zài / hé fǎnyìng duī / zhōng / màn huà jì / bèi / yònglái / jiàngdī / zhōngzǐ / de / yùndòng / sùdù在核反应堆中,慢化剂被用来降低中子的运动速度。In a nuclear reactor, a moderator is used to reduce the speed of neutrons.