Skip to content
MathsGenie logo
Open app

Course home

  1. A Level
  2. Physics AQA
  3. Question bank

Radioactivity (A-level only)

EasyMediumHard
12345678910111213141516171819202122232425262728293031323334353637383940414243444546474849505152535455565758596061626364656667686970
Question 29

A thermal nuclear reactor relies on various physical processes to operate safely and efficiently.

a.

Explain why the kinetic energy of neutrons must be significantly reduced in a thermal nuclear reactor.

[2]
b.

As a result of a collision with an atom of a particular moderator, a neutron loses 55%55\%55% of its kinetic energy. A neutron initially has a kinetic energy of 2.5 MeV2.5\text{ MeV}2.5 MeV. Calculate the kinetic energy of this neutron after four collisions. Give your answer in eV\text{eV}eV.

[3]
c.

The kinetic energy of a neutron in a thermal nuclear reactor is reduced from about 2.5 MeV2.5\text{ MeV}2.5 MeV to about 1 eV1\text{ eV}1 eV. Explain why the number of collisions required to achieve this reduction depends on the nucleon number of the moderator atoms.

[3]
d.

One fission process that can occur in the reactor is represented by the following equation: 92235U+01n→54140Xe+3893Sr+301n^{235}_{92}\text{U} + ^{1}_{0}\text{n} \rightarrow ^{140}_{54}\text{Xe} + ^{93}_{38}\text{Sr} + 3^{1}_{0}\text{n}92235​U+01​n→54140​Xe+3893​Sr+301​n Calculate, in MeV\text{MeV}MeV, the energy released in this single fission process.

Data:

  • mass of 92235U=235.044 u^{235}_{92}\text{U} = 235.044\text{ u}92235​U=235.044 u
  • mass of 54140Xe=139.922 u^{140}_{54}\text{Xe} = 139.922\text{ u}54140​Xe=139.922 u
  • mass of 3893Sr=92.914 u^{93}_{38}\text{Sr} = 92.914\text{ u}3893​Sr=92.914 u
  • mass of 01n=1.0087 u^{1}_{0}\text{n} = 1.0087\text{ u}01​n=1.0087 u
  • 1 u=931.5 MeV1\text{ u} = 931.5\text{ MeV}1 u=931.5 MeV
[3]

Radioactivity (A-level only) Questions

  1. A Level
  2. /Physics
  3. /Radioactivity (A-level only)