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 />
Units 3 and 4 auxiliaries during operation in mode E are supplied from EES, from OSY 220<br />
kV through backup trans<strong>for</strong>mer. Where needed, the units auxiliaries can be powered from OSY 400<br />
kV through their own unit trans<strong>for</strong>mers and auxiliary trans<strong>for</strong>mers.<br />
1.2.2.3.2.2 Independence, physical separation and protection against external and internal<br />
hazards to the backup power supply<br />
The electric energy system as a source <strong>of</strong> backup power shows stability in operation.<br />
1.2.2.3.2.3 Restrictions in the availability <strong>of</strong> backup power supply sources and external<br />
measures to extend operational time.<br />
According to the “Rules <strong>of</strong> Electric Energy System Control” the nuclear power plant are<br />
connected by principle “n – 2” (provided with at least two power supply sources that can be<br />
connected when needed), unlike the remaining energy facilities that are connected by principle “n –<br />
1” (provided with at least one power supply source that can be connected when needed).<br />
1.2.2.3.3 Emergency power supply<br />
1.2.2.3.3.1 Emergency power supply source<br />
At loss <strong>of</strong> main and backup power supply, the loads are supplied with emergency backup<br />
power supply depending on the significance category they belong to. The first category loads are<br />
connected to sections that preserve uninterruptible power supply through inventors from the<br />
batteries <strong>of</strong> respective safety trains. The second category loads are connected to the so-called diesel<br />
sections and allow <strong>for</strong> interruption in the power supply <strong>for</strong> max. 1 min, according to the nuclear<br />
safety requirements.<br />
1.2.2.3.3.2 Location, independence, physical separation <strong>of</strong> emergency power supply and<br />
protection against external and internal impacts<br />
The equipment related to providing emergency power supply is located in special premises.<br />
They are protected against internal (fires, floods) and external events both by design solutions <strong>for</strong><br />
physical separation, premises design, etc. and by numerous improvements to the design aimed at<br />
enhancing their resistance against internal and external hazards. Each emergency diesel-generator is<br />
located in a separate compartment <strong>of</strong> diesel-generator station. The compartments where individual<br />
diesel-generators are located are separated by fire rein<strong>for</strong>ced concrete walls. The doors between the<br />
compartments are fire protected and sealed.<br />
1.2.2.3.3.3 Restrictions in the availability <strong>of</strong> emergency power supply sources and external<br />
measures to extend operational time<br />
At loss <strong>of</strong> emergency power supply to the unit, it is possible to supply power from the<br />
neighbouring unit, <strong>for</strong> this purpose technical and organizational measures are provided. Inventories<br />
<strong>of</strong> combustible-lubrication materials ensure operation <strong>of</strong> all DGs <strong>for</strong> at least 4 days, and during this<br />
period delivery <strong>of</strong> additional inventory can be organized.<br />
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