Atomic Reactor
Nuclear Reactor
noun
If a 原子 is an atom and a 炉 is a furnace, what is a furnace that has atoms? It is an atomic reactor or nuclear reactor.
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own.
原子炉の建設について、政府に忠告をした人もいました。
Some people warned the government against building nuclear reactors.