Tag: nuclear reactor

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Multiple choice chemistry nuclear physics nuclear reactor the nuclear power station isotopes and nuclear chemistry

In nuclear reactor, Cadmium rods are used as

  1. Fuel

  2. Moderator

  3. Control Rods

  4. None
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Cadmium, Boron and Steel rods are used as control rods in a nuclear reactor.
Commonly moderators are Heavy water, graphite and Beryllium and Berillium oride.
Common fuels are Uranium $(^{238}U)$, enriched Uranium $(^{235}U)$ and plutonium $(^{236}{Pu})$ and $^{232}{Th}$

Multiple choice chemistry nuclear physics nuclear reactor the nuclear power station isotopes and nuclear chemistry

Boron rods in a nuclear reactor are used to 

  1. absorb excess neutrons

  2. absorb alpha particle

  3. slow down the reaction

  4. speed up the reaction
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
When a neutron collides with the uranium atom, then energy is released along with three more neutrons which further collide with another uranium atom an so the chain reaction continues. Thus boron rods in nuclear reactor are used to absorb excess neutrons so that the reaction rate remains under control.  
Multiple choice chemistry nuclear physics nuclear reactor the nuclear power station isotopes and nuclear chemistry

Which of the following is a neutron absorber?

  1. $Pb$
  2. $Ag$
  3. $Cd$
  4. $Cu$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
The purpose of neutron absorber is to have a controlled reaction.
The most important neutron absorber is 10B as 10B4C in control rods, or boric acid as a coolant water additive in PWRs. Other important neutron absorbers that are used in nuclear reactors are xenon, cadmium, hafnium, gadolinium, cobalt etc.
Multiple choice chemistry nuclear physics nuclear reactor the nuclear power station isotopes and nuclear chemistry

Control rods used in nuclear reactors are made of

  1. stainless steel

  2. graphite

  3. cadmium

  4. plutonium
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Control rods are used in the nuclear reactor to control the fission rate of uranium and plutonium. These are composed of chemical elements such as cadmium, silver and indium that are capable of absorbing many neutrons without  fissioning themselves.

Multiple choice chemistry nuclear physics nuclear reactor the nuclear power station isotopes and nuclear chemistry

For making atom bomb, what else is needed except $U^{235}$?

  1. neutron

  2. proton

  3. electron

  4. meson
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
The fission of $U-235$ in reactors is triggered by the absorption of a low energy neutron, often termed a "slow neutron" or a "thermal neutron". Other fissionable isotopes which can be induced to fission by slow neutrons are plutonium$-239,$ uranium$-233$, and thorium$-232$.
Multiple choice chemistry nuclear physics nuclear reactor the nuclear power station isotopes and nuclear chemistry

In a nuclear reactor, moderators slow down the neutrons which come out in a fission process.The moderators used have light nuclei. Heavy nuclei will not solve the purpose, because

  1. The net weight of the reactor would be unbearably high.

  2. Heavy nuclei will break generating unwanted smaller nuclei.

  3. Elastic collision of neutrons with heavy nuclei will not slow them down.

  4. Substances with heavy nuclei do not occur in liquid or gaseous state at room temperature.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

In an elastic collision, kinetic energy is transferred most efficiently when the masses of the colliding particles are similar. If a neutron hits a heavy nucleus, it bounces off with almost all its original energy, failing to slow down.