Last updated 12:30 p.m. ET March 18:
Should Japan's stricken nuclear reactors be entombed like the site of the Chernobyl accident? Authorities in Japan aren't yet thinking about a permanent entombment. But they are looking into the idea of covering up the "hot" fuel rods being stored at the site with piles of sand and soil, laced with lead and neutron-absorbing boron.
The procedure is laid out in a U.S. Nuclear Regulatory Commission study on strategies for responding to problems with spent fuel rods — exactly the kind of problem that the Japanese are facing at the Fukushima Dai-ichi nuclear complex. In normal circumstances, those fuel rods are cooled off in deep pools of water. The problem is that the water in the pools at Fukushima is boiling off, and it's been devilishly hard to get more water in.
Burying the rods in tons of material would pose a huge logistical challenge, but if it could be done, that might well reduce the risk of a huge radioactive release as the uranium fuel breaks down — and buy time for dealing with the other problems at the nuclear plants.
The idea of burying the Fukushima complex has come up before, and theoretical physicist Michio Kaku made a strong pitch for the plan on MSNBC's "Jansing & Co." show. Right now, the Japanese are trying to spray water on the reactors as well as a fuel-rod storage pool that's heating up — but Kaku said that strategy was like using "squirt guns against a raging forest fire."
Kaku said that unless there was quick relief, the workers fighting against the meltdown might have to withdraw — potentially leaving the complex vulnerable to multiple meltdowns and a fallout-spewing fire.
"I would personally advocate the Chernobyl option," Kaku said. "Do what Gorbachev did in 1986. Call out the Japanese air force, get the Japanese army to bring a fleet of helicopters armed with sand, boric acid and concrete and entomb this entire reactor. Bury it in concrete."
Isn't it too early to take such a drastic step?
"Well, they keep saying that the thing is stable," Kaku said. "That's like ... hanging on your fingernails, and you're saying, 'It's stable, it's stable.' Every six hours it gets worse, and it's an option."
He said that if he had the ear of Japan's prime minister, he'd recommend having the helicopters on standby right now.
Kaku may be a physicist at the City College of New York, but his specialty is string theory rather than nuclear engineering. So what do the engineers say?
"That certainly might turn out to be an option," Elmer Lewis, professor emeritus of mechanical engineering at Northwestern University, told me today. But burying the entire site this stage "would be very premature at this point."
'Cause for hope'
Although it may not look like it, Japanese workers just might be making slow headway in the fight to stabilize the Fukushima reactors, thanks to the continued cooling of the damaged cores, said physicist Ken Bergeron, an expert on meltdowns who worked on reactor accident simulations for Sandia National Laboratories in New Mexico. The uranium chain reaction was shut down immediately after last Friday's 9.0 earthquake, and the fuel rods' radioactive decay heat is slowly ebbing away. Those damaged fuel rods are still apparently contained within the reactors' pressure vessels, which is also good news.
"There's cause for hope," Bergeron said on MSNBC. "Time is really on our side."
The spent fuel rods are a different matter. They may still be heating up, and the rods' zirconium cladding is being eaten away. Unless the Japanese response teams can keep those rods covered by water, the potential for a dangerous fire and a far more serious release of radiation will continue.
"We have much less history on how to deal with that," Lewis said.
Princeton nuclear physicist Frank von Hippel, a former Clinton administration official, doubted that dropping tons of material on the site would work at this point in the crisis. "I don't think that you could cover the fuel while it is so hot," he told me in an e-mail. "It would disintegrate concrete, for example. For the near term, covering it with water is the only option. Unfortunately, Kaku says more than he knows."
The best-case scenario would include restoring electrical power to the site, as the Japanese are hoping to do in the next day or so. That would give emergency crews a better method to get water into the reactors as well as into the fuel-rod storage pools. The cooldown routine would be resumed, the decay heat from the fuel rods would dissipate, and in a matter of weeks, the crews could focus on cleaning up the Fukushima reactors.
David Lochbaum, a nuclear plant engineer who is now director of the Nuclear Safety Project for the Union of Concerned Scientists, an activist group, said using water for the cooldown is the preferred option. But he said Japanese authorities should be prepared to dump sand on the rods if they couldn't get enough water to the site.
"If you have only one option left, I'd use it," he told me.
Getting the nuclear fuel under control is the first priority. The long-term fate of Fukushima is a matter to consider later.
"The plant is not usable in the future. It's contaminated. It's broken. That's my opinion at this point," nuclear critic Greg Mello, executive director of the Los Alamos Study Group, said on MSNBC. "It has to be cooled. It's not a matter of just burying it. It's not the same as Chernobyl."
Lewis said the authorities should convene a panel of experts from around the world to look at the alternatives. "If the cores are badly damaged, the major decision is, do you leave them in place and cover them up, or do you remove them and take them to some suitable disposal site," he said.
The cleanup phase of the crisis will last many years — and some experts say Fukushima may well end up like Chernobyl, whether it's actually buried in concrete or not. "This is an area you would certainly want to keep people away from ... for a long time," Jeffrey Merrifield, a former commissioner on the Nuclear Regulatory Commission.
More on Chernobyl and Fukushima:
- U.S. military detects more radiation
- What is Japan doing to fix reactors?
- If there's a meltdown, then what?
- Q&A: Clearing up nuclear questions
- Cosmic Log archive on the Japan crisis
- Special report on the disaster in Japan
- Looking back at the Chernobyl disaster
- Scientific American: Chernobyl getting a new tomb
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