Radioactivity 4 Ionizing Radiation LOJ Feb 2004 What

Radioactivity (4) Ionizing Radiation LOJ Feb 2004

What is an ion? • An ion is an atom or molecule that has a different number of electrons and protons and therefore a net charge. LOJ Feb 2004

Ionization • When radiation from radioactive materials collides with neutral atoms or molecules these may become charged (ionized). LOJ Feb 2004

Ionization of living cells • When radiation ionizes molecules in living cells it can cause damage, including cancer. • The larger the dose of radiation the greater the risk of cancer. • Dose of radiation depends on – the intensity of the radiation and – the time of exposure. LOJ Feb 2004

When sources of radiation are outside the body: • beta and gamma radiation are the most dangerous because they can reach the cells of organs and may be absorbed by them; • alpha radiation is least dangerous because it is unlikely to reach living cells (it is absorbed by the dead skin cells on the surface of your skin!) LOJ Feb 2004

When sources of radiation are inside the body: • alpha radiation is the most dangerous because it is so strongly absorbed by cells; • beta and gamma radiation are less dangerous because cells are less likely to absorb the radiation. The key idea here is the localization of the damage! – The more localized (concentrated) the damage is, the less likelihood that the body can cope! LOJ Feb 2004

Damage to living tissue • The more localized the damage in living tissue the greater the chance of mutations occurring. • DNA is the material within cells that carries the information about the living creature. LOJ Feb 2004

Damage to living tissue • DNA molecules are long helical strands with four different types of branches coming off the stem. • If these branches are altered in any way the biological 'code' is altered and the cell may reproduce itself 'wrongly'. This can lead to tumors in the living being itself and/or mutated offspring if reproductive cells are affected. LOJ Feb 2004

Damage to living tissue • Biological systems can cope with one or two 'faults', detect them and deal. . but if the damage is highly localized there may be too many and defective cells may reproduce and cause problems. Even under extreme magnification, the double helix is almost too small to be seen clearly. LOJ Feb 2004

Damage to living tissue • Therefore the highly localized damage caused by alpha particles is most dangerous. Even under extreme magnification, the double helix is almost too small to be seen clearly. LOJ Feb 2004

Alpha Danger • If the alpha source is outside the body the alpha particles would all be absorbed by the outer (dead) layer of skin cells. . . but if it is within the body it could cause damage to vital organs. • That is why powdered sources of alpha emitters are highly dangerous. LOJ Feb 2004

Alpha Danger • Tiny grains can be inhaled and lodge sources of alpha particles deep in the lungs, or swallowed and get lodged in the digestive system etc. • Tiny grains of a radioactive source can contain millions of atoms. LOJ Feb 2004

Beta danger • Beta sources are less likely to cause as much extensive damage in a localized area as an alpha source of the same activity, but the risk of mutation is still there and all radiation sources are dangerous. LOJ Feb 2004

Gamma Danger • Gamma sources lodged inside your body would send out gamma rays: high energy electromagnetic waves that would mostly pass through you. LOJ Feb 2004

Gamma Danger • Some would interact with your body - so they ARE dangerous to you, but most would get straight out and make you a source of radiation to those around you! • These are the only radioactive sources that it is worth the risk of putting inside a patient for diagnostic reasons LOJ Feb 2004

Monitoring radioactivity • Workers who are at risk from radiation often wear a radiation badge to monitor the amount of radiation they have been exposed to over a period of time. LOJ Feb 2004

Monitoring radioactivity • The badge is a small packet containing photographic film. The more radiation a worker has been exposed to, the darker the film is when it has been developed. LOJ Feb 2004

Film Badges • Hospital workers and those in the nuclear industry are most likely to use these badges. • The badges have sections with areas of different coverings to help assess what type of radiation the person has been exposed to. LOJ Feb 2004