Chain of events, cause and effect. We analyze what went right and what went wrong, as we
discover that many outcomes can be predicted, planned for, and even prevented. I'm John
Chidgey, and this is Causality. Causality is part of the Engineered Network.
To support our shows, including this one, head over to our Patreon page, and for other
great shows visit https://engineered.network/ today. Fukushima. On Friday the 11th of March 2011
at 2:46pm local time a magnitude 9.0 earthquake occurred under the sea at a depth of approximately
32 km, 72 km east of the Oshika Peninsula off Tōhoku.
It was the most powerful earthquake to ever hit Japan and the fourth most powerful recorded
since 1900 in the world.
This earthquake occurred where the Pacific Plate is subducting under the plate beneath
northern Honshu.
The Pacific Plate moves at a rate of 8-9cm (3.1-3.5in/yr)
That movement pushes the upper plate down until the accumulated stress causes a seismic
slip rupture event, otherwise known as an earthquake.
The Fukushima 1 nuclear power plant consisted of 6 reactors, 1 at 480 MW, 4 of them at 784
MW each and 1 at 1.1 GW.
There were 3 reactors online at the time of that earthquake, those are reactors 1, 2 and
three and all initiated a SCRAM and a shutdown at the time that the earthquake hit.
Now, SCRAM is a unusual acronym.
In fact, some people have suggested it's not an acronym, it's actually a "back-ronym", which is the
the phenomena where people will fit an expression backwards into an acronym to try and explain
the existence of the acronym, hence "back-ronym."
Kind of like that idea.
Anyway, a SCRAM is supposed to be something like Safety Control
Rod Axe-Man.
And it was originally thought to have come, but the phrase was originally coined apparently by Enrico
Fermi, and he was working on the Manhattan Project on the Chicago Pile One reactor,
and that was in the early 1940s.
And the idea behind an "Axe-Man" is that there's a large
collection of control rods suspended above the reactor core by a rope and an
an axe man with an axe is sent to cut the rope in the event of an out of control reaction.
This particular expression and terminology method, whatever you want to call it, of doing
an emergency shutdown of a nuclear reactor is primarily used these days for Boiling Water
Reactors, BWRs, like Fukushima. I don't want to talk too much about the different designs
of nuclear reactors, but suffice it to say that a SCRAM is an emergency shutdown where
you insert a large number of control rods into the core, so many so that it absorbs
all the Neutrons and completely stops the fission reaction.
So the plants are designed to initiate a SCRAM as soon as there is an earthquake above a
certain trip threshold. This one certainly qualified and a SCRAM was initiated on the
online reactors. So reactors 1, 2, and 3 were in operation. So SCRAMs were initiated on each of them.
Now within minutes all those reactors were shut down but reactors 4, 5, and 6 they were already
shut down in actual they're in preparation for being refueled and when you're refueling what
you'll do is sometimes the fuel rods will be withdrawn from the reactor and stored in a large
pool and in this the case of Fukushima it was in an upper level of the reactor building outside of
of the containment vessel. The exact quantity varies depending upon which reports you read.
Some say as many as 1,533 fuel rods, some as little as 1,330. Irrespective of the number,
let's just say a significant quantity, all of them in fact from reactor 4, they were
in a cooling pool above the reactor on the floor above.
So the reactor four cooling pool was full of fuel rods
that were not in use at the time of the incident.
That actually been put there four months earlier
in November of 2010.
Takes a while for them to cool down a bit.
But reactors five and six were still in their reactors
and they had cooling water being pumped through them
to keep them cool.
So, back to reactors 1, 2 and 3.
The earthquake itself doesn't, just because you have an undersea earthquake doesn't actually
mean you're going to get a significant tsunami.
In this particular case, the break caused by the earthquake caused the sea floor to
rise up by several meters and that displaced an enormous amount of water above it.
And liquids aren't compressible, so the energy had to go somewhere and it travels away from
that upthrust region as waves. The deeper the water, the shallower the waves, but as
you approach shallow water, the wave height increases dramatically. In terms of the upthrust
region, it's quite significant. The upthrust region was between six to eight meters along
a 180 kilometer wide seabed, and that was around about 60 kilometers from the shoreline
on average. In fact, the tsunami was so significant it travelled as far as Chile in South America
and there resulted in a 2 metre wave height. Not enough to cause any damage, but certainly
enough to be quite noticeable. Tsunami waves, of course, arrive as sets of waves. It's
not just one, there's a subsequent series of them. But most tsunami wave heights are
measured by the largest or tallest wave. But the first tsunami waves from this incident arrived at
Kamaishi, and I hope I'm pronouncing that correctly. Apologies if I'm not. At 3:12pm local time, the
height was estimated at about 6.8 metres. They arrived at Sōma at 3:50pm with an estimated height
of 7.3 meters, that's 24 feet, and this was around the time at which the tsunami also reached the
Fukushima 1 power plant. At the plant itself, the waves peaked at a staggering 13 meters, that's 43
feet high, and that easily breached the protective seawall, which was only 10 meters or 33 feet high.
Once the water had passed the seawall, the seawater proceeded to flood all of the low-lying
areas of the plant, and this included the turbine hall and the reactor building. Cars and trucks
were all swept away, overturned, the waves destroyed the pipework, and within minutes
affected the backup diesel generators. And understanding why that's a problem,
we first have to understand about fuel rod cladding and decay heat. So let's start with the
cladding. Zircalloy or alloys of Zirconium, they're used predominantly in BWRs for cladding as it has
very low absorption of thermal Neutrons, meaning they just pass through it and don't affect the
material as they pass through. But it also maintains a high hardness ductility and it's
corrosion resistant. And that's important because if the Neutrons actually interact
with the cladding material, then they will change what that cladding material is. And
as you change what the material is, it changes its chemical properties. So you need something
that's going to essentially be invisible, which is what Zircalloys are, and that's why
they are predominantly used in these nuclear reactors. But it's not all positives. Zircalloy
also reacts with water and at high temperatures with steam. The oxidation of Zirconium by water
releases Hydrogen gas as one of its byproducts. The other problem is that once it passes about
400°C the oxidation rate increases dramatically and that increased rate of release
of Hydrogen for example if you're in an enclosed vessel which this is will increase the pressure
as the pressure increases that also further drives that oxidation process forward at an even faster
rate so essentially the higher temperature leads to high pressure the high pressure leads to a
higher oxidation rate which increases the pressure which leads to a higher oxidation rate.
Now in normal operation it's not a problem because the cooling water will keep the temperature well
under control that's fine. Now after a SCRAM event occurs the reactors aren't actually hot
enough anymore to generate steam to make electricity but they still have some latent heat
and more importantly, they have decay heat. So I mentioned this before, decay heat is something
that it's difficult to get your head around, but when we split Uranium or Plutonium
nuclear fission, we get byproducts and those byproducts are themselves radioactive and as
As they decay, they themselves generate heat as part of their decay reaction.
Essentially decay heat is the term that describes the continuing nuclear reaction.
Despite the fact that the main reaction of the Uranium or Plutonium has ended, the beta
decay of the byproducts of the original fission reaction will still occur.
The decay heat fraction is usually expressed as a fraction of the full power of the reactor.
it starts at about 7% of full power at a 1 second post-SCRAM event and then it reduces
logarithmically so about 4% at 1 minute, 2% at 10 minutes but then it really slows down
and it can take about 5 hours to reach 1% of full load and about 0.2% after 10 days.
Now when we consider the size of some of these reactors we're talking about 768 megawatts
That's a lot of power. 1% of 768 megawatts is still a lot of heat.
So if you don't keep it cool, it's going to get very hot.
And that's a bad thing.
And it takes a long time for the decay heat to actually slow down to a point at which these
things, these fuel rods will actually be able to stay cool in free air
quite some time.
Now all those figures and percentages I just quoted, they're all approximations because
since it clearly it varies based on the type of fuel in question, like if it is
Uranium, Uranium or Plutonium, and therefore the byproducts that you will get from the
reaction. It also depends on the concentration of the fuel and the life of that fuel.
Like, for example, newer fuel will have less byproducts.
So therefore, newer fuel will have less decay heat in theory.
So all those numbers are approximations, but it illustrates the problem.
the decay heat is a problem.
So, OK, it's critically important that the fuel rods are
then kept cool after you have a shutdown for at least a week or
two. And so that that happens, external power is required to
keep the system cool.
You need to keep circulating cool water through those fuel
rods to keep them cool.
Now, ordinarily, that would be taking care of power from the
electrical grid that's backfed, what we call in the industry
backfeeding and the idea is that the power grid then supplies the power to
cool the reactors. However in this particular case all six of the high
voltage transmission lines that connected the power plant to the
electrical grid were destroyed by the earthquake following the tsunami and the
following tsunami I should say. Now the so-called Essential Service Water
Systems that keep the cooling water circulating through the reactor they
have several other backups and the backup system installed on
site, the ESS's at Fukushima, they had an independent,
redundant power system of diesel generators. Now, the generators
were regularly tested to ensure they operated when they had to,
their fuel was topped up, everything was maintained. They
were, as far as we are aware, anyhow, in full working order.
When the SCRAM event occurred, the diesel generators were fully functional,
even when they lost mains power.
However, by the time the tsunami had breached the wall, the diesel generators were
inundated with seawater.
Eleven of the 12 diesel generators failed, and with only one
remaining generator off in a distant part of the plant, it was powering reactor
6. The reactor 6 was already online as we offline sorry which we mentioned before.
On a positive note it continued to circulate cooling water through reactors 5 and 6 and
ensured there was no incident in those reactors so that's something. The impact of the tsunami
had already destroyed the seawater lift pumps on the ocean side of the seawall
because they had been mounted lower and closer to sea level.
And there's additional power systems to circulate cooling water. In this case,
there's an emergency backup battery, a UPS system, that was able to power cooling pumps
for eight hours by design. Unfortunately, the flooding from the tsunami destroyed the batteries
in units one and two because they also were in a low-lying area of the plant.
The slightly newer Unit 3 batteries however were not damaged and surprisingly lasted as long as 30
hours before they were depleted which far exceeded their original 8-hour design life.
Now it's common practice for emergency power systems like those at Fukushima that there's
an external power connection point where you could deliver a mobile portable temporary generator that
that you can then connect in to supply power in a true emergency.
Unfortunately, this connection point had been swamped and was severely damaged by the tsunami
and it rendered it inaccessible for several days.
There was also difficulty in getting the portable generator to the plant.
The reactors themselves, for incidents such as this, have two additional layers of protection.
primary containment vessel, which is a steel and concrete reinforced structure surrounding the core
and a secondary containment vessel.
And that's usually just the reactor building.
And whilst the secondary containment is usually sealed well, it's not reinforced to the same extent as the primary containment vessel.
So a bit more about the timeline.
At 7:03pm
local time, the government declared a nuclear emergency.
By 8:50pm that day, the Fukushima Prefecture Office
ordered a two kilometre radius evacuation zone.
By 9:23pm, the government increased this radius to three kilometres and instructed
residents to stay inside buildings in the next
radius up to 10 kilometres away.
The following day at 5:44am in the morning,
the government ordered a full evacuation to a 10km radius.
And then that evening at 6:25pm,
the government then extended this to 20km away from the plant.
Around lunchtime on day four, following the incident,
the government ordered all residents to stay inside buildings in the area
between 20 to 30km from the plant.
Over the next two weeks,
There were a succession of Hydrogen explosions at reactor 1, 2 and 3.
To list the times mentioned relative from the moment of the primary earthquake,
we'll look at some of these events.
Units 1, 2 and 3 lost AC power when the generators died at 51, 54 and 52 minutes out,
respectively, pretty close together.
There were issues with circulating cooling water in unit 1.
So unit 1, it lost its circulating cooling within one hour.
Unit 2 and 3, 70 and 36 hours out respectively.
The water level had dropped to a critical height because of
accelerated evaporation due to high heat.
Which is what happens when you stop circulating fresh cooling
water. And now, at these points, they are only just covering
the top of the fuel rods.
So at three hours out, 74 and 42 hours,
the units one, two and three respectively.
Because of the low coverage of water
and the low amount of cooling,
damage to the cores began at four hours,
77 hours and 44 hours respectively.
So each of the three cores sustained damage.
The reactor primary pressure containment vessel
sustained damage at 11 hours.
Ultimately, we're only certain of the timing
of this for reactor number one.
Damage occurred to all three,
but the timeline for the exact moment of these
is unclear for units two and three.
Fire pumps were used with fresh water,
spraying the core at 15 hours for unit one
and 43 hours for unit three.
Unit two was never sprayed with fresh water, only seawater,
because it was essentially nearly 30 hours later before it had issues.
Hydrogen explosions occurred due to Zircalloy oxidation at 25 hours for Unit 1
and 68 hours for Unit 3,
causing significant damage to their own and adjacent structures.
The offsite electrical supply became available between 11 to 15 days later
and was brought on in stages for different units.
Fresh water cooling was re-established 14 to 15 days later
for all three units.
On the 25th of March,
the government requested a voluntary evacuation
of all residents in the area
from 20 to 30 kilometer radius from the plant.
About a month later, on the 21st of April,
the government set a 20 kilometer radius
as a no-go zone for all residents.
When the water temperature dropped below 100°C
at atmospheric pressure,
the reactor is said to be in cold shutdown.
It's still pretty hot,
but it's technically a cold shutdown.
The reactor reached cold shutdown
on the 16th of December, 2011.
That's quite some time after the incident.
Nine months.
That's how long it took.
What's interesting is the neighboring Daini Plant,
Fukushima 2, is located some 15 kilometers away from Daiichi.
Now, they were hit by a tsunami as well, of course.
It was only nine meters in height.
the height of the tsunami as it crosses the oceans got a lot to do with the profile of
the seabed as it approaches the shoreline.
Now they still had one of their power lines still available into the plant after the earthquake
and the tsunami had passed.
So whilst there were interruptions of the cooling supply post-SCRAM, with some of the
generators damaged, external power didn't really strictly require them.
Power and cooling systems were restored within 30 hours with new pumps fitted for units 1,
and four and no incidents were recorded at this plant and it was only 15
kilometers away a completely different ending. Radioactive releases into the
environment as a result of this incident. The main radionuclide released was
Iodine-131, has a half-life of about eight days. The other main radionuclide
is Cesium-137. Unfortunately, it has a half-life of about 30 years. It's easily carried in smoke,
tends to settle on land, and contaminates that land for decades. Cesium-134 was also released
in smaller quantities, has a half-life of about two years. One of the problems with Cesium is that
it's water soluble, and when it's ingested, has a biological half-life of about 70 days.
Of course, tracking the exact extent of radioactive releases from Fukushima post-incident is very
difficult since the mandatory radiation monitoring stations of which there were 24, well 23 of them
were disabled by the tsunami, so it's hard to be sure. So nuclear fission seems like such a good
idea or does it? A little bit about the history and why we need the water and why we put these
plants where we do so we can understand why on earth they would put a nuclear power plant
where they did. So nuclear power, the first plant was actually built for civilian use
was a 5 megawatt reactor at Obninsk in 1954 that was in the Soviet Union at the time.
Now since then many different designs have been tried many different reactors in operation around
the world. There's actually just under 500 nuclear reactors currently in operation and they generate
2731 terawatt hours and the global total generation as of last year was 20,261TWh
for all forms of energy. So that puts nuclear at about 13%
of the world's electricity generation. Of course, some
countries like France, it's the vast majority and the US it's
about one fifth of its electricity is generated from
nuclear. And nuclear is actually in many respects no different
from coal, oil or gas driven electricity generation insofar
as it requires cooling water. The concept is simple enough,
make heat through some heat source, heat that up, some heat
up some highly cleaned water, chemically cleaned water, so as
pure water as you can make it, and then turn that into high
pressure steam. That steam drives a steam turbine, turbine
spins around, drives an alternator, which then generates
electricity. From there, we need to cool that steam down and
pass it back through the heat source again, because you can't
pump steam. So these sorts of plants are called thermoelectric
power plants. And in the United States, for example, 90% of all
electric electricity is generated by a thermoelectric power plant.
And cooling water is a very big part of the selection process
when you're siting a power plant. Now, not enough water and you
have problems ranging from excessive thermal effects on the
local ecology, depriving the local ecosystem of its minimum
water requirements, or simply not being able to cool the plant
at all, and it's not viable. So obvious choices include large
lakes, large rivers, but if you're happy to deal with the corrosive consequences of living with
salt water, then the most obvious choice is actually the ocean. So much so that with nuclear
reactors about one-fifth of them are located on or within five kilometers of the coastline.
Now you see water for their cooling. So when you consider a nuclear reactor site in particular,
there's a long list of additional potential disasters you need to consider. And clearly
for Japan, the two big ones were earthquakes and tsunami, and there can be very little
doubt based on what happened at Fukushima, that whilst TEPCO may have considered both
of them, arguably the earthquake risk was adequately covered, but the tsunami precautions
were perhaps a little bit less well considered.
So what design flaws were present at this plant?
It's quite disturbing when I was doing the research on this, because I do understand to an extent how they reached the conclusions that they did.
But it doesn't make it that much less terrifying to me personally.
The plant was actually constructed on a bluff, and that bluff was originally 35 metres above sea level.
Well, they decided to take 25 meters off of that height.
It may sound crazy, but I'll tell you why.
The license for the plant and basis of design was that it only
had to withstand a 3.1 meter maximum height tsunami.
But that design basis was based on an earthquake that happened
in Chile in 1960 and that resulted in a 3.1 meter wave
halfway across the world at Japan at the current construction location at Fukushima.
Japanese researchers have increasingly found more evidence of sedimentation layers far
inland from that location and they suggest now that large tsunamis of the size seen in
2011 can actually occur approximately once every thousand years in that area.
As more evidence mounts in recent times, there were concerns raised within TEPCO after the
construction about the tsunami risk to the plant.
In 2008, TEPCO performed some computer simulation modelling and they determined the risk to
the plant may have been underestimated after all.
Now NISA is the Nuclear and Industrial Safety Agency in Japan and NISA were first provided
the details of TEPCO's simulation models, interestingly, 4 days before the tsunami struck.
So 3 years after the analysis was performed, they provided it to NISA.
Back to the construction phase.
During construction, TEPCO decided to lower the height of the bluff by 25m.
That made the base plant level at about 10m above sea level, still well above their 3.1m
maximum design height.
The reasons that they quoted for lowering the bluff included to allow the base of the
reactors to be constructed in solid bedrock and that mitigated earthquake damage.
People that are aware of civil engineering and earthquake prone areas understand that
bedrock is an ideal material for you to be placing your structure because bedrock cannot
go through liquefaction when the ground vibrates.
Not going to talk about liquefaction.
But if you were to put a building on sand
what happens under a high vibration situation like an earthquake
is that that sand essentially starts to act like a liquid and anything in it
tends to sink very quickly in fact.
Sand, dirt, it's a problem. But bedrock is solid
as a, well, rock. How about that? Now, it had to be about something else too, didn't it?
The running costs. The seawater pumps needed to lift the water from the sea to
cool the plant. The higher the plant is, the bigger the pumps needed to be, because
they're pumping against a much higher head pressure, and lifting all that
seawater the much larger distance would have much higher long-term operating
costs. Maintenance costs also would be higher for the pump maintenance and it
would just be more expensive as a long-term operating cost. So by lowering
the height you reduce the distance you have to pump the water makes it cheaper.
Now TEPCO's analysis of the tsunami risk determined a 10 meter high seawall
would provide protection for the maximum tsunami assumed by the design basis.
Hmm. The diesel backup generators that were most likely to be required during an earthquake or tsunami event
were located in the basement of the turbine hall and that was only 10 meters above sea level.
Now, putting generators at those lower heights, it certainly makes them cheaper to construct
and it's easier to maintain them if you have to do any work on them.
And you do have to strip these things from time to time and maintain them.
Now most buildings that I've worked on, the overwhelming majority have their backup gennies in the basement or in the ground floor at least.
But there was one building in particular that I remember, they put their gen set on the 9th floor of the building.
It had a day tank, a day diesel fuel day tank on the 9th floor with enough fuel in it to run for, oddly as the name suggests, a day.
where the bulk fuel tank had nothing to run for a week,
and that was in the basement.
But that was their compromise.
At the time, I remember arguing with them
that with the building's additional reinforcing
to handle the mass of the diesel generator,
putting the bulk fuel tank on or near the ninth floor
would have actually finished the job.
The tanker truck could have had a low lift pump,
a more powerful pump to actually pump the fuel
up to the ninth floor
when it was filling up the bulk fuel tank, but they decided not to do that.
Irrespective of that decision, you would have to put a sealed containment
bund around the bulk fuel tank as they had around the day tank,
but it could have been done.
So in an inundation event, if it ever happened, it would then be totally protected and
isolated. That's not what they did.
Ultimately, though, that's not the point.
It's a common practice to put generators at ground level or in the basement.
and it honestly it's pretty stupid. I've always thought that. I don't get it.
Because when you need it in a flooding event, that's not going to work is it?
Same with switchboards for that matter. Anyway, now if you don't raise the height of the gensets,
it's not the end of the world. There's other things you could do. You could put them in a
watertight bund and by bund I mean it's a wall around the outside without a lid on it essentially,
no roof. But then I think to myself a little bit about the Titanic's interlocking doors.
Now how high is high enough to make that wall high enough to stop becoming inundated?
And the next question is if you do put a wall around it you're stifling the cooling. So are
you going to have enough, are you going to have adequate cooling for the generator trapped inside
its little box? What about access and egress when you need maintenance, you need to pull out the
the alternator, you need to pull out sections of the motor for maintenance purposes.
It makes everything like that more difficult and more expensive.
So they didn't do that either.
Now, the seawater low lift pumps were also a big part of this.
The intake and the building for the low lift pumps was set at four meters above sea level,
which was above the maximum tsunami design height.
But these were the only mechanisms available to draw water in from the ocean
and you needed that cooling water. It was your cooling water source.
They could have added a backup system with multiple intake heights from different depths
with a lower speed, smaller size pumps that are just designed to handle post-SCRAM cooling.
The requirements of post-SCRAM cooling are not as great as when you're in full operation because
you're not at full heat load. So you don't need to cool as much water. So you didn't need as
bigger pump. Well they could have done that but they didn't. The other option of
course they could have mounted them higher with a more reinforced structure.
Mind you that would have cost more money. Refer previous comment about the higher
pumps, higher head pressure. So obviously you want to mount them closer.
So, in the aftermath of this incident, in fact in March this year, the Japanese National Police Agency confirmed
as a result of the earthquake, there were 15,893 deaths, 6,152 people were injured, 2,572 people were reported missing.
A staggering number, though, is 228,863 people displaced from their homes either temporarily
or permanently.
A large number of those relate directly to the exclusion zone around Fukushima.
Now, in amongst those figures will be individuals affected by the incident at Fukushima.
Of course, plenty of other people were affected by the tsunami directly.
And this isn't a show about preventing natural disasters, since you can't.
But in engineering, we design and we construct buildings, roads, control systems, electricity
grids, we design all these things to withstand natural disasters of a certain intensity.
If we build something that can't withstand a natural disaster, I want to know why.
the instance being compared to Chernobyl and TEPCO officially stated that the
amount of radioactive material was only about 15% of that released at Chernobyl
but the truth is that this figure is kind of well I'd say highly questionable
because it's very difficult to accurately determine that. Access to
those cores at units 1, 2 & 3 is still not safe and it won't be for many
years to come. It's going to take 30 to 40 years to clean up the fuel and remediate that site.
In the 20 kilometer no-go zone, it remains in place today, and it's four years after the incident,
and it's going to be in place for a very long time. I came across a very eerie set of photos
taken by a brave, maybe, photographer, and some from an aerial drone as recently as a month ago,
and they're both stunning and terrifying at the same time. There's a link in the show notes and
it's called the Fukushima Wasteland. It shows how nature is taking over again. There's abandoned cars
overgrown by weeds on a freeway it looks like, grasses and sidewalks hidden by foliage,
tables that were still set with half-eaten meals on. It's going to be three decades
at least before they could potentially declare the area safe.
And even then, that's not a certainty.
So there's a lot of conflicting
and disagreeing information about
what happened at Fukushima.
A lot of it is because we're not sure how transparent TEPCO has been.
A lot of it is because of misinformation spread on social media.
Spent quite a bit of time trying to get to the truth of exactly what figures and what happened when, and it's quite difficult.
The reality, though, is that no matter how you slice it, they made the wrong choices when they designed the plant.
But it comes back to the design basis.
A 3.1 metre tsunami, to me, sounds insane.
Japan is perhaps one of the most dangerous countries to live in regarding tsunamis and tsunami risk.
And 3.1 meters is not very big in terms of tsunami wave heights. So whilst it was a huge event,
as the evidence mounted in subsequent decades, it wasn't really reassessed seriously until 2008.
and even when it was, they were considering raising it to I think 5.7 meters or thereabouts
was their design basis adjustment for the maximum tsunami height and even if they had
have taken precautions to protect against that it still would not have been enough.
So the problem is when you say in a design basis I wanted to withstand a storm event of
one in 1,000 years or one in 10,000 years events, so something extreme, how do you know if the
the history doesn't go back that far.
Just because you find sediment 2, 5, 10 kilometers, miles inland, that doesn't tell you how big
the tsunami wave was when it hit the coastline.
I mean, computer modelling will help, sure, but you just don't know for sure.
You know it was bad.
You just don't know how bad.
And if you don't know that, how can you be sure you're meeting that requirement?
So what do we do? We fall back on the most recent sample of history, which is only what?
100 and well, when the plant was designed, it was 1967.
It was first constructed, unit one.
And we only had records going, accurate records, going back to 1900 in terms of earthquakes,
related tsunamis and the height measurements.
We just don't have the history.
How do you know it's enough?
History repeats itself, that's only useful if you're measuring history, if you're recording it.
So, nuclear fission, I guess, is most analogous to an enormous explosion
in extremely agonizingly slow motion.
The problem is that once you start that reaction, that fission reaction,
your goal at that point is to slow it down and keep it under control.
Because if you can control it, you can use the heat to make as much electricity as you like.
Problem is, if you screw it up, it doesn't take very long for it to get out of control.
And once it's out of control, bringing it back under control is extremely difficult.
It takes many, many months, in some cases years.
And there are serious consequences if you get it wrong.
We should be reassessing the protective measures as a result of global warming, because those
effects are starting to be felt, especially with rising sea levels, for plants like this.
And there's a lot of them.
In the last two decades, in case you thought that Fukushima was an isolated case, it's
not.
In the last two decades, there have been several other, call them beyond design basis flooding
if you'd like earthquake related some of them at different nuclear power plants around the world
let's go through some of them December 1999 a storm surge caused flooding at two reactors
at the Blayais nuclear power plant in France on December 26 2004 that was the Indian Ocean
tsunami that flooded the seawater pumps at Madras Atomic Power Station in India
On the 16th of July 2007, an earthquake exceeded the design basis of TEPCO's
Kashiwazaki-Kariwa nuclear power station in Niigata Prefecture.
On August the 23rd, 2011, several months after Fukushima, an earthquake on the east coast of
the United States marginally exceeded the design basis of the North Anna nuclear generating station
in Virginia. None of those led to a significant incident. No radioactivity was emitted. Call
them close calls perhaps, or I don't know, cautionary if nothing else. I guess no matter
how many times I go through this in my mind, I'm just not convinced nuclear fission can
ever be risk free. There will always be risks, there will always be things we just cannot
foresee, we can't account for, and we can't protect against. Ultimately the cost of solar
and wind power is coming down every year. And as we step closer to truly solving the
battery problem for storing that power overnight, maybe we can finally stop playing with nuclear
power and pretending that we're in control of it. Because we're not.
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Thanks for listening.
(gentle music)