POTENTIAL EUTECTIC FAILURE MECHANISM FOR STAINLESS STEEL CANS CONTAINING PLUTONIUM METAL

Plutonium and iron are known to form a eutectic at a relatively low temperature, i.e., ≈ 400-410°C. A study has been conducted to assess the likelihood that the Pu/Fe eutectic reaction acts as a failure mechanism for stainless steel cans containing plutonium metal. The study consisted of a review of the metallurgical data obtained from diffusion couples and irradiated Pu-bearing metallic fuels, and a thermal analysis of Model 9975 packaging containing Pu metal in a stainless-steel can under a postulated fire scenario in a storage facility, i.e., 800°C for 4 hours. The results of the study show that even in a 800°C fire with a duration of up to 4 hours, the Model 9975 packaging would provide adequate thermal protection, and the 3013 can temperature would stay significantly below the Pu/Fe eutectic temperature of ≈ 400-410°C. Indeed, even if the 3013 can reaches 400°C, the kinetics of the reaction is such that the walls of the 3013 can may survive several days at that temperature. Above 400°C, the progression depends strongly on the peak temperature and duration, as well as the thermal performance of the protective packaging. For facilities that store Pu metals in 3013 cans, whether bare, in Model 9975, and/or in other packagings, a review of the documented safety analysis should be performed, with special attention paid to the fire event. Compensatory measures should be taken, if deemed necessary