NEUTRON FLUX MONITORING SYSTEM

The AKNP-IF neutron flux monitoring system is a part of a control and protection system (SUZ) of NPP units.

Functions of AKNP-IF:

• monitoring, continuously registering, and archiving current values of reactor relative physical power, velocity (period) of its change, and reactivity;
• generating discrete signals on exceeding emergency and preliminary protection setpoints, setpoints of control and regulation by relative physical power and period for SUZ and unit’s I&C subsystems;
• presenting analog and discrete signals in the optical and acoustic form to operators of main, backup control rooms and a fuel reload machine, to operating personnel;
• automatically correcting neutron power measurements taking into account thermal physic and other parameters characterizing state of a reactor facility;
• monitoring fixation of in-core devices by results of neutron detector signal fluctuation analysis;
• monitoring subcriticality of a reactor facility.

Composition of AKNP-IF:

• two sets of AKNP-IF APZ-SKP for SUZ and a main control room;
• one set of AKNP-IF BCR for a backup control room.

Each set includes three independent channels of neutron flux monitoring. Each neutron flux monitoring channel consists of:

• detection devices containing:

• detection units based on ionization chambers (for startup and operating ranges), on boron or helium corona radiation-resistant highly sensitive neutron counters (for an SKP fuel reload monitoring system);
• amplification and digital conversion units;

• an accumulation and processing device;
• a device for input of power setpoints;
• registration and display units for a main control room and a fuel reload machine panel to display and archive current parameters, as well as to transfer information to unit’s adjacent systems – common for three neutron flux monitoring channels.

Detection unit for start-up and working rangesв		Detection unit for SKP

System advantages:

• automation of calibration of neutron flux density monitoring channels during operation of AKNP-IF using a metrologically certified reactor kinetics simulator developed by SRPA “Impulse” (signals are simulated in a whole range of neutron flux monitoring without necessity of access to sensors in a restricted zone);
• high accuracy due to use of highly sensitive boron and helium neutron sensors;
• integration of a fuel reload monitoring system into AKNP;
• absence of influence of residual readings of detection devices after power operation due to use of fluctuation mode of an ionization chamber;
• possibility of operational calibration of power readings in MCR with automatic recalculation of calibration coefficients;
• high fail-safety of the system due to use of redundant hardware and diverse software.

Safety class – 2.
Safety category – А.

Implementation facilities:

• Zaporizhzhya NPP, units 1-6
• Khmelnitsky NPP, units 1, 2
• Rivne NPP, units 1-4
• South-Ukraine NPP, units 1-3
• Armenian NPP, unit 2