To explain the mechanism of deuterium reactions in palladium and titanium (cold fusion), a model of an exotic deuterium plasma with possibly short nuclear distances due to thermal motion was considered. The screening parameter is increased by lowering the ion temperature. This is the usual feature of the screening phenomenon in plasma. Fully ionized gases of high density and low temperature are never possible outside the lattice. Hence, the growth of the screening parameter can be significant only for the hydrogen isotopes in the metal lattice.