Russell C. Johns

Initial MCNP6 Release Overview

MCNP6 is simply and accurately described as the merger of MCNP5 and MCNPX capabilities, but it is much more than the sum of those two computer codes. MCNP6 is the result of five years of effort by the MCNP5 and MCNPX code development teams. These groups of people, residing in Los Alamos National Laboratory’s (LANL) X Computational Physics Division, Monte Carlo Codes Group (XCP-3), and Decision Applications Division, Radiation Transport and Applications Team (D-5), respectively, have combined their code development efforts to produce the next evolution of MCNP. While maintenance and bug fixes will continue for MCNP5 1.60 and MCNPX 2.7.0 for upcoming years, new code development capabilities only will be developed and released in MCNP6. In fact, the initial release of MCNP6 contains 16 new features not previously found in either code. These new features include the abilities to import unstructured mesh geometries from the finite element code Abaqus, to transport photons down to 1.0 eV, to transport electrons down to 10.0 eV, to model complete atomic relaxation emissions, and to generate or read mesh geometries for use with the LANL discrete ordinates code Partisn. The first release of MCNP6, MCNP6 Beta 2, is now available through the Radiation Safety Information Computational Center, and the first production release is expected in calendar year 2012. High confidence in the MCNP6 code is based on its performance with the verification and validation test suites, comparisons to its predecessor codes, the regression test suite, its code development process, and the underlying high-quality nuclear and atomic databases.

The MCNPX Monte Carlo Radiation Transport Code

MCNPX (Monte Carlo N‐Particle eXtended) is a general‐purpose Monte Carlo radiation transport code with three‐dimensional geometry and continuous‐energy transport of 34 particles and light ions. It contains flexible source and tally options, interactive graphics, and support for both sequential and multi‐processing computer platforms. MCNPX is based on MCNP4c and has been upgraded to most MCNP5 capabilities. MCNP is a highly stable code tracking neutrons, photons and electrons, and using evaluated nuclear data libraries for low‐energy interaction probabilities. MCNPX has extended this base to a comprehensive set of particles and light ions, with heavy ion transport in development. Models have been included to calculate interaction probabilities when libraries are not available. Recent additions focus on the time evolution of residual nuclei decay, allowing calculation of transmutation and delayed particle emission. MCNPX is now a code of great dynamic range, and the excellent neutronics capabilities allow new opportunities to simulate devices of interest to experimental particle physics, particularly calorimetry. This paper describes the capabilities of the current MCNPX version 2.6.C, and also discusses ongoing code development.

Designing SWORD--SoftWare for Optimization of Radiation Detectors

The software for the optimization of radiation detectors (SWORD) is an integrated system (based on MCNPX [Pelowitz, DB, 2005] and GEANT4 [Agostinelli, S, et al., 2003] 3D Monte Carlo radiation transport codes) useful for the optimization of high energy radiation detection systems. A set of usable sample inputs and analysis algorithms are integrated into the system. Sample inputs include special nuclear material (SNM) targets, nuisance sources, and industrial and marine backgrounds. Analysis algorithms include spectroscopy and imaging for coded aperture detectors and Compton imagers. The system is designed from the start to be easy to use and to be deployable to detector design and system architecture study groups who are its ultimate users.

Interacting with the SWORD package (SoftWare for the Optimization of Radiation Detectors)

We present the first version of software for the optimization of radiation detectors (SWORD): a software package designed to simplify the evaluation of different gamma-ray detector configurations or the process of conducting system architecture studies for Homeland Security and other applications. It is a fully integrated system that uses GEANT4 [2] and MCNPX [3] to conduct Monte Carlo simulations, and can analyze the resulting output in a single step. We discuss in detail the following: the SWORD 3-D graphical tool for interactively creating custom detector and environment designs; the integration of the MCNPX interface, where users can provide an MCNPX input deck and directly push it into the system; and finally the serialization of data into a binary format in order to better manage the large amount of data produced in Monte Carlo simulation.

MCNPX Improvements for Threat Reduction Applications

Enhancements contained in the current MCNPX 2.6.0 Radiation Safety Information Computational Center (RSICC) release will be presented, including stopped‐muon physics, delayed neutron and photon generation, and automatic generation of source photons. Preliminary benchmarking comparisons with data taken with a muon beam at the Paul Scherrer Institute Spallation Neutron Source accelerator will be discussed. We will also describe current improvements now underway, including Nuclear Resonance Fluorescence (NRF), pulsed sources, and others. We will also describe very new work begun on a threat‐reduction (TR) user interface, designed to simplify the setup of TR‐related calculations, and introduce standards into geometry, sources and backgrounds.