Calculations have been done to develop estimates of the fluence rate of unscattered x and gamma rays emerging from two model spheres of special nuclear material: one of uranium enriched to 93.5% by weight of U-235; one of plutonium enriched to 6.0% by weight of Pu-240.

This document is intended to give a detailed report on the service offered by NIST for the calibration of ionization chambers in terms of the quantity absorbed dose to water.