What is the total amount of energy released by depleted uranium decaying to stable elements, over billions of years? Here is the result of summing all the energies of the radium series highest probability decay chain:
| Parent | MeV | Daughter | Running sum |
|---|---|---|---|
| U-238 | 4.270 | Th-234 | 4.27 |
| Th-234 | 0.273 | Pa-234m | 4.543 |
| Pa-234m | 2.271 | U-234 | 6.814 |
| U-234 | 4.859 | Th-230 | 11.673 |
| Th-230 | 4.770 | Ra-226 | 16.443 |
| Ra-226 | 4.871 | Rn-222 | 21.314 |
| Rn-222 | 5.590 | Po-218 | 26.904 |
| Po-218 | 6.115 | Pb-214 | 33.019 |
| Pb-214 | 1.024 | Bi-214 | 34.043 |
| Bi-214 | 3.272 | Po-214 | 37.315 |
| Po-214 | 7.883 | Pb-210 | 45.198 |
| Pb-210 | 0.064 | Bi-210 | 45.262 |
| Bi-210 | 5.982 | Tl-206 | 51.244 |
| Tl-206 | 1.533 | Pb-206 | 52.777 |
(Data from Wikipedia)
Total is 52.777 MeV per atom (238.05078826 amu), or 2.139*10^13 J/kg. This does not include energy lost (I think) in spontaneous fission. The total output energy is 1.3 million times more energetic than sugar. Yet the first step, uranium 238 to thorium 234 with a half life of 4 billion years, decays so slowly as to be considered non-radioactive! We had gotten a hint at how energy dense DU can be because it can be bred into plutonium 239 for reactors or weapons, and its use as a tamper in bombs.
Power density
You have: 4.27 MeV / 4 giga year 238.05078826 amu
You want: W / kg
* 1.3710866e-05
You have: 52.777 MeV / 4 giga year 238.05078826 amu
You want: microW / kg
* 169.46567
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