Gamma Radiation: How Does It Pass Through & Damage the Body?

[daisey]

Question about Gamma Radiation. I understand that Gamma Radiation, like X-Rays, are just photons (light particles) at different frequencies. I was reading an article about the Nuclear Plant problems in Japan, and the article stated that photons from Gamma Radiation for the most part pass through the body due to their energy, and because at the quantum particle level, human bodies (and most matter) are mostly empty space. Is this true, and if so how does Gamma Radiation then damage the body?

 

[Borek]

Most of gamma radiation passes through, but not all.

 

[daisey]

OK. So the few photons that do not pass through the body strikes (or otherwise modifies) the atoms comprising the cells inside our bodies. How do these photons now make out bodies "radioactive"? What makes the effect an ongoing reaction inside the body?

 

[bcrowell]

OK. So the few photons that do not pass through the body strikes (or otherwise modifies) the atoms comprising the cells inside our bodies. How do these photons now make out bodies "radioactive"? What makes the effect an ongoing reaction inside the body?

Being exposed to radiation typically does not make the exposed material radioactive itself. There is typically no ongoing nuclear reaction.

 

[Borek]

A lot depends on the energy.

http://en.wikipedia.org/wiki/Gamma_radiation#Matter_interaction

Basically once the gamma photon hits something it is this something that becomes the problem, like ejected electron that ionizes molecules on its path. Note that these electrons are produced inside of the body, they are not stopped by the clothing/radiation suits.

 

[bcrowell]

Basically once the gamma photon hits something it is this something that becomes the problem, like ejected electron that ionizes molecules on its path. Note that these electrons are produced inside of the body, they are not stopped by the clothing/radiation suits.

But this process of ionization is over with in a matter of microseconds -- if you look at what the OP was asking, he/she was assuming that the person's body would stay radioactive.

 

[fzero]

But this process of ionization is over with in a matter of microseconds -- if you look at what the OP was asking, he/she was assuming that the person's body would stay radioactive.

Right, but the problem with ionization in the body is that free radicals can modify DNA, possibly causing cell mutation to cancer. This is the most dangerous kind of damage that gamma radiation causes to the body.

 

[daisey]

But this process of ionization is over with in a matter of microseconds -- if you look at what the OP was asking, he/she was assuming that the person's body would stay radioactive.

When you see someone take a device (Geiger Counter?) on tv to measure the amount of radiation one has received, if the body is no longer radioactive, what is the device measuring? Or do those devices not work for Gamma radiation?

 

[bcrowell]

When you see someone take a device (Geiger Counter?) on tv to measure the amount of radiation one has received, if the body is no longer radioactive, what is the device measuring? Or do those devices not work for Gamma radiation?

It doesn't work that way. You cannot measure the radiation dose a person has received in the past by using a Geiger counter. Typically if you work with radiation, you wear a badge all the time, and it measures your accumulated dose.

 

[bcrowell]

Right, but the problem with ionization in the body is that free radicals can modify DNA, possibly causing cell mutation to cancer. This is the most dangerous kind of damage that gamma radiation causes to the body.

This applies to all ionizing radiation, not just gammas.

Actually, at low doses, ionizing radiation is probably good for you: http://en.wikipedia.org/wiki/Radiation_hormesis

 

[daisey]

It doesn't work that way. You cannot measure the radiation dose a person has received in the past by using a Geiger counter. Typically if you work with radiation, you wear a badge all the time, and it measures your accumulated dose.

Well, I remember seeing technicians on TV wearing white masks waving these electronic devices over people, and I thought they were measuring radioactivity. Maybe they were measuring radioactivity from inhaled contaminants, which I understand do radiate for some time.

 

[Drakkith]

Well, I remember seeing technicians on TV wearing white masks waving these electronic devices over people, and I thought they were measuring radioactivity. Maybe they were measuring radioactivity from inhaled contaminants, which I understand do radiate for some time.

Don't believe what you see on TV. It is almost always wrong. The only radiation that would be detectable from inside you would be gamma radiation from inhaled/ingested particles. I think it's just a widespread misunderstanding on how radiation works and a misportrayal on TV because of this.

Edit: Although if you are talking about real life stuff, like the Japan disaster, then see jshine's post below.

 

[jshine]

Well, I remember seeing technicians on TV wearing white masks waving these electronic devices over people, and I thought they were measuring radioactivity. Maybe they were measuring radioactivity from inhaled contaminants, which I understand do radiate for some time.

There are two slightly different hazards in a reactor accident. On the one hand, you could be exposed to to radiation directly (i.e., like an having an X-ray), or you could inhale or become covered in radioactive dust.

In the 1st case, you would not stay radioactive but could still be damaged by the radiation. In the 2nd case, the dust would stick on your skin or inside your body and you could become detectably radioactive. In general this 2nd case is more damaging, since the radioactive materials can become incorporated into your body, and you absorb radiation over a very long period of time.

It's this 2nd case that the technicians were attempting to detect.

 

[gabvqz]

In the 1st case, you would not stay radioactive but could still be damaged by the radiation.

The CDC states that someone exposed to about 10 grays (externally, no internal ingestion of dust, etc.), they could expect to die in 2 weeks.

Would the corpse be radioactive?

 

[QuantumPion]

The CDC states that someone exposed to about 10 grays (externally, no internal ingestion of dust, etc.), they could expect to die in 2 weeks.

Would the corpse be radioactive?

Only if they were contaminated with radioactive material, or exposed to large amounts of neutron radiation. The latter is extremely rare and would only occur if you were at ground zero of a nuclear bomb, or in close proximity to a nuclear reactor.

 

[Drakkith]

The CDC states that someone exposed to about 10 grays (externally, no internal ingestion of dust, etc.), they could expect to die in 2 weeks.

Would the corpse be radioactive?

No. Without ingesting or inhaling any radioactive material, the only way to get harmed by radiation is from Gamma or Neutron radiation. Gamma radiation will NOT cause anything to become radioactive.

Like QP said above me, the only way for someone to be radioactive in this case would be to have EXTREMELY large doses of neutron radiation. You will NOT get this without being very very close to something like a nuclear reactor or a nuke.