Fission Reaction Event Yield Algorithm, FREYA — For event-by-event simulation of fission

Abstract

From nuclear materials accountability to detection of special nuclear material, SNM, the need for better modeling of fission has grown over the past decades. Current radiation transport codes compute average quantities with great accuracy and performance, but performance and averaging come at the price of limited interaction-by-interaction modeling. For fission applications, these codes often lack the capability of modeling interactions exactly: energy is not conserved, energies of emitted particles are uncorrelated, prompt fission neutron and photon multiplicities are uncorrelated. Many modern applications require more exclusive quantities than averages, such as the fluctuations in certain observables (e.g. the neutron multiplicity) and correlations between neutrons and photons. The new computational model, FREYA (Fission Reaction Event Yield Algorithm), aims to meet this need by modeling complete fission events. Thus it automatically includes fluctuations as well as correlations resulting from conservation of energy and momentum. FREYA has been integrated into the LLNL Fission Library, and will soon be part of MCNPX2.7.0, MCNP6, TRIPOLI-4.9, and Geant4.10. Program summaryProgram title: FREYA 1.0Catalogue identifier: AEVS_v1_0Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEVS_v1_0.htmlProgram obtainable from: CPC Program Library, Queen’s University, Belfast, N. IrelandLicensing provisions: Special LLNL licenceNo. of lines in distributed program, including test data, etc.: 187792No. of bytes in distributed program, including test data, etc.: 2585089Distribution format: tar.gzProgramming language: Fortran 90, C++.Computer: Any computer with a Fortran 90 and a C++ compiler, tested with(a) Intel Xeon CPU X5660, 2.8 GHz, 48 GB RAM,(b) Intel(R) Xeon(R) CPU E5-2620, 2 GHz, 64 GB RAM,(c) Intel Xeon CPU W3520, 2.67 GHz, 6 GB RAM.Operating system:(a) Red Hat Enterprise Linux Server release 6.5 (GNU Fortran and g++ (GCC) 4.4.7 20120313 (Red Hat 4.4.7-4)),(b) CentOS release 6.4 (GNU Fortran and g++ (GCC) 4.4.7 20120313 (Red Hat 4.4.7-3)),(c) MacBook Pro OSX 10.6.8 (GNU Fortran and g++-mp-4.7 (MacPorts gcc47 4.7.3 5) 4.7.3).RAM: 6 GBClassification: 17.8.Nature of problem: Modeling of fission events.Solution method: Simulation of complete fission events, production of secondary fission fragments, fission neutrons and photons.Restrictions: Restricted to spontaneous fission of 238 U, 240 Pu, 244 Cm, 252 Cf; neutron-induced fission of 233 U, 235 U, 239 Pu, for incident neutron energies less than 20 MeV.Running time: 8 s for 1M events