MHz buncher for China accelerator driven sub-critical system injector II
According to the beam transmission matching of the MEBT and the geometric parameters requirements of bunchers, the unique mechanical structure and the main processing technology of buncher cavities and their couplers and tuners are described in this paper. The fabrication of bunchers and their parts have been completed and tested at high power, the test results agree well with the design requirements. These bunchers work well for about two years in Institute of Modern Physics, Chinese Academy of Sciences.
7/4/2019 5:00:17 AM +00:00
Development of a Korean roadmap for technical issue resolution for fission product behavior during severe accidents
The group members developed a tree to identify fission product release phenomena by tracing failures of individual defense-in-depth barriers and added possible countermeasures against failure. For each elemental issue, they searched for technical problems by examining the phenomena, accident management actions, and regulatory aspects relevant to the mitigation features for containment, including mitigation strategies against containment bypass accidents.
7/4/2019 4:59:46 AM +00:00
Statistical analysis on the fluence factor of surveillance test data of Korean nuclear power plants
In this study, the TTS trend of the Korean surveillance test results was analyzed using a nonlinear regression model and a mixed-effect model based on the power function. The nonlinear regression model yielded a similar exponent as the power function in the fluence compared with RG1.99/ 2. The mixed-effect model had a higher value of the exponent and showed superior goodness of fit compared with the nonlinear regression model. Compared with RG1.99/2 and RG1.99/3, the mixed-effect model provided a more accurate prediction of the TTS.
7/4/2019 4:59:22 AM +00:00
Unsteady heat exchange at the dry spent nuclear fuel storage
The time delays in the reaching of maximal temperatures for each spent fuel assembly were calculated. Results of numerical investigations show that daily fluctuation of outer temperatures does not have a large influence on the maximal temperatures of stored spent fuel, so that fluctuation can be neglected and only daily average temperature should be considered for safety estimation using the “best estimation” approach.
7/4/2019 4:58:59 AM +00:00
Statistical model for forecasting uranium prices to estimate the nuclear fuel cycle cost
This paper presents a method for forecasting future uranium prices that is used as input data to calculate the uranium cost, which is a rational key cost driver of the nuclear fuel cycle cost. In other words, the statistical autoregressive integrated moving average (ARIMA) model and existing engineering cost estimation method, the so-called escalation rate model, were subjected to a comparative analysis.
7/4/2019 4:58:42 AM +00:00
Fatigue crack growth characteristics of nitrogen-alloyed type 347 stainless steel under operating conditions of a pressurized water reactor
The fatigue crack growth behavior of Type 347 (S347) and Type 347N (S347N) stainless steel was evaluated under the operating conditions of a pressurized water reactor (PWR). These two materials showed different fatigue crack growth rates (FCGRs) according to the changes in dissolved oxygen content and frequency. Under the simulated PWR conditions for normal operation, the FCGR of S347N was lower than that of S347 and insensitive to the changes in PWR water conditions.
7/4/2019 4:58:15 AM +00:00
Analysis of radioactivity levels and hazard assessment of black sand samples from Rashid area, Egypt
The aim of this study is to evaluate the radioactivity levels and radiological impacts of representative black sand samples collected from different locations in the Rashid area, Egypt. These samples were prepared and then analyzed using the high-resolution gamma ray spectroscopy technique with a highpurity germanium detector.
7/4/2019 4:57:58 AM +00:00
High-power fiber laser cutting parameter optimization for nuclear Decommissioning
This study aims to improve the reliability of laser cutting for such work and indicates guidelines to optimize the cutting procedure, in particular, nozzle combinations (standoff distance and focus position), to minimize waste material. The results obtained show the performance levels that can be reached with 10 kW fiber lasers, using which it is possible to obtain narrower kerfs than those found in published results obtained with other lasers. Nonetheless, fiber lasers appear to show the same effects as those of CO2 and ND:YAG lasers.
7/4/2019 4:57:38 AM +00:00
Neutron activation analysis: Modelling studies to improve the neutron flux of AmericiumeBeryllium source
This study achieved multiple advantageous results: primarily, it will help us perform neutron activation analysis. Next, it will give us the opportunity to produce radio-elements with short half-lives. Am-Be single and multisource (5 sources) experiments were performed within an irradiation facility with a paraffin moderator. The resulting models mainly increase the thermal neutron flux compared to the traditional method with water moderator.
7/4/2019 4:57:21 AM +00:00
Development of a computer code for thermalehydraulic design and analysis of helically coiled tube once-through steam generator
The secondary side of the HOTSG is divided into single-phase liquid region, nucleate boiling region, postdryout region, and singlephase vapor region. Different heat transfer correlations and pressure drop correlations are reviewed and applied. To benchmark the developed physical models and the computer code, H-OTSGs developed in Marine Reactor X and System-integrated Modular Advanced ReacTor are simulated by the code, and the results are compared with the design data.
7/4/2019 4:57:06 AM +00:00