Thermal-Neutron ActivationThermal-neutron activation (commonly known as TNA) is widely employedin elemental analysis, since the neutron absorption cross-sectiontends to be highest at the thermal energy. As discussed in section 8.1,low-energy (thermal) neutrons are most likely to cause activation bythermal-neutron capture. The energy of the emitted activation gammaraysare characteristic of the parent nucleus, and hence can be used asnucleus identifiers. The National Data Center provides, on the Internet,provides a list of the thermal-neutron capture gamma-rays by target nucleusand by energy of the emitted gamma-rays [246]. Thermal-neutronsare not as readily available outside a nuclear reactor, as isotopic neutronsources and neutron generators produce fast-neutrons, as indicated insection 2.3.3. Nevertheless, a number of out-of-reactor thermal-neutronactivation systems (called instrumental methods) have emerged.
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