# The fast neutrons can easily be slowed down by :

$(a)\;applying\;strong\;electric\;field\qquad(b)\;elestic\;collisions\;with\;heavy\;nuclei\qquad(c)\;passing\;them\;through\;heavy\;water\qquad(d)\;use\;of\;lead\;shielding$

In nuclear engineering, a neutron moderator is a medium that reduces the speed of fast neutrons, thereby turning them into thermal neutrons capable of sustaining a nuclear chain reaction involving uranium-235.
Commonly used moderators include regular (light) water (roughly 75% of the world's reactors), solid graphite (20% of reactors) and heavy water (5% of reactors).
Beryllium has also been used in some experimental types, and hydrocarbons have been suggested as another possibility.
Answer is (C) passing them through regular water, heavy water or graphite
answered Mar 6, 2014 by
edited Apr 2, 2014