Okay kiddo, let me tell you what happened at Fukushima Daiichi nuclear power plant.
First things first, we need to understand what a nuclear power plant is. It's like a big power station that uses the energy from tiny particles called atoms to make electricity.
Now, in March 2011, there was a very strong earthquake in Japan. The earthquake caused a big tsunami which is like a huge wave that washed over the land. The tsunami was so strong that it damaged the nuclear power plant at Fukushima Daiichi.
As a result of this damage, some of the parts inside the power plant stopped working properly, and the power plant couldn't cool itself down. And when a nuclear power plant gets too hot, bad things can happen.
The heat caused one of the reactors in the power plant to be damaged, the metal surrounding the fuel rods started to melt and radiation was released into the air. That radiation could cause harm to people nearby.
People who live near the power plant had to leave their homes to protect themselves from radiation. For many years after, this area was marked as unsafe for people to live in.
Scientists and experts worked really hard to try and make the power plant safe again so people could come back home. They even tried to build big walls around the power plant to stop the radiation from spreading.
It was a really tough time for the people of Japan and the world was very worried for them. And that's what happened at Fukushima Daiichi nuclear power plant, kiddo.