Summary Report for Conduct of Kozloduy NPP Stress Tests

“Kozloduy NPP” PLC
SUMMARY REPORT
for Conduct of Kozloduy NPP
Stress Tests
For the degree of piling with debris of 100% results of calculations with conservative
assumptions show that the maximum temperature of the cladding may be only exceeded
accordingly after more than 2 or 3 days.
Considering the structure of the roof a realistic degree of burial with 50% confidence should
be anticipated. This increases the time available for countermeasures to more than 7 days. Even for
this worst case scenario of an accident with loss of heat removal there is sufficient time available to
take adequate countermeasures, i.e. to remove the debris and restore natural ventilation.
2.7.3.2 Potential loss of off-site power due to destruction of the main site infrastructure
The scenario for total loss of power supply is not relevant with regard to DSFS safety. Due
to availability of passive system for decay heat removal the safe mode of the storage facility
operation does not depend on the power supply.
2.7.3.3 Other indirect impacts caused by fires, explosions, flooding
The earthquake as an initiating design basis event may cause a fire, which indicate thermal
effects on the containers.
To avoid negative effects on safety resulting from fire the following provisions are made:
· primary fire protection is provided by the design though minimizing potential
sources of ignition and fire loads.
· in case of fire occurrence the DSFS building is provided with fire detection system.
· design fire protection of the containers. The containers are designed to withstand
severe boundary accident event of a fire at a constant temperature of 600 ° C with a duration
of 1 hour while maintaining the temperature of the fuel cladding below 330° C.
In the design of containers and DSFS building scenario of an explosion of the site or an
explosion of a vehicle near DSFS is not considered. The internal explosion can be excluded since
there are no explosive materials within the facility.
The building of the DSFS storage hall is designed to withstand the pressure wave from the
explosion of a gas cloud. However, it can not be excluded that construction debris from the roof
(thin metal plates) could fall into the storage hall. The emergency procedures and instructions shall
specify the way and the process tools required for removal of the debris.
2.8 POTENTIAL DESTRUCTIONS OUTSIDE THE SITE LEADING TO PREVENTION
OR BLOCKING OF PERSONNEL OR EQUIPMENT ACCESS TO THE SITE
To take into account possible adverse effects of seismically induced damage to the national
infrastructure around the plant on its ability to maintain their safety functions after the seismic event
it is necessary to conduct studies that show when and how seismic failures and the damage can be
anticipated in it. Possible adverse effects on the plant are mainly limited to:
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