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updated 7/12/2011 1:52:35 PM ET 2011-07-12T17:52:35

The warnings were stark and issued repeatedly as far back as 1972: If the cooling systems ever failed at a Mark 1 nuclear reactor, the primary containment vessel surrounding the reactor would probably burst as the fuel rods inside overheated. Dangerous radiation would spew into the environment.

Now, with one Mark 1 containment vessel damaged at the embattled Fukushima Daiichi nuclear plant and other vessels there under severe strain, the weaknesses of the design — developed in the 1960s by General Electric — could be contributing to the unfolding catastrophe.

When the ability to cool a reactor is compromised, the containment vessel is the last line of defense. Typically made of steel and concrete, it is designed to prevent — for a time — melting fuel rods from spewing radiation into the environment if cooling efforts completely fail.

In some reactors, known as pressurized water reactors, the system is sealed inside a thick, steel-and-cement tomb. Most nuclear reactors around the world are of this type.

But the type of containment vessel and pressure suppression system used in the failing reactors at Japan’s Fukushima Daiichi plant — and in 23 American reactors at 16 plants — is physically less robust, and it has long been thought to be more susceptible to failure in an emergency than competing designs.

G.E. began making the Mark 1 boiling water reactors in the 1960s, marketing them as cheaper and easier to build — in part because they used a comparatively smaller and less expensive containment structure.

American regulators began identifying weaknesses very early on.

In 1972, Stephen H. Hanauer, then a safety official with the Atomic Energy Commission, recommended in a memo that the sort of “pressure-suppression” system used in G.E.’s Mark 1 plants presented unacceptable safety risks and that it should be discontinued. Among his concerns were that the smaller containment design was more susceptible to explosion and rupture from a buildup in hydrogen — a situation that may have unfolded at the Fukushima Daiichi plant.

“What are the safety advantages of pressure suppression, apart from the cost saving?” Mr. Hanauer asked in the 1972 memo. (The regulatory functions of the Atomic Energy Commission were later transferred to the Nuclear Regulatory Commission.)

A written response came later that same year from Joseph Hendrie, who would later become chairman of the N.R.C. He called the idea of a ban on such systems “attractive” because alternative containment systems have the “notable advantage of brute simplicity in dealing with a primary blowdown.”

But he added that the technology had been so widely accepted by the industry and regulatory officials that “reversal of this hallowed policy, particularly at this time, could well be the end of nuclear power.”

In an e-mail on Tuesday, David Lochbaum, director of the Nuclear Safety Program at the Union for Concerned Scientists, said those words seemed ironic now, given the potential global ripples on the nuclear industry from the Japanese accident.

“Not banning them might be the end of nuclear power,” said Mr. Lochbaum, a nuclear engineer who spent 17 years working in nuclear facilities, including three that used the G.E. design.

Questions about the G.E. reactor design escalated in the mid-1980s, when Harold Denton, an official with the N.R.C., asserted that Mark 1 reactors had a 90 percent probability of bursting should the fuel rods overheat and melt in an accident. A follow-up report from a study group convened by the commission concluded that “Mark 1 failure within the first few hours following core melt would appear rather likely.”

Video: New fire erupts at Fukushima plant (on this page)

In an extreme accident, that analysis held, the containment could fail in as little as 40 minutes.

Industry officials disputed that assessment, saying the chance of failure was only about 10 percent.

Michael Tetuan, a spokesman for G.E.’s water and power division, staunchly defended the technology this week, calling it “the industry’s workhorse with a proven track record of safety and reliability for more than 40 years.”

Mr. Tetuan said there are currently 32 Mark 1 boiling water reactors operating safely around the globe. “There has never been a breach of a Mark 1 containment system,” he said.

Several utilities and plant operators also threatened to sue G.E. in the late 1980s after the disclosure of internal company documents dating back to 1975 that suggested the containment vessel designs were either insufficiently tested or had flaws that could compromise safety.

Paul Gunter, director of the Reactor Oversight Project with Beyond Nuclear, an organization opposed to nuclear power, says that regulators and utilities began raising concerns about the containment design as far back as the 1970s.

“The key concern has always been that the containment structure was undersized, and that a potential accident could overwhelm and rupture it,” Mr. Gunter said.

The Mark 1 reactors in the United States have undergone a variety of modifications since these initial concerns were raised. Among these, according to Mr. Lochbaum, were changes to the doughnut-shaped torus — a water-filled vessel encircling the primary containment vessel that is used to reduce pressure in the reactor. In early iterations, steam rushing from the primary vessel into the torus under high pressure could cause the vessel to literally jump off the floor.

In the late 1980s, all Mark 1 reactors in the United States were also ordered to be retrofitted with venting systems to help reduce pressure in an overheating situation, rather than allow it to build up in a containment system that regulators were concerned could not take it.

It is not clear precisely what modifications were made to the Japanese boiling water reactors now failing, but James Klapproth, the chief nuclear engineer for General Electric Hitachi, said a venting system was in place at the Fukushima plants to help relieve pressure.

With electrical power cut off in the aftermath of the earthquake and backup sources of power either failing or exhausted, workers have been struggling to inject seawater into the reactor to maintain control, but they have had some trouble venting the resulting steam.

Mr. Gunter argued that in any event, such venting amounts to a circumvention of the whole notion of containment in the first place. “They essentially have to defeat containment to save it,” he said.

What role the specifics of the G.E. design is playing in the rapid deterioration of control at the Fukushima plant is likely to be a matter of debate, and it is possible that any reactor design could succumb to the one-two punch of an earthquake and tsunami like those that unfolded last week in Japan.

Although G.E.’s liability would seem limited in Japan — largely because the regulatory system in that country places most liability on the plant operator, the company’s share price was down more than 2 percent at midday Tuesday as the situation at the Fukushima plant deteriorated.

Still, Mr. Lochbaum said it was important to emphasize that the design specifications for containment and cooling on any reactor are a matter of balance. The primary alternate reactor design, the pressurized water reactor, calls for a thicker and bigger containment structure, for example. A boiling water reactor design like the one at Fukushima does allow for scaling back on the size of the containment system while ostensibly maintaining the requisite safety margins.

In that sense, Mr. Lochbaum said, G.E.’s the boiling water reactors should be no better or worse in weathering accidents than any other design.

Should the ability to cool the reactor completely fail, however, Mr. Lochbaum said, “I’d certainly rather have a bigger, thicker containment structure.”

This article, Reactor Design in Japan Has Long Been Questioned, first appeared in The New York Times.

(Msnbc.com is a joint venture between NBC Universal and Microsoft. GE, which designed the reactors in Japan, is a part owner of NBC Universal.)

Copyright © 2013 The New York Times

Video: New fire erupts at Fukushima plant

  1. Closed captioning of: New fire erupts at Fukushima plant

    >>> tonight japan is dealing with a full scale tragedy, while also trying to contain a full scale nuclear emergency. the release of radiation has prompted a major evacuation. and the people of japan , across a wide area, are now being told to seal themselves in their homes. tonight we have the latest for you on the disaster in japan . the number of confirmed dead just over 3,000. and the missing now standing at close to 7,000. both expected to go much higher. half a million people have been evacuated. almost that number are in shelters. there are still huge shortages of food, fuel, water and shelter. about that radiation leak and the effort to avert an all out meltdown. 70,000 people have been evacuated. 140,000 have been told again to stay in their homes. tonight a handful of very brave nuclear workers are trying to prevent a further disaster, knowing they may pay with their lives. it's where we begin tonight with our chief science correspondent robert bazell in tokyo . bob, good evening.

    >> reporter: brian, the nuclear danger here remains ominous 37 now a second fire is burning. this has already become the worst reactor accident since chernobyl in 1986 .

    >> right, right, right.

    >> reporter: a fright thing scene just outside the evacuation zone. workers decontaminating residents with a new sense of urgency after conditions deteriorated rapidly. satellite photos of the crippled reactor show much of the damage. explosions at numbers one and three destroyed outside buildings. there's no obvious damage to number two, the reactor with the most severe problem a crack in the containment dome that's allowing radiation to leak out. at unit four, a fire was put out, and radiation is leaking from spent fuel rods like this.

    >> since the spent fuel accident, it would be worthy of massive worldwide concern, and we had that on top of three actually reactors that are having core damage going on. it's a very, very bad situation.

    >> reporter: japan 's prime minister urged calm and said there was no evidence the amount of radiation released so far threatened anyone outside the evacuation zone. the one bit of encouraging news from the government, the radiation levels have been dropping in recent levels. ground level winds had been blowing to the east out to sea. but in the past few hours, they shifted south in the direction of tokyo , where officials say radiation levels have been elevated but not dangerous. the company that runs the reactors ordered all but the most essential personnel to leave the site and offered public apologies.

    >> translator: this is a very poor scenario, very bad scenario.

    >> reporter: one big challenge, experts say, because there are only 70 or so workers at the site, reactor problems occur one after the other. those workers who volunteered to stay are facing radiation danger now. many could have gotten very high levels.

    >> they are already being exposed to levels of radiation that are life threatening and will in some cases be fatal.

    >> reporter: many see those workers as great heroes. some lost their homes and families in the earthquake and tsunami, yet they continue at great risk to themselves, to try to prevent another catastrophe in this country. brian?

    >> bob bazell starting us off in tokyo tonight. thanks.

Photos: After Japan's earthquake and tsunami - week 8

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  1. A radiation measuring instrument is seen next to some residents in Kawauchimura, a village within the 12- to 18-mile zone around the Fukushima Daiichi nuclear plant, on April 28. Most residents of Kawauchimura have evacuated in order to avoid the radiation, but some remain in the area of their own accord. (Koichi Kamoshida / EPA) Back to slideshow navigation
  2. A brazier heats the house of Masahiro Kazami, located within a 12-mile radius of the Fukushima Daiichi nuclear plant, April 28. (Koichi Kamoshida / EPA) Back to slideshow navigation
  3. Volunteers help clean a cemetery at Jionin temple in Ishinomaki, Miyagi prefecture, northeastern Japan, on April 29. Many volunteers poured into the disaster-hit region at the beginning of the annual Golden Week holiday. (Hiro Komae / AP) Back to slideshow navigation
  4. Japanese government adviser Toshiso Kosako is overcome with emotion during a news conference on April 29 in Tokyo announcing his resignation. The expert on radiation exposure said he could not stay on the job and allow the government to set what he called improper radiation limits for elementary schools in areas near the tsunami-damaged Fukushima nuclear plant. (AP) Back to slideshow navigation
  5. Fuel rods are seen inside the spent fuel pool of the Fukushima Daiichi nuclear plant reactor 4 on April 30. (Reuters) Back to slideshow navigation
  6. A volunteer girl from Tokyo works to clean the debris of a house in Higashimatsushima, northern Japan, on April 30. (AP) Back to slideshow navigation
  7. Farmer Tsugio Sato tends to his Japanese pear trees in Fukushima city, May 1. He said he expects to harvest the pears in October. Farmers and businesses face so-called "fuhyo higai," or damages stemming from the battered reputation of the Fukushima brand. (Hiro Komae / AP) Back to slideshow navigation
  8. Members of Japan Ground Self-Defense Force in protective gear receive radiation screening in Minamisoma in Fukushima prefecture, after searching for bodies at an area devastated by the March 11 earthquake and tsunami. (Reuters) Back to slideshow navigation
  9. Ruriko Sakuma, daughter of dairy farmer Shinji Sakuma, rubs a cow at their farm in the village of Katsurao in Fukushima prefecture on May 3. Thousands of farm animals died of hunger in the weeks following the quake. (Yoshikazu Tsuno / AFP - Getty Images) Back to slideshow navigation
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Explainer: The 10 deadliest earthquakes in recorded history

  • A look at the worst earthquakes in recorded history, in loss of human life. (The March 11, 2011, earthquake and tsumani that affected eastern Japan is not included because the fatalities caused, about 15,000, are fewer than those resulting from the temblors listed below.) Sources: United States Geological Survey, Encyclopedia Britannica

  • 1: Shensi, China, Jan. 23, 1556

    Magnitude about 8, about 830,000 deaths.

    This earthquake occurred in the Shaanxi province (formerly Shensi), China, about 50 miles east-northeast of Xi'an, the capital of Shaanxi. More than 830,000 people are estimated to have been killed. Damage extended as far away as about 270 miles northeast of the epicenter, with reports as far as Liuyang in Hunan, more than 500 miles away. Geological effects reported with this earthquake included ground fissures, uplift, subsidence, liquefaction and landslides. Most towns in the damage area reported city walls collapsed, most to all houses collapsed and many of the towns reported ground fissures with water gushing out.

  • 2: Tangshan, China, July 27, 1976

    Chinese Earthquake
    Keystone  /  Getty Images
    1976: Workers start rebuilding work following earthquake damage in the Chinese city of Tangshan, 100 miles east of Pekin, with a wrecked train carriage behind them. (Photo by Keystone/Getty Images)
    Magnitude 7.5. Official casualty figure is 255,000 deaths. Estimated death toll as high as 655,000.

    Damage extended as far as Beijing. This is probably the greatest death toll from an earthquake in the last four centuries, and the second greatest in recorded history.

  • 3: Aleppo, Syria, Aug. 9, 1138

    Magnitude not known, about 230,000 deaths.

    Contemporary accounts said the walls of Syria’s second-largest city crumbled and rocks cascaded into the streets. Aleppo’s citadel collapsed, killing hundreds of residents. Although Aleppo was the largest community affected by the earthquake, it likely did not suffer the worst of the damage. European Crusaders had constructed a citadel at nearby Harim, which was leveled by the quake. A Muslim fort at Al-Atarib was destroyed as well, and several smaller towns and manned forts were reduced to rubble. The quake was said to have been felt as far away as Damascus, about 220 miles to the south. The Aleppo earthquake was the first of several occurring between 1138 and 1139 that devastated areas in northern Syria and western Turkey.

  • 4: Sumatra, Indonesia, Dec. 26, 2004

    Aerial images show the extent of the devastation in Meulaboh
    Getty Images  /  Getty Images
    MEULABOH, INDONESIA - DECEMBER 29: In this handout photo taken from a print via the Indonesian Air Force, the scene of devastation in Meulaboh, the town closest to the Sunday's earthquake epicentre, is pictured from the air on December 29, 2004, Meulaboh, Aceh Province, Sumatra, Indonesia. The western coastal town in Aceh Province, only 60 kilometres north-east of the epicentre, has been the hardest hit by sunday's underwater earthquake in the Indian Ocean. Officials expected to find at least 10,000 killed which would amount to a quarter of Meulaboh's population. Three-quarters of Sumatra's western coast was destroyed and some towns were totally wiped out after the tsunamis that followed the earthquake. (Photo by Indonesian Air Force via Getty Images)

    Magnitude 9.1, 227,898 deaths.

    This was the third largest earthquake in the world since 1900 and the largest since the 1964 Prince William Sound, Alaska temblor. In total, 227,898 people were killed or were missing and presumed dead and about 1.7 million people were displaced by the earthquake and subsequent tsunami in 14 countries in South Asia and East Africa. (In January 2005, the death toll was 286,000. In April 2005, Indonesia reduced its estimate for the number missing by over 50,000.)

  • 5: Haiti, Jan 12, 2010

    Haitians walk through collapsed building
    Jean-philippe Ksiazek  /  AFP/Getty Images
    Haitians walk through collapsed buildings near the iron market in Port-au-Prince on January 31, 2010. Quake-hit Haiti will need at least a decade of painstaking reconstruction, aid chiefs and donor nations warned, as homeless, scarred survivors struggled today to rebuild their lives. AFP PHOTO / JEAN-PHILIPPE KSIAZEK (Photo credit should read JEAN-PHILIPPE KSIAZEK/AFP/Getty Images)

    Magnitude 7.0. According to official estimates, 222,570 people killed.

    According to official estimates, 300,000 were also injured, 1.3 million displaced, 97,294 houses destroyed and 188,383 damaged in the Port-au-Prince area and in much of southern Haiti. This includes at least 4 people killed by a local tsunami in the Petit Paradis area near Leogane. Tsunami waves were also reported at Jacmel, Les Cayes, Petit Goave, Leogane, Luly and Anse a Galets.

  • 6: Damghan, Iran, Dec. 22, 856

    Magnitude not known, about 200,000 deaths.

    This earthquake struck a 200-mile stretch of northeast Iran, with the epicenter directly below the city of Demghan, which was at that point the capital city. Most of the city was destroyed as well as the neighboring areas. Approximately 200,000 people were killed.

  • 7: Haiyuan, Ningxia , China, Dec. 16, 1920

    7.8 magnitude, about 200,000 deaths.

    This earthquake brought total destruction to the Lijunbu-Haiyuan-Ganyanchi area. Over 73,000 people were killed in Haiyuan County. A landslide buried the village of Sujiahe in Xiji County. More than 30,000 people were killed in Guyuan County. Nearly all the houses collapsed in the cities of Longde and Huining. About 125 miles of surface faulting was seen from Lijunbu through Ganyanchi to Jingtai. There were large numbers of landslides and ground cracks throughout the epicentral area. Some rivers were dammed, others changed course.

  • 8: Ardabil, Iran, March. 23, 893

    Magnitude not known, about 150,000 deaths

    The memories of the massive Damghan earthquake (see above) had barely faded when only 37 years later, Iran was again hit by a huge earthquake. This time it cost 150,000 lives and destroyed the largest city in the northwestern section of the country. The area was again hit by a fatal earthquake in 1997.

  • 9: Kanto, Japan, Sept. 1, 1923

    Kanto Damage
    Hulton Archive  /  Getty Images
    1923: High-angle view of earthquake and fire damage on Hongokucho Street and the Kanda District, taken from the Yamaguchi Bank building after the Kanto earthquake, Tokyo, Japan. (Photo by Hulton Archive/Getty Images)
    7.9 magnitude, 142,800 deaths.

    This earthquake brought extreme destruction in the Tokyo-Yokohama area, both from the temblor and subsequent firestorms, which burned about 381,000 of the more than 694,000 houses that were partially or completely destroyed. Although often known as the Great Tokyo Earthquake (or the Great Tokyo Fire), the damage was most severe in Yokohama. Nearly 6 feet of permanent uplift was observed on the north shore of Sagami Bay and horizontal displacements of as much as 15 feet were measured on the Boso Peninsula.

  • 10: Ashgabat, Turkmenistan, Oct. 5, 1948

    7.3 magnitude, 110,000 deaths.

    This quake brought extreme damage in Ashgabat (Ashkhabad) and nearby villages, where almost all the brick buildings collapsed, concrete structures were heavily damaged and freight trains were derailed. Damage and casualties also occurred in the Darreh Gaz area in neighboring Iran. Surface rupture was observed both northwest and southeast of Ashgabat. Many sources list the casualty total at 10,000, but a news release from the newly independent government on Dec. 9, 1988, advised that the correct death toll was 110,000. (Turkmenistan had been part of the Soviet Union, which tended to downplay the death tolls from man-made and natural disasters.)

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