Determination of neutron multiplication, (1). Concept

In a highly subcritical system with reflector, it is demonstrated that none of the methods so far developed serves usefully in determining the value of the multiplication factor with good accuracy, and that the fundamental difference between the essential properties of the prompt and the delayed neutron modes makes it to be extremely difficult to develop a new method to fulfil this need. Based on this judgement, it is proposed to abandon the widely used concept of multiplication factor, and to look for a new concept to represent the state of neutron multiplication, in the case of reflected highly subcritical systems. In this paper the authors present a new concept in which a fundamental prompt neutron decay constant α₀₀₀ is adopted to measure the neutron multiplication, this constant being of such nature as to satisfy the following two fundamental conditions: (1) It is uniquely measurable free from spatial and energetic dependence, and (2) it is amenable to direct calculation from the fundamental equation for neutron transportation. (author)