Supervision and Safety of Complex Systems

Chapter 12SVM Time-Frequency Classification for the Detection of Injection States ¹

 

 

 

12.1. Introduction

When the British fast neutron reactor Prototype Fast Reactor (PFR) ceased operation in 1994, a number of end of life tests were carried out. In particular, this included leak detection system (LDS) tests examining the acoustic detection of water leaks into the sodium of the steam generators (SGs). In this chapter, we study the use of the acoustic detection method on a series of recordings from LDS5 tests that involves injecting argon, hydrogen, and water into the PFR’s third evaporator (EV3). The aim is to create an approach that provides an alternative to current chemical methods.

These recordings have been studied by the CEA (the French Atomic Energy agency). They present a significant low-frequency attenuation that is presumably caused by bubbles during the injection, although this statement cannot be proved due to electrical interference. Unsupervised classification was also carried out that proved the frequency band of 200 — 1,000 Hz to be optimal for detection but that did not enable the complete characterization of the sodium—water reaction. Therefore, other criteria are needed to make passive acoustic detection reliable.

In this chapter, we will study 32 series of acoustic recordings sampled at f_s = 2,048 Hz taken using accelerometers placed at the end of the wave guides in the third secondary circuit’s evaporator of the PFR. The first 15 series are injections of ...