Summary Report for Conduct of Kozloduy NPP Stress Tests

“Kozloduy NPP” PLC
SUMMARY REPORT
for Conduct of Kozloduy NPP
Stress Tests
Based of the performed walkdowns, review of the available documentation and engineering
evaluation it was assumed that one possible scenarios of flooding of the buildings and facilities of
the site is through the sewage system of the plant. Walkdowns are performed for precise
localization of the lowest sewage exits in the buildings where equipment is located – directly related
to the safety of the plant. Although these places have no openings (drains, sinks, etc..) direct
flooding of the premises is possible due to lack of sewer connections (especially when they are PVC
or cast iron pipes with lead калчища) and through plugs and manholes.
The study identified no buildings or facilities the flooding of which will directly influence
the plant safety functions.
The facilities failure to which will lead to the greatest effect on the nuclear facilities in
Kozloduy NPP are electric wires located in the valley between hot channel-2 and dual channel. The
loss of their functions can lead to loss of off-site power supply for the plant.
The most important weak points found in this study of flooding of the plant with MWL=
32,93 m, can be divided as follows:
· Shutdown of the Power Generation and passing to the diesel-generators electric
power supply source – due to possible failure of a part of the power lines connecting plant to
the EES;
· Termination of water supply or cold channel due to loss of bank pump station and
lack of access to it by land;
· loss of emergency power supply of the Spray pools of units 5 and 6 due to failure of
the shaft pump stations;
· flooding of a part of a part of the town infrastructure and access from the town of
Kozloduy to the plant by the ring road which does not affect access to the plant;
· flooding of a part of underground communications under elevation 32,93 m –
drainage into the rainwater sewage and leakage in the channels where they are located;
· loss of redundant system (alternative) for spent fuel cooling by the steam generators
when the fuel is in the reactor – failure of the pumps of additional system for steam
generator emergency makeup.
The sequence of flooding of the facilities leading to selected consequences are provided in
Table 3.4-1.
Additional weak point complicating the situation is that at overflow of the protective dike
without its destruction the water flooding the plain between Kozloduy NPP and Danube River will
remain accumulated in a closed space between hot channel-2, dual channel and protective dike.
Thus, although the anticipated disastrous wave will continue for several hours, the water retained in
this space may remain for indefinitely long time up to complete and natural drainage.
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