Nuclear fuel is a very efficient source of energy, nevertheless, it is a hazardous substance, whose handling requires strict safety regulations. Although the production process itself, especially the fission reaction, is a well mastered technology nowadays, there is still a risk of leakage of radioactive substances. In order to minimize the risk to public and the employees, virtually all nuclear power plants worldwide build systems to monitor presence of radioactive substances as well as associated warning systems. The purpose of these systems is to deliver a warning message to all employees and residents of the threatened areas in the event of an emergency.  Warning and monitoring systems must be designed to be extremely reliable, resistant, and, particularly, operable even from the physically remote backup control centres, in order to be used in emergency situations when it is necessary to evacuate the operational control departments.
 

Warning system for nuclear power plant is designed to meet all requirements for reliable operation in demanding conditions typical for nuclear power plants. This particularly includes the possibility of its control from two independent and physically remote control centres, one hundred percent backup of the key communication elements and provision of information regarding operation of all major components:  sirens, centres, communication units, speakers, amplifiers, communication modems, antenna systems, power supplies, batteries etc. and individual system elements. The main elements of the warning system for nuclear power plants proposed by Telegrafia a.s.:

• main dispatching centre;
• backup dispatching centre;
• radio communication infrastructure;
• PAVIAN electronic sirens for external sound distribution;
• AMADEO radio units for interior sound distribution;

At the same time the system is connected to its superior state or municipal public address system via both sirens and control centres. Sirens or groups of sirens can also be controlled locally, i.e. from local control units. This functionality is mainly designed for municipalities. Moreover, it enables to control the internal visual warning system of the nuclear power plant.
 

• extremely reliable and safe solution;
• physically divided dispatching centre and the emergency control centre;
• extremely short activation times and activation confirming times for large number (hundreds) of sirens;
• reliable sound distribution in the interiors with many partitions;
• maximum automation of the announcement-following processes (automatic calling in the people in charge, informing the institutions involved etc.);
• effectivity of the invested money and good ratio between the costs and the received value

Key: 1. main dispatching centre, 2. backup dispatching centre, 3. main communication transmitter, 4. backup communication transmitter, 5. local communication units, 6. interior sound distribution of the power plant, 7. competent persons to be notified

Main dispatching centre
The dispatching centre is used for the following:

• It continuously monitors the status/functionality of the entire warning system at the dedicated radio frequencies;
• It monitors the progress of specific parameters of the technological process (autonomous monitoring system);
• In the case of critically increased levels of the parameters in question the centre activates relevant acoustic and optical warning systems;
• It activates the notification process i.e. calling in the people in charge of the workplace in case of emergency and informs the relevant institutions when such event occurs;
• It is connected to the external state public address system, to which it provides the information on the system status;
• It records control centre communication for future analysis;

It consists of:

• A computer with VEKTRA Enterprise edition software;
• Large display table;
• Additional notification and recording modules;
• Computer equipped with control and service software; 

Backup dispatching centre
The emergency control centre is equipped with the exactly same technology as the dispatching centre and they run simultaneously. This centre, however, is not used to control. It is in so called “interception” mode and it can overtake the system control, both automatic and manual if necessary or in the case of the dispatching centre failure.

Communication infrastructure
The communication infrastructure consists of the main transmitting unit, emergency transmitting unit and local transmitting units. The main transmitting unit communicates with local units and with sirens within its reach. The local communication units communicate with the sirens in the selected locations and they mainly function as a concentrator to shorten the response time of the entire system. The applied radio protocol and communication algorithms are optimized in order to maximize reliability, and to minimize activation message delivery time and activation confirming time. The emergency communication unit functions as the main communication unit if required. The sound is distributed within the internal premises using AMADEO radio controlled units. As for the interior with many partitions, the radio signal is transmitted to AMADEO radio units using a special radiating cable-based aerial system. This aerial system is also used for common radio communication using radio stations. Another control channel of the warning system is the RDS channel designed to activate the superior state public address system.   

PAVIAN electronic sirens
PAVIAN electronic sirens are used as terminal acoustic elements for nuclear power plant external broadcasting, i.e. to warn the nearby people, using all the auto-testing functions and modules in order to maximize the reliability of the sirens in case of emergency.

AMADEO radio units
AMADEO radio units are used to broadcast in the internal premises of the plants. This system also uses third party radio units, to which it is connected via a special interface. Just like the PAVIAN sirens, the AMADEO radio units are also equipped with auto-testing functions and modules. In addition to that a visual warning system is connected to the radio units.