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.

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.

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.

“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.

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.”

“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.”

“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.”

“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.”

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.”

“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.

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].

Meltdowns at the Fukushima Nuclear Power Plants

In May 2011 Tokyo Electric Power Co. (TEPCO) admitted that core meltdowns occurred at the Nos. 1, 2 and 3 reactors at the Fukushima No. 1 nuclear power plant. The melted fuel is now believed to be kept cool at the bottom of each reactor pressure vessel because of the emergency water injection measure. In a report was submitted to the Nuclear and Industrial Safety Agency of the Economy, Trade and Industry Ministry, said he meltdowns at the Nos. 1 to 3 reactors occurred in relatively short periods of time--about a half day to about four days--after the March 2011 earthquake and tsunami. As much as 800 kilograms of hydrogen was generated as a result of the overheating of nuclear fuel at the No. 1 reactor, according to TEPCO. The amount was enough to destroy the reactor building, according to nuclear experts. [Source: Yomiuri Shimbun, May 25, 2011]

The report was submitted two months after the disaster. Many people wondered why it took so long. The primary reason for the delay was that the reactors were without power, as their switchboards were submerged in water when the powerful tsunami struck. Most of the data TEPCO used to grasp what had happened in the reactors is normally recorded on computers at the reactors' central control rooms. Extremely high radiation levels near the control rooms in the early days of the crisis delayed the utility's ability to retrieve data that had been recorded.

It was not until early May when radiation levels declined and rubble was cleared from the area, that TEPCO workers were able to enter the control room to collect the data. Besides electronic data, paper records were also left inside the control rooms, which TEPCO scanned to add to the electronic records. To fill in the gaps when there was neither electronic nor paper records, the utility interviewed officials who were at the plant at the time, and looked at job sheets and other notes left on whiteboards in the control rooms. TEPCO then performed computer simulations of the meltdowns using an accident analysis program, based on various data including those already announced, such as water and pressure levels in reactors and operation records.

Prospect of a Huge Catastrophe at Fukushima

Speaking about the damaged reactors at the Fukushima Daiichi nuclear plant, Guenther Oettinger, the European Union’s energy commissioner, said: “There is talk of an apocalypse and I think the word is particularly well chosen...The site is effectively out of control...In the coming hours, further catastrophic events can be expected with danger for the life and limbs of the people on the island.” Eric Besson, France’s minister of industry and energy, made similar remarks on Wednesday , telling BFM television: “Let’s not beat about the bush: they have visibly lost the essential of control. That is our analysis, in any case, it’s not what they are saying.” Yukiya Amano, the former Japanese diplomat who heads the IAEA said that the situation at the plant is “very serious,” but “it is not the time to say things are out of control.”

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.”

Was the Fukushima Disaster as Bad as Chernobyl?

In mid April 2011, the Nuclear and Industrial Safety Agency (NISA) raised the severity level of the crisis at the Fukushima No. 1 nuclear power plant to a seven with seven being the worst rating on its scale, equivalent to that of the 1986 Chernobyl crisis. The agency had previously rated the accident as a five. The agency — a Japanese government organization’said the amount of radioactive material, calculated based on the reactors' estimated condition, reached "more than several tens of thousands of terabecquerels." A terabecquerel equals 1 trillion becquerels. [Source: Yomiuri Shimbun, April 13, 2011]

The level is defined as a "major accident" under the International Nuclear and Radiological Event Scale (INES), or the highest level on its scale from zero to seven, based radiation releases and the effect or radiation on workers at the nuclear facility and people living around it. According to the agency, the total amount of iodine-131 and cesium-137 emitted between March 11 and April 12 reached 370,000 terabecquerels according to the reactors' estimated condition. Within this assessment, cesium levels were converted to their equivalent in iodine-131 levels. Another Japanese government agency — the Cabinet Office's Nuclear Safety Commission — calculated the total amount of iodine and cesium emitted between March 11 and April 5 was 630,000 terabecquerels (again, with cesium levels converted to the iodine equivalent).

Some felt that giving the Fukushima crisis the same ranking as Chernobyl was not right. The total amount of radioactive materials emitted thus far by the Fukushima plant is equal to about 10 percent of that released in the Chernobyl accident and no one has been killed the Fukushima crisis. In the Chernobyl crisis, about 5.2 million terabecquerels of radioactive material was emitted into the air in the space of 10 days and about 30 workers and firefighters there die of radiation exposure. The NISA — the group in charge of making the ranking for the International Atomic Energy Agency (IAEA) — decided to raise the INES level not only because of the calculated radiative material released into the atmosphere but also because of the widespread ramifications of the accident.

Rachel Nolan wrote in the New York Times: “We know that the nuclear situation in Japan is critical. But how bad is it? Japan’s nuclear safety agency raised the rating of the crisis at Fukushima from 4 to 5 on the 7-step international scale. On one hand, this is scary: another Level 5 nuclear crisis was at Three Mile Island in 1979. (Chernobyl was a 7.) On the other hand, as a scientist friend pointed out to me this morning, the new rating means that the situation in Fukushima is 1/100 as bad as the Chernobyl accident. [Source: Rachel Nolan, New York Times]

“An explanation: The 7-step international scale was created by the International Atomic Energy Agency (I.A.E.A.) to measure the intensity of nuclear disasters,” Nolan wrote. “It is a logarithmic scale; an increase of one level means it is 10 times as intense, as the agency explains on a fact sheet. The Richter scale is also a logarithmic scale. But because it is much easier to systematically measure the shaking caused by an earthquake than to gauge a nuclear crisis, the I.A.E.A.’s scale is necessarily more interpretive. For example, no one died during the Three Mile Island meltdown, so saying that it was even 1 percent as bad as Chernobyl seems like an overestimation. And given Japan’s history, the psychological effects of Fukushima will most likely be much greater than those of Three Mile Island, so rating them both the same may also be misleading. But despite its flaws, the I.A.E.A. scale is the only international measure we’ve got.”

"Fukushima and Chernobyl are very different," said Denis Flory, head of nuclear safety and security at the IAEA. "This is a totally different accident. The level of releases and the value for Chernobyl are significantly different. IAEA officials, including the agency's chief Yukiya Amano, have repeatedly pointed out that Chernobyl — the world's worst-ever nuclear accident — was caused by human error and a design fault, whereas the crisis at Fukushima was triggered by an earthquake and ensuing tsunami of unprecedented size. In addition, the reactors at Fukushima had been automatically shutdown when the earthquake hit, while at Chernobyl the reactor had been operating. [Source: AFP, April 14, 2011]

"The mechanics of the accident are very different," Flory said. The Chernobyl reactor did not have a reactor vessel, while Fukushima does and that reactor vessel is still contained even after a series of explosions. That meant that the power of the Chernobyl explosion sent huge amounts of radiation into the high atmosphere "spreading it all over the world". By contrast, the Fukushima reactors were all shut down during the earthquake and there was no explosion in the reactor vessel itself.

The British government's Chief Scientific Officer Professor John Beddington said that even in “the worst case scenario,” the crisis in Japan would not rival the one that engulfed the area around Chernobyl in 1986. According to a transcript of his remarks at the British Embassy in Tokyo he said, “If the Japanese fail to keep the reactors cool and fail to keep the pressure in the containment vessels at an appropriate level, you can get this, you know, the dramatic word “meltdown.” But what does that actually mean? What a meltdown involves is the basic reactor core melts, and as it melts, nuclear material will fall through to the floor of the container. There it will react with concrete and other materials — that is likely.”

“Remember this is the reasonable worst case,” Beddington said, “we don’t think anything worse is going to happen. In this reasonable worst case you get an explosion. You get some radioactive material going up to about 500 meters up into the air. Now, that’s really serious, but it’s serious again for the local area. It’s not serious for elsewhere, even if you get a combination of that explosion it would only have nuclear material going in to the air up to about 500 meters. If you then couple that with the worst possible weather situation, i.e. prevailing weather taking radioactive material in the direction of Greater Tokyo and you had maybe rainfall which would bring the radioactive material down, do we have a problem? The answer is unequivocally no. Absolutely no issue.”

“The problems are within 30 km of the reactor. And to give you a flavor for that, when Chernobyl had a massive fire at the graphite core, material was going up not just 500 meters but to 30,000 feet; it was lasting not for the odd hour or so but lasted months, and that was putting nuclear radioactive material up into the upper atmosphere for a very long period of time. But even in the case of Chernobyl, the exclusion zone that they had was about 30 kilometers. And in that exclusion zone, outside that, there is no evidence whatsoever to indicate people had problems from the radiation.”

The problems with Chernobyl were people were continuing to drink the water, continuing to eat vegetables and so on and that was where the problems came from. That’s not going to be the case here. So what I would really reemphasize is that this is very problematic for the area and the immediate vicinity and one has to have concerns for the people working there. Beyond that 20 or 30 kilometers, it’s really not an issue for health.

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.

Last updated August 2020

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