  Reaction network of fluorine-18, oxygen-15 and nitrogen-15 is considered for
its temperature dependent energy output. The main reactions for generation and
annihilation of oxygen and fluorine are coupled in the reaction equations while
nitrogen is produced as a decay product. We find that the governing set of
equations for F18(p, alpha)O15 process in the phase diagram exhibit a
predominance of the direct reaction rather than the reverse reaction consuming
O15. The time-scale determined by the exact solution of this system yields
relatively short time-scale conversion of fluorine into oxygen indicating an
energy generation of 2.8MeV per reaction. The temperature dependence shows that
the effective reaction occurs at temperature about 0.04GK or above.
