Physics Simulation Packages

Main Page for Nuclear Physics Downloads
LLNL has developed self-contained physics simulations that can be interfaced to any parent transport code. Currently we provide three distinct simulation codes (listed below). We also provide interface examples for popular Monte Carlo transport codes such as MCNP, MCNPX, and Geant4.

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Generates correlated cosmic-ray particle showers at one of three elevations (sea level, 2100m, and 11300m) for use as input to transport and detector simulation codes. Provides all particle production (muons, neutrons, protons, electrons, photons, and pions) within a specified area (up to 300m by 300m) as well as time of arrival and zenith angle of secondary particles. Provides basic correlations between paticles within the shower, latitude, and solar cycle variations. Fast simulation based on precomputed input tables derived from full MCNPX simulations of primary cosmic rays (1 GeV to 100 TeV primary particles) on full atmosphere model. Function library callable from C, C++, and Fortran.

Documentation: User manual, Physics description.
Downloads (version 1.7): Install from source
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Calculates intrinsic gamma-ray spectrum from the nuclear decay of a mixture of radioisotopes. Uses Bateman solution to determine aged isotope concentrations and processes radioactive decay database to produce gamma-ray intensities from published decay energy lines. Provides interactive program (radsrc) and function library callable from C, C++, and Fortran.

Documentation: User manual and physics description
Downloads (version 1.6): Install from source, Mac OS X binary
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Simulates discrete neutron and gamma-ray emission from the fission of heavy nuclei, this includes spontaneous, neutron-induced, or photon-induced fission. Produces neutron and gamma-ray list from individual fission events by statistical sampling of distributions based on a combination of measured data and analytic models. The samples are taken from separate distributions of the particle multiplicity and energy. This is a function library, callable from C, C++, and Fortran, that encapsulates the fission physics and is intended to be called by an external Monte Carlo transport code.

Includes Fission Reaction Event Yield Algorithm (FREYA). FREYA enables the emission of completely correlated fission secondaries from individual realizations of fission processes on an event-by-event basis for the following isotopes:
neutron-induced fission U-233, U-235, U-238, Pu-239 and Pu-241, up to En = 20 MeV
spontaneous fission U-238, Pu-238, Pu-240, Pu-242, Cm-244, and Cf-252


LLNL Fission Library 2.0.2 User manual and physics description
FREYA 2.0.2 User manual
Changes between FREYA 1.x and 2.0.2

Downloads (install from source): LLNL Fission Library v2.0.5
Older versions

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Additional BSD Notice


Douglas Wright (