What's a Decommissioned Gaseous Diffusion Plant?

[Sal]

I change jobs about every 18 months, so I know it's difficult to keep up with what I'm doing at the moment.  You would be forgiven if you were to not know what I do, so let's start with that.  Right now, I work with a team that assesses hazardous environmental chemicals, either naturally-occurring like radon and manganese, or manmade and industrial releases, for potential health impacts on the community. Part of this includes radioisotopes and nuclear hazards.

I had the opportunity in 2017 to visit a decommissioned gaseous diffusion plant in mid-deconstruction. I thought it was pretty neat, and thought some of you might think so, too.

Disclaimer upfront: We were not allowed to bring any kind of electronic device inside the facility other than the radioactivity monitors we were given, so I don’t have any pictures of my own. However, a lot of this information I’m going to share is available online, so I’ll pull/source photos from there.

First things first…



What’s gaseous diffusion?

Perhaps this comes as a shock [/sarcasm]: I am not an engineer or a chemist or a thermodynamicist. That being said, I understand the basics and I will explain the process to the best of my understanding.

Per the All-Knowing Wikipedia, “gaseous diffusion is a technology used to produce enriched uranium by forcing gaseous uranium hexafluoride (UF6) through semipermeable membranes. This produces a slight separation between the molecules containing uranium-235 and uranium-238.”

Going back to high school chemistry for a minute, isotopes are different versions of a chemical element with varying numbers of neutrons (the parts of the atom’s nucleus that have no charge). U-235 and U-238 are isotopes of uranium. Easy peasy. Natural uranium (Unat) - being exactly what you think: uranium found in nature - is found almost entirely (99.3%) as isotope U-238, and only slightly (.7%) as U-235. There’s at least one other isotope I’m not getting into because it’s not relevant to this. Anywho, when you hear the term “enriched uranium”, that refers to Unat whose composition has been altered to yield uranium with a higher U-235 percentage. U-235 is the stuff that humans use for nuclear power, whether weapons-grade (highly enriched, 20-85% U-235) or reactor-grade (low enriched, <20% U-235). Why this isotope? Unlike 238, 235 is able to sustain a fission chain reaction. That’s the process that makes the energy whereby one nuclear reaction causes a self-propagating and exponential series of subsequent nuclear reactions, but I didn’t fully research it to tell you anything beyond that so I’m going to drop this here.



look at these Basic Beckys

There is more than one method to go about enriching uranium, and one of those is - yep, obviously - gaseous diffusion. Gaseous diffusion operates on the basis of Graham’s Law, which is that gas with a higher molecular mass will pass through a semipermeable membrane (effuse) more slowly than one with a lower molecular mass. The equipment used to complete gaseous diffusion is called a stage and it is comprised of:

1. A large metal cylindrical tank inside which the magic science happens. One gas goes in but only two may leave. Or something.

2. The semi-permeable barrier which is inside the tank.

3. A compressor used to pressurize the gaseous molecules and force them through the stage.

4. A heat exchanger so it doesn’t get too hot and go boom (compressing gas heats it up).

5. Lotsa Cold War-looking science pipes and industrial knobs.

UF6 is used as the starting raw material. It’s got uranium in it, so we’re off to a good start, but remember that the uranium atoms in each of the UF6 molecules are mostly isotope 238 with just a tiny amount of 235 sprinkled in. What we want to do is turn that tiny sprinkling into a hefty portion.

Why do we use UF6, by the way, and not some other kind of uranium-containing molecule? Because UF6 is the only uranium-containing molecule volatile (read this as: vaporizable; able to be sublimed; in the gaseous state of matter) enough to be used in this process. It is used because it is the only option. Seems valid.

The compressor applies pressure to the UF6 gas which pushes it through the semi-permeable barrier inside the big tank. As it moves along, strong and powerful U-235 atoms, which are just barely smaller than SAD very low energy U-238 atoms, escape through the almost incomprehensibly tiny pores in the barrier and into the lower-pressure chamber inside the tank. The enriched U-235 gas is then sent through one tube and the depleted U-238 gas is sent through a separate one. Probably to the gulags for being so useless.


Like this.

Cool! We’re done! …Right?



These two atoms are almost the same size. I mean, you have a difference of a few neutrons. A neutron isn’t even a whole atom. It’s part of an atom. You have a size difference of part of an atom. Some freeloading U-238 atoms are going to cross the semipermeable barrier and hitch a ride in the enriched gas tube. For this reason, the gas must pass through multiple stages and repeat the process over to enrich it more and more until you have a U-235 content than can sustain a fission chain reaction. This series of stages is called a cascade.

That was more information than I meant to dump. My bad. Hopefully you found it as neat as I did!



Portsmouth: A Background

The Portsmouth plant was commissioned by the US Atomic Energy Commission (AEC) in 1952 to be built somewhere in the Ohio River Valley. In August of that same year, the AEC decided on Pike County, OH; the chosen location had a large water source needed to cool down the cascades during pressurization, a reliable power source, and adequate personnel. Goodyear (the tire people) was chosen to be the operating contractor in September while plant construction went to Peter Kiewit Sons’ Company. This whole thing was going to cost somewhere in the ballpark of $2 billion to build, and it was going to be completed in such a way that each process building was going to come online as it was finished, meaning part of the building would be in use while others were still being built.

This place is massive. The aerial view below doesn’t do it justice. The original plot of land on which this thing sits is 4,000 acres and, when construction was complete, contained 25 miles of paved roads and more than 20 miles of railroad. The plant was constructed with 100,000 tons of structural steel and so much concrete that a concrete batching and mixing plant was constructed onsite to speed things up. The three main process buildings which house the diffusion cascades contain hundreds of miles of piping and tubing, all of which had to be coated because UF6 is corrosive. A water pumping station to cool the processes and a power station to power it were also built onsite. In addition to the three main process buildings, there was also a cafeteria, administrative offices, warehouses, utility buildings, fire department, water treatment facility, and hospital. Like I said, massive.



BIG BOY!


Construction on Portsmouth was completed (at only $750 million - a real bargain compared to the initial $2 billion estimate) in 1956 with the first units going online in ‘54. It operated under Goodyear from startup until 1986, Martin Marietta from 1986 until 1995, and Lockheed Martin with the merger of Martin Marietta and Lockheed until its closure in 2001. When still in use, Portsmouth had a peak demand of 2,100 megawatts of electricity, sucked 40 million gallons of water daily for cooling processes, and burned 7.5 million tons of coal annually.

All this to produce 8.3 million separative work units for the nation’s defense programs as well as fuel for nuclear power plants.

It was shut down in 2001 when operations were consolidated with the Paducah plant in Kentucky. The US Enrichment Corporation (USEC), for a while, worked on resuming a gas centrifuge operation on the Portsmouth site that had been attempted in the 1960s, but construction was halted in 2009 when the US Department of Energy would not guarantee a loan of $2 billion. As far as I know, the plan is still to construct and operate the centrifuge facility, but it’s still pending.



What does decommissioning this plant entail?

Decontamination. A looooot of decontamination. 60 years’ worth of industrial solvents and spent UF6 canister levels of decontamination.

The EPA currently has Portsmouth listed as a Superfund site. Superfund, or the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) is a program is a program that forces parties responsible for the contamination to either perform clean-up operations themselves or to reimburse the EPA for doing it. It tries to prevent situations like the Love Canal disaster in which industries throw their toxic waste and byproducts wherever - into soil, drinking water, etc. - and take no responsibility when people later become sick from it.

There’s also the obvious demolition duties that will need performed. Several buildings and one power plant have already been torn down, but there is still a lot left to be completed.  Decontamination and decommissioning are called D&D.  Not the one with the dice, ya nerd.

We got to tour a new landfill that was being constructed on-site. The specs for this thing were impressive and the super specific ways that all the scrap metal and concrete and other things that would go into it had to be folded and laid into the cells to make sure everything fit as planned was kind of mind blowing. I guess it makes perfect sense. I just never thought about landfills before.

The hope for all this effort is for the land to eventually be usable by another industry, possibly even a power plant.



That’s cool and all, but what’s it like in there 17 years later?

A plant that has been semi-shut down for almost two decades is exactly what you’d expect it to be like. I say semi-shut down because, as you could guess, deconstructing a nuclear energy plant takes some effort, and there are still people who work there.

The three main processes buildings, X-333, X-330, and X-326, make up the bulk of the footprint and contain a combined 7.73 million square feet of floor space. We went inside one, the X-333. This was the first building in the process when the plant was in operation; the cascade would have started there, so this is where the UF6 would enter and where the uranium would be totally unenriched. It’s basically been gutted of all the cells and most of the cradles holding the cells, so what you’re left with is this huge, empty concrete and steel hangar sort of thing. There are holes in the roof and it was pouring rain into the building when we visited, and it’s barely air conditioned. Interestingly, there are sections that are fenced and/or barb wired off, and big roped-off areas with warning signs like “this area contains PCE” (I don’t know how the PCE fumes know to stay behind the ropes, but....)

The official Portsmouth Virtual Museum has lots of good photos, both historical and more recent.  I'm going to *ahem* "borrow" some from them for these purposes.


A panoramic photo of X-330 in 2010 taken from the catwalk.  This is the best representation I found of what we saw.



X-333 in 1991. This is how it pretty much still looks today.



Also X-333.  These tanks are probably empty now, but this shows some of the tubing/piping.



This soon-to-be-pensioner laughs maniacally as he loosens the seals on the spent UF6 and releases the radionuclines. Checking seals on UF6 containers. I posted this one for scale on the containers.



The level of PPE you need to be in the building varies depending on where you are. The part we visited were low risk areas, so we got by on shatterproof safety glasses, hard hats, and steel-toed boots - plus the radiation monitors, like I said. But we definitely did wave hi to some people deeper in the bowels of the building who were in full hazmat suits. The bright yellow sci-fi ones like you’re imagining, yep.

One of the neatest things I saw was that the buildings are so large that the workers ride bikes inside.

Outside was pretty spooky, too. I think the weirdest part had to be the stacks of empty UF6 containers all neatly organized and labeled. They weren’t fenced off or anything, just kind of off to the side on asphalt slabs. There was a little nylon rope sort of thing around them with radioactive materials placards every ten feet or so. Just chilling out there.

The old area for where the final enriched uranium would be received by the military still stands, and it was pretty nifty, too. Just two concentric chain link fences surrounded by a whole lot of razor wire under a kind of awning thing. You’d think it would be more than that. At least I did.

Here are some things you can see in the aerial photos from :


Power station and spent UF6 containers behind process building X-330.



A closer look at just how many UF6 containers there are with the water tower for scale.  Note: these are stacked at least two high and this is not all of them.



The water treatment plant.



The train.  Choo choooo....





Yeah, that looks pretty cool.  I'm honestly kind of jealous and wish my work-sanctioned field trips were as fun as yours, Sal.

This thing won’t go cold and dark for another few years, so go take a tour while you can. I haven't seen any information for 2018 yet, but there were public tours offered one Saturday each month by the Department of Energy in 2017.  There’s a virtual tour available for those of you too far away, but Sal already told you all the good parts. Eh.