Thermochromatographic behavior of iodine in fused silica columns when evaporated from lead–bismuth eutectic

Abstract

As a step toward licensing a lead–bismuth eutectic (LBE) based reactor design, the adsorption behavior of iodine evaporated from LBE on fused silica was examined. Using inert and reducing carrier gases, depositions with an adsorption enthalpy of − 95 to − 113 kJ mol−1 were observed. These depositions are compatible with a single species, tentatively identified as bismuth monoiodide, BiI. When introducing oxidizing conditions, multiple iodine species with higher volatility form, with adsorption enthalpies ranging from − 67 to − 86 kJ mol−1. Based on an empirical correlation one of these species was identified as monatomic iodine. This work provides fundamental understanding of the LBE/iodine gaseous chemistry and related adsorption deposition behavior.

Silver as a capturing material for iodine released from lead–bismuth eutectic in various conditions

“…This finding indicates that a pretreatment of oxidized silver surfaces with hydrogen should enhance the adsorption of iodine in real life filtering systems designed based on this technology. The formation of multiple very volatile species in oxygen carrier gas which was previously observed in similar adsorption studies employing fused silica and steel surfaces [3,4] is not found here due to the high deposition temperature and instability of these molecules in comparison to the strong Ag-I bond. In addition, no formation of an oxide scale has been observed in the high temperature section of the silver surface due to the thermodynamic instability of Ag 2 O even in oxygen atmosphere.…”

“…At inert and reducing conditions full or near full evaporation was achieved (Table 1). An earlier study on the adsorption of iodine evaporated from LBE on fused silica surfaces employed thermodynamic calculations and empirically determined correlations between sublimation and adsorption enthalpies to assign a speciation to the evaporated and deposited iodine species [3]. The results of this work indicate the presence of the heavy metal iodide BiI in inert and reducing conditions, while oxidizing conditions induce the formation of monatomic iodine and more volatile iodine oxides and hydroxides.…”

“…The measured deposition temperatures range from 388 °C to 636 °C with extracted adsorption enthalpies of − 171 kJ mol −1 to − 208 kJ mo l −1 . This adsorption interaction is much stronger than the adsorption observed on reactor construction materials such as 316L stainless steel as well as on fused silica (concrete analogue) [3,4]. Oxidizing carrier gas was found to introduce a retention leading to incomplete evaporation of Next to the deposition peak the temperature of the tube at the peak maximum is given.…”

“…Previously, iodine dissolved in LBE has been observed to form particularly volatile reaction products when evaporated from LBE into oxygen [3,4]. This effect was postulated to result from oxidation of the iodine prevailing in oxidation state -1 in the liquid metal solution or the bismuth monoiodide evaporated from it.…”

“…In the present work, we address the behavior of iodine released from LBE. With respect to the deposition and capture of iodine species evaporated from LBE, two adsorbent surfaces have been studied in different gas atmospheres, fused silica as an analogue for concrete [3] and 316L stainless steel [4] as a major structural component suggested for the reactor. Both of these surface materials displayed only moderate retention, especially in an oxygen atmosphere where iodine may form particularly volatile species.…”