atw 2018-09v3

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atw Vol. 63 (2018) | Issue 8/9 ı August/September

OPERATION AND NEW BUILD 454

tail distribution. High but short peaks

and low prob ability are mostly responsible

for the activation of the power

limitation function of the digital I&C

system. Probability density function

(e.g. Generalized Extreme Value GEV

a)

[6]) and fits of measured parameters

were calculated in an attempt to

predict maximal values and frequency

occurrences of the measured neutron

flux [3], which are of relevance for

operational core control.

Although ex-core raw signals

from the ionisation chambers are

electro­nically filtered in the signal

processing, high amplitude noise are

nevertheless registered with a certain

low residual probability of triggering

b)

| | Fig. 4.

Radial cross-correlations of the four ex-core detectors (a) and axial cross-correlations of in-core detector G02 (b) measured on 18.12.2014.

a)

| | Fig. 5.

Probability Density Functions (PDF) a) and probability distribution b) of in-core detectors at position J14 and position G02 axial level 5. The signals are fitted with

the Generalized Extreme Value (GEV) and Gauss functions (b). GEV fit is well suited for asymmetric distributions as observed at certain core positions in KKG.

b)

a)

| | Fig. 6.

Signal sample from vertical movement detector A1 located on the reactor pressure lid of the oscillation surveillance system (SÜS) recorded at MOC (a) and

probability distribution of two absolute position sensors at MOC (b).

b)

Operation and New Build

Detailed Measurements and Analyses of the Neutron Flux Oscillation Phenomenology at Kernkraftwerk Gösgen ı G. Girardin, R. Meier, L. Meyer, A. Ålander and F. Jatuff

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