Investigation of I

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Investigation of IC components at Kernkraftwerk
Mühleberg during operation and outage with the
aid of signal analysis.Part I Bengt-Göran
BergdahlGSE Power Systems AB, Swedenbengt-goran.
bergdahl_at_gses.se
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• 350 signals are measured every cycle
• The analysis started in 1994
• The analysis results are stored in a data base
  called SensBase
• The nuclear power inspectorate in Switzerland has
  accepted an extended calibration interval as a
  result of the analysis

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Signal analysis of IC components at KKM, a GE
type BWR in Switzerland

• An independent method to observe dynamic
  deviations in the components like e.g.
• Filtering in IC response time
• Transmitter errors
• Increased signal noise in the IC component
• Static deviations
• Changes in IC calibration can also be observed
  with the analysis

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Storage of analysis data in SensBase

• Short time series 30 seconds
• APSD (Auto Power Spectral Density)
• Histogram with Mean Value, Standard Deviation,
  Skewness and Kurtosis
• Time constant, estimated with an identified model
  of the component
• Multiple sensor information in the time domain
  with Gain, Offset and Amplitude Ratio

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The input signal Xi and output signal Xo. Then
the residual Xr is based on the least square
fitting. Xo Kg Xi Ko where Kg Gain Ko
Offset The error of the output signal Xr gives
with the use of Kg, Ko the following
expression Xr Xo Kg Xi - Ko If the signals
are identical, the Gain and Offset will adopt the
following values Kg 1 and Ko 0 Ar (Amplitude
ratio). The unit is in () and the function is
defined by Ar 100 std(Xr)/std(Xo), where std
standard deviation
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23 different systems each with a GUI in SensBaseTM
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Gain, Offset and Amplitude ratio for 4 pairs of
reactor pressure sensors.MP34B2 was taken to
service in year 2000. Observe that the parameters
are normal in year 2001.Transmitter error!
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Process identification
x(t) Input
y(t) Output
Process
Output

Corr. of parameters
-
Output estimation
Model
x(t) Input
y(t) Output
Output estimation
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Reactor water level instrument in a BWR
P-transmitter
P
Level
Density converter
DP
DP-transmitter
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Time constant 80 ms Gain 1.4
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A2, B2 inputs and B-U01 output,analyzed with a
MAR (Multiple Auto Regressive) Model
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Time constants for the summation and isolation
amplifier units
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Observed deviations at KKM with SensBase
technique.
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Turbine controllers at KKM
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Test of the control system in closed loop
Steam pressure