INSTITUTE OF NUCLEAR POWER ENGINEERING
NPE 6104: RADIATION MEASUREMENT AND PROTECTION
OCTOBER 2024
ASSIGNMENT 01
MOTASIM FAIYAZ
1024 322 027
DATE OF SUBMISSION: 23 / 7/ 2025
Ans 1: When a heavily charged particle passes through a medium, it dissipates its
energy by ionizing its surrounding particles. This dissipation of energy is shown using
Bragg’s curve. Initially protons move fast ionizing few electrons from surrounding
particle but as it slows down it interacts more with surrounding matter causing a spike
in energy lost that’s when the Bragg’s curve reaches its maximum point, it is called the
Bragg’s peak.
Unlike protons, photons do not ionize they only scatter or get absorbed. Since protons
are charged, they allow down due to ionization and when slowed their interaction cross
section increases, producing Bragg’s peak. But photons, get absorbed at discrete
energy levels as photoelectric effect, Compton scattering and pair production.
An 𝛼-particle is comprised of 2 protons and 2 neutrons ( 42He nuclei). After its emission,
the resulting nuclei becomes neutron rich which causes it to be unstable. As a way of
regaining stability, neutron in the nuclei breaks down into a 𝛽-particle and an antineutrino.
Ans 2:
1) Elastic Scattering: When a neutron hits a nucleus and bounces off without
transferring any of its energy to the nucleus.
2) Inelastic Scattering: When a neutron with high enough energy hits a nucleus
transferring some of its energy to the nucleus exciting it. To go back to an
unexcited state, the nucleus releases the energy in the form of Gamma radiation.
3) Absorption: The neutron gets caught into the nucleus and the nucleus can
release energy by decaying or gamma radiation.
4) Fission: only occurs in fissile atoms like U-235 and Pu-239. It is after a neutron
has been absorbed and the nucleus splits into two lighter nucleus and more
neutrons releasing vast amounts of energy
Low energy neutrons have a higher absorption cross-section
Elastic scattering happens regardless of how much energy is contained in a neutron.
However, it is desirable that it happens at low energy levels so reactors can be
moderated
Fast moving neutrons undergo inelastic scattering and fission.
Ans 3: Mass of electrons is 1/1836th of that of a proton. Being lighter makes their path
more unpredictable and they collide amongst themselves more often than other
particles. This causes the tortuous path and scattering. Also, High energy electrons
dissipate its energy as bremsstrahlung radiation. That’s why electrons are more prone
to spreading and does not dissipate energy locally.
Ans 4: Both the rays are electromagnetic waves and that’s where their similarity ends.
Gamma rays have higher frequency than X-rays. Besides their frequencies, their origins
are also defining factors.
Gamma rays come from subatomic events such as radioactive decay from excited
nucleus, nuclear fissions, fusions, annihilation of matters and antimatters, supernovae
or neutron stars, blackholes colliding.
X-rays are produced through electronic transition, especially of free electrons. When a
free electron loses its energy hitting a metal, the nucleus emits x-ray as bremsstrahlung
radiation. When electrons are ejected out of inner shells of an atom, outer shell
electrons fall down to their position taking their place and in turn emitting X-ray, called
characteristic x-ray. Particles spinning at high speeds in synchrotrons, Compton
scattering and etc.
Ans 5:
Alpha particles: often referred to as 42He nucleus are heavily positively charged
particles and highly ionizing. Can be stopped by paper and layer of dead skin.
Dangerous if ingested or inhaled, can damage DNA causing cancer.
Beta particles: often Negatively charged and rarely positively, often referred to as
electrons. Lighter in mass moderately ionizing. Can be stopped by plastic and few mm
of Aluminum. Poses external danger to skin may burn skin, damage eye and can
damage internal organs if consumed.
Gamma rays: they are electromagnetic waves with high energy. Highly penetrative can
be mostly blocked by thick lead or concrete, but still then some of it will pass through.
They don’t carry charges making them weakly ionizing but dangerous externally and
internally. They can cause deep tissue ionization, like other radiations they can also
damage DNA causing cancer and severe radiation poisoning.
Neutrons: A subatomic particle. Neutral, deeply penetrating, indirectly ionizing which
makes it very dangerous for the fauna can turn stable atoms in living things radioactive.
Can be stopped by hydrogenous or heavy shielding.
X-rays: refer to a range of high energy electromagnetic waves but they have energy just
lesser than Gamma rays. Highly penetrating can be stopped by tissue paper to lead
depending on the energy of the wave. In high doses they can be dangerous externally
they can also cause deep tissue ionization and DNA damage.
Radiation
Alpha 𝛼
Beta 𝛽
Gamma 𝛾
Neutron n
X-ray
Context:
Inhalation/ Ingestion
Contact/ Ingestion
External exposure
Nuclear Reactors
Medical Imaging/ External exposure
Ans 6:
Bremsstrahlung X-rays: When free electrons are decelerated by a nucleus getting
excited. When returning to a stable state the nucleus emits X-ray.
Characteristic X-rays: When inner-shell electrons are made to exit the orbitals of an
atom, out shell electrons fill out the inner shell and as it does so, it de-excites and emits
energy in the form of X-ray of a specific energy.
Delta rays: When a heavily charged particle like proton or alpha particle interacts with
matter while passing through, sometimes they knockout electrons the matter’s atom.
The knocked-out electrons are called delta rays. They can ionize more after they have
been knocked out causing a secondary ionization.
Auger electrons: When inner-shell electron is made to shot out, an outer shell electron
fall down to fill its space it releases energy but the energy gets absorbed by another
electron in the very same atom so no resulting X-ray emission.