Disposal sites run by American Ecology

Here’s another company specializing in radioactive waste: American Ecology. They have four disposal facilities – Beatty, NV; Grand View, ID; Robstown, TX; and Richland, WA. The NV location is right near Yucca Mountain but doesn’t appear to actually do much with radioactive waste, unless that includes PCB “mixed waste”. The Richland, WA site is listed by the NRC as one of the country’s three low-level waste disposal facilities, and the Idaho and Texas locations only accept naturally occurring radioactive material (NORM) and “NRC-exempt waste”. I’m curious to know how many facilities there are accepting NORM, their geology, and methods. According to a webpage associated with Argonne national lab, “The majority of U.S. NORM waste is going to the commercial injection facility charging $150/bbl [/barrel].”

Criticality Unlikely at Yucca Mountain

I recently found myself in a discussion about the likelihood of a criticality (BOOM!) in the proposed repository at Yucca Mountain.

The argument for its being a concern went roughly as follows: Each giant steel canister of spent fuel would contain a large amount of U-235 and Pu-239. The reactor in Oklo contained less fissile (BOOM!able) material than that. Therefore, criticality is a real concern. The presence of water or hydrogen (e.g., associated with any steel corrosion products), or collapse of the shelves holding up the spent fuel would increase that possibility.

I’m not convinced a nuclear reaction is so easy to start. For one thing, we’re talking about spent nuclear fuel (SNF). That means it’s already undergone about as many fission reactions as our nuclear engineers could get out of it in the power plant. If it were so easy to cause the stuff to fission more, wouldn’t we still be using it for fuel? The fissile isotopes may be in there, but in order to for them to undergo fission again the fuel would need to be reprocessed, so that the fissile isotopes are separated from the non-fissile material. Even if some of the SNF is suitable for going critical a second time, there are neutron absorbers (I think mostly boron, but I’m not sure) in the package that should prevent this.

The license application for the proposed Yucca Mountain repository specifically addresses this issue in a 2042-page mega-document called “Features, Events, and Processes for the Total System Performance Assessment: Analyses”. According to this analysis, “for a configuration to have potential for criticality, all of the following conditions must occur: (1) sufficient mechanical or corrosive damage to the waste package outer corrosion barrier to cause a breach, (2) presence of a moderator (i.e., water), (3) separation of fissionable material from the neutron absorber material or an absorber material selection error during the canister fabrication process, and (4) the accumulation (external) or presence of a critical mass of fissionable material in a critical geometric configuration.” After analyzing the likelihood of each of these four factors, the report concludes that “the probability of criticality for the in-package location is much less than 1 chance in 10,000 of occurrence within 10,000 years after disposal.” There are a couple of revisions in later documents, but the ultimate conclusion is that a criticality event is so unlikely that there's no point in worrying about it.

R.W.M.A. and NORM in Louisiana

Today I had the pleasure of meeting with the staff of Radioactive Waste Management Associates in their office tucked in among the art galleries of Chelsea. Most of the projects they take on are related to transport issues and exposure analysis, and their relationship with industry is often adversarial. They portrayed themselves as fighting for workers who are treated as expendable by their employers.

One of the projects they mentioned doing work on involved radium in some Louisiana oil pipes maintained by Exxon. I’m guessing their work was related to this case described by Bloomberg (pdf). This piqued my interest because I rarely think about radium, and I had not realized just how much of a problem NORM can be for extraction industries. NORM here stands for Naturally Occurring Radioactive Materials, although context is everything with acronyms.What are the U-bearing minerals that are so common in the subsurface that drilling so often brings up and concentrates U and its decay products radium and radon?

U-238 as Radiation Shield

An old CBS story includes this sentence: “Even in stainless steel casks lined with lead or depleted uranium to absorb the radiation, the nuclear waste will still be so hot and so dangerous it will have to be moved with remote-controlled machinery.”

My first thought was "Wha?? Depleted uranium?!?" I am familiar and comfortable with providing shielding using lead, but not uranium. Depleted uranium, U-238, is radioactive. Granted its half-life of 4.5 billion years is much, much longer than that of U-235 and 234, but it’s still emitting alpha particles and radon gas. How can adding something that is radioactive help to absorb and shield radiation?

The key is thinking about the different types of radiation. U-238 is an alpha emitter. Alpha particles are a major problem if you manage to ingest/inhale/inject them, but otherwise they aren’t a big issue. They can’t get through skin or a plastic bag. Smaller, more energetic forms of radiation – beta particles, gamma rays, X-rays - are a much bigger threat for passers-by. Wikipedia has a cute little comparison chart comparing the shielding ability of different materials, and U-238 comes out looking 5 times better at shielding gamma rays than lead. Their source appears to be a book called Nuclear War Survival Skills. Fishy.

Apparently, the heavier the nucleus is, the better the absorption of gamma and X-rays. Pb is used because it is the heaviest element that’s common enough to be reasonably cheap. I am curious about when designers would choose to use U-238 or BaSO4 instead.

Putting the Los Alamos garbage “elsewhere”

New York Times (NYT) has an article about cleanup operations at Los Alamos, where waste is being “dug up and trucked elsewhere.” Best I can tell, “elsewhere” means dry storage and WIPP. For more detail, they also link to this report to Congress from the U.S. Department of Energy (DoE) Office of Environmental Management (EM). Aside from the report authors’ decision to use the word “disposition” as a verb, it’s a charming document – nice figures, important bits highlighted, useful executive summary. The NYT also cites the report’s upper estimate for the total cleanup cost as $260 billion, less than the $300 billion I had thought.

The article also includes a link to a DoE flyer about jobs created and saved by the Recovery Act. The good news for nuclear wastenistas is that if you live near one of these 18 locations (I’m 2.5 hours away from the nearest one – boooo) there are jobs. The not so good news is that they have 10,800 new or saved jobs and 73,000 job applicants. So about 14.8% of the people who applied for a job with the nuclear waste cleanup crew got/kept one.

Just for fun, let’s compare that number to college acceptance rates. Applying for and getting one of these nuclear waste cleanup jobs is very roughly equivalent to getting into Amherst, the 18th most selective college in the country. If the hiring/acceptance decisions are completely random, you have a better chance of getting into CalTech or Cornell than of getting one of these jobs.

Decontamination Technology

I once contaminated an analytical balance with some powdered UO2. The cleanup was surprisingly simple; the rad safety people just handed me a commercially available all-purpose household cleaner. (I don’t remember the name of the cleaner, but I think the bottle might have been dark orange.)

Cleanup of contaminated sites is a tad bit more complicated. It's so complicated and difficult, the Department of Energy's 2009 budget request (pdf) indicated it could cost the U.S. roughly $300 billion over the next 30 years. $300 billion! And I thought the $10 billion we spent on Yucca Mountain was bad. [Update: I later saw the number cited as only $260 billion. Only.]

So what is the dominant technology for cleanup of sites contaminated with radioactive material, and why does it cost so much?

The EPA has a website all about environmental remediation technology. According to their screening matrix, solidification/stabilization techniques are favored for most radionuclides. The specific approach I’ve heard the most buzz about uses a permeable reactive barrier (PRB). Essentially you bury a whole bunch of Fe(0) in the path that the uranium (or whatever oxidized baddie) is moving in, and then hope you didn't miss.

I am not aware of anyone is using microbes in any large-scale decontamination efforts yet. It’s a pretty neat idea, although I confess to having a vague Jurassic-Parkian paranoia about it.

Disposal Facilities and Repositories

Is there a difference between a "geologic repository" and a "disposal facility" for nuclear waste?

Merriam-Webster defines repository as "a place, room, or container where something is deposited or stored". (Also: a side altar in a Roman Catholic church - who knew?). The free dictionary's top picks are "a place where things may be kept for safekeeping" and "a warehouse". "Repository" does not clearly denote permanence, unlike "disposal".

There are now three low-level waste disposal facilities in the U.S. (Barnwell, SC; Richland, WA; Clive, UT). The facility in Utah, by the way, is run by a company that was in the news recently for wanting to import waste from Italy.

The Waste Isolation Pilot Project (WIPP) is a facility in a bedded salt deposit outside of Carlsbad, New Mexico that has been accepting both low level waste and transuranics (this usually means elements heavier than U) since 1999.

Are all of four of these facilities repositories? There are certainly references around the internet for each facility being described as either or both of these terms. Still, there is a tendency to only use the term “repository” for big projects that can accept highly radioactive waste. I have also heard WIPP described as the only operational repository for nuclear waste in the world. (Perhaps it is the only operational deep repository in the world?)

I am sometimes dismayed by the conflation of the terms “repository” and “disposal site” because it reflects a certain level of confusion and potentially conflicting goals in handling nuclear waste: We want to put our extra U and Pu in a safe place – so safe that everything will be fine if we call the stuff waste and leave it there for thousands of years – but we also on some level want the option of retrieving those energy sources from our nuclear warehouse if we decide we need them 200 years from now. On second thought, maybe the dual term is exactly right.