BN-600 operating safety enhancement

While the reactor has been in operation more stringent regulatory codes and rules for nuclear reactor safety have been adopted. In this coimection a special review was carried out to assess the compliance of safety-related systems and components with the up-to-date regulatory requirements. Discrepancies were identified and corrective measures were developed. 

Analysis carried out to assess the actual seismic stability of the plant buildings, structures and systems showed that under seismic impact of magnitude 6 destruction of parts 

A special building will be built for the DHRS air coolers. The stem is planned to be  

Installation of a stand-by control board in the DHR air cooler building is planned. From it the reactor could be shut down and cooled under reliable control if the nuun control room were to be lost. Pending realization of this modification a procedure has been developed for cooling the reactor down from the local control panels, and for controlling the reactor in a subcritical state from a room which functions temporarily as a stand-by control board. 

To limit the scope of possible leaks of sodium from the external primary coolant systems additional jacketing was provided for pipelines to the second isolation valves including the valve casings. Similar measures with installation of an additional valve are planned for the spent fuel drum cooling system to prevent failure due to faults or leaks in the isolation valves. Passive safety devices (hydraulic seals) are installed for overpressure protection of the drum s main and guard casings. 

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