Summary Report for Conduct of Kozloduy NPP Stress Tests

“Kozloduy NPP” PLC
SUMMARY REPORT
for Conduct of Kozloduy NPP
Stress Tests
In relation with performing of safety functions, flooding of the pumps of CEFWS (1÷4
CEFWS pumps) leads only to reduction of quantity of the systems performing the same safety
functions, and this is only if the spent nuclear fuel is located in the reactor, as 1÷4 CEFWS pumps
are not relevant to cooling of the SFP.
Therefore, as a result of the analysis the following recommendation may be introduced:
· Studying of possibility to prevent the flooding of buildings of the CEFWS.
· Implementation of periodic visual inspections to guarantee the leak tightness of the
penetrations of rainwater and domestic sewerage;
· Implementation of periodic inspections to guarantee the leak tightness of the
penetrations of pipelines, cable traces, etc.;
Measures to improve robustness at loss of power supply
Power supply to these systems for cooling of the fuel in SFP-3 and SFP-4 is provided from
various physically separated sources (emergency diesel generators – three per unit, emergency
diesel-generators of CEFWS, mobile DG). At low value of decay heat of the fuel stored in the pools
available time margin before the assemblies uncoverage starts is about one week for SFP-3 and
more than 9 days for SFP-4 at assumption of complete loss of cooling. Consequently no additional
measures are required to enhance robustness of SFP-3 and SFP-4.
Measures to improve robustness to loss of ultimate heat sink
At low value of decay heat of the fuel stored in the pools available time margin before the
assemblies uncoverage starts is about one week for SFP-3 and more than 9 days for SFP-4 at
assumption of complete loss of cooling.
6.1.4.2 Measures for Units 5 and 6
Set of the SBEOP for shut down reactor with the pressurized primary circuit passed
processes of verification and validation. Up to present operator training is conducted for work with
instructions of this type, and after this they will be introduced into operation.
Set of the SBEOP for shut down reactor with the depressurized primary circuit will be
subject to internal procedures of verification and validation at the NPP.
For severe accident management at Units 5 and 6 guidelines were developed for severe
accidents which follow the format of SBEOP. It is planned to subject these procedures to processes
of verification and validation and to introduce them to work.
6.1.4.3 Measures for SFS
Additional measures to improve robustness of SFS at loss of power supply are described in
par. 5.1.2 – reference 1 and par. 5.4.2.
6.1.4.4 Measures for DSFS
Measures envisioned in On-site and Off-site Emergency plan are sufficient.
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