Secondary Emission Radiation

[imp]

For a long time, I have wondered about the following condition, mentioned in textbooks and elsewhere, but never fully explained (at least not to my satisfcation).

 

Objects exposed to ionizing radiation, such as x-rays, gamma rays, and the sort, tend to become sources of radiation themselves (radioactive) upon removal of the original source.

 

How true is this? What conditions must be met for it to occur? If true, why is the equipment in hospitals' x-ray facilities not secondarily radioactive? Or is it, to some degree?

 

Information would be appreciated! imp

[SkepticLance]

The answer is no.

 

Radiation that is part of the electromagnetic spectrum will not render other materials radioactive.

 

Is it possible you got it mixed up with particulate radiation? A rain of alpha particles or neutrons can do it.

[insane_alien]

actually, gamma rays can cause nuclear transitions into metastable states which will emit a gamma photon when they decay at a later date. tends to happen with isotopes that are gamma emitters that have already decayed.

[Klaynos]

In addition to IA's comments.

 

If the photons are absorbed by atoms and the electrons can do one of two things, if the energy is great enough an electron can be moved into the vacuum level. Or they can move up energy levels, it is then possible that they decay into a metastable state which will decay radiating at a later time. But most meta stable states are fractions of a second before they decay so it doesn't really count.

[swansont]

actually, gamma rays can cause nuclear transitions into metastable states which will emit a gamma photon when they decay at a later date. tends to happen with isotopes that are gamma emitters that have already decayed.

 

In addition you can get a [math](\gamma,n)[/math] or [math](\gamma,p)[/math] reaction (eject a neutron or proton) that leaves you with an unstable isotope (activation). The distinction here is that to ionize an atom — remove an electron — it take a few eV, but to remove a nucleon, it takes several MeV of energy. X-rays are typically in the keV range, so they are ionizing radiation, but not enough to activate. Even a lot of gammas aren't energetic enough to cause activation.

 

A secondary effect of a [math](\gamma,n)[/math] reaction would be the subsequent absorption of the neutron by another nucleus, potentially causing activation.

[imp]

In addition you can get a [math](\gamma,n)[/math] or [math](\gamma,p)[/math] reaction (eject a neutron or proton) that leaves you with an unstable isotope (activation). The distinction here is that to ionize an atom — remove an electron — it take a few eV, but to remove a nucleon, it takes several MeV of energy. X-rays are typically in the keV range, so they are ionizing radiation, but not enough to activate. Even a lot of gammas aren't energetic enough to cause activation.

A secondary effect of a [math](\gamma,n)[/math] reaction would be the subsequent absorption of the neutron by another nucleus, potentially causing activation.

 

So, very energetic ionizing radiation, like mev+, can bring about secondary emission, which may be particulate OR gamma? Therefore, detonation of a nuclear bomb is likely to render surrounding objects which survive the heat blast secondarily radioactive?

 

I can understand that electron movement from one shell to another may cause emission of photons, but never thought that to be other than visible light, ala the laser. imp

[swansont]

So, very energetic ionizing radiation, like mev+, can bring about secondary emission, which may be particulate OR gamma? Therefore, detonation of a nuclear bomb is likely to render surrounding objects which survive the heat blast secondarily radioactive?

 

I can understand that electron movement from one shell to another may cause emission of photons, but never thought that to be other than visible light, ala the laser. imp

 

A nuclear bomb emits neutrons, too, and neutron activation is probably the biggest effect. There are certainly gammas, but I'm not sure how many really energetic ones you'd get.