Conservation Laws as Sanity Checks

Energy, particle, and momentum balances must close in every simulation; a leak in a conserved quantity is a defect, not noise.

Balances that must close

Physical solvers must conserve what nature conserves. We check global energy, particle, charge, and momentum balances on every run and require them to close to a stated tolerance. A power balance that is off by a few percent is not acceptable slack; it is evidence that the model is doing something we have not accounted for.

The power balance is the spine of the design

For the breeder (Hyperion), the fusion power of 88.7 MW and the scientific gain Q_sci of 3.424 are two faces of one balance: power out versus power in. Those numbers only mean anything if the full accounting closes, including radiated power, conduction losses, and the heating power in the denominator of Q. We report the balance, not just the ratio.

Tritium and helium accounting

The breeder is credited with roughly 4 kg/yr of tritium-class product and about 1.97 kg/yr of helium-3, plus 14 MeV neutrons. Every one of those flows is a term in a species balance. The tritium breeding ratio is treated as a design lever across 1.1, 1.5, and 1.8 precisely because tritium self-sufficiency is a conservation question we have not closed on hardware, and we will not pretend otherwise.

Conservation checks are unglamorous and non-negotiable. They are the first thing we run and the first thing an outside reviewer should demand to see. A model that balances is not guaranteed correct, but a model that does not balance is guaranteed wrong, which is why the balance is the first gate a result must pass before any of its more interesting numbers are believed.