|Fukushima Daiichi Nuclear Power Station on 21 March 2011, Photo by TEPCO|
Three years have already passed since the 2011 nuclear accident at Fukushima Daiichi Nuclear Power Station (FDNPS).
No improvement has yet been made to the situation in which Fukushima residents are suffering from radiation exposure and 140,000 evacuees are still unable to return home. When will “spring” come for these people? No matter if spring comes to Fukushima and the mountains and plains are covered with green leaves and flowers as far as you can see, the invisible danger of radiation continues to exist deep in the heart of the natural environment. This reminds us of “Silent Spring.”
The whole picture of the nuclear disaster still remains unclear. There are plenty of things that are still unknown, or unaccounted for. Overlooked problems and difficulties are being brought to light one after another. To determine the causes of the nuclear accident, many points need to be clarified; where the problems lie and why they are difficult to deal with. Many of these points still remain unclear, but some of them are becoming apparent.
The number of people diagnosed with cancer of the thyroid gland is increasing as the investigation area is expanded. Due to vagueness in the scientific research, it is still impossible to declare that the growing number of cancer patients has been caused by the nuclear disaster. Nevertheless, it is also wrong to say that the nuclear disaster has nothing to do with the increasing number of cancer patients. We must deal with this problem by assuming that the health effects have been caused by the nuclear accident.
|Fiscal Year||No. of consultations||No. of people referred for secondary test||No. positively diagnosed with thyroid cancer||No. with possible thyroid cancer|
|Table 1. Number of People Diagnosed with Thyroid Cancer, 2011 to 2013
* As of December 21, 2013 (Completed results up to November 15)
Source: Fukushima Prefecture, Survey of Prefectural People’s Health Management
Among people who have not been directly affected by the nuclear disaster and those who wish to imagine that the accident has not inflicted any damage on them personally, we are seeing spreading signs of a desire to forget about Fukushima and a mood for tolerating the restart of nuclear power plants because there does not appear to be any better alternative. However, there is no way to block the popular movement towards the creation of a nuclear-free society. In fact, the situation we have now, where all nuclear reactors are offline, has already been maintained in Japan for as long as six months.
It is well known that some of the crew members of a U.S. aircraft carrier engaged in the “Tomodachi” relief operation in the wake of the 2011 Great East Japan Earthquake were exposed to radiation emanating from the crippled FDNPS. In February, nearly three years after the accident, a total of 79 aircraft carrier crew members filed a class-action law-suit against Tokyo Electric Power Co. (TEPCO), demanding approximately 100 billion yen in compensation.
At the accident site, operations are currently proceeding to cope with several problems.
Transfer of the nuclear fuel from the Unit 4 spent fuel pool to a ground-level pool has been continuing since November 2013 (see NIT 158). TEPCO plans to complete the removal and transfer of all of 1,535 fuel assemblies by the end of 2014.
The transfer of 528 fuel assemblies had been completed as of March 24, 2014. Three damaged fuel assemblies have been stored in the spent fuel pool since the pre-accident period. The task of lifting and removing these fuel assemblies will be a very difficult operation.
|Operations in Unit 4 spent fuel pool, Photo by TEPCO||Storage tanks at Fukushima Daiichi, Photo by TEPCO|
The serious problem of how to deal with contaminated water suddenly emerged in July 2013. This is one of the problems that is making the nuclear accident clean-up very difficult. In early April 2011, it became evident that a great amount of radioactive contaminated water had leaked into the sea from the Unit 2 water intake. The then Democratic Party of Japan government tried to take necessary measures but TEPCO made one excuse after another to ignore the government’s instructions.
Currently, 400 tons of circulating coolant water is daily pumped into the Units 1, 2 and 3 buildings in order to maintain the melted uranium fuel assemblies there in a cool state. Furthermore, another 400 tons of underground water is flowing into the reactor buildings each day, increasing the amount of radioactive contaminated water. The polluted water is currently collected and stored in above-ground tanks, but sooner or later there will be nowhere to place new tanks. Radioactive contaminated water leaks caused by deterioration of the tanks have already occurred at the plant (see NIT 156).
It would be correct to say that the radioactive contamination level of the soil in the nuclear power plant is totally unknown. However, the soil is undeniably severely contaminated. Earlier, in February, the highest-ever level of cesium (134+137) measuring 130,000 Bq/kg was found in a 16m-deep monitoring well located next to the Unit 2 building, near the seashore. There is no guarantee that this record will be left unbroken for long. It will be extremely difficult to block the contaminated water leaks into the sea. As for contamination by beta nuclides, no information has been provided so far.
The water storage tanks contain strontium and other beta-emitting nuclides. It remains uncertain what kind of nuclides and how much of them are contained in the tanks. It was disclosed on January 9 that a non-negligible level of X-rays from the bremsstrahlung radiation*, caused by beta-rays, was detected around the tanks. This means that the workers engaged in the work near the tanks are certain to be exposed to this radiation.
The operation to build frozen walls around Fukushima nuclear power plant to stem leaks of radioactive water from the reactor buildings into the sea began in late January. TEPCO says that the verification test for drilling coolant-filled pipes into the ground will be completed before the end of March. Since this is a huge and challenging operation, there is no guarantee that it will be successful.
At present, the Nuclear Regulation Authority (NRA), without hearing any opinions from the members of the National Diet of Japan Fukushima Nuclear Accident Independent Investigation Commission (NAIIC), is said to be formulating a conclusion that the nuclear accident at Fukushima nuclear power plant was caused by the tsunami.
The only official panel that is still continuing investigations into the cause of the nuclear accident is the Technical Committee of Niigata Prefecture (see NIT 157). A prevailing view among Niigata residents is that the issue of whether Kashiwazaki-Kariwa nuclear power station can be restarted should be discussed after the committee’s investigation is completed. We hope that the view expressed by NAIIC member Mitsuhiko Tanaka, NAIIC cooperative member Yoshinori Ito, and other experts that the nuclear accident was not caused by tsunami, but was in fact caused by the earthquake preceding it, will contribute to the pursuit of truth about the accident.
(By Yukio Yamaguchi, Co-Director of CNIC)
When an electrically-charged particle moving at high speed is obstructed by the electric field from an atomic nucleus and comes to a halt, or when the direction it is moving in is altered, the particle radiates energy in the form of electromagnetic waves. This phenomenon is called bremsstrahlung radiation.