Ask A Scientist© Physics Archive

name         Jamie
status       student
age          15

Question -   What is Uranium-238 used for? What is the main purpose
for Uranium-238?


Since U238 is a stable isotope of uranium, it will not produce energy in a
nuclear reactor.  For this we have to have U235, which is unstable.  U238,
since it IS stable is the most commonly occuring isotope of uranium when it
is dug out of the ground.  So usually to use the uranium in a power plant,
the amount of U235 must be increased, run the ore thru a plant and pull out
slightly more U238 than U235, leaving an enriched uranium, enough U235 to
run the reactor.  We would not want pure U235 in a power plant, this would
make it too much like a bomb.  So in this case U238 is "used" to sort of
dillute the U235, to make U235 a safe fuel.

In what is called a breeder reactor, U238 can be converted to unstable
isotopes, and these then used for fuel.  So in this case U238 would be the
starting point for other things, eventually ending up with a fuel for a
nuclear power plant.  This is not a common thing these days partly because
of concern that it is too easy to keep going to make bomb quality fuel.

Since Uranium is a very heavy element, heavier than lead, it is also used in
artillery shells.  The army would put U238 in the front of a shell and shoot
the shell out of a tank or airplane, at the enemy tank.  The uranium in this
case has been processed so as to not have very much at all of U235 left in
it, hopefully pure U238.  So then the shell would not be radioactive.  There
is some controversy as to whether they do a good job of this, and there are
concerns that these shells spread radioactive uranium (U235) around.

Uranium is also well, just another element, and has it's own chemistry.  I
have heard of people putting very small amounts of it into chemistry or
biology experiments (not eating it!) just as a tag, a big atom to ride along
in the experiment to later show up,. to allow the scientist to follow the
process.  Of course this doesn't require very much.


Ross
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Natural Uranium contains a mixture of U235 and U238 isotopes.  It is used to
fuel nuclear reactors, which give us power.
Katie Page
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