Application of local Monte Carlo method in neutronics calculation of EAST radial neutron camera

2021 ◽  
Author(s):  
Liangsheng Huang ◽  
Liqun Hu ◽  
Luying NIU ◽  
Mengjie Zhou ◽  
Bing Hong ◽  
...  
Keyword(s):  
Monte Carlo ◽  
Variance Reduction ◽  
Geometric Model ◽  
Diagnostic System ◽  
Source Model ◽  
Deep Penetration ◽  
Diagnostic Systems ◽  
Surface Source ◽  
Nuclear Shielding ◽  
Long Time

Abstract The Local Monte Carlo (LMC) method is used to solve the problems of deep penetration and long time in the neutronics calculation of the Radial Neutron Camera (RNC) diagnostic system on the Experimental Advanced Superconducting Tokamak (EAST), and the radiation distribution of the RNC and the neutron flux at the detector positions of each channel are obtained. Compared with the results calculated by the Global Variance Reduction (GVR) method, it is shown that the LMC calculation is reliable within the reasonable error range. The calculation process of LMC is analyzed in detail, and the transport process of radiation particles is simulated in two steps. In the first step, an integrated neutronics model considering the complex window environment and a neutron source model based on EAST plasma shape are used to support the calculation. The particle information on the equivalent surface is analyzed to evaluate the rationality of settings of equivalent surface source and boundary. Based on the characteristic that only a local geometric model is needed in the second step, it is shown that the LMC is an advantageous calculation method for the nuclear shielding design of tokamak diagnostic systems.

scholarly journals PERFORMANCE STUDY OF GLOBAL WEIGHT WINDOW GENERATOR BASED ON PARTICLE DENSITY UNIFORMITY

2021 ◽  
Vol 247 ◽  
pp. 18005
Author(s):  
Peng He ◽  
Bin Wu ◽  
Lijuan Hao ◽  
Guangyao Sun ◽  
Bin Li ◽  
...  
Keyword(s):  
Monte Carlo ◽  
Variance Reduction ◽  
Particle Density ◽  
Complex Model ◽  
Deep Penetration ◽  
Detailed Calculation ◽  
Performance Study ◽  
Global Weight ◽  
Weight Window ◽  
Calculation Results

The variance reduction techniques are necessary for Monte Carlo calculations in which obtaining a detailed calculation result for a large and complex model is required. The GVR method named as global weight window generator (GWWG) was proposed by the FDS team. In this paper, two typical calculation examples, ISPRA-Fe benchmark in SINBAD (Shielding Integral Benchmark Archive Database) and TF Coils (Toroidal Field coils) of European HCPB DEMO (Helium Cooled Pebble Bed demonstration fusion plant), are used to study the performance of GWWG method. It can be seen from the calculation results that the GWWG method has a significant effect in accelerating the Monte Carlo calculation. Especially when the global convergence calculation results are needed, the acceleration effect (FOMG) can reach 105 or more. It proves that the GWWG method is an effective tool for deep-penetration simulations using Monte Carlo method.

scholarly journals Simulating neutron transport in long beamlines at a spallation neutron source using Geant4

2020 ◽  
Vol 22 (2-3) ◽  
pp. 183-189
Author(s):  
Douglas D. DiJulio ◽  
Isak Svensson ◽  
Xiao Xiao Cai ◽  
Joakim Cederkall ◽  
Phillip M. Bentley
Keyword(s):  
Monte Carlo ◽  
Neutron Source ◽  
Variance Reduction ◽  
Neutron Transport ◽  
High Energy ◽  
Low Energy ◽  
Deep Penetration ◽  
Monte Carlo Code ◽  
Spallation Neutron Source ◽  
Unique Challenge

The transport of neutrons in long beamlines at spallation neutron sources presents a unique challenge for Monte-Carlo transport calculations. This is due to the need to accurately model the deep-penetration of high-energy neutrons through meters of thick dense shields close to the source and at the same time to model the transport of low- energy neutrons across distances up to around 150 m in length. Typically, such types of calculations may be carried out with MCNP-based codes or alternatively PHITS. However, in recent years there has been an increased interest in the suitability of Geant4 for such types of calculations. Therefore, we have implemented supermirror physics, a neutron chopper module and the duct-source variance reduction technique for low- energy neutron transport from the PHITS Monte-Carlo code into Geant4. In the current work, we present a series of benchmarks of these extensions with the PHITS software, which demonstrates the suitability of Geant4 for simulating long neutron beamlines at a spallation neutron source, such as the European Spallation Source, currently under construction in Lund, Sweden.

scholarly journals Monte Carlo Simulation and Experimental Validation for Radiation Protection with Multiple Complex Source Terms and Deep Penetration for a Radioactive Liquid Waste Cementation Facility

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Wenqian Li ◽  
Xuegang Liu ◽  
Sheng Fang ◽  
Xueliang Fu ◽  
Kaiqiang Guo
Keyword(s):  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Radiation Protection ◽  
Experimental Measurement ◽  
Variance Reduction ◽  
Liquid Waste ◽  
Deep Penetration ◽  
Radioactive Liquid Waste ◽  
Variance Reduction Techniques ◽  
Reduction Techniques

A new radioactive liquid waste cementation facility was under commissioning recently in the Institute of Nuclear and New Energy Technology of Tsinghua University, which is designed to simultaneously process multiple intermediate-level radioactive waste drums. Therefore, the multiple volume sources and the scattering effect becomes a key issue in its radiation protection. For this purpose, the Monte Carlo program FLUKA code and experimental measurement were both adopted. In the FLUKA simulation, five different scenarios were considered, i.e., one drum, two drums, four drums, six drums, and eight drums. For the multiple volume sources, the source subroutine code of FLUKA was rewritten to realize the sampling. The complex shielding also leads to a deep penetration problem; hence, the optimization algorithm and variance reduction techniques were adopted. During the measurement, two scenarios, outdoor and indoor, were carried out separately representing the dose field when only one drum is considered and when the scattering effect is considered. A comparison between the experiments and calculations shows very good agreement. From both of the Monte Carlo simulation and the experimental measurement, it can be drawn that, in the horizontal direction, with the increase of the drum number, the dose rate increases very little, while in the vertical direction, the increase of the dose rate is very obvious with the increase of the drum number. The complicated source term sampling methods, the optimization algorithm and variance reduction techniques, and the experimental verification can provide valuable references for the similar scattering problem in radiation protection and shielding design.

Application of a 3D Discrete Ordinates-Monte Carlo Coupling Method on CAP1400 Cavity Streaming Calculation

2017 ◽  
Author(s):  
Zheng Zheng ◽  
Hui Li ◽  
Mengqi Wang
Keyword(s):  
Monte Carlo ◽  
Reactor Core ◽  
Coupling Method ◽  
Normal Operation ◽  
Discrete Ordinates ◽  
Deep Penetration ◽  
Monte Carlo Code ◽  
Surface Source ◽  
Dose Rates ◽  
Mc Method

Neutrons and photons produced from reactor core during operation pass through the pressure vessel, reach the reactor cavity, and form the reactor cavity streaming. Reactor cavity streaming dose rates calculation during normal operation is important for the evaluation and control of the equipment dose rates in the nuclear power plant. Because reactor is great in dimension and complex in geometry, neutrons and photons fluence rates declined by several orders from reactor core to outside. Cavity streaming calculation is a deep penetration calculation with heavy computation load which is difficult to converge. Three dimensional Discrete Ordinates and Monte Carlo (SN-MC) coupling method combines the advantage of the SN method with high efficiency and the MC method with fine geometrical modeling. The SN-MC coupling method decreases the tally errors and increases the efficiency of the MC method effectively by using MC surface source generated by the SN fluence rates. In this paper, the theoretical model of the 3D SN-MC coupling method is presented. In order to fulfill the coupling calculation, a 3D Discrete Ordinates code is modified to output angular fluence rates, a link code DO2MC is developed to calculate cummulative distribution functions of source particle variables on surface source, and a source subroutine is written for a 3D Monte Carlo code. The 3D SN-MC coupling method is applied on the calculation of the CAP1400 cavity streaming neutron and photon dose rates. Numerical results show that the 3D SN-MC coupling codes are correct, the relative errors of the results are less than 20% compared with those of the MC bootstrapping method, and the efficiency is greatly enhanced.

Long-Time Trajectorial Large Deviations and Importance Sampling for Affine Stochastic Volatility Models

2021 ◽  
Vol 53 (1) ◽  
pp. 220-250
Author(s):  
Zorana Grbac ◽  
David Krief ◽  
Peter Tankov
Keyword(s):  
Monte Carlo ◽  
Stochastic Volatility ◽  
Variance Reduction ◽  
Large Deviation ◽  
Heston Model ◽  
Stochastic Volatility Models ◽  
Monte Carlo Computation ◽  
Volatility Models ◽  
Long Time ◽  
Path Dependent

AbstractWe establish a pathwise large deviation principle for affine stochastic volatility models introduced by Keller-Ressel (2011), and present an application to variance reduction for Monte Carlo computation of prices of path-dependent options in these models, extending the method developed by Genin and Tankov (2020) for exponential Lévy models. To this end, we apply an exponentially affine change of measure and use Varadhan’s lemma, in the fashion of Guasoni and Robertson (2008) and Robertson (2010), to approximate the problem of finding the measure that minimizes the variance of the Monte Carlo estimator. We test the method on the Heston model with and without jumps to demonstrate its numerical efficiency.

Verification of Shielding Calculation Capability of RMC With H.B.Robinson-2 Pressure Vessel Benchmark

2018 ◽  
Author(s):  
Junjie Rao ◽  
Xiaotong Shang ◽  
Kan Wang
Keyword(s):  
Monte Carlo ◽  
Neutron Flux ◽  
Pressure Vessel ◽  
Variance Reduction ◽  
Fission Neutron ◽  
Deep Penetration ◽  
Monte Carlo Code ◽  
Calculation Methods ◽  
Neutron Distribution ◽  
Window Method

RMC is a 3-D continuous energy Monte Carlo code developed by REAL team in Tsinghua University, China. Besides the capability of fuel cycle burnup calculation, hybrid MPI/OpenMP parallelism strategy, sensitivity and uncertainty analysis, N-TH coupling calculation, shielding calculation methods including general source description, regional importance method, weight window method and source biasing method have been also developed for deep penetration problems. H.B.Robinson-2 Pressure Vessel Benchmark (HBR-2 benchmark) is used for the qualification of pressure vessel neutron flux calculation methods and shielding calculations based on this model have been performed by Monte Carlo codes such as SCALE, MCNPX and deterministic transport code DORT. In this work, the verification calculation of shielding calculation capability of RMC is conducted based on HBR-2 benchmark. The total calculation consists of two stages. Criticality calculation is performed first to obtain the fission neutron distribution in the reactor core assemblies. Then the fission neutron distribution is regarded as the initial neutron source in the following fixed source calculation. Variance reduction techniques such as source biasing and regional importance methods are combined together to be able to reduce the variance of the neutron flux in regions within and outside the pressure vessel including the downcomer and cavity regions. The preliminary calculation results show good agreement with MCNP and the shielding calculation of RMC is justified and applicable for deep penetration problems.

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