Neutronic signal conditioning using a singular system analysis G. Verdu a, *, D. Ginestar b a Departamento de IngenierõÂa QuõÂmica y Nuclear, Universidad Polite Âcnica de Valencia, Camino de Vera 14, 46022 Valencia, Spain b Departamento de Matema Âtica Aplicada, Universidad Polite Âcnica de Valencia, Camino de Vera 14, 46022 Valencia, Spain Received 19 May 2000; received in revised form 21 June 2000; accepted 22 June 2000 Abstract In this paper, we mix two approaches, the standard methodology and the dynamics recon- struction theory to calculate the stability characteristics of BWR neutronic signals. We review the singular system analysis (SSA) methodology considering the continuous and discrete case, focusing our attention on oscillating signals. We analyze analytic and real neutronic signals, showing that the use of SSA methodology improves the decay ratio calculations. # 2001 Elsevier Science Ltd. All rights reserved. 1. Introduction Although some authors advocate for a reconsideration (Konno et al., 1999; Van der Hagen et al., 2000), the decay ratio (DR) calculation is widely used as a method to study the stability characteristics of a BWR nuclear power reactor. Recently, two instability benchmarks have been devoted to the study of BWR reactors stability regime (Lefvert, 1996; NEA, 1999). Particularly, the Forsmark 1 and 2 Stability Benchmark was devoted to the revision of neutronic signals analysis techniques for the estimation of the decay ratio and the frequency of the oscillation associated with in-phase and out-of-phase instabilities. One of the conclusions obtained from this benchmark is the large variability on the DR determination, mainly in non stationary situations or when the neutronic signals are aected from external contributions as the electronics or the pressure controller. Annals of Nuclear Energy 28 (2001) 565±583 www.elsevier.com/locate/anucene 0306-4549/01/$ - see front matter # 2001 Elsevier Science Ltd. All rights reserved. PII: S0306-4549(00)00073-6 * Corresponding author. Tel.: +34-9-6387-7635; fax: +34-9-6387-7639. E-mail address: gverdu@inq.upv.es (G. VerduÂ).