LA-UR- o:J~6)~~ Approved for public release; distribution is unlimited.

Title: MCNPX Graphics and Arithmetic Tally Upgrades

Author(s): Joe W. Durkee, Jr., Michael R. James, and Laurie S. Waters

Intended for: American Nuclear Society 2009 International Conference on Advances in Mathematics, Computational Methods, and Reactor Physics, May 3-7,2009

fo~A'amosNATIONAL LABORATORY ---- EST. 1943 ---­

Los Alamos National Laboratory, an affirmative action/equal opportunity employer, is operated by the Los Alamos National Security, LLC for the National Nuclear Security Administration of the U.S. Department of Energy under contract DE-ACS2-06NA25396. By acceptance of thiS article, the publisher recognizes that the U.S. Government retains a nonexclusive, royalty-free license to publish or reproduce the published form of this contribution, or to allow others to do so, for U.S. Government purposes. Los Alamos National Laboratory requests that the publisher identify this article as work performed under the auspices of the U.S. Department of Energy. Los Alamos National Laboratory strongly supports academic freedom and a researcher's right to publish; as an institution, however, the Laboratory does not endorse the viewpoint of a publication or guarantee its technical correctness.

Form 836 (7/06)

Math&Comp2009 LA-UR -08-xxxx

MCNPX GRAPIDCS AND ARITHMETIC TALLY UPGRADES

Joe W. Durkee, Jr., Michael R. James, and Laurie S. Waters Los Alamos National Laboratory

Corresponding Author: Joe W. Durkee, Jr. jdurkee@lanl.gov

505-665-0530 Fax: 505-665-2897

PO Box 1663, MS K575 Los Alamos, NM 87545

Total number of pages: 9.

Total number of tables: O.

Total number of figures: 4.

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ABSTRACT

The MCNPX MCPLOT package is the tool used to plot tallies and cross-sections. We

report on an assortment of upgrades to MCPLOT that are intended to improve the

appearance of two-dimensional tally and cross-section plots. We have also expanded the

content and versatility of the MCPLOT "help" command. Finally, we describe the initial

phase of capability implementation to post-process tally data using arithmetic operations.

These improvements will enable users to better display and manipulate simulation results.

INTRODUCTION

Los Alamos National Laboratory (LANL) develops and maintains the MCNPX™1 Monte

Carlo N-Particle eXtended general-purpose radiation transport code. MCNPX

accommodates intricate three-dimensional geometrical models, continuous-energy

transport of 34 different particle types plus heavy-ion transport,2 fuel bumup,3 and high­

fidelity delayed-gamma emission.4 MCNPX is written in Fortran 90, has been

parallelized, and works on platforms including single-processor personal computers

(PCs), Sun workstations, Linux clusters, and supercomputers. MCNPX has

approximately 2000 users throughout the world working on endeavors that include

radiation therapy, reactor design, and homeland security.

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Visualization of model geometry and of calculated results ("tallies") is an important

component of the simulation process, particularly when complex models involving multi­

particle transport are being analyzed. MCNPX contains the interactive "PLOT" package

to plot model geometry. Since its creation three decades ago, the "MCPLOT" package

has been used to make two-dimensional (2-D) plots of tally information (Le., calculated

fluxes, currents, etc.) and of nuclear cross-section data. We have made a many upgrades

to improve overall plot appearance. In addition, we have added content from the

MCNPX manual to MCPLOT's "help" command so as to alleviate the need to refer to

the manual.

At times, the ability to post-process tallies using arithmetic operations is desired by

analysts. For example, a user might wish to study the difference between tallies for a pair

of simulations that were conducted using models that differed only in source particle

type. Until now this study could not be done using MCNPX. We report here on a new

capability that is being developed to enable the post-processing of tallies using arithmetic

operations.

MCPLOT 2-D-PLOT GRAPmCS UPGRADES

Figures 1 and 2 contain pre- and post-upgrade plots of the same tally data. The MCPLOT

graphics improvements include (1) ordinate numbering that is reasonably dense, (2)

differentiated major and minor tick lengths on log axes, (3) use of "e" format for

exponents, (4) horizontal display of ordinate numbers (to decrease crowding), (5) the use

of upper-case fonts for labels where appropriate, (6) maximum legend curve-identifier

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length increased from to ten to 23 characters, (7) maximum title length increased from 40

to 70 characters, (8) maximum number of log-axes decades increased from 17 to 200,

and (9) improved clarity in legend block.

Pulsed Neutron Source In U-235

Only 40-Character Titles Allowed

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Figure 1. Legacy MCPLOT 2-D tally plot. PDF image.

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4

__

Math&Comp2009 LA-UR-08-xxxx

Pulsed Pie.ion-Spectrum Neutron Source In U-135

70-Character Title. Can Be U.ed With The New 2-D Plotting Capability

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h-ll ie-a 1.-5 1.-2

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Figure 2. Improved MCPLOT 2-D tally plot. PDF image.

MCPLOT "HELP" COMMAND UPGRADES

The legacy MCNPX MCPLOT "help" command capability was exceedingly limited-it

only provided a three-column un-alphabetized list of commands. The "help" command

has been improved in two ways. First, the basic "help" command now produces an

alphabetized command listing. Second, syntax and content is now provided for individual

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commands. Figure 3 illustrates the revamped "help" command output for the "coplot"

command.

mcplot> help coplot

coplot > Syntax: coplot Plot multiple curves on one plot. COPLOT is effective for 2-D plots only. If COPLOT is the last command on a line, it functions as if it were followed by an &.

mcplot>

Figure 3. New MCPLOT "help" command capability illustrating content for the

"coplot" command, including invocation syntax and purpose.

POST -PROCESSING ARITHMETIC OPERATIONS FOR TALLIES

Previous versions of MCNPX did not allow post-processing of tally data using arithmetic

operations. We have begun development of post -processing capability to enable addition,

subtraction, multiplication, and division operations for tally data produced by one or

more MCNPX calculations.

To illustrate, the following command sequence calculates and plots the difference

between the surface-integrated currents for simulations involving point sources of 20­

Me V photons and neutrons positioned at the center of a 100-cm radius sphere of water.

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rmctal=pcpp4m +- Read photon tally metal file tal 0 = tall +-Create a saved arithmetic tally (photons) rmctal=pcpp6m +- Read neutron tally metal file tal 10 = tall +-Create another saved arithmetic tally (neutrons) tal 20 = tal 10 - tal 0 +-Save the difference tal 0 label "tal 0: 20-MeV photons" cop tal 10 label "tal 10: 20-MeV neutrons" cop tal 20 label "dif=photons-neutrons" +-Plot the tallies

Figure 4 contains the tallies for the respective calculations as well as their difference .

0.1

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C'_'~:. ,_.. ,_, ,____ .... . " _~ ,_.. ' _.._.. ,._ ,___ ,__ ... , __ _., _ '., ___ ._, _._..__ ,___ . __.. , ______ ._.. '_:._ .... __ :'_

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Figure 4. New MCPLOT arithmetic-tally capability. tal 0 and tal 10 are the saved

arithmetic tallies for the photon and neutron sources, respectively, while "dif' is their

difference.

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CONCLUSIONS

The MCNPX MCPLOT graphics package has been upgraded to provide enhanced quality

for 2-D tally and cross-section plots. Contour plots can now be created using logarithmic

axes. The MCPLOT "help" command has been extended to (1) provide an alphabetized

list of commands and (2) include syntax and content for each MCPLOT command.

A new MCNPX feature is being developed that provides the capability to post-process

tally data using arithmetic operations ("arithmetic tallies"). The initial upgrades include

addition, subtraction, multiplication, and division operations on tally data generated for

one or more MCNPX calculations. The user has the choice of creating and plotting

arithmetic tallies with or without saving them for further use.

These upgrades appear in the 2.7.x versions of MCNPX.

REFERENCES

1. Pelowitz D. B., ed., "MCNPX User's Manual Version 2.6.0," Los Alamos National

Laboratory report LA-CP-07-1473 (April 2008).

2. James, M.R.; McKinney, G.W.; Hendricks, J.S.; Moyers, M., "Recent Enhancements

in MCNPX: Heavy-Ion Transport and the LAQGSM Physics Model," Nuclear

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Instruments & Methods in Physics Research, Section A (Accelerators, Spectrometers,

Detectors and Associated Equipment); 23 June 2006; vo1.562, no.2, p.819-22.

3. Fensin M. L., Hendricks J. S., and Anghaie S., "Enhanced Monte-Carlo-Linked

Depletion Capabilities in MCNPX," Los Alamos report: LA-UR-06-0363, 2006

International Congress on Advances in Nuclear Power Plants Embedded Topical

Meeting at the 2006 ANS Annual Meeting, ICAP '06, Reno, NV (June 4-8,2006).

4. Durkee, J.W. Jr., McKinney G.W., Trellue H. R., Waters L.S., and Wilson W.B.,

"Delayed-Gamma Signature Calculation for Neutron-Induced Fission Using

MCNPX," accepted for publication in Progress in Nuclear Energy, pp. 1-86 (2008).

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