Operational experience with neutron power on-line calibration system AKE-02R at Bohunice NPP

M. Závodský, K. Klučárová, VUJE Inc., Slovakia

20th Symposium of AER on VVER Reactor Physics and Reactor Safety (2010, Hanasaari, Espoo, Finland)
Core Monitoring


Ex-core neutron flux measurement system was modernized at Bohunice NPP in period
2007-2008. The previous system AKNT-2 was replaced by new system AKNT-17R. In spite
of the new modern system, neutron flux measurement accuracy is still influenced by the
changes of various parameters: control assemblies group 6 position, coolant temperature at
reactor inlet, power distribution in reactor core change because of fuel burn-up, etc. Therefore
AKE-02R system (neutron power on-line calibration system) was installed at Bohunice NPP
in 2008 and 2009. AKE-02R system was working in open-loop mode more than one year and
finally at the end of 2009 (Unit 3) and at the beginning of 2010 (Unit 4) was switched into
close-loop mode.
The purpose of AKE-02R system is to increase ex-core neutron power measurement
accuracy. AKE-02R system eliminates above mentioned dependencies by using correction
factors, determined on the basis of real control assemblies axial position, real coolant inlet
temperature and real burn-up. Correction factors are continually calculated in AKE-02R
system and next enter into AKNT-17R system. New corrected value of neutron power is
computed in AKNT-17R system by using correction factor. Corrected value of neutron power
is used as input value for all other systems (reactor control system, reactor trip system, reactor
limitation system, etc.).
In this paper brief description of AKNT-17R system and AKE-02R system is
presented. The process of commissioning of AKE-02R and also the results of tests are
explained. Operational experiences with AKE-02R system after switching into close-loop
mode are showed.

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