Reactivity Pulse – Impulse Characteristics
We will now study a response of a reactor on a reactivity pulse (impulse characteristics), which is represented by the Dirac delta function, δ(t). Strictly speaking Dirac delta function is not a function, but a so-called distribution, but here the function form will be used, in which the delta function is defined as follows:
the reactivity pulse can be mathematically expressed as ρ(t) = ρ0 . δ(t). Using the inverse Laplace transformation and the system transfer function, G(s), it can be derived that the pulse reactivity insertion causes a transient which is characterized by following relations:
That means the prompt neutron lifetime plays key role in the first part of the transient, while the delayed neutrons play key role in the steady-state neutron level.