Lessons Learned: The Tragedy at Fukushima

photo: Allison Macfarlane
March 20, 2015

On March 11, 2011, there was a 9.0 magnitude earthquake off the eastern coast of Japan. This megaquake caused a massive tsunami that inundated the Japanese coastline. When the wave hit the nuclear power plant at Fukushima Daiichi, the nuclear power plant lost all backup power, creating one of the worst nuclear disasters in history. As we approach the 4th anniversary of this tragedy, GW Professor and former Chair of the U.S. Nuclear Regulatory Commission Allison Macfarlane provides an analysis of what happened at Fukushima Daiichi, the effects of this meltdown, and what lessons were learned by the nuclear industry and the international community.

 

Q:  Can you talk about the events that led to the meltdown?

Dr. Macfarlane: The unique thing about nuclear power plants is they exist to create electricity, but they can’t exist without electricity because you have to keep the fuel cool. To do that, you have to add and circulate water.

Initially after the earthquake, the nuclear power plants on that part of the coast lost what we call “off-site power.” All nuclear power plants have backup sources of power in case they do lose off-site power, because it does occasionally happen. When they lost off-site power because of the earthquake, their diesel generators started up just fine.

They were humming along, but 45 minutes later a massive tsunami came along.  It was much larger than anyone had ever expected.  It was probably around 45 feet high, a 45-foot wall of water.  Unfortunately, the backup diesel generators and the fuel supplies were located in the basements of the reactor buildings. The tsunami took out the diesel generators and the fuel supplies and even the batteries.

They experienced what is termed “station blackout.”  This means the nuclear reactors had no power, so they couldn’t run water to keep the fuel covered and cool.  As the temperatures began to rise in the reactor vessels, the fuel started to be uncovered.

The uncovered fuel heated up even more and eventually began to melt, slumping to the bottom of the reactor vessel. As the fuel became uncovered, a reaction between the steam from the boiling water and the zirconium-based cladding of the fuel [the outer layer of the fuel rods] formed hydrogen gas. High pressures in the reactor vessels caused leaks of radioactivity and hydrogen into the containment, which also was under pressure and formed leakages. The radioactivity and hydrogen eventually leaked out of the containment into the outer building. Once enough hydrogen collected it ignited. That’s why you saw these explosions in these buildings.

 

Q:  Could this type of a nuclear accident happen again?

Dr. Macfarlane: The problem is that it will likely happen differently the next time, in a way we haven’t imagined. Each accident occurs in a way we haven’t imagined. Charles Perrow wrote a book called Normal Accidents that discusses this.

We have these incredibly complex technical systems where you get these tightly coupled sequences of events. We haven’t imagined how these events could sequence themselves. In March 2011, it made sense for the diesel generators to be in the basement of the power plant because that was the most stable location, seismically. If you’re just expecting earthquakes, it’s probably better to have the generators in the basement. If you’re expecting tsunamis, then maybe not so much. What I’m trying to say is that this is really complicated.

Yes, we could see a different kind of accident. Nonetheless, we need to make sure that now we have the knowledge of how this unfolded, to a degree, and some of the errors that were made. Why they were made and who’s to blame, I’m not going to try to speculate.

 

Q:  What are some of the immediate and longer‑term effects  with regard to the environment and population relocation  that we’ve seen come out of this?

Dr. Macfarlane: There are a lot of them. One thing that we hadn’t thought about before was dealing with radioactive waste generated from a reactor accident.

Just a brief explanation of a nuclear power plant. You have the uranium fuel that’s in a reactor vessel, which is a thick steel vessel. If that is breached, there’s another layer of protection called containment. The containment is a steel-reinforced concrete structure — it’s very thick — that surrounds the reactor vessel.

In this case, the reactor vessel started to leak. The hydrogen seeped out. The pressure built up in the containment. Relieving the pressure is done through venting gases to the outside world – but because they had no filter for the vent — it meant that they were going to release radioactivity into the environment, but still maybe not as much as ended up being released. Instead, the hydrogen gas explosions “vented” the buildings.

Now there are still areas that are contaminated enough that people aren’t allowed to move back in. Basically 160,000 people were displaced. That’s a substantial population. You’ve got these huge effects there.

You’ve got the land that's contaminated. You’ve got people who have lost their homes, lost their livelihoods. You’ve got a lot of farming and agriculture that has been affected in that part of the country.

There was also a lot of the atmospheric radiation going out to sea. In addition, there were radiation leaks from contaminated water stored in tanks at the site.  The water table there is very high — so high that groundwater actually leaks into the basements of the reactor buildings. It always needed to be actively pumped out. They’re basically pumping off 400 tons of contaminated water a day. The basements of these buildings are contaminated. The groundwater that seeps in gets contaminated. They have this huge water clean-up problem.

The fishing industry there has been really damaged because nobody wants to buy fish from that area. There is a fair amount of radioactive contamination in parts of the local seabed.

There was also a plume of radioactivity that was going across the Pacific Ocean, but essentially, what arrived on our West Coast was 100 times lower than radiation doses allowed in the U.S. drinking water standard. It’s irrelevant to us, but it’s measurable.

Another effect is that this ended up shutting down all their nuclear power plants — at least temporarily.  Before the accident, up to 30 percent of their electricity came from nuclear power. They’ve had to — over the last four years — find other sources for that electricity. That means they’ve basically been importing a lot more gas and oil to make up for it.

This has really hurt the Japanese economy. The issues are enormous.

 

Q:  When you were the Chair at the U.S. Nuclear Regulatory Commission, one of your priorities was to respond to what we saw at Fukushima. Can you talk a little bit about the U.S. response?

Dr. Macfarlane: The NRC immediately did an analysis of lessons learned. They developed 12 recommendations, which the commission then prioritized into three tiers. They’re working hard to get that first tier done, mostly, by 2016.

That includes requiring plants to add extra equipment so that if there is some kind of emergency from natural disaster, that they have the equipment on-site, and they’re also required to have off-site equipment brought on-site within 24 hours.

For the plants that are of the Fukushima design, they’re required to have hardened vents that can be opened in the case of the need to vent the containments. These vents should be able to operate under the temperatures, pressures, and radiation conditions of accidents.

They’re also doing a flooding and seismic hazard review of each of the power plants because that hasn’t been updated in a really long time.

They’re also working on a number of rulemakings to codify all of this and to codify also the response piece to make sure that plants are able to communicate under these kinds of accident conditions.

 

Q:   Do you think that we've seen the nuclear industry go far enough, so far, in responding to the things that we've seen, or do you think we still have a ways to go?

Dr. Macfarlane: The industry has been working hard on getting this — what the NRC called the “Mitigating Strategies Order” — addressed, which is acquiring and staging all that extra equipment around their sites. I’m concerned that they don't want to do a lot more, and I think there are more issues that they need to consider and address. These include some of the other recommendations that the Nuclear Regulatory Commission made initially.