  Relativistic neutron-loaded outflows in gamma-ray bursts are studied at their
early stages, before deceleration by a surrounding medium. The outflow has four
components: radiation, electrons, protons and neutrons. The components interact
with each other and exchange energy as the outflow expands. The presence of
neutrons significantly changes the outflow evolution. Before neutrons decouple
from protons, friction between the two components increases their temperatures
by many orders of magnitude. After the decoupling, the gradual neutron decay
inside the outflow has a drag effect on the protons and reduces their final
Lorentz factor.
