Accident de fukushima

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Description de l'accident de Fukushima; remarques implicites sur ses causes.

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Accident de fukushima

  1. 1. Pourquoi ?<br />Fukushima<br />1<br />
  2. 2. Fukushima<br />2<br />
  3. 3. Fukushima<br />3<br />
  4. 4. Fukushima<br />4<br />Un site excavéadossé à unecolline ; les ouvragesd’eau et les sales des machines vont amplifier la vague<br />
  5. 5. Un site excavéadossé à unecolline<br />Fukushima<br />5<br />
  6. 6. BWR : les principes<br />Fukushima<br />6<br />
  7. 7. Un réacteurinstallétrès haut (instrumentation par le bas)<br />Fukushima<br />7<br />
  8. 8. L’installationélevéeest un handicap vis-à-vis du séisme, le concepteurestincité à réduire le niveau de la plateforme ; stockage combustible dans le BR<br />Fukushima<br />8<br />
  9. 9. Browns Ferry montre les dimensions<br />Fukushima<br />9<br />
  10. 10. ReactorCore Isolation CoolingSystem<br />20 m3/mn<br />No electricalsupply<br />Fukushima<br />10<br />
  11. 11. Injection de sécurité – Aspersion enceintesont des ystèmes de sûreté ; alimentation électriquesecoure – maisdéfaillante<br />Fukushima<br />11<br />
  12. 12. Le tsunami<br />Planches suivantes à voirimpérativement en mode Diaporama<br />Extrait d’un film pris par un ingénieur General Electric qui s’estmis à l’abri à l’annonce du tsunami<br />On voitque la centrale a amplifié la vague de tsunami<br />Ouvragesd’eau à l’amont<br />“mur” constitué par les s alles des machines<br />Colline à laquelle les sallles des machines étaientadossées<br />Fukushima<br />12<br />
  13. 13. Fukushima<br />13<br />
  14. 14. Fukushima<br />14<br />Calage des installations – les unités 5 & 6 étaient plus hautes de 3m : le concepteur se doutaitquel’implantation 1 à 4 étaitbasse…<br />
  15. 15. Fukushima<br />15<br />
  16. 16. Calage des installations – les unités 5 & 6 étaient plus hautes de 3m : le concepteur se doutaitquel’implantation 1 à 4 étaitbasse…<br />Fukushima<br />16<br />
  17. 17. La zone inondée<br />La slide suivantemontre la carte de la zone inondée<br />L(excavation des installations les a mises en situation de noyage<br />Fukushima<br />17<br />
  18. 18. Construiresur le bedrock<br />Fukushima<br />18<br />
  19. 19. Le développement de l’accident<br />Les slides suivantesmontrent le développement de l’accident<br />Préparées par le Dr Braun (Areva Gmbh)<br />A voir en mode Diaporama<br />Fukushima<br />19<br />
  20. 20. Reactor Service Floor(Steel Construction)<br />Concrete Reactor Building(secondary Containment)<br />Reactor Core<br />Reactor Pressure Vessel<br />Containment (Dry well)<br />Containment (Wet Well) / Condensation Chamber <br />Spend Fuel Pool<br />Fresh Steam line<br />Main Feedwater<br />Fukushima<br />20<br />
  21. 21. 11.3.2011 14:46 - Earthquake<br /><ul><li>Magnitude 9
  22. 22. Power grid in northern Japan fails
  23. 23. Reactors itself are mainly undamaged</li></ul>SCRAM<br /><ul><li>Power generation due to Fission of Uranium stops
  24. 24. Heat generation due to radioactive Decay of Fission Products
  25. 25. After Scram ~6%
  26. 26. After 1 Day ~1%
  27. 27. After 5 Days ~0.5%</li></ul>Fukushima<br />21<br />
  28. 28. Containment Isolation<br /><ul><li>Closing of all non-safety related Penetrations of the containment
  29. 29. Cuts off Machine hall
  30. 30. If containment isolation succeeds, a large early release of fission products is highly unlikely</li></ul>Diesel generators start<br /><ul><li>Emergency Core cooling systems are supplied</li></ul>Plant is in a stable save state<br />Fukushima<br />22<br />
  31. 31. 11.3. 15:41 Tsunami hits the plant<br /><ul><li>Plant Design for Tsunami height of up to 6.5m
  32. 32. Actual Tsunami height >7m
  33. 33. Flooding of
  34. 34. Diesel Generators and/or
  35. 35. Essential service water building cooling the generators</li></ul>Station Blackout<br /><ul><li>Common cause failure of the power supply
  36. 36. Only Batteries are still available
  37. 37. Failure of all but one Emergency core cooling systems </li></ul>Fukushima<br />23<br />
  38. 38. The Fukushima Daiichi Incident2. Accident progression<br />Reactor Core Isolation Pump still available<br /><ul><li>Steam from the Reactor drives a Turbine
  39. 39. Steam gets condensed in the Wet-Well
  40. 40. Turbine drives a Pump
  41. 41. Water from the Wet-Well gets pumped in Reactor
  42. 42. Necessary:
  43. 43. Battery power
  44. 44. Temperature in the wet-well must be below 100°C</li></ul>As there is no heat removal from the building, the Core isolation pump cant work infinitely<br />Fukushima<br />24<br />
  45. 45. Reactor Isolation pump stops<br /><ul><li>11.3. 16:36 in Unit 1 (Batteries empty)
  46. 46. 14.3. 13:25 in Unit 2(Pump failure)
  47. 47. 13.3. 2:44 in Unit 3 (Batteries empty)</li></ul>Decay Heat produces still steam in Reactor pressure Vessel<br /><ul><li>Pressure rising</li></ul>Opening the steam relieve valves<br /><ul><li>Discharge Steam into the Wet-Well</li></ul>Descending of the Liquid Level in the Reactor pressure vessel<br />Fukushima<br />25<br />
  48. 48. Reactor Isolation pump stops<br /><ul><li>11.3. 16:36 in Unit 1 (Batteries empty)
  49. 49. 14.3. 13:25 in Unit 2(Pump failure)
  50. 50. 13.3. 2:44 in Unit 3 (Batteries empty)</li></ul>Decay Heat produces still steam in Reactor pressure Vessel<br /><ul><li>Pressure rising</li></ul>Opening the steam relieve valves<br /><ul><li>Discharge Steam into the Wet-Well</li></ul>Descending of the Liquid Level in the Reactor pressure vessel<br />Fukushima<br />26<br />
  51. 51. The Fukushima Daiichi Incident2. Accident progression<br />Reactor Isolation pump stops<br /><ul><li>11.3. 16:36 in Unit 1 (Batteries empty)
  52. 52. 14.3. 13:25 in Unit 2(Pump failure)
  53. 53. 13.3. 2:44 in Unit 3 (Batteries empty)</li></ul>Decay Heat produces still steam in Reactor pressure Vessel<br /><ul><li>Pressure rising</li></ul>Opening the steam relieve valves<br /><ul><li>Discharge Steam into the Wet-Well</li></ul>Descending of the Liquid Level in the Reactor pressure vessel<br />Fukushima<br />27<br />
  54. 54. Reactor Isolation pump stops<br /><ul><li>11.3. 16:36 in Unit 1 (Batteries empty)
  55. 55. 14.3. 13:25 in Unit 2(Pump failure)
  56. 56. 13.3. 2:44 in Unit 3 (Batteries empty)</li></ul>Decay Heat produces still steam in Reactor pressure Vessel<br /><ul><li>Pressure rising</li></ul>Opening the steam relieve valves<br /><ul><li>Discharge Steam into the Wet-Well</li></ul>Descending of the Liquid Level in the Reactor pressure vessel<br />Fukushima<br />28<br />
  57. 57. Reactor Isolation pump stops<br /><ul><li>11.3. 16:36 in Unit 1 (Batteries empty)
  58. 58. 14.3. 13:25 in Unit 2(Pump failure)
  59. 59. 13.3. 2:44 in Unit 3 (Batteries empty)</li></ul>Decay Heat produces still steam in Reactor pressure Vessel<br /><ul><li>Pressure rising</li></ul>Opening the steam relieve valves<br /><ul><li>Discharge Steam into the Wet-Well</li></ul>Descending of the Liquid Level in the Reactor pressure vessel<br />Fukushima<br />29<br />
  60. 60. The Fukushima Daiichi Incident2. Accident progression<br />Measured, and here referenced Liquid level is the collapsed level. The actual liquid level lies higher due to the steam bubbles in the liquid<br />~50% of the core exposed<br /><ul><li>Cladding temperatures rise, but still no significant core damage</li></ul>~2/3 of the core exposed<br /><ul><li>Cladding temperature exceeds ~900°C
  61. 61. Balooning / Breaking of the cladding
  62. 62. Release of fission products form the fuel rod gaps</li></ul>Fukushima<br />30<br />
  63. 63. ~3/4 of the core exposed<br /><ul><li>Cladding exceeds ~1200°C
  64. 64. Zirconium in the cladding starts to burn under Steam atmosphere
  65. 65. Zr + 2H20 ->ZrO2 + 2H2
  66. 66. Exothermal reaction furtherheats the core
  67. 67. Generation of hydrogen
  68. 68. Unit 1: 300-600kg
  69. 69. Unit 2/3: 300-1000kg
  70. 70. Hydrogen gets pushed via the wet-well, the wet-well vacuum breakers into the dry-well </li></ul>Fukushima<br />31<br />
  71. 71. at ~1800°C [Unit 1,2,3]<br /><ul><li>Melting of the Cladding
  72. 72. Melting of the steel structures</li></ul>at ~2500°C [Block 1,2]<br /><ul><li>Breaking of the fuel rods
  73. 73. debris bed inside the core</li></ul>at ~2700°C [Block 1]<br /><ul><li>Melting of Uranium-Zirconium eutectics</li></ul>Restoration of the water supply stops accident in all 3 Units<br /><ul><li>Unit 1: 12.3. 20:20 (27h w.o. water)
  74. 74. Unit 2: 14.3. 20:33 (7h w.o. water)
  75. 75. Unit 3: 13.3. 9:38 (7h w.o. water)</li></ul>Fukushima<br />32<br />
  76. 76. The Fukushima Daiichi Incident2. Accident progression<br />Release of fission products during melt down<br /><ul><li>Xenon, Cesium, Iodine,…
  77. 77. Uranium/Plutonium remain in core
  78. 78. Fission products condensate to airborne Aerosols</li></ul>Discharge through valves into water of the condensation chamber<br /><ul><li>Pool scrubbing binds a fraction of Aerosols in the water</li></ul>Xenon and remaining aerosols enter the Dry-Well<br /><ul><li>Deposition of aerosols on surfaces further decontaminates air</li></ul>Fukushima<br />33<br />
  79. 79. Containment <br /><ul><li>Last barrier between Fission Products and Environment
  80. 80. Wall thickness ~3cm
  81. 81. Design Pressure 4-5bar</li></ul>Actual pressure up to 8 bars<br /><ul><li>Normal inert gas filling (Nitrogen)
  82. 82. Hydrogen from core oxidation
  83. 83. Boiling condensation chamber(like a pressure cooker)</li></ul>Depressurization of the containment<br /><ul><li>Unit 1: 12.3. 4:00
  84. 84. Unit 2: 13.3 00:00
  85. 85. Unit 3: 13.3. 8.41 </li></ul>Fukushima<br />34<br />
  86. 86. Positive und negative Aspects of depressurizing the containment<br /><ul><li>Removes Energy from the Reactor building (only way left)
  87. 87. Reducing the pressure to ~4 bar
  88. 88. Release of small amounts of Aerosols (Iodine, Cesium ~0.1%)
  89. 89. Release of all noble gases
  90. 90. Release of Hydrogen</li></ul>Gas is released into the reactor service floor<br /><ul><li>Hydrogen is flammable</li></ul>Fukushima<br />35<br />
  91. 91. Unit 1 und 3<br /><ul><li>Hydrogen burn inside the reactor service floor
  92. 92. Destruction of the steel-frame roof
  93. 93. Reinforced concrete reactor building seems undamaged
  94. 94. Spectacular but minor safety relevant</li></ul>Fukushima<br />36<br />
  95. 95. The Fukushima Daiichi Incident2. Accident progression<br />Unit 2<br /><ul><li>Hydrogen burn inside the reactor building
  96. 96. Probably damage to the condensation chamber(highly contaminated water)
  97. 97. Uncontrolled release of gas from the containment
  98. 98. Release of fission products
  99. 99. Temporal evacuation of the plant
  100. 100. High local dose rates on the plant site due to wreckage hinder further recovery work</li></ul>No clear information's why Unit 2 behaved differently<br />Fukushima<br />37<br />
  101. 101. Venting et refroidissement Eau de mer<br />Fukushima<br />38<br />
  102. 102. ParamètresUnité 1 – le refroidissemnt Eau de mer a contribué à l’augmentation de la concentration H2 et à l’explosion<br />Fukushima<br />39<br />
  103. 103. ParamètresUnité 2<br />Fukushima<br />40<br />
  104. 104. Refroidissement Piscine 4<br />Fukushima<br />41<br />
  105. 105. Cheminement des fuitesvers la station de pompage via des galleries<br />Fukushima<br />Page 42<br /><ul><li>Highly radioactive water leaked from Turbine building 2
  106. 106. Transfer to an cable trench
  107. 107. Seismic integrity of the trench was not a Design requirement
  108. 108. Water leaked to the foundation layer and to the sea </li></ul>Intake channel<br />
  109. 109. Sealing the leak<br />Fukushima<br />Page 43<br />http://www.tepco.co.jp/en/press/corp-com/release/betu11_e/images/110406e1.pdf<br />
  110. 110. Final gate planned<br />Fukushima<br />Page 44<br />Plan<br />To prevent potential new leaks from the pits and trenches. a water gate to be installesd<br />Vue en coupe<br />
  111. 111. Refroidissementpiscines<br />Fukushima<br />45<br />
  112. 112. Une “réévaluation” de sûretéavaitétéfaite<br />Fukushima<br />46<br />
  113. 113. NSC Decision No. 2006-60September 19, 2006The Nuclear Safety Commission of Japan<br />Seismic reevaluation (back-checks) recommended on existing NPPs based on the revised seismic design guide1<br />The above-mentioned seismic safety checks of existing facilities should be conducted on the voluntary basis of the operators out of legally bound obligations<br />Fukushima<br />47<br />
  114. 114. Comparaisonancienne et nouvelle règle : le tsunami n’était pas considérédansl’anciennerègle<br />Fukushima<br />48<br />
  115. 115. La classification sismique du systèmed’injection de sûretéétaitdansunecatégorieinférieure<br />Fukushima<br />49<br />
  116. 116. Présentationpar TEPCO des résultats de la réévaluation le 26 novembre 2010<br />Fukushima<br />50<br />
  117. 117. Fukushima<br />51<br />
  118. 118. Conclusion de la présentation : la sûretéestconfirmée !<br />Fukushima<br />52<br />
  119. 119. Conception des REP français<br />La piscine estdans un bâtimentdéparé<br />L’installationgénéraleest plus basse<br />Les fonctions de sûretésontassurées par des systèmesredondants et diversifiés<br />Alimentations électriquesultimes<br />ProcédurePertetotalealimentations électriques (turbo-générateur pour alimentation et joints et charge batteries essentielles)<br />Fukushima<br />53<br />
  120. 120. Fukushima<br />54<br />
  121. 121. Fukushima<br />55<br />
  122. 122. Alimentation de secours des générateurs de vapeur<br />Fukushima<br />56<br />
  123. 123. Grouped’ultimesecours et diesels ultimes (EPR) <br />Fukushima<br />57<br />
  124. 124. Fukushima<br />58<br />
  125. 125. Redondance et diversification<br />Fukushima<br />59<br />
  126. 126. Recombineurscatalytiques<br />Fukushima<br />60<br />

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