Hazards of Contamination & Irradiation

Contamination Hazards

Contamination occurs when radioactive material is deposited on or inside an object or person. This radioactive material emits radiation, which can be harmful.

Radioactive material on surfaces can be found on skin, clothes, tools, or work surfaces. If contaminated, these surfaces emit alpha, beta, or gamma radiation, which can damage nearby cells.

Risk of internal exposure: Contamination is particularly dangerous if radioactive particles enter the body through breathing, swallowing, or cuts in the skin. Inside the body, alpha and beta radiation can cause significant damage to cells and tissues because they are close to living cells.

Sources of contamination include spills of radioactive substances, improper handling of radioactive materials, or contact with contaminated objects.

Preventing contamination involves strict control measures such as:

• Wearing protective clothing (gloves, lab coats, masks)
• Using sealed containers for radioactive materials
• Working in controlled areas with restricted access
• Regular cleaning and monitoring of workspaces
• Proper disposal of radioactive waste

Irradiation Hazards

Irradiation happens when an object or person is exposed to radiation from a radioactive source but does not become contaminated. The radiation passes through or hits the body externally.

Exposure to radiation source can cause damage to cells even if the source is outside the body.

External radiation effects depend on the type of radiation:

• Alpha particles: Cannot penetrate skin; only harmful if inside the body.
• Beta particles: Penetrate skin but usually stopped by a few millimetres of tissue.
• Gamma rays: Highly penetrating; can pass through the body and require dense shielding.

Penetration of different radiation types affects how dangerous irradiation is:

• Alpha radiation is least penetrating but most ionising.
• Beta radiation penetrates moderately and can cause skin burns.
• Gamma radiation penetrates deeply and can affect internal organs.

Minimising exposure time reduces the dose of radiation received. The less time spent near a source, the lower the risk.

Health Risks of Radiation

Radiation can damage living cells by ionising atoms within them. This can lead to:

• Cell damage and mutations: Radiation can break chemical bonds in DNA, causing mutations that may disrupt normal cell function.
• Increased cancer risk: Mutations can lead to uncontrolled cell division, causing cancer. The risk increases with higher doses and longer exposure.
• Acute radiation sickness: Very high doses over a short time can cause symptoms like nausea, vomiting, hair loss, and skin burns.
• Long-term effects: Even low doses can increase the chance of cancer later in life. Damage to reproductive cells can cause genetic defects.

The severity of health effects depends on the dose, type of radiation, and which part of the body is exposed.

For instance, dose (in mSv) = dose rate (mSv/hour) × time (hours). If a person is exposed to a gamma radiation source delivering a dose rate of 0.5 mSv per hour, and they stay near it for 4 hours, the total dose received is:

$\text{Dose} = 0.5 \times 4 = 2 \text{ mSv}$

This dose is low but repeated or longer exposure increases health risks.

Safety Measures

To protect against contamination and irradiation hazards, several safety measures are used:

• Use of shielding: Dense materials like lead or thick concrete block or reduce radiation. For example, lead aprons protect against beta and gamma radiation.
• Maintaining distance: Radiation intensity decreases sharply with distance (inverse square law). Radiation intensity decreases with the square of the distance from the source, so doubling the distance reduces exposure to a quarter. Standing further away reduces exposure.
• Time management: Minimising the time spent near radioactive sources reduces total dose.
• Protective clothing and equipment: Gloves, lab coats, masks, and sometimes respirators prevent contamination and reduce internal exposure.

These measures are combined in workplaces handling radioactive materials, such as hospitals, nuclear power plants, and research labs.