Smoke After Reactor Explosion
After the gigantic earthquake and tsunami struck the Fukushima Daiichi nuclear power plant on March 11, 2011, reactors No. 1, 2 and 3 at the plant suffered core meltdowns Reactor No. 4 avoided a meltdown but a hydrogen explosion blew open the roof and walls of the reactor building. The fragile state of the No. 4 reactor and its spent fuel pool—containing highly radioactive fuel rods, located 130 feet above ground level---- led some experts to warn that a severe aftershock could damage the tank and leave the fuel rods dangerously exposed, releasing huge amounts of radiation.

The New York Times reported: "As Japan struggled with a rescue effort after the earthquake and tsunami it also faced a nuclear emergency with explosions and leaks of radioactive from three reactors at the Fukushima Daiichi Nuclear No.1 Power Station while spent fuel rods at another reactor overheated and caught fire, releasing radioactive material directly into the atmosphere. While no one died in the nuclear accident, the environmental and human costs are huge. [Source: New York Times]

Shortly after the 9.0 magnitude earthquake and tsunami struck the northern coast of Japan at 2:56pm on March 11, reports emerged of damage at one of Japan’s nuclear power plants. The plant lost its backup power shortly after 3:30 p.m., when it was hit by massive tsunami. Between March 12 and 15, explosions occurred one after another at the Nos. 1, 3 and 4 reactor buildings at the Fukushima No. 1 nuclear power plant operated by Tokyo Electric Power Co. (TEPCO). Cooling functions were lost at the reactor buildings due to the failure of all power sources as a result of the earthquake and tsunami. Massive amounts of radioactive substances were dispersed into the atmosphere outside the plant. [Ibid]

The reactors lost their cooling systems due to the blackout and a hydrogen explosion occurred in the No. 1 reactor in the afternoon of March 12, destroying most of the reactor building.That day Japanese authorities began evacuating residents nearby the Fukushima nuclear power plant due to the release of radioactive elements into the environment, signs of a possible meltdown at one of the reactors. Two days later the government said cooling systems at a third reactor had failed. The Kyodo news agency reported that the damaged fuel rods at the third reactor had been temporarily exposed, increasing the risk of overheating. Sea water was being channeled into the reactor to cover the rods. [Ibid]

David Jolly and Ken Belson wrote in the New York Times, “At the Fukushima Daiichi Nuclear Power Station, Japanese officials have struggled to contain a dire nuclear crisis in the quake's aftermath, facing partial meltdowns at two crippled reactors, fires at a third and cracks at yet another unit with a power outage that prevents the interior radioactive rods from being cooled. The emergency appeared to be the worst involving a nuclear plant since the Chernobyl disaster 25 years ago. The developments at two separate nuclear plants prompted the evacuation of more than 200,000 people. “The disasters require nationwide mobilization for search, rescue and resettlement,” Jolly and Belson wrote “and a scramble for jury-rigged solutions in uncharted nuclear territory, with crises at multiple reactors posing a daunting array of problems. Japan’s leaders need to draw on skills they are woefully untrained for: improvisation; clear, timely and reassuring public communication; and cooperation with multiple powerful bureaucracies.” [Source: David Jolly and Ken Belson wrote in the New York Times, March 18, 2011

Evan Osnos wrote in The New Yorker, “A row of six aging nuclear reactors at the Fukushima Daiichi nuclear power plant had lost their cooling systems, as well as their “backup backup--- protections, in the words of one nuclear expert. The prospect of radiation introduced a threat all its own, as invisible as the tsunami was vivid, and throbbing with history. Initially, the Japanese government downplayed the possibility that the ailing plants could leak any significant radiation, but survivors of the atomic bombings of Hiroshima and Nagasaki---the revered generation known as hibakusha’stepped forward to plead for “more sense of crisis.” [Source: Evan Osnos, The New Yorker, March 28, 2011]


Gravity of the Crisis at Fukushima Nuclear Power Station

On April 12, the Nuclear and Industrial Safety Agency of the Economy, Trade and Industry Ministry proclaimed the crisis to be "Level 7" in terms of severity, equal to the 1986 Chernobyl disaster in the former Soviet Union. The provisional evaluation of the accident was based on the International Nuclear Event Scale. Level 7 is the highest level, classified as a "major accident." Subsequent analyses found that core meltdowns took place at the Nos. 1 to 3 reactors.

On March 16, Emperor Akihito took the unprecedented step of addressing his people on television, telling them in a recorded message broadcast nationwide that he was “deeply worried” about the ongoing nuclear crisis and asking them to act with compassion “to overcome these difficult times.” Akihito reportedly had never before delivered a nationally televised address of any kind, not even in the aftermath of the Kobe earthquake in 1995 that killed more than 6,000 people.”

In a speech in June 2011 in Barcelona, the writer Haruki Murakami said: “This is a historic experience for us Japanese: our second massive nuclear disaster. But this time no one dropped a bomb on us. We set the stage, we committed the crime with our own hands, we are destroying our own lands, and we are destroying our own lives.” He challenged his countrymen to acknowledge “the failure of our morals and our ethical standards.” He said, “While we are the victims, we are also the perpetrators. We must fix our eyes on this fact. If we fail to do so, we will inevitably repeat the same mistake again, somewhere else.” [Source: Evan Osnos, The New Yorker, October 17, 2011]

Fukushima Daiichi Nuclear Power Station

Fukushima Plant in 1975
Fukushima No.1 (Daiichi) Nuclear Power Station is 170 miles north of Tokyo. Designed by General Electric, with a design similar to that of the Oyster plant in near Toms River, New Jersey, it went into operation in 1971 and was supposed to have been retired after 30 years of operation but, only a month before the disaster, had been approved by the Japanese government to keep operating for another ten years despite warnings about its safety. The plant’s life span was approved despite safety warnings and flaws such as radiation damage to pressure vessels that hold the fuel rods; corrosion on spray heads used to douse the suppression chamber; corrosion on key bolts in the reactors; and problems with gauges that monitor water flow into the reactor.

The Fukushima No. 1 nuclear power plant is owned and operated by Tokyo Electric and Power Company (TEPCO), which supplies a third of Japan’s power. People who lived around the plant had been grateful that it provided jobs and subsidized kindergartens, parks and community centers. Reactors No. 1 and 2 were made by GE. Reactor No.3 was made by Toshiba. Reactor No.4 was made by Hitachi.

Evan Osnos wrote in The New Yorker: Fukushima, which means “fortunate island,” erected its first plant---the one struck by the tsunami---on the former site of a Second World War imperial air base. Then it built another, not far down the rocky coast. Locals referred to their new skyline as the Nuclear Ginza, after the posh neighborhood in Tokyo. In a town beside the Fukushima Daiichi plant, people erected a sign that declares “Nuclear Power Is the Energy of a Bright Tomorrow.” The plant, about a hundred and fifty miles north of Tokyo, is painted white and pale blue and is a labyrinth of boxy buildings and piping on a campus larger than the Pentagon’s. It has six reactors. [Source: Evan Osnos, The New Yorker, October 17, 2011]

One of the main faults with the outdated reactors at Fukushima nuclear power plant is that they have small suppression chambers, which increases the risk of a pressure build up in the reactor (newer reactors have larger suppression chambers). One of the main reasons the life span of Japan’s aging nuclear power plants is being extended is that is strong opposition to new plants and very high costs involved with building new plants and shutting down old ones.

The Fukushima No.1 Nuclear Power Station has six nuclear reactors. There is also Fukushima Nuclear No. 2 Power Station nearby four reactors,. At the time of the disaster reactors No. 1, No. 2 and No. 3 of the Fukushima No.1 plant were operating. Reactors No. 4, No. 5 and No. 6 were not operating due to periodic inspection. Like most nuclear power plants the reactors---that contained the nuclear fuel rods that generated heat that produced steam that turn turbines to make electricity---has three layers of protection: the containment building; the containment vessel, and the metal cladding around fuel rods, which are inside the reactor.

The reactor pressure vessel that covers the reactor core is designed to prevent radiation from being released should something go wrong with the nuclear fuel. Even if the reactor vessel were damaged, radiation leaks are supposed to be prevented by another container surrounding it. Around these is the reactor's outer building.

Deaths (Lack of Deaths) Related to Radiation from the Fukushima Disaster

Six workers died in operations to the contain the crisis at Fukushima nuclear power plant. In May 2012, a United Nations panel reported that none of the deaths were caused by radiation exposure. The deaths were attributed to cardiovascuar disease and other causes. One worker died of leukemia but there was no correlation between his death and radiation exposure according to the United Nations Scientific Committee on the Effects of Atomic Radiation.

“Mark Lynas wrote in the Los Angeles Times: “The “current radiation-related death toll is zero and will likely remain so...Aa member of the public would have to eat seaweed and seafood harvested just one mile from the discharge pipe for a year to receive an effective dose of 0.6 millisieverts. To put this in context, every American receives on average 3 millisieverts each year from natural background radiation, and a hundred times more than this in some naturally radioactive areas. As for the Tokyo tap water that was declared unsafe for babies, the highest measured levels of radioactivity were 210 becquerels per liter, less than a quarter of the European legal limit of 1,000 becquerels per liter. Those leaving Tokyo because of this threat will have received more radiation on the airplane flight out than if they had been more rational and stayed put. [Source: Mark Lynas, Los Angeles Times, April 10, 2011]

In Reactor No. 1 at the Fukushima Nuclear Power Plant the Time of the Earthquake

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Reactor Area Before Tsunami
Reporting the experiences of a TEPCO subcontractor at the time of the earthquake. Naoko Kagemoto wrote in the Yomiuri Shimbun, “Strong horizontal jolts dislodged ceiling pipes and massive amounts of water started flooding out--this was the frightening scene experienced by a worker who was in the building housing the No. 1 reactor of the Fukushima No. 1 nuclear power... When the earthquake struck, he was doing electrical work with some coworkers inside the containment building of the reactor, which was operating at the time, in an area where there was ordinarily no fear of radioactive contamination and thus no need for protective clothing.” [Source: Naoko Kagemoto, Yomiuri Shimbun, March 17, 2011]

"It was such a powerful jolt I could hardly stand. I was thrown from side to side," he said. "I thought, 'That was no ordinary jolt.'" He also heard loud crashes of a crane, lighting and other equipment being bounced around, he said. Soon the lights inside the building went out and emergency lighting came on. An announcement came next, telling workers to stay where they were. But seams on metal pipes installed in the ceiling had been broken by the strong jolts and water started flooding out. [Ibid]

“Someone yelled: “This could be dangerous water. Let's get out of here!” and they rushed down the stairs to the first floor exit. Workers are supposed to first report, without touching, water leaks they find inside the building. But continuing aftershocks made them more terrified of being trapped inside the building with the reactor than of the possibly radioactive water, he said. When they reached the first floor, it was crowded with other employees changing out of their work uniforms and being tested for radioactive exposure before they left the building, as called for by regulations. But with only one testing device available, there was a long line of workers waiting in the narrow passage. The aftershocks kept on coming and some people shouted angrily, "Hurry up!" He eventually found out he had not been exposed to radiation.

Tsunami Was up to 21 Meters in Fukushima

The Yomiuri Shimbun, “The tsunami that hit Fukushima Prefecture on March 11 was particularly high---possibly up to 21 meters---along the coast in the center of the prefecture where the Fukushima No. 1 nuclear power plant is located, a survey has found. The height of the tsunami was previously assumed to have been about 15 meters at the nuclear plant, but this could not be confirmed because the area within a 20-kilometer radius of the plant is designated a no-entry zone. [Source: Yomiuri Shimbun February 9, 2012]

Researchers including Shinji Sato, a professor at the University of Tokyo, obtained permission from local governments to enter this zone, and for the first time since the tsunami, were able to survey coastal areas Monday and Tuesday. They found that areas struck by higher tsunami were concentrated on the coast in the prefecture's center. For example, at Tomioka, which is eight kilometers south of the nuclear plant, a tsunami height of 21.1 meters was observed. The maximum height was 10 meters along much of the coast in the prefecture's south. "It is necessary to do more research on what caused the tsunami to hit the central part of the prefecture particularly hard," Sato said.

Affect of the Tsunami on Fukushima Nuclear Plant

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Reactor Area After Tsunami
Tsunami waves estimated to be over 12 meters high overwhelmed the Fukushima plant on March 11. The plants protections against natural disasters---offshore breakwaters, designed to guard against typhoons but not tsunamis---were woefully inadequate and succumbed quickly as a first line of defense. The wave grew three times as tall as the bluff on which the plant had been built. [Source: New York Times, March 14, 2011]

The tsunami waves easily overcame the sea walls surrounding the Fukushima plant. It swamped the diesel generators, which were placed in a low-lying area, apparently because of misplaced confidence that the sea walls would protect them. At 3:41 p.m. Friday, roughly an hour after the quake and just around the time the region would have been struck by the giant waves, the plant lost all power and the back up diesel generators shut down. According to TEPCO the plant switched to an emergency cooling system that operates on batteries, but these were soon depleted. [Ibid]

TEPCO later said that the tsunami rose to a height of 15 meters above sea level and flooded buildings at the Fukushima nuclear power plant, including the reactors and turbine buildings, were with water up to depths of four to five meters. The height determination was based on physical evidence such as evidence of water damage and the discoloration of walls. Several tsunami waves struck the facility. The first arrived at 3:27pm---41 minutes after the earthquake. One wave that was 5.7 meters above sea level passed over the breakwater and wiped out the seawater pumps near the water intake outlets. Later waves as high as 10 meters struck the turbine buildings completely submerging the facilities doors . The force of the waves sent seawater around the turbine buildings to the far side of the reactor buildings. [Source: Yomiuri Shimbun, April 11, 2011]

At the time reactors No. 1, No. 2 and No. 3 were operating. Reactors No. 4, No. 5 and No. 6 were not operating due to periodic inspection. Without power, operators couldn’t circulate cooling waters through the plant that keep the radioactive fuel rods and pellets---which produce the power at the plant---from overheating. Temperatures and pressures inside the vessels of No. 1, No. 2 and No. 3 reactors began rising sharply, making it more difficult to inject cooling water into the reactors. The heat of the nuclear fuel began rising to dangerous levels. The fuel rods began to boil off the remaining water and became exposed and go even hotter---possibly producing a partial melt down. Workers responded by trying to pump in seawater into the reactors as an emergency measure to cool the fuel.

Situation Reaches the Crisis Level at the Fukushima Nuclear Power Plant

The Yomiuri Shimbun reported: “The Japanese government, Japan’s nuclear safety agency and TEPCO were filled with relief immediately after the earthquake. They had been told backup diesel generators would provide sufficient support to stabilize the Nos. 1 to 3 reactors, which were in operation when the quake hit. However, subsequent tsunami destroyed 12 of the 13 emergency generators. "Round up all the power-supply cars and send them to the plant right now!" shouted a TEPCO supervisor at the utility's head office in Tokyo. The emergency cooling systems that channel water into the reactor rely on emergency batteries to power the water intake valves. The emergency batteries at the Fukushima plant were expected to run out of power around midnight.” [Source: Yomiuri Shimbun , April 12, 2011]

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Reactors Buildings After Explosions

“TEPCO dispatched power-supply vehicles from various power stations around the country to the crippled nuclear plant. However, the vehicles had to travel very slowly because of damage to roads in northeastern Japan. The first power-supply car did not reach the plant until 9 p.m. on March 11. Once at the site, the lack of preparation became apparent. Cables needed to connect the vehicles' high-voltage electricity to plant facilities were not long enough. TEPCO immediately ordered additional cables, but precious time had been wasted. Power would not be restored at the plant by midnight.” [Ibid]

“At around 10 p.m. on March 11, the day of the disaster, Japanese Prime Minister Naoto Kan was given a report from the Nuclear and Industry Safety Agency of the Economy, Trade and Industry Ministry predicted reactor cores at the nuclear power plant--where power and all functions to cool the reactors were lost in the quake and tsunami--would be exposed to air, and that extreme heat generated by fuel rods would damage their encasing tubes later that night causing a meltdown.” [Ibid]

“Kan and everyone at the Prime Minister's Office understood the seriousness of the situation described by the report. There were only two options that might prevent a meltdown of the reactors--either restore the plant's power supply and cooling functions immediately, or pour water directly into the reactors. If neither course of action could be taken, the pressure inside the reactors would become so great that they would be destroyed.” [Ibid]

“The report concluded that valves in the containment vessels would have to be opened, to release radioactive steam and reduce the pressure inside. However, opening the valves was considered a last resort. Although it could prevent the reactors from breaking apart, it would release steam with high levels of radioactive materials into the atmosphere. But when pressure inside the containment vessels rose above the maximum allowed for by the facilities' design, there was no other option but to open the valves.” [Ibid]

Dithering by TEPCO as the Situation at the Fukushima Plant Worsens

“TEPCO began preparations for opening the valves around 7 p.m. on March 11. Pressure inside the No. 1 reactor was particularly high. “Soon, the reactor won't be able to withstand the pressure,” said an official of the accident headquarters at the plant, which was keeping in touch with TEPCO's head office via video phone. “We have to vent the pressure immediately.” “Pressure inside the containment vessel of the No. 1 reactor has gone up dramatically,” the agency told Banri Kaieda, economy, trade and industry minister, at 12:45 a.m. on March 12. In fact, it had reached 1.5 times the designed maximum, meaning the condition of the reactor was critical. “To get things under control, we have to pour water into the reactors and then vent the steam that is generated,” Haruki Madarame, chairman of the Cabinet Office's Nuclear Safety Commission, told Kaieda.” [Source: Yomiuri Shimbun , April 12, 2011]

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Four Damaged Reactor Containment Buildings

“At 1:30 a.m. on March 12, Kan, Kaieda and Madarame gathered at the crisis management center in the basement of the Prime Minister's Office. The three urged TEPCO officials to vent the steam as soon as possible. But TEPCO officials said there was no way of opening the valves because there was no power supply. Exasperated, Kaieda called the utility's head office in Tokyo and the accident headquarters at the plant every hour, pressuring them to open the valves immediately.” [Ibid]

“TEPCO workers tried to open the valves by manually overriding the automatic system, but struggled to make progress because they had to work in darkness. At dawn, pressure inside the No. 1 reactor was more than twice the designed maximum. Eventually, at 6:50 a.m., the government ordered the utility to open the valves under the Nuclear Reactor Regulation Law.”

“When Kan visited the accident site shortly after 7 a.m. and found TEPCO had not opened the valves yet, he reprimanded company officials. The officials replied they would like to have another hour to make a decision on what to do. Kan blew his stack. “Now's not the time to make such lackadaisical comments!” the prime minister told the TEPCO officials. Yet even still, the utility spent three more hours discussing the matter before finally opening the valves at 10:17 a.m. Five hours after that, a hydrogen explosion occurred at the No. 1 reactor, blowing apart its outer building.”

First Explosion at Reactor No. 1 at Fukushima Nuclear Plant

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Reactor No. 1
The New York Times reported: “Inside the plant...according to industry executives and American experts... there was deep concern that spent nuclear fuel that was kept in a ''cooling pond'' inside one of the plants had been exposed and begun letting off potentially deadly gamma radiation. Then water levels inside the reactor cores began to fall. While estimates vary, several officials and industry experts said that the top four to nine feet of the nuclear fuel in the core and control rods appear to have been exposed to the air--- a condition that can quickly lead to melting, and ultimately to full meltdown.” [Source: New York Times, March 14, 2011]

At 8:00 p.m., the government declared an emergency, contradicting its earlier reassurances that there were no major problems. By that time workers inside the reactors saw that levels of coolant water were dropping. They did not know how severely because gauges that measured the water level didn’t give accurate readings. By that point workers new that cooling systems at Fukushima Daini were starting to fail, for many of the same reasons, and pressure in the No. 1 reactor at Fukushima Daiichi was rising so fast that engineers knew they would have to relieve it by letting steam escape. But steam was not released until the following day because an evacuation of the area had not occurred and Japanese Prime Minister Naoto Kan flew over the area while making an inspection of earthquake and tsunami damage.

On March 12, the day after the quake, steam was released at 10.17am from the No.1 reactor. Shortly after 3:30 pm., camera crews near the plant captured an explosion at the No. 1 reactor caused by a buildup of hydrogen in the outer container and its exposure to oxygen in the air. Oxygen explodes when it combines with hydrogen. About 10 minutes after the explosion white smoke began rising from the facility.

The explosion blew off the roof and the walls of the outer container and made for dramatic television but was not especially dangerous--- except to the workers injured by the force of the blast---because it occurred in the outer container, leaving the main reactor vessel unharmed. The walls of the outer building blew apart, as they are designed to do, rather than allow a buildup of pressure that could damage the reactor vessel. But the dramatic blast was also a warning sign of what could happen inside the reactor vessel if the core was not cooled. At 8:00pm workers began injecting seawater in the No. 1 reactor to cool it down.

The Japanese nuclear safety agency said that the level of cooling water in the No. 1 reactor likely dropped to 1.7 meters below the top of the nuclear fuel rods, meaning about half the rod’s length had been exposed. Why did hydrogen fill the external containment structure before the blast? Professor Emeritus Keiji Miyazaki at Osaka University, an expert in atomic energy engineering, told the Yomiuri Shimbun nuclear fuel is enveloped in a particular type of metal covering. When the fuel reaches an extremely high temperature and then comes into contact with the cooling water, the metal's properties break down the water and generates hydrogen. The hydrogen can leak from the reactor containment vessel into the outer structure through valves and other gaps.

Fukushima residents were angry with TEPCO and the Japanese government for their failure to prudently disclose information about the nuclear crisis. Naoki Nanno, 30, who lives 25 miles from the plant and spent two years as a construction worker on the plant's reactors, told the Los Angeles Times, "I heard a loud bang and I suspected it was an explosion at the nuclear plant, but they didn't announce it for another 20 minutes are so. There was radioactive material leaking after that explosion---we should have known about it right away.”

Miyazaki said TEPCO should have acted more promptly. "It was an extremely serious accident. I have the impression that [TEPCO] spent too much time backing up the emergency electricity source, which had gone down," the professor said. "I think they could have prevented the accident if they'd started putting water [into the reactor] with temporary fire pumps to lower temperatures inside the reactor earlier. They finally started doing that Saturday morning."

Second Explosion Blows Roof off of Reactor No. 3 at Fukushima Nuclear Plant

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Reactor No. 3
On Sunday, two days after the quake, a second reactor unit---the No. 3 reactor unit--- at the stricken at the Fukushima plant ruptured and released radioactive steam. The International Atomic Energy Agency (IAEA) explained in an update on its website that Japanese officials have carried out “a controlled release of vapor,” from the No. 3 reactor, “intended to lower pressure inside the reactor containment.”

The IAEA statement read: “Japanese authorities have informed the IAEA’s Incident and Emergency Center (IEC) that venting of the containment of reactor Unit 3 of the Fukushima Daiichi nuclear power plant started at 9:20AM local Japan time of 13 March through a controlled release of vapor. The operation is intended to lower pressure inside the reactor containment... Subsequently, following the failure of the high pressure injection system and other attempts of cooling the plant, injection of water first and sea water afterwards started. The authorities have informed the IAEA that accumulation of hydrogen is possible.”

On March 14, three days after the quake, an explosion blew the roof off the No. 3 reactor, not damaging the core, officials said, but presumably leaking more radiation. TEPCO said two explosions could be heard, Video showed huge plumes of smoke and fire coming from the building. Eleven workers---four TEPCO employees, three from TEPCO subcontractors and three Self Force personnel---were reported injured.

The supply of cooling water in reactor No. 3 ran out due to a loss of fuel for temporary pumps. Between 1:00am and 3:20 am the use of seawater to cool the reactor was suspended. Some suspect this exposed the fuel rods, bring them into contact with steam and this generated a large amount of hydrogen that triggered the explosions. In addition to white smoke associated with hydrogen explosions there was also gray-brown smoke, which some experts believed might be linked with another problem in the reactor, possibly a partial meltdown in the reactor.

At this point it became clear the situation at the Fukushima nuclear power plant had reached a crisis level that could go on for weeks or even months. The emergency flooding of two stricken reactors with seawater---which caused the release of radioactive steam---began. This was a desperate step intended to avoid a much bigger problem: a full meltdown of the nuclear cores in two reactors.

Third Explosion at Reactor No. 2 at Fukushima Nuclear Plant?

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Reactor No. 2
Also on March 14, water levels fell at reactor No. 2, leaving fuel rods completely exposed. No explosion occurred so the outer containment building remained intact and things looked okay from the outside. But inside was perhaps the most vulnerable of three troubled reactors to a serious meltdown.

On March 15, it was first thought, an explosion at reactor No. 2 ruptured the torus (also called the primary suppression pool) and breached the primary containment vessel. High radiation levels found at the lower part of the primary containment structure, led the U.S. Nuclear Regulatory Commission (NRC) to speculate that fuel probably leaked from the pressure vessel of the No. 2 reactor. Although this implied the damage was worse than previously though the NRC said, it “does not believe that the reactor vessel has given way, and...believes practically all of the core remains in the vessel.”

The Yomiuri Shimbun reported: “The explosion at the No. 2 reactor is believed to have damaged the suppression pool. The blast was heard at 6:14 a.m. at the No. 2 reactor, whose cooling functions had already been deteriorating. Pressure inside its suppression pool dropped from the normal level of three atmospheres to one atmosphere, according to TEPCO.

TEPCO said there is a possibility the suppression pool may have been partially damaged and radioactive material may have leaked outside. At 7:50 a.m., 1-1/2 hours after the explosion, radiation of 1,941 microsieverts per hour was observed at the main gate of the No. 1 plant. Forty minutes later, the level shot up to 8,217 microsieverts per hour, which is more than eight times the exposure limit considered to be healthy for one year.

According to TEPCO, the pressure suppression pool is designed to release and lower steam pressure if it rises in the reactor containment vessel. The pressure inside the containment vessel remained unchanged at 7.3 atmospheres, according to TEPCO. According to the Economy, Trade and Industry Ministry's Nuclear and Industrial Safety Agency, the suppression pool contains steam and water with radioactive material.

No Explosion at No. 2 Reactor

An interim report released in October 2011 by a TEPCO panel investigating the nuclear crisis at Fukushima concluded that a hydrogen explosion did not occur at the plant's No. 2 reactor, overturning its previous conclusion that an explosion took place on March 15. According to TEPCO, the first hydrogen explosion took place in the No. 1 reactor building on the afternoon of March 12, followed by an explosion at the No. 3 reactor on the morning of March 14. Early on the morning of March 15, TEPCO confirmed the sound of an explosion, and then found damage in the No. 4 reactor building. [Source: Yomiuri Shimbun. October 3, 2011]

The power company also confirmed that pressure in the No. 2 reactor's pressure suppression pool, which is the lower portion of the reactor's containment vessel, dropped significantly immediately after the sound was heard. So the company concluded that explosions must have occurred almost simultaneously at the Nos. 2 and 4 reactors, and the government reported the same conclusion to the International Atomic Energy Agency in June.

However, the panel studied a seismometer at the plant and found only one explosion tremor recorded at 6:12 a.m. that day. Based on analysis of the tremor, the panel concluded that the explosion occurred at the No. 4 reactor. However, due to the fact that the pressure at the No. 2 reactor's pressure suppression pool dropped around that time, the panel said the reactor's containment vessel may have sustained other damage. The interim report did not further explain the damage or its cause. Indeed, the core of the No. 2 reactor is believed to have sustained the most serious damage among the power plant's six reactors, and the pace of cooling at the No. 2 reactor has been slow.

According to the draft of the interim report, a blowout panel installed at the upper part of the No. 2 reactor building opened accidentally after the No. 1 reactor's hydrogen explosion on March 12. The draft says a hydrogen explosion was avoided at the No. 2 reactor because a certain amount of hydrogen escaped through the blowout panel.

Explosion and Fire in Reactor No.4 Where Spent Fuel Rods are Stored

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Reactor No. 4
On March 15, the situation at the stricken Fukushima Daiichi plant appeared to verge towards catastrophe. Radiation levels shot up at the plant after a new explosion and a fire caused by the overheating of spent fuel rods in a pool at the plant's No. 4 reactor, which had been shut before the quake. The Yomiuri Shimbun reported: “High levels of radiation were detected at the Fukushima No. 1 nuclear power plant Tuesday morning after a fire broke out near a pool in the No. 4 reactor where spent nuclear fuel is temporarily kept.

TEPCO said radiation measuring 400 millisieverts (400,000 microsieverts) per hour was detected at 10:22 a.m. following the fire, which broke out at 9:38 a.m. "There is no doubt [these radiation levels] may pose health risks to humans," Chief Cabinet Secretary Yukio Edano said. . Four-hundred millisieverts per hour can increase incidence of cancer among those exposed. The figure also is 400 times legal radiation limits citizens are normally allowed to be exposed to, except for medical purposes.” [Source: Yomiuri Shimbun, March 16, 2011]

“TEPCO said the No. 4 reactor was out of operation for regular checks when the magnitude-9 earthquake hit the Tohoku region...However, the earthquake knocked out electricity to the reactor needed to circulate cooling water in the pool that temporarily stores spent nuclear fuel. As a result, residual heat from nuclear fuel rods raised the water temperature in the pool from the ordinary level of about 40 C to 85 C, TEPCO said. "Lower water level in the pool exposed tubes [encasing the fuel rods], which reacted with steam, likely generating hydrogen and causing an explosion," said Tetsuji Imanaka, assistant professor at Kyoto University Research Reactor Institute. A total of 783 spent nuclear fuel rods were stored in the pool.

By late afternoon on March 15, there were signs that workers had, at least for the moment, contained some of the danger: The escalated radiation levels of earlier in the day ---possibly from a fire in the No. 4 reactor---stabilized and then declined towards evening, according to Japanese authorities. But some experts warned that the pools holding spent fuel rods could continue to pose a great danger. The next day on March 16, smoke began rising from reactor no.3 prompting concerns that maybe water had leaked from the pool holding spent fuel rods and a fire and dangerous release of radiation could be occurring there.

One of the most dangerous jobs during the crisis was spraying water onto reactors trying to get water inside pools in reactor No. 3 holding the spent fuel rods. Much of that task was done by firefighters and SDF soldiers. A fire fighter from Tokyo who participated in the operation told the Yomiuri Shimbun, “We had to fight against the invisible threat [of radiation] during this mission, We had a difficult time accomplishing it in a short time [to minimize our exposure to radiation]. It was our team work that enabled us to complete the mission [in a short time].

Why the Explosions Occurred and Defending TEPCO’s Response

The interim report also referred to a possible reason why hydrogen explosions occurred at the Nos. 1 and 3 reactors. The report said silicon rubber used to seal the spaces between doors and wall, and between the containment vessels and their lids, may have not functioned properly due to the high temperatures, opening gaps that allowed the release of hydrogen into the reactor building.

The panel defended the company's slow initial response to the nuclear disaster, such as preparations to vent steam from reactor, by saying, "It can't be helped that that [the initial response] took time, as workers had to prepare in the darkness."The interim report said the nuclear reactor's major equipment sustained no damage due to the earthquake itself, but instruments ensuring the safety of the nuclear reactors lost their functions simultaneously due to tsunami, worsening the situation exponentially.

Prospect of a Huge Catastrophe at Fukushima

Evan Osnos wrote in The New Yorker: Chairman Jaczko was invited to testify on Capitol Hill the next day, and told lawmakers that the N.R.C. believed the pool had run dry. It was a striking claim, because it intensified the prospect of a far larger catastrophe---by one estimate, a worker standing beside a single dry pool could receive a fatal dose in sixteen seconds. It also raised questions about virtually identical pools at nuclear plants across the United States. (In June, the N.R.C. reversed itself and said that the Fukushima pools never ran completely dry, though it stands by the belief that the pools posed a grave threat.) [Source: Evan Osnos, The New Yorker, October 17, 2011]

Experts at the Departments of State and Defense were trying to anticipate what would happen next; the possibilities were extraordinarily dangerous, including one that became known as “the popcorn scenario.” If there was another explosion, the spike in radiation could prevent workers from being able to continue injecting water onto the fuel cores. Then “one will pop and then another one and then another one and then another,” a senior U.S. official told me. Fuel that had already melted into a heap at the bottom of the reactor could melt through the steel pressure vessel and react with the concrete below, releasing vapors carrying highly radioactive materials such as strontium and technetium. In that case, “the environmental impact from that many reactors is hundreds of kilometres,” Charles Casto, the top N.R.C. official on the ground in Japan, said. “That was the scenario we were working, and there were a lot of people who believed in that scenario.” He himself had been skeptical that it would come to that.

“Hundreds of kilometres” meant that the impact could reach the outskirts of Tokyo, the world’s largest metropolitan area, with a population of thirty-five million. The Japanese government publicly maintained that the risk was manageable, but U.S. authorities were far less sanguine. Kevin Maher, one of the senior State Department officials on the interagency task force responding to the crisis, told me that by March 15th representatives from the State Department, the Defense Department, and other agencies were actively debating how to evacuate all American citizens from Tokyo---as many as a hundred thousand people. It would be an extreme maneuver. Maher, who retired from the State Department in April, recalled the debate: “Would you have to advise people to try to evacuate, running the risk that they could get stuck in the middle of the road with nowhere to shelter? Or would you advise people to shelter in place, meaning cover your windows or try to go into a basement?” Though they gave no public indications that the discussion was under way---it could have started a panic---they talked about the use of trains and commercial aircraft. Tokyo already had a gasoline shortage, and an evacuation on that scale would also have harmed relations with the government. No matter how they looked at it, Maher said, the prospect was “a nightmare.”

Videos of the Fukushima Nuclear Power Plant Crisis

Video of Tsunami Hitting Fukushima Nuclear Power Plant

Tsunami Hits Fukushima Power Plant

Fukushima Plant After Tsunami

Video of Explosions at Fukushima Nuclear Power Plant

Fukushima Explosion

Explosion at Reactor No. 1

Fukushima Explosions at Reactor 3 and 4

Video of Damage to Fukushima Nuclear Power Plant After Explosions

Helicopter Video of Smoking Fukushima Plant

Smoke 10 Days After Tsunami

Video of Brave Workers at Fukushima Nuclear Power Plant After Explosions

Video, Slides of Fukushima Plant and Workers

Fukushima Fifty

Hospitalized Fukushima Workers

Brave Fukushima Workers

Video of Fears About Radiation from Fukushima Nuclear Power Plant

Fears Over Japanese Food

Worried About Radiation in Tokyo

Image Sources: TEPCO except black and white damage photos by DigiGlobe

Text Sources: New York Times, Yomiuri Shimbun, Daily Yomiuri, Washington Post, Los Angeles Times, Kyodo News, National Geographic, The Guardian. Times of London, The New Yorker, Time, Newsweek, Reuters, AP, AFP, and various books and other publications.

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© 2008 Jeffrey Hays

Last updated January 2014

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