Touching weps grade uranium/plutonium

Pengwuino

What would the timetable be for health for a person who touches with their bare hands, weapons grade nuclear material. Theres this stupid movie on and this guy was holding material for his "home made nuclear bomb" and im thinken.. come ooooon.

Astronuc

The pits are warm to the touch.

I know some folks who dismantle nuclear warheads. Obviously, one tries to minimize exposure.

It would be quite simple to take a representative mass, e.g. 10 kgs of both Pu and U, and use the decay constants to figure out the activity, and from that the dose. The activity then gives one a distributed energy source with which one can determine the heat flux. With the appropriate surface heat transfer coefficient, one can determine a reasonable approximation of the pit surface temperature.

Morbius

Pengwuino,

If you are talking about handling pure Plutonium-239; there would be
ZERO effect. Pu-239 decays by emitting a 5.245 MeV alpha particle.

Because alpha particles have a charge of +2 [ they are doubly ionized
helium nuclei ]; they interact very strongly with matter and lose their
energy very quickly - hence they have a very short range. The range is
so short, that the alpha particle will not even penetrate the dead layer
of skin that surrounds your body. Therefore, the radiation from the
Plutonium doesn't interact with live tissue - therefore, the health effect
is zero.

In fact, when Russian scientists had assembled the Plutonium core for
"Joe I"; the first Russian nuclear test which was their copy of Trinity;
the Russian scientists presented the core of the device to Joseph Stalin,
and he held it in his hands and commented about it being warm to the
touch.

It's not good practice to handle radioactive material in that manner -
at least one should wear latex gloves. In one of her, "Behind Closed Doors"
programs, Joan Lunden went to Los Alamos where she handled a ball of
Plutonium while wearing latex gloves. The ball was also coated in a
thin layer of stainless steel to protect the surface.

If you are talking about weapons grade uranium, again the risk is zero.
Weapons grade uranium is mostly Uranium-235, which has a half-life of
703.8 million years! Since the radioactivity is inversely proportional
to the half-life, and Plutonium-239 has a half-life of 24,110 years ;
Uranium-235 is 29,191 times LESS radioactive, atom per atom; as is
Pu-239.

When you see movies where Plutonium and Uranium [ even weapons
grade ] are protrayed as this stuff that glows green and will give you
deadly radiation sickness if you get anywhere near it - then you know
you are watching a movie by someone that is absolutely CLUELESS
about nuclear technology and radioactive materials.

Dr. Gregory Greenman
Physicist

russ_watters

Morbius, I was under the impression that Pu is one of the most radiologically toxic substances on earth. Is it only if you inhale it?

Morbius

Russ,

The fact that the alpha particles have a high LET - Linear Energy Transfer -
which means they lose a lot of energy per unit distance is a double-edged
sword.

If the alpha emitter is external - it means that the alpha particles can't
get in - they can't get through the dead layer of skin.

However, if you ingest or inhale the alpha emitter - then you've "solved"
the problem of getting into the body for the alpha emitter.

The alpha particle in that case is now IN the body right next to living
tissue. Now the fact that the alphas have a high LET means that they
deposit their energy in a very short track - hence they do a lot of
damage - which accounts for the high radiological toxicity.

The dose is a measure of energy deposited per unit mass of material.
The original unit - the rad - is 100 ergs per gram. The SI unit is the
Gray which equals 1 Joule per kilogram = 100 rads.

The "dose equivalent" takes into account that different forms of
radiation have larger or lesser effects. So the dose is multiplied by
a "Quality Factor" to give the "dose equivalent. The "Quality Factor"
for photons [ gamma and X-rays ] is one. The Quality Factor for alphas
is 20.

When you multiply "rads" by a quality factor, you get a dose equivalent
in "rems" [ rads equivalent man ]. For the SI units, when you multiply
a dose in Grays by a Quality Factor - you get a dose equivalent in a unit
called the Sievert.

So, an alpha emitter like Plutonium OUTSIDE the body - is not to worry.

An alpha emitter INSIDE the body is going to do a lot of damage.

Courtesy of the University of Michigan:

http://www.umich.edu/%7Eradinfo/intr...properties.htm

http://users.rcn.com/jkimball.ma.ult...Radiation.html

Dr. Gregory Greenman
Physicist

Pengwuino

So whats the danger in a 'dirty bomb' if touching this stuff is not so dangerous?

russ_watters

Theoretically a "dirty bomb" does oxidize or aeresolize it, so you can breathe it. However, the reality of the dirty-bomb threat is somewhat overblown. Most media reporting on the subject seems to operate under the all-radioactivity-is-equally-bad misconception. But composition and method of dispersion matters.

Next question for Morbius: I know uranium is somewhat volatile - I thought Pu would just about spontaneously combust in air at room temp...?

Astronuc

Both uranium and plutonium are pyrophoric when finely divided, as in powder, or shavings, e.g. from a machining operation. The solid material should not be a problem unless there is a good source of oxygen.

Regarding spontaneous combustion, IIRC Pu still needs a flame source.

Morbius

Penguino,

You are confusing two very different concepts - and types of weapons.

A so-called "dirty bomb"; or RDD - Radiological Dispersion Device - doesn't
use "weapons grade" material!

An RDD uses highly radioactive material bundled with explosives. When
the explosive explodes, it disperses highly radioactive material - material
that emits gamma radiation, around.

Gamma radiation, which is electromagnetic radiation - photons - like
X-rays, except even more powerful and energetic; will NOT stop at the skin.
Gamma radiation is highly penetrating.

So a "dirty bomb" disperses this highly radioactive material around - so
that it maximizes the number of people that are exposed to it.

Weapons grade material, on the other hand, like Uranium and Plutonium
is not very radioactive at all - only very slightly - and as I've stated, the
type of radioactivity from Uranium and Plutonium is very easily shielded;
a piece of paper, or the dead layer of skin on your body will do.

Although Uranium and Plutonium are not very radioactive, they are
"fissile" - that is they readily undergo the nuclear fission reaction. If one
arranges a device such that one can, on command, assemble this weapons
grade material into a "prompt supercritical" configuration - and add a
neutron source - the result will be a rapidly growing uncontrolled chain
reaction of nuclear fission - thus releasing tremendous amounts of
energy. Such a device is a nuclear weapon.

So you have two VERY DIFFERENT animals here. Weapons grade material
can be made into a nuclear weapon - but it is pretty useless for the
"dirty bomb" that you are talking about.

Dr. Gregory Greenman
Physicist

Morbius

Russ,

Yes - Plutonium is "pyrophoric" - that is it can spontaneously combust in
air at room temp. It does that if you have a fine powder - with lots of
surface area per unit volume. Therefore, when the surface oxidizes - and
releases heat - you can start combustion. It's not really "spontaneous" -
you need a triggering event - but something like the heat of friction,
should the powder become "sandwhiched" between two moving surfaces -
will trigger the combustion.

However, if you have a big ball of Plutonium - the surface will oxidize -
but the whole ball isn't going to catch fire.

Think of ordinary baking flour. You aren't concerned that the baking
flour sitting in the canister in your kitchen is suddenly going to explode.

However, a fine "mist" of airborne flour is very explosive - and you used
to hear a lot about grain elevators in the Midwest where flour was
stored in large quantities exploding. Here it was the flour "mist" that
was spontaneously combusting.

Dr. Gregory Greenman
Physicist

Pengwuino

@Morbius

I understand the different types of weapons but what I wasnt understanding is how i assumed you just had unrefined uranium in a dirty bomb... and its deadly as hell... but when its refined (which to my mind brings up 'concentrated' deadliness or what not), how is it all of a sudden not so deadly. Well actually no i dont understand now. What materials are used in hypothetical dirty bombs if not the same unprocessed uranium that eventually winds up as refined nuclear weapons material?

Morbius

Pengwuino,

First - uranium isn't "deadly as hell" - either in refined nor unrefined form.

I assume you understand that the radioactivity of an isotope is
INVERSELY proportional to the half-life - that is the shorter the half-life,
the more radioactive the isotope is, and consequentially, the longer
the half-life, the less radioactive an isotope is.

Natural uranium, fresh from the ground, is 99.3% U-238 and 0.7% U-235.

The U-238 [ which is what "depleted uranium" is made of ] has a half-life
of 4.5 BILLION years - so it is only very slightly radioactive. With such
a long half-life, it's almost stable.

The U-235 has a half-life of 704 MILLION years. While U-235 is a little
over 6 times more radioactive than U-238; it is still only slightly
radioactive.

Weapons grade uranium is mostly U-235. So while about 6X more active
than natural or depleted uranium; it is still very low.

So in terms of radioactivity; depleted uranium has the least, natural
uranium somewhat more than depleted; and weapons grade 6X the other
two - but still very low.

Additionally, as before, uranium is an alpha emitter. Alpha radiation
will not penetrate a sheet of paper, nor the dead layer of skin.

You don't use uranium in an RDD or "dirty bomb". The types of materials
that one would use in an RDD should be relatively short lived gamma
emitters. Cobalt-60 and Cesium-137 would be good candidates.

There is so much really BAD information in the media. The media
reporters don't understand this stuff - and haven't made an effort to
understand it - because it's really very simple.

In the media, a "nuke" is a "nuke" is a "nuke". They don't draw a distinction
between RDDs and a real nuclear weapon. That's why there are a lot of
people that think that "weapons grade" uranium goes into a "dirty bomb".

After all, a "dirty bomb" is a weapon - so you use "weapons grade". WRONG!!!

An RDD or "dirty bomb" has virtually nothing in common with a real
nuclear weapon. A dirty bomb doesn't use "weapons grade" uranium.
It also doesn't make a big explosion that can level a city - only a real
nuclear weapon does that.

A "dirty bomb" is a very, very, simple device relative to a real nuclear
weapon.

Dr. Gregory Greenman
Physicist

stoned

in that movie about first US nucluar bomb, one of the scientist died from touching two sphers of weapon grade uranium. you know what i'm talking about ?

Morbius

Stoned,

Not quite.

What you are most likely referring to is the case of Louis Slotin.

The part of the movie "Fat Man and Little Boy", in which the character
played by John Cussack receives a fatal radiation dose is a piece of
fiction that did not occur during the Manhattan Project - but is modeled
after an accident at Los Alamos that occurred 2 years later.

Louis Slotin was a scientist at Los Alamos, and in 1947 he was doing an
experiment at Los Alamos checking the critical mass for a bomb core in
what they called "tickling the dragon's tail".

He had 2 hemispheres of uranium - that if assembled would give you a
critical mass. He was supposed to get them almost, but not quite
assembled by holding them apart with a screwdriver.

Unfortunately, the screwdriver slipped - and the 2 hemispheres
assembled in a critical mass - there was a nuclear chain reaction -
and Slotin died several days later from massive radiation.

But this is NOT radioactive decay of the uranium. He accidently
assembled a bomb core. It was a fission chain reaction - like what
happens in a nuclear bomb when it's detonated that produced the
massive radiation. Louis Slotin, in essence, set off a small nuclear
"explosion" - and he died from the radiation.

Dr. Gregory Greenman
Physicist

stoned

thanks for claryfing, one question : would there be a regular nuclur explosion with mushroom and stuff ( like hiroshima ) from that accident ?

Pengwuino

So whats all the fuss with people saying "terrorists will steal nuclear material and set off dirty bombs!!!"? I mean if this is such basic information, why is it never disputed out in the media?

hitssquad

Pengwuino,

Uranium-235 and plutononium-239 are fissile radioisotopes — and therefore they can be used to make fission weapons — but they do not happen to be very radioactive. If you were making a dirty bomb, you might want to use radioisotopes that are much more radioactive — such as cesium-137, strontium-90, etc. You can find those radioisotopes in nuclear waste.

So, we are worried about terrorists stealing:

1. weapons grade plutonium or uranium, in order to make fission weapons (atomic bombs that produce a large blast like the ones dropped Hiroshima or Nagasaki)
   
   
2. nuclear waste, in order to make dirty bombs (rudimentary devices composed of ordinary chemical explosives surrounded by highly-radioactive isotopes intended to be dispersed by the chemical explosives in populated areas in order to poison people and create terror)