Question

Part VI: Apply Your Knowledge Many smoke detectors contain a small amount of the isotope Americium-241, which emits alpha radiation. Should a person walking under such a smoke detector be concerned about being hit by the alpha particles? Explain your answer using something you learned in this lab. In the medical imaging procedure known as a PET scan (Positron Emission Tomography), positrons from a radioactive tracer strike electrons in the body's tissues. This produces radiation, and this radiation is then observed using a detector outside the body. Based on this information, do you think the positron-electron collisions create alpha, beta, or gamma radiation? Explain your answer using something you learned in this lab,

Answer 1

Ans 1

Am-241 emits both alpha radiation and low-energy gamma rays. The alpha particles are absorbed within the detector, while most of the gamma rays escape. Americium has atomic number 95 and an average atomic mass of 243. Metallic americium is a silvery metal, which tarnishes slowly in air and is soluble in acid. There are no stable isotopes of americium, and hence it is extremely scarce in nature.

The radiation dose to the occupants of a house from a domestic smoke detector is very small, very much less than that from natural background radiation due to cosmic rays, naturally occurring radioactive elements such as potassium, or radon. The small amount of radioactive material that is used in these detectors is not considered to be a health hazard. When smoke detectors using americium were first introduced, they were labelled as requiring return to the supplier or shipment to the (then) Atomic Energy Control Board for disposal in Canada. This requirement was later withdrawn, although some jurisdictions (e.g., Australia) require special disposal. There is probably some “spent fuel waste” in your local landfill in the guise of defunct smoke detectors. 241Am is a potentially hazardous isotope, decaying by both alpha activity and gamma emissions. If it enters the body in a chemically available form, it would concentrate in the skeleton. However, swallowing the radioactive material from a smoke detector would not lead to significant internal absorption of 241Am. Since the dioxide is insoluble, it will pass through the digestive tract, without delivering a significant radiation dose. Inhaling AmO2 as dust particles could lead to it residing in the lungs. Alpha particle emitters present a biological hazard when inside the body, since the alpha particles are absorbed in a small volume near the source, increasing the risk of cell damage that may result in cancer. The low-energy gamma rays are less hazardous as they interact over a larger volume. 241Am decays to an isotope of neptunium (237Np), emitting an alpha particle with an energy of approximately 5.5 MeV and gamma rays, with the majority having an energy of 60 keV. 237Np has a half-life of 2.14 million years, and also decays by alpha emission (4.9 MeV). Because of its long half-life, 237Np is less hazardous than 241Am. (Very rarely, 241Am undergoes spontaneous fission.)

Ans 2

PET scans are often used with CT or MRI scans to help make a diagnosis or to get more data about a health condition and the progress of any treatment.

There is a risk of radiation exposure.

For most people, the benefits of having a PET scan

Normally, a pregnant woman should not have a PET scan, as the radioactive material may affect the fetus or the infant.

Very rarely, an individual may have an allergic reaction to the tracer.Side effects or allergic reactions are extremely rare, as the radioactive tracers are usually based on water and not iodine like X-ray contrast. Patients can eat, drink, and drive a car after having a PET scan, and will not feel sick or dizzy.

Although the tracer contains a low dose of radiation, it may pose a risk to patients who are pregnant or breastfeeding. Please notify our staff if there is any chance of pregnancy before the procedure begins. Patients are advised to avoid contact with anyone who is pregnant, breastfeeding or very young children for a few hours after the procedure.