NNadir

NNadir's Journal

February 17, 2019

A Reactor Designed to Burn Through It's Core: Design of a "CANDLE" Nuclear Reactor.

The paper I'll discuss in this post is this one: Design concepts of small CANDLE reactor with melt-refining process (Obara et al Progress in Nuclear Energy Volume 108, September 2018, Pages 233-242).

Recently in this space, I posted a paper about the properties of molten uranium oxide, including a picture of an unfortunate example of a result of the actual macroscopic formation of that fluid, the "Elephant's Foot" (molten uranium oxide mixed with structural reactor materials) that solidified, upon cooling, inside the core of the Chernobyl reactor that blew up in 1986.

The Structure of Molten Uranium Dioxide.

In the last few weeks, a robot made it to the debris pile formed in unit 2 of the Fukushima Daiichi reactor which was destroyed by an tsunami in 2011. The tsunami killed about 20,000 people, very few of whom, if any, were killed by radiation - there may be a few who were, one has been reported at such - with the bulk of the 20,000 being killed by seawater, not that anyone is calling for the phase out of coastal cities as a result.

Tepco makes contact with melted fuel in unit 2

A video of the robot manipulating the damaged fuel is available on the internet.

What I personally learned from these two events, the event at Chernobyl and the events at Fukushima is that the worst cases for nuclear reactor failures were less onerous that the best case for the normal operations of dangerous fossil fuel and dangerous "renewable" biomass combustion since wastes from these two forms energy kill more than 7 million people per year even if no accidents occur.

The rest of the world may have drawn a different conclusion than mine, choosing to destroy the planet as a whole with climate change, irrespective of the 56 million people who died from air pollution since the melt down of the Fukushima Daiichi nuclear plants following a tsunami that killed 20,000 with seawater.

Worldwide, it has also been popular to allow ignorant and foolish people to lead countries whose importance to climate can not be overstated, Donald Trump in the United States, Jair Bolsonaro in Brazil, and in countries that will suffer greatly from climate change, Rodrigo Duterte in the Phillipines, Recep Tayyip Erdoğan in Turkey.

Nevertheless, in the popular imagination it is popular to believe that what is popular is good.

Many years ago, for business purposes, I bought a new car, a Mercury Sable, which was an upgraded "luxury" version of the (then) "best selling car in the world," the Ford Taurus. It was the worst car I ever owned. After 50,000 miles, I could no longer drive with clients in the car because everything was broken, and I do mean everything, the seats, the electric windows, the air conditioning. Even the rear view mirror had fallen off. The engine blew well before 80,000 miles, despite the fact that the car was well maintained.

Cars, by the way, suck, but in the popular imagination in this country, no one can imagine that we can live without them, even though car accidents kill way more, vastly more, people than nuclear accidents.

The "best selling idea" in energy, by the way, is the dubious and frankly, ignorant, conclusion that so called "renewable energy" is the best way to address climate change.

Renewable energy has not done anything significant to reverse climate change, it is not doing anything significant to address climate change, and it will not do anything significant to address climate change.

The reason is physics.

Here is the data as of this morning, after the expenditure of trillions of dollars on this planet on wind and solar energy in this century alone, from the Mauna Loa Carbon Dioxide Observatory showing the concentration of the dangerous fossil fuel waste carbon dioxide in the planetary atmosphere:

Week beginning on February 10, 2019: 412.41 ppm
Weekly value from 1 year ago: 408.55 ppm
Weekly value from 10 years ago: 387.17 ppm
Last updated: February 17, 2019

Don't worry, be happy. We're selling lots of electric cars these days, worldwide.

The increase registered for the week beginning on February 10, 2019 over the same week of February 2018 is one of 2245 such readings recorded since 1975 at the Mauna Loa CO2 observatory. The value, 3.86 ppm over last year, is the 26th worst of all time, placing it in the 98.9th percentile for worst ever.

Again. Don't worry. Be happy. Solar City. Elon Musk. Tesla car. Space X.

Irrespective of the popular fascination with Chernobyl and Fukushima, which generates the extremely stupid but popular claim that "nuclear energy is too dangerous," without asking the question "compared to what?" first, my own interest in these incursions into the melted fuel at Fukushima and Chernobyl is concerned with what these materials can tell us about the behavior of nuclear fuel at very high temperatures.

The Fukushima robot did not bring a sample of fuel out of the core, but ultimately it will, since much of the fuel seems to be gelatinous or powdery as shown in the video. We know, of course, that the fuel released considerable amounts of the volatile elements cesium and iodine, but it would be useful to understand the chemical state and elemental distributions of the fuel itself, generated under real failure conditions.

The reason this is interesting to me is that I have convinced myself that it absolutely necessary - if we ever become interested in practical approaches to addressing climate change - that very high temperature nuclear fuels be utilized to remediate the ongoing climate catastrophe which is getting worse, not better.

All the things I have thought about nuclear energy will die with me soon enough. Last night however, my wife and I had the pleasure of traveling to my 19 year old son’s university - we needed to go over some paperwork - and having dinner with him. He is much smarter than I will ever be or ever have been, but, as I have lived longer and thus currently have seen and read more, and thus I have more information despite being of lower native intelligence, I gave a little lecture on neutrons over lemon meringue pie, capture cross sections, scattering cross sections, Breit-Wigner resonances, blah, blah, blah...since right now I know more about neutrons than he does.

My son will work with neutron fluxes this summer at a national laboratory, and when he comes back from his internship, he'll know more about neutrons than I ever will, I expect. This knowledge will give him the tools to help his generation recover from what my generation has done to his, which is to steal from them the stability of the entire planet.

I'm not particularly concerned with dying with all my best ideas, since I've had the happy circumstance of learning that very few of my ideas prove to be actually original. My fondness for breed and burn nuclear reactors based around molten metallic plutonium eutectic fuels is a little different in that tiny fraction of the nuclear engineering literature I've accessed, but good ideas, even great ideas have a way of surfacing independently of particular individuals. This was true even of Issac Newton. Calculus was discovered independently of Newton's discovery by Leibnitz, because the time to discover calculus had arrived in Europe.

I'm very lucky too, in that I have a son who can easily grasp any technical thing I say. I email him scientific papers of interest, and sometimes he actually reads them. Anything of value I have to say, will be all that lives of me, in him and his brother, after they dispose of my dead body. Of course, he's not me and will have his own ideas. He's better than me; which is in my view what a father should want, children who are better than he is. I'll die happy, I think.

All this brings me to the paper I evoked at the outset of this post.

One of the prominent researchers in the concept of "breed and burn" nuclear reactors is the Japanese scientist Hiroshi Sekimoto.

He wrote a marvelous little book about his ideas, and I've had the pleasure of leafing through it. You can too, if you want. The whole book is now available on the internet; I just downloaded the whole thing in a few seconds to replace my scanned copy:

Light a CANDLE: An Innovative Burnup Strategy of Nuclear Reactors

Light a candle...

We live in such dark times, environmentally dark times. History, I think, will not forgive us, nor should it.

And now, the paper evoked at the beginning of this post. The introductory paragraph:

The CANDLE (Constant Axial shape of Neutron flux, nuclide densities and power shape During Life of Energy production) burnup concept was first proposed by (Sekimoto et al., 2001). In a CANDLE reactor, the constant shapes of neutron flux, nuclide number densities and power density distributions shift in the axial direction. The CANDLE reactor core can be divided into roughly three regions: the breeding region composed of fresh fuel, the burning region which produces the main portion of power in the core, and the spent fuel region containing fission products. During operation, the main portion of the neutrons and energy are produced by fission of the fissile materials in the burning region. In the front side of the burning region, the fertile materials absorb leaked neutrons from the burning region to transmute into fissile materials. Therefore, the distribution of fissile materials shifts to the burning region. The spent fuel region is the region left behind by the burning region, composed mainly of fission products and depleted fuel. In this way, the burning region moves along the core axis.

The advantages of this reactor are summarized in the following paragraphs of the paper. Among these, the most important listed to my mind is that the reactor can operate for decades without refueling - the length of time it does so being controlled by the height of the core - and that it can burn either depleted uranium - now considered by people who don't know very much to be "nuclear waste" - or natural uranium without any enrichment. Another advantage is that since the fuel is not fissionable without a "spark" - I'd use plutonium for this purpose - the risk of a criticality accident does not exist.

With a "breed and burn" approach, it is technologically feasible that the uranium already mined, along with the thorium already mined and dumped as a side product of lanthanide mining to make things like stupid electric cars and useless wind turbines, might allow for the cloture of every coal mine, every natural gas well, every oil well on the planet.

Here is a segment of the text that addresses the problem of what to do with the used nuclear fuel after the nuclear reaction have burned through the core, which ultimately it will do. In this case the fuel is clad, as is the case of existing reactors, although I imagine cases were cladding is not so much an issue as are fluid barriers.

A CANDLE reactor can achieve 40% burnup of spent fuel without reprocessing and enrichment (Sekimoto et al., 2001). To realize a longlife CANDLE core, it is important to maintain fuel cladding integrity under ?40% burnup (Sekimoto, 2010). Several solutions to overcome this challenge have been proposed. The first is the recladding method, investigated by (Nagata and Sekimoto, 2007). In this method, fuels in the process of burning are removed from the core, gaseous fission products are also removed from these fuels, and the fuels are recladded. Then, they are reloaded into their previous position in the core. The effects of recladding in this method were small; the shape of each burnup distribution was almost the same, and burnup was increased by 1%. Another solution to maintain fuel cladding integrity is to apply the melt-refining process introduced by (Abdul Karim et al., 2016), (2017).

It would be an interesting and better world if dangerous fossil fuel companies were compelled to imagine what to do with their fuel after it's burned, but they aren't. With the practical acquiesce of everybody on earth - the popular approach while we wait for the grand "renewable energy" nirvana that never came, is not here, and will not come - they simply dump their fuel into the planetary atmosphere, where it impacts every man, woman and child on the planet, and will impact every man, woman and child for many centuries (unless future generations have the resources to clean up our mess) and in fact, every living thing on the planet, now and in the future.

From the text:

I have not accessed the Abdul Karim references yet but will.

They are here:

Application of melt and refining procedures in the CANDLE reactor concept (Julia Abdul Karim et al Annals of Nuclear Energy Volume 90, April 2016, Pages 275-283)

Effects of cooling interval time in melt and refining process for CANDLE burning (Julia Abdul Karim et al Annals of Nuclear Energy Volume 105, July 2017, Pages 144-149)

I love the PI's name, Julia Abdul Karim, another person engaged in saving the world.

I have had a lot of exposure to concepts in pyroprocessing over the years, and am quite fond of it, although truth be told, I'm rather fond of pyroprocessing techniques that are truly in process, that is, while the nuclear fuel is being consumed, employing the interesting and useful stuff we found out by accident from the events at Chernobyl and Fukushima, albeit in a way with negative consequences.

I've also come up with some concepts in reprocessing existing used nuclear fuel that I think might be novel - at least I haven't found such an approach mentioned in the literature as yet - that has some features of pyroprocessing but strictly isn't. I'll tell my son about them someday, after he has time to divert himself from things like his technical problem de jour, a homework assignment on property fluxes in matter and heat transfer in a chemical reactor for which the mathematics - integration of gradient expressions - is giving him a confusing result.

He's smarter than I am. It will work out.

I hope the next generation, for whom I have great hope, will all prove smarter than we have been. (For God's sake, we have a useless and ignorant criminal parasite in the White House, and we allowed this to happen. The orange nightmare is the reification of the intellect and attention of my generation.)

We also allowed climate change to happen, by the injudicious use of selective attention, the same kind of selective attention that results in focus on things like Hillary Clinton's email server, and, oh yeah, Fukushima and Chernobyl.

Anyway, the text continues:

The melt-refining process was developed in an EBR-II reactor project (Hesson et al., 1963). In this process, fuel pins are decladded, all volatile and gaseous fission products are substantially removed, and at least 95% of the reactive fission products are removed; no separation will occur for noble fission products in the melt-refining (Hesson et al., 1963). They investigated the possibility of introducing this process into a large-scale CANDLE reactor (Abdul Karim et al., 2016), (2017), and were able not only to maintain fuel cladding integrity in the high burnup condition, but also to improve the burnup performance of the large-scale CANDLE reactor. In previous studies (Greenspan and Heidet, 2011), (Heidet and Greenspan, 2012), performed by Ehud Greenspan and Florent Heidet, respectively, the melt-refining process was also applied successfully to large-scale breed and burn reactors to extend the lifetime of the fuel and achieve high burnup. This raises the question of whether it is possible to apply the melt-refining process to a small CANDLE reactor, which generally requires high neutron economy.

The neutron economy problem arises because some fission products have a high neutron capture cross sections, and it is important to remove those that do, even though neutron capture can greatly shorten the half-lives of some radioactive elements, a process that falls under the general rubric of "transmutation of" (so called) "nuclear wastes".

The Candle Reactor proposed here is small, about 1/10th the power output of typical existing commercial pressurized water reactors and/or boiling water reactors that are in common use around the world, saving human lives that would otherwise be lost to air pollution. It's power output is about 300 MW thermal. How this thermal energy might utilized is open: The outlet temperature of the lead bismuth eutectic coolant is said to be 800K, or 523C, temperatures which may prove useful for highly efficient production of electricity via combined cycle schemes, but it too low for advanced thermochemical carbon dioxide or water splitting to make portable chemical fuels and materials.

Some graphics from the paper follow.

This one gives a feel for the core size, which one may compare with the dimensions of say a field of useless greasy steel, aluminum and plastic bird and bat grinders in the sky, which might produce as much power briefly when the wind happens to be blowing, and nothing at all when it isn't. The core of this reactor could fit in the foyer of a McMansion owned by a person who imagines his or her Tesla car might save the world.

The caption:

Fig. 1. Basic axial configuration of the core.

The structure of the cladded fuel and information about heat flows:

The caption:

Fig. 2. Schematic fuel cell layout.

A flow chart of core calculations:

The caption:

Fig. 3. Flowchart of reference core calculation.

The caption:

Fig. 4. Cross-section view of single sub-channel model geometry.

Core temperatures:

The caption:

Fig. 5. Temperature distribution in the axial direction of sub-channel.

The caption:

Fig. 6. Schematic of melt-refining process operation for CANDLE reactor.

The size of fuel zones:

The caption:

Fig. 7. Melt-refining regions in the core.

They used to call Charles DeGualle "deux metres" (two meters) reflecting his height. This core, designed to produce energy more reliably than a field of bat and bird grinders in the sky, this for a period of decades, while producing no dangerous fossil fuel waste, is slightly taller than Charles DeGualle was.

The calculation flow chart for the recycled fuel.

The caption:

Fig. 8. Calculation flow chart of CANDLE reactor with the melt-refining process.

The "burnup" of nuclear fuel is a calculation of the amount of energy that the fuel produces in use, a unit very much like familiar terms like "miles per gallon" or "km per liter," for gasoline. In the following graphic, the unit of burnup for nuclear fuel is the GWd/ton, which is a unit of energy per unit mass and not peak power has is so often, and so misleadingly (mis)used to describe so called "renewable energy" devices. Five hundred GWd is 4.32 X 10^(16) joules, or 42.3 petajoules. A common, but somewhat silly unit of energy that finds its way into the international energy parlance is MTOE, million tons of oil equivalent. It is equal to 42 petajoules. It follows that the burn up of one ton of depleted uranium in this reactor core, a little taller than Charles De Gualle was, is the equivalent of 1.03 million tons of petroleum.

How the environmental advantages here can escape the public imagination is completely incomprehensible to me.

The graphic:

The caption:

Fig. 11. Core averaged burnup distribution.

The consumption of "depleted uranium:"

The caption:

Fig. 13. Core averaged number density distribution of U-238.

The production of plutonium:

The caption:

Fig. 13. Core averaged number density distribution of U-238.

Power density in the core:

The caption:

Fig. 15. Core power density distribution at BOC [W/cm3].

BOC refers to "Beginning of Cycle" where the cycle in question is the fuel cycle.

Whether anyone believes me or not - and I am intimately familiar with the mentality and dogma of anti-nukes, which frankly leaves me ethically appalled - this kind of work is the key to saving the world, which is not to say that we will save the world.

I love to brag about how smart I think my sons are - they are smart - but they are emerging into a world from which much has been stolen.

It is my hope and expectation that my son the engineer will use his mind in the same way that these scientists are, to looking to the practical considerations by which the world might be saved, because, again, if it is saved, approaches like these will do it.

I trust you'll have a pleasant Sunday afternoon for what remains of it, and a lovely evening as well.

February 16, 2019

Science on Saturday: Osteoarthritis of the Hip and Knee: The Science Behind the Pain...

...and How New Research is Revolutionizing Treatment.

One of the joys of living near Princeton NJ is the Science on Saturday series held at the Princeton Plasma Physics Lab in the winter months, hosted by Dr. Andrew Zweiker, PPPL outreach physicist and Democratic Assemblyman in the New Jersey Legislature.

My wife and I and two of our friends attended this one a few weeks, and it was, like most, very engaging.

Science on Saturday; Osteoarthrritis of the hip, and knee, the science behind the pain.

Scroll down for the video and enlarge it.

The speaker, Dr. Christina Gutowski, used to go to Science on Saturday Lectures in Princeton when she was a girl, and my fantasy is that my son, who started going with me when he was 11 and is now doing well as a Materials Science student will someday do well enough in his career to do the same.

The one last week, was absolutely fabulous, where a scientist described in detail what it was like to camp in Antarctica on a meteorite finding mission.

I'll post it when the video comes up.

Science on Saturday, PPPL, Winter, 2017

February 10, 2019

A Discussion of Direct Air Capture of Carbon Dioxide.

The scientific paper that I will discuss in this post is this one: Moving Beyond Adsorption Capacity in Design of Adsorbents for CO2 Capture from Ultradilute Feeds: Kinetics of CO2 Adsorption in Materials with Stepped Isotherms (Christopher W. Jones et al Ind. Eng. Chem. Res., 2019, 58 (1), pp 366–377)

We have failed miserably at addressing climate change and the rate of degradation of the planetary atmosphere is now proceeding at the fastest rate ever observed. The popular approaches to doing anything about climate change - at least among bourgeois types with the time and resources to pick lint out of their navels and daydream - specifically drive around in electric Tesla cars and applaud endlessly and mindlessly for wind turbines and solar cells, have not worked, are not working and will not work.

The reason is physics.

Since we have irresponsibly and contemptuously dumped the consequences of our irresponsibility on future generations with an uninterrupted sequence of pie-in-the-sky pronouncements ("By 2035"..."By 2050"..."By 2100"... etc, etc...) of when the grand so called "renewable energy" nirvana will spontaneously arrive, the only avenue that these generations, from whom we have stolen the future, will have, should they hope to restore anything that can be restored, will be geoengineering.

After some decades of considering the issue, I have drawn the conclusion that the only type of geoengineering that makes any sense whatsoever is the removal of the carbon dioxide, the dangerous fossil fuel waste, that we and previous generations have dumped, again, with contempt for the future, into the planetary atmosphere, thus dangerously destabilizing it.

From my perspective, one of the things we've dumped is not only the chemical wastes themselves, including but hardly limited to carbon dioxide, but also entropy. Over coming entropy involves energy.

The entropic situation is some what less dire in seawater than it is in air, and I believe that the only realistic approach for solving this huge thermodynamic problem which translates into a vast engineering problems, is to process seawater, which besides removing carbon dioxide, may also solve and/or ameliorate several other major environmental problems involving entropy.

Nevertheless, after seeing him speak some years ago at a meeting of the American Chemical Society, I have been following the work of Dr. Christopher Jones at Georgia Tech, who has focused on the removal of carbon dioxide directly from air.

Thus, I was pleased to come across one of his papers some weeks ago in my general reading, the paper referenced above.

Here's the cartoon graphic of what the paper is about:

Note that the "feed" gas here has 400 ppm of carbon dioxide, which was the concentration of this dangerous fossil fuel waste in air a few years back. We are now at over 411 ppm as of this morning, and currently concentrations are rising at a rate of 2.3 ppm/per year, with no slow down in sight. (And no, sorry, the "Green New Deal" lead by Edward Markey, antinuke, won't cut it.) No one now living will ever again see a carbon dioxide concentration as low as 400 ppm again, although one hopes that future generations may be smarter than the dumb shits we apparently are, and find a way to geoengineer as described above. The magnitude of the engineering requirements are so high however, that I feel fully confident in saying "no one now living."

Nevertheless from the introduction to Dr. Jones's paper:

CO2 capture from ultradilute feeds is gaining attention as a key part of global and local carbon management programs.(1?3) Direct air capture (DAC) is one of the few carbon emission mitigation technologies that has the potential to be carbon negative. Amine-functionalized adsorbents such as mesoporous silica,(3?5) carbon,(6) and metal organic frameworks (MOFs)(7,8) have attracted attention for DAC because of their high CO2 capacities even at ultradilute CO2 concentrations. Much of the work in this field has focused on the development of materials with large equilibrium adsorption capacities.(9?11)

Metal organic frameworks (MOFs) are a class of hybrid organic–inorganic materials that have generated significant interest for CO2 capture. Several MOFs have been developed that strongly adsorb CO2 at ultradilute concentrations.(12?14) One example is the amine-functionalized Mg2(dobpdc) material reported by Long and co-workers.(13,15,16) The Mg2(dobpdc) framework, when functionalized with N,N?-dimethyl ethylene diamine (MMEN) and ethylene diamine (ED), has room temperature CO2 uptakes of 3 mmol/g(15) and 2.83 mmol/g,(17) respectively, in the presence of 0.4 mbar of CO2. The sigmoidal shape of the CO2 isotherm in these materials has been explained in terms of a cooperative insertion mechanism in which capture of one CO2 creates a facile pathway for capture of another CO2. This mechanism has led to the creation of a series of materials with a sharply stepped CO2 adsorption isotherm in which the variation in metal centers and diamines allows the pressure at which the step occurs to be tuned.(15) The existence of a sharp step in the CO2 isotherm suggests that a high working capacity for CO2 capture may be possible in a cyclic adsorption process using a relatively small change in pressure or temperature.(16,18) A key aim of this paper is to explore whether factors extending beyond this conceptual description of equilibrium adsorption may be critical in practical applications of these materials.

Keep in mind that even "small" changes in pressure and temperature dealing with carbon dioxide capture on a scale of trillions of metric tons of carbon dioxide - we have dumped the stuff on this scale - implies vast, incredibly vast, quantities of carbon free energy - this at a time when the proportion of fossil fuel energy is rising significantly as well as absolute quantities. In the year 2000, when energy demand was well under 400 exajoules per year, 80% of the world's energy came from dangerous fossil fuels, in 2017, when world energy demand was almost 200 exajoules higher, specifically 584 exajoules, dangerous fossil fuels represented 81% of the world's energy production.

Nevertheless, Dr. Jones goes bravely into defining what a practical process might look like, while confessing that little is actually known about such a process might involve:

Practical adsorption-based separations require that the adsorbent be deployed in a fixed-bed, immobilized on a practical substrate such as a monolith(22,23) or hollow fibers,(24,25) or deployed in a fluidized bed.(26) Ultradilute systems require special attention to the design of the gas–solid contactor, necessitating designs that offer very low pressure drops such as fiber and monolith contactors.(11,27) Mass transfer in these systems can potentially be affected by a range of competing heat and mass transfer effects, including film, macropore, or micropore resistances and adsorption/desorption/reaction. Film and macropore resistances are relatively well understood.(28,29) Nontrivial components of system design include the estimation of micropore diffusion, surface resistances, and reaction (or adsorption/desorption) kinetics. Usually, one or more of these are the controlling resistances, and limited studies exist for transport of CO2 in supported amine materials.(30?38) In the absence of precise microscopic techniques, macroscopic techniques such as gravimetric uptake or pressure decay can be used to measure the kinetics of CO2 adsorption.

He explores these issues with TGA, thermogravimetric analysis.

A well-designed experiment with a small bed can allow accurate predictions for larger beds if it can capture the dynamics of CO2 adsorption satisfactorily. Some of the parameters of interest are the CO2 concentration profile at the exit of the bed, the fractional bed usage, the overall CO2 capture fraction, the breakthrough time, the productivity, and the adsorption rate constant, kads. Mass transfer of CO2 in a packed bed can be modeled by eq 1,(46) which takes into account dispersive and mass transfer effects.

Equation 1 is this differential equation:

Appealing to earlier work related to the theory of chromatography (as well the use of metal organic frameworks he explores here) he offers us this equation describing "absorption waves."

In the absence of any dispersive and diffusive effects associated with diffusion of gas molecules, the actual velocity (w) of a particular adsorption wave can be related to the superficial velocity (ug) by eq 2

(2)

One of the references for this equation, this one, Applying the wave theory to fixed-bed dynamics of Metal-Organic Frameworks exhibiting stepped adsorption isotherms: Water/ethanol separation on ZIF-8 (Julien Cousin-Saint-Remi, Joeri F.M. Denayer, Chemical Engineering Journal 324 (2017) 313–323), is a paper apparently focused on another energetically expensive process, the separation of water from ethanol, commonly employed in an effort to get Iowa corn farmers to vote for specific Presidential candidates in elections.

It features this cool cartoon graphic showing an MOF, metal organic framework:

Isn't that special? We're saved.

Just kidding...

The above equation is simplified by appeal to "Golden's Chord Rule" that allows determination of absorption waves in this fashion:

This graphic is offered to show geometrically how it works:

The caption:

Figure 1. Shapes of various types of isotherms (top), corresponding concentration fronts inside the bed (middle) and corresponding breakthrough curves (bottom) as predicted by the local equilibrium theory. Dashed red lines indicate the chords used in applying Golden’s String Method to describe the bed behavior from the initial state (I) to the feed point (F).

In any case, some experiments are set up to compare with theory.

Here's a schematic of the apparatus employed by the Jones Group:

The caption:

Figure 2. Packed bed adsorption system schematic

The IR detector - the strong absorbance of infrared energy by CO2 is why it's a climate gas - detects the "breakthrough" of carbon dioxide from the packed bed, when its capacity is full.

A model is constructed of the absorption:

Total adsorption is the sum of two adsorption mechanisms denoted by q1* and q2*. The equilibrium adsorbed quantity at the isotherm transition pressure, pstep, is denoted by qsat. Adsorption of CO2 below pstep is represented by a Sips isotherm with a temperature dependent surface heterogeneity factor (nL). A combination of Langmuir and Henry’s isotherm is used after the transition step.

A smooth function(w) is used to switch between the low pressure Sips and the high pressure Langmuir–Henry isotherms, shown here in eq 10. Parameters in the isotherm are listed in Table S1. Other details in the isotherm are given in eqs S1–S13 and Table S1.

Equation 10 is quite beautiful to look at:

Anyway, the model developed apparently works quite well when compared to experimental data points:

The caption:

Figure 3. Experimental data (symbols) and modeling fit (solid curves) at 25 °C (black), 49 °C (red), and 69 °C (blue) for CO2 adsorption in MMEN–Mg2(dobpdc). Parameters for the modeling fit are listed in Table S1.

Application of Golden's String Rule for CO2 breakthrough:

The caption:

Figure 4. Application of Golden’s string analysis to predict breakthrough curves resulting for the simulated CO2 isotherm in MMEN–Mg2(dobpdc) at 23 °C at conditions relevant to DAC. The overall partial pressure change between the initial state of the bed, I, and the feed concentration, F, in (a) is divided into two zones in (b) and (c).

Some more on breakthrough:

The caption:

Figure 5. Normalized breakthrough profiles for a packed bed of MMEN–Mg2(dobpdc) at 23 °C as a function of the partial pressure of CO2 in the gas entering the bed. Simulations (left) and experiments (right) were carried out at the flow rate of 17.2 N mL/min. The results are shown in terms of the normalized CO2 concentration at the exit of the bed.

Note that here we're talking in terms of milliters, and for the atmosphere, we're talking trillions of tons. Note too that some of the concentrations of carbon dioxide are multiple orders of magnitude of the current (disastrous) levels in our atmosphere, heading toward Venus, not that we show any reluctance to go there.

A graphic more appropriate to the real world in which we live:

The caption:

Figure 6. Breakthrough adsorption experiments performed at 23 °C with the feed containing CO2 at the partial pressure of 0.4 mbar and different flow rates of 17.2, 28.2, 48.6, and 100 N mL/min. The figure on the left shows the full breakthrough profile while the figure on the right shows breakthrough profiles for the first 3 h.

Some more about the model:

The caption:

Figure 7. CO2 uptake at 23 °C (black diamond) on TGA for a typical sample of MMEN–Mg2(dobpdc). As shown in the figure on the left, one single pseudo-first-order uptake model (red solid line) is not sufficient to model the entire uptake. As shown in the figure on the right, a hybrid model with pseudo-first-order model (red solid line) for the initial uptake and the Avrami model (blue solid line) for the subsequent uptake fits the data well.

Note the time scale and the flow rates.

The caption:

Figure 8. Experimental (scatter) and simulated (solid lines) breakthrough profiles for CO2 adsorption with the CO2 partial pressure of 0.4 mbar in the feed. Simulated profiles were obtained at a flow rate of 17.2, 28.2 N, 48.6, and 100 N mL/min at 23 °C. The Avrami model was used in this analysis to account for the cooperative CO2

I'm not entirely sure how "practical" any of this really is, since the volume of the atmosphere is huge, but offer the following caveat.

I am, in general, hostile to the idea of energy storage since generally it wastes energy and the idea is bandied about in popular culture to further squander money and resources to overcome the biggest drag on so called "renewable energy," its inherent reliance on the weather, such reliance being a factor on why so called "renewable energy" was abandoned by humanity beginning at the outset of the 19th century. (We often forget that the idea of so called "renewable energy" is reactionary and is in no way new, particularly where wind energy is involved.)

A caveat to this statement is the general feeling that one form of energy storage might be capable of avoiding the worst of this waste of energy by the application of waste heat: Compressed air storage. This has the potential to convert energy storage into energy recovery by considering a system that converts the compression into, effectively, a Brayton cycle, by which jet engines and combined cycle dangerous natural gas plants operate.

One can imagine a system where the necessary flows of air so involved might utilize these MOF systems Dr. Jones's Group describes.

From the conclusion of the paper:

The MOF MMEN–Mg2(dobpdc) has shown unprecedented, high adsorption capacities and high amine efficiencies at ultralow partial pressures of CO2 in equilibrium isotherm studies. This system shows a stepped isotherm that is tunable, and it has been suggested previously that such a system may be ideally suited for direct air capture (DAC) applications. In this work, CO2 adsorption in MMEN–Mg2(dobpdc) was studied under ultradilute conditions using a breakthrough adsorption setup as a proxy for practical flow systems. Dynamic CO2 adsorption experiments were carried out at various flow rates, temperatures, and concentrations. The resultant breakthrough profiles were analyzed using local equilibrium theory. Local equilibrium theory suggested either a shock wave–dispersive wave–shock wave or a shock wave breakthrough, depending on the feed concentration. This was confirmed through experiments where a shock wave–dispersive wave–shock wave breakthrough was observed in experiments simulating DAC conditions. A shock breakthrough was observed for CO2 concentrations above 1%. A higher wave concentration was observed in adsorption experiments at higher flow rates using the feed concentration of 400 ppm, corresponding to DAC

It's a very nice paper, a wonderful paper, and I hope to continue to monitor the Jones Lab's work for as long as I can.

I trust you're having a pleasant Sunday afternoon.

February 10, 2019

Separation of Uranium from Lanthanide (Rare Earth) Ores.

The paper I'll discuss in this post is this one: Selective Removal of Uranium from Rare Earth Leachates via Magnetic Solid-Phase Extraction Using Schiff Base Ligands (Laurence Whitty-Léveillé†‡, Nicolas Reynier†‡, and Dominic Larivière*‡ Ind. Eng. Chem. Res., 2019, 58 (1), pp 306–315).

In two previous posts in this space, I discussed the properties of the element cerium, one of the 14 (15 if you count yttrium, 16 if you add scandium) lanthanide or rare earth elements.

Polymers of Cerium and Plutonium.

Cerium Requirements to Split One Billion Tons of Carbon Dioxide, the Nuclear v Solar Thermal cases.

In the latter post, I pointed out that there is not enough cerium in the world to reliably split even a minor fraction carbon dioxide released each year while we wait like Godot, for the "Green New Deals," "Gazillion Solar Roofs," "Energiewende..." ...blah...blah...blah...blah...programs to slow climate change which, even as people around the world have thrown trillions of dollars at them, have failed, completely and totally, to have any effect on climate change.

They haven't worked, they aren't working, and they won't work. The reason is physics.

They, schemes centered on so called "renewable energy" nonetheless remain very popular, which goes to show you that very often - this should be very obvious - what is popular is neither good, effective, realistic, or remotely honest.

In rhetoric, the fallacy underlying this sort of situation is known as the bandwagon fallacy, which is a feature widely exploited in advertising, since it is not true that the "Best selling car," is actually a good, reliable or safe car, or that the "best selling nutritional drink" is good for you, or that "the best selling acne treatment" is effective at treating acne, and so on.

In my tenure here at Democratic Underground going back to 2002, I've had a lot of very unpleasant interactions with people embracing this fallacy, the sort who like to point out that somewhere a huge bird and bug and bat grinding wind farm is being built somewhere while elsewhere a nuclear plant is being shut.

I have always struggled against my own stupidity in many ways and sometimes - not always, but sometimes - I have succeeded in overcoming it: Here, I've learned to use the wonderful "ignore" button to avoid interacting with the preternaturally stupid people who are different from me only in that they are satisfied with their stupidity, revel and wallow in it, assert it as a positive good, and are proud of it. The person currently described as the "President of the United States" is famously such a person, but there are many other examples of similar people and frankly - I say this as a life long Democrat who has always voted Democratic, even at some pain - we have examples of such people in our party, and in fact, on this website. We all know them here and elsewhere, at work, at school, in our neighborhoods, even if we never turn on the TV to watch words drool out of the criminal babied orange fool who has described himself as a "real stable genius."

Anyway...

Despite the advertising success of so called "Renewable Energy!!!!!" - a brand name that is itself a lie since this form of energy is neither "renewable" or sustainable because of the low energy to mass ratio involved in the devices to collect and store it - the degradation of the planetary atmosphere is accelerating: The rate of increase has now reached an average of 2.3 ppm per year.

Even if you can sell electric cars by putting pictures of solar cells in the ad, or wind turbines, or both, here is what it says on the Mauna Loa Carbon Dioxide Observatory website as of this writing:

Week beginning on February 3, 2019: 411.63 ppm
Weekly value from 1 year ago: 407.81 ppm
Weekly value from 10 years ago: 386.99 ppm
Last updated: February 10, 2019

The type of data reported here, by the way, is one of 2,245 such data points recorded and posted by the Mauna Loa Carbon Dioxide Observatories website, going back to 1974. The increase over the same date of the previous year, 3.82 ppm, is the 29th largest ever recorded. Of the top 50 such data points, 32 have been recorded in the last 5 years, 37 in the last ten years, and 40 in this century.

We have no realistic plan to stop what we are doing to all future human beings, and in fact, all future living things, because we cannot do what Abraham Lincoln told the country to do in other, far less deadly and dire circumstances, "think anew."

I have deliberately macerated the following text to take it out of the context of the American Civil War and an address to congress, to choose the phrases that appeal to any generation faced by seemingly insurmountable tragedy, and let's be clear, that the risk Lincoln faced, the destruction of the United States and its government is an inconsequential think when compared to the destruction of the planetary atmosphere:

The dogmas of the quiet past are inadequate to the stormy present. The occasion is piled high with difficulty, and we must rise with the occasion. As our case is new, so we must think anew and act anew. We must disenthrall ourselves...

...Fellow-citizens, we can not escape history. We... ... will be remembered in spite of ourselves. No personal significance or insignificance can spare one or another of us. The fiery trial through which we pass will light us down in honor or dishonor to the latest generation...

...We shall nobly save or meanly lose the last best hope of earth.

This text is always on my mind, not just because of the history of the American Civil War, but because of how the same ideas apply to climate change.

We shall nobly save or meanly lose the last best hope of earth.

I steal that beautiful locution, "last best hope of earth," all the time, taking it far out of any context Lincoln could have known, to describe nuclear energy.

This brings me closer to the scientific paper referenced at the opening of this post.

My previous post in this space referenced above, the one about cerium as a carbon dioxide splitting catalyst, contained the following text, repeated here for convenience, since ores is referenced in the paper under discussion.:

The concentration of the various elements in these ores varies considerably from mineral to mineral and site to site. Bastnaesite and Monazite can contain between 40-50% cerium, with lanthanum constituting another 20-30% and neodymium perhaps 15% to 20%. (cf Volker Zepf, Rare Earth Elements, A New Approach to the Nexus of Supply, Demand and Use, Springer, 2013, Table 2.3 page 23.) Xenotine is mined for the "heavy" lanthanides, notably dysprosium, which appear in trace amounts in most bastnaesite and monazite ores, as well as yttrium, which dominates this mineral.

Neodymium in neodymium iron boride magnets is often utilized in generators, including those in bird and bat grinders in the sky, a.k.a. wind turbines, marketed as being "green," even though they are no such thing. Neodymium is not really a "rare" element, and the common locution (with which I'm not comfortable) "rare earth" does not apply. It cannot be called a common element either; there are limits to how much can be recovered, and in any case, its recovery is environmentally onerous as I noted previously in this space:

Some life cycle graphics on so called "rare earth elements," i.e. the lanthanides.

Magnets utilizing dysprosium are somewhat superior to neodymium iron boride magnets, but more expensive. Probably the locution "rare earth" applies better to dysprosium, the main source of which is the less common mineral (compared to monazite and Bastnaesite), xenotine.

The external costs of isolating lanthanide elements is higher if the device running them spends a lot of time off line, put another way, if the capacity utilization is lower. The capacity utilization of wind turbines in most locations typically falls into the range of 30%-40%, meaning that 60% to 70% of time, the lanthanides in wind turbines do nothing. When they do nothing, power companies burn dangerous natural gas these days. Nuclear plants, by contrast, routinely run at better than 90% capacity utilization.

The paper discussed refers to the fact that in many cases lanthanide mine tailings are radioactive. (I have long been familiar with the radioactive thorium (and decay daughter) content of lanthanide ores, but the fact that lanthanide ores contain uranium as well, and, of course, all of its radioactive daughters is somewhat new to me. One learns something every day, if one is lucky.)

From the paper's introductory text:

Rare earth elements (REEs) have unique physicochemical properties that make them essential in many high technology components.(1) While REEs can be extracted from a large number of rare earth minerals, only three are predominantly used in the production of rare earth oxides, namely bastnasite ((Ce, La)(CO3)F), monazite ((Ce, La, Nd, Th)PO4), and xenotime (YPO4).(2) In addition to REEs, uranium and thorium are often found in rare earth minerals such as monazite via lattice substitution.(2) Uranium can usually be found at concentrations up to 5% and 0.1% in xenotime and bastnasite, respectively, and at trace levels in monazite.(3)

The presence of naturally occurring radioactive materials (NORM), including U and Th, in these minerals is problematic from both a regulatory and health physics perspective for the mine operator.(4,5) Thus, effective methods to separate NORM from valuable REE constituents are essential.(6) While most of the short-lived decay products from Th- and U-series, such as Ra, Pb, Po, and Bi, could be segregated from REEs as they exhibit different chemical behavior during acid leaching and separation steps,(7) the separation of naturally occurring actinides from lanthanides still needs to be addressed.

Numerous strategies have been published to segregate U/Th from REE leach liquor. As an example, Sadri et al. recently reported that precipitation through pH adjustment followed by selective redissolution could be applied to REE leach liquor to isolate U, Th, and REE in distinct fractions.(7) However, these steps require precise pH adjustment and multiple phase separation to obtain the proper level of separation. Zhu et al. also reported that the combination of solvent extraction, selective dissolution and ion-exchange resin could be used to purify REE fractions from U/Th impurities.(6) However, this separation strategy, in addition to being cumbersome, generates significant volumes of radioactive acidic liquid wastes.

In the paper the authors describe a process whereby uranium can be removed from lanthanide ores by the use of ligands attached to magnetic particles. This type of process, widely utilized in analytical chemistry, of which it is a key component, as well as in some large scale processes, is called "solid phase extraction."

In this case, the solid phase particles are iron oxides supported on silica, "Fe3O4@SiO2."

Quoth the authors:

Magnetic solid-phase extraction (MSPE), employing Fe3O4 nanoparticles as a solid support, is an attractive alternative to other solid supports in terms of production cost and phase separation.(13,14) Fan and co-workers recently reported on the use of magnetic Fe3O4@SiO2 composite particles to remove uranium ions from aqueous solution.(15) The adsorption process demonstrated a maximum calculated uranium sorption capacity onto their magnetic nanoparticles (MNPs) composite particles of approximately 52.0 mg g–1 at 25 °C. The composite MNPs showed a good selectivity for uranium in the presence of other interfering ions such as Mg(II), Ca(II), Zn(II), and Sr(II)...

However...

While the magnetic nanoparticles provide an interesting strategy for phase separation, they lack the selectivity required for hydrometallurgical applications involving actinides and lanthanides.

The general scheme of what they propose is suggested by this cartoon from the paper's abstract:

The authors set out to address this lack of selectivity by covalently known organic extraction ligands showing selectivity to lanthanides and actinides to the magnetic particles. They have the following structure:

The caption:

Scheme 1. Structures of the Schiff base ligands synthesize and tested. (A) CH3Salen, (B) H2Salophen, (C) MeOSalophen

The selectivity of these ligands can be controlled by the size and geometry of the binding sites.

Appealing to in silico modeling the authors explore the use of substitutents on the basic system, where the "R" designated groups, as is customary in the organic chemical literature refer to "wild card" function groups that can be attached.

The caption:

Scheme 2. General Structure of the Schiff Base Family Ligands and Its Coordination of the Uranyl Ion

Substituents on the phenyl rings (R1–R4, R1?–R4? ) are freely modified and may be used for easy control over the ligand properties.

Exploring the ligand structures from "Scheme 1" the authors identify the uranium capacity for these derivatives.

The caption:

Figure 1. Effect of structure on the adsorption capacity of U(VI) ions by three crystalline Schiff bases. The initial uranium concentration 100 mg L–1, pH 6, temperature 20 °C, adsorbent mass 0.08 mmol, stirring time 24 h.

They evaluate the effect of ions that may commonly be found during the extraction processes used to isolate lanthanides from ores because of the high strength acids used to dissolve them, and the adjustments to the pH of the system that may be required:

The caption:

Figure 4. Impact of various media on the removal of U(VI) ions by MSB. Initial uranium concentration, 100 mg L–1; anion concentration, 4000 mg L–1; temperature, 20 °C; adsorbent mass, 0.025 g; stirring time, 24 h.

"Qe" in the ordinate of this graph refers to the binding capacity.

The kinetics of the reaction are not incredibly fast:

The caption:

Figure 6. Adsorption kinetic of U (VI). Initial uranium concentration in sulfate media 100 mg L–1, pH 6.0, temperature of 20 °C, amount of magnetic Schiff base 0.025 g.

One can imagine that this might be adjusted by adding excesses of the magnetic particles, or perhaps using an industrial flow system, should this technology ever come to industrial scale.

But the big issues is selectivity.

It's actually quite good, showing the ratios (the distribution coefficient) of the various elements captured by the particles.

The caption:

Figure 9. Competitive adsorption of concurrent ions on magnetic Schiff base, magnetic nanoparticles, and MeOSalophen in real leaching solution: pH 1.82; temperature, 20 °C; mass of adsorbent, 0.025 g; stirring time, 24 h.

The authors conclude:

U(VI) was extracted using magnetic Schiff bases with MeOSalophen. Using this magnetic extractant, that is conveniently separated by an external magnetic field, facilitates phase separation problems commonly encountered with more traditional adsorbents used in heterogeneous separation. Optimal extraction of U(VI) was achieved at pH = 6.0 with a contact time of 24 h in the presence of 25 mg of MSB. An adsorption capacity (Qe) of (63 ± 3) mg g–1 for U and a Kd value of over 5000 mg L–1 was found using those conditions. Using real REE leaching solutions, a lower Kd value of approximately 760 mg L–1 was determined, but the MSB maintained an acceptable degree of selectivity for uranium(VI) over a number of coexistent ions. The present study illustrates that MSB is usable as adsorbents for the effective removal of uranyl ions from complex mining solutions at various pH values. In the future, to improve the adsorption rate and increase the number of available complexation sites, appropriate Schiff base ligands could be chemically grafted onto magnetic nanoparticles instead of only being deposited.

Most of the world's lanthanides come from China, but occasionally China threatens the rest of the planet with export bans. This raises interest in opening mines in other countries, including both the United States and Canada.

The mining leachate used in the experiments here were Canadian in origin, and besides uranium, contained in higher concentrations other elements, including lead, thorium and cadmium.

Lanthanides are, by the way, common fission products found in used nuclear fuels and this separation technique could conceivably be modified for nuclear fuel reprocessing should we ever get serious about climate change, which we currently not even close to doing.

I have convinced myself that the only serious approach will involve mostly the recovery of uranium and thorium, as well as neptunium, plutonium, americium and curium from used nuclear fuels.

Under breeding conditions, the uranium and thorium already mined - the latter residing mostly in lanthanide mine tailings - are sufficient to shut every oil well, every gas well, and every coal mine on the planet for centuries.

I trust you're having a pleasant Sunday afternoon.

February 10, 2019

The final data's in: 2018 was the 4th worst year ever recorded at Mauna Loa for CO2 increases.

The annual growth rate for carbon dioxide increases has been reported, and 2018 came in as the 4th worst year for increases in carbon dioxide measured at the Mauna Loa Carbon Dioxide Observatory going back to 1959.

The increase was 2.68 ppm over 2017. The third worst year was 1998, when carbon dioxide concentrations rose 2.93 ppm.

The worst year ever recorded was 2015, when carbon dioxide concentrations increased by 3.05 ppm over 2014. The second worst was 2016, when carbon dioxide concentrations increased by 2.99 ppm over 2015.

For the 42 measurements recorded in the 20th century, from 1959 to 2000, 5 had an annual increase of 2.00 ppm in atmospheric carbon dioxide or greater. In the "percent talk" so popular among proponents of the so called "renewable energy" scheme, this is about 11.9%

For the 21st century, from 2001-2018, 11 of the 18 measurements increase by 2.00 ppm or more, or in "percent talk," 61.1% exceeded 2.00 ppm growth in atmospheric carbon dioxide.

If any of this concerns you, don't worry be happy.

In that offshore oil and gas hellhole, Denmark, they are adding wave power to the 9,422 wind turbines they'd built as of last May (the last time I checked the database), "only" 3,232 of which had been decommisioned as of that time.

In 25 years or less, all of the "wave power" machines in Denmark and elsewhere will have tranformed into the stuff reported in this scientific paper: Small Microplastics As a Main Contributor to Plastic Mass Balance in the North Atlantic Subtropical Gyre (Alexandra ter Halle et al, Environ. Sci. Technol., 2019, 53 (3), pp 1157–1164.

Don't worry, be happy.

No one should be compelled to read "science," when we can read happy horseshit about so called "renewable energy" on the internet.

Since 2004, the world has "invested" approximately 2.3 trillion dollars on so called "renewable energy."

This information is here, in the UNEP Frankfurt School Report, issued each year: Global Trends In Renewable Energy Investment, 2018

It's working just great isn't it?

In the year 2017, the combined wind, solar, marine, and geothermal energy scheme grew by 1.21 exajoules.

The use of dangerous natural gas (including that mined in the North Sea by Denmark) grew by 4.19 exajoules to 130.08 exajoules; petroleum by 1.97 exajoules, to 185.68 exjoules.

World energy demand was 584.98 exajoules.

Combined, after 50 years of world wide cheering, the wind, solar, geothermal and marine production of energy has reached 10.63 exajoules.

2018 Edition of the World Energy Outlook Table 1.1 Page 38 (I have converted MTOE in the original table to the SI unit exajoules in this text.)

We're doing just great. Just wonderful.

I wish you a pleasant Sunday.

February 7, 2019

2019 is off to a great start. One of the weekly year to year readings breaks into the top 50.

The Mauna Loa carbon dioxide observatory maintains some data pages, one of which compares current weekly readings with the readings of the same week of the previous year. This record stretches back to May of 1975. There are 2,244 such readings as of this date.

I keep a spreadsheet of this data which allows me to compare (and sort) the data. (I also keep spreadsheets using the monthly and annual data.)

I keep my eye on the top 50 worst year to year increases.

Twenty-four of the top 50 occurred in 2016, an El Nino year. In 2016, the week ending July 31, the worst ever was recorded, 5.04 ppm over the previous year. Of the top 50, 31 occurred in the last 5 years; 37 in the last 10 years, and 40 in this century.

Eighteen readings exceeded 4.00 ppm increases, and of these 18, all but 3 have taken place including and since 2010.

The two post-El Nino years, 2017 and 2018 each produced only one reading in the top 50, and after three weeks of 2019, that figure has been matched.

The week ending January 20 of this year produced the 40th highest reading of the 2,244 readings, an increase of 3.68 ppm over the same week of the previous year, placing it in the 98th percentile for "worst ever."

We're doing just great.

All those wind turbines, solar roofs and electric cars have stopped climate change in its tracks. Or maybe not. No matter, they're cool anyway, even if trillions of dollars thrown at them has had no result. They're great for marketing, and what counts more than marketing? Nothing I think, certainly not that awful thing called "reality."

I wish you a pleasant Thursday.

February 6, 2019

The Structure of Molten Uranium Dioxide.

The paper I'll discuss briefly in this post is this one: Molten uranium dioxide structure and dynamics. (Skinner et al Science Vol. 346, Issue 6212, pp. 984-987 (2014))

The famous "Elephants Foot" produced by the melting of the Chernobyl nuclear reactor in 1986 consists of a mixture of steel graphite, silicates produced by melting concrete and about 10% uranium dioxide which also melted during the event.

The thing has been photographed, even though a range of a meter, the exposure to radiation emitted by it will be fatal in about 5 minutes.

Here's the photograph:

I hope that guy in the picture didn't stay there very long.

The photograph is grainy because the film was being exposed to radiation when the picture was taken.

I personally am interested in what happens when nuclear fuels in a liquid state, since liquid nuclear fuels whether in solution, such as being explored in various kinds of "molten salt" reactors, or (more to my interest) liquid metal fuels, particularly low melting eutectics made using the remarkable properties of plutonium offer certain advantages that solid phase fuels cannot match. One value of these nuclear fuels is that they allow for on line in process separation of fission products. This is, by the way, what happened at Chernobyl. Much of the cesium and other volatile fission products boiled away, contaminating a large area. It is seldom noted that this kind of thing can also be contained, thus lowering the available inventory of fission products for leaking into the environment, while recovering valuable radioactive elements including, but not limited to, radioactive cesium. Radioactive cesium, like many other fission products, utilized in a controlled way, can solve many intractable chemical pollution problems in air and water.

Some time back, in this space, I offered a long involved "thought experiment" showing how the use of radioactive cesium to clean up the air might work: A Scientific Rationale For Pursuing New Immobilization Forms For So Called "Nuclear Waste."

Uranium dioxide has an extremely high melting point, thought to be around 2,865C. Precise measurements are difficult to obtain, since the hot oxide will interact with the materials containing it, reducing the purity of the sample while destroying the container, as happened at Chernobyl.

To avoid this problem, the authors of this paper, which was designed to utilized a very innovative approach. They "levitated" the sample in a stream of flowing (unreactive) argon gas. From the paper's supplementary information:

The aerodynamic levitation method involves floating of the sample on a on a 99.999% purity Ar gas stream inside an Ar filled chamber (21). The sample is then heated from above using a 400W CO2 laser (Synrad Firestar i401). Temperature was measured at the top of the sample using a Chino IR-CAS pyrometer (0.7-0.9 ?m waveband). The liquid UO2 emissivity value of 0.84±0.03 was used in the temperature correction (2) and the error in temperature is estimated to be ~2-3% due to a combination of temperature gradients in the upper part of the sample and chamber window transparency corrections. A brass sheet was placed in front of the area detector to absorb any uranium fluorescence (L-edge ~20keV), while passing >80% of the elastically scattered x-rays (standard corrections were used for attenuation).

Their goal was to learn about the structure of molten uranium dioxide.

From their introductory text:

Nuclear power from fission currently accounts for about 10% of the global electricity supply. Compared with burning fossil fuels, nuclear power has prevented ~64 × 10^12 kg of CO2-equivalent emissions since 1971, corresponding to a saving of 1.84 million air pollution–related deaths (1). Because the majority of currently operating nuclear reactors use either UO2 or mixed oxide fuel (typically 90% UO2), understanding and predicting the behavior of UO2 at extreme temperatures is of great importance to improved safety and optimization of this low-carbon electricity source. Although no experimental structure measurement of molten UO2 has been previously reported, some physical properties measurements (2, 3) and several literature molecular dynamics (MD) models do exist for molten UO2 (4–9). These models, which are often parameterized from solid-state properties, have large differences in their melt structures. The U-O bond length rUO, for example, varies from 1.9 to 2.2 Å between UO2 melt models (4–9). This structural uncertainty results in molten UO2 models with differing physical properties, such as viscosity and compressibility, that are relevant to reactor safety. The present x-raymeasurements, by contrast, find a precise value rUO of 2.22 T 0.01 Å (at 3270 K), which provides a new tool to test the validity of liquid UO2 models.

Here's a nice picture showing the apparatus (as a schematic) and some x-ray data:

The caption:

Fig. 1X-ray diffraction measurements of UO2.
(A) UO2 x-ray structure factors. Above 1300 K, the high-Q region (Q > 12 Å?1) contained no structure. The setup diagram (inset) shows the incident x-rays passing through the collimator (1) and the hot sample (2). The temperature was measured with a pyrometer (3), and exhaust gas was filtered (4). The view through the exit window shows the sample loader (5) and beam stop (6), which absorbed exit window scattering. (B) X-ray pair distribution functions DX(r), generated from the patterns in (A). Dotted lines are from the Yakub MD model (6); red lines (3270 K) indicate the liquid state. As an approximate guide, these UO2 x-ray diffraction patterns consist of pair contribution weightings of 73% U-U, 25% U-O, and 2% O-O (at Q = 0).

What happens when UO2 melts is that the coordination number of oxygens bonded to uranium decreases.

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The caption:

ig. 2UO2 coordination numbers and bond lengths.
(A) U-O pair distribution functions [rTUO(r)] and running coordination numbers [nUO(r)]. Open circles are nUO(r) from the x-ray measurements at 2100 K (black) and 3270 K (red). The above 3-Å U-U correlations also contribute to the measured nUO(r). (B) U-U pair distribution functions [rTUU(r)] and running coordination numbers [nUU(r)]. In both (A) and (B), light gray and light red curves are the rT(r) and the thicker, darker curves are n(r). The dashed or unbroken curves are from the Yakub MD model at three temperatures: 2100 K (dashed gray or black), 3000 K (unbroken gray or black), and 3270 K liquid (unbroken red or pink). The direction of the arrows indicates increasing temperature. The dotted red lines are the n(r) curves from the refined MD model. The temperatures chosen are either side of the lambda transition in the hot solid (2100 K and 3000 K) and the stable liquid state (3270 K). (C) Measured rUO(solid circles) and rUU (open circles), normalized to the 300 K value. The dotted lines are the Yakub MD model. Red circles (3270 K) indicate the liquid state. Liquid UO2 number density at 3270 K is 0.0593 Å?3 (2).

The authors perform some molecular dynamics calculations and structure determination

?width=800&height=600&carousel=1

The caption:

Fig. 3Molten UO2 structure measurements and MD simulations.

Diffraction measurements (red), Yakub and refined MD models (black dashed). (A) The thin, light gray line on the upper pattern is the raw measurement, whereas the smoother red lines correspond to the solid red lines in (B). The inset shows times for 50% of bonds to be broken in the solid or supercooled liquid at 3000 K (light blue). (B) The solid red lines were filtered by Fourier transforming with an r-dependent modification function to reduce unphysical high-frequency noise (13, 19), whereas the solid light gray line shows the unmodified transform. The lower dashed and dotted curves are the UU, UO, and OO partial contributions to the x-ray pattern. (C) Slices from the refined MD simulation (~15 by 12 by 3 Å) showing U-O polyhedra, above and below the lambda transition (2100 K and 3000 K) and in the liquid state (3270 K). The bottom slice shows the UO6 drawn in black and the UO7 in light blue (11).

Here are some brief concluding remarks from the paper:

Portions of the hot solid and liquid UO2 MD simulations illustrate the large oxygen disorder above the lambda transition and the different UO6,7 coordination species that predominate in the melt (Fig. 3C). The structure and optimized interatomic potentials for UO2 allow for accurate atomistic multiscale modeling. The x-ray data are important as an end-member benchmark for models of multicomponent systems, including corium melts and high-level waste glasses (11).

Cool, (or hot) paper.

By the way, I'm opposed to the use of "waste glasses" to dump so called "nuclear waste," since radioactive nuclear materials, albeit limited in the amount that can accumulate by the Bateman Equations.

We ought to be utilizing these materials to solve otherwise intractable problems. Of course, our current generation is too stupid and too paranoid to understand as much, but future generations, one hopes, needing to clean up our mess, dumped on them as an expression of our contempt for the future, will understand as much.

Speaking of the future:

One of the labs to which my son applied for his summer internship was the lab of this paper's authors, Argonne National Lab. He was, however, offered a job at Oak Ridge National Laboratory - his first choice - which he accepted. It's neutron work.

I'm jealous, but very proud of him.

I wish you a nice day tomorrow.

February 3, 2019

Having studied nuclear fuels for more than 30 years, I have a distinct objection to the ethical...

...matrix by which someone can appeal to putative "long term" deaths from so called "nuclear waste," that almost certainly won't happen over the real and observed deaths of 70 million people over the last ten years from dangerous fossil fuel and biomass combustion waste, air pollution. Deaths from air pollution in the last ten years represent more people than died in the Second World War. It is the equivalent of killing every man, woman and child in the UK.

There are literally hundreds of thousands of highly sophisticated papers in the scientific literature, written by highly educated scientists all over the planet on the handling of used nuclear fuels, a valuable resource for future generations when and if ignorance is overcome.

I know the value of used nuclear fuel because I've read, in the last 30 year many, many thousands of them.

People who refuse to be educated and giggle at what they learned in schools are not really capable of entering into a discussion of energy and the environment.

It's very clear that these kinds of people are opposed to opening a science book, never mind a serious scientific paper and in a very Trumpian fashion, shoot their mouths off on sujbects they know nothing about.

Yesterday, I attended a lecture by New Jersey's State Climatologist, David Robinson at the Princeton Plasma Physics Lab's Science on Saturday Series. I made a point of staying after the presentation to thank him for his positive remarks on nuclear energy in the face of so much knee jerk Pavlovian public interest that prattles on about so called "nuclear waste," while dangerous fossil fuel waste is killing 13 people every damned minute.

We are, as of this morning, at Mauna Loa, the carbon dioxide concentration on this planet is 411.02 ppm, whereas one year ago this week it was 407.25. That represents the destruction of the entire planetary atmosphere by energy wastes.

As a person who has devoted long hours of my personal time to the study of energy and the environment, I am appalled by the ignorance of people responsible, which I find to largely consisting of mindless, rote anti-nukes.

Over the years here, I've built this wonderful ignore list for people who clearly lack a shred of moral, intellectual, or scientific sophistication, because after long experience with them, it becomes clear that they are as fond of their ignorance as Donald Trump, and that there's little point in spending a minute more with them.

I clearly need to expand that list now.

I wish you a wonderful life.

February 3, 2019

You know what to do with a dead chemist, don't you?

Barium.

February 2, 2019

A very powerful play, "The Niceties..."

My wife and I saw it last night at the McCarter Theater in Princeton NJ, performed by two brilliant actresses. It's one of the most thought provoking and timely pieces of theater I've seen in many, many, many years:

At an elite East Coast university, an ambitious young black student and her esteemed white professor meet to discuss a paper the college junior is writing about the American Revolution. They’re both liberal. They’re both women. They’re both brilliant. But very quickly, discussions of grammar and Google turn to race and reputation, and before they know it, they’re in dangerous territory neither of them had foreseen – and facing stunning implications that can’t be undone. Written with powerful truth and humor by Eleanor Burgess, this deeply resonant work is directed by Kimberly Senior (Disgraced). The Washington Post hails it as “a barnburner of a play,” adding that it’s “one of the best plays I’ve seen about who gets to tell the story of America, and how.”

The Niceties at the McCarter.

I personally left weeping, with great sympathy for both characters, despite their very bitter reaction to one another.

By the way, if you are in New Jersey and plan to go, there are NO bad seats in the Berlind Theater at the McCarter. Having gone there before, I knew that the $25 seats are just as good as the $80 seats, in fact in our case, 2nd row, stage right, they may have been the best seats in the house.

The playwright, a graduate of Yale, based the play on real events at Yale in 2015 apparently. It was set during the Clinton Trump election which, of course, the country lost.

If you can, see it.

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