Asteroid Impact, Asteroid Tsunamis and Nuclear Facilities

Tsunamis are waves in the ocean or lakes generated by abrupt vertical movement of the seafloor or lake floor by earthquakes, volcanic eruptions, landslides, and, rarely, asteroid impact. 

City of Richmond, British Columbia, Canada

There are things that are important enough that you don't tolerate any risk. You have to have data to work with to generate reliable risk estimates. It just doesn't work for rare but catastrophic events.

- David Schindler

I wrote most of this post (below the line) a few months after the asteroid strike on Russia in February 2013. At the time I thought it might have been a little excessive to worry about such a low-probability event, but recent news makes me feel vindicated. This really is a problem that our society should wake up to because it highlights once again one of the many ways that the nuclear legacy has many shocks and surprises in store for future generations. Benjamin Hart, in The Huffington Post, reported today:

Bad news, earthlings. A former NASA scientist says it's mere happenstance that an Armageddon-style asteroid hasn't hit a densely populated area in the last few years. On Tuesday, the B612 Foundation, which is devoted to preventing the next deep impact, will present data from a nuclear-weapons test warning satellite showing that far more asteroids have hit earth in the past few years than previously thought, the organization announced on its website.

The data, collected from a nuclear missile detection system that picks up large blasts on earth, shows that since 2001, asteroids have caused 26 explosions on the scale of an atomic bomb. 

“This data shows that asteroid impacts are NOT rare, but actually 3-10 times more common than we previously thought,” Ed Lu, one of the astronauts working on the project, said in a statement. "The fact that none of these asteroid impacts shown in the video was detected in advance is proof that the only thing preventing a catastrophe from a 'city-killer' sized asteroid is blind luck."

It is interesting that the scientists tell us that the asteroid would be comparable to a nuclear weapon, but they don't seem to be thinking about the other nuclear implications of an asteroid strike. An asteroid impact on a large city would also be likely to take out nuclear weapons and/or nuclear power plants and spent fuel storage pools. The result would be much more than the destruction of a city. It would likely include an event as severe as, or more severe than Chernobyl and Fukushima.

I wrote the paragraphs below in 2013, contemplating the risk of asteroid impacts and the tsunami waves they could cause on large bodies of water.
_____________________

Maybe I think too much. But I’d worry less if the people who ran the nuclear industry worried a little more. Then again, if they worried more they might come to the logical conclusion that there shouldn't be nuclear plants.

Today I was thinking outside the box, wondering if I could think of a black swan event that no one else is paying attention to. Perhaps I’m doing this just for distraction, to take my mind off the more immediate danger close to home in Japan. Lately the world has been paying attention finally to the potential catastrophe that might unfold after work begins next month on Fukushima Daiichi Nuclear Power Plant Unit 4 Spent Fuel Pool (What’s the abbreviation for this? F1NPP-4SFP?) So for distraction, my thoughts wandered back to my original home by Lake Ontario, and I wondered if there isn’t some risk there that the Canadian nuclear people haven’t taken into account.

I know that nuclear plant operators have considered asteroid impacts before, but they have made no special measures to prepare for them. The thinking seems to be that the risk is too miniscule to think about, but if it happens, the impact will be too huge to worry about. If an asteroid landed near a nuclear plant, everyone in the area would be cooked anyway, so there’s no point in thinking about it.

The risk is miniscule because an asteroid that was big enough to do damage to a plant, but small enough not to cause a catastrophe on its own, would be pretty small. The chance of a small asteroid landing on a reactor building is just too small to worry about. The risk can never be zero, so forget about it. We accept this risk in order to have electricity, right?

But is the risk really that small? Orders of magnitude smaller than the risk of a giant tsunami in Japan? After the light show over Russia in February 2013, asteroid impacts suddenly didn’t seem like a remote possibility.

The question seems to be: Could there be something a little larger than the asteroid that landed on Russia, but small enough not to wipe out civilization, were it not for nuclear facilities that would melt and lay waste to the environment?

At Answers.com someone who was apparently knowledgeable in these matters, posted a good response to the question “What would happen if an asteroid hit the Great Lakes?”

This person set the variables as:

• 1 mile wide asteroid, solid rock
• Lake Michigan, 50 miles from Chicago
• impact: 12 miles per second
• impact in 800 feet of water 

There is a blinding flash of light, then a magnitude 8 earthquake. Buildings begin to crumble, meteor fragments begin to rain down on the city. A blast wave follows, then a deafening wall of sound. Finally, a 200-foot tsunami hits all shores of the lake and washes inland for 150 miles. But don’t worry, it happens only every few million years, and it probably wouldn’t land in the Great Lakes. 

So fine. But what if we change the variables a little? The Tunguska event of 1908 is believed to have been caused by an air burst of a rock 60–190 meters wide, and that was powerful enough to have had a force of 10-15 megatons and knock down trees over 2,150 square kilometers. If something of this size hits Chicago, Detroit or Toronto, no one will be worrying about radiation from nearby nuclear power plants. The decommissioning and waste disposal problem will be solved.

How about other scenarios? Should we worry? Maybe these things happen only over Russia. But just for fun, let’s consider the surface area of Lake Michigan, Lake Huron, Lake Erie and Lake Ontario, the four Great Lakes that have nuclear power plants situated nearby. How big would an asteroid have to be to cause a tall tsunami on these lakes, a wave bigger than anything power plant operators have planned for? My guess is that it could be much smaller than the one-mile wide rock, smaller than the Tunguska rock, but bigger than what landed on Russia in 2013. It would be a damaging wave, but the big cities on the lakes could recover, if they didn’t have to deal with nuclear fallout in the aftermath. Considering the surface area of the lakes and the frequency of asteroid impacts, this is an event “with probability significantly higher than zero,” as they like to say in the cautious lingo of risk assessment.

Now my mind goes back to something Arnie Gundersen said to Canadian nuclear regulators about the ultimate cause of the problems at Fukushima. We all know that the earthquake damaged the reactors and knocked down the outside transmission lines. We know that the waves flooded the backup power systems. However, what has been overlooked is that even if electrical power had not been cut, there still would have been the damage done to the pumps' cooling systems by the tsunami and earthquake. There is only one factor that leads to meltdown--loss of cooling, which can be caused by loss of power to the cooling system or physical damage to it. Fukushima Daiichi lost power, but the tsunami waves also did physical damage to the cooling system, and this on its own was enough to devastate the plant.* That’s the damage that an unexpectedly tall wave on the Great Lakes could do to a nuclear plant.

*From Peter Melzer's blog: 
Why Fukushima's Reactors Failed. November 4, 2013

... electric power must be available and the residual heat removal system must remain operable for nuclear reactors of the Fukushima type to successfully complete an emergency shutdown. These conditions impose a major constraint on accident recovery, representing a fundamental weakness of the reactor design. The residual heat removal system must remain operable under the conditions of flooding and station blackout.

Thirty reactors of this type currently operate in the United States. A number are sited in flood-prone areas. A moratorium should be imposed on these reactors, until the operators can ascertain that service water pumps are protected against inundation, debris, and loss of power.