Yucca Mountain raises a lot of controversy – let’s face it; if it didn’t then a 4-part series of blog postings would hardly be necessary. Part of the reason for the controversy is that there are a number of worries about the impact of spent fuel disposal on the environment and on the health of people living and working in the area and along the transportation routes. So to close this series out I’d like to tackle some of these concerns to see which hold water and which might be over-stated. One good place to find a number of these concerns is a website put together by the State of Nevada in 1998.
Radiation levels from the spent fuel will be dangerously high for millennia
This is true, but not really relevant to the question of safe disposal at Yucca Mountain because no person will ever come in contact with the spent fuel. As I mentioned in the last posting, the spent fuel will be locked away inside of heavy-duty casks that are designed to shield the radiation, reducing it to less than 10 mR/hr at a distance of 2 meters from the cask. As long as the fuel remains inside the casks the fact that the fuel itself is intensely radioactive doesn’t make a difference – nobody can be harmed by radiation to which they’re not exposed. And with regards to the spent fuel remaining inside the casks – remember that the casks are rugged; they’re designed to survive hits from speeding locomotives, and once they’re in place in the ground they’ll not even face that risk. Finally, while the fuel remains radioactive for millennia, the radiation levels fall off fairly quickly over time – after several decades (far less than the design lifetime for the waste site or for the casks) radiation dose rates are down to a fraction of the original levels.
Spent fuel contains intensely toxic plutonium
Also true, but again not as dire as it sounds. Yes – spent fuel contains plutonium because plutonium is created when uranium-238 atoms capture neutrons during nuclear fission. And yes – plutonium is a very toxic heavy metal. But plutonium is hardly the most toxic element known to man – a toxicologist I used to work with could name a dozen substances that are more toxic (including shellfish toxins and fungal toxins). In fact, plutonium was administered to humans to help puzzle out how it acts and moves within the body and those to whom it was administered remained alive and well (and yes, many of these tests would be considered unethical today and they have generated a ton of controversy – but that doesn’t change the fact that the testing did not harm those who were tested).
And let’s think for a moment about what has to happen for the plutonium in the fuel to reach a person who might be harmed by it. Groundwater would have to percolate down through the hundreds of feet of rock to reach the spent fuel containers. Then it would have to penetrate through the casks by corroding the metal and soaking through the concrete layers. Once inside the casks it would have to dissolve the fuel elements – including the highly insoluble plutonium – and would then have to escape again. Finally, it would have to carry the dissolved plutonium through another several hundred feet of rock to the water table and, once there, would have to carry it however many miles to the nearest human with a well sunk into the aquifer. Possible? Yes. Plausible – especially in time measured in millennia? Not really.
Geologic events – earthquakes or volcanic eruptions – can cause the casks to fail, speeding the release of radioactivity to the environment.
Let’s take the easy one first. Yucca Mountain is made of volcanic rocks and there have been volcanic eruptions in the American Southwest within the last several thousand years. So it is plausible to think that there might be more such eruptions in the next few tens of thousands of years. But there are two primary types of eruptions – those with lava and those without. The style of eruption in the American Southwest has historically been ashfalls rather lava – such an eruption would only serve to entomb the spent fuel even more deeply, and the ash itself is too cool to melt the spent fuel casks. Being immersed in lava is more likely to damage the casks, but the lava itself isn’t likely to flow as far as the Las Vegas suburbs. To expose people to elevated levels of radiation the lava would have to immerse the casks long enough to melt them and then continue flowing and carrying the fission products with it – and continue far enough to expose people. There have been lava flows that have covered hundreds of miles, but not within millions of years. So while it is plausible to think that volcanic eruptions might be able to release radioactivity to the environment, the debris or lava are more likely to bury the waste even further than they are to release it to the environment.
Earthquakes are a little more problematic – the concerns here are that an earthquake could open up new fractures, speeding the flow of water from the surface to the casks and from the casks to the water table. Another concern would be that an earthquake could rupture the casks and release radioactivity. Both of these are plausible – we know that earthquakes fracture rock and can disrupt groundwater flows and they can certainly do that in Yucca Mountain. And we know that they can fracture rock, so they can certainly fracture spent fuel casks. So it is plausible to think that an earthquake could cause radionuclides to be released from the spent fuel casks. But we also have to think about the odds that an earthquake will open a fracture that passes through the very rock – the exact part of the rock – that the casks are sitting in. It’s certainly possible, but the odds are against it.
Plutonium might leak out of the canisters and accumulate in a critical mass in the environment and explode
This is one of my favorites. Not only do we have to get the plutonium out of the casks (water leaking into the waste repository, penetrating into the casks, dissolving plutonium, making its way into the environment), but then enough of the plutonium has to precipitate out of solution in the same place – and under the correct conditions – to form a critical mass. And it’s important to understand that a critical mass is not something that will explode but simply something that will sustain a fission chain reaction under the right circumstances. Going through the steps to even get plutonium into the environment is challenging enough and not likely to happen. Precipitating the plutonium out of solution in a critical mass adds to the unlikelihood. And putting together something that could blow up is well-nigh impossible.
Putting all of the spent fuel – which contains plutonium – in one spot makes a tempting target for terrorists and is a proliferation risk
Putting all of the spent fuel in one place certainly increases the amount of plutonium in this one location. On the other hand, we also have to wonder if it’s better to have only one location at risk or the 50+ that exist today. We can make a good argument that it’s easier to guard and make impregnable a single location than to try to secure every reactor facility in the nation.
With regards to non-proliferation, anyone trying to make a nuclear weapon would first have to get to the spent fuel casks and would then have to either steal some very large and heavy casks or would have to open them up at the waste site and remove the fuel from them – actions that would be hampered by high radiation levels anytime in the next several decades. And did I mention getting the spent fuel offsite and out of the country? Then the putative terrorists (or infiltrators from a prospective nuclear power) would have to remove the fuel, chop it up and dissolve it in acid, and chemically process it to remove the plutonium. The bottom line is that no terrorist group has the resources to pull this off, and neither do most nations. So…possible? Well – maybe, from the standpoint that winning the lottery by buying a single ticket is possible. Plausible – nope. This is another one that just doesn’t pan out.
I could go on and on – there have been tons of arguments raised about why spent reactor fuel shouldn’t be disposed of at Yucca Mountain. Some of these arguments – the one about plutonium leaking out, forming a critical mass, and going boom comes to mind – are either deliberately specious or are a sort of worst-case wishful thinking; they will certainly not happen in the real world. Others – the possibility of an earthquake rupturing the spent fuel casks is one – are plausible, but the odds are very much against their happening. But here’s what it comes down to – we will be able to come up with lengthy lists of arguments both for and against putting spent reactor fuel just about anywhere. At some point we have to say one of three things:
- We’re happy with the current situation and are going to stick with it forever,
- We’re going to suck it up and put the waste in a location where our best science tells us it will be safe from any reasonable set of circumstances, or
- We’re going to give up nuclear power and find some other way to produce 20% of our electrical needs.
The bottom line is that the entire nation benefits from the use of nuclear energy – again, 20% of our power is nuclear. There are ample places where the waste from these reactors can be stored with minimum risk to the environment or to people. We may never find a single location that we can certify as being “best” and the nit-pickers among us will always be able to find arguments – however irrational, specious, or ill-informed – that seem to mitigate against any particular site. But at some point the nation will need to find a place that, while perhaps not perfect, is good enough to meet our needs because it meets all reasonable criteria for waste disposal in the real world.
At some point, whether the nation is going to continue using nuclear energy or not, we are going to have to find a spot to put the spent reactor fuel that has accumulated and that is currently being stored across the nation. It makes sense that this location be someplace that is dry and under-populated, that is convenient to major transportation routes, and that is geologically and hydrogeologically suitable for isolating the waste while it is dangerous. These sites exist and Yucca Mountain is one of them. I would suggest that the technical problems of long-term radioactive waste disposal are relatively minor – the natural nuclear reactor at Oklo has shown us that even wet and fractured rock can retain radioactive waste for eons – it is the political problems that have thus far proven insurmountable. But let’s not deceive ourselves – the seemingly scientific objections to Yucca Mountain are pretexts for the underlying political objections. It is politics, not science or engineering that’s holding up our waste disposal solution. And until we can resolve these political problems we will continue to store our waste in a host of vulnerable locations scattered around the US.