Three Mile Island was a nuclear power plant located in Pennsylvania. In 1979, pressure began to increase in the second reactor. The valve was supposed to be closed, but it was stuck open with no workers aware of the problem. Therefore, cooling water was quickly covering the nuclear reactor core.
The cooling water was overflowing on the sides, and was not cooling the reactor core. Therefore, the reactor core was overheated and formed a hydrogen bubble that almost exploded and breached containment. Officials were worried that radioactive gas would be spread.
Officials later found out that half of the core melted. Luckily, minimal damage was done outside, as not much radioactive material was exposed in the air.
The heat rising inside the nuclear reactor core caused a hydrogen bubble to form. This hydrogen bubble left the population on edge, not knowing if it was going to explode. Luckily, there was not enough oxygen for the hydrogen to bubble to explode, and it eventually dwindled down.
The nuclear regualtory comission chairman ordered pregnant women and little children to evacuate thier homes if they were within a five-mile radius of the Three Mile Island plan