Subject: TEPCO Earthquake Information Update on June 8: Report of Japanese Government to the IAEA Ministerial Conference on Nuclear Safety
Dear Friends,
Please see the following updates on Fukushima Daiichi NPS and Fukushima Daini NPS [Fukushima Daiichi](1)Report of Japanese Government to the IAEA Ministerial Conference on Nuclear Safety
- The Accident at TEPCO's Fukushima Nuclear Power Stations -(2) Improvement of Work Environment in Unit 2 Reactor Building
(3) Unit 4 Reactor Building Reinforcement Work Progress
(4) Submission of the Report on Transfer of High Level Radioactive Wastewater Accumulated in the Fukushima Daiichi NPS to the Centralized Radiation Waste Treatment Facility
(5) Power Center Failure at Unit 1,2
[Fukushima Daini](6) Plans to Discharge Accumulated Water in Turbine Buildings
Contacts:
TEPCO Washington Office: 202-457-0790
Kenji Matsuo, Director and General Manager
Ikuo Nishimura, Deputy General Manager,
Masayuki Yamamoto, Manager, Nuclear Power Programs
[Fukushima Daiichi](1) Report of Japanese Government to the IAEA Ministerial Conference on Nuclear Safety - The Accident at TEPCO's Fukushima Nuclear Power Stations –
ü The Japanese Government submitted a report to the IAEA on the Fukushima Accident. The report is posted on below link. Please note the full report is about 600 pages.
http://www.kantei.go.jp/ü Although we recognize the report as “a preliminary” (in page I-2), we will study this report thoroughly and take necessary actions. Also we will conduct an in-depth and comprehensive internal investigation of the accident, learn from the lessons and make the results public.
ü 28 lessons in 5 categories are summarized in the report.
1. Strengthen preventive measures against a severe accident
(1) Strengthen measures against earthquakes and tsunamis
(2) Secure power supply
(3) Secure robust cooling functions of reactor and PCV
(4) Secure robust cooling functions of spent fuel pools
(5) Thorough accident management (AM) measures
(6) Response to issues concerning the siting with more than one reactor
(7) Consideration on placements of NPS in basic design
(8) Ensuring the water tightness of essential equipment facilities
2. Enhancement of response measures against severe accidents
(9) Enhancement of prevention measures of hydrogen explosion
(10) Enhancement of containment venting system
(11) Improvement of accident response environment
(12) Enhancement of the radiation exposure management system at accident
(13) Enhancement of training responding to severe accident
(14) Enhancement of instrumentation to identify the status of reactors and PCVs
(15) Central control of emergency supplies and equipment and setting up rescue team
3. Enhancement of nuclear emergency response
(16) Response to combined emergency of both large-scale natural disaster and prolonged nuclear accident
(17) Reinforcement of environment monitoring
(18) Establishment of clear division of labor between relevant central and local organizations
(19) Enhancement of communication relevant to the accident
(20) Enhancement of response to assistance by other countries and communication to the international community
(21) Adequate identification and forecast of the effect of released radioactive materials
(22) Clear definition of widespread evacuation area and radiological protection guideline in nuclear emergency
4. Reinforcement of safety infrastructure
(23) Reinforcement of safety regulatory bodies
(24) Establishment and reinforcement of legal structure, criteria and guidelines
(25) Human resources for nuclear safety and nuclear emergency preparedness and response
(26) Securing independency and diversity of safety system
(27) Effective use of probabilistic safety assessments (PSA) in risk management
5. Raise awareness of safety culture
(28) Raise awareness of safety culture
(2) Improvement of Work Environment in Unit 2Reactor Building
ü Based on the data collected in the Unit 2 reactor building on June 4, we decided to implement work environment improvement like we have done at Unit 1 in early May.
ü After airborne radioactive materials and humidity are reduced enough for workers to enter in the building, we will start pipe connection for nitrogen injection, calibrate water level instrumentations and install an alternative reactor cooling system.
[Schedule]
- Installation of temporary filtration systems: June 7 – 8
- Installation of temporary power supply equipment: June 9 – 11
- Setting up Ducts (intake and exhaust): June 7 – 10
- Installation of Air-houses: June 8 – 10
- Operation of Temporary Filtration Systems: June 11 – (about 3 days)
[Survey data at 5 m inside of the North Air-lock in the first floor of the reactor building (June 4)]
- I-131: 4.2×10-2 Bq/cm3
- Cs-134: 5.8×10-2 Bq/cm3
- Cs-137: 5.6×10-2 Bq/cm3
- Temperature: 34 – 35 C (94 F)
- Humidity: 99.9 %
ü Lessons learned from the experience of similar work at Unit 1:
Ø It is possible to see airborne radioactivity increases because of spread of dust when an exhauster starts operation.
Ø I-131 will not decrease by this operation because it generates from floor and wall.
ü We plan to continue operate the filtration system until the airborne radioactivity decreases to below 10-2 Bq/cm3, criteria for enter into the building without full-face mask, or at the point where we see no further decrease of radioactivity.
Ø Notification Limits for radiation workers to work without full-face mask are:
² I-131: 1×10-3 Bq/cm3
² Cs-134: 2×10-3 Bq/cm3
² Cs-137: 3×10-3 Bq/cm3
ü Our estimate of radioactivity to be released when we open air-locks is about 2.3 x 1010 Bq.
Ø Radioactivity in the building: 0.36 Bq/cm3 x Volume of the building: 65,000 m3
Ø Based on the data on June 4, 3 moths average radioactivity at the site boundary is estimated well below the legal limits. Effective dose at the site boundary will be 1.7 x 10 -2 micro Sv.
² I-131: 6.6×10-8 Bq/cm3 [Legal Limit] 5.0×10-6 Bq/cm3
² Cs-134: 8.0×10-8 Bq/cm3 [Legal Limit] 2.0×10-5 Bq/cm3
² Cs-137: 7.4×10-8 Bq/cm3 [Legal Limit] 3.0×10-5 Bq/cm3
[The improvement plan of working environment by an ambient air filtration system]
(3) Unit 4 Reactor Building Reinforcement Work Progress
ü We are installing support pillars under the spent fuel of Unit 4. In total 32 pillars are to be installed by the end of June, then we will construct walls surrounding the pillars.
(4) Submission of the Report on Transfer of High Level Radioactive Wastewater Accumulated in the Fukushima Daiichi NPS to the Centralized Radiation Waste Treatment Facility (CRWTF)
ü We had been transferring the high level radioactive wastewater to the Process Main Building and the Miscellaneous Solid Waste Volume Reduction Treatment Building (HIT Building) in CRWTF. However, we suspended the transfer because the amount of wastewater almost reached the planned storage level at the Process Main Building and there was a possibility that the wastewater leaks to the adjacent underground corridor in HIT Building.
ü In such a situation, as the paddle water in the Turbine Buildings of Units 2 and 3 were increasing, in order to prevent wastewater leakage to outside, we reconsidered the water storage level in the Process Main Building and reported the result to NISA on June 4.
ü At 6:39 pm on June 4, we started to transfer the wastewater in the Turbine Building of Unit 2 to the Process Main Building. As for Unit 3, at 6:26 pm on June 5, we started to transfer the water into the condenser of Unit 3.
ü In order to lower the risks of leakage of the wastewater in the Turbine Buildings of Unit 2 and 3 to the outside, we reconsidered and set new limit for the water storage level in the Process Main Building and reported the result to NISA on June 8.
May 15, 2011 | June 4, 2011 | June 8, 2011 | |
Transfer Volume | Approx. 10,000m3 | Approx. 11,500m3 | Approx. 14,200m3 |
Criteria | Up to the first basement, floor level （OP3700） | Up to the first basement, bottom of penetrated area（OP4200） | Up to 1.4m above the floor, B1（OP5100） |
ü The water level of high level wastewater of Unit 2 and 3 tends to be increasing due to injection of water to reactors. To prevent possible leakage to the environment, transfer and storage is being carried out to CRWTF. However, if the transfer is kept suspended longer, the risk of leakage will increase as the water level may increase beyond OP4000, before the Radioactivity Treatment System commences its operation (after June 15).
ü Therefore, we transferred 1,500m3 of the high level wastewater in the Turbine Building, Unit 2. Based on the criteria of June 4, 2011. After termination of transfer, the water level in the Turbine Building of Unit 2 is expected to increase again. As such, we are planning to transfer wastewater to the condenser of Unit 1.
ü As for the wastewater in the Turbine Building of Unit 3, we are transferring to the condenser of Unit 3. The water level is showing slight decrease.
ü While we can defer the time when the water level of the high level wastewater reach OP4000 by transferring wastewater to condensers for both Units 2 and 3, there is still possibility that the water level exceeds OP4000 and the water leaks to the outside of the system.
ü So we revised the water storage level criteria in the Process Main Building to 1.4 m above B1 floor (OP5100). By revising the storage level criteria in the Main Process Building and transferring additional 2,700m3 of wastewater, it will take five days before the water level in the Turbine Buildings of Unit 2 and 3 reach OP4000, therefore the risk of possible leakage is reduced.
[Figure] Water Level in trenches connecting CRWTF buildings (OP5100 is the new criteria)
(5) Power Center Failure at Unit 1,2
ü On June 8, power centers at Unit 1 and 2 failed and the power supply to the main control room lighting, a pump used to transfer water from Unit 2 turbine building and nitrogen injection system was lost for 3 hours due to a signal failure but it was restored about 3 hours later.
ü We confirmed no significant impact to the two units.
[Fukushima Daini](6) Plans to Discharge Accumulated Water in Turbine Buildings
ü We found radioactivity in seawater accumulated in turbine buildings and radioactive waste treatment buildings due to the tsunami.
ü The amount of water is about 3,000 m3 and we detected small amounts of radioactivity such as Co-58/60, Mn-54, Cs-134 and Cs-137 (I-131 has been decayed).
ü To secure plants safety function including recovering safety related equipment and mitigating corrosion in important piping and components, it is necessary to drain this water. At this time, the seawater is stored in the suppression pool surge tank in Fukushima Daini NPS.
ü The amount of radioactive material in this seawater is very small and it is possible to discharge to the sea without conflicting laws and Tech. Spec. But we plan to remove/reduce radioactive material below detectable level, then discharge to the sea.
ü We will consult with relevant organizations prior to discharge.
[Discharge Criteria]
Nuclide | Radioactivity(Bq/cm3) | |
Radioactivity in the Seawater (In Suppression Pool Surge Tank, as of June 1st) | Radioactivity in water, out of the site boundary | |
Mn54 | 3×10-1 | 1×100 |
Co58 | 3×10-1 | 1×100 |
Co60 | 2×100 | 2×10-1 |
I131 | ND | 4×10-2 |
Cs134 | 2×100 | 6×10-2 |
Cs137 | 3×100 | 9×10-2 |
Amount of Radioactive Material (will be discharged), excludes Tritium | Discharge Management Target |
About 3×109Bq | 1.4×1011Bq |
- TEPCO English website
- METI(Ministry of Economy Trade and Industry)
- NISA(Nuclear and Industrial Safety Agency)
- JAIF(Japan Atomic Industrial Forum Inc.)
- FEPC(The Federation of Electric Power Companies of Japan)
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