Summary Report for Conduct of Kozloduy NPP Stress Tests

“Kozloduy NPP” PLC
SUMMARY REPORT
for Conduct of Kozloduy NPP
Stress Tests
Initiating
event
Option
and use of reserve in the boron control system tank)
6 Loss of primary circuit cooling due to failure of emergency
and planned cooldown system during the mode of outage
cooldown of the primary circuit
(Considered: drainage of ECCS three hydro accumulators
and use of reserve in the boron control system tank)
3 days after shutdown 25:51 h
18 days after shutdown 50:12
Time to fuel
damage
5.1.3.4 Loss of ultimate heat sink, in combination with station blackout (i.e. loss of off-site
and emergency power supply to the site)
Simultaneous loss of power supply and ultimate heat sink is considered as:
· Loss of off-site power supply and all the stationary AC sources at the NPP site
(emergency and additional DGs);
· Loss of main ultimate heat sink, defined as loss of Danube river water intake
structures.
to:
As a result of postulated off-site initiating event it is assumed that loss of operability occurs
· Open switchyards of Kozloduy NPP;
· Emergency DGs;
· Additional DGs;
· Bank pumping stations and their structures, including DG;
· Shaft pumping station.
For accident management the following can be used
· Mobile DG and their powered facilities;
· Emergency water volume in the cold channel;
· Pumps with own diesel motor, including fire-protection ones;
· Category І loads of the power supply to discharging of the SS accumulator batteries;
· Manually-operated valves;
· Other structures operation of which is not affected by the initiating event.
5.1.3.4.1 Time of independence of the site before fuel damage occurs due to loss of primary
circuit water
Below response of power units 5 and 6 is described at different operational conditions.
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