Self-diffusion of plutonium in high burn-up simulated (U,Pu)(C,N) and (U,Pu)N

The diffusion of Pu-238 in (Usub(0.8)Pusub(0.2)) Csub(0.8)Nsub(0.2) and (Usub(0.8)Pusub(0.2))N containing simulated fission products equivalent to burn-ups of 3 and 10 at% was studied and compared with Pu tracer diffusion in the corresponding carbonitride and nitride without added fission products. Diffusion in (U,Pu) (C,N) was enhanced in the temperature range of 1420 to 1690 K by more than an order of magnitude with an indicated saturation at a burn-up of approx. < 3 at%, since the data for 3 and 10 at% were identical. A similar enhancement was observed for 3 at% simulated burn-up in (U,Pu)N, but the 10 at% b.u. (U,Pu)N showed lower diffusion rates than the 3 at% b.u. specimens. (orig.)