Study on fission-product behavior in liquid sodium using inpile loop

The behavior of fission products (F.P.) in liquid sodium, which is one of the most important aspects for the safety and economy of fast breeder reactors (LMFBR), was studied by using an inpile loop at Toshiba Training Reactor. Fission products can be classified into three groups concerning the behavior in sodium liquid systems: (1) nonvolatile F.P. quickly deposit on the inner surface of the loop; (2) volatile F.P., such as I, Cs, Te, are dissolved in sodium and reversibly adsorbed on cooler parts of the loop; distribution coefficients of their adsorption were obtained as temperature functions; (3) gaseous F.P. are released from liquid sodium into cover gas, and the degassing constant was obtained. From these studies, an outline of the F.P. behavior in LMFBRs was understood in some detail and their distribution in the primary cooling system became quantitatively predictable for several nuclides. (author)