Form 836 (7/06)
LA-UR- Approved for public release; distribution is unlimited.
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-AC52-06NA25396. 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.
Title:
Author(s):
Intended for:
Operated by the Los Alamos National Security, LLC for the DOE/NNSA
Recent Developments in MCNP and MCNPX
H. Grady HughesLos Alamos National Laboratory
Uncertainty Assessment in Computational DosimetryBologna, Italy
October 8 –10, 2007
Operated by the Los Alamos National Security, LLC for the DOE/NNSA
Abstract
New features of MCNP and MCNPX will be discussed with particular attention to the forthcoming release of MCNP5 and to the ongoing MCNP/MCNPX unification project. One particular new feature for electron transport, the detailed straggling sampling (first made available in version 1.40 of MCNP5) will be described, and its effect on the calculation of pulse-height spectra in a mini-TEPC simulation will be reported.
Operated by the Los Alamos National Security, LLC for the DOE/NNSA
New Features in MCNP5 version 1.40
• Stochastic geometry
• Source entropy estimation and plotting (for criticality)
• Fission neutron multiplicity
• New electron energy-loss straggling logic
• Positron sources
• Lethargy plots for energy-dependent tallies
• Mesh tally plotter
• Input conveniences
Operated by the Los Alamos National Security, LLC for the DOE/NNSA
Stochastic Geometry
• On-the-fly random translations of embedded universes in lattice
• Developed for pebble bed reactors.
• Could model other amorphous materials
• Medical physics – Alveoli, sinuses, bone
marrow, … ?
Fuel kernel displaced randomly within lattice element each time that particle enters
Image of the stochasticgeometry of fuel kernels from MCNP5 plotter
Forrest Brown, “Monte Carlo Methods & MCNP Code Development” Monte Carlo 2005, Chattanooga, TN.
Operated by the Los Alamos National Security, LLC for the DOE/NNSA
Operated by the Los Alamos National Security, LLC for the DOE/NNSA
New Landau Straggling Logic
• Bin-centered (MCNP) logic– One sample per energy step– Emphasis is on remaining (mostly) within the energy group– DBCN 17J 0 (still the default)
• Nearest-group boundary (ITS) logic– One sample per energy step– Emphasis is on completing a prescribed energy step– DBCN 17J 1 (often preferred)
• Detailed straggling logic– One sample per angular sub-step– Sampling function is specific to particle energy and step length– DBCN 17J 2 (new with MCNP5 1.40)
Operated by the Los Alamos National Security, LLC for the DOE/NNSA
Landau Straggling Example
• Three representations of the same geometry
– 10 MeV electrons
– 15 mm water slab
– No angular deflection
– Substep = 1.364 mm
Operated by the Los Alamos National Security, LLC for the DOE/NNSA
3 4 5 6 7 8Transmitted Electron Energy (MeV)
1×10-3
1×10-2
1×10-1
1×100
1×101
Num
ber
per
MeV
per
Sou
rce
Ele
ctro
n 15 mm cell1 mm cells0.1 mm cells
MCNP (bin-centered) Straggling Logic10 MeV electrons after 15 mm water, no angular deflection
Operated by the Los Alamos National Security, LLC for the DOE/NNSA
3 4 5 6 7 8Transmitted Electron Energy (MeV)
1×10-3
1×10-2
1×10-1
1×100
1×101
Num
ber
per
MeV
per
Sou
rce
Ele
ctro
n 15 mm cell1 mm cells0.1 mm cells
ITS (nearest-group-boundary) Straggling Logic10 MeV electrons after 15 mm water, no angular deflection
Operated by the Los Alamos National Security, LLC for the DOE/NNSA
3 4 5 6 7 8Transmitted Electron Energy (MeV)
1×10-3
1×10-2
1×10-1
1×100
1×101
Num
ber
per
MeV
per
Sou
rce
Ele
ctro
n 15 mm cell1 mm cells0.1 mm cells
Step-Specific Straggling Logic10 MeV electrons after 15 mm water, no angular deflection
Operated by the Los Alamos National Security, LLC for the DOE/NNSA
New Features in MCNP5 version 1.50
• Pulse-height tally variance reduction– Including DXTRAN– Memory management for threading
• Generation of temperature-specific cross sections– Enhancement to MAKXSF code– Doppler broaden resolved resonance data to higher temperature– Interpolate unresolved resonance data and S( , ) data
• Lattice memory improvements
• Improved annihilation gamma treatment
• Long file names (256 characters)
Operated by the Los Alamos National Security, LLC for the DOE/NNSA
Lattice Memory Improvements
• Increase limit on number of voxels from ~20 Million to ~200+ Million.
• Reduce startup times from hours or days to a few hours.
• Windows OS limit of 2 Gigabytes of Memory per program. (Use 64 bit chip & OS)
0
100
200
300
400
500
600
700
800
900
0 50 100 150 200 250 300 350 400
Millions of Voxel Cells
Meg
abyt
es o
f Mem
ory MCNP5_RSICC_1.20
MCNP5 VIP Modifications
Goorley, “Issues Related to the use of MCNP code for an
Extremely Large Voxel Model VIP-MAN” Monte Carlo 2005.
Operated by the Los Alamos National Security, LLC for the DOE/NNSA
Selected Recent MCNPX Features
• Version 2.6.A– Transmutation using CINDER90– Proton step size control– New S( , ) scattering law– STOP card– Long file names (40 characters)
• Version 2.6.B– CEM INC model upgrade (2K 03)– Gravitational effects for neutrons– Improved high-energy photon emission data (PHTLIB)
Operated by the Los Alamos National Security, LLC for the DOE/NNSA
More MCNPX Features
• Version 2.6.C– Delayed neutrons and gammas– Spherical weight windows– Photon tally tagging
• Version 2.6.D– Coupled space-energy-time weight windows– Activation neutrons and gammas– Background radioactive sources– Muon capture physics– Heavy ion transport
Operated by the Los Alamos National Security, LLC for the DOE/NNSA
New S( , ) Data
2.6.C/new S( , ) file
2.5.0/lwtr.01t
Neutron flux in the water
Operated by the Los Alamos National Security, LLC for the DOE/NNSA
CEM Upgrade
2.6.C neutrons
2.6.C protons2.5.0 protons
2.5.0 neutrons
Secondary particle productionFrom 1-GeV protons onto 56Fe
Operated by the Los Alamos National Security, LLC for the DOE/NNSA
Photon Tally Tagging
27Si
26Si
27Al
26Al
Deexcitation gammas from 28Si
Operated by the Los Alamos National Security, LLC for the DOE/NNSA
MCNP/MCNPX Merger Project
• Goal – Combine all features of MCNPX and MCNP5 into a single code, to be released as MCNP6.
• Principal developers– H. G. Hughes, G. W. McKinney, J. S. Hendricks, J. T. Goorley,
S. J. Pollack, R. E. Prael
• Support– FY07 – 2.5 FTE– FY08 – at least 1.25 FTE
• Expected delivery – end of FY08.
Operated by the Los Alamos National Security, LLC for the DOE/NNSA
MCNP/MCNPX Merger Project: Overview
• ~1000 subroutines in 9 directories• ~500 new subroutines in 8 sub-directories• ~400 subroutines in the MCNP6 …/src/ directory
• ~400 subroutines in the MCNPX …/mcnpf/ directory• 55 new MCNPX subroutines• ~200 subroutines nearly same as MCNP6• ~150 subroutines require careful merging
• Phased approach with building & testing after each step
Operated by the Los Alamos National Security, LLC for the DOE/NNSA
MCNP/MCNPX Merger Project: PlanPhase 1 Phase 5
Move X variables to 6. MCRUN
Reconcile particles, etc. (particle transport)
Phase 2 Phase 6
First half of IMCN MCRUN
(card reading) (sources and tallies)
Phase 3 Phase 7
Second half of IMCN PLOT
(geometry, tallies, materials) (tallies with geometry)
Phase 4 Phase 8
XACT MCPLOT
(proton lib., heating) (mesh tallies)
Operated by the Los Alamos National Security, LLC for the DOE/NNSA
Operated by the Los Alamos National Security, LLC for the DOE/NNSA
Integral Numbers and Energies
• Total energies : In Out NetPhotons 0.1788 0.1788 9.2×10-7 MeVElectrons 3.846×10-4 3.847×10-4 -1.6×10-7 MeV
• Heating estimators: F6:P F8:P,Ecell 1 0.707 0.591 MeV/gmcell 41 0.707 0.619 MeV/gmcell 51 0.694 0.535 MeV/gmcell 61 0.605 0.353 MeV/gm
• Numbers for cell 1: Photons ElectronsIn 0.271 1.69×10-3
Out 0.271 1.69×10-3
Generated 4.56×10-8 5.47×10-5
Lost 4.10×10-8 5.49×10-5
Operated by the Los Alamos National Security, LLC for the DOE/NNSA
Operated by the Los Alamos National Security, LLC for the DOE/NNSA
Operated by the Los Alamos National Security, LLC for the DOE/NNSA
Operated by the Los Alamos National Security, LLC for the DOE/NNSA
10-5
10-4
10-3
10-2
Energy (MeV)
10-3
10-2
10-1
100
101
102
Cou
nts
per
MeV
per
sou
rce
phot
on
MCNP5, DBCN(18) = 1.MCNP5, DBCN(18) = 2.
Cs-137 Source
Operated by the Los Alamos National Security, LLC for the DOE/NNSA
10-5
10-4
10-3
10-2
Energy (MeV)
10-3
10-2
10-1
100
101
102
Cou
nts
per
MeV
per
sou
rce
phot
on
MCNP5, DBCN(18) = 1.MCNP5, DBCN(18) = 2.FLUKAMCNPXfrom B. Grosswendt
Cs-137 Source
Operated by the Los Alamos National Security, LLC for the DOE/NNSA
The End
• Comments ?
• Questions ?