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Computation of Bias on Measured $\alpha_p$ by Monte-Carlo Simulation

R. Boffy 1, 2, * C. Jammes 1, 2, *
* Corresponding author
1 LDCI - Laboratoire de Dosimétrie, de Contrôle-commande et Instrumentation
SPESI - Service Physique EXpérimentale, d'essais en Sûreté et d'Instrumentation : DEN/DER
Abstract : Controlling the reactivity of a nuclear reactor requires the knowledge of its kinetic parameters. Even though they can be computed by neutronic codes, they often have to be measured to finish the commissioning of a new installation. Amongst the list of kinetic parameters, we are specifically interested in the prompt-decay constant ($\alpha_p$). In practice, the presence of a reflector generates a decay constant, which will differ from core's $\alpha_p$ , and that might disturb the measurement of the whole set of kinetic parameters. Such a behaviour is a drawback for experimentalists since neutron detectors are usually located in non-fissile areas. The aim of the study is to give numerical estimates of the bias that can come out when measuring kinetic parameters of a light-water nuclear reactor. The work is based on on time-impulse techniques to derive kinetic parameters from the flux decay of the system. The impact of the detector position, as well as the reactivity level have been studied in a concurrent way. As an example, it was shown that $\alpha_p$ could be underestimated by a factor ranging from 8 to 12 % in a case of a sub-criticality of −3600 pcm, if the detector was located in the core or the reflector, respectively.
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Submitted on : Monday, April 27, 2020 - 9:56:00 AM
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R. Boffy, C. Jammes. Computation of Bias on Measured $\alpha_p$ by Monte-Carlo Simulation. 2020. ⟨cea-02555090⟩



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