Improved reactivity monitor using a shuttling /sup 252/Cf source

A technique for measuring reactivities of moderated arrays of nuclear fuels with a shuttling /sup 252/Cf source has been significantly extended and refined. In the old method, the shuttle time was so short that details of the delayed neutron time behavior could be neglected. Specifically, the average delayed neutron population during the ''On'' part of the cycles was assumed to be equal to that during the ''Off'' part. In the new method, the detailed behavior of the delayed neutrons is explicitly exploited