Summary Report for Conduct of Kozloduy NPP Stress Tests

“Kozloduy NPP” PLC
SUMMARY REPORT
for Conduct of Kozloduy NPP
Stress Tests
Option
2 Shut down reactor, planned cooldown at pressurized primary
circuit and drained SG
(Considered: drainage of three hydro accumulators)
3 Shut down reactor, planned cooldown at pressurized primary
circuit and non-drained SG
(Considered: drainage of three hydro accumulators, make-up of
SG from high pressure deaerator, chemically demineralised water
system tanks and SG emergency make-up system tanks)
4 Shut down reactor, planned cooldown at depressurized primary
circuit
(Considered: drainage of three hydro accumulators)
Time to fuel
damage
(h:min)
16:44
More than 3 days
and 19 hours
19:45
5
Shut down reactor, outage cooldown
(Considered: drainage of three hydro accumulators)
3 days after shutdown 25:51
18 days after shutdown 50:12
The first threshold is discharge of the accumulator batteries (about 10 hours after complete
loss of AC sources). As a result the shift personnel losses information on unit parameters. Before
that the valves required for accident management shall be positioned (safety valves of the
pressurize, BRU-A, steam/gas mixture emergency removal line, etc.).
However, discharge of the accumulator batteries does not terminate the started processes of
heat removal (motor-driven pumps will maintain their position).
The second threshold is water exhaust in chemically demineralised water tanks (at pump
make-up of SG auxiliary make-up system) and in the tanks of SG emergency make-up system (at
make-up using SG EMS).
At power operations exhaust of the three SG emergency make-up system tanks, of high
pressure deaerator water reserve and chemically demineralised water tank is expected after more
than 3 days.
The third threshold is exhaust of fuel oil reserve for additional and mobile DG. Fuel oil
reserve for additional DG is sufficient for more than 4 days, and for MDG – for 60 hours. Oil
reserves for both DGs are sufficient for this period of time. If emergency DGs are inoperable, oil
and fuel intended for these can be used on the operating DGs, with which their operation is ensured
for more than 30 days.
142/202