# [ExI] Could Thorium solve our energy problem?

Brent Neal brentn at freeshell.org
Sat Jul 10 11:52:02 UTC 2010

```On 10 Jul, 2010, at 1:10, John Clark wrote:

> On Jul 10, 2010, at 12:25 AM, Brent Neal wrote:
>
>> I think you are wildly optimistic and haven't done either the research or the math on how much energy is released in U-233 fission.
>
> Optimism has nothing to do with it, I maintain that it is a FACT that one kilogram of thorium contains at a minimum 200 times as much usable energy as a kilogram of Uranium as used in todays slow neutron reactors. This is true for 2 reasons:
>

John,

Because you were using business-person math to make your assumption, and my 80 TJ number was based on a published number for U235 fission plus a bit of Kentucky windage, I decided to post the full calculation for the energy released. This calculation involves looking at the kinetic energy of the fission fragments and the energies of the released photons and electrons (which can be calculated by differencing the rest masses of the U and the fragments.) Usually, this information is captured in a table of nuclides.  Since I have long since sold my old nuclear physics text,  I went looking for the relevant tables.  Lo and behold, the following table has been helpfully posted on the internet:  http://www.kayelaby.npl.co.uk/atomic_and_nuclear_physics/4_7/4_7_1.html

You will note that for U233, the basic release of energy per atom is 197.9 MeV, with an additional 9.1 MeV available from recapturing the fast neutrons. So the most energy that can be extracted per atom of uranium-233 is 207 MeV, or 3.32 e-11 J/atom.   There are 6.023e23 atoms/mol, thus we get 2e12 J/mol.  1 mol of U233 weighs 233g, roughly. This gives us 85 GJ/g or  85 TJ/kg. Thus, my original estimate was off by about 6%, but I'm expect that when the nuclear physicists do the calculation they correct that number for the neutrons that are captured and lead to fission.

B

--
Brent Neal, Ph.D.
http://brentn.freeshell.org
<brentn at freeshell.org>

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