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| Program name | Package id | Status | Status date |
|---|---|---|---|
| ZZ-BWRSB-FORSMARK | NEA-1551/01 | Arrived | 12-FEB-2002 |
Machines used:
| Package ID | Orig. computer | Test computer |
|---|---|---|
| NEA-1551/01 | Many Computers |
The purpose of this benchmark is the intercomparison of the different time series analysis methods that can be applied to the study of BWR stability. This is a follow-up benchmark to the Ringhals 1 Stability Benchmark. While the Ringhals 1 Stability Benchmark included both time domain and frequency domain calculation models to predict stability parameters, the new benchmark is focused on the analysis of time series data by means of noise analysis techniques in the time domain.
The first goal is to elucidate if it is possible to determine the main stability parameters from the neutronic signals time series with enough reliability and accuracy. Typically, the main stability parameters are assumed to be the decay ratio (DR) and the frequency of the oscillation. However, there are other parameters that provide valuable information, such us the Lyapunov exponents associated to the time series, or the Haussdorff dimension. In fact, the Lyapunov exponents are also a measure of the stability of the neutronic time series.
The data given in this benchmark were obtained during several stability tests performed at the Swedish BWR reactors Forsmarks 1 and 2, in the period 1989 to 1997.
The database is divided into six cases, the sampling rate of all the time series being 25 Hz, decimated to 12.5 Hz. The data are stored column wise in ASCII format. No filter to the signals and the DC-component has not been subtracted.
CASE 1: This case contains the neutron flux signals measured during several tests. The objective of the case is to study several signals ranging from stable to quasi-unstable conditions. The signals are standard measurements with no distortions. Data contains measured APRM (Average Power Range Monitor) signals from stability tests. The signals are measured at conditions with low Decay-Ratios up to high Decay-Ratios.
CASE 2: This case addresses the importance of the time duration of measured data. The objective of this case is to study the variability of the DR and oscillation frequency with the measurement time duration. There are two time series to analyse. Each one has about 14000 points and will be divided in blocks of approximately 4000 and 2000 points. The results for the short time series will be compared with the original long series results.
CASE 3: APRM data for this case contains more than one natural frequency of the core. The data also contains peaks of other frequencies due to the actuation of the pressure controller. One case has two frequencies close to each other. Cases with more than one natural frequency make the analysis much more difficult. This case contains five measurements contaminated with influences from the plant control systems. In this case, the time series have a bad behaviour, and consequently the standard stability parameters are not clear. It could then be interesting to analyse a set of the dominant poles of the transfer function obtained from the time series.
CASE 4: This case contains a mixture between a global oscillation mode and a regional (half core) oscillation. The case consists of APRM and LPRM (Local PRM) signals coming from one test.
CASE 5: This case is focused on the analysis of two APRM-signals obtained during a small plant transient, that resulted in a bad behaviour of the signals. In this case, it is important to analyse the first dominant poles of the transfer function obtained from the time series. Note that this is a non-stationary case, and the autoregressive methods have a limited validity.
CASE 6: This test case shows local (channel) oscillations. The data contains APRM and LPRM signals from two tests that were performed close to each other, both in time and in the operating conditions.
Tomas Lefvert:
Proposed Benchmark for Core Stability Evaluation Methods presented at the Eighth Nuclear Science Committee Meeting 9-11 June 1997 FTT-A1200/PAK (May 1997)
G. Verdu, M.J. Palomo, A. Escriva
Department of Chemical > Nuclear Engineering
Polytechnic University of Valencia
P.0. Box 22012
46071 Valencia, Spain
D. Ginestar
Department of Applied Mathematics
Polytechnic University of Valencia
P.0. Box 22012
46071 Valencia, Spain
Released by:
Per Lansaker
Vattenfall
Forsmarksverket
S-74203 OESTHAMMAR, Sweden
Keywords: BWR reactors, reactor stability.
