Delayed Neutron Energy Spectra
The key properties of delayed neutrons, which are very important for the nuclear reactor design, belong also delayed neutron energy spectra. The energy spectra of the delayed neutrons are the poorest known of all input data required, because it very difficult to measure it.
Depending on the type of the reactor, and their spectrum, the delayed neutrons may be more (in thermal reactors) or less effective than prompt neutrons (in fast reactors). In order to include this effect into the reactor kinetic calculations the effective delayed neutron fraction – βeff must be defined.