REACTOR NOISE EXPERIMENTS CONSIDERING HIGH FREQUENCIES IN THE IPEN/MB-01 REACTOR

Diogo Feliciano Dos Santos,P Blaise,M Margulis,Adimir Dos Santos

doi:10.1051/epjconf/202124708010

Diogo Feliciano Dos Santos, P Blaise + Show 2 more

Open Access

https://doi.org/10.1051/epjconf/202124708010

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Abstract

Reactor noise experiments at high frequencies (up to 100 kHz) in subcritical configurations have been performed at the IPEN/MB-01 research reactor facility. The core configuration considered a short version of the IPEN/MB-01 core in a 24 × 26 rectangular array of fuel rods. The subcritical configurations considered the control banks totally withdrawn and the moderator poisoned with H3BO3. The boron concentrations were: 286.8 ± 10 and 578.6 ± 10 ppm. The pulses of two 3He detectors in the reflector region were summed and inserted into the IPEN/MB-01 Correlator and the APSD (Auto Power Spectral Density) was inferred through a mathematical model. The analysis reveals that the APSD in this frequency range is best described by a four-mode decay model. According to the two-region two-group (thermal and fast) kinetic model developed in this work, the first two decay modes describe the thermal group and the other two describe the fast group. After a tedious and severe analyses of the least-square fit of the experimental data, it was concluded that the kinetic behavior of the thermal and fast neutrons can be considered uncoupled. The analysis of the experimental data is still in progress and only the thermal group of the case of 286.8 ppm of boron was analyzed and some parameters could be inferred. The most important one so far is the prompt neutron generation time in the core region that could be inferred with a good level of accuracy.

Highlights

Reactor noise applications in research reactors have enjoyed a long history in the reactor physics field [1,2]
Several studies performed at the IPEN/MB-01 research reactor facility indicate that its core is more appropriately described by a two-region model as proposed by Spriggs [3]
The experiment for the APSD measurements at high frequencies has been successfully performed at the IPEN/MB-01 reactor

Summary

INTRODUCTION

Reactor noise applications in research reactors have enjoyed a long history in the reactor physics field [1,2]. The noise measurements are performed up to 10.0 kHz. Several studies performed at the IPEN/MB-01 research reactor facility indicate that its core is more appropriately described by a two-region model as proposed by Spriggs [3]. Several studies performed at the IPEN/MB-01 research reactor facility indicate that its core is more appropriately described by a two-region model as proposed by Spriggs [3] Several parameters such as βeff [4] and subcritical reactivities [5] were measured employing this two-region model. The experimental data can be very useful to infer important quantities of the interest to the reactor physics field such as subcritical reactivity, neutron lifetimes and generation times in the core and in the reflector regions. A complete description of the IPEN/MB-01 core can be found elsewhere [6]

THE MEASUREMENT APPROACH

THE TWO-GROUP AND TWO-REGION NEUTRON KINETIC MODEL

Reflected Core Equations in the Thermal Group

CONCLUSIONS