Physics – 5.2.5 Safety precautions | e-Consult

Ionising radiation poses a risk to living tissue by damaging cells and potentially leading to long-term health problems. To minimise this risk, three key principles are employed: reducing exposure time, increasing distance from the source, and using shielding.

Reducing Exposure Time: The intensity of ionising radiation is often proportional to the time spent exposed. Therefore, minimizing the duration of exposure is crucial. Example: In medical imaging using X-rays, healthcare professionals strive to use the lowest possible radiation dose for the shortest possible time to obtain a clear image. This involves careful planning of the exposure parameters and efficient imaging techniques. Similarly, in nuclear medicine, procedures are designed to minimise the time a patient is exposed to radioactive isotopes.

Increasing Distance from the Source: The intensity of ionising radiation decreases significantly with increasing distance. This inverse square law means that doubling the distance reduces the intensity to one-quarter. Example: When working with radioactive sources, maintaining a safe distance is paramount. Radiation detectors are used to monitor the radiation levels at different distances, ensuring that the exposure is kept below acceptable limits. In nuclear reactors, the fuel rods are shielded by thick concrete structures to protect personnel from the radiation emitted.

Using Shielding: Shielding materials absorb or attenuate ionising radiation, reducing the amount that reaches living tissue. The effectiveness of a shield depends on the type of radiation and the material used. Example: Lead is commonly used as shielding against gamma rays because it is dense and effectively absorbs these high-energy photons. Water is also an effective shield against gamma and X-rays due to its high water content. For alpha particles, a thin sheet of paper or even the outer layer of skin is sufficient to block them. For beta particles, materials like plastic or aluminum are effective. The choice of shielding material depends on the type of radiation being used and the desired level of protection.

These three principles are often used in combination to provide comprehensive protection against ionising radiation. They are fundamental to ensuring the safety of individuals working with or exposed to ionising radiation.