Influence of boron vapor on transport behavior of deposited CsI during heating test simulating a BWR severe accident condition

In order to evaluate influence of B on the release and transport of Cs and I during severe accidents, basic experiments have been performed on the interaction between deposited Cs/I compounds and vapor/aerosol B compounds. CsI and B2O3 were utilized as a Cs/I compound and a B compound, respectively. Deposited CsI on the thermal gradient tube (TGT) at temperatures ranging from 423 K to 1023 K was reacted with vapor/aerosol B2O3, and then observed how it changed Cs/I deposition profiles. As a result, vapor/aerosol B2O3 stripped a portion of deposited CsI within a temperature range from 830 K to 920 K to make gaseous CsBO2 and I2. In addition, gaseous I2 was re-deposited at a temperature range from 530 K to 740 K, while CsBO2 travelled through the sampling tubes and filters without deposition. It is evident that B enables Cs compounds such as CsBO2 to transport Cs to the colder regions.