ACCIDENT AND POST-ACCIDENT MONITORING SYSTEM

The PAMS accident and post-accident monitoring system is intended for monitoring of safety parameters and state of reactor facility’s systems during design and beyond-design accidents at NPPs.

PAMS implements functions of accident and post-accident monitoring at any design-relevant initial events, as well as beyond-design accidents (including those connected with severe damage of fuel).

Functions of PAMS:

• monitoring the following RF parameters with the use of emergency measuring instrumentation (AKIP):

• level of coolant in a reactor – for level measuring thermoelectric transducers, located inside a case of an in-core direct charge detector assembly, are used;
• level in a cooling pond – for level measuring sensor elements, based on the impulse reflectometry principle, are used;
• temperature in a cooling pond – for temperature measuring temperature transducers with the measuring range 0 - 300 °С are used;
• temperature in a containment – for temperature measuring resistance thermometers with the measuring range 0 - 300 °С are used;
• containment radiation dose rate – for monitoring of radiation dose rate detection units (ionization chambers) with the measuring range 10^-4 - 10⁵ Gy/hour are used;
• pressure above a core – for pressure measuring pressure sensors of 0 - 25 MPa are used;
• pressure in an accident confinement area – for pressure measuring pressure sensors of 0 - 1 MPa are used;
• level in containment sumps – for level measuring differential pressure sensors of 0 - 70 kPa are used;

• providing operating personnel of NPP and emergency work headquarters with information on state of main safety functions and reactor facility’s systems with the help of PAMS hardware resistant to emergency conditions, as well as data received from standard systems if they keep their operability;
• providing information on state and efficiency of protective barriers based on direct readings of AKIP when standard monitoring systems fail during beyond-design accidents;
• PAMS data transferring into the “Black Box” system and crisis centres.

Composition of PAMS:

• upper level of PAMS – MSKU industrial controllers and panel computers qualified according to application conditions;
• lower level of PAMS - emergency measuring instrumentation qualified for conditions of design and beyond-design accidents.

System advantages:

• high failure tolerance due to use of a distributed two-level structure with the use of two independent channels of data measuring, processing and displaying;
• use of hardware qualified for conditions of design and beyond-design accidents, including loss of coolant accidents (LOCA);
• use of AKIP with an advanced measurement range of monitored technological parameters of RF;
• assurance of PAMS operability under conditions of a maximum design earthquake and full blackout of a unit;
• reliable power supply of PAMS equipment due to use of a UBP-15 uninterruptible power supply assuring power supply for PAMS in case of unit blackout for a time period up to 8 hours.

Safety class – 3.
Safety category – В.

Implementation facilities:

• Zaporizhzhya NPP, units 1, 2
• Rivne NPP, units 1-4
• Khmelnitsky NPP, units 1, 2