Before the 3/11 earthquake and tsunami, there were two nuclear power plants in Fukushima, both on the coast. (Nuclear power plants must be near a source of water.) Both were/are owned by the Tokyo Electric Power Company (TEPCO) and supplied electricity to Tokyo.
ONE of the power plants was fine, and was safely shut down. The other one had meltdowns. Look at the Google map views. Which do you think was the power plant that melted down? Which was the one that was safely shut down?
First, Dai ichi. (Literally: Power Plant Number One)
Second, Dai Ni. (Literally, Power Plant Number Two)
If you know you know your numbers in Japanese—-Ichi, Ni, San, Shi, Go (One, Two, Three, Four, Five) then the names make sense.
In kanji, these numbers are: 一二三四五