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⚡ Radioactive Contamination

Spec 6.4.2.4 📗 Foundation
📖 In-Depth Theory

Contamination vs Irradiation

These two terms are often confused but describe very different situations:
RADIOACTIVE CONTAMINATION:
Unwanted radioactive material is DEPOSITED ON or INSIDE a person or object.
The contaminating material continues to emit radiation over time.
The source stays with the person/object — ongoing exposure.
Example: breathing in radon gas; swallowing radioactive dust; radioactive material on skin.
IRRADIATION:
The person or object is EXPOSED TO RADIATION from a source that is NOT attached to them.
When the person moves away from the source, exposure stops.
Example: standing near a radioactive source; medical X-ray; radiotherapy.
KEY DIFFERENCE:
Contamination = source stays with you.
Irradiation = source is external, exposure ends when you move away.

Hazards of Each Type

CONTAMINATION HAZARDS:
Alpha sources are especially dangerous as INTERNAL CONTAMINANTS:
Alpha particles are highly ionising but very short range.
Inside the body they deposit all their energy in nearby cells → severe local tissue damage.
External alpha contamination (on skin) is less dangerous — alpha cannot penetrate skin.
Beta and gamma internal contamination is also serious — penetrate to internal organs.
IRRADIATION HAZARDS:
Depends on radiation type, dose and duration.
Gamma is most dangerous external source — penetrates deeply into tissue.
Alpha from external source: stopped by skin, relatively safe.
Beta: penetrates skin, can damage underlying tissue.
LONG-TERM EFFECTS:
Ionising radiation damages DNA → mutations → increased cancer risk.
High acute doses → radiation sickness, cell death.
Eyes, bone marrow and gonads particularly sensitive.

Precautions and Safe Use

PRECAUTIONS TO PREVENT CONTAMINATION:
Never touch radioactive materials directly — use TONGS or remote handling.
Wear PROTECTIVE CLOTHING (gloves, lab coat) to prevent skin contact.
WORK IN WELL-VENTILATED areas to prevent inhaling radioactive dust or gases.
No eating, drinking or applying make-up in radioactive areas — prevents ingestion.
Seal radioactive materials in appropriate containers.
PRECAUTIONS TO REDUCE IRRADIATION:
DISTANCE — intensity follows inverse square law; doubling distance reduces dose by ¾.
SHIELDING — appropriate material (paper for alpha, aluminium for beta, lead/concrete for gamma).
TIME — minimise exposure duration.
DOSIMETERS — worn by radiation workers to monitor cumulative dose.
PROFESSIONAL GUIDELINES:
Radiation workers have annual dose limits.
Regular monitoring of workplace radiation levels.
Storage of radioactive sources in lead-lined containers when not in use.
BENEFITS vs RISKS:
Medical uses (X-rays, radiotherapy, tracers) involve balancing dose risk vs diagnostic/treatment benefit.
Risk is managed, not eliminated.
⚠️ Common Mistake

Contamination and irradiation are NOT the same. Contamination: radioactive material on/in you — source travels with you. Irradiation: external source — exposure stops when you move away. Alpha is most dangerous as INTERNAL contaminant (highly ionising, short range → all energy deposits locally).

📌 Key Note

Contamination: source deposits on/in person — ongoing. Irradiation: external exposure — stops when away from source. Alpha most dangerous internally. Gamma most dangerous externally. Precautions: tongs, shielding, distance, dosimeters, sealed containers, ventilation. Benefits vs risks must be balanced.

🎯 Matching Activity — Contamination vs Irradiation

Sort each scenario into contamination or irradiation. — drag the symbols on the right to match the component names on the left.

Contamination
Drop here
Contamination
Drop here
Irradiation
Drop here
Irradiation
Drop here
Most dangerous internally
Drop here
Breathing in radioactive dust — source is now inside the body
Alpha radiation — highly ionising, short range, deposits all energy nearby
Standing near a gamma source — move away and exposure stops
Medical X-ray — brief external exposure, no source deposited
Radioactive material spilled on skin — source remains in contact
🎯 Test Yourself
Question 1 of 2
1. A worker accidentally inhales radioactive dust containing an alpha emitter. Why is this particularly dangerous?
2. A radiographer takes X-rays of patients all day. Which precaution best reduces their radiation dose?
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