NEUTRON CROSS SECTIONS FOR FUSION.

First generation fusion reactors will most likely be based on the **3H(d,n)**4He reaction, which produces 14-Mev neutrons. In these reactors, both the number of neutrons and the average neutron energy will be significantly higher than for fission reactors of the same power. Accurate neutron cross section data are therefore of great importance. They are needed in present conceptual designs to calculate neutron transport, energy deposition, nuclear transmutation including tritium breeding and activation, and radiation damage. They are also needed for the interpretation of radiation damage experiments, some of which use neutrons up to 40 Mev. The quality of currently available data for these applications is reviewed and current experimental programs are outlined.