[3E01-03] Behavior of Radioactive Nuclides 1

[3E01] Investigation of effect by the late-phase release of boron-containing atmosphere on CsI deposit formed on reactor structural material SUS304L

*Muhammad Rizaal¹, Shuhei Miwa¹, Eriko Suzuki¹, Jumpei Imoto¹, Masahiko Osaka¹, Mélany Gouëllo² (1. Japan Atomic Energy Agency, 2. VTT Technical Research Centre of Finland)

Keywords:Cesium iodide, boron, thermal gradient tube, cesium borates, SUS304L

The gaseous species interaction with the early FP deposits (mostly Cs and I) on the surface of reactor coolant system (RCS) material is considered as one of the factors of gaseous iodine generation at the late phase and could affect the containment atmosphere. In this study, we investigated the reaction of CsI deposit formed on stainless steel type 304L with the steam-boron flow. The experiments for reproducing the RCS temperature gradient in the range of 1000–400 K showed a significant depletion of CsI at 850 K, resulted in the formation of low volatile cesium borates on the former surface, and simultaneously released gaseous iodine that could reach a range below 400 K.