The Fukushima Daiichi Incident

1. The Fukushima Daiichi Incident • Matthias Braun • PEPA4-G • AREVA NP GmbH

2. The Fukushima Daiichi Incident • Unit I - GE Mark I BWR (439 MW), Operating since 1970 • Unit II & III - GE Mark I BWR (760 MW), Operating since 1974 Spiegel.de

3. The Fukushima Daiichi Incident Service Floor (Steel) Building (Concrete) RPV Containment Pressure suppression pool nucleartourist.com

4. The Fukushima Daiichi Incident nucleartourist.com

5. The Fukushima Daiichi Incident nucleartourist.com

6. The Fukushima Daiichi Incident nucleartourist.com

7. The Fukushima Daiichi Incident www.zwentendorf.com

8. The Fukushima Daiichi Incident nucleartourist.com

9. The Fukushima Daiichi Incident Fresh Steam Main Feedwater Core RPV Containment Pressure suppression pool

10. The Fukushima Daiichi Incident Containment Pressure suppression pool Containment closure Head en.wikipedia.org/wiki/Browns_Ferry_Nuclear_Power_Plant

11. The Fukushima Daiichi Incident Progression of the accident: • 11.3.2011 14:46Earthquake • SCRAM • Containment-Isolation • Close of fresh steam and main feed water valves • Only a failure of these Valves could lead to an early large release

12. The Fukushima Daiichi Incident • 11.3.2011 3:41pmStation-Blackout • Loss of off-site power due to Earthquake • Diesel startet as planed • Tsunami damaged either Diesel generators or Service water supply(Tsunami height >7m, plant designed for 6.5m) • Failure of all active cooling systems • Core Isolation Pump / Einspeisesystem TJ • Steam from Reactor drives Turbine • Turbine pumps water form pressure suppression pool • Needs Battery power

13. The Fukushima Daiichi Incident • Reactor Isolation pump stopped • Either Run-out of Batteries • Or pressure suppression pool boils • Pressure buildup in reactor • Decay heat produces steam • Opening of pressure relief valves • Steam gets blown in pressure suppression pool

14. The Fukushima Daiichi Incident • Dry-out of the RPV

15. The Fukushima Daiichi Incident • Dry-out of the RPV

16. The Fukushima Daiichi Incident • Dry-out of the RPV

17. The Fukushima Daiichi Incident • Dry-out of the RPV

18. The Fukushima Daiichi Incident • Dry-out of the RPV • Heat-up of the exposed fuel

19. The Fukushima Daiichi Incident • At ~900°C • ~1/3 of Core uncovered • Fracture of the Cladding • Release of first fission products • At ~1200°C • ~1/2 of Core uncovered • Zirconium burns Steam • Zr + H20 ->ZrO + H2 • Strong core heat-up • 300-600kg Hydrogen • Strong Pressure buildup in containment

20. The Fukushima Daiichi Incident • Strong release of fission products • Xenon • Cesium • Iodine • …. • Aerosols (Smoke) • Large fraction of fission products get scrubbed in pressure suppression pool, not Xenon • Uranium/Plutonium remain in core • At ~1800°C • Melting of the cladding • Unknown if this stadium was reached

21. The Fukushima Daiichi Incident • Due to hydrogen, pressure build-up up to 8bar in containment • Venting of containment down to ~4 bar • Venting via pressure suppression pool removes significant amount of aerosols • Release of small amounts of Aerosols (Iodine, Cesium) and • most of radioactive noble gases (Xenon) and • Hydrogen

22. The Fukushima Daiichi Incident • Vented gas was released inside Reactor service floor • Hydrogen combustion blows of Service Floor • Explosion Unit 1: 14.3.2011 11:01AM • Explosion Unit 3: 14.3.2011 11:01AM • Concrete Reactor building unaffected • Explosion of the building spectacular, but minor importance • Deduced Informations • Service Floor ~8000m3 •  100 to 200kg H2 •  20% to 40% Core oxidation dailycaller.com

23. The Fukushima Daiichi Incident • Radiation released • Maximum ~1mSv/h on site after venting of unit 1 • Probably similar dose at Venting of Site 2 • Expected order of magnitude by German crisis documents • Rapid falling values to ~0.07mSv • Indicating main release was noble gases • INES4 classified • Most probably no land permanently contaminated

24. The Fukushima Daiichi Incident • Current Information • RPV Flooded by See water in all 3 Units • Containment flooded at least in Unit 1 • Liquid level stable • Further cooling of the containment by venting • Clogging of fuel by sea water? • Rough estimate after 100h by flooding by pure sea water • Core status • Unit1: Core damaged • Unit2: unknown • Unit3: Core oxidized, possibly damaged

25. Informations supplyed by Google.com GRS.de Yoshiaki Oka, Waseda university . . . .

26. ENDE der Folien Im Anschluss Orginal-Informationen von Yoshiaki Oka und weitere Folien über weiter denkbaren Unfallablauf, für welchen es bis jetzt keine Anzeichen gibt

27. TEPCO’s Nuclear Power Plants suffered from big earth quake of March 11,2011 Yoshiaki Oka Waseda university Prepared for the presentation at ISSCWR5 on March 14, 2011 from the request of the organizer based on the information until March 13 in Canada. Available Information is very limited. Recovery action is in progress. The presentation may contain misunderstandings.

28. The big earth quake Attached northern part of Japan at 2:46pm of March 11, 2011. Magnitude is 9 in Richter scale. The biggest in history. Some earth quakes occurred along the boundary of plates. Hundreds of km of the boundary moved, similar to the big earth quake in Indonesia. Big Tsunami (10m) attacked northern Japan and NPP. It was bigger than expected. There is no damage in the central Tokyo. Power plants including gas and coal fired ones were automatically shut down. NPPs were also automatically shut down.

29. Fukushima site 1 (1F) 6 units , Unit #1, #2 , and #3 in trouble. Unit #1: 460MWe BWR ,Unit #3,#2: 768MWe BWR 2:46pm March 11: The earth quake happened. Plants automatically shut down. Offsite power lost. Emergency DG started up. 3:41pm Emergency DG stopped due to loss of equipment cooling water. (Tsunami was bigger than expected.) All AC power was lostand consequential isolation from UHS, except for IC (isolation cooling system) in 1F1. RCIC in 1F 2 Blackout + (mostly) loss of UHS RCIC was available to makeup water in the initial stage. SAM (Severe Accident Management) prepared in the 90’s in place such as containment scrubbing venting, supply of water from portable water tank using Fire Protection pump or Fire Engine and inter-connection of power supply with other units. Site emergency announced. (After JCO accident, emergency law was settled. It requires report to the central government.) Evacuation up to 20km around 1F, 10km around 2F.

30. Summary of Site #1, Unit 1 and 3 Loss of All AC power. Partial core uncover (1-2m) occurred. Hydrogen generated by Zr-water reaction CV pressure increased and CVs were vented to maintain the integrity. Hydrogen detonation occurred in the upper part of the reactor buildings (unit 1 on March 12 and unit 2 on March 14). 14 workers injured. Area evacuated in 20km. Radiation levels are low, 1mSv/h highest at the site. (Dose limit of public: ImSv/y) Sea water with boric acid injected into RPV and CV. CV integrity is maintained. Large release will be not likely. Cores are covered by water now. Level 4 accident of IAEA.

31. Fukushima site #1 Unit 2 (1F2) Loss of all AC power. RCIC was in operation but is now lost. Low water level in RPV and High CV pressure continue. Mobile power supply is tried but not working well. CV vent my be considered. Fuel is covered by water (3am of March 14), but there is a threat to core uncovery. Depressurization of RPV, CV venting and Seawater injection are in preparation.

32. Fukushima site # 2 (2F)10-20km from site #1 4 units: 110MWe BWR Sea water pumps of unit 1,2 and 4 did not work due to Tsunami. The motors were being replaced unit by unit. Recovery of the cooling were successful for unit 1 at 3am and for unit 2 at 7am of March 14.