Contamination & Irradiation (Edexcel IGCSE Physics: Double Science)

Contamination

• Contamination is defined as:

The accidental transfer of a radioactive substance onto or into a material

• A substance is only radioactive if it contains a source of ionising radiation
• Contamination occurs when a radioactive isotope gets onto a material where it should not be
  • It is almost always a mistake or an accident e.g. a radiation leak
• As a result of this, the small amounts of the isotope in the contaminated areas will emit radiation and the material becomes radioactive

Irradiation

• Irradiation is defined as:

The process of exposing a material to ionising radiation

• Irradiating a substance does not make it radioactive
  • However, it can kill living cells

• Irradiation is usually a deliberate process, such as in the sterilisation of food or medical equipment
  • Surgical equipment is irradiated before being used in order to kill any micro-organisms on it before surgery
  • Food can be irradiated to kill any micro-organisms within it to make it last longer

This sign is the international symbol indicating the presence of a radioactive material

Protection from irradiation and contamination

• Radiation can mutate DNA in cells and cause cancer through both irradiation and contamination
  • Therefore, it is important to reduce the risk of exposure to radiation

• Contamination is particularly dangerous if a radioactive source gets inside the human body
  • For example, through the inhalation of radioactive gas particles, or ingesting contaminated food
  • The internal organs will be irradiated as the source emits radiation as it moves through the body

• To prevent irradiation, shielding can be used to absorb radiation
  • Lead-lined suits are used to reduce irradiation for people working with radioactive materials
  • The lead absorbs most of the radiation that would otherwise hit the person

• To prevent contamination, an airtight suit is worn by people working in an area where a radioactive source may be present
  • This prevents radioactive atoms from getting on or into the person

Lead shielding is used when a person is getting an x-ray, as well as for people who work with radiation. Contamination carries much greater risks than irradiation

Differences between irradiation and contamination

• The differences between irradiation and contamination are summarised in the table below:

Comparison of irradiation and contamination table

	Irradiation	Contamination
description	when an object is exposed to a source of radiation but does not become radioactive	when an object becomes radioactive due to the presence of a source of radiation
source	exposure to source of radiation outside the object	exposure to source on or within the object
prevention	blocked by using shielding such as lead	radiation cannot be blocked once an object is contaminated, but can be prevented by handling the source safely
causes	caused by the deliberate exposure to radiation	caused by the accidental transfer of radioactive material