Summary Report for Conduct of Kozloduy NPP Stress Tests

“Kozloduy NPP” PLC
SUMMARY REPORT
for Conduct of Kozloduy NPP
Stress Tests
In the oil stocks at the site of Units 5 and 6 emergency inventory (in two tanks with capacity
per 2000 m3) ensuring additional operation of all simultaneously during 7 days is stored. The oil
inventories (operational and backup) are sufficient for the diesel-generators operation during 20
days, according to item 4.3.1.5 of [45].
The mobile diesel-generator is designed to ensure power supply of alternative pumps for
steam generators makeup water pumps. The mobile diesel-generator can power only one out of two
pumps (that of unit 5 of unit 6). The fuel tank has capacity of 3,5 m3. The maximum flow-rate of
the fuel is about 320 l/h. With this flow-rate the inventory in the tank located on the platform is
sufficient for about 11 hours’ continuous operation.
DC power supply systems of safety systems (I, II and III trains) are located at elevation
20,40 and are not affected by MWL. According to the data from technical tests, the batteries last
over 10 hours with real load without degradation.
3.2.1.3 SFS
3.2.1.3.1 Major SSCs
In definition of critical SSCs documents [26],[107], and from [109] to [113] inclusively
were considered.
The system for filling, makeup, transfusion and emptying of the fuel storage pools is
determined as critical SSCs due to the requirements of item 5.5.2 of [26]. The ventilation systems
are determined as critical SSCs due to the requirements of item 5.8.1 of [26] and [113]. The power
supply system is determined as significant SSCs due to the requirements for the ventilation systems
as well as due to item 5.9.2 of [26].
3.2.1.3.2 Protective measures for maintaining cooling water supply
According to the defined SSCs the spent fuel compartments cooling system is not of interest
for safety margins reassessment as according to [26], it may remain inoperable for up to four days,
besides item 6.5.1.2 [25] stated that normally fuel storage pool cooling system operation is required
for one week per month.
3.2.1.3.3 Protective measures for maintaining emergency power supply
For power supply or category 1 and 2 equipment a complete two-transformer substation
with dry transformers with capacity of 630 kVА and two-section switchgear with redundancy
between the sections is provided. The substation power supply is by two independent cable lines
from 6 kV sections of units 3 and 4.
3.2.1.4 DSFS
3.2.1.4.1 Major SSCs
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