Abstract
Equilibrium evaporation experiments have been conducted to investigate fundamental liquid-to-gas transfer behavior of volatile radionuclides polonium-210 (^<210>Po), cesium, and tellurium in a lead-bismuth eutectic (LBE) that is considered one of the promising coolant materials of Fast Breeder Reactors (FBR) and Accelerator Driven transmutation System (ADS). The experiment utilizes a conventional vapor pressure measurement method: the 'transpiration' method, which has already contributed in a sodium(Na)-cooled FBR study to the understanding of evaporation behavior for volatile fission products (cesium, iodine and tellurium) in a Na pool. Since both LBE pool test and Na pool test focus on the evaporation of the same nuclides in liquid pool, it is possible to compare the nuclides' volatility between in LBE and in Na. This paper describes first the reviewed evaporation characteristics of fission products in Na, next the evaporation test results of fission or activation products in LBE as a continuation of previous papers ICONE12-49111 and ICONE14-89187. The importance of investigating ^<210>Po evaporation is quantitatively demonstrated through specific estimation of the vapor in a cover gas region of a typical LBE-cooled system. Furthermore, comparison under a certain condition is made for the volatility of cesium and tellurium in two kinds of liquid metal coolant Na and LBE using the derived gas-liquid partition coefficients in both tests. The accumulated experimental data can serve as significant database used in accident analysis tools for safety assessment of liquid-metal-cooled nuclear reactor systems.
