Summary Report for Conduct of Kozloduy NPP Stress Tests

“Kozloduy NPP” PLC
SUMMARY REPORT
for Conduct of Kozloduy NPP
Stress Tests
3.1.2 Current reassessments of MWL....................................................................................102
3.1.3 Conclusion with regard to consistency of the protection against external floodings.......105
3.2 ENSURING THE PLANT PROTECTION AGAINST MWL...........................................................107
3.2.1 SSCs required for bringing and maintaining of the units in safe shutdown state most
threatened at MWL.............................................................................................................................
107
3.2.2 The main design provisions for prevention of flooding impact on the plant...................111
3.2.3 Main operational measures for protection against external floodings ............................112
3.2.4 Potential impact from outside the plant, including prevention or blocking of personnel and
equipment access to the site..........................................................................................................113
3.3 PLANT COMPLIANCE WITH THE CURRENT LICENSING CONDITIONS ......................................116
3.4 EVALUATION OF SAFETY MARGINS AGAINST EXTERNAL FLOODINGS...................................116
3.4.1 Definition of safety margins against external floodings.................................................116
3.4.2 Potential measures to increase plant robustness against external floodings....................123
3.5 CONCLUSION FOR THE INFLUENCE OF EXTERNAL FLOODING ON KOZLODUY NPP SITE ........123
4 EXTREME METEOROLOGICAL IMPACTS ...........................................................124
4.1 ACTUAL ASSESSMENT OF METEOROLOGICAL PHENOMENA USED AS DESIGN
BASIS FOR THE SITE CONSTRUCTION ..................................................................................124
4.1.1 Extreme winds and sand spouts (tornado).....................................................................124
4.1.2 Humidity and freezing..................................................................................................124
4.1.3 Extreme precipitations..................................................................................................125
4.1.4 Lightning......................................................................................................................125
4.1.5 Extreme snowfalls ........................................................................................................125
4.1.6 Ice phenomena .............................................................................................................126
4.1.7 Extreme temperatures...................................................................................................126
4.1.8 Low standing of Danube River .....................................................................................126
4.1.9 Potential combinations of extreme meteorological impacts affecting the site ................126
4.1.10 Evaluation of frequency of occurrence of extreme weather conditions postulated in the
design basis........................................................................................................................................
127
4.2 ACTUAL STANDARD REQUIREMENTS FOR LOADS FROM EXTREME EXTERNAL EVENTS..........127
4.3 DESIGN BASIS...................................................................................................................128
4.3.1 Review of meteorological conditions used as design basis for SSCs ensuring safety of
Units 3 and 4 and structures margins assessment ..........................................................................129
4.3.2 Review of meteorological conditions used as design basis for SSCs ensuring safety of
Units 5 and 6 and structures margins assessment ..........................................................................131
4.3.3 SFS ..............................................................................................................................134
4.3.4 DSFS ...........................................................................................................................135
4.3.5 Outdoor Switchyard .....................................................................................................136
4.4 CONCLUSION FOR IMPACT OF THE EXTREME EXTERNAL EVENTS ON THE BUILDINGS AND
FACILITIES OF KOZLODUY NPP SITE...............................................................................................136
5 LOSS OF POWER SUPPLY AND LOSS OF ULTIMATE HEAT SINK ..................139
5.1 NUCLEAR REACTORS – UNITS 5 AND 6....................................................................139
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