Summary Report for Conduct of Kozloduy NPP Stress Tests
Summary Report for Conduct of Kozloduy NPP Stress Tests
Summary Report for Conduct of Kozloduy NPP Stress Tests
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“<strong>Kozloduy</strong> <strong>NPP</strong>” PLC<br />
SUMMARY REPORT<br />
<strong>for</strong> <strong>Conduct</strong> <strong>of</strong> <strong>Kozloduy</strong> <strong>NPP</strong><br />
<strong>Stress</strong> <strong>Tests</strong><br />
2 EARTHQUAKE<br />
The facilities subject to stress tests <strong>of</strong> <strong>Kozloduy</strong> <strong>NPP</strong> were designed and constructed within<br />
the period from 1973 to 1992. During this period <strong>of</strong> time both the seismicity itself (earthquakes with<br />
focal in Vrancha in 1977, 1986 and 1990) and the normative documents <strong>for</strong> its definition have<br />
changed. <strong>Kozloduy</strong> <strong>NPP</strong> has responded consistently to all those changes by per<strong>for</strong>ming the required<br />
additional surveys. New seismic characteristics <strong>of</strong> the site have been identified and safety related<br />
facilities ensured <strong>for</strong> them.<br />
2.1 INITIAL SEISMIC DESIGN BASES OF KOZLODUY <strong>NPP</strong><br />
2.1.1 Initial seismic design bases <strong>of</strong> units 3 and 4<br />
According to the design <strong>of</strong> 1973 <strong>of</strong> <strong>Kozloduy</strong> <strong>NPP</strong> units 1 and 2 the seismic activity <strong>of</strong> the<br />
region has been assessed <strong>for</strong> as VI degree <strong>of</strong> MSK-64 scale, due to which in the design special<br />
measures have not been taken <strong>for</strong> improvement <strong>of</strong> the seismic resistance <strong>of</strong> the structures.<br />
Following the earthquake <strong>of</strong> 4.03.1977 with epicentre in the region <strong>of</strong> Vrancha mountain the site<br />
seismic re-evaluation has been per<strong>for</strong>med and operational base earthquake (OBE) level was<br />
accepted as the VI degree with peak ground acceleration (PGA) <strong>of</strong> 0.05g and design basis<br />
earthquake (DBE) – the VII degree with PGA <strong>of</strong> 0.1g.<br />
In the design <strong>of</strong> units 3 and 4 <strong>of</strong> <strong>Kozloduy</strong> <strong>NPP</strong> the following maximum seismic impacts on<br />
the site have been adopted:<br />
· OBE - VI degree by MSK-64 scale<br />
· DBE - VII degree by MSK-64 scale;<br />
· Floor response spectra – the spectrum <strong>of</strong> accelerogram <strong>of</strong> the Vrancha earthquake<br />
dated 4.03.1977, recorded in Bukuresht and brought to PGA <strong>of</strong> 0.1 g.<br />
2.1.2 Initial seismic design bases <strong>of</strong> units 5 and 6<br />
The design <strong>of</strong> Units 5 and 6 has been developed with the following seismic characteristics:<br />
· The design basis earthquake (DBE OBE) = VI degree by МSК-64 scale with peak<br />
ground acceleration (PGA) <strong>of</strong> 0.05g with recurrence period <strong>of</strong> 100 years and<br />
· Safe shutdown earthquake (DBE DBE) = VII degree by МSК-64 scale with peak<br />
ground acceleration (PGA) <strong>of</strong> 0.1g with recurrence period <strong>of</strong> 10000 years.<br />
2.1.3 Initial seismic design bases <strong>of</strong> SFS<br />
SFS has been designed during the period from 1982 to 1984 with the following seismic<br />
characteristics: DBE = VII degree by МSК-64 scale with peak ground acceleration (PGA) <strong>of</strong> 0.1g<br />
with recurrence period <strong>of</strong> 10 000 years.<br />
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