Fusion of Polarized Deuterons

The nuclear physics aspects of the $d-d$ reactions initiated by low-energy polarized deuterons are discussed. It is shown that the use of polarized deuterons does not suppress the fusion of deuterons with deuterons and hence does not suppress neutron production. Therefore a recently proposed "neutron-free" $d$-${}_{}{}^3{}_{}{}^{}\mathrm{He}$ fusion reactor is unlikely to work.