Also published here.
When most people think of “the Cold War nuclear arms race”, they think of Reagan and Gorbachev, Kennedy and Khrushchev, treaties and international summits, Presidents and Premiers. It all starts to seem rather abstract: something from the past, to be relegated to history books and news archives.
They probably don’t think of the remote sites around the United States, consisting of laboratories and manufacturing facilities, the complex that made The Bomb possible. And unless you’re very familiar with this complex, or you’re a resident of the Pacific Northwest, you may not know about a remote part of Washington State known as the Hanford Site.
To make nuclear weapons, you need to actually make weapons-grade plutonium, or plutonium-239 (239Pu). The Hanford Site’s role in the Cold War was to produce most of the plutonium for the US nuclear arsenal; at the peak of the Cold War, we were producing about 28 bombs a day, and had as many as 31,255 nuclear weapons. The facilities built at the 586 square mile Hanford Site included nine nuclear reactors, several spent nuclear fuel processing facilities, support laboratories, and of course, large underground tanks for waste storage, in an area of the site known as the “tank farms”.
It’s the rather complex issue of Hanford’s tank waste that I’d like to address today.
When telling the story of the Cold War, the part that often gets neglected is that the extraction, processing, and purification of plutonium at the Hanford Site was anything but a neat, clean process; in fact, it resulted in a rather extraordinary amount of extremely radioactive and chemically dangerous waste. This waste is absolutely nothing like commercial nuclear waste, and its management has been one of the biggest challenges the US nuclear weapons complex, and consequentially, the Department of Energy, has ever had to deal with.
In a previous article, I introduced you to the Hanford Site, and explained that in the early 1990s, I’d worked as a radiochemist in one of the laboratories in what is known as the “300 Area” of the site. Among other things, I analyzed the plutonium content in spent fuel sludge, as well as in extremely dilute samples of tank waste. Since plutonium production had only stopped in 1988, and the Cold War had only ended a few years later, the site still had somewhat intricate security zones, and thus us students didn’t have access to much more than the laboratory where we worked.
As a result, the tank waste and the tank farms took on a sort of legendary quality for us. That was the part of the site where our samples came from; it was one of the reasons the site was getting an increasing amount of negative attention due to media reports on the fact that the tanks were leaking, and the government had failed to report the leaks and the spreading contamination. In short, the tank waste represented not only fascinating chemistry, but an environmental crisis that had to be handled… and it was all underground, where we couldn’t see it, on a part of the site we just knew about because it was on a map.
At the time, I remember thinking that, like many of the site’s other problems, the tank waste problem was intractable. How could they possibly manage to safely transfer the waste from the leaking tanks to safer ones? Would it ever be possible to permanently store the waste in a way that it couldn’t cause any more environmental damage? In the years since I worked at the site, I followed government reports and news media updates on the site, but was not satisfied with the answers I got.
I decided that it was time to visit the Hanford Site again, 17 years after I’d worked there, and ask all the technical, scientific, and logistical questions I’d had for so many years. For the sake of simplicity, I decided that, given the extent of the cleanup effort at the site, I’d focus only on tank waste management, and address other site issues on a separate visit/in a separate article.
First of all, I’d like to point out the biggest difference between the early 1990s and 2010: transparency and openness with the public. In fact, you can take a site-wide bus tour, and they’ll answer as many questions as time allows. Changing security requirements have made this possible, among other things; I highly recommend the tour, in fact.
As media, and someone with a technical background, I was very pleased to be able to get a more detailed and extended tour of the site, and I’m very grateful to the people at the Office of River Protection, the tank farms, and the DOE for making it possible. My tour spanned two days, and gave me a pretty good idea of the progress they’ve made, the tools they use, the difficulties they’re facing, and what they hope to achieve in the future.
Location of the tank farms, and an overview of plutonium processing
Here’s a general overview of the Hanford site, showing the location of the (now-decomissioned) reactors, as well as the tanks, which are located in the “200 Area” of the Hanford Site:
Plutonium production started at Hanford with the B reactor and one type of chemical extraction process in 1943. Over time, the site expanded to include nine reactors, and the chemists had settled on a plutonium purification process known as PUREX, after trying two previous methods of purification, with somewhat different chemistry. Here’s the overall scheme, greatly simplified:
The liquid waste from the extraction process was very caustic and highly radioactive, so it was stored in 177 underground tanks. 149 of these are single-shell tanks, with storage capacities between 55K and 1 million gallons. 28 of these are double-shell tanks, with storage capacities of 1 million to 1.25 million gallons; these were built later than the single-shell tanks, and are more stable. The total amount of waste in the tanks adds up to 53 million gallons.
Although the waste going into the tanks was originally a liquid, over time, chemical reactions have taken place causing solids to form as well as gases. Because multiple plutonium extraction processes were tried, the content of the tanks is anything but simple. The solids can be as hard as cement or as sticky as peanut butter. The degree of radioactivity is daunting as well; the waste cannot be handled without extensive shielding. In other words, you can’t just suck the waste out of the tanks and put it someplace else without adequate planning, preparation, and care. It’s really dangerous stuff.
Let’s Take A Tour
The scale of the problem: standing inside a waste tank
No, of course you can’t stand inside a real tank at Hanford, but you can stand inside the Cold Test Facility, which was the first stop on my tour of the site.
The Cold Test Facility (CTF) is a mock-up of a 660K gallon waste tank at Hanford. I don’t think I had a real idea of the scale of the waste, the sheer amount of it, until I stood inside the facility (remember, there are over 100 actual waste tanks at Hanford). The CTF stands 27 feet high, and is 75 feet in diameter. It is used to simulate the situations workers encounter when dealing with the waste in the “hot” (radioactive) tanks; instead of trial-and-error with extremely dangerous material, workers can train to use the retrieval techniques on “cold” (non-radioactive, inert) material. For example, one of the things I saw in the CTF was a very thick, cement-based slurry that had been produced in order to simulate the consistency of some of the tank waste workers would ultimately encounter.
One of the tools they’ve recently tested in the CTF is something called a Mobile Arm Retrieval System, or MARS. It’s a robotic arm that has been designed to fit into one of the rather small openings in the tanks, and has a telescoping capability, so it has a wide range of motion inside the tanks. It has not yet been deployed, but the CTF makes it possible to eliminate sources of error before putting it in a highly radioactive environment. (Click here for a news article about the MARS.)
Tank waste retrieval: the C tank farm
Our next stop was the C tank farm, where they were staging a sluicer, getting it ready to insert into one of the single-shell tanks. Sluicing is the use of a high-pressure jet of liquid to break up the solids in the tank so they can be vacuumed/pumped out, and transferred to one of the more stable (non-leaking, higher technology) double-shell tanks. I was told that they use actual liquid tank waste to break up the solids; in other words, they’re not producing more waste in the clean-up effort. I was able to watch a video tape of the sluicing process; they said that the radioactivity is so high in the tanks that they have to replace the cameras regularly. Everything is done by remote control, and a typical tank retrieval takes many months of planning as well as considerable training.
I should point out one thing that has made a huge difference at the Hanford Site, which you can see from the banner on the tank farm fence:
The Hanford Site received quite a bit of Recovery Act funding, which has helped accelerate clean-up efforts, especially at the tank farms. They also said that Energy Secretary Steven Chu has been very interested in the clean-up; one of the people I spoke with said that in his twenty or so years working at Hanford, Chu has been the most involved Energy Secretary he could remember, and that it was much appreciated.
The real thing: walking around S tank farm
I had to be fairly well sealed inside my protective suit, since there is potential surface contamination at the tank farm they wanted to show me.
It was quite fascinating to actually be able to walk across the ground, many feet above where some of the more notorious tanks were, including the infamous “burping” tank, 101-SY, which was producing large bubbles of hydrogen and was a topic of great concern when I was working at the site in the 1990s. The tank has since been emptied, and the special equipment designed to monitor it has been shut down, but it was still fascinating to look at. Each tank has different chemistry, and different problems from the next tank; each time one is emptied, they learn something that can be applied to future situations. In other words, the more the learn, the faster the cleanup effort will go.
One of the main criticisms of the cleanup effort is that it’s behind schedule and over budget. They told me that when the Tri-Party Agreement was signed in 1989, it set milestones that were based on incomplete knowledge of the complexity of the tank chemistry and content. In other words, milestones had to be set, but they were somewhat arbitrary, and they didn’t realize exactly how complicated the cleanup and tank retrieval operation would be. The first tank retrieval they did, in 1998, took years of preparation and planning; as a former radiochemist, dealing with very dilute tank waste, I can tell you that it was still quite “hot”. The concentrated stuff is literally deadly. In other words, I can’t begin to emphasize enough that “tank waste clean-up” is very much misunderstood by the general public. It’s one of the most difficult chemical, engineering, and logistical jobs you can imagine. Setting arbitrary milestones was the best they could do in 1989; now, they’re making progress toward an actual end-point for the waste, which is what I learned about on the next day of my tour.
The Waste Treatment Plant: turning it all to glass
I’d read for years that one of the possible solutions for the Hanford tank waste was to literally turn it into glass, or vitrify it. The idea was only in the testing phases when I was working at the site, but now they’ve begun to build a huge (65 acre) waste treatment complex. It’ll essentially work like this:
The nuclear and chemical wastes will be delivered from the underground storage tanks (see Tank Farms link) to the Vit Plant through a series of underground transfer lines. Called “pipe in pipe,” the system ensures that there are no leaks of materials during the transfer.
The waste will first enter the Waste Treatment Plant complex in the Pretreatment Facility. The largest of the facilities in the complex, it will be the equivalent of 1 ½ football fields in length (540 ft.), over 70 yards wide (215 ft.), and twelve stories high (120 ft.). It will encompass more than 13.9 million cubic feet of space and contain 100 miles of piping. The Pretreatment Facility will separate the tank waste into low-activity and high-level waste streams for the Low-Activity Waste and High-Level Waste vitrification facilities. The Pretreatment Facility concentrates the waste by first removing any excess water. After that, the solids are filtered out using ultra-filtration technology, and an ion exchange process removes the remaining soluble, highly radioactive material.
The low-activity waste is primarily in liquid form that has a relatively small amount of radioactivity. Referred to as LAW (low-activity waste), these wastes will be sent to the Low- Activity Waste Vitrification Facility. The high-level waste (HLW) is primarily in the solids which have formed in the waste. High-level waste contains much more radioactivity than the low-activity waste does, and will be treated at the High-Level Waste Vitrification Facility. As with the Pretreatment Facility, both buildings required to process the LAW and the HLW are massive. Each will be longer than a football field (300 ft.) and rising at least six stories (90 ft.) tall.
They told me that the vitrified waste will eventually be stored in an underground complex, when that becomes available.
The “Vit Plant” is over 50% complete; construction slowed at one point, when they had to stop and check for some seismic issues, but it’s back on schedule now. They said that they speak to Secretary Chu quite often, when he checks to see how things are going.
The Savannah River Site has a waste vitrification plant, but the chemistry of their waste is far less complex than the Hanford waste, which is why the Hanford waste treatment plant is a much larger, more complicated operation.
You can see photos and videos of the Vit Plant construction at the contractor’s website.
Part of my tour included something near and dear to my heart: a radiochemistry lab. They walked me through the 222-S lab, which is where all the tank waste samples are characterized. This is done in “hot cells”, behind very thick, leaded Plexi-Glass, using robotic arms, which takes quite a bit of training. (My hat is off to any chemist who can work like that — it’s extremely demanding work, and takes serious skill.)
The lab itself dates back to 1952, but Recovery Act funding is helping to upgrade the structure, and the technology is all very modern.
None Of These Parts Are Separate
The biggest take-away lesson from my trip is that nothing is separate: without knowing the tank waste chemistry (222-S lab), and without knowing how to get instruments into the tanks and work with the waste (the CTF), it can’t be retrieved in preparation for treatment at the Vit Plant. Everything is connected, which is why the picture is far more involved than the average reporter or citizen critic seems to realize.
There are plenty of reasons to worry about the progress of tank waste retrieval at Hanford, since it’s quite critical to the overall cleanup effort at the site. There’s no reason that there shouldn’t be continuing independent goal-setting by, say, the GAO or other independent entities. Also, given the history of the site (namely, failure to reveal environmental contamination on several occasions, way back during the Cold War), it’s understandably difficult to trust that they’re doing the right thing now.
So what I’d like to stress is that after my trip to the site, I’m convinced that they’re doing quite a bit of very good work on what I thought was a completely unsolvable problem. They’re making more and more progress, especially thanks to funding from the Recovery Act. This funding will eventually run out, which will be a problem, but hopefully Congress will put value on the progress the Hanford Site has made, and continue to provide the necessary money to push things forward as quickly as possible.
It will be many decades before the tank waste has been properly vitrified and stored permanently. The legacy of the site will continue to be a problem, at least for a while. But, clearly, they’re working on solutions, and making measurable progress.