Future of America's Nuclear Power Plants

[PamW]

7. FAILED UNDERSTANDING, AGAIN!!!

Once again Kris doesn't understand what the truthful
answer to the question is; because once again he has
completely FAILED to understand the question.

We see that in his quoted statement about the time it
takes to transmute U-238 into Plutonium. Who said
anything about transmuting U-238 into Plutonium?
In fact, in my response I specifically said that I was
NOT talking about burning U-238 but merely putting
it back into the ground. That doesn't take time.

This is what happens when one relies on one's own
beliefs as the authenticator of truth, as opposed to
any real intellect or advanced education. I forget
that I'm not talking to my colleagues. All of us have
documented high IQ's and advanced degrees from
prestigious universities.

This is going to be like attempting to explain quantum
mechanics to the cat. It's difficult to explain the meaning
of the Schroedinger equation when there just isn't that
much mental horsepower on the receiving end. However...

First, natural uranium is about 0.7% U-235 and 99.3% U-238
(In a recent post, Kris attempted to tell us that about half of
natural uranium was U-234.)

http://en.wikipedia.org/wiki/Natural_uranium

Natural Uranium (NU) refers to refined uraniumwith the same isotopic ratio as found in nature. It contains 0.7 % uranium-235 99.3 %uranium-238,..

The typical fresh reactor core is 100 tons of uranium with about 4% enrichment.

So a new core has 4 tons of U-235 ( 4% of 100 tons). In order to get that amount
of U-235 from natural uranium, I need 400 tons of natural uranium to get 4 tons
of U-235 ( 1% of 400 tons = 4 tons ). The 4% fuel will also contain 96 tons of U-238.
So of the 400 tons of NU; the 4 tons of U-235 will be used in the fuel. 96 tons of the
396 tons of U-238 will also go into the fuel; leaving 300 tons of U-238 tailings ( which
is called depleted uranium ). However, somewhere there is a hole in the ground that
used to contain 400 tons of uranium.

Now what is the composition of spent reactor fuel:

http://en.wikipedia.org/wiki/Spent_nuclear_fuel

About 96% of spent fuel is Uranium, mostly U-238:

96% of the mass is the remaining uranium: most of the original 238U and a little 235U...

The U-235 is <1%. So a 100 ton spent nuclear core has
about 95 tons of U-238 and 1 ton of U-235.

Is it the uranium that makes spent fuel so difficult to dispose of?
NO - that U-238 and U-235 is no different than what came
out of the ground. So nobody should have any objections to just
putting it back.

What else is in spent fuel. Our 100 ton core has 3 tons of fission
products:

3% of the mass consists of fission products ...The fission products include every element from zinc through to the lanthanides

Is this what makes the spent fuel problem have such a long longevity?
NO - fission products decay in a relatively short amount of time. Again
from the PBS Frontline interview with nuclear physicist Dr. Charles Till:

http://www.pbs.org/wgbh/pages/frontline/shows/reaction/interviews/till.html

Q: And you repeat the process?
A:Eventually, what happens is that you wind up with only fission products, that the waste is only fission products that have, most have lives of hours, days, months, some a few tens of years. There are a few very long-lived ones that are not very radioactive.

So it is not the fission products that have the long life times.

What else is in spent fuel? There is Plutonium:

About 1% of the mass is 239Pu and Pu-240 resulting from conversion of 238U, which may be considered either as a useful byproduct, or as dangerous and inconvenient waste.

Pu-239 has a half-life of 24,110 years.

The entire reason for the longevity of spent nuclear fuel is due to the 1% that is
Pu-239 and other actinides.

So if we bury spent fuel; we have to have a facility that can handle the 1% of the
spent fuel that is long-lived Plutonium and other actinides.

Is there something else we can do with the 1 ton of Plutonium from our 100 ton core?
YES - we can burn it as fuel. Plutonium and actinides are useful reactor fuels and we
have 1 ton in our spent fuel. When we refuel the reactor, we need 4 tons of fissile material.

So we send our spent fuel to be reprocessed. We can separate the components. We need
4 tons of fissile material for the new core; we have 1 ton of U-235 in the spent fuel, and
we have 1 ton of Plutonium and other actinides. So we have 2 tons of the 4 tons needed.
So we put the 2 tons of U-235 and Pu-239 and actinides back into the reactor. ( We agument
with another 2 tons of fresh fissile material, for a total of 4 tons )

We also have 95 tons of U-238. We can combine that with the 300 tons of U-238 from the
waste stream of the enrichment plant to get 395 tons of U-238. We can put that 395 tons
of U-238 back where we got it; back into that hole in the ground from which we took 400
tons of natural uranium. Nobody should have a problem with that, as we are just putting
back most of what we took out.

We have to store those fission products for the timescales mentioned by Dr. Till above.

However, we don't have anything in the waste stream that has lifetimes of thousands of years!
So the long lifetime problem of nuclear waste is solved by the scheme outlined above.

Now what Arjun is talking about is something completely different He's talking NOT
about putting the U-238 back into the ground as I proffer; he is talking about converting
it all to Plutonium before burning it as fuel. That is going to take a long time. I think that
would be a good idea; because it means we would have power for a long time, and it sure
puts a LIE to the claim by the anti-nukes that we only have 20 or 40 years or whatever
worth of nuclear fuel left.

But Arjun's scheme and my scheme are different. My U-238 goes back into the ground, which
one can do immediately, and Arjun has the U-238 converted to Plutonium which takes hundreds
of years. Unfortunately, Kris can't tell the difference between these two schemes.

PamW