Close on the heels of Fukushima nuclear disaster, the state-run Nuclear Power Corporation (NPC) would install hydrogen recombiners in all 20 plants to avoid hydrogen explosion and thereby mitigate disaster.
According to NPC's initial estimates, an investment of about Rs 500 crore would be required for the installation of hydrogen recombiners. At present, the Bhabha Atomic Research Centre (BARC) has prepared a design of a hydrogen recombiner.
Hydrogen recombiner is an apparatus, which efficiently and safely recombines hydrogen and oxygen gas to form water vapour. This is used in nuclear reactor system in which potentially dangerous hydrogen gas, evolved within the containment vessel during certain postulated accident conditions, can be eliminated. Further, this apparatus also aids in removal of certain radioactive contaminants from gases in a containment vessel.
NPC Chairman and Managing Director SK Jain, in his comprehensive presentation made on Tuesday to BARC and NPC scientists on Fukushima disaster and the measures being worked out to upgrade safety at nuclear plants, announced NPC would go in for installation of hydrogen-management devices such as hydrogen recombiners at all 20 plants.
Jain explained hydrogen gas is explosive in high concentration when it comes into contact with oxygen. If hydrogen is not removed in a controlled manner in case of an accident, the containment building can be jeopardised. Jain noted four core committees appointed by NPC to make recommendations on short and long-term measures to strengthen safety applications at all nuclear plants in the wake of the Fukushima nuclear disaster made a strong case for installation of hydrogen recombiners.
An NPC official told Business Standard, “In Fukushima, as the reactor containment was maintaining high it caused the hydrogen to escape through the top flange of reactor containment. The hydrogen found its way and accumulated on the roof top until it formed a explosive mixture and finally ignited and created explosion.
Therefore, learning a lesson from the Fukushima incident, the core committee have called for installation of hydrogen recombiners at all 20 nuclear plants in the country. This will be done in phases.”
The official said BARC has prepared a design, which can be used for Indian plants. Similarly, hydrogen recombiners would also have to be imported. He said details with regard to plant-wise investment for hydrogen recombiners are being worked out. However, he added it would not be less than Rs 500 crore for all plants.
BARC, in its recent research paper, said several methods have been envisaged to limit the hydrogen concentration in the containment. These include deliberate ignition of mixture, removal of oxygen, dilution of containment atmosphere either by increase in containment volume or by injection of inert gas and catalytic recombination.
Among the provisions included to mitigate the consequences of a massive hydrogen production in the core,with subsequent release in the containment, introduction of hydrogen recombiners in key locations is a very effective one.