Ludwik Posted April 2, 2011 Posted April 2, 2011 How harmful is nuclear radiation? It depends on the dose/density received. Tsunami-related Fukushina accident will probably renew debates about nuclear electricity. Such debates should be based on what is known about negative effects of nuclear radiation. Numerical data below should be useful in that context. The effect of penetrating radiation on a person depends on the dose density received. The common unit of dose density is Sievert (Sv). Smaller doses are expressed in milliseverts (mSv) or microseveret. The old unit of dose density, rem, is also used widely (1Sv=100 rem) A dose density of 10 Sv will most likely results in death, within a day or two. 5 Sv would kill about 50% of exposed people. 2 Sv can also be fatal, especially without prompt treatment. 0.25 Sv = 250 mSv is the limit for emergency workers in life-saving operations. 0.10 Sv = 100 mSv dose is clearly linked to later cancer risks. 0.05 Sv = 50 mSv is the yearly limit for radiation workers. 0.004 Sv= 4 mSv typical yearly dose due to natural radiation (cosmic rays, etc). 0.003 Sv= 3 mSV typical dose from mammogram The one day dose densities, due to Fukushima accident, at a distance of 30 miles from the damaged reactors, was reported (on 3/16 and 3/17) as 0.0036 mSv. I do not have data on doses, probably very large, received by those who worked near or inside reactors. But I have no doubt that each of them was carrying an individual dosimeter. No deaths due to radiation have been reported in Japan, as far as I know. Many lives, however, were lost in Chernobyl, by those who worked to minimize damage. P.S. What I call dose density is often called a dose. But this is not correct. Sv=J/kg is dose density; the dose (how much energy absorbed in a body) should be in Joules. Ludwik Kowalski Professor Emeritus Montclair State University, USA . .
mooeypoo Posted April 3, 2011 Posted April 3, 2011 Great breakdown, thanks! I am wondering, by the way, about the incident in japan. In the case of actual nuclear weaponary, the explosion creates a "shower" of radioactive particles "fallout". In this case, however, there was no real explosion, but there is radiation. If I understand correctly, radiation will not usually create radioactive particles in the air (I might be wrong, I am not sure). My question is twofold, then: 1. Is there a risk for any sort of fallout in that area, or is the risk strictly localized, so when and if this nuclear core is sealed (I think they're beginning to seal it now with sand and cement) and the radiation leak is stopped, the radiation risk in general to the area is done completely? Or will this be a sort of "Chernobil" area again, where people cannot return to live there for a few decades? 2. Why is the news and experts that I read in media talk about the wind direction if we're not talking about particles? Radiation is electromagnetic waves, right? What effect does the wind have on any of this? I think this was posted before on the forum, but I thought it was a nice visual way to see a comparison of radiation doses (or rather dose density). Thanks, of course, to the brilliant XKCD. Click here to see it, it's worth it. ~mooey
Cap'n Refsmmat Posted April 3, 2011 Posted April 3, 2011 There've been leaks of radioactive particles, such as iodine-131 and radioactive steam, from the reactor containment building. Hence the concern about wind direction.
swansont Posted April 3, 2011 Posted April 3, 2011 I read a critique of the xkcd dose chart; though the numbers are good it does not distinguish between acute and chronic doses. Getting a given dose in a day is very different from getting that same dose spread out over weeks or months. Giving the body a chance to repair itself is very important. Ludwik mentioned a yearly limit for radiation workers, but they have quarterly limits as well, to help ensure that the dose is not received all at once.
Kikis Posted April 4, 2011 Posted April 4, 2011 Dear Sir I have a question, are people who have been exposed to nuclear radiation transmitting it to others?
swansont Posted April 4, 2011 Posted April 4, 2011 Dear Sir I have a question, are people who have been exposed to nuclear radiation transmitting it to others? No. Exposure, with some specific exceptions, does not make you radioactive. Once the energy has been deposited and damaged a cell, that's it. (The exceptions are exposure to neutron radiation, which can be absorbed and create radioactive isotopes, and some (uncommon) gamma absorptions which kick out a neutron or proton, which can also produce radioactive isotopes) If you have been contaminated, i.e. you have radioactive particles (or particulates containing them) on or in you, then the radiation from that can either harm you or someone else, depending on where it goes. If the daughter of a decay is also radioactive, then it can continue to be a problem. But since dose depends on distance, it's generally much more of a problem for the contaminated person. There is a danger of spreading contamination, in large part because external exposure can turn into internal exposure, e.g. a speck of radioactive alpha-decaying material on your hand, which presents little danger by itself, transfers to a donut and you eat it — that's a much, much bigger problem.
niebieskieucho Posted April 4, 2011 Posted April 4, 2011 How harmful is nuclear radiation? It depends on the dose/density received. The most dangerous radiation pollution by Fukushima power plant seems to be water. As it appears from the article http://swns.com/fukushima-radiation-detected-in-uk-291410.html it's estimated at 100,000 times its normal level. Thou, Japanese fishermen should be checking safety degree of radioactive fish before they land on their plates.
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