# Question: a In power reactors using water as a moderator neutron

(a) In power reactors, using water as a moderator (“neutron slower”) works well, because the proton and neutron have nearly the same mass. Explain why this is true. (b) From your reasoning in part (a), it follows that in a head-on elastic collision, we might expect a neutron to lose all of its kinetic energy in one collision, whereas for an “almost miss,” it might be expected to lose essentially none. Let’s therefore assume that, on average, the neutron loses of its kinetic energy during each proton collision. Estimate how many collisions are needed to reduce a 2.0-MeV neutron to a neutron with a kinetic energy of only 0.02 eV (approximately “thermal”).

## Answer to relevant Questions

Fill in the blank: (a) 11H + _____(, 21H + y, (b) _____+ 32He ( 42He + 211H,. (c) Find the energy released in each. What is the maximum kinetic energy of the electron emitted when a 12B nucleus beta decays into a 12C nucleus? By what minimum amount of energy is the energy conservation “violated” during a πo exchange process? (a) The quark combination for a antineutron is (1) udd, (2) uud, (3) uud, (4) ddd. (b) Prove that your answer to part (a) gives the correct electric charge for the antineutron. At first glance, it would seem that the unstable 7Be nucleus could decay into a stable 7Li nucleus either by capturing an electron or through β+ decay. (a) From an energy point of view, what should occur: (1) only electron ...Post your question