Experimental Estimation of Moderator Temperature Coefficient of the IPEN-MB-01 Reactor

Rubens Cavalcante Da Silva

doi:10.15392/bjrs.v7i2b.615

Abstract

The aim of this article is to present the procedure for the experimental estimation of the Moderator Temperature Coefficient of Reactivity of the IPEN/MB-01 Research Reactor, a parameter that has an important role in the physics and the control operations of any reactor facility. At the experiment, the IPEN/MB-01 reactor went critical at the power of 1W (1% of its total power), and whose core configuration was 28x26 rectangular array of UO2 fuel rods, inside a light water (moderator) tank. In addition, there was a heavy water (D2O) reflector installed in the West side of the core to obtain an adequate neutron reflection along the experiment. The moderator temperature was increased in steps of 4oC, and the measurement of the mean moderator temperature was acquired using twelve calibrated thermocouples, placed around the reactor core. As a result, the mean value of -4.81 pcm/°C was obtained for such coefficient. The curves of ρ(T) (Reactivity x Temperature) and (Moderator Temperature Coefficient of Reactivity x Temperature) were developed using data from an experimental measurement of the integral reactivity curves through the Stable Period and Inverse Kinetics Methods, that was carried out at the reactor with the same core configuration. Such curves were compared and showed a very similar behavior between them.

Highlights

The moderator temperature coefficient of reactivity αTM of water moderated reactors is an important operational parameter that is strongly associated with safety issues of the nuclear installation [1]
3.1 αTM Values By the values of the mean temperature of the thermocouples and ∆ρ, it was possible to calculate the value of moderator temperature coefficient of reactivity through equations 1 and 4 for each CR2 position
3.2 ρ(T) Curves By means of the CR2 position values (% withdrawn), the integral reactivity values were calculated based on the calibration curves obtained in [10] (Inverse Kinetics and Stable Period Methods) with the same core configuration; and the ρ(T) curves were developed

Summary

Introduction

The moderator temperature coefficient of reactivity αTM of water moderated reactors is an important operational parameter that is strongly associated with safety issues of the nuclear installation [1]. The moderator temperature coefficient of reactivity causes variations in the liquid density and in the energy spectrum of thermal neutrons [3]. Such modification changes the balance between fission and absorption rates in the core, since these factors are function of the energy of neutrons [4]. According to [5], the shift of the neutron spectrum to higher temperatures changes the rates of thermal neutron absorption in the fissile isotopes

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Conclusion