Monthly Report of the Watchers’ Team, (Summary, Sept. 2012)
(A. Summary of TEPCO Home Page article/B. Comment by Watchers’ Team)
1. Reactor Cooling
A. (TEPCO):
The water supply decreased by 0.1-0.2 cubic meters at each reactor, but temperatures in the primary containment vessels have decreased by 2.7-6.9 degrees Celsius.
B. (Watchers’ Team):
A possible trouble attributable to the above decreased water supply is not anticipated for the time being, because the hottest season was over.
2. Radioactive Density of Cesium in Cooling Water
A. (TEPCO):
The density of Cs137 sampled in the triangular compartment located in the northwest corner of the Unit 1 building is decreasing gradually.
05/27/2011; 2,900 kBq/cm3
11/25/2011; 190 kBq/cm3
09/20/2012; 70 kBq/cm3
B. (Watchers’ Team):
It is estimated that the condition of the fuel debris is stable and the generation of fresh fracture surface in contact with the water is small.
3. Accumulated Water Storage
A. (TEPCO):
A total amount of accumulated water is 204 kilotons as of Sept. 18, and a total capacity of available tanks is 229 kilotons at present. Additional tanks are under construction to increase the capacity by 86 kilotons, and more tanks are planned to add a further volume by 80 kilotons. The total capacity of the tanks, including those being planned, is estimated in 700 kilotons.
B. (Watchers’ Team):
A volume of 54 kilotons water out of the above mentioned 86 kilotons will be stored in underground water tanks (they are sealed by bentonite and double layers of polyethylene sheet). No report of substantial investigation regarding their integrity has been presented.
4. Advanced Liquid Processing System (ALPS)
A. (TEPCO):
A verification for the removal ability of 62 radioactive nuclides other than cesium was completed. The density reduction for all nuclides below the detection limit was attained.
B. (Watchers’ Team):
The ALPS was cold tested until Aug. 4. A schedule for the full-scale operation is to be adjusted with the Nuclear Regulatory Agency. A stable operation in the early stages is expected.
5. Aerial Radiation Dosage at Site Boundaries
A. (TEPCO):
The current radiation dosage is 9.67 mSv/year. The dosage is planned to be reduced to 0.47 mSv/year by means of shielding the facilities and relocating the radioactive waste farther from the boundaries.
B. (Watchers’ Team):
It needs to be considered that the dosage is not measured at the boundaries, but is the value of additional dosage from inside.
6. Spent Fuel Pool
A. (TEPCO):
1) The inspection of two unused fuel assemblies removed from the spent fuel pool in Unit 4 testified the soundness.
(2) A steel beam slipped and fell into the spent fuel pool in Unit 3. No deviation of dose rate or water level was detected.
B. (Watchers’ Team):
(1) No corrosion on the removed fuel assemblies is a piece of good information. A possibility of deformation in other fuel assemblies remains unknown.
(2) The accident was caused by a fundamental error while the beam was lifted. Safety measures are necessary.