One major objective of this work is to experimentally estimate the following kinetic parameters on the IPEN/MB-01 research reactor at São Paulo: the effective neutron delayed fraction, β e f f , the prompt neutron generation time, Λ, and the ratio β e f f /Λ. In order to achieve our goal, we will use a microscopic noise technique called Rossi-α method. This method is based on the statistical nature of the fission-chain process. Using a coincidence acquisition system, the rationale is to experimentally determine the probability distribution of detecting neutrons from the same chain. Through a least-squares fit of this distribution we estimate the prompt neutron decay constant α = (β e f f − ρ)/Λ. The α parameter will be measured for three sub-critical levels using three different source configurations, and the ratio β e f f /Λ is obtained via a extrapolation to ρ = 0. A specific acquisition system for Rossi-α measurements has been developed in order to achieve our objective. This system is based on a multichannel scaler controlled by virtual instruments that records the timing of all neutron events, allowing data analysis during the acquisition. The first measurements were performed using two BF 3 detectors positioned at the center of IPEN/MB-01 reactor core. In the future the same measurements described above will be performed using 3 He and photodiode detectors. The photodiode detectors have been developed by the Reactor Physics Division of IPEN. In this work we will present a preliminary set of Rossi-α measurements performed on the IPEN/MB-01 research reactor at São Paulo.
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