Monte Carlo N-Particle Simulations for Nuclear Detection and Safeguards: An Examples-Based Guide for Students and Practitioners

316 Pages·2022·14.679 MB·English

by  John S. Hendricks, Martyn T. Swinhoe, Andrea Favalli

John S. Hendricks
Martyn T. Swinhoe
Andrea Favalli
Monte Carlo
N-Particle
Simulations for
Nuclear Detection
and Safeguards
An Examples-Based Guide
for Students and Practitioners
Monte Carlo N-Particle Simulations for Nuclear
Detection and Safeguards
John S. Hendricks • Martyn T. Swinhoe •
Andrea Favalli
Monte Carlo N-Particle
Simulations for Nuclear
Detection and Safeguards
An Examples-Based Guide for Students
and Practitioners
John S. Hendricks Martyn T. Swinhoe
Los Alamos National Laboratory Los Alamos National Laboratory
Los Alamos, NM, USA Los Alamos, NM, USA
Andrea Favalli
Los Alamos National Laboratory
Los Alamos, NM, USA
This book is an open access publication.
ISBN 978-3-031-04128-0 ISBN 978-3-031-04129-7 (eBook)
https://doi.org/10.1007/978-3-031-04129-7
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Preface
This book is intended as a tool for Monte Carlo N-Particle (MCNP®) software prac-
titioners who use the code to simulate the interaction of radiation with matter in
general and safeguards-related detector instrumentation in particular. Most MCNP
software-related references are directed toward users who are modeling for other
applications. Nuclear safeguards applications require a distinctly different approach
to MCNP modeling. This book contains a fundamentals review, followed by exam-
ples written by safeguards modeling experts. It also includes an overview of
advanced concepts like variance reduction. We hope that this guide will help new
modelers learn to use the MCNP software for safeguards applications and save time
and effort for the veteran safeguards modeler in working through the MCNP manual
to solve problems that have already been solved.
This book does not introduce or explain safeguards concepts or techniques. The
user is expected to be familiar with the type of instrumentation (both neutron and
gamma) that is currently applied. For background information on nondestructive
assay methods for safeguards, we refer the reader to other publications such as the
“PANDA” manual1 or the book on radiation detection by Knoll.2
This book is not intended to replace the MCNP software manual.3 We will refer
to the MCNP User’s Manual Code Version 6.2 extensively. The examples in this
book were run using MCNP version 6.2 software, but the general principles
described have been applicable for many previous versions of the code and are
1 “Passive Nondestructive Assay of Nuclear Materials” https://www.lanl.gov/org/ddste/aldgs/sst-
training/technical-references.php
2 G. F. Knoll “Radiation Detection and Measurement” John Wiley 2000.
3 C. J. Werner, Ed., “MCNP User’s Manual Code Version 6.2,” LA-UR-17-29981 (October
27, 2017).
v
vi Preface
expected to be valid also in future versions. For general information on the code, its
history and availability, as well as latest information and news, please see https://
mcnp.lanl.gov/.
Los Alamos, NM, USA J. S. Hendricks
Los Alamos, NM, USA M. T. Swinhoe
Los Alamos, NM, USA A. Favalli
November 2021
Acknowledgments
The authors acknowledge the Office of International Nuclear Safeguards–Human
Capital Development Subprogram for the support and the Los Alamos National
Laboratory (LANL) Research Library for the support in publishing the book as an
open-access book.
An important contribution to the quality of the manuscript was made by mem-
bers of the XCP-3 group at Los Alamos National Laboratory, who reviewed the
manuscript and made many constructive suggestions. Nevertheless, any errors and
omissions remain the responsibility of the authors.
The authors would also like to thank Tamara Hawman, LANL Communications
and External Affairs-Communication Arts and Services, for editorial and formatting
support.
vii
About This Book
The MCNP® software is a general-purpose Monte Carlo N-Particle code that can be
used for transport simulations of neutrons, photons, electrons, ions, etc. In the field
of nuclear safeguards and nonproliferation, MCNP software simulations are rou-
tinely used for many purposes such as the design and calibration of detector systems
and the study of nuclear safeguards scenarios, including radiation emission proper-
ties of fresh fuel in shipping containers and spent fuel in storage pools. Current lit-
erature lacks a reference book or repository material that systematically explains
MCNP software usage by example; thus, the purpose of this work is to augment
current literature with a reference repository that teaches MCNP software usage
through detailed examples, with a focus on nuclear safeguards applications. We
explain both MCNP software input and output files and the technical details used in
MCNP input file preparation, which are linked to the MCNP manual. Examples
have been selected based on the real-world experience of the safeguards group at
Los Alamos National Laboratory (LANL) and the feedback of students trained in
MCNP software by LANL safeguards personnel.
We expect this text to be of great benefit to students, postdocs, and practitioners
who work in the nuclear engineering and nuclear physics fields with an emphasis on
the use of MCNP software in nuclear safeguards and nonproliferation. It is a means
to transfer the knowledge that the authors have developed through decades of work
with the MCNP software—in real safeguards scenarios—to a new generation of
subject matter experts.
Supplementary files Each chapter comes with downloadable input files for the

user to easily reproduce the examples in the text. The files corresponding to each
chapter can be located via a link in the footnote on the first page of that chapter.
Trademarks MCNP® is a registered trademark owned by Triad National Security,

LLC, manager and operator of Los Alamos National Laboratory. Any questions
regarding licensing, proper use, and/or proper attribution of Triad National Security,
LLC, marks should be directed to [email protected].
Copyright ©2021, J. Hendricks, M. T. Swinhoe, and A. Favalli

ix
x About This Book
Disclaimer Los Alamos National Laboratory strongly supports academic freedom

and a researcher’s right to publish; however, as an institution, the Laboratory does
not endorse the viewpoint of a publication or guarantee its technical correctness.
The submitted manuscript has been authored by an employee or employees of
Triad National Security, LLC, operator of Los Alamos National Laboratory under
Contract No. 89233218CNA000001 with the U.S.  Department of Energy.
Accordingly, the U.S. Government retains an irrevocable, nonexclusive, royalty-
free license to publish, translate, reproduce, use, or dispose of the published form of
the work and to authorize others to do the same for U.S. Government purposes.
Contents
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1 Nuclear Safeguards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 Monte Carlo N-Particle Transport: MCNP Code . . . . . . . . . . . . . . . 2
1.3 Objective . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2 Basic Concepts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.1 Geometry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.1.1 Simplest Possible Input File . . . . . . . . . . . . . . . . . . . . . . . . 5
2.1.2 Running MCNP: The Simplest Case . . . . . . . . . . . . . . . . . . 6
2.1.3 Simple Input File . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.1.4 Running and Plotting MCNP Geometries . . . . . . . . . . . . . . 11
2.1.5 Surfaces and Complicated Cells: Intersections and
Unions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
2.1.6 Duplicate Cells, Complements, and Translations:
LIKE n BUT and TRCL. . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
2.1.7 Filled Cells: Universes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
2.1.8 Lattice Geometries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
2.1.9 Fully Specified Lattice Geometries . . . . . . . . . . . . . . . . . . . 28
2.2 Materials and Cross Sections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
2.2.1 Specifying Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
2.2.2 Neutron Cross Sections . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
2.2.3 Low-Energy Neutron Problems: Thermal Free Gas
Treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
2.2.4 Low-Energy Neutron Problem Data: S(α,β) Thermal
Treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
2.2.5 Photon Cross Sections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
2.2.6 Electron-Stopping Powers for Coupled Photon and Electron
Problems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
2.2.7 Data and Models for Ions and Charged Particles . . . . . . . . . 48
2.2.8 Additional Data Diagnostics and Recommendations . . . . . 50
xi