A surprisingly good outreach platform has turned out to be Quora.com, a Q&A site where people ask questions and let anyone answer. So I will be replicating some of my answers from there to here. Enjoy…
Nature showed us how to do it, and it works great!
This is a nuclear waste repository, that held waste for 2 billion years.
Yes, you read that right: 2,000,000,000 years. That is 20,000 times more than what we consider to be adequate for a repository. And the only reason it is not longer than that is because…
a. that is how much time has passed since the waste was created
b. the waste has now decayed, completely. [1]
In the 1970’s, the Uranium ore find at Oklo, Gabon, Africa, gathered attention, because there was something “wrong” with the ore. It was as if the Uranium had already been used in a reactor.
As it turned out, it had indeed been in a reactor, a natural reactor. Billions of years back the isotope mix of Uranium was more like that we use in artificial reactors today. So all it needed was a bit of water to moderate the neutrons and — voilà! — nuclear fission, just like we do it today.
Nuclear fission means nuclear waste. These natural reactors also made waste. That meant a golden opportunity for us to examine what happened to the waste. The conclusion was astounding:
The waste stayed in place and moved less than 10 feet / 3 meters
This is despite the fact that the waste…
- was not packaged in fuel bundles
- was not encapsulated
- was subjected to violent temperature swings (these reactors worked in cycles of a few hours)
- was washed through by water for hundreds of thousands of years
The chief finding was that long-lived waste — the Transuraniums like Plutonium and Americium and other such Actinides — binds chemically to rock in a reducing environment and remains entirely immobile.
This is the key to why geological repositories work. Nature told us so. And that is why we are building repositories that way.
The Swedish KBS-3 method builds on the findings of Oklo and further research since the 1970’s. KBS-3 is already approved in Finland, and is in the process of being approved in Sweden.
KBS-3 — besides using the reducing environment of the bedrock — also adds the following barriers.
- The fuel remains in the fuel rods, i.e. clad in Zirconium alloy. They are then placed in…
- Cast iron holders. The cast iron ensures rigidity, toughness, and that the environment will remain reducing even if water enters the…
- 2 inch / 50 mm thick corrosion resistant copper capsule that encapsulates the fuel bundles and their holder. That capsule is then surrounded by…
- A layer of water absorbent Bentonite clay. The clay acts as soft padding to keep the capsule from being subjected to movements of the bedrock. It is also meant to be wet, because when it wets it swells to a pressure of 50 atmospheres, and is pressed into all the cracks and fissures around…
- The bore hole, made 500 meters down into geologically stable bedrock, with a reducing environment and only small water movement.
The only thing that the Oklo reactors had was the reducing environment, and that alone held the waste in place for 2 billion years. KBS-3 will do the job.
So anyone that says there is no plan or no method or no site to deal with nuclear waste, is speaking — put in the plainest of the Queen’s English — complete and utter bollocks.
Footnotes
[1] The half-life of Plutonium-239 is: \[t_{1/2}= 24,100 y\]
So the tenth-life of Pu-239 is: \[t_{1/10} = t_{1/2} \left(\frac{ln(10)}{ln(2)}\right) \Rightarrow\]
\[t_{1/10} = 24,100 \cdot 3.32 \approx 80,000 y\]So 2 billion years makes for…
\[2,000,000,000 / 80,000 = 25,000\]…25,000 tenth-lives.
After about 110 or so tenth-lives, the original amount would have had to fill out the entirety of the known observable universe in order to have one atom left.
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Say Yes To Fourth Generation Nuclear Power
Published by Michael on November 24, 2010Today’s policies on nuclear energy dictate that we shall put fuel that is unspent – 95 percent of it – in an expensive hole in the ground. There are better ways. Fourth generation nuclear power helps save us from our own foolish plans.
Picture this…
You are on a family car trip. You need gas, so you stop at a station and fill up twenty gallons of fuel in your car. You drive ten-fifteen miles down the road, using up one third of a gallon of gas, and then you stop. To the puzzlement of your family you siphon all of the unused gas out of the tank. Two thirds of a gallon you pour out on the road and set fire to. The remaining nineteen gallons you give back to a gas station. Your family asks you: “Why are you doing that?!”. You reply to them: “Oh that gas will be sent back to the oil well and put it into the ground again, not to be used”
By now your family will call for an ambulance and have you committed on grounds of insanity, because such behavior is without doubt utterly ludicrous.
But what if I told you that this is how most counties in the world are managing their stock of nuclear fuel, including the US?
In the middle 1980’s most of the nuclear power plants that are in operation in the world today had been built. They are of the so called second generation nuclear power. After thirty years in operation the results from these plants are quite excellent. Apart from Three Mile Island (TMI) accident – which incidentally didn’t hurt anyone – none of the pressure and boiler water reactors of West or East Asia have had a major accident. They are sturdy and reliable designs.
They do have a few drawbacks though:
Today tens of thousands of tons of spent nuclear fuel are sitting in casks or storage pools around the world, waiting for us to come up with a solution for it. For countries that do not allow reprocessing, there has only been one solution seriously proposed so far: deep geological repositories. You build caves deep into stable bedrock, and stuff the nuclear fuel there. Seen from a safety perspective that is a good idea because we know from the natural nuclear reactor site in Oklo, Gabon, Africa, that such repositories are extremely safe. A geological repository will keep spent nuclear fuel locked inside for literally billions of years. The only major worry is human intrusion.
Seen from a resource and sustainable development standpoint though, this is an awful(!) idea. 95 percent of the energy in spent nuclear fuel is unused. Why would we want to put that in the ground for hundreds of thousands of years when we can use it to get clean, safe energy instead?
Fourth generation nuclear power is an umbrella term for emerging reactors designs. Some of them have existed as experimental plants for decades. Countries like the U.S., Russia, France and India have been working on fourth generation for quite some time. The advantages of this new nuclear power are substantial:
Two things have held fourth generation nuclear power back so far. First the negative attitudes towards nuclear power after TMI and Chernobyl. The second factor has been the fact that Uranium has been – and still is – dirt cheap considering the fantastic amounts of energy that is extracted from the material, even with the second generation reactors.
While countries like the US and Sweden are mulling over how to get people to accept nuclear waste dumps in their neighborhoods, others – like Russia and South Korea – are moving forward aggressively in the field of new nuclear power. With the current rate of expansion China will be the world leader in a couple of decades; the country is breaking ground for ten(!) new nuclear reactors every year.
Until fusion power is commercially available, the question is what role the western world will take in the continuing history of nuclear power. Will we:
If the first option sounds good to you, I urge you to get a siphon and start draining your gas tank…
Michael Karnerfors, Lund, Sweden
The author is a Master of Science in Computer Science and Engineering, and co-founder of the independent network Nuclear Power Yes Please” (NPYP) which seeks to gather people who consider the issue of nuclear power too important to be squandered with junk arguments and outrageous claims aimed more to scare and terrify people rather than informing them on the issues for and against nuclear power. 2 Comments