Video Transcript
Which of the following correctly
describes whether or not an object is radioactively contaminated? (A) An object is radioactively
contaminated if it has absorbed nuclear radiation. (B) An object is radioactively
contaminated if radioactive material has become joined to it.
This question is asking what must
happen to an object for it to be considered to be radioactively contaminated. To answer this question, we must
understand what “radioactively contaminated” means.
Contamination is a type of mixing
process. A contaminant is something that can
become mixed into uncontaminated objects. The question asks specifically
about radioactive contamination. It is helpful then to recall what
“radioactive” means.
A substance is radioactive if it
contains atoms that can emit nuclear radiation. The meaning of radioactive
contamination is still not exactly clear however. Radioactive contamination could
mean contamination of an object that is caused by radioactive material. Radioactive contamination could
also mean contamination of an object with some radioactive material. A helpful way to further understand
what contaminated means is to understand that an object that is contaminated may go
on to contaminate other objects.
Remembering what we have just been
told about contamination and radioactivity, let us consider the options in the
question. The options are that an object
absorbs nuclear radiation or that an object has had radioactive material join to
it. Let us consider what the difference
between these two options is.
If an object absorbs nuclear
radiation, this means that nuclear radiation has entered the object. If an object has had radioactive
material joined to it, this means that radioactive atoms have entered the
object.
Recall that an object that is
contaminated may go on to contaminate other objects. So, if radioactive contamination
means that an object absorbs nuclear radiation, we could describe the process of
contamination as follows. An object absorbs nuclear radiation
and becomes contaminated. Then, the contaminated object emits
nuclear radiation that can contaminate other objects.
Let us consider an object that is
initially not radioactive, such as water in a container. This water cannot emit nuclear
radiation as it is not radioactive. This water now absorbs some nuclear
radiation from a radioactive rock that is held over the surface of the water. The rock is then taken away. Is the water now radioactive? No, the water will not emit nuclear
radiation. Absorbing nuclear radiation does
not make stable atoms in the water become unstable atoms.
Now, instead, let’s consider what
would happen if you poured some radioactive fluid into a container of pure
water. Since both are fluids, we would
expect them to mix together in the container. After the fluids have mixed in the
container, it is correct to say that unstable atoms from the radioactive fluid have
transferred to the container of water and the water is now a source of nuclear
radiation. Therefore, it is correct to say
that an object, such as the water in our example, is radioactively contaminated when
radioactive material has become joined to it or become a part of it.
Now, we can identify option (B) as
the correct answer. An object is radioactively
contaminated if radioactive material has become joined to it.