A unit used in British nuclear engineering to describe the "reactivity" of a nuclear reactor. One millinile is a reactivity of 10-5. For a discussion of reactivity, see: inhour
Russ Rowlett (Director), How Many? A Dictionary of Units of Measurement, Center for Mathematics and Science Education University of North Carolina, USA 2005. http://www.unc.edu/~rowlett/units/dictA.html, (Unit of Meas and Covr Factors - Amer) {608}