National Report of Hungary on the Targeted Safety Re-Assessment of Paks Nuclear Power Plant
Total Page:16
File Type:pdf, Size:1020Kb
National Report of Hungary on the Targeted Safety Re-assessment of Paks Nuclear Power Plant Compiled for the European Commission by the Hungarian Atomic Energy Authority Hungarian Atomic Energy Authority Budapest, December 29, 2011 Name, assignment Signature Date Editor: Dr. Ferenc Adorján HAEA Chief Advisor Verified by: Gyula Fichtinger DDG of HAEA Approved by: Dr. József Rónaky DG of HAEA 1 2 Contents 0. GENERAL REQUIREMENTS AND CONDITIONS OF THE ASSESSMENT ............................... 6 0.1. Initiative ....................................................................................................................................................... 6 0.2. Structure of the report .................................................................................................................................. 7 0.3. Role of the authority in the review ............................................................................................................... 7 0.4. Legal and regulatory requirements ............................................................................................................... 8 1. GENERAL DATA ABOUT THE SITE AND NUCLEAR POWER PLANT .................................... 9 1.1. Brief description of the site characteristics ................................................................................................... 9 1.1.1. Main characteristics of the units ................................................................................................................... 10 1.1.2. Description of the systems for conduction of main safety functions ............................................................ 12 1.2. Significant differences between units ..........................................................................................................25 1.2.1. Differences between the Emergency diesel generators ................................................................................ 25 1.2.2. Status of severe accident management modifications ................................................................................. 26 1.2.3. Location of demineralised water storage tanks of Installation II .................................................................. 26 1.2.4. Recovery of essential service water system after emptying ......................................................................... 27 1.2.5. Delivery of fire water into essential service water system ............................................................................ 27 1.3. Use of PSA as part of the safety assessment ................................................................................................27 1.3.1. Scope of probabilistic safety assessments ..................................................................................................... 27 1.3.2. Results of the re-assessment ......................................................................................................................... 27 2. EARTHQUAKES ................................................................................................................................. 33 2.1. Design basis .................................................................................................................................................33 2.1.1. Earthquake against which the plant is designed ........................................................................................... 33 2.1.2. Provisions to protect the plants against the design basis earthquake .......................................................... 37 2.1.3. Compliance of the plant with its current licensing basis ............................................................................... 42 2.2. Evaluation of safety margins ........................................................................................................................43 2.2.1. Range of earthquakes leading to severe fuel damage .................................................................................. 43 2.2.2. Range of earthquakes leading to loss of containment integrity .................................................................... 48 2.2.3. Earthquake exceeding the design basis earthquake for the plant and consequent flooding exceeding design basis flood ......................................................................................................................................................... 50 2.2.4. Measures which can be envisaged to increase robustness of the plants against earthquakes .................... 50 3. FLOODING .......................................................................................................................................... 52 3.1. Design basis .................................................................................................................................................52 3.1.1. Flooding against which the plant is designed ................................................................................................ 52 3.1.2. Provisions to protect the plants against the design basis flood .................................................................... 54 3.1.3. Plant compliance with its current licensing basis .......................................................................................... 54 3.2. Evaluation of safety margins ........................................................................................................................54 3.2.1. Estimation of safety margin against flooding ................................................................................................ 54 3 3.2.2. Measures which can be envisaged to increase robustness of the plants against flooding ........................... 55 4. EXTREME WEATHER CONDITIONS ........................................................................................... 56 4.1. Design basis .................................................................................................................................................56 4.1.1. Re-assessment of weather conditions used as design basis ......................................................................... 57 4.2. Evaluation of safety margins ........................................................................................................................58 4.2.1. Estimation of safety margin against extreme weather conditions ................................................................ 58 4.2.2. Measures which can be envisaged to increase robustness of the plants against extreme weather conditions .................................................................................................................................................................... 61 5. LOSS OF ELECTRICAL POWER AND LOSS OF ULTIMATE HEAT SINK ............................. 62 5.1. Loss of electric power ..................................................................................................................................62 5.1.1. Loss of off-site power .................................................................................................................................... 62 5.1.2. Loss of off-site power and loss of the ordinary back-up AC power source ................................................... 64 5.1.3. Loss of off-site power and loss of the ordinary back-up AC power sources, and loss of permanently installed diverse back-up AC power sources ............................................................................................................... 65 5.1.4. Conclusion on the adequacy of protection against loss of electrical power ................................................. 66 5.1.5. Measures which can be envisaged to increase robustness of the plants in case of loss of electrical power 68 5.2. Loss of decay heat removal capability/ultimate heat sink ............................................................................68 5.2.1. Design provisions to prevent the loss of the primary ultimate heat sink ...................................................... 69 5.2.2. Loss of primary ultimate heat sink ................................................................................................................ 71 5.2.3. Loss of primary ultimate heat sink and alternative heat sink ........................................................................ 74 5.2.4. Conclusions on the adequacy of the protection against the loss of the ultimate heat sink .......................... 80 5.2.5. Measures which can be envisaged to increase robustness of the plants in case of loss of ultimate heat sink ........................................................................................................................................................ 82 5.3. Loss of the primary ultimate heat sink, combined with station blackout .....................................................84 5.3.1. Time of autonomy of the site before loss of normal cooling condition of the reactor core and spent fuel pool ............................................................................................................................................................. 84 5.3.2. External actions foreseen to prevent fuel degradation ................................................................................. 84 5.3.3. Measures, which can be envisaged to increase robustness of the plant in case of loss of primary ultimate heat sink, combined with station blackout .................................................................................................................