Question

Which of the following is correct for a nuclear reaction?

• A. A typical fission represented by ${ }_{92} U ^{235}+_{0} n ^{1} \rightarrow_{56} Ba ^{143}+$ ${ }_{36} Kr ^{93}+$ Energy
• B. Heavy water is used as moderator in preference to ordinary water
• C. Cadmium rods increase the reactor power when they go in, decrease when they go outward
• D. Slower neutrons are more effective in causing fission than faster neutrons in case of $U^{235}$

Answer 1

Answer: (A), (C), (D)

In option (A) the reaction given is the fission reaction of $U^{235}$ by a slow neutron hence option $(A)$ is correct. Option (B) is correct as $H$ atoms in ordinary water may capture neutrons, while Deuterium in heavy water does not capture neutrons. Option (C) is not correct as Cadmium rods decreases the reactor power by absorbing neutrons. Option (D) is correct as for $U ^{235}$ slow neutrons causes effective fission whereas in $U ^{238}$ fast neutrons causes effective fission.