Most (n,p) reactions have threshold neutron energies below which the reaction cannot take place as a result of the charged particle in the exit channel requiring energy (usually more than a MeV) to overcome the Coulomb barrier experienced by the emitted proton. The (n,p) nuclear reaction N (n,p) C is an exception to this rule, and is exothermic – it can take place at all incident neutron energies. The N (n,p) C nuclear reaction is responsible for most of the radiation dose delivered to the human body by thermal neutrons – these thermal neutrons are absorbed by the nitrogen N in proteins, causing a proton to be emitted; the emitted proton deposits its kinetic energy over a very short distance in the body tissue, thereby depositing radiation dose.