"Uranium"
"Make a video about uranium"
"Uranium"
"Maybe he just cannot make a video about uranium"
Hmm...
G-Man: We'll see... about that!
(intriguing music)
(extractor fans whirr)
Oh! Hi, Max.
I think they wanted you to film something about uranium
Here's your uranium
Max: Oooh, that's nice
Thank you
Oh... 8-)
Hello everyone.
I guess you have figured that this video is going to be about such a metal as uranium.
However, let me make
give a small warning in order to calm you down
We're currently in the uranium lab
We're certified to work with radioactive materials, such as uranium
so there will be no official problem.
Welcome.
Max: And of course
don't try to repeat these experiments at home
even if you have two pounds of uranium in your garage.
I think now we have settled everything
and can move on to considering properties of the most dangerous metal on Earth...
uranium.
Uranium belongs to the actinide series in the periodic table
that is, to radioactive elements
and its atomic number is
92
Uranium is 40 times more abundant in Earth's crust than silver.
It is so abundant because it forms
upon rapid neutron capture inside spinning supernovas.
That is why Uranium was discovered quite early
in Germany
in 18th century.
Its discoverer, Martin Heinrich Klaproth
named it after a newly discovered planet of the solar system...
after Uranus.
In nature, uranium is often found in such minerals as uraninite and autunite.
This metal often has several oxidation states in those minerals
Thanks to the beautiful yellow colour of such minerals
glass-blowers added them to glass
As a result
minerals would give such a glass
a beautiful greenish colour.
It's a pity that back then
craftsmen didn't know about the toxicity of uranium compounds
Nevertheless, pure metallic uranium can be obtained from uranium ore
via reduction by calcium.
And it looks very ordinary.
Since mostly uranium naturally occurs
in the form of uranium-238 isotope
with a half-life of about 4.5 billion years
depleted uranium is most frequently used for chemical research
in order to reduce scientists' exposure to its radiation.
Pure uranium obtained from its ore looks quite dark
as its surface oxidises pretty fast
because of the high chemical activeness of this metal.
That is why it is often stored in argon
and also all experiments with uranium are conducted in argon atmosphere.
Usually, to conduct experiments a piece of uranium-238
is ripped to such small shreds on a lathe in laboratory.
It is noteworthy that these shreds in the test-tube
already emit beta and gamma radiation
Gamma emission alone is 50 times the normal level.
This emission is caused by the decay products of uranium
which breaks down even further
to beta and gamma particles.
The walls of the test-tube confine the alpha-rays.
Because of its high chemical activeness
uranium shreds burn well in the air
For the first time on YouTube
you can observe how uranium burns
and turns into its oxides.
However
to conduct experiments uranium is not just burned.
Uranium shreds are mixed with iodine crystals
and the chemicals are left to sit for a few days
sometimes with a solvent
in order for them to react.
The reaction produces uranium triiodide
of such violet colour.
The reaction can also produce uranium tetraiodide
depending on the proportions of reagents.
These metal compounds, with +3 or +4 oxidation states
are most frequently used as raw materials to create uranium complexes
and are also used as catalysts
because with such an oxidation state uranium is the most chemically reactive
because of having a lot of electrons in the f-orbitals.
It is noteworthy how quickly the colour of uranium compounds change
depending on the oxidation state.
For instance, it can be seen
when comparing uranium triiodide and uranium tetraiodide.
It is also worth noting
when tetrachloride is used instead of uranium tetraiodide
the colour will also change drastically
from orange to green.
By the way,
uranium tetrachloride used to be used
in early electromagnetic isotope separation uranium enrichment
But soon this method proved to be inefficient
and was substituted by other methods.
Nevertheless, uranium compounds with +4 oxidation state
are quite stable.
That is why they are used most frequently.
For instance, enriched uranium dioxide is used
as nuclear fuel for atomic reactors.
However,
the oxidation state of uranium can be increased
to +6 oxidation state.
For instance, dry uranyl nitrate is a beige powder.
In this form it is most frequently used for experiments.
When exposed to air
this compound absorbs water very well
and it turns into beautiful hexahydrate crystals
which glows in ultraviolet light very well.
Uranyl nitrate is also formed when pieces of uranium react with nitric acid.
Besides, at this particular moment
the shiny surface of the element can be seen very well.
In fact, many compounds of 6-valent uranium have fluorescent properties in ultraviolet light.
That is the very reason why they are added to so-called uranium glass
which beautifully glitters in the sun with bright green colour.
Whereas, in the dark, when an ultraviolet flash-light is pointed at it
it looks even more stunning.
Because of its fluorescent properties, uranium is most frequently depicted as glowing with green
in most cartoons and films.
Although in reality uranium fuel and uranium itself are usually of dark colours
and don't attract much attention.
Besides, it's worth remembering that many uranium compounds are very toxic
and, needless to say, are also very radioactive.
There are also uranium compounds with +5 oxidation state
However, only in 2006
stable uranium compounds with +5 oxidation state were obtained
that didn't break down at room temperatures.
It was achieved as a result of stabilisation of uranyl ion
with the help of organic coordination ligands.
And, if you think that scientists were doing useless things
I hasten to question that statement.
Nowadays, because of the large amount of processed nuclear fuel
there is always a risk of water and soil contamination
with well-soluble 6-valent uranium compounds.
However, if they are converted to +4-valent uranium compounds
they do not dissolve in water.
The risk of water contamination decreases by a few times
because 4-valent uranium compounds will just sink to the bottom
and can later be easily collected.
Also, 5-valent uranium is often stabilised by iron ions
for instance, in such an iron ore as magnetite.
That is why now scientists are seeking to use it for a more efficient nuclear fuel recycling.
And now, let us recall to the title of this video
and answer the question
Why uranium is so dangerous?
It's so because this is the very metal that the Little Boy bomb, dropped on Hiroshima in 1945, was made of.
This bomb was designed using a gun method.
Two parts of enriched uranium in sub-critical state
were shot in each other.
After being in contact, the mass of uranium would reach a critical point
and this would trigger a chain reaction
when uranium cores would start dividing
under the influence of an enormous amount of neutrons
which reflected off the tamper, made from tungsten carbide.
As a result, the nuclear explosion killed about 2,000 people
becoming the first use of atomic weapons in history.
Besides, in a nuclear reactor uranium-238 can be turned into plutonium-239
by irradiation with slow neutrons.
It is known that plutonium-239 is fitting for making implosion-type atomic bombs
because its critical mass is smaller.
As if that was not enough
uranium is also a very toxic metal
That is why, because of these dangerous properties, it can be called the most dangerous metal.
It is also worthy of note that naturally occurring uranium
mostly consists of isotope uranium-238
which cannot divide spontaneously
and is not suitable to be used for making nuclear weapons.
Only less than one percent of uranium
or more precise, uranium-235
can run a self-sustaining nuclear chain reaction
and can be used to make atomic bombs.
To make those bad things
the concentration of isotope 235 is increased...
to 85%
whereas only 3% of uranium-235 is enough to make nuclear fuel for power stations.
Usually enrichment is done by centrifugation of gaseous uranium hexafluoride
in special machines.
During this process a lot of needless uranium-238 is released
and concentrated.
That is how depleted uranium is obtained.
Its radioactivity is much smaller than that of enriched fuel.
As a result of the cold war, there has been produced too much depleted uranium
that people don't know what to do with it.
Thanks to its high density
depleted uranium is used as aircraft loads for balance
as tank armour
and even as missile cores.
However, because of being highly active
uranium armour can ignite
and that is why it can be risky to use.
It's also noteworthy
that because of the very long half-life of uranium
it is still a source of warmth of Earth.
To make a conclusion, we can say
that uranium is the most dangerous metal on Earth
because it's very toxic
and people have made one of the most destructive weapons from it.
One step in the wrong direction can lead to disastrous consequences.
Chernobyl nuclear disaster is a testimony to that.
Humans have yet to find an efficient way of recycling uranium
with as little impact on nature as possible
and also to decrease the risk of nuclear disasters
and environmental contamination.
If you liked this video, please give a thumbs up
and also, if you have access to some radio-chemistry laboratories
and you can help me
in the continuation of production videos about actinides
please contact me via my email.
If you would like to support the continuous production of science videos like this one
please support channel on Patreon,
link in the video description.
(inspirational music)
=^.^=