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By
Nick Touran, Ph.D., P.E.,
2020-10-30
, Updated 2023-04-29
, Reading time: 1 minute
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A single uranium oxide fuel pellet weighs about 10 grams. This has 8.8 grams of uranium in it (the rest is oxygen), so, using energy density values, it contains 35,000 MJ in a typical reactor and at least 700,000 MJ in a breeder reactor. Thus we can compare its content to other fuels. Here is the result:

Material | Energy Density (MJ/kg) |
Equivalent to fuel pellet in LWR |
Equivalent to fuel pellet in breeder |
---|---|---|---|

Coal | 30 | 1.3 tons | 22 tons |

Oil | 42 | 250 gallons | 4350 gallons |

Natural Gas | 53.5 | 34,000 cubic ft | 590,000 cubic ft |

Lithium | 43 | 0.9 tons | 16 tons |

Note: The characteristics of the power generation system affect exactly how much usable energy is extracted. For instance, if a power plant makes heat to be converted to electricity, the thermal efficiency (\(\epsilon_{th}\)) determines how much of the heat gets converted to electricity. These values vary from around 35-45% for coal plants and advanced nuclear plants to 33% for typical nuclear plants, to above 60% for combined cycle natural gas plants. Thus, from a electricity point of view, the values above would be 20-50% less.

Data supporting this include:

- crude oil volumetric energy density 37 MJ/L
- natural gas density at STP is 0.0364 MJ/L
- lithium energy density is 43 MJ/kg
- coal energy density is 30 MJ/kg

GNU units commands:

```
units -1 --digits 2 "46 MW*d/kg * 10 grams * 238/(238+32)" "MJ"
3.5e4
units -1 --digits 2 "46 MW*d/kg * 10 grams * 238/(238+32)/(30 MJ/kg)" "ton"
1.3
units -1 --digits 2 "46 MW*d/kg * 10 grams * 238/(238+32)/(43 MJ/kg)" "ton"
0.9
units -1 --digits 2 "46 MW*d/kg * 10 grams * 238/(238+32)/(37 MJ/L)" "gallon"
2.5e2
units -1 --digits 2 "46 MW*d/kg * 10 grams * 238/(238+32)/(0.0364 MJ/L)" "ft^3"
3.4e4
```

For breeders, do the same with 800 MW*day/kg instead of 46.

*This page is a part of our Factlet collection.*