Answer:
potential energy decreases
kinetic energy increases
If you mean nuclear, fission is a radioactive isotope losing protons or "radioactive decay"
whereas nuclear fusion is where 2 atoms hit each other and combine,
like on the sun where hydrogen hits each other and makes helium.
Superheated water is liquid water under pressure at temperatures between the usual boiling point, 100c (212 F ) and the critical temperature , 374 C (705F) . It is also known as “subcritical water”
Or “pressurized hot water”.