Summary Report for Conduct of Kozloduy NPP Stress Tests

“Kozloduy NPP” PLC
SUMMARY REPORT
for Conduct of Kozloduy NPP
Stress Tests
the dual channel and hot channel-2 can only occur in reinforced concrete pipes passing under dual
channel.
3.2.4.2 Loss of off-site power
Flooding of the valley and filling to elevation 32.93 can be accompanied by the destruction
of part of the columns of power lines connecting Kozloduy NPP and bank pump station with
electric energy system of the Republic of Bulgaria (EES) in the path of tidal wave .
Since these columns are constructed with a height commensurate with the level of the
terrain, the distance between power lines and water surface in some areas will be 5 - 5.5 m lower
than it was before the flooding between the same power lines and the ground. This significant
reduction in the distance may lead to short circuits resulted in, respectively, failure of operation also
of those power lines whose columns are not destroyed by tidal waves. With all this, even if the very
site of the outdoor switchyard (OSY) is not affected by the flooding it is possible that the plant will
be temporarily left without off-site power due to the loss of part of the connections with the EES of
the Republic of Bulgaria.
At common cause de-energizing of bank pump station, through diesel-generators located in
the diesel-generator stations emergency power supply for the emergency pumps supplying water to
the advance chamber (emergency volume) of the circulation pump stations and one bank pump can
be provided.
3.2.4.3 Loss of cooling water
According to [89], the valley flooding will not lead to loss of cooling water.
At overflow or rupture of the dike and flooding to elevation 32.93, hot channel-2 will be
filled with water to the elevation of the river as regardless whether operating or not, its facilities for
discharge into the river are not equipped with closed facilities. The same refers to hot channel-1.
According to the design of Units 3 and 4 of Kozloduy NPP loss of bank pump station does
not affect the functioning of essential components service water pumps, as the service water drain
from heat exchangers can be supplied to the hot channel or to spray pools. Water from the spray
pools in the spillways returns back into the cold channel, and hence in the advance chamber of
circulation pump stations. The purpose of the advance chamber is to provide an adequate supply of
water at blackout of Units 1 to 4. At such accident according to the design in Circulation pump
station-1 advance chamber after “curve8” water inventory of 21380 m3 will remain, and in advance
chamber of Circulation pump station-2 it will be 15000 m3.
Flooding of valley and its filling to elevation 32.93 will lead to loss of function of the bank
pump station in the valley, at which loss of emergency makeup of spray pools of Units 5 and 6 will
occur. Normal makeup (from Circulation pump station 3 and 4) of spray pools will be retained. The
advance chamber of Circulation Pump Station 3 and 4 ensures the necessary water supplies.
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