Control of Beryllium-7 in liquid lithium

Abstract

Radiation fields created by the production of 7Be in lithium of the Fusion Materials Irradiation Test (FMIT) Facility can be sufficiently high to prevent contact maintenance of system components. Preliminary experiments have shown that 7Be will adhere strongly to the FMIT piping and components and a good control method for 7Be must be develop, ed. The initial experiments have been conducted in static stainless steel capsules and a Modified Thermal Convection Loop (MTCL). The average lithium film thickness on stainless steel was found to be 11 μm in the temperature range 495°–571°K from the capsule experiments. The short-term experiments showed that 7Be migrates to the capsule wall and the long-term experiment indicated that 7Be actually penetrates into the stainless steel wall. The diffusion coefficient for 7Be in stainless steel at 543°K was calculated to be 5.31 × 10−15 cm2/sec. The cold leg of the MTCL picked up much of the 7Be activity released into the loop. The diffusion trap, located in the cold leg of the MTCL, was ineffective in removing 7Be from lithium, at the very slow flow rates (< 3.79 × 10−4 m3/s) used in the MTCL. Pure iron has been shown to be superior to cobalt and nickel as a getter material for 7Be.