Summary Report for Conduct of Kozloduy NPP Stress Tests

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“Kozloduy NPP” PLC SUMMARY REPORT for Conduct of Kozloduy NPP Stress Tests occur in their structures at extreme wind. In this case, if the spray pool makeup pumps are damaged, it is running emergency makeup of the pools of 6. ShPS in the valley of Danube River, i.e. the safety functions are not violated. Given that the structure of the buildings DGS is reinforced concrete ("heavy"), it can be assumed that at calculation and sizing of the combinations for seismic impact.. Therefore, the structure can accommodate the calculated effort under extreme wind pressure, which are close and lower than those at a seismic impact. 4.3.2.1.5 Spray pools Units 5, 6 The design basis of spray pools are consistent with their 1 category seismic resistance and the estimated maximum wind speed at probability p = 0.01% (once per 10,000 years) of 45 m/s.), which meets the requirements set for normative and extreme wind speeds. Supplementary water for spray pools, which comes from pumps CPS-3 and CPS-4 and as a reserve - diesel pumps and ShPS, compensates for losses from spraying at weak and moderate winds. There is a process option at extremely strong winds to eliminate losses from blowing, the water supplied for cooling is released directly to the bottom of the spray pools without spraying in nozzles, as its cooling is by convection. 4.3.2.2 Snowfalls 4.3.2.2.1 Main building – Reactor compartment Units 5 and 6 The calculated value of snow load (2,52 kN /m2 ) is 50% higher than the applicable standards (1,68 kN/m2) and 57% higher that the extreme value of snow load (1.6 kN/m2). The structure has reliable stiffness and can withstand extreme snowfall. 4.3.2.2.2 Reinforced concrete ventilation pipe loads. Due to the structure of the ventilation pipes they are not threatened by damage from snow 4.3.2.2.3 CPS 3 AND CPS 4, DGS-1,2 and 3 cells The calculated value of snow load in the design basis of the buildings (0,98 кN/м2) is lower than the current standards (1,68 КN/м2) and extreme value (1.6 kN/м2). At relatively heavy structures, such as reinforced concrete, with high ratio of permanent loads to the snow loads the impact of the snow load increase is minimal. The physical condition of structural elements and the influence of a constant load is rather leading to determining the bearing capacity of the elements and determination of sections, in which boundary deformation and loss of bearing capacity occurs. The roofs of DGS-1,2 and 3 cells have sufficient bearing capacity to accommodate the load of snow according to the new standards. 133/202
“Kozloduy NPP” PLC SUMMARY REPORT for Conduct of Kozloduy NPP Stress Tests Surface civil structures (prefabricated concrete elements) of CPS 3 and 4 were not strengthened during the modernization program. Given that extreme snow loads can be present for a short period of time (recurrence 3% for 1-2 days), it can be assumed that the extreme snow loads will lead to the limit bearing capacity of the building. But even assuming conservatively that damage will occur in their structures at extreme snow loads the safety functions are not violated. In this case, if spray pools makeup pumps are damaged, then emergency makeup of the pools from 6 ShPS in the valley of Danube River. 4.3.2.2.4 Spray pools Snowfalls do not apply load on the spray pools structure. 4.3.2.3 Extreme temperatures High temperatures, to the maximum measured for the area of Kozloduy NPP do not bear mechanical loads on structures and buildings at Units 5 and 6. In the given design basis extreme values of temperatures do not lead to failure to the plant safety functions. In the operational history of the plant there are no events and accident initiated by extremely low or extremely high temperatures. 4.3.2.3.1 Spray pools Design flow of sources of supplemental water is sufficient to compensate for evaporation losses at extremely high temperatures. The technological temperature mode of the spray pools provides for non-freezing of the water even at extreme temperatures. 4.3.2.3.2 Freezing To protect the bars before the pumps in BPS against freezing and icing recirculation facility is built – hot water battery. It ensures supply of hot water to the advance chamber of BPS 1 , 2 and 3. Probability of ice drifting occurrence has been assessed in the BPS design. To protect the advance chamber before BPS 2 and 3 against floating missiles bridge-barrier reinforced concrete facility with immovable bars. For technological provision of the required temperature mode and protection of bars of pumps CPS 1-4 against freezing hot water recirculation unit is constructed before CPS 1. 4.3.3 SFS 134/202
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“Kozloduy NPP” PLC Figure 1.2-2
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Summary Report for Conduct of Kozloduy NPP Stress Tests

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