Ok. This question is pretty 'elementary' but I do not know much about how a NPP works. I read an article
that said that the US delivered coolant to Japan. Why does Japan need the coolant? I don't understand how an earthquake and a tsunami can make a NPP lose its coolant? Also, what specific purpose does the coolant serve in the plant (what exactly does it cool) and what would happen if Japan could not get more coolant?