Original scientific paper

Krško NPP Experience with RTD Bypass Elimination

Gordan Janković ; Nuclear Power Plant Krško Vrbina 12, 8270 Krško, Slovenia

Abstract

This paper describes Krško experience and problems that had to be resolved with RTD
Bypass Elimination project (RTDBE). Following RTD bypass manifold isolation valve leak in
2008, Krško decided to perform RTDBE modification on reactor coolant system narrow range
temperature measurement system. The installation was performed during Outage 2013. Soon after
the plant returned to power, newly configured measurement channels showed that OPΔT reactor
trip was oversensitive to spikes caused by auxiliary relay operation in the cabinets nearby. The
solution was to reconfigure OPΔT trip filtering constants to filter out short-term spikes in the signal.
After almost full operating cycle of trouble-free operation, RTD failures started occurring on reactor
coolant system cold leg, which was caused by the high frequency vibrations (3-5 kHz) induced by
reactor coolant pumps. To resolve RTD failures, Krško ordered re-design of the RTDs to add
robustness and specific qualification in high-frequency vibration operating environment. Improved
RTDs were installed in Outage 2016 and were operating one full cycle with minor deviations.

Keywords

RTD, RTDBE, high-frequency vibration, reactor coolant pump

Hrčak ID:

247091

URI

https://hrcak.srce.hr/247091

Publication date:

28.10.2019.

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