AbstractThis paper presents a hybrid (Monte Carlo/deterministic) method for increasing the efficiency of Monte Carlo calculations distributions, such as flux or dose rate distributions (e.g., mesh tallies), well responses at multiple localized detectors and spectra. This method, referred to Forward-Weighted CADIS (FW-CADIS), is an extension Consistent Adjoint Driven Importance Sampling (CADIS) which has been used more than decade very effectively improve quantities flux, dose, reaction...

This paper provides a review of the hybrid (Monte Carlo/deterministic) radiation transport methods and codes used at Oak Ridge National Laboratory examples their application for increasing efficiency real-world, fixed-source Monte Carlo analyses.The two principal are (1) Consistent Adjoint Driven Importance Sampling (CADIS) optimization localized detector (tally) region (e.g., flux, dose, or reaction rate particular location) (2) Forward Weighted CADIS (FW-CADIS) optimizing distributions...

A generalization of the response expansion previously used to develop a variational heterogeneous coarse mesh transport method has been accomplished. This allows broad class functions be employed within framework original principle. New finite element equations were derived based on general expansion, along with an additional assumption that seemingly breaks tight coupling created numerical difficulties in previous work. In addition, nonvariational was developed new and more thorough manner...

This paper describes code and methods development at the Oak Ridge National Laboratory focused on enabling high-fidelity, large-scale reactor analyses with Monte Carlo (MC).Current state-of-the-art tools used to perform "real" commercial have several undesirable features, most significant of which is non-rigorous spatial decomposition scheme.Monte methods, allow detailed accurate modeling full geometry are considered "gold standard" for radiation transport solutions, playing an...

The immense size and complex geometry of the ITER experimental fusion reactor require development special techniques that can accurately efficiently perform neutronics simulations with minimal human effort. This paper shows effect hybrid Monte Carlo (MC)/deterministic techniques—Consistent Adjoint Driven Importance Sampling (CADIS) Forward-Weighted CADIS (FW-CADIS)—in enhancing efficiency modeling demonstrates applicability coupling these methods computer-aided-design-based MC. Three...

The ITER International Organization has developed a number of reference Monte Carlo N-Particle (MCNP) models including the tokamak machine C-model, Tokamak Complex model, and neutral beam injection (NBI) systems model. model primarily describes building structures beyond bioshield. Representation its are not included in this Oak Ridge National Laboratory Radiation Transport Group conducted two neutronic analysis integrations: (1) integration C-model with for shutdown dose rate...

Fusion energy systems present increasingly significant computational challenges as they grow in size and complexity. Once constructed, ITER will be a full-size nuclear facility with highly complicated structures support systems, an array of scientific equipment close proximity to the neutron-emitting deuterium-tritium plasma. Characterization shutdown dose rate (SDDR) distributions caused by neutron activation these is important final design full-power operation device. This work summarizes...

It is well-known that statistical estimates obtained from Monte Carlo criticality simulations can be adversely affected by cycle-to-cycle correlations in the fission source, which lead to of uncertainties are lower than true uncertainty a factor 5 or more. However, several other more fundamental issues such as adequate source sampling over fissionable regions and convergence have significant impact on for calculated eigenvalue localized tally means, these may mistaken effects resulting...

Neutronics analyses of the ITER experimental fusion reactor rely on increasingly complex geometry models and estimates energy-dependent neutron flux radiation dose-rate distributions generated at ever higher resolutions. There are significant practical challenges with applying Monte Carlo N-Particle (MCNP) continuous-energy transport code to high-resolution analyses. For consisting more than 100 000 surfaces cells, initialization can take several hours, thus slowing down model integration...

AbstractThe well-established Consistent Adjoint Driven Importance Sampling (CADIS) and the Forward Weighted (FW-CADIS) hybrid Monte Carlo/deterministic techniques have dramatically increased efficiency of neutronics simulations, yielding accurate solutions for increasingly complex problems through full-scale, high-fidelity simulations. However, full-scale simulations very large geometrically nuclear energy systems, even CADIS FW-CADIS can reach CPU memory limits all but powerful...

Fusion energy systems pose unique challenges to the modeling and simulation community. These must be met ensure success of ITER experimental fusion reactor. ITER's complex require detailed that goes beyond scale comparable simulations date. In this work, Denovo radiation transport code was used calculate neutron fluence kerma for JET streaming benchmark. This work performed on Titan supercomputer at Oak Ridge Leadership Computing Facility. is a novel three-dimensional discrete ordinates...