Fission Energy per Mole Calculator

Formula Used

How to Use This Calculator

1. Select an input method: energy per fission or mass defect.
2. Enter the energy value and unit, or enter Δm in atomic mass units.
3. Set the fission fraction to match burnup or completion.
4. Optionally reduce recoverable fraction for non-recoverable energy.
5. Provide the fuel molar mass to compute energy per kilogram.
6. Press Calculate to view results above the form.
7. Use the CSV and PDF buttons to export the report.

Example Data Table

These are illustrative values. Real systems vary by isotope and design.

Fission Energy per Mole: Practical Notes

1) What this calculator estimates

This tool estimates the energy released when a mole of fissionable nuclei undergoes fission. One mole contains 6.02214076×10²³ nuclei (Avogadro’s constant). If a typical fission releases 200 MeV, the raw energy per mole is roughly 1.93×10¹³ J/mol before any scaling factors are applied.

2) Key unit conversions used

Nuclear energies are commonly expressed in MeV. The calculator converts using 1 MeV = 1.602176634×10^-13 J. When you enter eV, kJ, or J, the input is normalized to joules, then mapped back to MeV for easy comparison across cases.

3) Using mass defect as an input

If you know the mass defect per fission, the calculator applies the rest‑mass energy conversion 931.494 MeV per atomic mass unit. For example, a mass defect of 0.215 u corresponds to about 200.3 MeV, which closely matches many U‑235 fission energy summaries.

4) Why fission fraction matters

Real systems rarely achieve “one fission per nucleus” across an entire mole of material. The fission fraction lets you model partial burnup. For instance, at 75% fission fraction, the net molar energy scales linearly to 0.75× the full‑fission value.

5) Recoverable fraction and losses

Not all released energy is recoverable as useful heat or work. Some energy can escape as neutrinos and some is lost in conversion and transport. The recoverable fraction is a simple efficiency‑style factor. A common engineering placeholder is 85–95% depending on what you consider “recoverable.”

6) From molar energy to per‑kilogram energy

The calculator also reports energy per kilogram using your molar mass. With a molar mass of 235 g/mol, a net value of 1.73×10¹³ J/mol (example inputs) becomes about 7.38×10¹³ J/kg. This highlights why nuclear fuels are extremely energy‑dense compared with chemical fuels.

7) Useful benchmarks for interpretation

For scale, 1 kWh = 3.6×10⁶ J. A full‑fission mole near 1.9×10¹³ J corresponds to about 5.3×10⁶ kWh. The TNT benchmark is also included using 1 kg TNT ≈ 4.184 MJ, which helps compare orders of magnitude across industries.

8) Recommended input ranges

For most textbook fission estimates, use 170–210 MeV per fission and set the fission fraction to your burnup assumption. Keep recoverable fraction at 90–100% unless you have a specific accounting model. Enter a molar mass matching the isotope you are modeling (for example, 235 or 239 g/mol).

FAQs

1) What does “energy per mole” mean here?

It means the total energy released if a mole of nuclei experiences fission, scaled by your fission and recoverable fractions. One mole corresponds to 6.022×10²³ nuclei.

2) Which energy per fission value should I use?

A common estimate for U‑235 is about 200 MeV per fission. If you are modeling a different isotope or a specific dataset, enter that value to match your reference.

3) Why offer a mass defect option?

Sometimes you know Δm from reaction products. The calculator converts Δm in atomic mass units to energy using 931.494 MeV/u, then proceeds with the same molar scaling.

4) What is the recoverable fraction used for?

It models energy that is not practically captured as useful heat or work. You can keep it at 100% for ideal comparisons, or reduce it to represent losses and accounting choices.

5) Does this include reactor efficiency to electricity?

Not directly. Recoverable fraction is an energy accounting factor. Electrical conversion depends on plant design, typically much lower than 100%. You can apply an additional efficiency externally if needed.

6) Why do I need the molar mass input?

Molar mass allows conversion from energy per mole to energy per kilogram or per gram of fuel. This is useful for comparing energy density across fuels and systems.

7) Are the TNT comparisons exact?

They are approximate, using 1 kg TNT ≈ 4.184 MJ. This benchmark is helpful for intuition and rough scaling, not for precision explosive engineering calculations.