Interpretation of flux shape transient with concepts of 'region of unity' and 'region of influence'

Concepts of "region of unity "and" region of influence" are introduced to interprete space-time flux behavior in general. The normalized fractional power change U is first defined by U(r,t)≡f/maxr fφ≡ where f≡φ(r,t) ≡&0(r) is the fractional power change. The factor of unity is then defined by u(t)= min r U(r, t). The fractional power change through-out the core is therefore estimated within the limits of [u,1], If the flux shape does not change, u is always equal to unity in a reactor core; u can be a measure of coupling strength or "degree of unity" of the transient flux distribution inside a core. The region of unity is finally defined to be a region in which the normalized fractional power change U is larger than a predetermined number close to 1 (0.8 for example). Within the region of unity, approximations relevent to a point reactor are applicable, and the power change proceeds at the same pace throughout this region. Thus, one detector for each region of unity is sufficient for keeping track of the core power distribution.