At Fukushima Dai-ichi nuclear power plant zircaloy that was used for cladding tube was exposed to high temperature steam and Hydrogen was produced by rapid oxidation. Essentially produced oxygen had to be sealed in containment vessel and released to the air by venting. However Hydrogen released from containment vessel were stored in reactor building and exploded at the NPP.

From the experience engineers recognized that countermeasure to prevent Hydrogen leak from containment vessel was required. Unfortunately there are few studies relevant to Hydrogen permeability at high temperature and demanded Hydrogen permeability coefficient of sealing material in the case of high temperature exposure.

In this study tests were conducted to predict Hydrogen permeability through rubber gasket at ACCIDENT. Experimental conditions were 1) deteriorated by heat, 2) deteriorated by heat and steam, 3) at high temperature.

Tests were conducted for Silicone rubber, EPDM, NBR and Fluoro-rubber and we found that there was no significant difference between the rubbers Hydrogen permeability coefficient under conditions from 1) to 3) without the case of losing its elasticity.

Currently we can present basic data to predict Hydrogen leak volume from containment vessel to reactor building at ACCIDENT. Based on the data we calculated Hydrogen leak volume from containment vessel through top flange of Fukushima Dai-ichi nuclear power plant in the case that zircaloy was melted completely as example.

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