Monte Carlo N-Particle Transport (MCNP)[2] is a general-purpose, continuous-energy, generalized-geometry, time-dependent, Monte Carlo radiation transport code designed to track many particle types over broad ranges of energies and is developed by Los Alamos National Laboratory.
The code treats an arbitrary three-dimensional configuration of materials in geometric cells bounded by first- and second-degree surfaces and fourth-degree elliptical tori.
[3] The creators of these methods were Stanislaw Ulam, John von Neumann, Robert Richtmyer, and Nicholas Metropolis.
[4] Monte Carlo for radiation transport was conceived by Stanislaw Ulam in 1946 while playing Solitaire while recovering from an illness.
In 1947, John von Neumann sent a letter to Robert Richtmyer proposing the use of a statistical method to solve neutron diffusion and multiplication problems in fission devices.
He suggested 100 neutrons each to be run for 100 collisions and estimated the computational time to be five hours on ENIAC[6][circular reference].
While waiting for ENIAC to be physically relocated, Enrico Fermi invented a mechanical device called FERMIAC[7] to trace neutron movements through fissionable materials by the Monte Carlo method.
In the 1950s and 1960s, these new methods were organized into a series of special-purpose Monte Carlo codes, including MCS, MCN, MCP, and MCG.