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Sun Jan 22, 2017, 04:44 PM

Spontaneous separation of californium and curium.

The environmental tragedy now commencing in the United States means that future generations will be even more challenged to address severe environmental issues than they would have been had the United States constitution prevented the installation of an insane administration.

The insanity exists however, and those of us who can in the United States should not abandon our pursuit of knowledge, however much science may be threatened by the anti-intellectual bent of the mob that has seized control of the United States in defiance of Democracy.

If we have learned nothing in the last two decades about addressing climate change, it is that so called "renewable energy" cannot stabilize the atmosphere. This is demonstrated by the incontrovertible fact that the expenditure of trillion dollar sums on this failed technology has had no effect whatsoever on the unrelenting increase in climate change forcing gases.

We're at 406,14 ppm this week, 3.52 ppm higher than last year.

Although we have left a great mess for all future generations, one thing that they may not appreciate is that we have left them is sufficient fully isolated uranium to provide for all of the world's energy demands for many generations to come, as well as technology that can make access to uranium inexhaustible beyond several centuries, with rather less than dire environmental impact. A relatively small amount of uranium is capable of eliminating all the world's energy mines, all of the coal fields, all of the gas fields, fracked and traditional, and all of the world's oil fields.

For the overwhelming bulk of this uranium to be utilized, it will need to be converted to plutonium, utilizing, among other things, existing plutonium inventories (including weapons grade plutonium which must be denatured and rendered impossible to use in nuclear weapons.)

Right now, and for the immediate forseeable future, most of the world's nuclear reactors utilize the thermal neutron spectrum which is many ways undesirable, but it's what we have for now, at least until the fine upcoming generation of nuclear, chemical, and materials science engineers can apply their intellects to change this state of affairs, as we must hope they will.

Continuously recycled plutonium in a thermal cycle, according to one reference, (Ref: Nuclear Reactor Physics, William E. Stacy, Wiley and Sons 2001. pg.234) will consist of an isotopic mixture having roughly 8.17% [sup]238[/sup]Pu, 45.10% [sup]239[/sup]Pu,
20.54% [sup]240[/sup]Pu, 18.57%, [sup]241[/sup]Pu, and 7.62% [sup]242[/sup]Pu. These figures show - they are probably only valid as a first approximation - that plutonium can be readily transformed into a form totally unsuitable for weapons use, owing to the heat load associated with [sup]238[/sup]Pu and [sup]241[/sup]Pu which decays in situ to [sup]241[/sup]Am.

However the transuranium isotope distribution will not be limited to plutonium in this state of affairs (which is less sustainable than fast spectrum fission reactors, which can supply all human energy needs indefinitely.) Among the transuranium elements, working from the same reference, only 51% will be represented by plutonium. Roughly 5% will be neptunium, 9% will be americium, 34% will be curium, with smaller amounts being represented by californium and berkelium.

As I noted earlier in a post here, the accessibility of high oxidation states makes the separation of plutonium, neptunium, and americium from traditional used nuclear fuels, almost all of which are based on oxides of the actinides. Neptunium and americium are the key to generating [sup]238[/sup]Pu to eliminate the value of plutonium for weapons diversion.

In the case of americium, however, an intermediate in the production of [sup]238[/sup]Pu is [sup]242[/sup]Cm. The other curium isotopes will also be present, and what's more, inevitably, this curium will also be contaminated with californium. Because of californium's high rate of neutron production, it is desirable to separate it from other elements both to utilize this spontaneous flux, and to simplify the handling of curium for the recovery of its heat.

Neither californium nor curium however exhibit stable higher oxidation states. This means that while they are easily separated from the lower actinides, they are more challenging to separate from one another; in general (especially since in general only small amounts are produced today), one must resort to procedures like chromatography.

All of this is why I read with interest today a paper detailing a spontaneous separation of curium and californium.

The paper is here: Inorg. Chem., 2015, 54 (23), pp 1139911404 "Spontaneous Partitioning of Californium from Curium: Curious Cases from the Crystallization of Curium Coordination Complexes"

Some text from the paper:

Curium plays a central role in actinide chemistry in that it is isoelectronic with gadolinium, and both trivalent ions possess half-filled f7 shells. This allows curium(III) compounds and complexes to be used as benchmarks for comparisons with gadolinium and other lanthanide analogues as well as with both earlier and later actinides.(1) Given the spherical symmetry of the f[sup]7[/sup] configuration and the general perception that both 4f and 5f orbitals are nonbonding, one might expect that gadolinium(III) would be an excellent analogue of curium(III) if the difference in their ionic radii is excluded. In fact, the electronic characteristics of curium(III) diverge from those of gadolinium(III) in a number of respects...


Actually the "general perception" of 5f is not really valid, but no matter.

A little more on uses for curium:

Curium(III) is perhaps the most luminescent of all 5f-element ions and emits characteristic orange light centered near 600 nm.(7) This property is extraordinarily useful in a wide variety of applications that range from solution complexation studies to the environmental behavior of trivalent actinides to biological probes to understanding energy-transfer processes in f-block materials.(7) Changes in the coordination of curium(III) can cause substantial shifts in the photoluminescence peak position and spectral shape.(7) In contrast, gadolinium(III) compounds, while capable of emitting at visible wavelengths, have low quantum yields even when antennas are utilized for energy transfer and are often used as nonemitting hosts in europium(III)- and terbium(III)-doped materials.(8)


Some remarks on separations:

The separation of middle-to-late actinides from one another has been a key challenge for decades in the development of the chemistry of these elements, their use as targets for the production of super heavy elements (i.e., transactinides), and advanced nuclear fuel cycles for separating lanthanides from actinides. Studies of the stability constants of trivalent lanthanides and actinides with α-hydroxyisobutyrate show that a monotonic trend exists with lanthanides.(14) However, with diethylenetriamine-N,N,N′,N″,N″-pentaacetic acid, this trend is not preserved; curium binds more weakly, and californium more strongly, than expected.(14, 15) These early studies were already suggestive of a change in chemistry occurring at californium that continues through mendelevium.(14, 15)

We recently communicated a few features of the curium(III) tris-chelate, 2,6-pyridinedicarboxylate (dipicolinic acid, DPA) complex, Cm(HDPA)3, as a part of a comprehensive study that compared middle actinides with californium.(16-18) Herein, we substantially expand on our analysis of this complex as well as elucidate the structure and properties of the bis-chelate complex [Cm(HDPA)(H2DPA)(H2O)[sub]2[/sub]Cl][sup]+[/sup].


They ran some crystallizations and to their surprise found that the crystallization process lead to the separation of tiny amounts of californium complexes from curium complexes.

The collection of photoluminescence spectra from groups of crystals revealed that the colorless crystals of DPA that cocrystallize with the bis-chelate luminesce green, as shown in Figure 4. Collection of this luminescence spectrum showed that the green luminescence is superimposable with that of Cf(HDPA)[sub]3[/sub], including the fine vibronic structure (see the Supporting Information).(16) Single-crystal X-ray diffraction studies demonstrate that these crystals are ostensibly just DPA. However, it must be kept in mind that crystal structures are averages of the total composition of the crystal and are largely insensitive to trace doping.(31) However, they are clearly doped with low levels of Cf(HDPA)[sub]3[/sub], . Dissolution of the crystals followed by energy-resolved liquid scintillation counting of californium in the crystals reveals doping levels of 37(5) ppm. The error on this number represents the deviation in the dopant levels between crystals and supports essentially constant doping levels from crystal to crystal. Crystals were also cut and broken, and the lack of significant variation in the photoluminescence intensity of the interior versus exterior of the crystals reveals a relatively uniform distribution of californium throughout the samples. This level also indicates that californium is concentrated within the DPA crystals because the californium levels in typical 248Cm samples are ∼1 ppm (or less).


Here's the picture of the crystals:



Esoteric, I know, but cool. They'll need to know these sort of things in the future if they wish to save themselves from what our irresponsibility has done.

Enjoy the coming week.

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Response to NNadir (Original post)

Sun Jan 22, 2017, 04:48 PM

1. Didn't really understand about 99% of this but,

It sounds really cool!

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Response to dhol82 (Reply #1)

Sun Jan 22, 2017, 05:07 PM

3. Thanks. It is really cool. Actually...

...in recent years I've come across some old work from the 1960's which suggests some even cooler approaches to separations in nuclear chemistry, also spontaneous, and also on line, without even removing the bulk of the fuel from a reactor type that can operate a very high temperatures, temperatures suitable for water splitting cycles, neutralization of chemical wastes, water recovery and high thermodynamic efficiencies where the goal is simply to produce electricity.

They didn't really have the materials science knowledge in the 1960s to go further with it, but we have that knowledge now.

My youngest kid is graduating from high school this year and has been accepted to some pretty good materials science engineering programs, and I'm trying to interest him in learning more about this so it doesn't depart with me when I depart this earth. I keep telling him to go into refractories, and I hope I'm making progress.

If I'm right, this sort of thing could really save the day, so much so that it might be able to actually meet the very, very, very, very, very difficult challenge of removing] carbon dioxide directly from the atmosphere.

I hate the world I'm giving him, but I have high hopes for my son, and his very bright friends who I've met, to do better than we did.

Thanks again.

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Response to NNadir (Reply #3)

Sun Jan 22, 2017, 06:02 PM

6. It sounds like very exciting work!

Hope your son follows your advice.

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Response to NNadir (Original post)

Sun Jan 22, 2017, 05:00 PM

2. Once we learn to safely manage PWRs, maybe we can get more exotic.

 

All this has to be done perfectly, no mistakes, no mishaps. That means a big budget, and a big government agency, and scrupulous oversight.

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Response to HassleCat (Reply #2)

Sun Jan 22, 2017, 05:17 PM

4. PWR's are already the world's safest, by far, energy production machines, by far.

Seven million people die each year from air pollution, about half from fossil fuels, and half from biomass utilized by the world's poorest citizens, about whom we in the West couldn't care less.

In more than half a century of PWR operations, the combined loss of life from all the operations of all the PWRs and BWR's on the surface of this planet doesn't equal the loss of life that will take place in the next two hours from air pollution.

I wish that people would be concerned about real loss of life, rather than their imagined losses of life from radiation that they're always offering up in their paranoid little fantasies, or their silly remarks about Fukushima and Chernobyl for instance.

As the world famous climate scientist Jim Hansen pointed out in his famous paper a few years ago, nuclear energy saved more than 1.8 million lives that other wise would have been lost to the normal operations of dangerous fossil fuel plants. He included Fukushima and Chernobyl in his analysis.

That number might well have been in the tens of millions, were it not for the selective attention of anti-nukes, whose dangerous ignorance has been a great crime against all future generations.

Prevented Mortality and Greenhouse Gas Emissions from Historical and Projected Nuclear Power (Environ. Sci. Technol., 2013, 47 (9), pp 48894895)

We like to pretend on the left that all of the ignorance resides on the right. I hate to say it, but it's not true.

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Response to NNadir (Reply #4)

Sun Jan 22, 2017, 05:49 PM

5. Safer than others is not good enough.

 

They have to be perfectly safe, and we know they're not. Fixing that will require some changes and commitments I don't think we're ready to make.

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Response to HassleCat (Reply #5)

Sun Jan 22, 2017, 06:26 PM

8. Listen kiddie, the contention that it's OK for 70 million people to die every ten years from...

air pollution because some idiots somewhere think that nuclear energy and only nuclear energy needs to be perfect or that everything else can kill at will, is so morally and ethically absurd that it's well, Trumpian, in the depth of its ignorance.

I would suggest that anyone who thinks that way is bordering on criminal.

Every ten years, more people die from air pollution than died from all causes in World War II, combat, bombings, genocide, starvation.

This is fine because nuclear energy is not "perfectly safe?" Do you have any idea what you're saying? If you do, well, I don't think there's much use in even addressing you.

Before giving up on what may be a very poor excuse for a human being, let me say this though:

Now I have never met, not once, an anti-nuke who is even remotely scientifically literate. It's very clear that most of them have never opened a science book or a scientific paper in their lives.

Nevertheless, if one does read science, one can glean moral messages therein. For example Gates foundation funded an exhaustive study of the causes of human mortality and disease soliciting the input of hundreds of health care professionals and health scientists. The figures examine in fine detail what kills people.

Lancet 2012, 380, 222460 A comparative risk assessment of burden of disease and injury attributable to 67 risk factors and risk factor clusters in 21 regions, 19902010: a systematic analysis for the Global Burden of Disease Study 2010

(For air pollution mortality figures see Table 3, page 2238 and the text on page 2240.)

Nuclear energy doesn't even appear on the list as a risk. If that's not as close to perfect as is possible, I don't know what is.

800 people die every hour from air pollution. Some of them are killed by lung cancer. Have you ever watched some one die from lung cancer? I have.

God you're cold!

This sort of contempt for science is one reason that an awful person like Trump can end up in the White House.

People who accept the disastrous because they seek perfection are not worthy of respect. This conversation is concluded.

Enjoy the week.



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Response to NNadir (Reply #8)

Sun Jan 22, 2017, 06:32 PM

9. I'm not a scientist.

 

But I was a reactor operator in the navy.

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Response to HassleCat (Reply #5)

Sun Jan 22, 2017, 11:33 PM

11. What on Earth is *perfectly* safe ? Coal ? Oil ? Gas ? Electricity ? even renewables ?

Every form of energy has its own particular hazards, and particularly when stored in concentrated form. Coal kills miners on a regular basis, as well as the environment. Gas lines blow up with alarming frequency. Electricity kills many people every year, but usually one at a time, so it gets less notice. Dams collapse, and also lead to methane emissions from decaying organic sediments. Hell, life is not perfectly safe. The best available can always be improved on, and "better than others" is the process by which inferior technologies are rolled over to make way for better ones, whether the improvement is marginal or paradigm-shifting. Expect perfection and you will always be disappointed; be pragmatic and take what you can get for now, but work for better in the future, and you will almost always see your expectations met, eventually.

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Response to HassleCat (Reply #2)

Sun Jan 22, 2017, 06:03 PM

7. Sadly, that doesn't sound like it's going to happen any time soon

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Response to dhol82 (Reply #7)

Sun Jan 22, 2017, 11:25 PM

10. I dunno ... "American Carnage" Trump may very well sign any bill that says "nuclear" on it.

If scientists and funding agencies are shrewd about it, they could really loosen the ol' purse strings for nuclear research.

Yeah, I know, probably wishful thinking. But who knows ?

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Response to NNadir (Original post)

Mon Jan 23, 2017, 12:05 AM

12. 34% Curium is kind of mind-blowing.

None of the transuranics were known before the 20th century. Now we're manufacturing them in bulk, and using Americium in common home smoke detectors. Not something I reflect on that often, but every now and then it really hits me that we've basically added most of a full (extra long!) row to the table Mendeleev knew. U and Th were pretty lonely down there until 1898.

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Response to eppur_se_muova (Reply #12)

Mon Jan 23, 2017, 07:39 AM

13. Well, we are not manufacturing curium on that scale now. The reference simply reports...

...a calculated outcome for a continuous recycling approach to plutonium utilization in thermal reactors.

I have calculated that the world inventory of plutonium, weapons and reactor grades included, corresponds to about 40 exajoules of energy if fully fissioned. This is not very much. However in a breeder situation, necessarily fast, except if we also incorporate thorium into a number of cycles, each year we would have more plutonium than the year before.

Curium does not accumulate anywhere nearly as fast in either thorium (thermal) cycles nor in plutonium fast cycles. In fact significant amounts of the curium, as well as americium and neptunium directly fission in a fast spectrum.

Unfortunately all of the commercial fast reactors that have operated have been sodium cooled reactors, requiring reprocessing of the fuel contained in rods. This is less than ideal. Many of the designs advanced as small modular reactors are "breed and burn" reactors.

These are designed to run for decades without refueling.

Even these have not fully explored the universe of possible reactors for safe plutonium utilization.

Thanks for your comment.

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