Journalism in the Public Interest

Status of Spent Nuclear Fuel in Question at Crippled Japanese Power Plant

Opponents of nuclear power have warned for years that if spent fuel pools lost water, it could lead to a fire and a catastrophic release of radiation. Now, there have been hydrogen explosions at two of the reactor buildings housing spent fuel pools at the Fukushima Daiichi Nuclear Power Station.

A March 14, 2011 satellite view of the Fukushima Dai-ichi Nuclear Power plant in Futaba, Japan after a massive earthquake and subsequent tsunami. (Photo by DigitalGlobe via Getty Images)

Update: As we have noted, there has been a fire and the spent fuel rods of one of Fukushima's reactors are now at risk.

Concerns about a radiation release from the Fukushima Daiichi power facility have focused on its stricken nuclear reactors, but the plants of that design also store highly radioactive spent fuel in pools outside the protective containment structure that surrounds the reactor itself.

Opponents of nuclear power have warned for years that if these pools drain, either by accident or terrorist attack, it could lead to a fire and a catastrophic release of radiation. Now, there have been hydrogen explosions at two of the reactor buildings housing spent fuel pools at Fukushima.

This diagram shows where spent fuel pools are typically located in the 1970s-vintage GE Mark I reactor design in use at Fukushima units 1, 2 and 3, where officials suspect reactor fuel has melted.

The nuclear industry says fears about the storage pools at U.S. plants are overblown because the pools are protected and, even if fuel is exposed to the air, the chance of a fire is incredibly small. And with limited information being released about conditions at Fukushima, the status of spent fuel pools is uncertain.

The fuel that powers a nuclear reactor only works so long. When it is exhausted, it is still radioactive and physically very hot. So it needs to cool in a deep tank of water before it can be stored elsewhere.

At Fukushima, these tanks are attached to the outside of the reactor’s containment structure. The pools are deep – typically the fuel lies under 25 feet of water. Although the concrete-and-steel containment is designed to trap radiation leaks, there is no such protection for pools outside.

When the U.S. reactors were built, everyone assumed the government would open a national storage center to handle the tons of radioactive spent fuel from nuclear plants. The proposed Yucca Mountain site in Nevada never opened, so the old fuel sits at nuclear plants across the country.

Many plants have been operating for 20 years and have tons of used fuel in cooling pools.

The concern is that if the water in the pools ever drops too low, the zirconium cladding that holds the radioactive fuel pellets would begin to heat up and eventually burn. And if it did, the smoke from the fire could carry radiation away from the plant because the pool is outside the containment.

“People should be very concerned because the NRC has acknowledged that spent fuel pools that are not located inside the containment have the potential to cause catastrophic accidents,” said Diane Curran, a lawyer who has represented environmental groups and governments in challenges to fuel storage plans.

“These are not high-probability accidents,” Curran said, “but we have seen how low-probability accidents can happen.”

After the Sept. 11 terrorist attacks, Congress asked the National Academies to study the vulnerability of spent fuel to a terrorist attack.

The resulting 2005 report, “Safety and Security of Commercial Spent Nuclear Fuel Storage,” concluded that “an attack which partially or completely drains a plant's spent fuel pool might be capable of starting a high-temperature fire that could release large quantities of radioactive material into the environment.”

The report found that the vulnerability of the spent fuel to fire depends on how old it is and how it is stored. As the fuel ages, it cools, so it becomes less susceptible to a fire.

“The industry standard is that fuel that is older than five years can be dry-stored,” said Kevin Crowley, director of the nuclear and radiation board for the National Research Council, part of National Academies.

The report recommended that the nuclear industry take steps to decrease the vulnerability of the storage pools to fire. Some of those steps are classified, Crowley said. But he said others, like making sure there were fire hoses or spray systems above the pools, were pretty simple.

Crowley said he does not have enough information on the status of the Japanese plants to say whether the pools are vulnerable.

The Nuclear Regulatory Commission did not reply to an e-mail for this story. The agency says on its website that it is confident the spent fuel pools at U.S. plants are safe.

The nuclear industry disagreed with the national academy about the vulnerability of the spent fuel to a fire. Carl Baab, a spokesman for the Nuclear Energy Institute, said studies show that the risk is low in part because the spent fuel contains relatively little energy compared to the fuel inside the reactor.

“The potential for a fire from damage or loss of water is so remote that we believe it is misleading,” he said.

Baab also said plant workers only need to replace about 25 gallons of water each day to the fuel pool to maintain water levels in the event that primary systems were knocked out.

How hydrogen explosions at Fukushima may have affected the spent fuel pools is unclear.

Some nuclear plants have moved their older fuel into reinforced metal storage casks that are located away from the reactor building. According to information on the website of Tokyo Electric Power Co., which operates the Fukushima facility, more than 200 tons of spent fuel is stored in casks.

Baab said the nuclear power industry has been pushing the federal government to open a long-term storage site for nuclear waste.

“From the beginning it was intended to stay at the sites for a relatively short time,” he said. “It was never intended or designed that it remain at the site.”

For Pete’s sake, just look at the satellite photo of the Fukushima power plant. As is clearly seen, the top third of reactor #1’s building was blown off by a simple hydrogen gas explosion, yet the building’s lower walls remain completely intact. Also clearly seen is that #3’s explosion has left nothing but the building’s skeletal steel framework. This extensive damage most likely was not caused by a simple explosion of hydrogen gas which built up in the top third of the reactor’s building structure. The most likely cause is a criticality event occurring within the reactor’s partially melting down core since the core’s design is inherently flawed.

@GoneToPlaid: Please do not pretend to know information that you do not. Spreading fear and misinformation based on your assumptions is not helpful to anyone.

Anyone give any thought as to the outcome of a “depth-charge” dropped in a fuel storage pool?  Convection circulation of nuclear fuel material could be pretty interesting…

Uh Josh, I’m spreading fear and misinformation? This just in as of 15 minutes ago: Japan faces catastrophic radiation leak, warns people to stay indoors.

In a nationally televised statement, Prime Minister Naoto Kan said radiation has spread from the three reactors of the Fukushima Dai-ichi nuclear plant in one of the hardest-hit provinces in Friday’s 9.0-magnitude earthquake and the ensuing tsunami.

“The level seems very high, and there is still a very high risk of more radiation coming out,” Kan said.

He warned there are dangers of more leaks and told people living within 19 miles (30 kilometers) of the Fukushima Dai-ichi complex to stay indoors to avoid radiation sickness.

Chief Cabinet Secretary Yukio Edano said a fourth reactor at the complex was on fire and more radiation had been released.

“Now we are talking about levels that can damage human health. These are readings taken near the area where we believe the releases are happening. Far away, the levels should be lower,” he said.

Powers-that-be confident on safety of spent fuel pools, yet one burned for hours in Japan today.

Check out the Reuters articles regarding previous plant owner cover ups.

Yes, you are spreading fear and misinformation when you talk about critical excursions.  The reactors were scrammed with control rods, so the reactor cores are below critical mass.

I agree with you that there is clearly core damage, as Cs-137 and I-131 are being released, but had there been a critical excursion the US carrier that was offshore would have had warnings flashing all over the ship from its radiometers.  Remember, it’s a nuclear carrier with its own full set of radiation measures for crew safety.  That’s why they detected the isotopes so quickly and know exactly how much exposure the crew has.  I do also agree with you that there is a lot of conflicting information in the reports, and that there is likely more radiation being released than the Japanese press is admitting.

Hydrogen gas causes impressive explosions, plenty to damage a building, and can disperse reactor core material very effectively.

the IAEA has said that a fuel pool was on fire and releasing radiation into the atmosphere (@ reactor #4 that uses MOX fuel)
Tepco has however said that the fire has now been put out (they also evacuated all employees except for 50 due to the fire)

@mike - only reactor #3 uses MOX fuel

Good information, one point of clarification I would make regards this sentence:

“When it is exhausted, it is still radioactive and physically very hot.”

I might say instead:

“When it is exhausted, it is still radioactive and continues to produce a significant amount of heat from radioactive decay for a year or more.”

It’s not so much that it is “hot” - which might imply that after removing it from the reactor, all you have to do is cool it down once and you’re done - as that it continues to produce heat from radioactive decay for a long period after it is removed, which heats up (and eventually boils, if not cooled) the water it is immersed in.

This article is part of an ongoing investigation:
Nuclear Safety

Nuclear Safety

With the disaster in Japan, we're investigating questions about nuclear safety.

The Story So Far

Following a massive earthquake and tsunami in Japan, hydrogen explosions rocked three reactors at the Fukushima Daiichi nuclear power plant. Radioactive spent fuel stored in pools was also affected, especially at one reactor—the plant has a total of six—where multiple fires erupted. Evacuation orders were issued, potassium iodine tablets distributed, and plant employees used seawater and external electrical power to cool the stricken reactors, three of which had a partial core meltdown.

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