8 Mars 2012
March 8, 2012
TOKYO (Kyodo) -- A year after the Fukushima Daiichi nuclear power plant was ravaged by a huge earthquake and tsunami, Japan continues to face the challenge of keeping the complex under control without much knowledge of what is actually happening inside the three crippled reactors.
The country is also gearing up to clean the vast radiation----contaminated areas outside the plant, located about 220 kilometers northeast of Tokyo, but securing places to store the topsoil after removal is not easy given the opposition of local residents.
The nuclear crisis at the plant in Fukushima Prefecture occurred shortly after the March 11 natural disasters led to the loss of nearly all of the plant's power sources, and consequently the ability to cool the reactors and spent fuel pools.
The Nos. 1 to 3 reactors have suffered core meltdowns and the buildings housing the Nos. 1, 3 and 4 reactors were ripped by explosions caused presumably by hydrogen released from the core.
Following a painstaking process to contain the world's worst nuclear crisis since the 1986 Chernobyl disaster, the government announced in December that the plant has achieved a stable state of cold shutdown.
But the fact that no one knows precisely what has happened inside the reactors and where the melted nuclear fuel is located means there is still great uncertainty over the situation at the complex.
Most recently, tensions grew over the status of the No. 2 reactor after readings on one of its thermometers showed a notable rise in February in a possible sign that there may be some trouble in cooling the fuel.
While plant operator Tokyo Electric Power Co. determined that the thermometer in question was broken, the incident highlighted the need for the utility to enhance the credibility of its system for monitoring the reactors.
"We should take this problem in the measuring equipment seriously," nuclear disaster minister Goshi Hosono told a press conference on Feb. 14. "Given that work toward scrapping the reactors is expected to last for 30 to 40 years, it is extremely unfavorable to see a situation in which the utility cannot obtain data."
According to a road map for decommissioning the reactors, the utility known as TEPCO will start removing the fuel stored in the spent fuel pools of the Nos. 1 to 4 units within two years and the fuel from the Nos. 1 to 3 reactors within 10 years.
Tadashi Narabayashi, a Hokkaido University professor, called on the utility to swiftly create "criteria and a monitoring system to judge whether a cold shutdown condition has been maintained," using the readings of properly functioning thermometers and the amount of radioactive substances released from the reactor buildings.
He also pointed to the need to develop robots within five years that can operate inside the reactors, where radiation levels could be high enough to destroy integrated circuits in a short time, so that they can carry out such work as installing new thermometers for the reactors.
In addition to the situation of melted fuel, due attention is needed in handling the massive amounts of contaminated water created as a result of constant water injection into the stricken reactors.
After being used to cool the reactors, the water goes through a processing facility so that radioactive substances are removed to a certain extent. Some of the water is then recycled as a coolant and the remaining portion is placed in tanks at the site.
But the storage capacity could eventually run short, raising the possibility that TEPCO may resort to dumping low----level radioactive water in the Pacific Ocean, a plan the utility said it was considering in December but gave up due to opposition from the fishing industry.
Outside the plant's premises, work to reduce the contamination level of land detected to have an annual exposure dose of 1 millisievert or more, excluding natural dosage, is set to accelerate in eight prefectures in the northeastern and eastern regions of Japan.
Talks are also under way between the central government and municipalities located near the stricken plant to build a facility in Fukushima Prefecture to store the removed soil for a certain period of time.
The government aims to select the location for the interim storage facility during fiscal 2012, but the eight municipalities concerned have not yet reached a consensus on the issue and it remains to be seen whether things will go as scheduled.
Reflecting the sensitivity of the matter, a gathering between the government and the municipalities planned for Feb. 26 was abruptly canceled, with the mayor of one of the two towns that host the Fukushima plant expressing his "strong mistrust" of the state due to media reports that described in advance what the government planned to discuss at the meeting.
Swift establishment of the facility is necessary to move the decontamination process forward and help people in Fukushima Prefecture restore their shattered lives.
The following is the current status and other information on the six reactors at the Fukushima Daiichi nuclear power plant, crippled by the magnitude 9.0 earthquake and ensuing tsunami on March 11 last year, based on data issued by the government and plant operator Tokyo Electric Power Co.
-------- Reactor No. 1 (Operation suspended after quake)
Core melted after loss of power supply, 392 fuel assemblies stored in spent fuel pool, building housing the reactor damaged by hydrogen explosion on March 12, building cover completed on Oct. 28, achieved state of cold shutdown on Dec. 16.
-------- Reactor No. 2 (Operation suspended after quake)
Core melted after loss of power supply, 615 fuel assemblies stored in spent fuel pool, achieved state of cold shutdown on Dec. 16, industrial endoscope passed into reactor on Jan. 19, malfunction of thermometers confirmed in February.
-------- Reactor No. 3 (Operation suspended after quake)
Core melted after loss of power supply, 566 fuel assemblies stored in spent fuel pool, building housing the reactor damaged by hydrogen explosion on March 14, achieved state of cold shutdown on Dec. 16, work to remove debris from upper area of building continuing.
-------- Reactor No. 4 (Under maintenance when quake struck)
No fuel rods in core, 1,535 fuel assemblies stored in spent fuel pool and stably cooled, building housing the reactor damaged by hydrogen explosion on March 15, supporting structure under bottom of pool installed as countermeasure against aftershocks by July 30, work to remove debris from upper area of the building continuing.
-------- Reactors No. 5, 6 (Under maintenance when quake struck)
Achieved cold shutdown on March 20, with power supplied by one emergency diesel generator.
Fukushima gov. inspects Daiichi nuclear plant
The governor of Fukushima Prefecture has asked the operator of the Fukushima Daiichi nuclear plant to continue efforts to decommission its crippled reactors.
Yuhei Sato on Thursday visited the plant run by Tokyo Electric Power Company for the first time since the accident there last March.
Sato was told by plant chief Takeshi Takahashi that there's still a long way to go, but that the government and the firm said in December that the plant had been brought to a state of cold shutdown. The state marks the second phase of a timetable to bring the plant under control.
Takahashi added that the firm wants to steadily carry out operations such as removing fuel rods that melted and fell to the bottoms of the plant's reactors.
Sato said residents of the prefecture remain uneasy due to reports on a series of problems at the plant.
The governor later visited the plant's emergency response room and thanked about 150 workers for their efforts. He then boarded a bus to tour 4 reactor buildings and other facilities.
Sato said the visit made him think again about the severity of the accident. He added that the prefectural government will have to work to realize an early return of nuclear evacuees and reconstruction of infrastructure.