[HN Gopher] Triso particles have safety features that may power ...
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Triso particles have safety features that may power a new
generation of reactors
Author : wscott
Score : 71 points
Date : 2020-07-03 19:57 UTC (3 hours ago)
(HTM) web link (www.wired.com)
(TXT) w3m dump (www.wired.com)
| pjscott wrote:
| Because the article isn't clear: no, this isn't about pebble bed
| reactors. This is about a type of fuel where a little bit of
| uranium has been encased in a number of protective layers, such
| that the fuel will remain safely contained in its tiny packaging
| even at very high temperatures. You take a bunch of these poppy-
| seed-sized things and embed them in graphite rods or pellets,
| which both keeps them in place and acts as a moderator for the
| reaction. These can then be used in a variety of reactors,
| including (but not limited to) pebble bed reactors.
| oxymoron wrote:
| The confusing part about the article was that it initially
| stated that they were very small, and then went on to speak
| about billiard ball size. Does that mean that the protective
| coating is very thick, or that there's a range of sizes for the
| actual uranium mass?
|
| I remember reading in one of Feyman's biographies about how he
| visited an early fuel plant, and was horrified to see them
| storing what amounted to a near a critical mass in barrels, in
| long rows. we've come some way since.
| pjscott wrote:
| The TRISO fuel particles are very small -- about a millimeter
| or so in diameter. The "billiard ball sized" fuel pebbles
| designed for the Xe-100 reactor are graphite balls with a
| bunch of TRISO fuel particles embedded in them.
| nordsieck wrote:
| One thing that' slightly worrying:
|
| > But during the INL tests, Demkowicz demonstrated that triso
| could withstand reactor temperatures over 3,200 degrees
| Fahrenheit.
|
| > ...
|
| > Sell says. "It is physically impossible--as in, against the
| laws of physics--for triso to melt in a reactor,"
|
| 3200 F = 1760 C
|
| > The first phase lasted only several seconds, with temperatures
| locally exceeding 2,600 degC, when a zirconium-uranium-oxide melt
| formed from no more than 30% of the core.[1]
|
| It seems like it's yet to be demonstrated that Triso fuel can
| withstand the highest recorded temperature inside a nuclear
| reactor. I get that the physically impossible quote is probably
| partially puffery, but IMO puffery is not appropriate when it
| comes to nuclear reactors.
|
| ___
|
| 1.
| https://en.wikipedia.org/wiki/Corium_(nuclear_reactor)#Chern...
| VBprogrammer wrote:
| I went through a phase of reading about nuclear power and in
| particular the nuclear accidents. It feels like we kinda got to
| the Comet1 stage of Nuclear power and gave up. We still learn
| lessons from each accident, for example Fukushima has resulted in
| Passive auto recombiners being installed which convert hydrogen
| back to water. It also added provisions for using mobile
| generation and cooling (fire trucks).
|
| I certainly don't have the answer but to how we can make nuclear
| power fool proof but I do feel like we should still be asking the
| question.
|
| [1] https://en.m.wikipedia.org/wiki/De_Havilland_Comet
| Xylakant wrote:
| > We still learn lessons from each accident, for example
| Fukushima has resulted in Passive auto recombiners being
| installed which convert hydrogen back to water.
|
| Seems we are on a global level not very much learning from
| incidents. These are common (mandatory?) in Germany and
| colloquially named "Topfer-Kerze" after the minister who had
| them installed:
| https://de.m.wikipedia.org/wiki/Reaktorsicherheit#T%C3%B6pfe...
| Klaus Topfer was responsible for nuclear security from
| 1987-1994. This would have been the time to learn.
| corty wrote:
| Use of passive auto recombiners (PARs) started over 30 years
| ago on a large scale and has been state of the art for more
| than two decades now:
| https://inis.iaea.org/collection/NCLCollectionStore/_Public/...
|
| However, many operators didn't want to spend the money, which
| is why Fukushima didn't have a PAR at the time of the accident.
| The problem with Fukushima is that I fear we do not learn from
| accidents. Otherwise, Fukushima wouldn't even have been in
| operation at the time of the accident as it is an old reactor
| model well past its design life. The location was, as we have
| known before the accident, poorly chosen. Safety measures, such
| as PARs, seawalls and properly redundant power supplies were
| skipped or badly implemented due to the cost involved. All this
| was known before the accident, however neither the operator nor
| the national oversight took any action before it was too late.
| pdonis wrote:
| The article is conflating two very different kinds of "meltdown".
| A meltdown during actual reactor operation is the kind the
| article is talking about in the first paragraph, and the kind
| that the type of reactor discussed in the article is designed to
| make impossible, according to the rest of the article.
|
| But the meltdown at Fukushima was caused by lack of decay heat
| removal after shutdown, which is different from what could or
| could not happen during actual reactor operation. So there are
| _two_ kinds of "prevent meltdown" that are required, not one.
| The article does not talk at all about how, or whether, the type
| of reactor it discusses would prevent a meltdown of the second
| kind, the kind that happened at Fukushima.
| VBprogrammer wrote:
| They are designed to be operated at much higher temperatures
| because the use gas as a coolant where they can effectively use
| natural convection to remove decay heat.
| pjscott wrote:
| The article is (confusingly, and a bit confusedly) discussing a
| type of fuel, not a reactor design. The type of fuel in
| question can withstand very high temperatures, whether from
| fission or from decay products, without letting the fuel out of
| its little protective shells.
| joncrane wrote:
| So apparently Fukishima's power failed and the generators were
| damaged by the tsumami.
|
| Why can't nuclear reactors at least have the option to power
| themselves?
| acidburnNSA wrote:
| They have to shut down during the earthquake to ensure they
| maintain coolable geometries. Cooling is easier at lower
| power.
|
| Some Fukushima reactors did have some self-powered safety
| features, like a little steam turbine that comes from the
| boiling coolant and is hooked to a coolant pump. These
| features are at least a little related to why some reactors
| failed at different times than others in Fukushima.
|
| But seriously, there is enough decay heat to do more of this
| so it's a pretty good point.
| sbierwagen wrote:
| Fort St. Vrain ran the reactor cooling pumps off of process
| steam, but had lots of problems with steam leaking through
| the bearings and contaminating the coolant. Electric pumps
| don't have that problem.
|
| https://en.wikipedia.org/wiki/Fort_St._Vrain_Generating_Stat.
| ..
|
| Running some kind of heat engine off decay heat should be
| possible, but it would be very different from the primary
| turbines, (You probably couldn't use it during normal
| operating temperatures, but it'd still have to be connected
| to the coolant circuit) have to be nuclear rated,
| (expensive!) and only be used in an accident scenario where
| you lose external power and the diesel generators are then
| destroyed, or run out of fuel.
| jabl wrote:
| Normally they do, but when you shut it down you need
| something to get rid of the decay heat. That's why nuclear
| power plants have these emergency generators. Those failed at
| Fukushima, leading to the meltdown.
|
| Some newer designs opt for passive decay heat removal, eg
| through convection.
| im3w1l wrote:
| Wouldn't convection also be impacted if the plant is
| flooded?
| nordsieck wrote:
| > the meltdown at Fukushima was caused by lack of decay heat
| removal after shutdown
|
| This was also the problem at three mile island.
| acidburnNSA wrote:
| In probabilistic risk assessments, almost all pathways that
| lead to radiological release in modern reactors is related to
| decay heat cooling failures.
|
| That's the singular safety selling point of Gen IV reactors
| that have passive cooling features.
|
| It was demonstrated in April, 1986 at EBR-II in Idaho, weeks
| before Chernobyl. Very few people have heard of this awesome
| capability.
|
| https://en.wikipedia.org/wiki/Experimental_Breeder_Reactor_I.
| ..
| peachy_no_pie wrote:
| Can anyone speak to the implications for this type of Triso fuel
| and radioactive waste? Is there less radioactive waste once it is
| spent or how similar is it to other types of nuclear fuel in that
| regard?
| pjscott wrote:
| It should produce amounts of waste similar to other once-
| through uranium fuel cycles, e.g. most reactors in use today.
| jabl wrote:
| It ought to be safer since the fission products are encased in
| the protective and non-corroding triso structure. That being
| said, used LWR fuel rods are also enclosed in protective
| cylinders (see eg the designs for the Finnish Onkalo storage
| site). Both safe enough per current best knowledge.
|
| If one wants to do some fancier recycling and reprocessing
| rather than once through, I understand this is relatively
| undeveloped.
| LatteLazy wrote:
| All the major incidents with nuclear power are despite dozens of
| safety systems, redundancies, clever designs etc.
|
| This is because nuclear power is tightly coupled and complex.
| Humans have never mastered such systems. We have them and we
| accept they fail sometimes (eg fires at conventional power
| plants: 200 plus years of engineering and they still happen). But
| with nuclear that isn't an option.
|
| This is why people are unconvinced by clever new fuels or "it's
| totally guaranteed this time" engineering. You can't fix a
| systems/human nature problem with new fuel cells.
| nine_k wrote:
| France is choke-full of nuclear power plants. Can you remember
| a major nuclear power incident in last, say, 30 years?
|
| I think that reactor standardization really paid off there.
| They have few types, a wide operation experience, and
| apparently well thought-out procedures.
|
| This, of course, is hard to achieve without a massive rollout
| planned ahead.
| sradman wrote:
| > nuclear power is tightly coupled and complex
|
| Sounds like you have read Charles Perrow's 1984 book _Normal
| Accidents_ [1]. New fuel systems are actually key to safe
| design, IMHO. All the major nuclear power incidents, that I 'm
| aware of, are due to one underlying problem: zirconium clad
| fuel rods produce large amounts of hydrogen during loss of
| coolant accidents (LOCA). Nuclear power plants weren't supposed
| to go BOOM but it turns out they do so readily with hydrogen
| explosions.
|
| Even with zirconium clad fuel rods, the CANDU reactor design
| seems to have managed the complexity and tight-coupling issues
| surrounding nuclear power generation; the design, however,
| never managed to reduce the immense capital costs involved.
|
| Price-per-Performance is all that matters and in an age of
| cheap natural gas. I'm not convinced that new nuclear reactor
| designs will find anything other than niche markets. There are
| many lessons to learn from Charles Perrow but complete distrust
| of engineering should not be one of them.
|
| [1] https://en.wikipedia.org/wiki/Normal_Accidents
| acidburnNSA wrote:
| TRISO fuel has some very interesting capabilities as noted in the
| article. It also has some challenges. Traditionally, the
| challenges are:
|
| * Very low power density requiring absolutely massive reactor
| vessels for a certain power level
|
| * Very expensive fuel fabrication ($10k/kg), hopefully can be
| brought down
|
| * Difficult to reprocess (this is probably fine until nuclear
| produces like 50% of the world's energy, at which we will begin
| to challenge the fuel resources)
|
| Also traditionally, these are high temperature gas-cooled
| reactors. A new twist is the molten-salt cooled (basically just
| melted salt, not fluid fuel like in full-on molten salt reactors)
| TRISO-fueled reactors. These are called FHRs.
| jabl wrote:
| The FHRs seem like a nice combination of the safety of Triso
| fuel and the higher power density and low pressure of MSRs.
| Wonder why they haven't been studied more..
| acidburnNSA wrote:
| It is a pretty new reactor idea, and has lots of benefits. It
| was popularized recently by MIT Professor (formerly of ORNL)
| Charles Forsberg. Here's a full presentation showing the case
| from 2012 [1].
|
| [1] https://whatisnuclear.com/assets/FHR_Project_Presentation
| _Ja...
| sparker72678 wrote:
| Is this the same thing as "pebble bed" reactors I read about many
| years ago?
| jabl wrote:
| Yes, and no. Most(?) pebble bed reactors have used triso style
| fuel (there was a similar earlier fuel type called biso, don't
| know if any reactors using it were ever built), but triso fuel
| can be used in other reactor types as well.
|
| And yes, triso is pretty cool tech. Like the article says, it
| can withstand exceptional temperatures without any fission
| products escaping.
| verandaguy wrote:
| Yes, this is about pebble bed reactors. From the article:
| The Xe-100 is a small pebble-bed reactor that is designed to
| produce just 75 megawatts of power.
|
| I should add that I'm _thrilled_ steps are being made to make
| these a reality.
| api wrote:
| Seems like the pebbles are much smaller in these. I recall
| one very mundane but difficult issue with previous pebble bed
| reactors was pebbles jamming and other mechanical problems
| with the fuel. These seem like they'd flow like that weird
| pseudo-sand stuff in kids toys.
| pjscott wrote:
| These very small fuel particles are embedded in larger
| graphite structures with whatever geometry is convenient
| for handling. (Pebble bed pebbles are one such possibility,
| and PBRs have been made which use TRISO-based fuel
| pebbles.)
| tersers wrote:
| I also believe it's true of liquid fluoride thorium reactors:
| https://en.wikipedia.org/wiki/Liquid_fluoride_thorium_reacto...
|
| I remember watching a documentary on nuclear power in the US
| and how the thorium reactor was the focus of a lot of research
| in the 70s, but I can't remember for sure.
| pjscott wrote:
| To clarify: molten fueled reactors (like LFTRs) trivially
| can't have their fuel accidentally melt, because their fuel
| is already molten. (And there are some nice options for
| dumping their fuel into a subcritical passively-cooled
| configuration in case of an emergency.) This is different
| from TRISO fuel, which isn't supposed to be molten in normal
| operation but which structurally limits the spread of fuel
| and fission products at high temperatures.
| acidburnNSA wrote:
| They can melt. They all do during fuel synthesis. They're
| pre-melted.
| acidburnNSA wrote:
| No. LFTRs have fluid fuel. There are some solid-fueled clean
| molten salt cooled reactors that are called Fluoride salt
| cooled high-temperature reactors (FHRs).
| Gibbon1 wrote:
| I read a detailed report of the one in Germany. Thing totally
| sucked. Two big problems the indestructible alumina pebbles
| cracked and contaminated the reactor. Second was inhomogeneous
| burn rates. I think I remember some pellets got stuck when they
| decommissioned the reactor.
| DiabloD3 wrote:
| I literally came here to say the same thing. It reads like
| someone is just trying to remarket the concept to people in
| their 50s and up to accept nuclear power as their one true God.
| Xcelerate wrote:
| > Most nuclear reactors today operate well below 1,000 degrees
| Fahrenheit
|
| I have a background in chemical engineering and still had no clue
| that nuclear reactors operate at the temperature of a pizza oven.
| That's wild.
| klodolph wrote:
| What's amazing to me is that the kind of graphite used in
| nuclear reactors doesn't burn until it's white hot, somewhere
| around 1650degC.
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