Besides cooling the fuel (and thus producing the steam) the water also ACTS as a moderator, slowing down the neutrons and keeping the reaction going.

水源除用于冷却燃料外(也由此生成蒸汽)，还起到调节介质的作用，它能使中子减速，并使核反应持续进行。

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From these results, it is concluded that the reflector with steel and boron water has positive reactivity effect on the core with boroned moderator.

通过实验发现，对于具有硼慢化剂的铁硼水反射层堆芯，堆芯具有正的反应性效应。

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Heavy water is used as a moderator in nuclear power plants, slowing down the fast neutrons so that they can react with the fuel in the reactor.

重水可用作核电厂的减速剂，减缓快速运动的中子以使它们能和反应炉的燃料一起反应。

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He was less than impressed, for example, when the moderator of the press conference - who was sitting beside Reeves - accepted a glass of water the actor had intended for the film's director, Scott Derrickson.

BBC: Science friction with star Reeves