CIE IGCSE Physics (0625) Safety precautions Study Notes - New Syllabus
CIE IGCSE Physics (0625) Safety precautions Study Notes
LEARNING OBJECTIVE
- Understanding the concepts of Safety precautions
Key Concepts:
- Effects of Ionising Nuclear Radiation on Living Organisms
- Safe Handling of Radioactive Materials
Effects of Ionising Nuclear Radiation on Living Organisms
Effects of Ionising Nuclear Radiation on Living Organisms:
Ionising radiation includes alpha (α), beta (β), and gamma (γ) radiation.These radiations have enough energy to remove electrons from atoms, creating ions – a process called ionisation.
When living tissue is exposed to this radiation, the ionisation can affect the molecules that make up cells – especially DNA.
Main Biological Effects:
1. Cell Damage and Death: High doses of ionising radiation can kill cells outright by damaging their structure. This is called radiation sickness if many cells are killed.
2. Mutations in DNA: Ionising radiation can break DNA strands or cause mutations in genetic material. This can:
- Lead to non-functional or malfunctioning proteins
- Affect the cell’s ability to divide or repair
3. Cancer: Damaged or mutated cells may start dividing uncontrollably, leading to tumours and cancer. This is a long-term effect and more likely with repeated low-level exposure.
4. Inherited Mutations: If radiation affects reproductive cells (sperm or egg), the mutations can be passed on to offspring.
Severity Depends On:
- Type of Radiation: Alpha is highly ionising but only harmful if ingested or inhaled; gamma penetrates and can damage deep tissue.
- Amount/Dose: Higher radiation doses cause more damage.
- Duration of Exposure: Long or repeated exposure increases risk.
- Part of the Body Exposed: Some tissues (like bone marrow or reproductive organs) are more sensitive.
Example:
A hospital worker accidentally comes into close contact with an unshielded beta radiation source for an extended period. A few weeks later, they begin experiencing symptoms including fatigue, reduced white blood cell count, and irregular cell growth.
▶️ Answer/Explanation
- Fatigue and reduced white blood cells: Beta radiation penetrated the skin and ionised cells in the bone marrow, damaging rapidly dividing white blood cells → weakening the immune system.
- Irregular cell growth: Ionisation caused mutations in the DNA of some cells. Some of these mutated cells began to divide uncontrollably, which could lead to cancer.
- Type of radiation: Beta particles have medium penetration and ionising power. They can enter the body through skin and cause internal tissue damage if unshielded.
Safe Handling of Radioactive Materials
Safe Handling of Radioactive Materials
Radioactive materials emit ionising radiation, which can damage living tissues. Therefore, strict safety protocols are followed when moving, using, and storing these substances.
1. Moving Radioactive Materials
- Sealed in lead-lined containers to block radiation during transport.
- Clear hazard warning labels (radioactive symbol) are placed on containers.
- Remote handling tools or shielding tongs used to load/unload sources.
- Transport regulations require proper documentation and only trained personnel to handle the materials.
2. Using Radioactive Materials Safely
- Use for the shortest time possible to reduce exposure.
- Operators use tongs or robotic arms to increase distance and avoid direct contact.
- Always wear protective clothing, like lab coats and gloves, especially when using open or unsealed sources.
- Work is done behind protective barriers, such as lead screens or glass windows.
- Radiation levels are constantly monitored using dosimeters or Geiger counters.
3. Storing Radioactive Materials
- Kept in lead-lined storage containers in designated radiation-safe rooms or secure cabinets.
- Containers are clearly labelled and locked to prevent unauthorized access.
- Stored materials are regularly inspected and inventory is tracked to avoid leaks or loss.
- Access to storage areas is limited to trained and authorised personnel only.
Example:
Which of the following practices is the most important when handling radioactive sources in a school laboratory?
- A. Holding the source close to the body to prevent dropping it
- B. Wearing ear protection to reduce exposure to the source
- C. Using long tongs to handle the source at a distance
- D. Keeping the source uncovered for better visibility
▶️ Answer/Explanation
C. Using long tongs to handle the source at a distance
Increasing distance from a radioactive source significantly reduces radiation exposure according to the inverse square law.
Some more Safety Precautions for Ionising Radiation
Ionising radiation (alpha, beta, and gamma) can damage living tissues by causing ionisation in cells. To protect workers and the public, safety measures are based on three principles: reducing time of exposure, increasing distance from the source, and using shielding to absorb radiation.
1. Reduce Exposure Time
- Minimise the time spent near radioactive sources to limit radiation dose.
- Plan and rehearse procedures in advance so exposure is brief.
- Use remote tools (like tongs or robotic arms) to speed up handling safely.
2. Increase Distance from the Source
- Radiation intensity decreases with distance (follows inverse-square law).
- Use long-handled tools to handle radioactive materials from afar.
- Restrict access to radiation zones and keep people as far from the source as practical.
3. Use Shielding to Absorb Radiation
- Shielding materials absorb radiation and protect people nearby.
- Alpha particles: stopped by a sheet of paper or skin, but require containment if source is ingested or inhaled.
- Beta particles: require plastic or thin metal (e.g. aluminium).
- Gamma rays: require dense materials like thick lead or concrete barriers to reduce exposure.
- Operators often work behind lead glass screens in labs and hospitals.