Izvestiya vuzov. Yadernaya Energetika

The peer-reviewed scientific and technology journal. ISSN: 0204-3327

On the Concept of Delayed Neutron Multiplication Factor

12/14/2022 2022 - #04 Personnel training

Yuferov A.G.

DOI: https://doi.org/10.26583/npe.2022.4.12

UDC: 621.039.514.4:621.039.515:621.039.516:378

The article considers methodological issues related to the conceptual and terminological apparatus of the dynamics of nuclear reactors. Based on an elementary analysis of the standard nuclear reactor dynamics equations, it is shown that the delayed neutron multiplication factor (DNMF) in the form of kdn = βkef, the product of the «effective delayed neutron fraction» by the population multiplication factor, has no physical meaning. This incorrectness is due to the fact that the parameter β does not express the actual fraction of delayed neutrons (DNs) in the population. It follows directly from the transfer equations that, in transient regimes, the rate of generation of DNs and, consequently, their fraction in the population are variable values. The concept of ‘multiplication factor’ as the ratio of the rates of generation and loss of particles is not applicable to DNs, since the transport equations do not describe the processes of their absorption and leakage. For this reason, the author proposes a number of meaningful and terminological clarifications of the concepts under consideration. Possible definitions of the parameters kef, kmn, kzn in conjunction with other parameters of the NR dynamics are considered. Alternative possibilities for reflecting the contribution of DNs to the dynamics of the total neutron population are presented. The options for determining the multiplication factor are compared based on the description of the NR dynamics in terms of generations and the balance of process rates. The non-identity of the multiplication factors appearing in the generation model and in the rate model is shown.


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nuclear reactor dynamics delayed neutron multiplication factor

Link for citing the article: Yuferov A.G. On the Concept of Delayed Neutron Multiplication Factor. Izvestiya vuzov. Yadernaya Energetika. 2022, no. 4, pp. 134-146; DOI: https://doi.org/10.26583/npe.2022.4.12 (in Russian).