Improvements in electron-photon-relaxation data for MCNP6

We have provided a brief discussion of four recent enhancements and corrections to the electron, photon, and atomic relaxation data of the eprdata series of data libraries included with the MCNP6 distribution. There are two changes based on the new data that have potential importance for calculations: an alternate elastic cross sections and sufficient precision in the tabulation of the angular probability distribution functions for large-angle electron elastic scattering, especially at high energies. Two changes are primarily formal corrections: it was not the average energy of a Bremsstrahlung photon that was tabulated previously but the average energy remaining to the electron after a Bremsstrahlung event. The second correction deals with an inconsistency between the data in the library and how it was used by early versions of MCNP (MCNP5 and MCNPX): the probability that the incoherently scattered photon has interacted with a particular electron shell is presented in the data library as a tabulated probability density function, while the MCNP5 and MCNPX codes treated the table as a cumulative distribution