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Sat Oct 20, 2018, 11:55 AM

A time when plutonium was utilized to model the lanthanides instead of the other way around.

In recent years I've been thinking about liquid plutonium metal quite a bit, as I reconsider the wonderful LAMPRE nuclear reactor that operated in the early 1960's at Los Alamos. I consider that this type of reactor, which was not pursued further back then, not only for funding and political reasons, but probably in consideration of materials science concerns, actually has many wonderful features that should be reevaluated given advances in Materials Science over the last half a century.

Of course, not much has been written on the subject of liquid plutonium in recent years, as the world has become enamored of dangerous natural gas, the external costs of which will be dumped, with contempt for every human being who lives after us, on all future generations.

If one is interested in learning about the properties of liquid plutonium and its eutectic alloys, generally one needs to refer to older literature, sometimes very old literature, to learn things about its properties.

The lipstick on the dangerous natural gas pig is so called "renewable energy" which is not really "renewable" owing to its dependence of somewhat exotic materials or toxic materials with high environmental impact. In particular, the popular forms, solar and wind, were they not still trivial forms of energy, which they are, would now be recognized as obviously unsustainable.

This is why I personally regard nuclear energy and only nuclear energy to be the last best hope for addressing climate change, not that anyone on this planet is willing to be inconvenienced by climate change unless their vacation beach house is destroyed.

One of the most prominent classes of materials utilized in the so called "renewable energy" industry - as well as the related and equally as useless electric car industry - are the lanthanides.

Today, access to plutonium is somewhat limited, and some scientists writing about it do experiments in which they choose a lanthanide to model the behavior of plutonium, usually cerium, since it exhibits two of plutonium's oxidation states, +3, +4, (but not +5, +6 and the suspected but unproved +7 and +8 states) and because it is trivial to order cerium compounds from a catalog, and not trivial to order plutonium.

The separation of the 14 lanthanides from one another remains until this day challenging, because most, with the exception of cerium, europium, which has a well defined +2 state, and a few others in non-aqueous systems, all exhibit only the +3 oxidation state under normal circumstances. This difficulty, although now addressed widely on an industrial scale, is responsible for the high external cost of the purified lanthanides, most of the external costs being borne by relatively poor people in China, which is the world's main source of lanthanides.

Lanthanide chemistry was pretty much a curiosity in the mid-20th century, and much of the progress made in it was an outgrowth of work performed beginning with the Manhattan Project, which was a nuclear project. The prominent presence of lanthanides in used nuclear fuel also drove interest in these elements. When I was a kid, and took high school chemistry, the only mention of them I recall is, "they're there, at the bottom of the periodic table, just above the actinides." I don't believe anything was said about their chemistry.

Today lanthanide chemistry is well understood, and anyone who wants to learn about it and has access to the scientific literature can easily find out lots and lots of stuff about it, should one be interested. (I am.)

But in 1963...

I've been thinking about the behavior of gases in liquid plutonium this week and an issue with this behavior in a fluid dynamics sense is the viscosity of liquid plutonium, which is higher than most liquid metals. Digging through my files I came across this old paper:

The viscosity of liquid plutonium, predicted from a general relationship between the activation energy and melting points of metals, and the experimental data (Grosse, J. Inorg. Nucl. Chem. 25, 1, 1963, 137138)

Cool text from it:

Recently, the viscosity of liquid plutonium in the range of 648-950C has been measured at the Mound Laboratory. Since plutonium is the first actinide element for which experimental data are available (no data are available even for the lanthanides!) it is of interest to compare empirically predicted values with the experimental data... The agreement is quite satisfactory and leads one to expect satisfactory results with the lanthanide metals.

A cool, if obscure, point from the history of science.

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