Japan’s Air Self-Defense Forces have dropped water into the Number Three and Number Four reactors at the Fukushima Number One nuclear power plant to cool the reactor in hopes of preventing an explosion and radiation leakage.

The Self-Defense Forces dropped a total of 30 tons of water on the reactors for cooling purposes through the use of helicopters on Thursday morning.

The helicopters first measured the radiation level in the air and dropped the water while maintaining constant movement to avoid possible exposure to radiation.

At the Fukushima nuclear power plant, the Number Three reactor is suspected of having sustained damage to its container following a hydrogen explosion on Monday. A radiation leakage is feared at the Number Four reactor due to exposed spent fuel rods.