the random musings not worthy of new thread thread

[Zanshin]

Watched it on FB yesterday - pretty damned cool. Did you ask Hiatt if the tiki bar was open?

Hiatt would tell you that the only bar he goes to now has lettuce and tomatoes ;-). 

[PhillyPhreak54]

Fell down into the YouTube rabbit hole last night watching videos about the Chernobyl disaster.

QB - I imagine you've read a ton about that. Are reactors still run like that nowadays? I know it was mainly human error but they mentioned design flaws too. Curious as to what those flaws were.

[QB Eagles]

It was a Soviet design with its origins in the 1950s. It works extremely differently than most modern reactors. It used water to cool the core but graphite -- a solid, the same shtein in pencil lead -- to slow down the neutrons and enable fission. Most reactors use water for both roles. Graphite itself can catch on fire, which is not something you want to happen. In the US, I think only early test reactors and reactors used in the nuclear weapons program to produce plutonium used similar materials.

The main flaw from a design perspective was something called a positive void coefficient. Nuclear reactors in general are designed so to have negative feedback to bad events. For example, if the temperature goes up, you want the number of fissions to go down. This will in turn cool the reactor and balance things out, naturally keeping things stable, instead of causing a feedback loop of higher temperatures, more fissions, higher temperatures, more fissions, until things are happening at a speed well beyond human control. It's Nuclear Engineering 101 to have negative coefficients associated with all of these bad events, and how to do it is really well understood science.

Void coefficient refers to what happens when the number of steam bubbles increase. The Chernobyl design generated more fissions when the water was boiling more, and this created a nasty feedback loop of higher levels of boiling and reactions. By itself, that's not so bad -- there are a lot of ways to still control it. But it's just bad fundamental design principles, and in an accident scenario like Chernobyl where some idiots have intentionally disabled a lot of the safety features, it can make all the difference. To have a design like that in use as late as the 1980s is really mind boggling to an American engineer. Nearly all of our reactors since the 60s are pressurized water designs with a void coefficient which is enormously negative.

These days the newest reactors are designed so that natural processes would prevent accidents even if humans do nothing, or do a lot of idiotic things. That's the way to do it. Humans are the worst.

[PhillyPhreak54]

Awesome info. Thanks. I find that stuff fascinating. We lived close to Limerick and since then I've always been interested in reading about nuclear plants.

So with the technology now it really is the safest and cleanest way to go? Where does the waste go?

Those Russians were nuts. Ive read that it's a huge tourist attraction now but I couldn't imagine going there with it still being radioactive.

[hbionic]

There was a special on PBS on nuclear reactors and waste. One woman mentioned they were working on a design that would re-use nuclear waste material. It would be used in the process again. But not sure if that's a thing yet if ever at all.

[PhillyPhreak54]

Was it a Frontline episode?

[phattymatty]

My drug dealer was all destroyed watching some Youtube series called Vietnam in HD the other day, ended up watching with him for 3 hours. Really good if you like that stuff. Can't find it on Netflix or anything, seems to be only on youtube somehow. Apparently they were already filming in HD back then but we just couldn'tt watch it until recently. Amazing footage.

[PhillyPhreak54]

Good tip thanks.

I love history. Ive begun watching The Men Who Killed Kennedy on YouTube and also the 60s and 70s series that cnn did.

[phattymatty]

Tec Cruz's dad killed JFK. Read it today.

[PhillyPhreak54]

Sirhan Sirhan Cruz?!

[QB Eagles]

So with the technology now it really is the safest and cleanest way to go? Where does the waste go?

There's always tradeoffs. The safest power is probably something like wind or solar, but if it's many times more expensive, or requires a much larger environmental imprint, how do you judge that? The energy market is distorted in all kinds of ways. Some forms of energy are held to different environmental standards and regulations, others are subsidized based on who's donating to who. Nuclear is certainly safer and cleaner than fossil fuels. Right now the way the energy markets in the US are set up though, nuclear is barely economically viable. The plants take too long to commission and build, and it's very difficult to get loans to cover the capital costs. Ultimately it's a political question. When plants are being built, it's generally because the political process is pushing them through. When they are being delayed or closed, it's generally because the political process is fighting them.

I don't really believe in an evil technology. If something is unsafe, good engineering can make it safe. Calling a tech inherently unsafe is a luddite argument, IMHO. Nuclear plants don't output carbon or shoot radiation out all over the countryside. Once they are built, they are dirt cheap to operate. They output massive amounts of energy. When you compare the risks to other forms of energy, things actually look pretty good for nuclear. At the end of the day, I am rather agnostic about what forms of energy dominate. If the US went 100% coal or 100% wind through a fair process, I would be okay with it.

The waste is stored on-site in a solid form until it cools (both temperature and radioactivity). It's not truly waste, because most of the fuel is still not used up, but at a certain point (typically every 18 months) it becomes easier and more economically viable to swap it out for fresh fuel, so we consider it spent fuel at that point. It's a ridiculously small amount of waste material compared to something like a coal plant.

In the US, a law was passed in the early 1980s to send all of the waste to Yucca Mountain in Nevada. It's been a political football ever since. The repository never opened, and probably never will be. The location was a political choice to begin with. I am convinced that Yucca Mountain would have been perfectly safe -- it's probably the most scientifically studied piece of land anywhere in the world. It wouldn't have been the MOST safe location, but that would have been somewhere in the granite mountains of the northeast, closer to more congressmen and electoral votes. Everything nuclear is always about politics first and foremost... not science, not the environment, not economics.

[General_Failure]

Sirhan Sirhan Cruz?!

Can you blame him? Every time JFK saw him he'd go "Hey Sirhan, Sirhan. Whatever will be, will be."

[PhillyPhreak54]

So with the technology now it really is the safest and cleanest way to go? Where does the waste go?

There's always tradeoffs. The safest power is probably something like wind or solar, but if it's many times more expensive, or requires a much larger environmental imprint, how do you judge that? The energy market is distorted in all kinds of ways. Some forms of energy are held to different environmental standards and regulations, others are subsidized based on who's donating to who. Nuclear is certainly safer and cleaner than fossil fuels. Right now the way the energy markets in the US are set up though, nuclear is barely economically viable. The plants take too long to commission and build, and it's very difficult to get loans to cover the capital costs. Ultimately it's a political question. When plants are being built, it's generally because the political process is pushing them through. When they are being delayed or closed, it's generally because the political process is fighting them.

I don't really believe in an evil technology. If something is unsafe, good engineering can make it safe. Calling a tech inherently unsafe is a luddite argument, IMHO. Nuclear plants don't output carbon or shoot radiation out all over the countryside. Once they are built, they are dirt cheap to operate. They output massive amounts of energy. When you compare the risks to other forms of energy, things actually look pretty good for nuclear. At the end of the day, I am rather agnostic about what forms of energy dominate. If the US went 100% coal or 100% wind through a fair process, I would be okay with it.

The waste is stored on-site in a solid form until it cools (both temperature and radioactivity). It's not truly waste, because most of the fuel is still not used up, but at a certain point (typically every 18 months) it becomes easier and more economically viable to swap it out for fresh fuel, so we consider it spent fuel at that point. It's a ridiculously small amount of waste material compared to something like a coal plant.

In the US, a law was passed in the early 1980s to send all of the waste to Yucca Mountain in Nevada. It's been a political football ever since. The repository never opened, and probably never will be. The location was a political choice to begin with. I am convinced that Yucca Mountain would have been perfectly safe -- it's probably the most scientifically studied piece of land anywhere in the world. It wouldn't have been the MOST safe location, but that would have been somewhere in the granite mountains of the northeast, closer to more congressmen and electoral votes. Everything nuclear is always about politics first and foremost... not science, not the environment, not economics.

How long does it usually take to cool in radioactivity? And when you buy new fuel is that bought from the govt or are their suppliers for the plutonium and uranium?

[Susquehanna Birder]

My drug dealer was all destroyed watching some Youtube series called Vietnam in HD the other day, ended up watching with him for 3 hours. Really good if you like that stuff. Can't find it on Netflix or anything, seems to be only on youtube somehow. Apparently they were already filming in HD back then but we just couldn'tt watch it until recently. Amazing footage.

Watched one of these today. Really good stuff. Thanks for the info.

[QB Eagles]

How long does it usually take to cool in radioactivity? And when you buy new fuel is that bought from the govt or are their suppliers for the plutonium and uranium?

The very nature of radiation is that the most dangerous stuff decays the fastest, so the worst of the worst is gone in the first few days. It's kind of a judgement call how long to keep it in the pool. I've seen everything from 1 to 20 years. It's mostly for the heat though. The spent fuel will always be somewhat radioactive, just decreasing forever. There are some isotopes that take billions of years to decay. That's the case with natural uranium, and most of the spent fuel is still uranium.

Basically you don't want to stand next to the whole assembly of unshielded fuel for many generations, but if a little bit leaked into the ground or water or something, it probably wouldn't be deadly. Shielding and dilution are big deals.

Uranium enrichment is a commercial business. Like the reactors themselves, the government has access to everything and is heavily involved. The enrichment levels are well below what's needed for weapons. Plutonium is typically not sold as a fuel, it's something that's created during the process. It can be used though. The UK and France reprocess their waste, pull the plutonium out, and use that as fuel. And it's probably the best way to get rid of nuclear weapons... turn them into electricity.