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 · Average annual precipitations – 520 mm · Snow cover – not durative, maximum up to 30-40 days, typically do not exceed 15- 20 cm · Maximum recorded snow cover 80 cm with 3% recurrence · Dominating wind direction – west and north west · Average annual wind speed 1-4 m/s · Days with wind speed over 11,0 m/s – 69 · Days with wind speed over 16,0 m/s – 4-5 days · Extreme wind speed - 45 m/s The facilities at the site are designed before the 80-ies of the 20th century according to the regulations and standards applicable at the time. Changes in regulations and standards lead to a change in design requirements and implementation of large-scale programs for modernization and safety improvement of all nuclear facilities on the site, including with respect to seismic effects. Activities associated with retraining and ensuring seismic stability of the equipment of safety systems and civil structures with regard to increased seismic impact were completed in full-scale. Buildings in which safety related systems and components are located are I seismic category and are not directly affected by extreme weather phenomena. 4.3.1 Review of meteorological conditions used as design basis for SSCs ensuring safety of Units 3 and 4 and structures margins assessment 4.3.1.1 Extreme winds 4.3.1.1.1 Main building, Turbine Hall, CPS 2 and DGS 2 In the period 1997-2000 seismic strengthening of the main building, Turbine Hall, Circulation Pump Station 2 and Diesel Generator Station 2 was implemented in accordance with the requirements of "Load and effects on buildings and equipment" 1989. Standard wind load in the current design basis of the buildings meet the requirements of [141] on the standard value of the wind - 0,48 kN/m 2 and calculated value - 0.67 kN/m 2 . Performed seismic strengthening measures lead to increased reliability of the buildings for bearing loads from wind. The seismic reinforcements are valid for the determination of the required capacity of the building to bear horizontal loads (from seismic impacts and wind). Due to the nature of the reinforced concrete structure the seismic force exceeds the load from the extreme wind by many times, therefore the buildings have the capacity to bear also extreme wind loads. 4.3.1.1.2 ASSGEM 3, ASSGEM 4 and fire pump station-2 129/202
“Kozloduy NPP” PLC SUMMARY REPORT for Conduct of Kozloduy NPP Stress Tests Additional system for steam generator emergency makeup (ASSGEM-3) of unit 3 and ASSGEM-4 of unit 4, and Fire Pump Station 2 were designed and put into service before 1997 as a system of seismic category I and are designed for seismic effects of DBE level. The wind load calculated in the design basis (1.40 kN/m2) of the three buildings is greater than the extreme value (1.24 kN/m2) of these standards. The available margin is within 2.6%, taking into account the significance factor according to the current standards and elastic work of the structures. 4.3.1.1.3 Reinforced concrete ventilation pipes 1 and 2 In 1999 a constructive investigation of "Energoproekt" LLC of the three reinforced concrete pipes at the site was performed identifying that the facilities are designed for the effects of wind with calculated load from 1,26 kN/m2 exceeding the extreme values of 1.24 kN/m2 of these norms. The facilities have the required carrying capacity to bear the normative and extreme wind load as the design value of the wind is 88% higher as compared against the normative value and 1.6% against the extreme value the wind. 4.3.1.1.4 Spray pools 3,4 unit Design basis of the three spray pools comply with their first class in seismic resistance and the calculated maximum wind speed of 45 m/s (load - 1.24 kN/m2) at probability P = 0.01% (once per 10 000 years), which meets the requirements of the regulations and specified extreme wind speeds. Losses of water treatment during extreme winds do not affect the performance of the system safety function (ultimate heat sink) as the system is open and has a continuous makeup from the advance chamber before CPS-2. 4.3.1.2 Snowfalls 4.3.1.2.1 Units 3 and 4 – Reactor compartment The design basis for the calculated extreme snow loads (2.52 kN/m2) exceed the standard calculated value of these standards (1.68 kN/m2). Facilities have the necessary carrying capacity to withstand standard and extreme snow loads as the design calculated value of snow load is higher than 50% as compared against the normative value and 57% as compared against the extreme values of snow load. 4.3.1.2.2 ASSGEM 3 and 4, FPS 2, CPS 2 AND DGS 2 The design snow load in the design basis (1.40 kN/m2) is less than the defined extreme (1.6 kN/m2) and standard (1.68 kN/m2) value. In relatively heavy structures such as reinforced concrete, with a high ratio of permanent loads to the snow loads, the impact of the increase of snow is minimal. The physical condition of structural elements and the influence of a constant load is rather 130/202
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Summary Report for Conduct of Kozloduy NPP Stress Tests

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