CJSC «HAEK» UNITS 1-2 STRESS TEST SELF-ASSESSMENT REPORT OF THE ARMENIAN NPP CONTRIBUTIONS TO THE ARMENIAN NUCLEAR POWER PLANT (ANPP) OPERATOR FOR THE IMPLEMENTATION OF THE “STRESS TESTS” AT ANPP STRESS TEST SELF-ASSESSMENT REPORT OF THE ARMENIAN NPP TABLE OF CONTENTS ACRONYMS ...................................................................................................................... 6 INTRODUCTION ............................................................................................................. 16 1. CHAPTER 1: GENERAL DATA ABOUT SITE/PLANT ......................................................... 18 1.1. Brief description of the site characteristics ................................................ 18 1.2. Main characteristics of the units................................................................. 21 1.3. Systems to ensure or maintain the main safety functions ......................... 26 1.3.1. Reactivity control................................................................................. 50 1.3.2. Heat transfer from reactor to the ultimate heat sink ................................ 53 1.3.3. Heat transfer from spent fuel pools to the ultimate heat sink .................... 58 1.3.4. Heat transfer from the reactor containment to the ultimate heat sink ........ 59 1.3.5. AC Power supply ................................................................................. 59 1.3.6. Batteries for DC power supply............................................................... 64 1.4. Significant differences between units ........................................................ 65 1.5. Scope and main results of Probabilistic Safety Assessments ..................... 65 2. CHAPTER 2: EARTHQUAKES ....................................................................................... 93 2.1. Design basis ................................................................................................ 93 2.1.1. Earthquake against which the plant is designed ...................................... 93 2.1.2. Provision to protect the plant against the design basis earthquake ...........102 2.1.3. Compliance of the plant with its current licensing basis ...........................110 2.2. Evaluation of safety margins .................................................................... 113 2.2.1. Range of earthquake leading to severe fuel damage...............................113 2.2.2. Range of earthquake leading to loss of containment integrity ..................121 2.2.3. Earthquake exceeding the design basis earthquake for the plant and consequent flooding exceeding design basis flood ..................................121 2.2.4. Measures envisaged to increase robustness of the plant against earthquakes . ..........................................................................................121 3. CHAPTER 3: FLOODING ............................................................................................131 3.1. Design basis .............................................................................................. 131 3.1.1. Flooding against which the plant is designed .........................................131 3.1.2. Provisions to protect the plant against the design basis flood ..................133 3.1.3. Plant compliance with its current licensing basis.....................................144 3.2. Evaluation of safety margins .................................................................... 145 3.2.1. Estimation of safety margin against flooding..........................................145 3.2.2. Measures which can be envisaged to increase robustness of the plant against flooding ..........................................................................................146 4. CHAPTER 4: EXTREME WEATHER CONDITIONS ..........................................................149 4.1. Design basis .............................................................................................. 149 4.1.1. Reassessment of weather conditions used as design basis ......................149 4.2. Evaluation of safety margins .................................................................... 161 4.2.1. Estimation of safety margin against extreme weather conditions ..............161 4.2.2. Measures which can be envisaged to increase robustness of the plant against extreme weather conditions.................................................................163 5. CHAPTER 5: LOSS OF ELECTRICAL POWER AND LOSS OF ULTIMATE HEAT SINK ...........165 5.1. Loss of electrical power ............................................................................ 165 5.1.1. Loss of off-site power .........................................................................165 5.1.2. Loss of off-site power and loss of the ordinary back-up AC power source .168 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 ..............170 5.1.4. Conclusion on the adequacy of protection against loss of electrical power .173 5.1.5. Measures envisaged to increase robustness of the plant in case of loss of electrical power ..................................................................................174 5.2. Loss of the ultimate heat sink................................................................... 175 5.2.1. Design provisions to prevent the loss of the primary ultimate heat sink, such as alternative inlets or systems to protect main water inlet from blocking .175 5.2.2. Loss of the primary ultimate heat sink (e.g. loss of access to cooling water from the river or loss of the main cooling system) ..................................175 5.2.3. Loss of the primary ultimate heat sink and the alternate heat sink ...........176 5.2.4. Conclusion on the adequacy of protection against loss of ultimate heat sink ... ..........................................................................................178 5.2.5. Measures envisaged to increase robustness of the plant in case of loss of ultimate heat sink...............................................................................178 5.3. Loss of the primary ultimate heat sink, combined with station black out (i.e., loss of off-site power and on-site ordinary and back-up power source) .................................................................................................................. 178 5.3.1. Time of autonomy of the site before loss of normal reactor core cooling condition (e.g., start of water loss from the primary circuit) ....................178 5.3.2. External actions foreseen to prevent fuel degradation.............................179 5.3.3. Measures envisaged to increase robustness of the plant in case of loss of primary ultimate heat sink, combined with station black out ....................179 6. CHAPTER 6: SEVERE ACCIDENT MANAGEMENT ...........................................................188 6.1. Organisation and arrangements of the licensee to manage accidents .... 188 6.1.1. Organisation of the licensee to manage the accident ..............................189 6.1.2. Possibility to use existing equipment.....................................................197 6.1.3. Evaluation of factors that may impede accident management and respective contingencies .....................................................................................201 6.1.4. Conclusion on the adequacy of organisational issues for accident management ..........................................................................................204 6.1.5. Measures envisaged to enhance accident management capabilities ..........204 6.2. Accident management measures in place at the various stages of a scenario of loss of the core cooling function ........................................................... 204 6.2.1. Description of the accident management measures currently in place before occurrence of fuel damage in the reactor pressure vessel (including last resorts to prevent fuel damage), after occurrence of fuel damage and after failure of the reactor pressure vessel of a scenario of loss of the core cooling function ..........................................................................................204 6.2.2. Identification of any cliff edge effects, and evaluation of the time before they occur for a scenario of loss of core cooling function (all stages) ...............208 6.2.3. Assessment of the adequacy of the existing management measures for a scenario of loss of core cooling function (all stages), including the procedural guidance to cope with a severe accident ...............................................209 6.2.4. Evaluation of the potential for additional measures for a scenario of loss of core cooling function (all stages). Part I: Suitability and availability of the required instrumentation .....................................................................211 6.2.5. Evaluation of the potential for additional measures for a scenario of loss of core cooling function (all stages). Part II: Availability and habitability of the control room ......................................................................................213 6.2.6. Evaluation of the potential for additional measures for a scenario of loss of core cooling function (all stages). Part III: Evaluation of potential H2 accumulations in other buildings than containment ................................214 6.3. Maintaining the containment integrity after occurrence of significant fuel damage (up to core meltdown) in the