Because your fuel is liquid, and it's combined with your coolant, you could actually just drain the core into what's called a sub-critical setting, basically a tank underneath the reactor that has some neutrons absorbers.
燃料は液体で 冷却剤と一緒になっているので 炉心を流し出して 臨界以下の条件に落とせます 基本的には反応炉の下にある 中性子吸収剤の入ったタンクに落とすのです