Summary Report for Conduct of Kozloduy NPP Stress Tests

“Kozloduy NPP” PLC
SUMMARY REPORT
for Conduct of Kozloduy NPP
Stress Tests
SCR (Standby control room) is intended, in case of failure to the MCR, for reliable transfer
of the unit in undercritical cold condition and for maintaining the unit in that condition for unlimited
time, for actuation of the safety systems and for receiving information on condition of the reactor.
SCR is located at elevation of -4.20 in reactor compartment. The premise of the standby
control room is assigned category I of the seismic stability. Design accidents related to loss of
coolant do not affect the MCR. As a result of analyses of the beyond design seismic impacts the
civil structure of the SCR and adjacent premises maintains its integrity. At analyses of beyond
design combined impacts of the earthquake and off-site flooding is possible - the SCR will be
flooded. At analyses of the beyond design impacts of off-site flooding it is possible that the adjacent
premises of the SCR are flooded what will hinder access to the premise.
6.1.3.3.2 Feasibility and efficiency of measures for accident management in conditions of offsite
hazards (earthquake, flooding)
The design of Units 5 and 6 of Kozloduy NPP is robust to impacts of the off-site hazards.
The reactor and the main structures of the primary circuit are located in the reinforced concrete
containment, intended to localize radioactive products after accident in its own space which is
qualified for seismic impacts of 0,2 g [7], [8].The main systems and components of the safety
systems and these safety-related systems also are located in buildings qualified for seismic impacts
0,2g [7], [8]. Analyses of beyond design seismic impacts show that to seismic impacts 0.36 g
structures with which accident management are provided, are available. At analyses of beyond
design combined impacts of the earthquake and off-site flooding it is shown that safety functions
are performed of units 5 and 6 with survived equipment. At analyses of beyond design impacts of
the off-site flooding it is shown that systems and equipment required for performing safety
functions, are not affected.
Personnel of Units 5 and 6 takes measures in accordance with Emergency procedures of the
units to shut down the reactor and maintain it in safe condition. In parallel with the emergency
procedures of Units 5 and 6, on-site and off-site emergency response plan will be initiated
according to Appendix 3.2 of [28].
6.1.3.3.3 Unavailability of the power supply
Impacts of unavailability of the power supply to Units 5 and 6 of the Kozloduy NPP were
analyzed within assessment of loss of power supply and loss of ultimate heat sink. All the options
were assessed of sequential loss of sources of electric power supply. Virtually availability of
equipment is reduced for accident management, but the design has available sufficient standby
power supply sources, actuation of which leads to restoration of the equipment required for accident
management. Recovery operator actions are described in the Emergency procedures.
6.1.3.3.4 Potential failure of measurement instrumentation
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