TART: Monte Carlo Radiation Transport in Industrial Applications by Dermott E. Cullen University of California Lawrence Livermore National Laboratory L-128/P.O

TART:Monte Carlo Radiation Transport

in Industrial Applications

by

Dermott E. Cullen

University of California

Lawrence Livermore National Laboratory

L-128/P.O. Box 808

Livermore, CA 94550

Tele: 925-423-7359

E.Mail: [email protected]

Website: http://www.llnl.gov/cullen1

This paper will soon be available at my website

What is TART? What’s it’s Pedigree?

•Livermore production code for 40 years•Livermore’s equivalent of MCNP•Only recently released outside Livermore•Now available Internationally

•The currently released version, TART2000, • Coupled Neutron-Photon• 3-D Combinatorial Geometry • Time Dependent• Energy Range: Very Low up to 1 GeV

TART: Monte Carlo Radiation Transport in Industrial Applications

Why should you use TART?

• It is VERY Fast• an order of magnitude or more faster than other codes

• Uses Latest ENDF/B data• neutrons & photons

• It runs on ANY computer• Mainframes• UNIX Workstations• IBM PC – Windows/Linux• Power MAC• My wristwatch (next year)

•The TART System is VERY User friendly•Only about 15-20 % is the Monte Carlo code•The remainder is tools to make your job easier


Why should you use TART? (continued)

•The TART System is a complete system•It helps you prepare and check input•Runs your Monte Carlo calculations•Helps you analyze your results

•Interactive graphics is extensively used•In input preparation and checking•Overlaying results on your geometry•Viewing neutron and photon data

•Interactive graphics is used•Not just to produce pretty pictures•But rather to improve understanding


Example 3-D plotof experimental

setup

Spherical Source

Cylindrical Filter

CylindricalDetector

Example 2-D plotof experimental

results

Source Filter Detector

Note, the reflectionon the Filter

from the detector


•A well known advantage of Monte Carlo is its ability to handle complicated geometry

•TART try to optimize this advantage•Other codes allow first & second degree surfaces

•Planes, spheres, cylinders,…•TART allows third & fourth degree surfaces

•Cubic & quartic splines•Very fine, detailed surfaces

•Torus•There is no limit to the detail of geometry

•Everything is dynamically dimensioned•Here’s an example of a complete seven story building


Example 3-D plot of seven story building(the entire NIF facility)


•TART does source and criticality problems

•What makes TART so fast is experience•40 years of use at Livermore•Hundreds of man-years of use

•Very Responsive to day-to-day User Needs•If you have a need, just ask

•Very versatile Results•Allows 22 different types of tallies•If this doesn’t meet your need tells me; I’ll make it 23



•Many Utility codes to analyze output•If you have a specific need, just ask

•Extensive Verification•Against Measured Results•And Other Codes – MCNP & Sn Codes

•Other codes stress variance reduction•That you must be an expert to use

•TART includes variance reduction, but •I recommend you rely on built-in expert system•to allow non-experts to use it



•Other codes start from basic principles

•In my opinion this approach, ignores,•Everything we were taught in school•Everything we’ve learned since then

•For TART I use every trick of the trade



• For example, TART uses• continuous energy neutrons• and continuous energy kinematics• but multigroup cross sections• 700 groups: 50 per energy decade• Multiband parameters in all group

• Because sampling continuous energy cross sections converges too slowly • and isn’t necessary• we can use self-shielding theory• and the multiband method


U-238 total cross section, 1 to 2.15 keV.Over 3 orders of magnitude variation,

with low probability of resonance

Result: difficult to reproduce averagecross sections and distance to collision

10 samples 1 million samples

Garbage In, Garbage Out!!!

•Any code is only as good as the data it uses• for Neutrons & Photons

•I am amazed at how much effort goes into designing radiation transport codes

•And how little thought seems to be given to the data the codes use

•Your results cannot be better than the data you use •Before deciding to use any code you should know the pedigree of the data it is using


Garbage In, Garbage Out!!! (continued)

•In the case of TART, it always uses the most recent ENDF/B data•Neutrons: ENDF/B-VI, Release 8•Photons: EPDL97 (now ENDF/B-VI)

•Incorporating new data into TART is now completely automated and simple

•I can apply data the same day I receive it


What Monte Carlo codes do I use?

• Experience has shown that no code is perfect• So it is important to verify results

• I use a combination of codes to do this

• During the day I use TART•Because of its speed

• At home, at night, I verify results using•MCNP

• I strongly recommend you also verify results


Why should you use Monte Carlo?

• Only Monte Carlo can accurately Model• Complex Geometry• Exact Reaction Kinematics

• For Example of Kinematics,• Neutron Elastic Scattering• Photon Compton Scattering

• Exact with Monte Carlo – approximate Sn

• If this is important in your applications you should be using Monte Carlo


Can you Afford to Use Monte Carlo?

•Historically it has been too expensive or time consuming to use Monte Carlo•Needed many hours/days•on expensive super computers

•Those days are gone forever

•Recent increases in computer power and decrease in computer costs make Monte Carlo very competitive for use in today’s applications


Can you Afford to Use Monte Carlo? (continued)

•In 1995 the first computer independent version of TART was released

•In 1995 it took the fastest available PC only about three times as long to run a set of test problems, as it took on a CRAY YMP super computer

•These results showed great potential for small computers

•But nobody could foresee what was about to happen



• I gave a similar talk in 1999 – then available PCs ran these same problems 50 times faster than could be done in 1995

•Today’s PCs run these problems 207 times faster than in 1995 [28,487 seconds vs. 89 seconds]

•What took at entire 9 to 5 day (8 hours) in 1995 today takes less than 2.3 minutes •THAT BOGGLES MY MIND!!!



•It wasn’t too long ago that with Monte Carlo we could afford to runs thousands of histories & more recently this became millions (106)

•Using TART a PC today can runs billions (109) histories per day

•Using multiprocessor computers, TART can run trillions (1012) Histories per day

•Statistical convergence is no longer a problem


Conclusions

•Today Monte Carlo is very practical

•Today the major cost of applications is •your salary•NOT computer costs

•I recommend that you use several Monte Carlo codes to verify your results

•Naturally I recommend that one of these codes be TART – see my website for details http://www.llnl.gov/cullen1


Documents

TART: Monte Carlo Radiation Transport in Industrial Applications by Dermott E. Cullen University of California Lawrence Livermore National Laboratory L-128/P.O