Progress toward decommissioning:Fuel removal from the spent fuel pool

Work to help remove spent fuel from the pool is steadily progressing while ensuring seismic capacity and safety. The removal of spent fuel from the Unit 4 pool commenced on November 18, 2013 and was completed on December 22, 2014.

Fuel removal from the Unit 4 spent fuel pool

  • In the Mid- and Long-Term Roadmap, the target of Phase 1 involved commencing fuel removal from inside the spent fuel pool (SFP) of the 1st Unit within two years of completion of Step 2 (by December 2013). On November 18, 2013, fuel removal from Unit 4, or the 1st Unit, commenced and Phase 2 of the roadmap started.
  • On November 5, 2014, within a year of commencing work to remove the fuel, all 1,331 spent fuel assemblies in the pool had been transferred.
  • The transfer of the remaining non-irradiated fuel assemblies to the Unit 6 SFP was completed on December 22, 2014. 2 of the non-irradiated fuel assemblies were removed in advance in July 2012 for fuel checks. This marks the completion of fuel removal from the Unit 4 Reactor Building.
  • Based on this experience, fuel assemblies will be removed from Unit 1-3 pools.


Check of the soundness of the Reactor Building

  • Regular inspections have been conducted, which have confirmed that the soundness of the Reactor Building has been maintained.


Inspecting the soundness of fresh fuel (unirradiated fuel) inside the Unit 4 SFP

  • In order to inspect the status of fuel corrosion to fresh fuel assemblies were removed from the pool and soundness was evaluated (August 27 through the 29th)
  • The inspection revealed no significant information or damage to the fuel rods were fuel structures, and no corrosion was found, and it was therefore concluded that material corrosion will not have a large impact on fuel removal.


Main works to help remove spent fuel at Unit 3

  • The removal of rubble is underway (from December 17). From April 19, removal of the fuel-handling machine commenced. In May, a supplementary traveling hoist frame and handrails on the hoist were removed.
  • Measures to reduce the radiation dose (decontamination and shielding) on the Reactor Building 5th floor (operating floor) have been underway since October 15, 2013.
  • To facilitate the installation of a cover for fuel removal, installation of the gantry was completed (March 13, 2013). Removal of rubble from the roof of the Reactor Building was completed (October 11, 2013). Currently, toward the installation of a cover for fuel removal and the fuel-handling machine on the operating floor(*1), measures to reduce the radiation dose (decontamination and shielding) have been started (from October 15, 2013). Removal of large rubble from the SFP is also underway (from December 17, 2013).

(*1) Operating floor: During regular inspection, the roof over the reactor is opened while on the operating floor, fuel inside the core is replaced and the core internals are inspected.


Removal of debris from top of Unit 3, Unit 4 reactor buildings and construction of Unit 4 cover for fuel removal

  • Debris is currently being removed from the top of the Unit 3 reactor building in preparation for fuel removal from the spent fuel pool ( to be completed around the end of FY2012)
  • Unstable pieces of steel girder fell into the fuel pool during debris removal at Unit 3. A report on the cause of this incident and reoccurrence prevention countermeasures was submitted to the Nuclear Regulatory Commission (10/3,19 and 11/15). Debris removal work will continue safely and steadily based on this report.
  • At Unit 4 building debris was removed on July 11 and large equipment was removed between July 24 and October 2. debris is currently being gathered (until December). In conjunction, a fuel removal cover continues to be built (to be finished around the middle of FY2013)


Unit 3, Unit 4 SFP debris dispersion survey

  • Underwater cameras and remotely operated vehicles (ROV) were used to survey the dispersion of debris within the spent fuel pools.
  • An underwater debris removal plan prior to spent fuel removal shall be proposed based on the results of the survey.


Main works to help remove spent fuel at Unit 1

  • Regarding Unit 1, to remove rubble from the top of the operating floor, there are plans to dismantle the cover over the Reactor Building.
  • Two roof panels of the Unit 1 Reactor Building (R/B) were removed to facilitate investigation of the rubble status on the R/B top floor.
  • On March 16, the preparatory work for dismantling the Reactor Building cover commenced. The dismantling will commence on May 15. Before starting the dismantling work, measures to prevent spreading will be steadily implemented.
  • To facilitate the early removal of fuel and fuel debris from the SFP, the cover over the Reactor Building will be dismantled to accelerate the removal of rubble on the operation floor. The radiation dose on the site boundaries will also increase compared to before the dismantling. However, through measures to reduce the release, the estimated impact of the release from Units 1 to 3 on the site boundaries (0.03mSv/year) will be limited.


Main works to help remove spent fuel at Unit 2

  • Regarding Unit 2, to prevent risks of reworking due to change in the fuel debris removal plan, the plan continues to be examined within a scope not affecting the scheduled commencement of removal.

Unit 1, Unit 2 operating floor survey

  • A survey of the operating floors was conducted in order to help with the deliberation of fuel removal from spent fuel pools.
  • At Unit 1 a camera attached to a balloon was used to take footage and to measure dose levels. A maximum dose of 53.6mSv/h was measured at a 1 m from the operating floor.
  • At Unit 2 a remote-controlled robot was used to take footage, and measure radiation levels and temperature/humidity levels. A maximum dose of 880mSv/h was measured at the top of the reactor well.


Desalination of Unit 1~4 spent fuel pools

  • Unit 1: Saline levels are low enough since seawater was not injected
  • Unit 2: Desalination completed on July 2. Water quality being monitored through periodic sampling.
  • Unit 3: Being desalinated with desalination equipment
  • Unit 4: Desalination completed on October 12. Water quality being monitored through periodic sampling
  • Close range chloride ion concentration: Unit 1 5ppm(7/17), Unit 2 28ppm(10/18)Unit 2 72ppm(10/18), Unit 49ppm(10/18)(Below technical specification limits of 100ppm)

Replacement of fuel rack for common pool

  • An open space will be maintained in the common pool (Transfer to the temporary dry cask storage facility)
  • The common pool has been restored to a condition allowing it to re-accommodate fuel to be handled (November 2012)
  • Loading of spent fuel stored in the common pool to dry casks commenced (June 2013)
  • Fuel removed from the Unit 4 spent fuel pool began to be received (November 2013)

(*2) Cask: Transportation container for samples and equipment, including radioactive materials.


Future issues and the direction of countermeasures

Handling the risks associated with earthquakes and tsunami

  • Alternative coolant injection equipment, such as concrete pump trucks, having been deployed so as to enable sufficient time to restore cooling function if the fuel pools become unable to be cooled due to damage to primary/secondary pump pipes, etc., by an earthquake or tsunami.
    • In this instance, it has been concluded that a minimum of 16 days (Unit 4 ) would be required to reach a point where fuel pool water level is maintained at a certain level (2m from top of active fuel: water level at which shielding is deemed effective) since water temperatures will rise and water levels will decrease.
    • Even if it is difficult to cool the pools using emergency coolant injection equipment, and concrete pump trucks, etc., are used to cool the pools, cooling could be restored in approximately 6 hours even if cooling function is lost
  • Furthermore, every effort shall be made to comply with newly gained knowledge, including the handling of changes to the reference ground motion.

 

Issues that may impact work schedules

  • The following issues that may impact work schedules must be resolved in order to carry out fuel removal as planned.
    • Debris removal work: the status of falling debris within the pools and radiation levels have yet to be confirmed which may prolong work and add to it.
    • Fuel removal cover construction: many uncertainties, such as building damage and radiation levels, exist that may prolong or add to work.
    • Pool fuel removal work: if more of the fuel than expected is damaged, or if the extent of damage to the fuel is greater than expected, work may be prolonged or added to.

Unit 1, Unit 2 fuel removal

  • Detailed plans shall be proposed based on a survey of debris at Unit 1 while acquiring knowledge and experience through removing debris at Unit 3 and Unit 4, the operability and malfunctions of remote operated equipment and fuel surveys, etc.
  • Detailed plans for the inspection, repair, and fuel removal at Unit 2 shall be proposed based on the establishment of remote decontamination technology and upon decontaminating the inside of the building, shielding it and conducting surveys at a point in time when fuel handling equipment can be approached.

Fuel removal from the spent fuel pool

Common

UnitDescriptionCategoryDate of issueLink
n/a Transportation of a Dry Storage Cask from the Common Pool Building to the Temporary Dry Cask Storage Facility in Fukushima Daiichi Nuclear Power Station Document & photos 04 April 2013
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Units 1-4 Cask Transportation to Fukushima Daiichi Nuclear Power Station by Way of the Port of Hirono Thermal Power Station Document & photos 28 February 2013
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n/a Inspection of the Spent Fuel Appearance and the Fuel Rack in the Spent Fuel Common Pool at Fukushima Daiichi Nuclear Power Station Document 20 December 2012
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Unit 1 & 2 & 3 & 4 & 5 Response training to abnormal conditions that occurred at Spent Fuel Pool per the Safety Regulation photos 26 January 2012
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Unit 2 & 3 & 4 Completion of radioactive materials removal procedure in the spent fuel pool of Unit 2 at Fukushima Daiichi Nuclear Power Station Document 06 December 2011
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Unit 1 & 2 & 3 & 4 Partially correction of amount injected water to spent fuel pool at Fukushima Daiichi Nuclear Power Station Document 01 May 2011
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Unit 1

UnitDescriptionCategoryDate of issueLink
Unit 1 Results of Reinvestigation of Unit 1 Operation Floor at Fukushima Daiichi Nuclear Power Station Document 24 October 2012
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Unit 1 Water injection to reactor well and drier separator pool of Unit 1 in 1F Document 20 June 2011
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Unit 2

UnitDescriptionCategoryDate of issueLink
Unit 2 Unit 2 Spent Fuel Pool Desalination Completed at Fukushima Daiichi Nuclear Power Station Document & photos 02 July 2012
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Unit 2 Installation Status of Radioactive Material Removal Facility at the Unit 2’s Spent Fuel Pool of Fukushima Daiichi Nuclear Power Station photos 07 November 2011
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Unit 2 Installation of Radioactive Material Removal Instruments for the Spent Fuel Pool of Unit 2, Fukushima Daiichi Nuclear Power Station Document 06 November 2011
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Unit 3

UnitDescriptionCategoryDate of issueLink
Unit 3 Debris Removal from the Upper Part of Unit 3 Reactor Building at Fukushima Daiichi Nuclear Power Station Renewal of the Protection Installed on the Spent Fuel Pool and the Skimmer Surge Tank Hatch Document & photos 27 May 2013
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Unit 3 Debris Removal from the Upper Part of Unit 3 Reactor Building at Fukushima Daiichi Nuclear Power Station Document & photos 22 April 2013
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Unit 3 Desalting Completed at Unit 3 Spent Fuel Pool at Fukushima Daiichi Nuclear Power Station Document & photos 18 March 2013
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Unit 3 Investigation of the Inside of Spent Fuel Pool Utilizing an Underwater Camera as Part of Debris Removal from the Upper Part of Unit 3 Reactor Building at Fukushima Daiichi Nuclear Power Station Document & photos 13 February 2013
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Unit 3 Possibility of Debris (Assumed to be the Fuel Handling Machine Mast) Sinking in the Spent Fuel Pool at Debris Removal from the Upper Part of the Unit 3 Reactor Building at Fukushima Daiichi Nuclear Power Station(2) Document & photos 08 February 2013
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Unit 3 Possibility of Debris (Assumed to be the Fuel Handling Machine Mast) Sinking in the Spent Fuel Pool at Debris Removal from the Upper Part of the Unit 3 Reactor Building at Fukushima Daiichi Nuclear Power Station Document & photos 08 February 2013
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Unit 3 Debris Removal from the Upper part of Unit 3 Reactor Building at Fukushima Daiichi Nuclear Power Station: Removal of Steel Truss Debris Document & photos 06 February 2013
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Unit 3 Debris Removal from the Upper Part of Unit 3 Reactor Building at Fukushima Daiichi Nuclear Power Station Document & photos 04 February 2013
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Unit 3 Presumption of Refueling machine’s situation based on the result Unit 3 Spent Fuel Pool investigation Document & photos 15 October 2012
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Unit 3 Investigation of the Inside of Unit 3 Spent Fuel Pool using an Underwater Camera at Fukushima Daiichi NPP Document & photos 15 October 2012
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Unit 3 Investigation of the Inside of Unit 3 Spent Fuel Pool Using an Underwater Camera at Fukushima Daiichi Nuclear Power Station (September 26) Document & photos 26 September 2012
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Unit 3 Investigation of the Inside of Unit 3 Spent Fuel Pool Using an Underwater Camera at Fukushima Daiichi Nuclear Power Station Document & photos 25 September 2012
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Unit 3 Investigation of the Inside of the Spent Fuel Pool for Fuel Removal from the Upper Part of Unit 3 Reactor Building at Fukushima Daiichi Nuclear Power Station Document & photos 13 September 2012
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Unit 3 Survey on the inside of Unit 3 Spent Fuel Pool for Removal of Debris ,Fukushima Daiichi Nuclear Power Station Document & photos 13 April 2012
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Unit 3 Completion of Removal of Radioactive Materials from Unit 3 Spent Fuel Pool at Fukushima Daiichi Nuclear Power Station Document 02 March 2012
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Unit 3 Strainer washing due to Suction pressure decrease of Primary coolant system pump, in Spent fuel pool closed loop cooling system at Fukushima Daiichi Nuclear Power Station Unit 3 Document 07 November 2011
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Unit 4

UnitDescriptionCategoryDate of issueLink
Unit 4 Work Procedure Review Following Unused Fuel Removal at Fukushima Daiichi NPS Unit 4 Document 25 November 2013
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Unit 4 Current Status of Fukushima Daiichi NPS Unit 4 Fuel Removal Document & photos 18 November 2013
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Unit 4 Operation of Fuel Removal from Unit 4 Spent Fuel Pool at Fukushima Daiichi NPS Document & photos 15 November 2013
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Unit 4 Summary of results of external and internal reviews made on the operation to remove fuel at Fukushima Daiichi NPS Unit 4 Document 15 November 2013
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Unit 4 Safety Measures etc. concerning Fuel Removal from Unit 4 in Fukushima Daiichi NPS Document 15 November 2013
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Unit 4 Operation to Remove Spent Fuel from Unit 4 Spent Fuel Pool at Fukushima Daiichi NPS Document & photos 13 November 2013
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Unit 4 Results of Inside Investigation of the Reactor Well, the RPV and the Spent Fuel Pool at Unit 4 in Fukushima Daiichi Nuclear Power Station Document & photos 09 August 2013
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Unit 4 Inside Investigation of the Reactor Well, the RPV and the Spent Fuel Pool of Unit 4 at Fukushima Daiichi Nuclear Power Station Document 02 August 2013
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Unit 4 Completion of Outer Wall and Exterior Roof Panel Installation for the Fuel Removal Cover at Unit 4 in Fukushima Daiichi Nuclear Power Station Document & photos 22 July 2013
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Unit 4 Completion of the Steel Frame Construction for the Cover to be Installed for Fuel Removal at Unit 4 at Fukushima Daiichi Nuclear Power Station Document & photos 29 May 2013
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Unit 4 Progress of the Steel Frame Construction for the Cover to be Installed for Fuel Removal at Unit 4 at Fukushima Daiichi Nuclear Power Station Document & photos 11 April 2013
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Unit 4 Steel Frame Construction for the Cover to be Installed for Fuel Removal at Unit 4 at Fukushima Daiichi Nuclear Power Station: Completion of the Third Layer of Steel Frame Document & photos 13 March 2013
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Unit 4 Steel Framing Construction for the Cover to be Installed for Fuel Removal at Unit 4 at Fukushima Daiichi Nuclear Power Station: Installation of 2 Columns of the First Layer Document & photos 08 January 2013
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Unit 4 Steel Beam Framing for the Cover to be Installed for Fuel Removal at Unit 4 at Fukushima Daiichi Nuclear Power Station Document 07 January 2013
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Unit 4 Desalting Completed at Unit 4 Spent Fuel Pool at Fukushima Daiichi Nuclear Power Station Document & photos 12 October 2012
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Unit 4 The Soundness of Unit 4 Reactor Building and Spent Fuel Pool at Fukushima Daiichi Nuclear Power Station Document & photos 30 August 2012
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Unit 4 Results of the Second Soundness Inspection of Unit 4 Reactor Building at Fukushima Daiichi Nuclear Power Station Document & photos 30 August 2012
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Unit 4 Soundness Investigation of the Unused (Unirradiated) Fuel Removed from Unit 4 Spent Fuel Pool at Fukushima Daiichi Nuclear Power Station Document & photos 29 August 2012
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Unit 4 Soundness Investigation of the Unused (Unirradiated) Fuel Removed from Unit 4 Spent Fuel Pool at Fukushima Daiichi Nuclear Power Station Document & photos 28 August 2012
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Unit 4 Unused Fuel Removal from Unit 4 Spent Fuel Pool at Fukushima Daiichi Nuclear Power Station photos 19 July 2012
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Unit 4 Completion of Debris Removal from the Upper Part of Unit 4 Reactor Building at Fukushima Daiichi Nuclear Power Station Document & photos 11 July 2012
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Unit 4 Unit 4 Spent Fuel Pool Circulation Cooling System UPS Inside Inspection Document & photos 06 July 2012
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Unit 4 Unit 4 Spent Fuel Pool Alternative Cooling System Suspended at Fukushima Daiichi Nuclear Power Station(Occurred on June 30, 2012) Document 02 July 2012
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Unit 4 The Protection Platform Installation on Unit 4 Spent Fuel Pool at Fukushima Daiichi Power Station Document & photos 15 June 2012
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Unit 4 The Protection Platform Added on Unit 4 Spent Fuel Pool at Fukushima Daiichi Power Station Document & photos 08 June 2012
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Unit 4 Motor Cable Connection for the Secondary System Circulation Pump (B) of Unit 4 Spent Fuel Pool Circulation Cooling System at Fukushima Daiichi Nuclear Power Station photos 08 June 2012
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Unit 4 The integrity evaluation of the reactor building at unit4 in the Fukushima Daiichi nuclear power station Document & photos 16 May 2012
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Unit 4 Soundness Verification of Unit 4 Reactor Building at Fukushima Daiichi Nuclear Power Station Document 16 May 2012
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Unit 4 Set up of Manned Heavy Machinery on the upper side of Unit 4 Reactor Building In the Fukushima Daiichi Nuclear Power Station Document & photos 16 April 2012
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Unit 4 Fukushima Daiichi Nuclear Power Station, Unit 4 Water Level Measurement for the Verification of Reactor Building Health Document 13 April 2012
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Unit 4 Removal Works of Debris on the Upper Part of the Reactor Building of Unit 4 in Fukushima Daiichi Nuclear Power Station photos 06 March 2012
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Unit4 Resumption of desalting by ion exchanging device at spent fuel pool of Unit4 at Fukushima Daiichi Nuclear Power Plant Document & photos 29 November 2011
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Unit4 Coverage of Spent Fuel Pool for removal of debris on the roof of Reactor Building at Unit 4, Fukushima Daiichi Nuclear Power Station (image) Document & photos 27 September 2011
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Unit4 Unit 4, Fukushima Daiichi NPS circulating cooling system for Spent Fuel Pool Water seepage from a flexible hose Document 08 September 2011
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Unit4 Unit 4 Spent Fuel Pool Circulating Cooling System Oozing Water from Flexible Hose Document 23 August 2011
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Unit4 Desalting Facilities for Spent Fuel Pool at Unit 4, Fukushima Daiichi Nuclear Power Station photos 20 August 2011
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Unit4 Installation of a Salt Removal System at Spent Fuel Pool of Unit 4, Fukushima Daiichi Nuclear Power Station Document 16 August 2011
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Unit4 Completion of Installation of Supporting Structure under the Bottom of the Spent Fuel Pool in the Reactor Building at Fukushima Daiichi Nuclear Power Station Unit 4 Document & photos 30 July 2011
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Unit4 Spent Fuel Pool in Reactor Building (5th floor), Unit 4, Fukushima Daiichi Nuclear Power Station photos 01 July 2011
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Unit4 R/B, Unit 4, Fukushima Daiichi Nuclear Power Station Installation work of supporting structure at the bottom of Spent Fuel Pool (Completion of installation of steel support pillars) Document & photos 20 June 2011
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Unit4 Alternative water injection line to Unit 4 spent fuel pool Document 16 June 2011
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