On the Definition of the Prompt Neutron Lifetime

Technical Report · Fri Jul 01 04:00:00 EDT 2022

DOI:https://doi.org/10.2172/1874906· OSTI ID:1874906

O'Rourke, Patrick Francis ^[1]; Jaegers, Peter James ^[1]; Temple, Brian Allen ^[1]; Ramsey, Scott D. ^[1]

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1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

There are myriad definitions for the mean neutron lifetime, neutron generation time, and other related quantities to characterize a neutron and its progeny’s propagation through an assembly. In this document, we consider lifetime definitions that are associated with eigenvalue forms of the neutron transport equation. Specifically, we focus on the two most widely used eigenvalues: the $$\kappa$$ eigenvalue and the $$\alpha$$ eigenvalue. These eigenvalues are used more often than other eigenvalues due to the physical phenomenon they capture. The $$\kappa$$ eigenvalue allows for the ability to determine if the system can sustain a chain reaction, while the $$\alpha$$ eigenvalue captures the asymptotic time dependent behavior of the system. An advantage of using these eigenvalues resides in the biorthogonality of the solutions with their adjoint counterpart. This feature allows us to simplify the expressions and to obtain appropriately weighted definitions that highlight important physics and regions of an assembly.

• Research Organization: Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
• Sponsoring Organization: USDOE National Nuclear Security Administration (NNSA)
• DOE Contract Number: 89233218CNA000001
• OSTI ID: 1874906
• Report Number(s): LA-UR-22-26394
• Country of Publication: United States
• Language: English

Related Subjects

73 NUCLEAR PHYSICS AND RADIATION PHYSICS