- Overview of roadmap
- Contaminated water processing
- Reduce radioactivity dosage and mitigate sea water contamination
- Fuel removal from the spent fuel pool
- Fuel debris removal plan
- Processing and disposal of radioactive waste
- Improvement of site environment for facilitation of work
- Area monitoring
- Investigation on Units
Reactor cooling
The cold shutdown condition will be maintained by cooling the reactor by water injection and measures to complement status monitoring will continue to be implemented.
Status of Progress Points(1) Temperatures inside the reactors
- Through continuous reactor cooling by water injection, the temperatures of the Reactor Pressure Vessel (RPV) bottom and the Primary Containment Vessel (PCV) gas phase have been maintained within the range of approx. 15 to 40℃ for the past month, though they vary depending on the unit and location of the thermometer.
(2) Release of radioactive materials from the Reactor Buildings
- The density of radioactive materials newly released from Reactor Building Units 1-4 in the air measured at site boundaries was evaluated at approx.1.3 x 10-9 Bq/cm3 for both Cs-134 and -137. The radiation exposure dose due to the release of radioactive materials was 0.03 mSv/year (equivalent to approx. 1/70 of the annual radiation dose by natural radiation (annual average in Japan: approx. 2.1 mSv/year)) at the site boundaries.
(3) Partial observation of containment vessel interior
- From the standpoint of supplementing the monitoring of reactor parameters, the interiors of the primary containment vessels of Units 1 and 2 were investigated to ascertain temperature, water level, dose and other conditions. Consideration is continuing to be given to conducting a similar interior investigation of Unit 3.
- An alternate temperature gauge for the Unit 2 reactor pressure vessel has been installed and additional temperature gauges installed at Units 1 and 2.
- To address leaks from pressure hoses and other such issues related to piping along the reactor injection line, the hoses have been replaced with more reliable polyethylene pipe.
- Appropriate backup facilities have been secured for the reactor coolant injection system (injection line pump: 3 systems; water source: 2 types; ensuring power sources from multiple buses, etc.). Even if the functionality of multiple systems involved in the injection of coolant into the reactor were to be lost simultaneously due to an accident, the injection of cooling water can be restarted using fire engines within three hours.
Investigation of Interior of Unit 1 PCV and Installation of Temperature and Water Level Gauges
- The interior of the primary containment vessel was filmed with a camera, and the dose, water level and other conditions were investigated (10/9~13).
- It was verified that the dose was a max. of approximately 11.1Sv/h, and the water level was approximately +2.8m above bottom of the containment vessel.
- Additional temperature and water level gauges were installed (10/13). The temperature gauges have been used as the monitoring temperature gauges specified by safety regulations since 12/3.
Investigation of Interior of Unit 2 PCV and Installation of Temperature Gauge
- The interior of the primary containment vessel was filmed with a camera, and the dose, water level and other conditions were investigated (1st :Jan 19; 2nd : May 26 - 27).
- It was verified that the dose was a max. of approximately 73Sv/h, and the water level was approximately +60cm above bottom of the containment vessel.
- An additional temperature gauge was installed (Sep 19). It has been used as the monitoring temperature gauge specified by safety regulations since Nov 6.
- There are future plans to enhance monitoring function by permanently installing temperature and water gauges similar to those in Unit 1 (scheduled for end of February).
Installation of Alternate Temperature Gauge at Unit 2
- Following the failure of the existing temperature gauge, an alternate temperature gauge (1 unit) was installed in addition to the temperature gauge already installed for monitoring (1 unit) (10/3).
- Because both temperature gauges display almost the same temperature (approx. 43~46℃), it was confirmed that there were no problems with the installation. The gauge has been used as the monitoring temperature gauge specified by safety regulations (11/6).
- As the thermometer installed at the Unit 2 RPV bottom after theearthquake had been broken, it was excluded from the monitoringthermometers (February 19).
- On April 17, removal of the broken thermometer failed and was suspended. To facilitate removal, tests to check rust formation and fixing are underway (from May 12).
- Some of the permanent supervisory instrumentation for PCV could not be installed in the planned locations due to interference with existing grating (August 13, 2013).
- Reinstallation after resolving the twisted cables from May 20-22 was failed and these instruments were removed on May 27. New instruments will be installed in June.
Nitrogen Seal on Unit 1 Suppression Chamber (S/C)
- Because it is assumed that gas from the time of the initial accident, which has a high hydrogen concentration, is remaining in the upper part of the S/C, nitrogen has been injected (10/23~early December) and (to 2%) the hydrogen concentration lowered sufficiently below the combustibility limit concentration※, which has further reduced risk of a hydrogen explosion.
Commencement of work to shorten the circulation loop
- Regarding the work to shorten the circulation loop, the operation of which is scheduled for the end of FY2014, as the facility design was completed, the preparatory work will commence from June.
Reinstallation of supervisory instrumentation for Unit 2 PCV
- Some of the supervisory instrumentation (thermometer and water-level gauge) for PCV could not be installed in the planned locations during the work in August 2013 due to interference with existing grating. Reinstallation after resolving the twisted cables from May 20-22 failed and these instruments were removed on May 27. New instruments will be installed in June.
Replacement of the thermometer at the bottom of Unit 2 RPV
- Removal and replacement of the thermometer installed at the bottom of Unit 2 RPV, which was broken in February 2014, failed in April and the operation was suspended. The estimated cause was fixing or added friction due to rust having formed. To help remove the thermometer, tests to check rust formation and fixing are underway (from May 12).
Future Challenges and Direction of Responses
Maintenance of Monitoring Functions for Long-Term Stable In-Core Environment
- An alternate temperature gauge (1 unit) has been installed to serve as the Unit 2 pressure vessel temperature gauge, and the insertion and installation of an additional temperature gauge through the TIP (traversing in-core probe) pipe is being studied in order to improve reliability.
- At Units 1 and 3 also, alternate temperature gauges need to be installed prior to that in preparation for failure of a temperature gauge. Because the dose needs to be reduced in the vicinity of the installation location, possible sites for installation of the alternate temperature gauges are being narrowed down in FY 2012.
Addressing Risks in Event of Earthquake or Tsunami
- With regard to earthquakes, it has been verified that there is sufficient seismic resistance to withstand an earthquake equivalent to the Tohoku-Chihou-Taiheiyo-Oki Earthquake (JMA seismic intensity scale 6+). Even if some of the equipment were to become unusable, appropriate backup equipment has been secured to be able to restart the injection of cooling water quickly.
- With regard to tsunami countermeasures, a provisional seawall has already been installed in preparation for a tsunami striking due to aftershocks. To provide for a case where a tsunami surpassing assumptions were to hit, dedicated diesel generators have been deployed to ensure power as well as backup coolant injection pumps and cooling water injection pumps on high ground in order to maintain reactor cooling function. Also, power-generating vehicles have been deployed to prepare for any power interruptions.
- In addition, fire engines have been deployed as alternative means for injecting cooling water should multiple backup systems become unusable.
- Moreover, as new information is obtained, it will be thoroughly addressed, including responding to reviews regarding standard earthquake ground motion.
Avoiding Remote Risk of Hydrogen Explosion
- To prevent any explosion of hydrogen generated from radiolysis of water inside the reactor pressure vessels at Units 1~3, nitrogen is continuing to be charged into the reactor pressure and containment vessels.
- The hydrogen concentration inside the containment vessels of Units 1~3 is monitored and managed so that the concentration does not exceed the combustibility limit concentration (4%) by adjusting the amount of nitrogen charged.
- Using a web camera, it is possible to monitor the pressure of injected nitrogen gas and the injected amount of nitrogen gas at the seismic-isolated building. In the event that unusual conditions are detected within these parameters or during an inspection, it will switch over to the standby facility. This includes valve manipulation or the switching over of the power supply.
| Unit | Description | Category | Date of issue | Link |
|---|---|---|---|---|
| Units 1-3 | Commencement of the Reactor Water Injection at Units 1-3 of Which the Source is Condense Storage Tank (CST) at Fukushima Daiichi Nuclear Power Station | Document & photos | 05 July 2013 | |
| Unit 1 & 2 & 3 | Confirmation of Reactor Water Injection by the CST Reactor Water Injection System Line of Unit 2 at Fukushima Daiichi Nuclear Power Station | Document | 04 July 2013 | |
| Unit 1 & 2 & 3 | Reliability Improvement of the Feed Water System for Reactor Injection at Units 1-3 at Fukushima Daiichi Nuclear Power Station | Document | 19 February 2013 | |
| Unit 3 | Water Injection to the Reactor Utilizing the Reactor Water Injection Pump in the Turbine Building in the Case of Power Supply Suspension at Fukushima Daiichi Nuclear Power Station | Document | 13 November 2012 | |
| Unit 1 & 2 & 3 | The Reactor Pressure Vessel Temperature and the Amount of Water Injection to Reactor at Fukushima Daiichi Nuclear Power Station Unit 1 - 3 (Reference) | Document | 13 September 2012 | |
| Unit 1 & 2 & 3 | The Reactor Pressure Vessel Temperature and the Amount of Water Injection to Reactor at Fukushima Daiichi Nuclear Power Station Unit 1 - 3 (Reference) | Document | 12 September 2012 | |
| Unit 1 & 2 & 3 | Decrease in the Reactor Injection Amounts at Unit 1-3 at Fukushima Daiichi Nuclear Power Station (Follow-up Report) | Document & photos | 11 September 2012 | |
| Unit 1 & 2 & 3 | The Reactor Pressure Vessel Temperature and the Amount of Water Injection to Reactor at Fukushima Daiichi Nuclear Power Station Unit 1 - 3 (Reference) | Document | 11 September 2012 | |
| Unit 1 & 2 & 3 | The Reactor Pressure Vessel Temperature and the Amount of Water Injection to Reactor at Fukushima Daiichi Nuclear Power Station Unit 1 - 3 (Reference) | Document | 10 September 2012 | |
| Unit 1 & 2 & 3 | The Reactor Pressure Vessel Temperature and the Amount of Water Injection to Reactor at Fukushima Daiichi Nuclear Power Station Unit 1 - 3 (Reference) | Document | 07 September 2012 | |
| Unit 1 & 2 & 3 | The Reactor Pressure Vessel Temperature and the Amount of Water Injection to Reactor at Fukushima Daiichi Nuclear Power Station Unit 1 - 3 (Reference) | Document | 06 September 2012 | |
| Unit 1 & 2 & 3 | The Reactor Pressure Vessel Temperature and the Amount of Water Injection to Reactor at Fukushima Daiichi Nuclear Power Station Unit 1 - 3 (Reference) | Document | 05 September 2012 | |
| Unit 1 & 2 & 3 | The Reactor Pressure Vessel Temperature and the Amount of Water Injection to Reactor at Fukushima Daiichi Nuclear Power Station Unit 1 - 3 (Reference) | Document | 04 September 2012 | |
| Unit 1 & 2 & 3 | The Reactor Pressure Vessel Temperature and the Amount of Water Injection to Reactor at Fukushima Daiichi Nuclear Power Station Unit 1 - 3 (Reference) | Document | 03 September 2012 | |
| Unit 1 & 2 & 3 | Decrease in the Reactor Injection Water Amounts at Unit 1-3 of Fukushima Daiichi Nuclear Power Station | Document | 03 September 2012 | |
| Unit 1 & 2 & 3 | Fukushima Daiichi Nuclear Power Station Unit 1-3 RPV Temperatures and Reactor Injection Water Flow Rates (Reference) | Document | 31 August 2012 | |
| Unit 1 & 2 & 3 | Operational Commencement of the Refrigerators Installed by the Treatment Water Buffer Tank at Fukushima Daiichi Nuclear Power Station | Document & photos | 17 July 2012 | |
| Unit 1 & 2 & 3 | Change in the Water Injection Amounts at Fukushima Daiichi Nuclear Power Station towards Summer 2012 | Document | 25 May 2012 | |
| Unit 2 | Results of Survey on Thermometer at Unit 2 Reactor, Fukushima Daiichi NPS | Document | 03 March 2012 | |
| Unit 2 | Fukushima Daiichi NPS Unit 2 The temperature of the lower part of the reactor pressure vessel (upper part of the bottom head／upper part of support skirt junction) (Reference) | Document | 03 March 2012 | |
| Unit 1 & 2 & 3 | Reactor Water Injection Line from the Reactor Water Injection Pump in the Turbine Building of Fukushima Daiichi NPS | Document | 26 January 2012 | |
| Unit 1 to 3 | Test Run of Reactor Injection Pump in the Turbine Building of Unit 1 to 3 | Document | 27 December 2011 | |
| Unit 1 | Increase in the amount of water to the reactor of Unit 1 in Fukushima Daiichi Nuclear Power Station | Document | 28 October 2011 | |
| n/a | Accumulated water treatment analysis result | Document | 21 October 2011 | |
| Unit 2 | Operation of Filling Water to Reactor Water Level Gauge in Unit 2 at Fukushima Daiichi Nuclear Power Station | Document | 21 October 2011 | |
| n/a | Water injection practice at Fukushima Daiichi Nuclear Power Station | photos | 12 October 2011 | |
| n/a | Reactor and Fuel Status in Case of a Reactor Water Injection System Malfunction | Document | 01 October 2011 | |
| Unit 2 and Unit 3 | Increase of water injection through the core spray system of Unit 2 and Unit 3 of Fukushima Daiichi Nuclear Power Station | Document | 16 September 2011 | |
| Unit 2 | Adjustment of the water injection amount after the addition of the injection line (reactor feed water system → reactor feed water system + Core Spray System) to the reactor of Unit 2, Fukushima Daiichi Nuclear Power Station | Document | 14 September 2011 | |
| Units 1-3 | Fukushima Daiichi Nuclear Power Plant Units 1-3 Additional installation of the Reactor coolant injection mini flow line | Document | 11 September 2011 | |
| Unit 1-3 | Water injection into the reactor of Fukushima Daiichi NPS Unit 1-3 | Document | 09 September 2011 | |
| Unit 3 | Fukushima Daiichi Nuclear Power Station Monitoring Result Regarding Water Injection for the Reactor through Core Spray System of Unit 3 (air dose rate) | Document | 03 September 2011 | |
| Unit 3 | Flow Rate Adjustment after Addition of CS Line (FDW→FDW+CS) | Document & photos | 31 August 2011 | |
| Unit2 | Outline drawing of High Pressure Core Spray System Unit2 of Fukushima Daini Nuclear Power Station | Document | 30 August 2011 | |
| Unit 3 | Fukushima Daiichi Nuclear Power Station - Unit 3 Diversification of A Method of Water Injection to Nuclear Reactor by Adding Core Spray System Line | Document | 23 August 2011 | |
| Unit 1-3 | Schematic Drawing of the Reactor Water Injection System at Unit 1-3, Fukushima Daiichi Nuclear Power Station | Document | 16 August 2011 | |
| Unit 1-4 | System outline of circulating injection cooling | Document | 01 July 2011 | |
| Unit 1-4 | Outline of Circulation and Injection System of Cooling Water | Document | 28 June 2011 | |
| Unit 5 | Temperature of Reactor Water and Spent Fuel Pool, Unit 5 Fukushima Daiichi Nuclear Power Station | Document & photos | 29 May 2011 | |
| Unit 1-3 | Decay Heat of Fuel in Reactor(changes in a half year period after the earthquake) | Document | 26 May 2011 | |
| Unit 3 | Diagram of Water Injection to the Reactor Unit 3 of Fukushima Daiichi Nuclear Power Station | Document | 08 May 2011 |
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