Recent developments in low-energy electron/photon transport for MCNP6

Recently a variety of programmatic needs have driven the development of improved methods for low-energy photon/electron transport in the Monte Carlo particle transport code MCNP6. Aspects of this development include a significant reworking of the MCNP coding to allow for consideration of much more detail in atomic relaxation processes, new algorithms for reading and processing the Evaluated-Nuclear-Data-File photon, electron, and relaxation data capable of supporting such detailed models, and extension of the electron/photon transport energy range below the traditional 1-kilovolt limit in MCNP, with the goal of performing transport of electrons and photons down to energies in the few-electron-volt range.