Areva has a bulk order in Japan to fit hydrogen recombiners that help to prevent the explosive gas building up in reactor containment during emergency situations.
The French company announced a contract to provide 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, the course of action chosen by Tokyo Electric Power Corporation was to fit versions that required power. 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. While Tepco's hydrogen management was inactive due to the loss of power, the passage of hydrogen to the top of the building was another unexpected aspect of the accident sequence.
Areva said it will install 100 of its devices at various Japanese reactors, without specifying which units.
Researched and written
by World Nuclear News