COLD SHUTDOWN OF THE FUKUSHIMA NUCLEAR POWER PLANT
steam isolation valves TEPCO has done extensive rebuilding, including erecting a new steel framework around the building, to provide support and strengthen the structure of the reactor building in preparation for the removal of the fuel assemblies. In November 2013, Jiji Press reported: TEPCO plans to retire the No. 5 and No. 6 reactors at its Fukushima No. 1 nuclear power station.
The Fukushima plant continued to spew radiation after the disaster, though levels dropped with time. Tokyo Electric and Power Co. (TEPCO) installed a new makeshift cooling system that allowed the shut down the plant’s three damaged reactors. Other tasks included removing thousands of tons of highly contaminated water from the reactor buildings.
According to Yomiuri Shimbun, “If all the contaminated water can be removed, then the reactors must be put in what is called cold shutdown to prevent the further discharge of large quantities of radioactive substances and bring the reactors into a stable state. Cold shutdown means all control rods have been inserted into the reactors to stop nuclear fission chain reactions, and the coolant water inside the reactors is below 100 C. Usually the temperature needs to be lowered further to remove fuel rods for regular checks or decommissioning.” "If the original cooling systems can be activated through a power supply from outside the plant and coolant water circulated, cold shutdown can be achieved in a day or two," Prof. Kenichiro Sugiyama of Hokkaido University said.[Source: Yomiuri Shimbun, April 1 2011]
“But it will likely take a few more years for the nuclear fuel rods to be cool enough to be removed from the reactors to decommission them. On the other hand, if the current method--putting coolant water into the reactors with makeshift pumps--continues to be used, the situation may become more serious.” "Although the nuclear fuel would cool gradually, it would take at least several months to achieve cold shutdown," said Toru Ebisawa, a former associate professor of Kyoto University's Research Reactor Institute. This would also mean using more water, which would increase the amount of contaminated water.”
“Overall, it will take decades to complete the process of decommissioning the reactors. The Japan Atomic Power Co.'s Tokai plant in Ibaraki Prefecture was the first commercial nuclear power plant in Japan to begin being decommissioned. The plant ended commercial operations in 1998, and the decommissioning process is scheduled to end in 2021. In the decommissioning process, fuel rods are removed and workers wait for levels of radioactivity to fall. During that time, power generators and other equipment with low levels of radiation contamination are decommissioned first. In the final stage, reactors' steel containers and other equipment are cut into pieces and buried deep underground. At the Tokai plant, heat exchangers and other parts are now being removed.”
“But in the case of the Fukushima No. 1 nuclear power plant, in which reactors and buildings were damaged, it is doubtful whether the normal process of decommissioning will be possible.” Shojiro Matsuura, former chairman of the Nuclear Safety Commission, said, "This time, much more time and effort will be needed to lower radiation contamination levels. Twenty or 30 years probably won't be enough." In the 1979 Three Mile Island accident in the United States, it took a month to achieve cold shutdown and six to seven years to remove melted fuel rods. Fourteen years later, U.S. authorities declared the decommissioning process complete. Part of the nuclear fuel could not be recovered and remained in the reactors. [Ibid]
Cold Shutdown Declared at Fukushima Nuclear Plant in December 2011
In December 2011, the Japanese government declared that the Fukushima Daiichi nuclear plant had reached “cold shutdown.” Chico Harlan wrote in the Washington Post, “But the formal status change at the plant, experts cautioned, means only that its problems have become less dire; they have not disappeared. The plant still leaks radiation into the sea. Its makeshift cooling system is vulnerable to earthquakes. And the cleanup work remains dangerous, with many flooded and debris-strewn areas of the reactor buildings difficult even for robots to access. [Source: Chico Harlan, Washington Post, December 16, 2011]
In normal circumstances, a reactor in cold shutdown mode is entirely stable, its fuel intact, with no chance of a chain reaction. To achieve its version of a cold shutdown at Fukushima Japan had to loosen the definition. Fukushima now meets the government’s requirements because temperatures at the bottom of the three damaged reactor pressure vessels have dropped below 100 degrees Celsius (212 degrees Fahrenheit). Airborne leaks into the environment have also been almost halted, with little chance of backsliding.
“We can now maintain radiation exposure at the periphery of the plant at sufficiently low levels, even in the event of another accident,” Prime Minister Yoshihiko Noda said. “We believe the Fukushima Daiichi accident has been brought under control.” The temperatures at the three damaged reactors now range between 38.1 and 67.8 degrees Celsius (100.6 and 154.0 degrees Fahrenheit), according to TEPCO data.
TEPCO had pledged one month after the disaster to stabilize the plant by January. The effort involved thousands of workers, many from subsidiary companies, who used a soccer training complex as their base camp. They battled a series of unprecedented problems using risky, trial-and-error methods. Engineers needed months to install a reliable cooling system. They shipped in temporary storage facilities for fast-accumulating radioactive water. They installed a cover blanketing the Unit 1 reactor building.
AP reported: The plant's chief acknowledged to journalists visiting the complex that it remains in a fragile state, and makeshift equipment some mended with tape could be seen keeping crucial systems running. Enormous risks and challenges lie ahead at the Fukushima plant, including removal of the melted nuclear fuel from the core and the disposal of spent fuel rods. Completely decommissioning the plant could take 40 years. [Source: AP, March 12, 2012]
Pumping Water into the Reactors and Decontaminating the Water
evaporative concentration equipment > TEPCO continued injecting water into the containment vessel until the fuel rods inside were fully submerged in what the power company has called a "water coffin." In late April TEPCO said it believed pressure suppression pools at the bottom of the No. 1 reactor's containment vessel were full of water, and that the top section of the containment vessel was about half full. Under normal circumstances, the pressure suppression pools are about 50 percent full with water. The pressure suppression pools help control the air pressure inside the reactor's pressure vessel. Operators can open valves to release steam from the vessel into the suppression pools, where it is cooled and condensed to water. [Source: Yomiuri Shimbun, April 25, 2011]
According to TEPCO, it has poured about 7,000 tons of water into the No. 1 reactor's pressure vessel. The company said it believes almost all of that water is still inside the pressure vessel and the containment vessel. However, the firm said it has injected about 14,000 tons of water into the No. 2 reactor and 9,600 tons of water into the No. 3 reactor since cooling operations began. In both cases, the amount injected exceeds the about-7,000-ton capacity of the reactors' containment vessels. TEPCO believes considerable amounts of water leaked from those reactors' containment vessels into their turbine buildings through cracks in pressure suppression pools and other routes. [Ibid]
The decontamination of radioactive water is slated to begin in June. This will involved sending radioactive water through a filter comprised of an oil separator and system that removes radioactive comprised of a deice that absorbs cesium zeolite and a device that removes other radioactive materials through precipitation.
Building Dikes and Underground Walls
In May work began on a 500-meter dike to protect the Fukushima nuclear power plants from aftershocks and additional tsunamis. The makeshift dike was built using stone-filled, basket-shaped containers, measuring one meter to two meters in height, that were stacked to form a barrier 10 meters high between the coast and the Nos. 3 and 4 reactors. TEPCO also plans to reinforce reactor buildings and other facilities damaged by the disaster. Construction to install a concrete structure in the bottom of the No. 4 reactor's pool to temporarily store spent nuclear fuel also started in May. Some geologist say there is a good chance that an 8-magnitude aftershock might occur east of the March 11 earthquake epicenter and such a quake could produce an eight-meter tsunami. The dike---to be made with wire-mesh containers filled with stones---would offer further protection from such an event.
In late July TEPCO said it will begin constructing a new wall that will extend some 60 feet underground to prevent radioactive groundwater from seeping into the nearby Pacific Ocean. Also to be built will be pits to prevent industrial water from flowing back into the sea and reinforcements for reactor No.4 which was seriously damaged by a hydrogen explosion. The later will involve placing 33 eight-meter-long pillars under the spent furl rod pool and surrounding that with a concrete wall 13 meters high and one to six meters thick.
The government is considering building an underground barrier near the Fukushima No. 1 nuclear power plant to prevent radioactive material from spreading far from the plant via soil and groundwater. Sumio Mabuchi, a special adviser to the prime minister, said the plan is the first attempt to address the risk of contaminated water spreading far from the plant through soil. According to Mabuchi, the barrier would extend so far underground that it would reach a layer that does not absorb water. The wall would entirely surround the land on which reactors No. 1, 2, 3 and 4 stand.[Source: Yomiuri Shimbun, April 25, 2011]
Fuel Rods Exposed But Cooling
robo crawler dump “In mid April, the Atomic Energy Society of Japan (AESJ) said that melted nuclear fuel in the Nos. 1 to 3 reactors of the Fukushima No. 1 nuclear power plant was in a cooling state after forming into small particles that have settled at the bottom of pressure vessels. Based on data released by Tokyo Electric Power Co. and the Japanese’s government’s Nuclear and Industrial Safety Agency, the AESJ determined fuel rods in the No. 3 reactor's pressure vessel were completely submerged in water, but the fuel rods in the Nos. 1 and 2 reactor pressure vessels are partially exposed.” [Source: Yomiuri Shimbun, April 16, 2011]
“The AESJ said the fuel rods in the Nos. 1 to 3 reactors were damaged and had partly melted. The committee has presumed that the melted nuclear fuel formed into particles measuring several millimeters or less after coming into contact with cooling water. The particles then settled on fuel rod support plates and at the bottom of the pressure vessels and are in a cooling state, it said. The assumption is consistent with the fact that water temperatures in the lower part of the pressure vessels are low.” [Ibid]
"The contaminated water that leaked into the turbine buildings also is believed to contain particles of melted fuel," Takashi Sawada, deputy chairman of the AESJ, explained. Other experts believe the melted fuel became a magmatic lump with a core temperature in excess of 2,000 C, which later settled on the bottom of the pressure vessels. However, the committee considers there is no danger of intense heat from the melted fuel destroying the pressure vessels. The committee also said it was unlikely that an explosion would occur and cause a large volume of radioactivity to be released from the reactors and nuclear fuel temporary storage pools. [Ibid]
“The committee pointed out that the immediate top priority is to stop radioactive contaminated water from leaking into the turbine buildings. Sawada also stressed the need to take measures against any power outages that may be caused by strong aftershocks. "The nuclear fuel is generating less heat than before, but [the situation] could become dangerous if injecting water into the reactors stops for two or three days and there is a lack of cooling water," Sawada said.
Injecting Water Into the Spent Fuel Rod Pool
desalting machine In late April at the No. 4 reactor, TEPCO has attached cameras and other equipment to a pump used to inject water into the pool containing spent nuclear fuel rods to monitor the water and radiation levels around the clock. According to the company, water in the pool was 91 C and the water level was about 2 meters above the spent fuel rods. Those readings were about the same as those taken by the company on April 12, TEPCO said.
Water was pumped into the spent fuel pond in reactor No. 4 with a pump designed to pump concrete. Although about 70 tons of water is believed to be evaporating every day from the pool the water level is not. rising as much as expected which might mean there is a leak or perhaps water pumped into the spent rod pool is flowing back across the damaged gate into the No. 4 reactor well located next to the pool.
In late April TEPCO began increasing the amount of water injected into reactor No. And no. 4 gradually from six tons per hour to 14 tons an hour in preparation for flooding the reactors primary containment vessel to cool the fuel inside in a stable manner. The injection of water into the reactors cooled the cores quicker than expected without any major leakage.
Months Needed to Stabilize Fukushima Power Plant
radiation storage cask In mid April TEPCO released “road map” on how it was going to solve the crisis at Fukushima nuclear power plant with the goal of bringing the damaged Nos. 1 to 3 reactors to a stable condition known as a "cold shutdown," in which water temperatures inside the reactors are stably brought below 100 C in about six to nine months. At a press conference in Tokyo, TEPCO Chairman Tsunehisa Katsumata said, "It will take three months to ensure that radiation leaking from the nuclear power plant is in a continual decline." He added it would then take another three to six months to significantly reduce these amounts. [Source: Yomiuri Shimbun, April 18, 2011]
Katsumata said the company's tasks include cooling the plant's nuclear reactors and storage pools for spent fuel rods; decreasing the amount of radioactive substances released from the power plant; monitoring radiation leaks and decontaminating radioactive substances at areas near the plant. To reduce the amount of radiation leaking from the power plant---TEPCO's most important goal---Katsumata said it was crucial to prevent hydrogen explosions at reactors Nos. 1, 2 and 3.
"It is also important to prevent water contaminated with radioactive substances from the No. 2 reactor leaking to the sea," he said. TEPCO Vice President Sakae Muto added the company will secure places to keep the contaminated water. However, Muto said TEPCO will not be able to remove fuel rods from the nuclear reactors within the nine-month period. The removal will be conducted in the next phase, he said.
In mid May TEPCO released an updated version of its “road map” toward settling the crisis, saying it would stick to its initial plan to stabilize the crippled reactors sometimes between October and January, although it changed some parts of its plan amid concerns that the Nos. 1 to 3 reactors may all have suffered meltdowns (See Below)
Installing Ventilation Systems and Removing Radioactive Water
In early May 2011 a ventilation system was started at reactor No.1. The goal was to purify the air of radioactivity to make it easier to work there. The system is designed to reduce the concentration of iodine-131 in the reactor building to less than one-30th its current level. If the process goes as planned, work to install a heat exchanger within the building could start as early as May 16, according to TEPCO.
Later the doors to the building that houses Reactor No. 1 were opened to air out the building to ensure that radiation levels are low enough to allow workers to enter. TEPCO said the procedure would release little radiation into the atmosphere because an air filtering system installed last week had already removed most of the dangerous particles. Eight hours after the doors were opened, workers entered the building to test radiation levels. It was the first time people entered it since the tsunami. First two workers entered to check radiation radiation levels. They stayed for 26 minutes then 11 workers entered to install eight ventilation hosed, The radiation level within the reactor building ranged from 8 to 93 millisieverts per hour, according to TEPCO, and the 13 workers were exposed to radiation doses from 0.31 to 3.16 millisieverts. "The dosage level was almost entirely within the 3 millisieverts we planned for. We don't think there are any health risks to the workers," a TEPCO official said.
In late May Kyodo reported that TEPCO started transferring highly radioactive water at the No. 3 reactor to a waste-disposing facility to prevent it from leaking into the environment. The move is believed to be essential to contain radiation leaks from the power station as well as to allow workers to get access to the damaged vessel, from which the contaminated water may be leaking to its adjacent turbine building and other places. Under TEPCO’s plan a total of 4,000 tons of water is expected to be pumped out from the No. 3 reactor turbine building to a nuclear waste disposal facility by using hoses. The tainted water, the level of which has been rising by around 2 centimeters a day in the No. 3 reactor's turbine building, may be leaking into the sea, forcing the plant operator to remove it as soon as possible.
Kyodo reported: “But TEPCO is also being forced to keep injecting sufficient quantities of water into the reactor as workers have been struggling to cool down its vessel stably. The temperature inside the No. 3 reactor has been rising since the beginning of May, topping 200 C on May 7, compared with around 90 C on May 1, TEPCO said....TEPCO remains vigilant as there is some skepticism about whether water has remained in the reactor, company officials said.
Video Taken Inside the Fukushima Reactor in September 2012
In September 2012, the Yomiuri Shimbun reported: “Tokyo Electric Power Co. released video footage taken inside the damaged containment vessel of the No. 1 reactor at its Fukushima No.1 nuclear power plant. The first such footage released by TEPCO since the crisis began in March 2011, the video was made using an endoscope. It shows an area around a pipe that sits about 8.5 meters from the bottom of the containment vessel. The scattered debris that is visible is believed to be damaged parts of the vessel's internal structure. [Source: Yomiuri Shimbun, September 29, 2012]
To insert the endoscope, a hole was drilled through a 30-centimeter-diameter pipe that had become blocked by a steel plate and other debris. The investigation revealed that a 7.5-centimeter-thick lead plate had disappeared from inside the vessel, presumably lost after the hydrogen explosion March 12. Temperatures inside the containment vessel rose to more than 700 C three days after the explosion, meaning the plate probably melted. The melting point of lead is 327 C. [Ibid]
Fukushima Reactor No.1 Gets New Covering
NHK reported in October 2011: Reactor No.1 at the Fukushima Daiichi Nuclear power plant finally has a cover in place that will help lower radioactive emissions. TEPCO had been building the casing for the reactor since June. The cover is 54 meters high, 47 meters wide and 42 meters deep. It has a ventilation system that filters out radioactive substances. [Source: NHK, japan-afterthebigearthquake.blogspot.com October 29, 2011]
TEPCO says that during pilot tests, the system removed more than 90 percent of radioactive cesium from the reactor. The company says the cover will allow it to move nearer to its goal of containing radioactive emissions from the No. 1 reactor. TEPCO is considering installing similar covers for the No. 3 and No. 4 reactors when debris removal is completed after next summer. Both reactor buildings were damaged by the explosions. Radioactive emissions need to be lowered before local residents who were evacuated following the earthquake and tsunami can return home.
In June 2011, the Yomiuri Shimbun reported: “Work to assemble parts of a giant cover for the No. 1 nuclear reactor building at Tokyo Electric Power Co.'s Fukushima No. 1 nuclear power plant is proceeding at a fever pitch at Onahama Port in Iwaki, Fukushima Prefecture. The giant cover is designed to prevent most radioactive substances from dispersing into the atmosphere from the No. 1 reactor, which was damaged by a hydrogen explosion on March 12. It will enclose an area of 42 meters by 47 meters and will stand 54 meters high. [Source: Yomiuri Shimbun, June 21, 2011]
To limit workers' exposure to radiation and shorten the construction period, 62 parts, including pillars, beams and polyester-sheeted panels, are being assembled at the port into a unified structure. After it is confirmed that the parts fit together properly, the cover will be disassembled and transported to the nuclear power plant by ship. On-site assembly of the components is scheduled to start next Monday. TEPCO plans to complete the work in late September.
Final construction of the cover will be carried out by two giant cranes, which will be remote-controlled. A traditional Japanese insertion-only joint method, which does not employ welding or bolts for joining materials, is being used to assemble the cover.
Step 1 at the Fukushima Nuclear Power Plant Completed
By July 2011 what TEPCO and the government called Step 1 of the timetable to end the crisis at the Fukushima No. 1 nuclear power plant was mostly completed, the government said. The focus of Step 1 was setting up a circulation cooling system that was activated on June 27. By decontaminating radioactive water that leaked from damaged reactors and using the clean water to cool the reactors, the quantity of radioactive water, which rose to 120,000 tons at one point, has been declining. The actual decontamination of the water took longer than it was thought it would (See Below).
The Japanese government said that at that juncture that the nuclear crisis has been brought out of a dangerous situation after measures were taken to prevent further hydrogen explosions from occurring at the power plant's nuclear reactors and stable cooling operations were achieved. But the crisis was far from over. Nuclear materials continued to leak into the air and sea from damaged parts of the reactors albeit at levels much lower than immediately after the crisis began.
In July 2012 TEPCO Co. removed a fuel rod from a spent fuel pool at the Fukushima No. 1 nuclear power plant as part of preparations to start the full-scale decommissioning of the crippled plant's reactors. It was the first time fuel had been removed from the plant since it was taken off-line by the March 11, 2011, disaster. The 4.5-meter-long unused rod was lifted from a pool at the No. 4 reactor by a crane on the upper part of the building. The rod was removed to determine how much of the fuel cladding had eroded or been damaged, TEPCO said. [Source: Yomiuri Shimbun, July 19, 2012]
Step 2 at Fukushima Nuclear Power Plant
storage tanks In July 2011, the Japanese government and TEPCO released a road map for ending the ongoing crisis at the Fukushima No 1 nuclear power plant, which aimed to achieve a "cold shutdown" of reactors at the crippled facility by January 2012. Cold shutdown, a major goal of Step 2, will require bringing the temperature of the three reactors to below 100 C. To cool the reactors, which stood at between 100 C and 125 C in July, more water needs to be injected. [Source: Yomiuri Shimbun, July 21, 2011]
The road map for the six months between July and January 2011 began with procedures called Step 2, aiming to reduce this dose to one millisievert a year or lower. In Step 2, circulating injection cooling, which reuses contaminated water to cool the reactors, will continue, and processes aiming to realize stable cooling at controlled temperature will begin. In addition to achieving cold shutdown the government and TEPCO aim to control and substantially lower leakage of radioactive materials from the containment vessels.
The system for treatment of contaminated water was a makeshift one involving four kilometers of pipes that have been plagued by leaks and other problems. Under the road map, the government and TEPCO considered building a full-fledged water-treatment system and constructedi underground walls to prevent contaminants from seeping out via groundwater.
By late September 2011, the temperatures at the base of the No. 1, No. 2 and No. 3 reactors had fallen below 100 degrees C for the first time since the March 11 disaster, meeting one of the two conditions for the reactor to be declared in a stable cooling state known as cold shutdown.
Three-Stage Decommissioning Plan Adopted
In December 2011, after Cold Shutdown was declared, the Japanese government and TEPCO announced they had decided on a 30- to 40-year road map for decommissioning the Nos. 1 to 4 reactors at the Fukushima No. 1 nuclear power plant As the work involves the unprecedented task of removing nuclear fuel that melted through the base of the pressure vessels in the Nos. 1 to 3 reactors, the whole process has been divided into three stages. So-called "assessment points" also have been established, to judge whether work can proceed to the next stage. [Source: Yomiuri Shimbun, December 22, 2011]
The first phase of the new road map---devised by the Natural Resources and Energy Agency, the Nuclear and Industrial Safety Agency and TEPCO---will involve begin of nuclear fuel stored in the spent fuel pool of the No. 4 reactor. Launched in December 2011 and and expected continue until fiscal 2013, the operation will utilize new equipment that can remove the radioactive material that cannot be extracted from contaminated water with the current facilities.
In the second phase, which is scheduled to last from fiscal 2013 to fiscal 2021, all the fuel stored in the spent fuel pools of all the reactors will be removed. Then work will shift to submerging the Nos. 1 to 3 reactors so their melted fuel can be removed. In the meantime, the existing mechanisms that remove radioactive substances from contaminated water and reuse that water to cool the reactors will be made smaller, so they can be housed within the reactor buildings.
In the third stage, which is set to last from fiscal 2021 until fiscal 2051 at the latest, removal of the melted fuel will be completed. Also, the reactors, reactor buildings and other structures will be dismantled and removed, leaving vacant plots of land where the facilities once stood.
Chico Harlan wrote in the Washington Post, “Among other things, workers will have to move spent fuel rods to more stable storage areas and seal cracks that let contaminated water escape into the environment. TEPCO’s biggest challenge might be collecting the molten fuel. Much of that fuel, according to one Tepco simulation, probably burned through the inner chambers designed to hold it and dropped into the containment vessel. At one reactor, the spilled fuel nearly bored its way through the reactor building, stopping 15 inches shy of an outer steel wall. [Source: Chico Harlan, Washington Post, December 16, 2011]
According to an expert panel from the Japan Atomic Energy Commission, it could be 10 years before work can begin to remove the melted fuel. And some experts say that even the 40-year decommissioning timetable set by the government is optimistic. “It is not going to be a regular decommissioning process,” said Tetsunari Iida, a former nuclear engineer who directs the Institute for Sustainable Energy Policies. “It’s going to take hundreds of years.”
Japan must also decontaminate an area around the plant of some 930 square miles, according to the Environment Ministry. That process could clear the way for some evacuees to return home, if they are willing to take the risk. Many areas within the no-entry zone---a 12-mile radius around the plant---will be uninhabitable for decades, maybe longer.
Fuel Retrieval at Fukushima to Start in 10 Years
In October 2011, Japan's Atomic Energy Commission says it aims to start retrieving melted nuclear fuel rods from the Fukushima Daiichi power plant within 10 years. The report says decommissioning will start with repairing the containment vessels of the No.1 to No.3 reactors, where meltdowns occurred. The vessels will then be filled with water to block radiation released from the melted fuel. The commission also plans to start moving spent fuel rods from pools at the No.1 to No.4 reactors to another pool in the plant within 3 years. This will take place after the reactors achieve a state of cold shutdown. [Source: japan-afterthebigearthquake.blogspot.com October 28, 2011]
The report projects that the decommissioning will take more than 30 years to complete. The timetable is longer than that for the Three Mile Island nuclear plant in the United States, because the containment vessels were damaged at Fukushima along with the pressure vessels that house fuel rods. In the 1979 Three Mile Island accident, about 70 percent of the reactor's fuel rods melted. Fuel retrieval began 6 years after the accident and lasted for 5 years. The work at Fukushima is expected to be longer and more difficult, because the extent of the damage is more severe and workers will have to repair 4 reactors simultaneously.
The decommissioning cost in the U.S. accident is reported to be about $1.5 billion. In the case of the Fukushima No. 1 plant, a third-party committee estimated the cost will be about $13 billion, using the U.S. accident as a reference. But the cost may increase further, experts say.
New Seawalls at Japan’s Nuclear Power Plants
In response to the accident at the Fukushima nuclear power plant, the government instructed the nation's power companies on March 30 to take urgent safety measures to prevent damage from tsunami. The utilities are preparing their anti-tsunami measures, including the construction of seawalls. A total of 45 of the 54 reactors around the country are planning to build seawalls. Construction is expected to be completed as early as spring 2012, or in the next 3 years at the latest. [Source: japan-afterthebigearthquake.blogspot.com October 5, 2011]
In October 2011, Hokuriku Electric Power Company started construction of a reinforced concrete seawall at the plant in Shika Town, Ishikawa Prefecture. The wall is 4 meters high, 700 meters long, and sits 11 meters above the sea level. Hokuriku Electric also plans to install a new drainage gate to minimize damage to plant facilities in case seawater manages to climb over the wall and flood the plant. Other emergency safety measures to be taken by the utility include installing an extra pump to cool reactors with seawater and a power source to operate a valve for venting steam out of reactors. The company intends to complete construction by the end of March 2013.
Removal of Fukushima Nuclear Fuel Begins in November 2013
In November 2013, Alexander Martin wrote in the Wall Street Journal, “More than 2½ years after the Fukushima nuclear disaster, TEPCO began the painstaking and potentially dangerous process of removing fuel rods from one of the plant's damaged reactor units.The operation, expected to take more than a year to complete, is TEPCO's first step toward dismantling the devastated plant in what is expected to be a 30- to 40-year cleanup process after one of the worst nuclear accidents in history. [Source: Alexander Martin, Wall Street Journal, November 18, 2013 +++]
“For the next 13 months, TEPCO plans to transfer 1,533 assemblies holding spent and fresh fuel from a storage pool at the top of the reactor No. 4 unit and move it to a common pool serving all six of the plant's reactors. The operation involves the careful removal of 550-pound assembly units each holding 60 to 72 metal-clad rods filled with fuel pellets that power a nuclear reactor. The units are kept in a pool of cool water to prevent any exposure to air that might cause the radioactive material to heat up or even trigger a sustained nuclear reaction. +++
“TEPCO said it began lifting the first fuel-assembly unit using a crane to place them inside the 5.5-meter-long container, while they are still submerged in water in the storage pool. It said four assembly units were transferred by the time work for the first day wrapped up. The container can store up to 22 fuel assemblies and weighs around 91 metric tons when filled. +++
“TEPCO spokesman Yoshikazu Nagai said 36 workers in groups of six will each take two-hour shifts for the encasement process alone. Once sealed, the container will be lifted out of the pool and taken down to ground level, where it will be placed on a trailer for transportation to the common fuel pool around 100 meters away. There, the assemblies will be removed from the container, after it is submerged again in water. "It takes around two days to fill up one container, and around one week for it to be sealed, transferred and safely placed in the common pool," he said. Two containers will be used in turns, he said. +++
Nobuyuki Hamanaka and Takashi Maemura wrote in the Yomiuri Shimbun, “One team on the task consists of six people, including two who operate a crane above the pools and two who handle underwater cameras. They must wear protective gear and masks. As the delicate work makes it difficult for the workers to communicate with each other and move precisely, some observers are concerned about operational errors. Air radiation levels around the pool are 0.04 millisievert per hour. Workers at the plant are estimated to be exposed to 100 millisieverts of radiation over five years. As they work under highly stressful conditions, the six teams removing the fuel take turns every two hours. The fuel removal is also planned for the Nos. 1 to 3 reactors with higher radiation levels. To prevent experienced workers having to leave after their exposure to radiation exceeds the set limits, TEPCO has been urged to proceed with the work carefully and effectively. [Source: Nobuyuki Hamanaka and Takashi Maemura, Yomiuri Shimbun, November 20, 2013 |=|]
“Others have voiced concerns over the possibility the containers used to move the fuel could somehow fall and break, or small debris remaining in the pool could jam the assemblies and complicate the process.Another TEPCO spokesman, Noriyuki Imaizumi, said Monday during a regular news conference that any debris found remaining in the spent fuel pool during the removal process will be cleared out during nighttime. Keiji Miyazaki, an expert on nuclear reactor engineering and professor emeritus at Osaka University, said he expected a smooth removal process, provided the plant isn't hit by another large earthquake during the operation. "I'm sure TEPCO has already considered such a scenario, but my concern is what could happen if a larger-than-expected earthquake strikes the plant when the crane is hauling the heavy container out of the spent fuel pool," he said. TEPCO has said it has taken precautionary measures to protect the fuel, with a locking device preventing any fall of the container in the event a quake causes a power failure while the assemblies are being moved. +++
Removal of Fukushima Nuclear Fuel Major Step in Decommissioning Process
Nobuyuki Hamanaka and Takashi Maemura wrote in the Yomiuri Shimbun, “TEPCO’s road map divided the decommissioning work, which started in December 2011, into three stages. The start of fuel removal means that the first stage, regarded as a preparation period for decommissioning the reactors, has come to an end, paving the way for the second stage. TEPCO plans to move fuel assemblies in storage pools at the Nos. 1 to 4 reactors to safer common pools and stop water leakage from the Nos. 1 to 3 reactors in the second stage. This is expected to reduce further risk of massive leaks of radioactive substances from the plant. Despite frequent leaks of contaminated water at the plant, preparations for fuel removal from the No. 4 reactor went smoothly, allowing the first stage, which was supposed to take two years, to be completed a month ahead of schedule. [Source: Nobuyuki Hamanaka and Takashi Maemura, Yomiuri Shimbun, November 20, 2013 |=|]
“TEPCO had sorted out possible risks during the fuel removal operation, such as fuel assemblies falling when they are lifted by a crane and a failure in the cooling system for the storage pools. To prepare for the possibility an earthquake could occur while the assemblies are lifted, the crane has been equipped with extra devices such as double wire ropes and a stopper attached to a hook to prevent the fuel assemblies from falling. |=|
“The utility also conducted procedural tests and operational training using dummy fuel assemblies while undergoing government inspections and asking overseas experts to check its envisaged work. Lake Barrett, a former official of the U.S. Nuclear Regulatory Commission who led the decommissioning of the Three Mile Island nuclear plant after the 1979 nuclear accident, expressed confidence that TEPCO would carry out the work successfully because it was prepared carefully. He also said it was vital that the utility explain the decommissioning process clearly to residents affected by the nuclear crisis. |=|
TEPCO Wins Rare Praise, But Hurdles Remain
In December 2013, Osamu Tsukimori of Reuters wrote: TEPCO “won rare praise from monitors for its efforts to decommission the site, but the specialists also said the company still faced steep challenges, particularly in managing contaminated water. But it has proceeded with initial decommissioning steps, including the tricky removal of spent fuel rod assemblies from a badly damaged reactor building. The entire process is likely to take decades and costs ten of billions of dollars."It's nice to see the good progress TEPCO has made in the last several months," Dale Klein, a former chairman of the U.S. Nuclear Regulatory Commission, told a meeting of the Nuclear Reform Monitoring Committee. "There's obviously a lot more work to be done, but it's very positive progress....Spent fuel movement at (reactor) No. 4 went very well. You have demonstrated a very positive approach to safety culture." But Klein added: "You've also made good progress in water management. But again water will continue to be a challenge at the Fukushima site."[Source: Osamu Tsukimori, Reuters, December 2, 2013 \+\]
“The Monitoring Committee, which includes four members from outside TEPCO, was set up in September 2012 in response to calls for independent experts to monitor pledges to raise standards of safety culture. Barbara Judge, a British-based nuclear expert, also pointed to "extremely good progress" by the company. "But nuclear safety is a long proposition. And it's only beginning," she said. "I'm disappointed that it's not going as fast as we would have liked it to. There is still reluctance by some of the members to ask the hard questions." Judge praised improvements in working conditions for those overseeing the clean up and decommissioning process, saying the efforts would make "working at Fukushima easier for them and better for the company and better for the country". \+\
“But TEPCO's difficulties have focused on radioactive water leaks and in July it first acknowledged, after months of denial, that the water had spilled into the Pacific. Its management of water leaks has improved since the government said in September it was stepping into oversee the process. The International Atomic Energy Agency, the U.N. watchdog for nuclear power, is currently undertaking an inspection of the Fukushima site after issuing rare criticism of TEPCO during a visit earlier in the year. \+\
IAEA: Japan Nuke Cleanup May Take More than 40 Years
Mari Yamaguchi of Associated Press, “A U.N. nuclear watchdog team said Japan may need longer than the projected 40 years to decommission its tsunami-crippled nuclear plant and urged its operator to improve plant stability. The head of the International Atomic Energy Agency team, Juan Carlos Lentijo, said that damage at the Fukushima Dai-ichi plant is so complex that it is "impossible" to predict how long the cleanup may last. "As for the duration of the decommissioning project, this is something that you can define in your plans. But in my view, it will be nearly impossible to ensure the time for decommissioning such a complex facility in less than 30-40 years as it is currently established in the roadmap," Lentijo said. [Source: Mari Yamaguchi, Associated Press, April 22, 2013 /~/]
“The government and plant operator Tokyo Electric Power Co. have predicted the cleanup would take up to 40 years. They still have to develop technology and equipment that can operate under fatally high radiation levels to locate and remove melted fuel. The reactors must be kept cool and the plant must stay safe and stable, and those efforts to ensure safety could slow the process down. "You have to adopt a very cautious position to ensure that you always are working on the safe side," Lentijo said. /~/
The plant still runs on makeshift equipment and frequently suffers glitches. Just over the past few weeks, the plant suffered nearly a dozen problems ranging from extensive power outages and leaks of highly radioactive water from underground water pools. One day, TEPCO had to stop the cooling system for one of the fuel storage pools for safety checks after finding two dead rats inside a transformer box. Earlier in the month, a rat short-circuited a switchboard, causing an extensive outage and cooling loss for up to 30 hours. Lentijo said water management is "probably the most challenging" task for the plant at the moment. TEPCO says 280,000 tons of contaminated water has been stored in tanks on the plant, and the amount would double within a few years. /~/
Lentijo, an expert on nuclear fuel cycles and waste technology, warned of more problems to come. "It is expectable in such a complex site, additional incidence will occur as it happened in the nuclear plants under normal operations," Lentijo said. "It is important to have a very good capability to identify as promptly as possible failures and to establish compensatory measures." The IAEA team urged the plant operator to "improve the reliability of essential systems to assess the structural integrity of site facilities, and to enhance protection against external hazards" and promptly replace temporary equipment with a more reliable, permanent system.
Image Sources: Tepco and YouTube
Text Sources: New York Times, Washington Post, Los Angeles Times, Times of London, Yomiuri Shimbun, Daily Yomiuri, Japan Times, Mainichi Shimbun, The Guardian, National Geographic, The New Yorker, Time, Newsweek, Reuters, AP, Lonely Planet Guides, Compton’s Encyclopedia and various books and other publications.
© 2008 Jeffrey Hays
Last updated January 2014