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Ultra Safe Nuclear

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Re: Ultra Safe Nuclear

#411

Post by jabl »

johnisgood wrote: post #380
godelski wrote: post #308

Earlier quoted context omitted.

> So why has nuclear waste become a thing that's not mentioned anymore? - It still is the number 1 talking point. - It is a solved problem (you put it in a hole). - The "problem" is vastly overstated. We're talking about 60 years of waste can sit on a football field 1.5m high. That's tiny. Bringing up (generically) waste on a technical forum is often associated with not knowing much about the subject. - Economics is…

Yup, thorium-based nuclear power does not generate much nuclear waste at all, for example, and nuclear waste can be recycled, called "nuclear recycling"[1]. Nuclear waste is NOT an issue. [1] https://whatisnuclear.com/recycling.html

The thorium fuel cycle produces about the same amount of waste as the equivalent U-Pu cycle. Both are breeding cycles requiring reprocessing. There is nothing magical in Th that gets rid of the waste.

The Th cycle can't really be compared to the once-through enriched uranium cycle, as Th doesn't contain any fissile isotope by itself. It requires breeding and reprocessing.

Re: Ultra Safe Nuclear

#412

Post by jabl »

pfdietz wrote: post #339
cbmuser wrote: post #205

Earlier quoted context omitted.

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...

Nuclear waste is not a problem, but not because it can be recycled. Reprocessing is an economic loser compared to just mining fresh uranium. The separated plutonium has negative value, and in thermal reactors much of it can't be destroyed before going into final disposal.

Indeed, reprocessing with PUREX and only using thermal reactors will most likely never make any economic sense.

Breeder reactors and more economic and proliferation-resistant reprocessing technologies like pyroprocessing might, however. Too early to tell really, as neither have really been developed to the point where one can make precise economic predictions.

Re: Ultra Safe Nuclear

#413

Post by evgen »

selectodude wrote: post #294
evgen wrote: post #144

Earlier quoted context omitted.

Out of curiosity, is there a single death that is directly attributable to nuclear waste from a reactor? (want to add that last clause because I do not think nukes should get blamed for someone improperly dumping medical equipment with cobalt or cesium isotope generators) For some reason I want to assume this happened at some point, maybe back in the 50s or 60s when we were really sloppy with nuclear waste but I can'…

https://en.wikipedia.org/wiki/Goiânia_accident That's the one you're thinking of. Brazil, 1987.

Yeah, that was the one that made me add the medical waste clause in my question. There have been a couple of cases of poor handling of these devices, but as far as I can tell there do not seem to be any deaths from actual reactor waste.

Re: Ultra Safe Nuclear

#414

Post by jabl »

tyho wrote: post #15

The walk away passive safety is a tradeoff with non-proliferation concerns. This design requires 20% enrichment, much higher than traditional reactors. This might be a smart tradeoff, but let's not pretend it's doesn't exist. https://www.aps.org/units/fps/newsletters/201810/reactors.cf...

We could start with taking anything said by Ed Lyman with a huge grain of salt, considering he's made an entire career out of concern-trolling anything related to nuclear power.

In this case, his argument is basically that HALEU is a proliferation risk because given access to enrichment facilities, it's more effort to produce weapons-usable HEU starting from HALEU than from LEU or natural uranium. Well, duh! As he himself admits in that letter, it's only a modest factor of three difference for HALEU vs LEU. From a non-proliferation perspective, the critical thing is the access to enrichment technology in the first place!

If one wants to make a case against HALEU, compare the economics vs. LEU.

Re: Ultra Safe Nuclear

#415

Post by jabl »

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…

It has low power density because it's a gas cooled reactor. Gas is a much worse heat conductor than a liquid.

I'm slightly skeptical wrt gas cooled reactors. Due to the low power density, the reactor needs to be physically big. And since the gas is under high pressure, the reactor needs to be a pressure vessel. Big pressure vessel usually means expensive.

One intriguing development is to use the TRISO kind of fuel that Ultra Safe has developed, but instead use molten salt as the coolant. That allows much higher power density, and doesn't need to be pressurized either as the operating temperature is well below the boiling point of the salt at atmospheric pressure. It also avoids the problem of having the fuel and highly radioactive and corrosive fission products dissolved in the salt, as molten salt reactors usually have.

Re: Ultra Safe Nuclear

#416

Post by jabl »

dongobongo wrote: post #208
cbmuser wrote: post #203

Earlier quoted context omitted.

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.

Especially considering the IFR (and it's predecessor EBR II where the experiment the parent refers to was done) are pool type reactors, meaning the reactor sits in a big pool filled with the primary coolant, there are no pipes where the primary coolant leaves the tank.

Re: Ultra Safe Nuclear

#417

Post by jabl »

bl0b wrote: post #290

Random renewable energy-related question that I've been thinking about: Specifically wrt solar, a big argument against is that it can't provide power during the night and we don't have a good way to store energy. What I'm wondering is why it's so imperative that residential/commercial properties are able to get full power from the grid 24/7? What if prices for power go way up during the night (because it can't come f…

In many parts of the world there are so-called deregulated electricity markets, where a market operator takes bids for producers and the marginal price then determines the wholesale price for that time period (usually the period being something between 15 minutes and 1 hour). So yes, if the marginal unit that sets the wholesale price is a low marginal cost producer like wind, solar or nuclear, the wholesale price for that period will be very low. Conversely, if demand is very high and the marginal producer is a peaker gas plant, the price will be very high.

This is basically the business model behind grid batteries as well. Buy power and charge the batteries when power is cheap, sell the power when it's expensive.

One big problem here is that despite wholesale markets working like this for a long time, customer uptake of electricity contracts with time-varying prices tied to the wholesale price has been very poor. In general it seems most customers rather pay a higher fixed electricity price than check the current price before starting their laundry (or something else that takes a decent amount of power).

Re: Ultra Safe Nuclear

#418

Post by Vecr »

croutonwagon wrote: post #340
scoopertrooper wrote: post #282

Earlier quoted context omitted.

It's pretty crazy to assume that we wouldn't be around in a millennia, two, or three. No other civilisation has been truly global, no other civilization has achieved so much in terms of mastery of nature and technological advancement. So unless the carrying capacity of earth suddenly collapses to the point that it's impossible to maintain organised society for several hundred years, then I think we'll be alright. If…

Well. We also have the capacity to destroy all life on earth many times over. When the carrying capacity of earth does collapse it will likely be sudden. Food insecurity will do it quick. We are only like 6 meals away from total chaos at the best of times.

Many times over? I doubt it, if you are talking about nuclear weapons.

There's no way we could punch through all the ice at the poles to get any microscopic life that might live under there, and in a standard nuclear war nothing would touch them anyway. Nuclear winter (if that's still thought to happen in a likely scenario) might not even get all the surface life.

Re: Ultra Safe Nuclear

#419

Post by jabl »

GuB-42 wrote: post #253
redm wrote: post #5

Earlier quoted context omitted.

1) I don't think its a zero sum game, nuclear doesn't preclude solar or wind. In-fact, thats how it's working now. Competition will drive improvements and optimization. 2) Accidents do happen with technology and the repercussions of nuclear accidents are serious. That doesn't mean we shouldn't re-think the technology and how it can be applied in a better or safer way, including cold fusion.

> I don't think its a zero sum game, nuclear doesn't preclude solar or wind. That's what I'd like to think, but it doesn't seem to be a good match. Nuclear plants want constant power output, they are ideal for base load. Solar and wind production vary during the day, and they don't always meet demand. That problem is called the "duck curve": too much is produced during the day and too little just after sunset. That's…

> Nuclear plants want constant power output, they are ideal for base load. Solar and wind production vary during the day, and they don't always meet demand. That problem is called the "duck curve": too much is produced during the day and too little just after sunset. That's the reason why the best plants to complement solar and wind are those that can vary their output on demand. And unfortunately, that's typically coal (see Germany). Hydro would be ideal but its capacity depends is limited by the terrain.

Modeling suggests there is a place for nuclear, or more generally, dispatchable (firm) low-carbon resources in deep decarbonized electricity grids. See e.g. https://doi.org/10.1016/j.joule.2018.08.006

As for the duck curve, you can flatten it with solar panels that are angled to the south-west rather than straight to the south, and some moderate amount of battery storage. That still leaves the problem of how to deal with the baseload. Nuclear could be a good candidate for that.

Re: Ultra Safe Nuclear

#420

Post by imtringued »

bananabreakfast wrote: post #358
marcosdumay wrote: post #355

Earlier quoted context omitted.

At least until somebody gets a design that isn't basically a coal power plant using different fuel, nuclear can not get cheaper than coal. And guess what is being mass decommissioned right now because it's too expensive?

What an absurd thing to say. Nuclear fuel is several orders of magnitude more energy dense than coal. A "coal power plant using different fuel" would produce energy so cheap it couldn't be metered.

No, he's right. Nuclear plants are still just conventional thermal power plants. They "burn" stuff to generate heat and use the heat to drive a turbine. They can't be cheaper because burning coal doesn't have ultra high demands on how the boiler is designed. Meanwhile nuclear reactors can be arbitrarily complex.
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