Neutron Generation Based Method for Monte Carlo Three-Dimensional Reactor Time-Dependent Simulation

2012 ◽  
Author(s):  
Qi Xu ◽  
Ganglin Yu ◽  
Kan Wang
Keyword(s):  
Monte Carlo ◽  
Dynamic Analysis ◽  
Three Dimensional ◽  
Simulation Method ◽  
Time Dependent ◽  
New Method ◽  
Monte Carlo Code ◽  
Neutron Generation ◽  
Direct Simulation ◽  
Reactor Dynamic

A novel Monte Carlo time-dependent simulation method, named neutron generation based method (NGBM), is proposed for three-dimensional reactor dynamic analysis. Different from the traditional direct simulation method (DSM) based on neutron history, the new method, originating from the process of Monte Carlo criticality calculation, is based on neutron generation. In order to turn the original static calculation into a dynamic one, the time mark and time-dependent flux tally are added, the weight of neutron is adjusted while accumulating the flux estimator and the criteria for ending simulation is set. This new method is of higher computing efficiency than the direct simulation method for super-critical time-dependent situation, because it is able to take the advantage of Monte Carlo criticality calculation to keep the number of neutrons per generation approximately constant while the direct simulation method cannot stop the exponential increase of neutron population. The new method was integrated into RMC (Reactor Monte Carlo code developed by Tsinghua University). A numerical experiment was performed. The results demonstrate the feasibility and accuracy of the neutron generation based method for reactor dynamic analysis. The relative deviation of the time-dependent neutron flux tells that the accuracy of the neutron generation based method is enough for routine reactor safety analysis. And the experiment also shows the high efficiency of this method for super-critical reactor systems, since in the experiment, RMC runs nearly 7 times faster than MCNP which uses the direct simulation method.

Scale Effects on Rarefied Supersonic Flows in Nanochannels

2008 ◽  
Author(s):  
Nikolaos A. Gatsonis ◽  
Wael G. Al Kouz ◽  
Ryan E. Chamberlin
Keyword(s):  
Monte Carlo ◽  
Supersonic Flow ◽  
Knudsen Number ◽  
Scale Effects ◽  
Three Dimensional ◽  
Direct Simulation Monte Carlo ◽  
Supersonic Flows ◽  
Direct Simulation ◽  
Aspect Ratios ◽  
Simulation Monte Carlo

The supersonic flow of nitrogen into a nanochannel is investigated using a three dimensional unstructured Direct Simulation Monte Carlo (U3DSMC) method. The U3DSMC code is validated by comparisons with previous 2D DSMC simulations of flows in micron-scale channels. Rectangular nanochannels with heights between 100 nm to 1000 nm, and aspect ratios L/H of 1, 10, 100 are used in the U3DSMC investigation. The Mach 5.9 freestream has a pressure of 0. 1atm and Knudsen numbers of 0.481, 0.962 and 4.81. The nanochannel walls are assumed to be diffusively reflecting at the freestream temperature. The simulations show the development of a disturbance region upstream from the inlet that depends on the Knudsen number. For the L/H = 10 and L/H = 100 nanochannels considered the velocity decreases from its freestream value velocity decreases from its freestream value and becomes subsonic inside the nanochannel. The temperature shows an enhancement region near the inlet while the density shows an enhancement region inside the nanochannel.

scholarly journals Characterization of laser-driven electron and photon beams using the Monte Carlo code FLUKA

2014 ◽  
Vol 32 (2) ◽  
pp. 233-241 ◽  
Author(s):  
F. Fiorini ◽  
D. Neely ◽  
R.J. Clarke ◽  
S. Green
Keyword(s):  
Monte Carlo ◽  
Electron Temperature ◽  
Spectral Characteristics ◽  
Simulation Method ◽  
Target Thickness ◽  
Monte Carlo Code ◽  
X Rays ◽  
Photon Beams ◽  
X Ray ◽  
Plasma Effects

AbstractWe present a new simulation method to predict the maximum possible yield of X-rays produced by electron beams accelerated by petawatt lasers irradiating thick solid targets. The novelty of the method lies in the simulation of the electron refiluxing inside the target implemented with the Monte Carlo code Fluka. The mechanism uses initial theoretical electron spectra, cold targets and refiluxing electrons forced to re-enter the target iteratively. Collective beam plasma effects are not implemented in the simulation. Considering the maximum X-ray yield obtained for a given target thickness and material, the relationship between the irradiated target mass thickness and the initial electron temperature is determined, as well as the effect of the refiluxing on X-ray yield. The presented study helps to understand which electron temperature should be produced in order to generate a particular X-ray beam. Several applications, including medical and security imaging, could benefit from laser generated X-ray beams, so an understanding of the material and the thickness maximizing the yields or producing particular spectral characteristics is necessary. On the other more immediate hand, if this study is experimentally reproduced at the beginning of an experiment in which there is an interest in laser-driven electron and/or photon beams, it can be used to check that the electron temperature is as expected according to the laser parameters.

Monte Carlo Simulation of Inclined Reactivity Control Rod and Boron Poisoning for the Canadian-SCWR Supercell

2016 ◽  
Vol 2 (2) ◽  
Author(s):  
Haykel Raouafi ◽  
Guy Marleau
Keyword(s):  
Monte Carlo ◽  
Three Dimensional ◽  
Coolant Temperature ◽  
Monte Carlo Code ◽  
Control Rod ◽  
Vertical Control ◽  
The Core ◽  
Core Height ◽  
Supercell Model ◽  
Control Rods

The Canadian-SCWR is a heavy-water moderated supercritical light-water-cooled pressure tube reactor. It is fueled with CANada deuterium uranium (CANDU)-type bundles (62 elements) containing a mixture of thorium and plutonium oxides. Because the pressure tubes are vertical, the upper region of the core is occupied by the inlet and outlet headers render it nearly impossible to insert vertical control rods in the core from the top. Insertion of solid control devices from the bottom of the core is possible, but this option was initially rejected because it was judged impractical. The option that is proposed here is to use inclined control rods that are inserted from the side of the reactor and benefit from the gravitational pull exerted on them. The objective of this paper is to evaluate the neutronic performance of the proposed inclined control rods. To achieve this goal, we first develop a three-dimensional (3D) supercell model to simulate an inclined rod located between four vertical fuel cells. Simulations are performed with the SERPENT Monte Carlo code at five axial positions in the reactor to evaluate the effect of coolant temperature and density, which varies substantially with core height, on the reactivity worth of the control rods. The effect of modifying the inclination and spatial position of the control rod inside the supercell is then analyzed. Finally, we evaluate how boron poisoning of the moderator affects their effectiveness.

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