Mochovce NPP – Replacement of H3BO3 Concentration Analyzers

In 2015, a contract for the replacement of boric acid (H₃BO₃) analyzers on Mochovce NPP Units 1 and 2 was concluded with Slovenské elektrárny, a.s. The existing analyzers – boron meters – were obsolete, with no possibility of getting spare parts. New solution was based on the delivery and installation of I&C Energo a.s.’ own boron meters, type BorAn PN160. Production took place until July 2016. Installation took place during individual outages in the course of 2017.

Boron meters continuously measure the concentration of the isotope of boron ¹⁰B in reactor coolant of the nuclear power plant. Based on the known composition of boric acid, the measured value can also be presented as the concentration of boric acid.

The implementation of the work on one unit consisted in the replacement of two single-channel and two two-channel suspension boron meters on the existing technological pipeline with a diameter of 108 mm. Two-channel boron meters are installed in the air-tight zone.

To monitor the concentration of boric acid in the reactor, a single-channel flow boron meter was installed on each unit. In order to avoid potential rupture of the water column, which occurred with the original solution and due to which the operator did not have information about the concentration in the reactor, an industrial peristaltic pump was installed upstream of the flow boron meter, which ensures a continuous flow of 75 l/h at a low (approximately 10.5 m) and a high (approximately 21 m) level in the reactor.

Boron meters are installed in the technology, including sensors of basic quantities – detection of the pulses of slow neutrons, corresponding to the concentration of boric acid; temperature of the coolant at the point of measurement of pulses and measurement of flow using a flow boron meter. All signals are carried to the evaluation unit of the appropriate channel of the boron meter.

Boron meters are connected to each other via RS485 data communication to the Boron Meter Control and Diagnostics System, which ensures the servicing, archiving and calibration functions of the boron meters. The Boron Meter Control and Diagnostics System is implemented by a Simatic system.