The Monte Carlo Codes group (XCP-3) develops and delivers methods, production-quality codes, tools, and training to our sponsors, primarily U.S. federal agencies, through research, development, and maintenance of high-quality software and documentation.

The Monte Carlo method for radiation particle transport has its origins at LANL dating back to the 1940s. The creators of these methods were Drs. Stanislaw Ulam, John von Neumann, Robert Richtmyer, and Nicholas Metropolis. Monte Carlo methods for particle transport have been driving computational developments since the beginning of modern computers (with the first calculations taking place on the ENAIC computer in April–May 1948) and this continues today. More information on the history of the Monte Carlo method and one of XCP-3's products is available in this presentation. While XCP-3 is focused on particle transport, Monte Carlo has become a widely adopted computational technique in areas such as computational biology, computer graphics, applied statistics, finance, and most branches of engineering.

The application areas that use the predictions of XCP-3 codes include (but are not limited to): radiation protection and dosimetry, radiation shielding, radiography, medical physics, nuclear criticality safety, critical and subcritical experiment design and analysis, detector design and analysis, nuclear oil-well logging, accelerator target design, fission and fusion reactor design, decontamination and decommissioning, and nuclear safeguards and nonproliferation. Through contributions to emergency response exercises, our efforts support national security by maintaining the ability to respond successfully to an incident of nuclear terrorism. We provide the nation’s foremost predictive tool for nuclear criticality safety simulations and play a central role in tying nuclear weapon simulations to the nuclear test database.

XCP-3 frequently partners with other organizations inside and outside LANL to provide training and/or consultation and we welcome the opportunity to collaborate to advance the state of the art. However, the three main areas of work in XCP-3 are MCATK (pronounced "mack-a-tack"), the MCNP® (pronounced "em-see-en-pee") code, and supporting tools and capabilities, which are described next.

MCATK

The Monte Carlo Application ToolKit (MCATK) is a C++, component-based, Monte Carlo particle transport code. It provides a library of modular components that can be used for rapid development of custom Monte Carlo applications, for linking to other physics software for multi-physics applications, or for replacing/supplementing functionality in existing Monte Carlo applications. It leverages a unit testing framework and Agile development practices to match other software industry library standards. MCATK can run on large high-performance computing clusters and is parallel reproducible. Components of the MCATK library have been ported to graphics processing units (GPUs), which gives users the flexibility to perform efficient simulations on a new computing architecture. More information on MCATK is available in this journal article.

MCNP

The MCNP, Monte Carlo N-Particle®, code is extensively verified and validated (V&Vd) and can be used for general-purpose transport of many particles including neutrons, photons, electrons, ions, and many other elementary particles, up to 1 TeV/nucleon. The transport of these particles is through a three-dimensional representation of materials defined in a constructive solid geometry, bounded by first-, second-, and fourth-degree user-defined surfaces. In addition, external structured and unstructured meshes can be used to define the problem geometry in a hybrid mode by embedding a mesh within a constructive solid geometry cell, providing an alternate path to defining complex geometry. More information is available on the MCNP website including past user symposia, upcoming training classes, a reference collection with over 1,000 entries, and a list of over 1,500 theses and dissertations that relied on the MCNP code.

Supporting Tools & Capabilities

XCP-3 is responsible for providing enabling capabilities through tools such as the Intrinsic Source Constructor (ISC) library (for determining intrinsically radioactive source terms and material compositions), the MCNPTools library and utilities (for post-processing MCNP calculations), and Whisper (for sensitivity and uncertainty analysis). Other examples of utilities and supporting capabilities are given in the MCNP reference collection and are described in detail within Appendix E of the MCNP6.3 manual. XCP-3 also contributes to related open-source software such as CGMF (for cascading gamma-ray multiplicity and fission modeling) and NJOY2016 (for processing nuclear data).