Boron chemistry during transportation in the high temperature region of a boiling water reactor under severe accident conditions

Revaporization Behavior of Cesium and Iodine Compounds from Their Deposits in the Steam–Boron Atmosphere

“…TeRRa is equipped with a horizontal thermal gradient tube (TGT) and a set of accompanying analyses of FP behavior for both deposits and aerosol at respective temperature regions in the TGT. The capability of TeRRa to reproduce those complex processes had been demonstrated in the earlier works, , thus enabling it for further utilization in the present investigation. Through this study, we aim to overcome the knowledge gap of the interaction mechanism among CsI deposits, steam, and boron, and therefore, this could lead to more reliable development of the Cs-I-B-O-H system in the ECUME database.…”

“…Therefore, it is consistent with the less iodine amount at this location by ICP-MS analysis (Figure a). The form of boron at the initial state would exist as condensed B 2 O 3 or boric acid vapors (HBO 2 , (HBO 2 ) 3 , and H 3 BO 3 ) depending on its concentration in the gas flow, i.e., B/H 2 O ratio . Then, it would formalize the mechanism of the boron–CsI interaction.…”

“…Such a kind of comprehension will aid in the use and improvement of SA analysis codes like MELCOR or THALES-2 to assess the source term. In the framework of the OECD/NEA BSAF project (Organisation for Economic Co-operation and Development/Nuclear Energy Agency–Benchmark study of the accident at the Fukushima Daiichi NPS), these analytical codes encountered some issues related to FP chemistry due to the inherent complex phenomena and also lack of supporting data for relevant chemical interactions, which at last have induced uncertainties in analyzing the release and transport behaviors of FPs. , Recognizing the significant impact of the said release and transport behavior of FPs, fundamental research studies on FP chemistry have been initiated in the Japan Atomic Energy Agency (JAEA) encompassing separate- and integral-test experiments. − The objectives of those research studies are primarily to evaluate FP chemistry and to create and/or improve existing FP chemistry models for database ECUME (Effective Chemistry database of fission products Under Multiphase rEaction). , The ECUME database consists of three datasets including (1) chemical reaction kinetics, (2) elemental models, and (3) thermodynamic properties, which are implementable in the SA analysis codes. The phenomena and behaviors of FP in ECUME are selected based on the importance and priority for decommissioning work of 1F and safety enhancement of the reactor, where they consist of chemical interaction in the gas phases and gas–condensed phases.…”

“…In the present study, we investigate the gas-condensed phase reaction of the Cs-I-B-O-H system using an integral test facility built in JAEA. The test facility called TeRRa (Test-bench for FP Release and tRansport) is designed to reproduce the chemical interaction during FP transport in a severe accident, , including complex physical and chemical processes of condensation and deposition on the wall of the structural material and aerosol formation/growth as it transits in the reactor coolant system (RCS) . TeRRa is equipped with a horizontal thermal gradient tube (TGT) and a set of accompanying analyses of FP behavior for both deposits and aerosol at respective temperature regions in the TGT.…”

Investigation of the Outflow and Spreading-Solidification Behaviour of Stratified Molten Metal

“…However, in practical accidents, molten corium stratifies between fuel and structural components due to density differences [24,25]. If the material distribution in the fuel debris were not homogeneous, it would affect the selection of the cutting devices [26], aerosol removal management [26,27], and even re-criticality management for fuel debris retrieval [28].…”