Hydrogen can present a very real danger in nuclear reactors if the concentration is allowed to build to levels where combustion becomes possible. In most scenarios powerplants have various measure to prevent the build-up of hydrogen during design basis accidents. However, during severe accidents these measures may not be available, or the production of hydrogen may exceed these capabilities. In most accidents’ hydrogen is formed through the corrosion of metals such as Aluminum or Zirconium or the radiolysis of water. In most cases this is a very small amount and takes days for hydrogen to build to dangerous levels. In more sever accidents there are three primary sources of hydrogen in most nuclear plants.
- Oxidization of metals such as Zirconium and chemicals like Boron Carbide in the reactor.
- Oxidization of metals such as Zirconium, Chrome and Iron inside the containment building.
- Oxidization of metals through interaction with concrete (can only occur once the core has melted through the vessel).