Asymmetrical Information

Depends on whether it was an air bust or a ground burst as well as the basic "cleanness" of the weapon, its power and the definition of kill zone.

However having given the vague answer - averagely messy low power airbursts such as Hiroshima and Nagasaki had people moving back some 5 years later. It seems likely that in the best case of a really "clean" airburst you'd need just 1-2 years before half lives have reduced most radiation to about the same as that received in a concorde flight. Contrariwise a messy groundburst in granite(? I think) could easily produce a place that is highly radioactive for a century or more.

Why? are you planning on blowing somewhere up?

Depends on your standards for acceptable radiation. Also radiation is not so much reduced by radioactive decay but by dispersal of the radioactive stuff.

Based on the prior two posts, I surmise that as part of some experiment to test intelligent design or a theory of evolution, Jane plans to detonate an improvised nuclear device at a campsite in the tri-state area (after a romantic dinner by firelight). A complex one that Jane is.

MB

I'm guessing it has to do with Mecca and Medina.

It depends what you mean by liveable. For example in Beneath the Plante of the Apes, NYC had been hit by a nuclear bomb and was techincally liveable, as irridated people lived in Grand Central Station. Is that really living though?

I'd run with the historical points. Japan is a great place to start, but check with the Ukraine as well. Is anyone moving back into the area around Chernobyl? That's been close to 20 years now, and I think it's still considered dangerous.

There is published data on this stuff, but is all based on modeling as you might expect. The safe bet, if someone pops a nuke, is to plan for a lot of unpleasant surprises in addition to the foreseeable unpleasantness.

Chernobyl was contaminated by a hot fission reactor fire, though --- different radionuclides. People were visiting the Trinity site within a few hours or days; and back in the fallout shelter days, they taught us the 'seven hour rule', that the dose rate falls by half every seven hours.

The Wikipedia entry looks pretty good.

Here's FAS's Resources page.

Here's the Nuclear Weapons FAQ.

And this is a Google search that gave some nice other resources.

I personnaly would get a chuckle out of the triple-eyed fish and freaky little goat-boys. But I'm a sick one.

On another note: Chernobyl is still considered unlivable (even by Post-Soviet standards) and radioactively dirty, but getting better. That wasn't even a nuclear detonation, rather more akin to a really big dirty bomb (food for thought on the terrorism angle). One would have to imagine that if one of the really big megaton warheads of the Cold War era detonated in a major city the fallout would be big and longlasting. Pulverized concrete dust probably stays radioactive for a good long while.

Not really my area of expertise, but when did that ever stop me? :)

Francis' post seems to have hit the nail on the head. Modern hydrogen bombs, AFAIK, use trans-uranics only for the detonation and the vast majority of the energy released is from relatively clean fusion. If it was an airburst, most of the original radioactive material and trasmuted material would be dispersed over a fairly large area and the more radioactive elements also have the shortest 1/2 lives.

Again...it depends on what you mean by liveable. Radiation models for humans seem to be still very variable and in their infancy. From memory, 350 REM/yr is believed to be the point at which 50% of the population would die. Here's a site from the EPA guaging acute radiation exposure http://www.epa.gov/radiation/understand/health_effects.htm
However, that's only death from acute exposure and doesn't include long term effects, which are very fuzzy.

Oh...and here's an online book "Nuclear War Survival Skils" which has gobs of stuff in it about nuclear blasts, radiation, et al. http://www.oism.org/nwss/

Hope that helps, at least somewhat, answer your question.

All you need is a hat or a ploughed field

Kevin - You probably have this already:

http://www.archive.org/details/DuckandC1951

If you're a cockroach, and the blast doesn't kill you, hell, you'll rule the roost immediately!

First, some background. There are several different sources of radioactive fallout from nuclear weapons. The most direct source is unreacted components of the bomb itself, such as Uranium-235, Plutonium-235, Tritium, etc. These are a health risk but on a very low scale, they don't even fit on the scale of other fallout risks. Following that, there are the byproducts of nuclear fission. These are the most dangerous, including such fun little friends as Iodine-131 and Strontium-90, both highly radioactive, both readily absorbed by the human body. These byproducts are the same bad boys behind the death and destruction of the Chernobyl accident. Except, bombs carry only a few kg of fissionables and thus generate only a fraction of a kg of these most dangerous fallout isotopes, whereas reactors contain tonnes of fuel (and, as with Chernobyl, if incompetently designed and operated can generate correspondingly larger amounts of fallout). Then you've got fusion byproducts (in thermonuclear weapons). Which tend to be both fairly mobile and fairly mildly radioactive in comparison. The biggest danger here is Tritium, which is consumed fairly thoroughly during fusion reactions and isn't anywhere near Sr-90 or I-131 in terms of health concerns. Finally, there is fallout generated from in situ materials through neutron activation. This is the same mechanism that turns the support materials of fission reactors radioactive over time, only much faster. Essentially, neutrons from the bomb (or reactor) transmute some fraction of elements they encounter, and some fraction of the transmuted products can be radioactive. This is a complicated process and dependent on a lot of details of the bomb and the nearby environment. As a general rule of thumb, the heavier the elements in the surrounding area are the more likely they are to be activated by neutron flux, also, of course, the closer the bomb detonation is to said materials, the more activated fallout will be generated. Thus, an air burst over water would be pretty clean in terms of activation fallout, but a ground or underground burst in granite or steel or such-like would be very dirty.

Also, someone commented above that most bombs today gain almost all of their yield via fusion. This is not the case. Most of the most modern bombs are very efficient, low mass designs that are much smaller than the monster Hydrogen bombs of yesteryear. The most common weapon in the US arsenal, for example, is the W-88. A 475 kiloton yield, staged detonation thermonuclear warhead which derives only perhaps half of its yield from fusion. This is because most modern weapons are fission-fusion-fission, and take advantage of radiation implosion (aka "Teller-Ulam") designs to gain incredible efficiency in the detonation of the 2nd / 3rd stage fission components (typically these are integrated as the casing and "spark plug" of the fusion fuel capsule). That being said, their mere efficiency alone makes them substantially "cleaner" than the classic fission designs.

Long story short, if you're talking J. Average Modern-Nuclear-Warhead, then you're talking about something near a half MT thermonuclear device which will be detonated in an air burst over the target (actually, several of them spread out over the target). Under those circumstances, I wouldn't expect the fallout danger to last significantly longer than for, say, Hiroshima or Nagasaki, and I would fully expect people could come back and live in the area within a few years. In terms of other scenarios, I'd say that it would be pretty unusual to have a combination of circumstances which could produce enough fallout to keep an area uninhabitable longer than a few decades (if that). However, it is fully possible for someone to manufacture a nuclear device purpose built to maximize fallout (e.g. a "Cobolt bomb"), but these generate more quantities of hazardous radioisotopes and don't necessarily increase the time period a specific area would be uninhabitable.

In shorter short, the only way to produce a Chernobyl style, long-lived radioactive no-man's-land would be to bring to the table the tonnes of fissionables needed to generate such large amounts of fallout. It's also possible to create purpose built devices to do precisely this (e.g. unshielded fission reactors designed to catch on fire at the appropriate moment) but they would weigh tonnes and would require special delivery mechanisms.

Robin mentions neutron activation of surrounding material. If you're talking about a nuclear attack against a city, most of the common atoms in those areas which might absorb one neutron would not be rendered radioactive.

Ni15 is stable. C13 is stable. O17 and O18 are stable. H2 is stable. Si29 and Si30 are stable.

Half-lives of the most likely radioactive isotopes created by absorbing one neutron:

Sodium 24: 15 hours
Aluminum 28: 2.3 hours
Silicon 31: 2.62 hours
Phosphorus 32: 14.3 days
Sulphur 35: 86.7 days
Chlorine 36: 300,000 years
Chlorine 38: 37.3 minutes
Potassium 42: 12.4 hours
Calcium 45: 165 days

Those are all beta sources. However, none of those will show up in very great quantities because their precursors (one atomic number down) are all relatively small percentages of naturally occurring atoms.

Where I think you'd really worry about created fallout products would be if there was an iodine processing plant or a cobalt refinery at ground zero. Then you really got to worry.

But most of the isotopes I listed above would burn off in fairly short order, and most of them would be rare anyway (between poor neutron cross sections and relative lack of abundance of feedstock isotopes to be activated).

[Keep in mind that radioactive decay is inverse-exponential. After 3 half-lives you're down to 1/8th of the original quantity. After 10 half-lives you're at 0.1%. After 20 half-lives less than one millionth of the original quantity remains.]

Don't forget hormesis

http://www.angelfire.com/mo/radioadaptive/anniv2.html

You've probably seen this before, but just in case, here's a set of photoessays by woman who rides her motorcycle through the area around Chernobyl.

As the other responses point out, the question is what kind of nuclear bomb, and detonated where?

Air-burst will in all cases minimize long-term radiation, ground burst will create somewhat more. Sea bursts may maximize fallout, because of the relatively high proportions of chlorine and sodium.

The more efficient a fission bomb is, the less fallout it will produce; much of the Hiroshima and Nagasaki fallout was uranium and plutonium that didn't get consumed by the device. A hydrogen bomb, between the fissile "sparkplug" and the uranium casing, will produce more fallout per bomb than a fission weapon. A neutron bomb will produce somewhat less fallout, because it uses nuetron-transparent nickel instead of materials relatively easy to activate as the X-ray reflectors and casing. All really will be on the scale of Hiroshima and Nagasaki for post-detonation livability.

A cobalt bomb, however . . . . The idea with salted bombs is that you replace the U-238 shell in a hydrogen bomb with a material, like Co-59, which will then be bombarded by neutrons from the detonation and turn into a deadly pollutant. As Co-60 is a gamma emitter with a 5-year half-life, a cobalt bomb will work quite effectively as long-term irradiator. Zn-64 and Ta-181, which would produce Zn-65 (half life of 8 months) and Ta-182 (half-life of 4 months), would be shorter-term versions of the salted bomb. However, it is not believed anyone, anywhere, has actually built or tested an enhanced-fallout design.

The real question isn't when the area would actually be safe, but when people would stop getting hysterical over tiny traces of radiation and be willing to move back in. (Or when government agencies would stop being hysterical and allow people to move back. Note that it's never going to be radiation free - there was natural radiation before the bomb.

I'm not sure the early 1950's examples (Hiroshima, Bikini Atoll, etc.) are relevant because they really had no idea what they were dealing with in terms of long term effects of low radiation levels back then. But the trouble is, we still don't know that to any precision, we just err in the opposite direction. (Did anyone do long-term studies of people who moved to Hiroshima and Nagasaki afterwards?)

The DOE sets exposure limits based on the linear assumption (that 1 millionth the dose would have 1 millionth the effect), which is almost certainly wrong. It implies that there is no completely safe dose, which seems unlikely since we evolved to live in a world with some natural background radiation. It would be true if cancer was generally caused by a single genetic mutation, but more recent research has shown that a number of different things have to go wrong in a single cell's DNA before it becomes malignant. It's probable that there is an optimum level of radioactivity. However, politics has more to do with DOE policy than science, and the politics of radioactivity is driven by "environmentalist" [1]fanatics stirring up hysterical fear among the scientifically ignorant, which is most of the population because public schools do a terrible job of teaching science.

[1] Those scare quotes are because the so-called environmental movement advocates several policies that are actually bad for the environment - mindless opposition to nuclear power being a prime example.

markm's point is well taken... A few years ago, at least, when I was working in the field (haven't researched to see if still true), there were pollutants in groundwater whose maximum acceptable levels (depending on the state) were AT the lower limit of lab detection, not because there were actual data to indicate an enhanced human cancer risk at those levels, for instance, but because God forbid you should discover that you have x in your groundwater.

Usually, if you have a good can of air freshener and a really good vacuum cleaner you can move right into the zone after ten minutes or so.

Gawd, what sort of question is this? Jane you really have to tell your new Saudi boyfriend to stop asking questions of you like this. And if he tries to tell you he was just trying to get the microwave setting to heat up his hot pocket, that is soooo not true.

(Just kidding).

The photos at that Chernobyl site are great, but I think that the motorcycle story was exposed as a hoax.

Zbigniew Jaworowski is a professor at the Central Laboratory for Radiological Protection in Warsaw, Poland, and is a former chairman of the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAN).
Writing in Physics Today, Jaworowski says that the 1986–95 average radiation doses from the Chernobyl fallout ranged between 6 and 60 mSv and the projected average individual lifetime dose in the Chernobyl-contaminated region is 210 mSv.

By comparison, the average individual lifetime radiation dose due to natural background radiation, in many regions of the world, is 5 times higher (about 1000 mSv), and "no adverse genetic, carcinogenic, or other malign effects of those higher doses have ever been observed among the people, animals, and plants that have lived in those parts since time immemorial."
He also says that "survivors of the atomic bombing of Hiroshima and Nagasaki who received instantaneous radiation doses of less than 200 mSv have not suffered significant induction of cancers. And so far, after 50 years of study, the progeny of survivors who were exposed to much higher, near-lethal doses have not developed adverse genetic effects."

Consequently, Jaworowski believes that the evacuation and relocation of a quarter of a million people from the Chernobyl region was entirely unnecessary -- an hysterical overreaction to an imaginary danger.

Among the commentators here, Deak says that "Chernobyl is still considered unlivable," Half Canadian says that it's "still considered dangerous," and Robin Goodfellow refers to Chernobyl as a "long-lived radioactive no-man's-land."
Jaworowski says they're wrong, and would apparently agree with commentator Markm who says that the real question is "when people would stop getting hysterical over tiny traces of radiation and be willing to move back in. Or when government agencies would stop being hysterical and allow people to move back."

I'm no expert on the subject and am not qualified to judge the argument, but Professor Jaworowski's article is thought provoking.

Not surprisingly, the health effects of the Chernobyl explosion have been wildly exaggerated.
Some say it killed 50,000 people. 50 is more like it.

Check this essay: http://www.uic.com.au/nip22.htm

Bear in mind that the unit that blew up was one of five in the complex. The other four continued to run for years, supplying half the Ukraine's power, and staffed by 6,000-8,000 employees working a stone's throw from the disabled reactor. Sure, the ground around the plant is polluted with radio-isotopes, as is the ground around the neighboring town. So don't eat the dirt (like you would have?).

Someone asked whether anyone had followed the health impacts of Hiroshima and Nagasaki. Well, yes. It is one of the largest and most extensive population health studies ever conducted, with a study group of over 300,000 individuals. The study is on-going.

Various preliminary reports have been used to calibrate human health impact standards for radiation.

Those really interested might like to refer to "Effects of Atomic Radiation -- A Half Century of Studies From Hiroshima and Nagasaki" by William J. Schull. Schull spent the better part of his lengthy career on this topic.

Bottom line: If you didn't die of bomb effects in the first ten days, you probably weren't going to die of those effects at all.

The biggest correlation between radiation and carcinogenesis involves a certain type of normally rare leukemia. In a population the size of the study group, you'd expect about 600-odd cases. In actuality, they found a little over 900 cases, a 50% increase in risk for that type of cancer. While that may sound pretty daunting, you're still dealing with not more than a one in a thousand probability -- not the kind of casualty rate that should shift the tide of history.

Nagasaki and Hiroshima were re-inhabited very quickly -- pretty well as soon as infrastructure like the water system could be repaired. As Den Beste pointed out, the deadliest isotopes are deadly because they pound out a lot of radiation, but pounding out a lot of radiation also means that their half lives will be short -- minutes, hours or days. While there might be a few long-lived isotope that produce penetrating gamma rays (cobalt-60 or cesium-137), you normally wouldn't find much of those isotopes after a nuclear blast.

There's still "hot spot" of a couple of acres in Nagasaki right under where the bomb went off, so yes, some radiative elements can hang around for a long time. But note that this is couple of acres, not dozens of square miles.

One of the more hideous aspects of Hiroshima was that after the blast, the water system was wrecked so large numbers of survivors camped out next to the river than ran through town. A couple of weeks later, the biggest typhoon in 50 years drenched the region, drowning additional thousands. The river then ran with polluted muck, triggering an epidemic of cholera and typhus, killing thousands more. An absolute hell on earth.

IMHO, unsexy civil defense measures, aimed at mitigating the effects of terror attacks or other disasters, are at least as high a priority as Patriot-act policing measures or overseas military activities.

So CL36 has a half-life of 300,000 years. Another reason to oppose municipal chlorination of the water supply....

As others have pointed out, there's loads of hysteria about radiation.

Fall-out will kill, but not for very long. Hiding away for a few weeks in a bunker would be enough.

A boiler explosion of a nuclear reactor would do more to crap up the landscape then a nuclear bomb. For one thing the amount of fissionable material is higher. Have transuranics, cobalt-60 etc. Also, the material just sits there vice getting dispersed in the nuclear explosion. That said, it is possible to expensively decontaminate the area. SL-1 (US nuclear reactor explosion that killed 3 people) and Chernobyl are good things to research.

TCO: Not true. Commercial nuclear power plants are designed to include the prospect that the reactor pressure vessel (what you call a boiler) will fail and still cause no harm to the public. That's what the costly safety systems and containment structures are for. Blowing up the boiler, as you put it, would cause a hell of a mess on the floor of the reactor room, but not the surrounding community.

Remember too that our plants were designed to meet a safety standard that did not include evacuation the population in the plant vicinity. The TMI evacuation -- aimed at 5,000 people near the plant -- was answered by 450,000 people. The evacuation itself was ordered because ill-informed public officials wanted to look like they were 'doing something' even though nothing needed to be done that was not already being done.
And indeed, nothing happened besides wrecking the reactor: No one hurt, no one killed, not in the plant, not outside the plant. I wish the airline industry could say the same--or indeed any industry that entails heat, pressure or speed.

I am not a science student so i don't know the answere.But i enjoyed reading comments on you're posting.
Albert

RAF - they don't "chlorinate" resevoirs.

If your chlorinated water is hot after the blast, all you gotta do is run some fresh stuff into the system.

Seriously - I think you should up your meds is you think this is an issue.

Not to overstate the obvious here, but if the theme of this thread, and posters is that nuclear weapons are "no big deal", then:

A) What the heck was the hysteria about the Cold War about?

B) What the heck was the urgency about invading Iraq after "allegedly" trying to acquire nuclear weapons (the ultimate WMD)?

If I'm following these posts, the response to a nuclear attack in America would be to take temporary cover, sweep up the mess, bury the dead and pick up fresh milk on the way home from work.

Surely we're not skipping down this silly road, are we?

--Cobra

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