Another breakdown on the info superhighway, so lets try this again. Eyeballing the graph on page 92-338-22 of the BNL 325 Neutron Cross Section Book (2nd ed., 1965), the 17 MeV fission cross-section for U-238 is approx. 1.4 barns. Is PG&E converting to a fast reactor? :) Regards, L. Bobek, Director WPI Reactor