  We investigated the use of neutron activation to estimate the 30Si mole
fraction of the ultra-pure silicon material highly enriched in 28Si for the
measurement of the Avogadro constant. Specifically, we developed a relative
method based on Instrumental Neutron Activation Analysis and using a natural-Si
sample as a standard. To evaluate the achievable uncertainty, we irradiated a 6
g sample of a natural-Si material and modeled experimentally the signal that
would be produced by a sample of the 28Si-enriched material of similar mass and
subjected to the same measurement conditions. The extrapolation of the expected
uncertainty from the experimental data indicates that a measurement of the 30Si
mole fraction of the 28Si-enriched material might reach a 4% relative combined
standard uncertainty.
