Summary Report for Conduct of Kozloduy NPP Stress Tests

“Kozloduy NPP” PLC
SUMMARY REPORT
for Conduct of Kozloduy NPP
Stress Tests
At overflow and break of the state dike the shaft pump stations will be flooded first. They
are located next to the heel of the dike and the approximate height is 25 - 26m. With their failure
loss of the emergency makeup to the spray pools of Units 5 and 6 also occurs.
3.4.1.2.2 Power lines
As presented in item 3.2.4.2 the flooding of the lowland and its filling to elevation 32.93
will probably be accompanied by the destruction of part of the columns of power lines connecting
the Kozloduy NPP with the EES, on the way of the tidal wave. Therefore, for the purpose of safety
margins reassessment it can be conservatively assumed that a part of the power lines situated in the
valley between hot channel-2 and dual channel fail at penetration of water from Danube River.
3.4.1.2.3 BPS and channels
Elevation 0,00 of the bank pump station site corresponds to the absolute elevation 33,00. It
is considered not flooded at MWL – 32,93. At elevation 32,93, however, the pumps by their factory
characteristics do not function.
At berms crown elevation 33.00 of hot and cold channels and level of water in them 32.93,
in practice there will be a total water mirror. Although the dikes are not resized to this level, at
commissioning they were tested overflow over an average dike, which has an average elevation of
32.80. Under these conditions, the hot channel will be with the elevation of the Danube River and
will be connected to the cold channel through spillway of the average dike between the bridge
"Valya" and bridge "Heavy loads" - at elevation 32.80.
Another potential problem is that if the dry slope of the channel remains under cold water,
there is a potential of slope sliding if this condition is prolonged.
3.4.1.3 Buildings and facilities of Kozloduy NPP site the flooding of which occurs in sewage
system
The description of the sewage network is provided in [89]. Water penetration into the
buildings of Kozloduy NPP site at external flooding can occur both by rainwater and domestic
sewage. Examination of wells confirmed the expressed thesis that despite the availability of
treatment plant for domestic sewage at the site of Units 5 and 6 water return to in shaft 542 to
elevation 32,93 m is possible.
All cable channels and process tunnels drained into rainwater sewage and those whose
bottom is lower than 32.93 will be flooded. Corresponding penetrations at entry in the buildings, if
they are not tight, should be considered as a source of flooding.
3.4.1.3.1 Units 3 and 4 of Kozloduy NPP
Description of safety related SSCs of units 3 and 4 are provided in [89]. The sewage system
for production wastewater (returning back) of Units 3 and 4, before discharge into drain channel-1
passes through the local treatment facilities the level of which is significantly higher than the
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