Safety is a top priority and a leading corporate value in Kozloduy NPP.
The nuclear facilities are operated while strictly observing the conditions of the licences issued by the NRA, the requirements of the technical specifications, and the operating procedures.
COMPANY'S OBJECTIVES FOR SAFETY MANAGEMENT
- ensuring nuclear safety
- effective protection of the personnel, public, and environment against the harmful impact of ionizing radiation;
- safe management of fresh and spent nuclear fuel;
- safe radioactive waste management;
- continuous safety culture enhancement.
Technological safety is inherent in the design through a set of control and protection systems which ensure the safe operation of the facilities from their design stage.
Defence-in-depth is the main principle, applied by Kozloduy NPP and by all nuclear power plants around the world. This means that the functions of each safety system are furnished with backup equipment and alternative systems capable of supporting the control of processes in the nuclear facilities in a timely manner.
One of the main issues related to the nuclear power plant safe operation is preventing the spread of radioactive products generated as a result of nuclear fission and contamination of coolant to the environment.
This is ensured through the use of the following physical barriers:
- Fuel pellet matrix;
- Fuel elements cladding − fuel pellets in metal coating; in this way the fuel and nuclear reaction products remain tightly sealed throughout the whole fuel cycle;
- Reactor pressure vessel and primary equipment − the walls of each reactor are made of special steel alloy resistant to neutron flux, high pressure, and thermal effects. The third barrier includes also the pipelines and the equipment of the coolant circuit;
- Containment – the reactor and a significant part of the equipment are placed under a special dome built of reinforced concrete.
Apart from the physical barriers, a hierarchy of different levels of equipment and procedures has been developed to preserve the effectiveness of the physical barriers in normal operation, anticipated transients, and in case of emergency.
The safety systems have a major role in accident prevention and mitigation through a set of technical means. They enable safe reactor shutdown and maintaining it subcritical, reactor coolant circuit cooling, decay heat removal, and maintaining radioactive substances within the set limit values.
In order to reduce the probability of common cause failure of several systems important to safety, the following principles are applied separately or in combination:
- passive operation;
- independence – functioning of one system should not depend on the operation of another;
- redundancy – use of supplementary systems or components for ensuring additional possibility to perform safety functions;
- separation – structural, functional and physical separation of the safety trains;
- diversity (variation) – protection of systems and components which perform the same task by means of various structures, operating principles, etc.
All aspects of activities performed by Kozloduy NPP serve to achieve the key priority objective of continuous safety enhancing as well as upholding and developing strong safety culture.
The scope of safety covers all the activities related to the operation, maintenance and inspection of the facilities. Strict procedures and rules for providing radiological protection are applied. The personnel undergo initial and continuing training in order to ensure their high qualification. Before obtaining a licence issued for work in Units 5 and 6 control rooms, the nuclear operators undergo specialised training for a period of at least 3 years after graduating their university courses. The power plant has a full-scope simulator for WWER-1000 type of reactors where operators work in conditions fully identical to real work conditions.
The continuous process of learning lessons from operating experience is of great importance. Kozloduy NPP performance, as well as events occurring at other nuclear power plants are analysed and assessed.
SAFETY AND REGULATORY REGIME
Safety is continuously monitored and assessed through a graded approach by means of regular self-assessments, safety assessments performed by an independent regulatory body (the Nuclear Regulatory Agency), numerous peer reviews and missions conducted by the World Association of Nuclear Operators (WANO), the International Atomic Energy Agency (IAEA), and the European Commission.