  The present status of the nuclear reaction rates determining the solar
neutrino flux is discussed. This includes the reaction rates for the two
branching ratios of the three pp-chains involving the reactions 3He(3He,2p)4He
and 3He(4He,gamma)7Be for the first branching, and 7Be(e-,nu_e)7Li and
7Be(p,gamma)7B for the second branching. Mainly we will concentrate on the
basic nuclear reaction p + p -> D + e+ + nu_e of the pp-chains. We use a
relativistic field theory model of the deuteron to calculate the low-energy
cross section for this reaction. The theoretical prediction of the cross
section obtained is about 2.9 times largerthan given in the conventional
potential approach. The consequences of this new reaction rate for the solar
neutrino problem will be presented and discussed.
