European Stress Tests for Nuclear Power Plants National Report FINLAND 3/0600/2011 December 30, 2011 Tomi Routamo (ed.) © Radiation and Nuclear Safety Authority 2011 Radiation and Nuclear Safety Authority Report i (xvii) 3/0600/2011 Nuclear Reactor Regulation December 30, 2011 Public CONTENTS Abbreviations ................................................................................................................................................................ x Authors ......................................................................................................................................................................... xii Executive summary ................................................................................................................................................. xiii A. Background information on National Report .......................................................................................... 1 A.1 General view on NPPs and nuclear power regulation in Finland ........................................................... 1 A.2 Earthquakes – seismicity in Finland and Finnish requirements ............................................................. 3 A.3 Flooding – Finnish requirements ......................................................................................................................... 7 A.4 Extreme weather conditions – Finnish requirements .............................................................................. 10 A.5 Electrical power supply – Finnish requirements ........................................................................................ 10 A.6 Severe accident management – Finnish requirements ............................................................................ 13 A.7 Actions initiated in Finland after the Fukushima Dai-ichi accident .................................................... 21 B. Fortum – Loviisa 1&2 ...................................................................................................................................... 22 B.1 General data about the site and nuclear power plant units ................................................................... 22 B.1.1 Brief description of the site characteristics ......................................................................................... 22 B.1.1.1 Main characteristics of the units ......................................................................................................... 22 B.1.1.2 Description of the systems for conduction of main safety functions ................................... 23 B.1.2 Significant differences between units .................................................................................................... 30 B.1.3 Use of PSA as part of the safety assessment ........................................................................................ 30 B.2 Earthquakes ............................................................................................................................................................... 33 B.2.1 Design basis ...................................................................................................................................................... 33 B.2.1.1 Earthquake against which the plant is designed .......................................................................... 33 B.2.1.2 Provisions to protect the plant against the design basis earthquake .................................. 33 B.2.1.3 Compliance of the plant with its current licensing basis .......................................................... 35 B.2.2 Evaluation of safety margins ..................................................................................................................... 35 B.2.2.1 Range of earthquake leading to severe fuel damage .................................................................. 35 B.2.2.2 Range of earthquake leading to loss of containment integrity ............................................... 36 B.2.2.3 Earthquake exceeding the design basis earthquake for the plant and consequent flooding exceeding design basis flood ............................................................. 36 B.2.2.4 Measures which can be envisaged to increase robustness of the plant against earthquakes ................................................................................................................................. 36 B.3 Flooding ....................................................................................................................................................................... 38 B.3.1 Design basis ...................................................................................................................................................... 38 B.3.1.1 Flooding against which the plant is designed ................................................................................ 38 Radiation and Nuclear Safety Authority Report ii (xvii) 3/0600/2011 Nuclear Reactor Regulation December 30, 2011 Public B.3.1.2 Provisions to protect the plant against the design basis flood ............................................... 41 B.3.1.3 Plant’s compliance with its current licensing basis .................................................................... 43 B.3.2 Evaluation of safety margins ..................................................................................................................... 44 B.3.2.1 Estimation of safety margin against flooding ................................................................................ 44 B.3.2.2 Measures which can be envisaged to increase robustness of the plant against flooding .......................................................................................................................................... 44 B.4 Extreme weather conditions ............................................................................................................................... 46 B.4.1 Design basis ...................................................................................................................................................... 46 B.4.1.1 Reassessment of weather conditions used as design basis ..................................................... 47 B.4.2 Evaluation of safety margins ..................................................................................................................... 56 B.4.2.1 Estimation of safety margin against extreme weather conditions ....................................... 56 B.4.2.2 Measures which can be envisaged to increase robustness of the plant against extreme weather conditions ................................................................................................. 60 B.5 Loss of electrical power and loss of ultimate heat sink ............................................................................ 62 B.5.1 Loss of electrical power ............................................................................................................................... 62 B.5.1.1 Loss of off-site power ............................................................................................................................... 62 B.5.1.2 Loss of off-site power and loss of the ordinary back-up AC power sources ..................... 63 B.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 B.5.1.4 Conclusions on the adequacy of protection against loss of electrical power ................... 67 B.5.1.5 Measures which can be envisaged to increase robustness of the plant in case of loss of electrical power ....................................................................................................... 68 B.5.2 Loss of the decay heat removal capability/ultimate heat sink .................................................... 69 B.5.2.1 Design provisions to prevent the loss of the primary ultimate heat sink .......................... 69 B.5.2.2 Loss of the primary ultimate heat sink ............................................................................................. 70 B.5.2.3 Loss of the primary ultimate heat sink and the alternate heat sink ..................................... 72 B.5.2.4 Conclusions on the adequacy of protection against loss of ultimate heat sink ............... 73 B.5.2.5 Measures which can be envisaged to increase robustness of the plant in case of loss of ultimate heat sink.................................................................................................... 73 B.5.3 Loss of the primary ultimate heat sink, combined with station blackout .............................. 74 B.5.3.1 Time of autonomy of the site before loss of normal cooling condition of the reactor core and spent fuel pool ............................................................................................. 74 B.5.3.2 External actions foreseen to prevent fuel degradation ............................................................. 76 B.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............... 76 B.6 Severe accident management ............................................................................................................................. 77 B.6.1 Organization and arrangements of the licensee to manage accidents ..................................... 77 Radiation and Nuclear