Glenn Seaborg

If you had seen Glenn Seaborg in 1929 just when he entered UCLA, you would have been surprised that he looked more like a pugilist or a longshoreman than a future Nobel Prize winner. He had, in fact, worked as a dockworker in LA, but his present job was at the Firestone Tire Company. He was only 17 and decided he'd go to college and study his favorite subject. This was a day when college was actually affordable, and Glenn knew he could keep working at various jobs and complete his studies. It also helped just a wee bit that at that time tuition was free for in-state residents at California's state colleges.

Still his boss tried to argue him into staying. After all, why should a strapping, strong, and tall (6' 2") young man of Glenn's calibre go for such a nerdily major as chemistry? Promises of a better job than his current graveyard shift had no effect, and Glenn decided nope, he'd go to school. But he still sought advice from a phrenologist who felt Glenn's skull and said he was suited for a science career. Of course, as the phrenologist had no doubt learned of Glenn's plans from Glenn himself, giving said advice was not particularly taxing.

After UCLA, Glenn went on to Berkeley where he got his Ph. D. After graduation he joined the faculty first as research associate, then instructor, next to assistant professor, on to associate professor, and in 1946, a full professor. Not counting the hiatus due to the war (at the University of Chicago) he stayed at Berkeley where from 1946 to 1958 he was Director of the Lawrence Berkeley Laboratory.

Glenn's specialty was nuclear chemistry, that is, isolating new elements produced in nuclear reactors. Specifically he created transuranium elements a feat that landed him the 1951 Nobel Prize which he shared with Edwin McMillan. All in all Edwin did the making of the elements and Glenn did the isolation.

Glenn realized all the new elements didn't quite fit in with the usual periodicity of the periodic table. He said there needed to be a new section - the actinides - put in below the lanthanides. This would produce two rows taken out of the table and stuck at the bottom of the charts to save space. Why some people thought this was crazy is difficult to understand as it makes perfect sense. But as more and more elements were made, isolated, and studied, it became clear that Glenn was right. So we now have the two rows.

That doesn't mean, of course, that Glenn was spot on everything. He thought electricity from nuclear power would be so cheap that you couldn't even make a meter small enough to charge for it. Actually electricity that arrives at your home is not always produced by the same method. And whatever the source of your power, the meters calculate the monthly bill quite easily, thank you.

Everyone knows that it was in 1941 (or thereabouts) that Glenn discovered plutonium, the element that is used in atomic bombs and as the ignitor of the hydrogen bombs. Before plutonium, the only atomic bombs could be made by concentrating Uranium-235 which occurs naturally in Uranium-238. You can think of this as the "all-natural" atomic bomb. Since U-235 and U-238 are chemically the same they can only be separated by differences in mass. Usually you make uranium hexafluoride - nasty stuff - and let it diffuse through a membrane. If you start out with 0.7 grams of U-235 per 99.3 grams of U-238 - the usual ratios - you end up with 0.703 grams of U-235 per 99.297 grams of U-238 on the other side. So you need humongous plants to make pound quantities of U-235.

Plutonium was the first synthetically created element and if you sample the environment and find plutonium, then it probably is man-made. However, plutonium isn't synthetic in the sense that it never occurs in nature. Or rather you can find it at certain times in the history of the world, even before man began making nuclear reactors. One interesting place that used to have natural plutonium is in Gabon, Africa. For various reasons, some natural uranium started a self-sustaining chain reaction. Although the ratio of the isotopes is only explainable by the decay of plutonium, there isn't any plutonium left. So based on the half-life of the various plutonium isotopes this "natural" nuclear reactor must have ceased operation about 2 billion years ago.

Plutonium, whether natural or man-made - arises from uranium-238 and is a different element with a different electronic configuration. So it can be separated from the uranium by chemical means. There are a number of ways to finally get your plutonium. The procedures Glenn and his friends developed were based on techniques worked out by the analytical chemists before instrumental analysis took over. At that time to find out how much of one metal you had in a mixture you had to actually fish the metal out somehow and weigh it. So the separation had to be quantitative. Fortunately, the recovered material did not need to be as the pure metal - which is the way gold was (and sometimes still is) assayed. Instead it could be isolated as a chemical compound. This made things a bit simpler.

The method finally decided on by Glenn and his co-workers is based on the chemistry of bismuth. As is usual in these situations, Glenn, as the man in charge of the lab, did not necessarily do the hands-on work. That job went to three chemists who were particularly skilled at microanalysis: Burris Cunningham, Lewis Werner, and Michael Cefola. Also, the actual details differ depending on the source of the information. But you can get the gist of the process.

So how do you get plutonium when it really doesn't exist in nature? It's very simple as Captain Mephisto might have said to Sidney Brand. First you have to make the plutonium. You do this by taking uranium - often as the oxide - and bombard it with neutrons for a few months in a nuclear reactor. You get, oh, a couple of hundred milligrams Pu per kilogram uranium.

(Glenn, by the way, suggested that the symbol for plutonium be "Pu". The more logical symbol would be to use the first two letters "Pl". But he thought it would be a good joke to for it to be pronounced the way young children express displeasure at bad odors. Surely, he thought, someone on the naming committee of the International Union of Pure and Applied Chemistry would scotch the suggestion. But apparently no one caught on.)

Now what you do is dissolve the uranium cum plutonium in nitric acid with added sulfuric acid. The sulfate helps form a complex of the uranium that keeps it in solution. In any case, what you have is your uranium, plutonium, and other "fission" products in the acid. Now you just have to fish out the plutonium.

The success of the process depends on what chemists call the oxidation state of the elements. That is, how many electrons are surrounding the nucleus. If you've taken middle school chemistry, you know that atoms are relatively happy with certain number of electrons surrounding them. In particular plutonium is happy with either 94 electrons - which is the metal - or 90 electrons (the +4 oxidation state) or 88 electrons (the +6) state. You can also get some with 91 electrons (the +3) state but if it's there it tends to stick with the Pu +4. You can convert one form of the element to the other by adding chemical reagents which will grab up the electrons (oxidizing agents) or give them back (reducing agents).

The metals in positive oxidation states are called cations and their charge is balanced by anions - negatively charged ions. (To remember which is which, see the figure below). But the key to the separations is that different oxidation states have different solubilities. Metals - 0 oxidation state - are not soluble in water. The few metals that seem to dissolve in water, like lithium, sodium, and potassium are actually reacting dangerously and violently with it.

But many positive metal ions - are water soluble. And what oxidation state is soluble for one element may not be the case for others. So in principle you can selectively oxidize and reduce the elements and add various reagents to make some drop out of solution while others stay dissolved.

Now there are a number of procedures that are based on what Glenn and his friends did. But which exactly - if any - was actually used in the massive plutonium manufacturing facility in Washington (now Hanford National Lab) is kind of hard to figure out. Even the patents don't necessarily tell us what was done exactly in the actual plant. But the basic procedure is as follows. Once you dissolve the uranium/plutonium mixture into the acid, you add a reducing agent such as sodium nitrite or sulfur dioxide. This does nothing to any Pu+4 that is floating around, but it does gives two electrons to any Pu+6, thus converting it to even more Pu+4. Now with all the plutonium in the +4 state you add phosphoric acid and then some bismuth nitrate.

Now bismuth coming into contact with phosphate will not stay in solution. Bismuth phosphate is, in fact, one of the universe's most insoluble compounds. For instance, if you add 5 pounds of bismuth phosphate to 5 gallons of water, a whopping 0.00000002 grams dissolves. Or to put it another way, if you have a solution of 100 grams of bismuth nitrate in 1 liter of water and add phosphoric acid, 99.999999999 % comes falling out of solution as bismuth phosphate. Pretty much the same thing happens in acid solution if there's not too much acid - that is, you've adjusted the pH correctly.

Now here's the real kicker. It is true plutonium phosphate is not particularly soluble in water. So you could take the Pu +4 solution and add phosphoric acid. In principle, the Pu +4 would precipitate as plutonium phosphate.

But the trouble is that there is so little plutonium in solution that 1) a lot of it would still stay in solution and 2) there would be so little you couldn't find it, even with a microscope.

But if there's a lot of bismuth, the Pu +4, instead of staying in solution, grabs hold of the bismuth phosphate and so also precipitates out of solution with it. That is, the bismuth phosphate is a "carrier" for the plutonium. But the uranium - as the sulfate complex (remember, we added some sulfuric acid) - stays in the liquid. Now you can either filter or centrifuge the precipitate and end up with a mixture of solid bismuth phosphate which, as we said, contains virtually all of the plutonium.

At this point you don't have pure plutonium obviously. It's essentially bismuth oxide with some plutonium contamination. But for all practical purposes you have at least removed the plutonium from the massive amounts of uranium.

Even not counting the bismuth, this process has not produced pure plutonium compounds. There are other "fission" products like thorium and americurium that also precipitate with the bismuth. These you need to get rid of.

So what you do is to redissolve the solids in nitric acid - bismuth phosphate will go into solution if the nitric is concentrated enough - and add an oxidizing agent like sodium bismuthate or sodium persulfate. This changes the plutonium from the +4 state to the +6. Now you dilute the solution to lower the amount of nitric acid. Add since the nitric acid concentration is now less, the bismuth comes precipitating out when you add additional phosphoric acid.

On the other hand, because the Pu+6 is soluble (only Pu+4 precipitates), this time your plutonium stays in solution. Some extra steps may be needed to make sure the other fission products are removed, but in the end, you filter away the solids and you have what is mostly plutonium in solution.

One pass usually doesn't do the the job and you have to repeat the process two or three times. When you get your final solution of plutonium, there are a couple of options. One of the simplest is to add oxalic acid - which precipitates the plutonium as the oxalate salt, or you can add hydrogen peroxide, which precipitates the plutonium as a mixture of the oxide and the peroxide. These solids can be filtered, and you have plutonium compounds that you can turn over to the metallurgists to make plutonium metal.

And as Sydney would say to Captain Mephisto, "I understand."

And Captain Mephisto replied ....

Well, you can watch the movie.

The process that Glenn used in the lab was on - as we mentioned - microgram quantities. Even today the work isn't something you try in your own home. But to actually make useable quantities, Glenn's lab process had to be scaled up to produce about 100 grams a day - in other words by a factor of about 100,000,000.

By normal industrial standards it was a horribly time consuming and inefficient process. Not only did it produce - literally - tons of waste, but the manufacturing had to be done by remote control due to the radioactivity and the hazards of the chemicals. But the plants were soon turning out kilogram quantities of 99.9 % pure plutonium with a recovery rate of 97 %. That was better than the chemists ever thought possible. Glenn had earlier assured the higher ups that the recovery would be at least 50 %.

Glenn, we should point out, was one of the signatory's of the Franck Report. This was a recommendation that there be no use of the atomic bomb unless it was first demonstrated on an uninhabited and "barren" island for selected members of the United Nations. Although the Japanese weren't members of the then fledgling organization, some neutral nations, including Switzerland, were. So the news, photographs, and films of the demonstrations could be transmitted to Japan. The report also warned that the methods of manufacturing a bomb could not be kept secret since the basics of the science was well known. Finally it pointed out that the Russians would be able to develop their own bomb in a few years and that America could not hope to avoid a nuclear armaments race.

The report was filed through channels. It was, the official "target committee" decided, an objective and fair analysis of complex and important issues. But - inevitably - the recommendations of the report were unanimously rejected.

After the war, Glenn continued his research and he and his co-workers discovered a number of other elements. These were americium, curium, berkelium, californium, einsteinium, fermium, mendelevium, nobelium, and, yes, the element now called seaborgium. Once discovered, they were given their names without difficulty - except for the last.

So what was the brouhaha with seborgium? Well, the American Chemical Society - of which Glenn had been president - thought it was time to honor Glenn with the name of a new element. But this seemed to be usurping the authority from IUPAC (pronounced "you-Pack" by the cognoscenti). IUPAC wanted to name elements by the same guidelines of the US Postal Service for putting pictures on stamps. That is, no living persons allowed.

The ACS, though, had already begun using the name (when Glenn's daughter first heard about the newly named element she thought, "My God! My father's dead!"). But the ACS pointed out that naming elements for living people was not - as the rabbi in Fiddler on the Roof said - expressly forbidden. And so it must be all right. IUPAC had no real answer - and they did indeed think Glenn merited such an honor. But they still hemmed and hawed a bit. After all do you want the ACS, an organization that officially named ethyl ether as "1,1'-oxybisethane", naming an element, for crying out loud? But then again it was IUPAC that officially named arsacyclopentadiene as "arsole", pronounced ... well, you can figure out how it's pronounced.

Well, eventually it was sorted out and element 106 is now officially and internationally called "seaborgium".

At the present there are 118 elements so far discovered. Element 118 wasn't officially been named until 2016 when it was dubbed oganesson in honor of Yuri Oganessian, a Russian-Armenian nuclear scientist.

We wonder, though. Will we ever have an element named after ...

It makes you shudder just to think of it.

References

"Glenn T. Seaborg", Encyclopedia Britannica

"Glenn Seaborg's Interview", Stephane Groueff, Voices of the Manhattan Project, http://manhattanprojectvoices.org/oral-histories/glenn-seaborgs-interview

"Glenn T. Seaborg, 1912 - 1999", The Glenn T. Seaborg Medal, University of California at Los Angeles, http://www.seaborg.ucla.edu/biography.html

Nuclear Energy Encyclopedia: Science, Technology, and Applications, Steven Krivit (Editor), Wiley, 2011.

"Plutonium", David Clark, Siegfried Hecker, Gordon Jarvinen, and Mary Neu, The Chemistry of the Actinide and Transactinide Elements, L. Morss, N. Edelstein, J. Fuger, and J. Katz (Eds.), Springer, 2010.