When uranium splits, the story is not over. The two pieces are born hot and unstable, then shed neutrons and light as they settle down—and predicting that aftermath matters for reactors, medicine, and nuclear waste. When a heavy nucleus splits, its two pieces release particles that create several linked outcomes, including the amounts of radioactive products and the numbers and energies of emitted neutrons and light.

Those outcomes matter beyond the laboratory: they support reactor-safety estimates, nuclear-waste treatment, medical radioisotopes, and the study of how elements form in stars. The central idea is like checking a recipe with one shared kitchen: a common, consistent code probes starting-assumption biases separately from effects addressed during deexcitation.

Different fragment generators provide starting descriptions, including microscopic and phenomenological models, and TALYS then applies the common deexcitation calculation to produce prompt observables. The calculation follows the excited pieces as they release neutrons and light, producing the observable results of fission.

The starting information describes how often different pieces are made, how much energy they carry, and how that energy is spread. The calculation produces deexcitation data that can be compared with measurements and with results from other stand-alone models, enabling broad comparison of systematic errors and model defects.

The cooling calculation depends on how the pieces’ rotation is distributed and on how finely their possible energy states are represented. The number of energy states changes when more nucleons are released: it stays fixed at first, is reduced later, and is cut in half when the number released becomes large.

The predicted neutron count follows the same saw-tooth pattern as measurements, and the TALYS version based on the H F three-D model agrees fairly well near the most probable masses. But the agreement worsens for very uneven splits. Another version predicts too many neutrons from the heavy pieces and too few from the light pieces, while the neutron count reaches a pronounced minimum near especially stable nuclear arrangements.

This matters because the predicted outgoing-neutron energies follow the measured pattern only up to about two megaelectronvolts; beyond that, the two calculation approaches bend away in opposite directions, showing that the treatment of neutron evaporation strongly shapes the result.

The neutron-energy results do not describe the experimental shape above two mega-electron-volts. One calculation has a harder high-energy tail, while the other has a softer tail. The difference between the two results reflects differences in how the codes calculate the pieces’ evaporation.

For light emission, the calculation reproduces the measured saw-tooth pattern in how many light particles come from fragments of different masses, but it underestimates the overall amount. Its predicted light-particle energy pattern also contains a strong low-energy peak linked to the calculation’s grouping of energies, and it falls below measurements in some low- and high-energy regions.

The calculation connects the initial split with the particles and radioactive products that follow. It improves the ability to compare competing pictures of fission, while also revealing where important predictions still disagree with measurements.