Radiation facts and myths

[Polymer Bob]

Why exactly is everyone concerned about the power plants right now? Everyone was evacuated and supposedly didn't receive much harmful radiation. There are dangers of further explosion. Is the issue that those could cause additional gamma radiation that would travel further than the evacuation zone and put people in danger?

If I might interject here. It seems the news media and governmental organizations use the term "radiation" differently than physicists. The media and organizations are not so much concerned with direct neutron, alpha, beta and gamma rays; which weaken with the square of the distance. They are concerned with the release of radioactive elements into the environment. This stuff would get into the air and water and travel with the wind and currents. The inverse square law goes out the window at that point.

[rfisher]

rfisher, thank you very much for this post. I am no scientist so all the radiation stuff they talk about in the news goes right over my head... My stupid-ass question, if you could be so kind to respond: Why exactly is everyone concerned about the power plants right now? Everyone was evacuated and supposedly didn't receive much harmful radiation. There are dangers of further explosion. Is the issue that those could cause additional gamma radiation that would travel further than the evacuation zone and put people in danger?

Worst case scenerio, yes. If there was a full scale meltdown of the nuclear material there would be a huge explosion which would disperse radioactivity over a larger area. Not only would there be problems for anybody in the area, but the ground would be contaminated. It's unlikely that anybody would suffer Acute Radiation Syndrome which happens with a total body exposure of more than 2-3 Sv (that's Seivert not milliseivert and is a substantial dose), but the risk of cancers such as leukemia and thyroid would increase. Leukemia being the most common. This happened with the Chernobyl meltdown.

One big problem that happened with above ground nuclear testing was the dispersal of Strontium-90 as part of the fall out. Strontium is uptaken in grass. Animals that eat the grass, such as cows, can pass the isotope through their milk. Prevention of that worst case is what the engineers are doing. I can't imagine the stress levels at those reactors. It's kind of like a whack-a-mole game where you hit one and another pops up. Chernobly did teach that the nuclear material needed multiple containment fields and all modern reactors have those additional safety features.

[rfisher]

If I might interject here. It seems the news media and governmental organizations use the term "radiation" differently than physicists. The media and organizations are not so much concerned with direct neutron, alpha, beta and gamma rays; which weaken with the square of the distance. They are concerned with the release of radioactive elements into the environment. This stuff would get into the air and water and travel with the wind and currents. The inverse square law goes out the window at that point.

The inverse square law still applies to particulate radiation. However, the dispersal of radioactive particles would be the concern. I'm not certain what material is in rods or if the decay products are alpha, beta or neutron producers along with gamma. It doesn't really matter in regard to nuclear fission (well it matters which elements you use but not whether they are an alpha producer). It's the heat given off duing the decay event that drives the steam turbines to create electricity. Each of those would have a different impact if there was widespread dispersal. Alpha particles are heavy (they are essentially helium nuclei) but have a very short range. Beta are small (essentially a nuclear electron) with a longer range. Gamma is wave form electromagnetic energy and will be dispersed by wind fairly quickly. All of which is esoteric and wouldn't matter to the impacted population if the worst happened.

This is one of the issues associated with a dirty bomb. Most wouldn't have an explosive chage sufficient to spread the radioactive material in a wide circumference, thus the overall damage would be somewhat limited. It's the psychological damage that would be catastrophic. Not that if you were one of the people within that circumference it wouldn't be catastrophic.
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And MarieM, the US has planned to store all the nuclear waste in some expaned natural caverns beneath Yucca Mountain in the west. They carted stuff around the country for a couple of years and nobody would let them put it in their backyard. They finally made a deal to deposit it here, but so far the nothing has been done. The project has been blocked by several environmental suits. The site is in a seismically active area (quakes and volcanos) and the risk of contamination has been the basis for the courts to rule in favor of the enviornmentalists. The stuff is still sitting around in steel barrels happily corroding away.

[Yehudi]

I've been using this site as the main source for info on the nuclear situation. It's a pro-nuclear industry site so of course, you don't want to be too reliant on this site (the twitter feed for the media guy makes my eyes roll), but it's been the most informative in terms of the steps being taken to cool down the reactors.

http://www.nei.org/newsandevents/inf...n-that-region/

They also have an FAQ about radiation here.

http://www.nei.org/newsandevents/inf...in-perspective

[PUNKPRINCESS]

We actually do not know for a fact that no harm is done. There must be a certain number of people (be it ever so small) for whom just one CT scan happens to cause damage that results in cancer. The benefits of CT scans, in general, outweigh the risks, but fewer are better, and none is the best. Ironically, cancer patients are often given multiple CT scans over relatively short periods of time. Choose your poison.

Yes. Thank you.

This is why I at individuals who want to declare, definitively, that "it's safe, it's saaaaaafe, you uneducated fools."

One of my profs compared the likelihood of gamma rays hitting an atom in the body as something like an asteroid traveling through space and hitting a planet. The amount of empty space they can travel through is relatively huge, so the probability that they will hit anything meaningful is low. And yes, the body has a number of repair mechanisms as far as DNA damage goes, and multiple changes to specific genes have to occur, irreversibly, before a cancer develops. When you try to count the odds, it seems unlikely. Yet, we know that cancer is actually common, which makes sense when you consider that every second we are bombarded by millions of different processes that can cause deleterious changes in the body. I'm not exactly going to stop eating my barbecued meat, but since getting CT scans or X-rays taken aren't particularly fun, why do more than you have to. Even if you smoke a pack a day.

[GarrAarghHrumph]

I'm loving that we have our own "WTF does this all mean re: radiation" thread. FSU rocks. We do more analysis of the news than the news does!

What does this actually mean in real person speak?

From the BBC:

2333: More details on the reported blast at Fukushima's reactor 2. The explosion is feared to have damaged the reactor's pressure-suppression system, Kyodo says. It adds that "radiation tops legal limit" after the explosion.

[rfisher]

The "radiation tops legal limit" would mean the levels are higher than the maximum set by the ICRP. You'd have to know what that level is in order to assess the specific impact, keeping in mind the *legal limits* are set very much lower than the statistical thresholds for long term biological damage. So, if those levels persisted for weeks or months, it would be a problem.

[LadyNit]

NHK news now says that 400 milisieverts are detected around the reactor #1 in power plant#1. People are being told to stay indoors if they are within 30KM of plant #1 and to prevent air exchange between indoor systems and outdoor air.

[Anita18]

Yes. Thank you.

This is why I at individuals who want to declare, definitively, that "it's safe, it's saaaaaafe, you uneducated fools."

One of my profs compared the likelihood of gamma rays hitting an atom in the body as something like an asteroid traveling through space and hitting a planet. The amount of empty space they can travel through is relatively huge, so the probability that they will hit anything meaningful is low. And yes, the body has a number of repair mechanisms as far as DNA damage goes, and multiple changes to specific genes have to occur, irreversibly, before a cancer develops. When you try to count the odds, it seems unlikely. Yet, we know that cancer is actually common, which makes sense when you consider that every second we are bombarded by millions of different processes that can cause deleterious changes in the body. I'm not exactly going to stop eating my barbecued meat, but since getting CT scans or X-rays taken aren't particularly fun, why do more than you have to. Even if you smoke a pack a day.

Obviously, the very first thing someone should do to prevent cancer is STOP SMOKING.

And stay out of the sun. As a general rule, you'd want to prevent as much inflammation as possible, that's where cell damage occurs.

And thanks for emphasizing the number of DNA mechanisms. My lab does DNA repair and we have yet to really start delving into what the cell actually does when DNA breaks. It sounds simple but there's so many things going on, it literally makes no sense that someone could have designed this.

[numbers123]

The "radiation tops legal limit" would mean the levels are higher than the maximum set by the ICRP. You'd have to know what that level is in order to assess the specific impact, keeping in mind the *legal limits* are set very much lower than the statistical thresholds for long term biological damage. So, if those levels persisted for weeks or months, it would be a problem.

NHK news now says that 400 milisieverts are detected around the reactor #1 in power plant#1. People are being told to stay indoors if they are within 30KM of plant #1 and to prevent air exchange between indoor systems and outdoor air.

rfisher - what does the ladynit post mean?

[PUNKPRINCESS]

Nod to Anita.

[IceAlisa]

rfisher and other experts: my (former) dentist said that dental xray cause the same amount of radiation as your usual every day exposure to the elements. Is this true? Sounds strange.

Anita, staying out of the sun completely may lead to the depletion of vitamin D. Choose your poison. But yes, unequivocally, STOP SMOKING!!!!

It sounds simple but there's so many things going on, it literally makes no sense that someone could have designed this.

True, and yet one starts believing in the studying biology of cancer. Almost.

[aka_gerbil]

My lab does DNA repair and we have yet to really start delving into what the cell actually does when DNA breaks. It sounds simple but there's so many things going on, it literally makes no sense that someone could have designed this.

The lab I was in in grad school was not a DNA repair lab, but a few of my fellow labmates worked on some stuff with the NHEJ pathway (trying to downregulate several components). I was always so glad that my project was in a completely different area.

I've come away with biology/genetics with a different view. I look at some of this stuff and think it all arising by chance is as likely as a tornado blowing through a scrap yard and the result being a shiny Boeing 757 airplane.

At any rate, there is just so much we don't know about so many things when it comes to cancer, DNA repair, checkpoints, apoptosis, etc. Although, reading, it feels like everything always somehow goes back to p53.

ETA: Just to complicate things, and throwing this out there, I worked on the inflammatory response some. And while it can cause a lot of cellular damage, you don't always want to avoid it because it is sometimes necessary for efficient handling of pathogens that could cause even more illness/damage.

The more I type, the more I realize we really have no idea what's going to kill people or not.

[/geek talk]

[IceAlisa]

^^^^luuurves geek talk!

[Anita18]

The lab I was in in grad school was not a DNA repair lab, but a few of my fellow labmates worked on some stuff with the NHEJ pathway (trying to downregulate several components). I was always so glad that my project was in a completely different area.

I've come away with biology/genetics with a different view. I look at some of this stuff and think it all arising by chance is as likely as a tornado blowing through a scrap yard and the result being a shiny Boeing 757 airplane.

At any rate, there is just so much we don't know about so many things when it comes to cancer, DNA repair, checkpoints, apoptosis, etc. Although, reading, it feels like everything always somehow goes back to p53.

ETA: Just to complicate things, and throwing this out there, I worked on the inflammatory response some. And while it can cause a lot of cellular damage, you don't always want to avoid it because it is sometimes necessary for efficient handling of pathogens that could cause even more illness/damage.

The more I type, the more I realize we really have no idea what's going to kill people or not.

[/geek talk]

NHEJ! That's totally what we do! And yeah, it really is like a tornado blowing through a scrap yard and resulting in a shiny new Boeing. I might have to use that analogy sometime.

You're right, the body definitely developed the inflammation response for a reason. It's just that when it's chronic inflammation (lots of sunburns, smoking habit), that it's bad. Too much of anything is bad, pretty much.

[Anita18]

Oh, I see you meant that some of it had to be designed. I'm actually of the opposite view, but it's not "chance," really. Just "this thing worked and so we're gonna go with it!"

[MichaelK]

sorry - wrong thread

[MichaelK]

rfisher and other experts: my (former) dentist said that dental xray cause the same amount of radiation as your usual every day exposure to the elements. Is this true? Sounds strange.

If your dentist uses a modern X-ray device and it is properly administered the radiation exposure is indeed very small in a dental exam. The exposure is higher in a bigger exam like a thorax exam and significantly higher for CT - these should only be done if really necessary.

[rfisher]

rfisher and other experts: my (former) dentist said that dental xray cause the same amount of radiation as your usual every day exposure to the elements. Is this true? Sounds strange.

Anita, staying out of the sun completely may lead to the depletion of vitamin D. Choose your poison. But yes, unequivocally, STOP SMOKING!!!!
True, and yet one starts believing in the studying biology of cancer. Almost.

The exam yes. However, the dose is confined to a very small area. If you compared the lethal whole body dose to the allowed occupational dose for the lens of the eye, for example, the whole body dose is less because of the volume of exposed tissue.

There are many different factors that determine whether a specific radiation exposure will have some effect. Presence or absence of oxygen (oxygen is a radioenhancer), the specific part of the cell cycle of a targeted cell (G1 is most radioresistant, early S is radiosensitive, mitosis some where in between, the type of cell (short lived cells such as lymphocytes are more radiosensitive than neurological tissue), the age of the individual. The younger the organism, the greater the sensitivity. Stem cells are more sensitive than mature. The thing is, it's entirely random. There is no way to predict exactly what will happen, however, given all the biological data accumulated over the last 100 years, it's clear the overwhelming majority of radiation photons pass through without permanent damage. The radiolysis of water is the most likely event to occur. In most instances the electron removed from the hydrogen will immediately rejoin the atom. It is possible that if two molecules are struck in close proximity, the hydrogen and OH can form free radicals. They will react very fast and usually reform water but can form hydrogen peroxide. This are indirect effects.

Radiation carcinogenesis is indistinguishable from non radiation cancers and is entirely dependent on dose and how that does is delivered. A large dose delivered at once is much more damaging than fractionating that dose over time. This is what is done in radiation oncology. We can deliver a dose of radiation that if given as a whole body exposure would possible kill the patient, but given over a period of time allows recovery.

The situation in Japan seems to be getting out of the engineer's control. It simply remains to be seen what happens and how big a health risk this becomes. There are many different factors that can determine what happens. Sadly, there's nothing anybody can do except deal with it. If people are exposed, they're exposed. Most won't know the full impact until years from now.

[aka_gerbil]

NHEJ! That's totally what we do! And yeah, it really is like a tornado blowing through a scrap yard and resulting in a shiny new Boeing. I might have to use that analogy sometime.

You're right, the body definitely developed the inflammation response for a reason. It's just that when it's chronic inflammation (lots of sunburns, smoking habit), that it's bad. Too much of anything is bad, pretty much.

A professor we consulted with for a good chunk of my dissertation research put it best; when it comes to biological functions, for the most part, you want things somewhere in the middle. Not enough of a response and too much of a response are usually what causes trouble. Not enough of a response, you're body can't fight an infection, etc. Too much, you end up with damage. I worked on inflammatory response in the GI tract. Too much of a response there leads to permanent damage, which can lead to malabsoprtion and nutrition problems. On the otherhand, if you don't get enough of a controlled response, it may possibly be detrimental in fully priming the immune system in the GI tract. On a related note, I completely agree that inflammation from smoking and sunburn aren't so muchly so beneficial.

Oh, I see you meant that some of it had to be designed. I'm actually of the opposite view, but it's not "chance," really. Just "this thing worked and so we're gonna go with it!"

I'm a Methodist who believes in The Big Bang and evolution, if that tells you anything. More or less, I believe in some divine imput/design, but also the ability for things to adapt and change (and the Earth is totally more than 6000 years old).