Sorta OT: radiation detection and identification questions

If radioactive material is enclosed in airtight shielding, it does not emit any isotope atoms that could be detected. On the other hand, it would emit radiation such as gamma rays or neutrons, which could be detected with suitable devices.

This dirty bomb talk is mostly Republican scare tactic electioneering ("we are working hard to protect you from dirty bombs"), as, in reality, the damage from a dirty bomb is of relatively minor nature. A truck full of any explosive, like ANFO, could cause many times more deaths than a dirty bomb. Damage from a dirty bomb mostly pertains to the cost of cleanup (again, likely less than the cost of a blown up high rise building).

Smuggling stuff is more difficult to detect because there are not bazillions of contaminated dust-particles being generated.

Uranium emits alpha particles, stopped by paper. Plutonium also emits gamma rays, easier to detect but I think the level is low. I believe neutrons are generated by both, and so the nuke detectors around DC (and elsewhere) are neutron detectors.

I believe range is quite short on all these.

Wanna have some fun? Build a portable farnsworth fusion device that'll fit in a van and drive around DC. You'll be a real popular guy in a very short amount of time!

(fusion is easy- break even self sustained fusion is what's tough)

Dave

I suspect, but don't know for certain, that what they detected were short-lived active radioisotopes that can only be formed in an atomic reaction.

Detect> Several days after North Korea set off an underground nuclear

While you are correct that the cost from a dirty bomb would be mostly cleanup, I would not consider strontium 90 or cesium contamination to be a "scare tactic", but rather something that would take much work to clean up.

Or do you want these things to stay in the environment and then into humans? How expensive is asbestos removal? What do you thing a dirty bomb attack cleanup would cost?

Or perhaps you are volunteer> Damage from a dirty bomb mostly pertains to

Exactly.

I think that the cost/benefit ratio from practically organizing a dirty bomb makes it not worth it.

Let's see.

First you have to obtain a good enough quantity of radioactive isotopes (not easy). For a powerful enough "dirty bomb" they would emit a lot of radiation.

So, they would be, first, difficult to handle without dying very early in the process. Second, they would be difficult to transport without heavy shielding. Third, they would be detectable.

To spread the isotopes of the dirty bomb would require a decent quantity of explosives (or else they will not spread sufficiently).

If terrorists already can get a decent quantity of explosives (see previous paragraph), it is a lot easier to just rent an apartment in a high rise, bring in explosives in shopping bags gradually and blow up the building, with a lot more deaths than a dirty bomb would ever cause.

The dirty bomb project's cost is millions of dollars, the explosives cost project is thousands of dollars.

Yes, it would be a bit hard to do without at least being detectable. If we happened to be monitoring the right spot at the right time, we would catch them trying to bring it in. As for availability, not such a big problem. There is a HELL of a lot of radioactive material in labs and production facilities all over the place. The countries we are worried about have their OWN reactors, producing TONS of radioactive waste.

Some terrorists have clearly shown little regard for their own lives.

After the plain bomb blows up the building, people are not scared to move about the city. After the dirty bomb, they all run away screaming! The whole idea is terror, if you add a new element, invisible "stuff" that can kill you, and you have a PERFECT terror recipe.

Jon

Not all that short. The Navy (I think) did a test to see if nuclear weapons could be detected outside a ship. They had a research vessel trail some guided missle cruisers and aircraft carriers. They were able to pick up either the Gamma or Neutron signature of Plutonium from distances of thousands of yards. I think it took a half-hour count or something like that for the signature to build up.

I believe this gear is already being fielded, probably by the coast guard.

Jon

I have a couple of radiation detectors that came from a '50s shelter. It looks like I'd better dust them off and get them working...I assume the Democrats will gain power and I'll need them.

Thanks Jon, Ig and everyone else who responded to my questions. I'm not real scared of radioactive bombs, nuclear or "dirty", but I am curious and concerned about detection and prevention. Right now we (meaning the USA gov't) are wasting money and time on checking airline passengers for liquid bomb making ingredients when a little research shows just how difficult it would be to make and set off the explosive on an airplane. But little cargo is being inspected for explosives, exotic or common, on airliners or ships. And since the ways radioactivity can be deadly are a mystery to most people it would be a good thing, in my opinion, for our government to educate all the residents of America about the real dangers. And what our government is doing to prevent even one incident. And what we can ourselves do such that we don't become, or remain, sheep. ERS

I tried mine briefly, it did not seem to work well. Mine is a yellow civil defense surplus.

This bomb was a flub really - it never went critical.

A dirty bomb is one that explodes with plastic TNT material and in the process it spreads the scrap radioactive junk all over the place.

Yes - if the scrap was hot - it would be.

This one was in that sense - but it was way below ground and was dampened. A dirty would be ground level and yes - almost any detector would work.

The chunks would be everywhere and would take time to be picked up and isolated.

Take a bucket of grass seed. Have it thrown up in the air and the wind catches it. Now pick up each - but remember you can hunt them down with detectors.

Martin [ Degree in Physics - at least ] Martin H. Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net NRA LOH & Endowment Member NRA Second Amendment Task Force Charter Founder IHMSA and NRA Metallic Silhouette maker & member

Eric R Snow wrote:

I got my duct tape, plastic sheeting and my radiation detector...I'm ready for the elections!

These "radiac test sets" use ionization chambers, and are useful only in pretty serious radiation conditions. They also require some batteries that have probably been unobtainable for 30 years, ie.

I managed to get a wrecked Geiger counter from work and rebuild it. It is pretty sensitive to the Alpha and Beta that it is designed for. Haven't had much use for it yet, thankfully.

Jon

Not really. They need enough radioactive materials to set of a few detectors and a few pounds of explosives. Then sit back and watch while several million people that should know better, wind themselves into knots worrying about where is next, not to mention how much the actual and residual losses to the economy will be.

The dirty bomb that causes the most havoc will not be one that poses much real risk of health complications or death, but the one that causes the most people to freak out worrying.

The fastest way to end up job hunting is to be a high level public official that says that there is nothing reasonable that can be done about something, even if it is the truth. Look at the continued effect that the 9-11 incident is having on world trade, air travel, and general feelings of unease in the populace, while things that perhaps should be changed continue on as they always have (just how many containers off any particular container ship actually ever get checked? for example).

There has been a pile of pain in the butt stuff put in place that makes air travel not fun anymore, that has mostly accomplished nothing. But it has cost the economy a pile.

Cheers Trevor Jones

On the subject of cargo inspections... Why would a device have to be brought into the country at all? A device in a sea can on a boat in the harbour is as effective a way to cause chaos as any. So much the better for the perps if the wind is blowing inshore.

Cheers Trevor Jones

If it didn't go critical, then it wouldn't have produced the characteristic fission daughter products that our people are looking for. And, they are sophisticated, such that the specific isotopes tell them whether it was a U235 or Pu239 device, whether there was any thermonuclear booster on it (not this time), etc.

As I understand it, there is some minimum critical mass, depending on the intensity of the chemical implosion. Advanced implosion devices reach a density of the fissile material very roughly twice the normal mettalic density. That allows you to use a critical mass quite a bit less than the normal critical mass of uncompressed Uranium or Plutonium. Our Hiroshima bomb "little boy" operated at normal density, and it probably is still secret what level of compression the Nagasaki bomb "fat man" produced. If you don't achieve the critical mass by compressing the fissile material to the level required by the design (and I'm assuming the N.Korean device was implosion-type) then the neutrons delivered by the trigger do not multiply very much in the short time of high density, which only lasts microseconds. If the mass goes above critical, the whole nuclear reaction completes within a microsecond or so. I'm no expert on this, but my understanding is there is a VERY thin line between a pretty complete reaction and essentially no nuclear reaction at all (in implosion-type devices, specifically.) And, if there's no reaction, then the air sampling won't pick up those daughter products they are looking for.

One possible way to trick the investigators is to set off a dirty bomb loaded with very fresh reactor fuel elements. Even so, I think the mixture of daughter products would have a very different percentage in reactor fuel than a weapon detonation, since some of the reactor products would have decayed to secondary etc. daughters.

Oh, well, that leaves me with a conundrum. If the thing can either go BOOM or burp, how do we explain the half-boom? One theory, which others in the non-proliferation area have also alluded to, is that N. Korea was trying to save their precious Plutonium, and not use a "full load" in this test. Well, if you don't put enough fissile material into the device, can you EVEN TELL if it would have gone critical if it DID have a full load? My understanding of critical mass is that it would be really hard to get good diagnostic info if it doesn't have enough material to form a critical mass. If you put half of the required plutonium into the thing, you won't get 1/2 yield, you'll get a few thousand neutrons, maybe. Mabe some good neutron detectors close to the device, and recording gear far enough away to survive the blast would do. But, that doesn't explain the radioactive isotopes the samplers found.

So, that might point to some kind of a flub, but one that DID go critical, just not very well past critical, or didn't stay critical for long enough. Or, another option, that the N. Koreans have worked very hard on the smallest possible device, to make sure their crummy missiles can loft the thing. Maybe they used insufficient chemical explosive to get the full density, and just barely crossed the critical line for an instant. But, it is something they know their missile can lift. What is the smallest critical mass achievable? We certainly had, and may still have, battlefield nukes that can be delivered by artillery. What is the yield of those devices? They can't weigh more than a couple hundred pounds.

Jon

My own guess is that the North Koreans used gun type of design, which is very inefficient and can produce very incomplete fission.

A dirty bomb is quick to make, and is a marvelous terror weapon. Even moderate levels of radioactive material powdered and blown into the sky with an explosive charge..would kill thousands in a large city. Not from the rads..but from the panic.

No matter how much the Government tells the public they are safe if they simply stay inside......they will run like a herd of cattle out of the area..and thousands will quite frankly..die in the panic.

It will not only shut down the immediate area..but everything downwind for miles. Economic chaos.

When an explosive device goes off..there is a finite amount of damage. People can see and walk around the chunks. With a rad attack..the worry and panic ..the Unseen Boogy Man will take over.

Most reading this are logical and analytical types..the Public at large is NOT.

Gunner

Rule #35 "That which does not kill you, has made a huge tactical error"

Indeed. Ive pulled out all my Civil Defense detectors and replaced the batteries again.

Sadly..when we all start walking around with Dosimeters in our pockets and a cumulative dose chart in our wallets...we will know for sure Democrats control Congress.

Gunner

Rule #35 "That which does not kill you, has made a huge tactical error"