In NAA, a sample is exposed to a beam of neutrons to induce temporary radioactivity in the sample. The radioactive isotopes within the sample then decay rapidly, releasing gamma rays that are characteristic of each individual chemical element within the sample. These can be measured to quantify elements within a given sample. Conventionally, NAA has been performed using research scale fission (nuclear) reactors, but as these have diminished globally, it has also been performed at spallation sources such as the ISIS neutron source. NAA techniques can be performed using fast neutrons, epithermal neutrons and thermal neutrons.

NAA techniques have some of the lowest detection limits of any technique. This utility has been improved with recent development of fast and accurate gamma/neutron detectors and spectroscopic technology.

EPAC will produce neutron pulses of extremely short durations (picoseconds). This will enable measurements of the prompt gamma emissions to be taken more rapidly after exposure enhancing detection of short lived isotopes. Particularly those with high neutron cross sections that decay more rapidly. Accurate knowledge of the pulse durations and intervals between pulses will further enhance accuracy along with cyclical measurements taken with multiple pulses of laser-driven neutrons.