Half-Life & Risk Flashcards

All 6 cards in this deck

Why is a source with a very short half-life hazardous?

Its activity is very high, so it emits a lot of ionising radiation in a short time.

Why is a source with a very long half-life hazardous?

It stays radioactive for a very long time, so it remains a hazard and must be stored or disposed of safely for years.

What half-life is suitable for an isotope injected into a patient as a tracer?

A few hours: long enough for the scan to be taken, but short enough that it soon decays away inside the patient.

True or false? A medical tracer should have a half-life of several days.

False. It would stay in the body too long, giving the patient an unnecessarily high dose.

Why is an isotope with a half-life of a few minutes unsuitable for a scan lasting 30 minutes?

It decays too quickly to give a reading for the whole scan.

Why does a thickness gauge in a factory use a source with a very long half-life?

So the count rate stays steady over time and the source does not need replacing or recalibrating often.