Areva is to fit all 23 Japanese pressurized water reactors with hydrogen recombiners that help to prevent the explosive gas building up in emergency situations.

The French company announced a contract to provide a bulk order of its passive autocatalytic recombiners. The devices use catalytic oxidation to turn traces of hydrogen into steam, a process that works constantly and requires no power. They will be fitted in the reactor unit containment vessels to help prevent hydrogen explosions and “preserve the integrity of the reactor,” said Areva.

Many nuclear operators installed systems to manage hydrogen after the partial core melt at Three Mile Island in 1979. Unfortunately, this was not the case in Japan. During the accident at Fukushima Daiichi last year, many hours without power for cooling water pumps saw nuclear fuel in the cores of units 1, 2 and 3 overheat to the point that zirconium fuel cladding oxidised in the presence of steam, producing hydrogen and oxygen. At units 1 and 3 this was able to escape the containment and concentrate in the tops of the buildings, where it eventually exploded and caused extensive physical damage to those units as well as unit 4.

Areva said it will install more than 100 of its devices at the Japanese pressurized water reactors, which make up 23 of the country’s 50-reactor fleet. The reactor type is used at the following Japanese nuclear power plants: Ikata, Mihama, Ohi, Sendai, Takahama, Tsuruga, Tomari and Genkai.

Researched and written
by World Nuclear News