Summary Report for Conduct of Kozloduy NPP Stress Tests

“Kozloduy NPP” PLC
SUMMARY REPORT
for Conduct of Kozloduy NPP
Stress Tests
It should be noted that as consequences from destruction of the turbine hall rupture of the
pipeline connected to the SG can be anticipated, i.e. the unit will go into an accident situation with
isolable break in the secondary circuit. Termination of the leak in the secondary circuit (that ensure
termination of non-controlled cooldown of the primary circuit and prevention of potential for PTS
process) required closing of all MSIVs. The seismic impacts of this range do not affect functionality
of main steam isolation valve and the valves of its binding, due to which it can be accepted that SG
isolation will be fully successful. Due to loss of I&C equipment may require the operating
personnel to duplicate the action of the automation from MCR.
The loss of make-up and blowdown system (caused by the loss of auxiliary sections)
predetermines termination of sealing water supply to the reactor coolant pump seals. As fro this
range of the seismic impacts there is no loss of intermediate circuit system, then the primary circuit
integrity does not fail.
Therefore, to cope with the accident process performance of the safety functions of the
remaining available equipment is required.
For the overall performance of the function to ensure sub-criticality it is required that at least
one the following systems: high pressure emergency boron injection system or medium pressure
emergency core cooling system remain operable. The analysis in [44], demonstrates:
· medium pressure emergency core cooling system remains operable after the
earthquake. For Unit 5, however, only two trains of the system are available due to failure of
the first train of the essential components service water supply system;
· high pressure emergency boron injection system remains operable after the
earthquake.
It follows from the above stated that performance of the function for both units can be
ensured as due to remaining high level of redundancy.
Primary circuit heat removal function will be affected both by the earthquake and by the
flooding as:
· Seismically induced failure of the SG makeup water system due to destruction of the
turbine hall, some reduction of resources for performance of the functions before the
emergency feedwater systems and SG alternative makeup system.
· Emergency feedwater pumps fail as the result of flooding of rooms with water
supplied from adjacent rooms. this failure, however is anticipated at the accident progress
much later phase in time.
· The steam generators alternative makeup system will not be affected by the
earthquake and the water level, but movement of MDG may be hindered. The system can be
used to for makeup of only one of the two units as the power supply source MDG is the only
one at the site.
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