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Ultra Safe Nuclear

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Re: Ultra Safe Nuclear

#201

Post by SiempreViernes »

shireboy wrote: post #68
grawprog wrote: post #8

So why has nuclear waste become a thing that's not mentioned anymore? It was a pretty big thing in the 90's, now it seems to get brushed under the rug for all this 'safe' nuclear power marketing. It's mot just meltdowns and containment breaches that are a problem with nuclear power. None of the renewable alternatives produce radioactive waste that needs to be stored and dealt with. https://en.m.wikipedia.org/wiki/Rad…

Counterpoint: why is environmental impact of solar+batteries often not mentioned? Lithium, silicon tetrachloride, hydrochloric and hydrofluoric acid isn't exactly nice to produce or put into rivers. My 2c: have an "all of the above" approach towards research, dispassionately understand pros and cons and big-picture complexity, instead of retreating to tribes that ignore the complexity.

Well, you skip all the same nasty metals needed for the reactor vessels and support equipment too, so it's an even trade?

Re: Ultra Safe Nuclear

#202

Post by PaulHoule »

hairytrog wrote: post #189
simonebrunozzi wrote: post #179

Earlier quoted context omitted.

> which you can't really do because of Xenon poisoning Can you clarify this part? You mean that channging the power level of the reactor would cause Xenon poisoning?

I highly recommend HBO's Chernobyl. Explains a lot this stuff. Basically, as a nuclear reactor operates, it is turning the Uranium into lots of other stuff. One component of this other stuff is Xenon-135, which absorbs neutrons and basically gets in the way of nuclear reactions. This is not an issue if you keep the reactor on because there are enough neutrons to keep things going and overcome the Xenon absorption. Bu…

When a reactor is "poisoned" with Xenon, the Xenon absorbs a large fraction of neutrons that otherwise would cause fission.

If you don't want to wait for the Xenon to decay you could construct a reactor that has a larger control swing than you would need otherwise -- for instance you could put in more and denser control rods. In that case, however, you need to have a lot of "excess reactivity" and also a lot of neutrons lost in the control rods under normal use, which in turn means the "neutron efficiency" is worse. (If you're not planning to breed Pu239 or U233 maybe you don't care)

Note the Xenon concentration can vary in different parts of the reactor so you have to manage the "oscillations" in space just as you do in time. Not a catastrophe, but definitely a hassle.

Re: Ultra Safe Nuclear

#203

Post by cbmuser »

hairytrog wrote: post #158

Seems like their claim to "Ultra Safe" is actually merited based on a first principles look at the power density. They claim 1.24 W/cm^3 versus 20-40 W/cm^3 in normal reactors. The high power densities mean you have to be able to cool the reactor, even when you shut down the reactor because reactors take a long time to actually turn off. With such low power density, it should be no problem to cool down the reactor. I…

There are reactor types like the Integral Fast Reactor that will safely shut itself down even if the cooling systems fail.

In fact, the engineers at Argonne deliberately tried to overheat the reactor by shutting off its pumps and they failed.

Re: Ultra Safe Nuclear

#204

Post by colinmhayes »

colonwqbang wrote: post #137
Pfhreak wrote: post #129

Earlier quoted context omitted.

Wait, we're better than this on HN. If you have concerns about an argument being made it's important to articulate the concerns. Pointing out someone's career/reputation is an appeal to authority, and a form of bias. It's possible that a comedian could be well informed from a staff, for instance, doing research. I am not familiar with John's arguments, but I wanted to address that dismissing him out of hand seems per…

But no arguments were cited in the comment, there was only a John Oliver name drop.

No. The comment pointed out an argument against nuclear and asked for a counter-argument.

Re: Ultra Safe Nuclear

#205

Post by cbmuser »

grawprog wrote: post #8

So why has nuclear waste become a thing that's not mentioned anymore? It was a pretty big thing in the 90's, now it seems to get brushed under the rug for all this 'safe' nuclear power marketing. It's mot just meltdowns and containment breaches that are a problem with nuclear power. None of the renewable alternatives produce radioactive waste that needs to be stored and dealt with. https://en.m.wikipedia.org/wiki/Rad…

Because it’s not a problem:

> https://www.energy.gov/ne/articles/5-fast-facts-about-spent-...

It’s the best waste we have due to being solid and extremely compact and it can be recycled by 95%:

> https://www.anl.gov/article/nuclear-fuel-recycling-could-off...

Re: Ultra Safe Nuclear

#206

Post by obelos »

Symmetry wrote: post #157
manfredo wrote: post #75

Earlier quoted context omitted.

> I keep seeing justifications like that and it makes me want to puke. First of all: The total number of victims is unknown and it is still rising. Even for Chernobyl. The total number of victims was unknown for Chernobyl. We didn't know what the impact on cancer rates would be. But it isn't the 1980s anymore. We can compare the rates of cancer and other radiation related illnesses among the people who experienced Ch…

A number of people did die because of the Fukushima evacuation, though, through things like interruption of medical care. And if there hand't been an evacuation there would have been a few radiation deaths. The total is still only 10x the number of air pollution deaths you'd expect from a coal plant providing the same number of megawatt-years and very few nuclear plants melt down but lets be accurate.

How does one disentangle interruption of medical care due to nuclear emergency from interruption of medical care due to tsunami?

Re: Ultra Safe Nuclear

#207

Post by PaulHoule »

manfredo wrote: post #17
grawprog wrote: post #8

So why has nuclear waste become a thing that's not mentioned anymore? It was a pretty big thing in the 90's, now it seems to get brushed under the rug for all this 'safe' nuclear power marketing. It's mot just meltdowns and containment breaches that are a problem with nuclear power. None of the renewable alternatives produce radioactive waste that needs to be stored and dealt with. https://en.m.wikipedia.org/wiki/Rad…

Because it's not a problem. There's actually very little of it. It occupies a volume the footprint of a football field and 10 yards high [1]. Storing it is pretty foolproof: bury it in an area with no aquifer. The main risk of contamination is getting into the groundwater. If there's no groundwater the risk of contamination is eliminated even if the containers decay over time. And lastly, it doesn't make sense to bur…

The main problem with "nuclear waste" is that it is not waste at all.

If it is sufficiently concentrated in Pu238, then people might want to steal it to make bombs with.

Current LWR(s) use about 1% of the energy in the fuel.

Burying the waste in Yucca Mountain is like buying a gallon of gas, filling your car with a thimble, then carefully trying to store the rest of the gas so it doesn't ever get burned up.

The one reason we were going ahead with Yucca Mountain was a matter of "cutting off our nose to spite our face." That is, if we recycled nuclear fuel, somebody might use the recycling plant to make materials for nuclear weapons. If it wasn't for that policy of kneecapping nobody would have once suggested that we bury perfectly usable nuclear fuel.

People are slowly waking up to notion that burning carbon is slow motion suicide, so maybe policies will change.

Re: Ultra Safe Nuclear

#208

Post by dongobongo »

cbmuser wrote: post #203
hairytrog wrote: post #158

Seems like their claim to "Ultra Safe" is actually merited based on a first principles look at the power density. They claim 1.24 W/cm^3 versus 20-40 W/cm^3 in normal reactors. The high power densities mean you have to be able to cool the reactor, even when you shut down the reactor because reactors take a long time to actually turn off. With such low power density, it should be no problem to cool down the reactor. I…

There are reactor types like the Integral Fast Reactor that will safely shut itself down even if the cooling systems fail. In fact, the engineers at Argonne deliberately tried to overheat the reactor by shutting off its pumps and they failed.

But they don’t lose the liquid coolant - which seems like a pretty reasonable scenario.

Re: Ultra Safe Nuclear

#209

Post by sbierwagen »

simonebrunozzi wrote: post #179
hairytrog wrote: post #156

Two interesting things to see here, of many. They are really planning the sites to be temporary compared to the solar/wind/ and other industrial power plants that have little or no plan for returning their sites to the original virgin soil. And two, they seem to use a molten salt loop like in concentrated solar to meet variable demand without changing the power level of the reactor, which you can't really do because…

> which you can't really do because of Xenon poisoning Can you clarify this part? You mean that channging the power level of the reactor would cause Xenon poisoning?

https://en.wikipedia.org/wiki/Iodine_pit

Re: Ultra Safe Nuclear

#210

Post by cbmuser »

lmilcin wrote: post #155
manfredo wrote: post #17

Earlier quoted context omitted.

Because it's not a problem. There's actually very little of it. It occupies a volume the footprint of a football field and 10 yards high [1]. Storing it is pretty foolproof: bury it in an area with no aquifer. The main risk of contamination is getting into the groundwater. If there's no groundwater the risk of contamination is eliminated even if the containers decay over time. And lastly, it doesn't make sense to bur…

Yeah, exactly. Even though it is costly to deal with, per kilogram, there is very little of it when compared to amount of energy produced. An atomic plant might use couple dozen tonnes of fuel which is peanuts compared to the amount of waste from coal power plant. There are no technical problems with storage that we can't solve. The biggest problem is that nobody wants it around.

Even without considering the amount of energy produced, it’s nothing.

The US has accumulated 83.000 tons in decades. Compare that to the billions of tons CO2 that coal plants blow into the atmosphere.

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