BURNUP OF SOME REFRACTORY-METALS IN A FUSION NEUTRON-SPECTRUM

For some materials, neutron-induced transmutations are predicted to le ad to substantial changes in elemental composition over neutron exposu re times comparable to expected component service lives. These changes involve the partial burnup of elements initially present and the accu mulation of transmutation products, to a point at which materials prop erties may be adversely affected. Tantalum, tungsten and the alloy W-2 6Re are studied as examples and allowance is made in inventory predict ions for 'self-shielding' effects that are found to be important in th ese materials. The evolution of elemental compositions is examined as a function of exposure time and the implications for materials propert ies are briefly discussed.