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S. K. Trikha, P. S. Grover
Nuclear Science and Engineering | Volume 26 | Number 4 | December 1966 | Pages 447-452
Technical Paper | doi.org/10.13182/NSE66-A18415
Articles are hosted by Taylor and Francis Online.
In the case of crystalline (coherent) moderators, it has been observed that the trapping of neutrons in the Bragg peaks greatly affects the decay of a neutron pulse from inside small assemblies and leads to a much larger value of the observed decay constant as compared to the theoretical limit. In the present paper we report a theoretical study of the pulsed neutron problem in finite assemblies of incoherent solid moderators. We find that even in the absence of the trapped neutrons, it will take a very long time for the decay constant to approach the theoretical asymptotic limit (υ∑s)min. A study of transient spectra has also been made in these assemblies. We find that for large assemblies (B2 < ), the value of λ calculated from the study of transient spectra agrees well with the asymptotic decay constant. However, for small assemblies, the equilibrium is not attained within 600 μsec, the time limit of our studies.