Why have you listed refractory brick as a useful radiation source? I thought refractory brick was used in kilns, furnaces and other applications that involve very high temperatures?
You are correct about the uses of refractory brick in high temperature applications. Refractory brick, or “fire brick” as it is often called, can withstand temperatures as high as 4,000 F and is commonly found in furnaces, fireplaces or exhaust stacks. Therefore, it is certainly useful.
Well then what does that have to do with radiation and radioactivity?
The bricks are usually composed of a combination of clay and minerals, with silica, alumina or kaolin in the mix. The ore that is mined for use as refractory brick (i.e., bauxite) is commonly found in the presence of naturally occurring radioactive elements, such as uranium and thorium. These elements often end up in the finished brick, to a greater or lesser degree, depending upon their concentration in the ore.
So are you saying that furnaces are radioactive?
No . . . only the brick that is used as an insulator for the extremes in temperature contains radioactivity. The remainder of the furnace is typically inert.
What about things that are put into the furnace? Do they become radioactive as a result of the brick?
No. The radioactivity in the brick stays in the brick while the oven or furnace is being used. None of that radioactivity is transferred to whatever is being heated.
Is there a lot of radioactivity in refractory brick?
I guess that depends upon your point of view. There is certainly not enough present to be of any radiological harm to anyone if the bricks are used the way in which they were intended. However, there is frequently enough present to be readily detectable using simple radiation detection instruments.
Let me back up a bit. Are you saying that if I have a furnace now in my place of work, I don’t have to get rid of it because it might contain radioactive materials in the refractory brick?
No. The uranium and thorium in the brick does not pose a health hazard, so it does not need to be replaced for radiological reasons.
But I have read, over the years, about some types of fire insulating materials used in schools that were all removed, at great expense. Isn’t that the same thing?
No. I believe you are referring to the use of asbestos in many construction projects over the years, including the construction of schools. Asbestos was used because it is a good fire retardant and because it provides some excellent heat insulation properties. But because asbestos may become airborne and then enter the lungs of people in its vicinity, resulting in some potential health effects, we don’t see asbestos being used so frequently any more. Nonetheless, many school districts elected to remove asbestos when they found it rather than pay for routine maintenance and control over the lifetime of the school. In the long run, they felt that was the most cost-effective way to go.
And that wouldn’t be the same for refractory brick that might be found in schools?
Actually, the brick is composed, primarily, of silica and alumina. The uranium and thorium in them are in only trace quantities, relatively speaking, and they are securely contained within the brick itself. Unless someone gets it into their head to crush a brick into fine powder, then scatter that powder in the immediate vicinity of people, and find some way of keeping it airborne for a reasonably long period of time, there is very little potential for radiation exposures above those typical of the natural background.
Okay. Earlier you said that the radioactivity in refractory brick was naturally-occurring. What did you mean by that?
The elements uranium and thorium are found in the earth’s crust. They were formed when the Earth was formed. Humans did not manufacture it, and we did not put it there. We pretty much always find uranium and thorium when we dig into the earth. There is no exception when mining for the feed materials used to manufacture refractory brick.
But aren’t nuclear weapons also made from uranium?
They can be. But the natural uranium found in the earth’s crust must be purified and enriched before it has the properties necessary for sustaining a nuclear reaction. Natural uranium is a completely different beast.
So you are telling me that refractory brick contains radioactivity, that the concentrations are too low to be a health hazard, but that you can detect its presence using radiation survey instruments. It doesn’t sound like much of a problem to me.
Radiologically speaking, there really is no problem . . . at least from a health standpoint. However, there are rules and regulations about the disposal of radioactive materials. If the concentration of radioactivity is high enough, and if the applicable regulatory authorities perceive any kind of a health threat, no matter how insignificant, they must go to a specially-licensed low-level waste disposal site that has the necessary containment systems, monitoring systems, and surveillance programs to ensure its perpetually-safe storage.
But why would I have a disposal problem for refractory brick? Why not just send it to my local industrial landfill?
Actually refractory brick is commonly disposed of in industrial and construction landfills along with other masonry and building debris. In some cases, truck loads of brick are brought to the landfill and disposed of with nothing more said. But in other cases, the landfill operator has installed radiation detectors, sometimes called “gate monitors” or “portal monitors”, in order to see if any radioactivity is entering the site. If a monitor is present when the truck loads of refractory brick drive by, an alarm will sound and the trucks will be stopped.
Why in the world would landfills need these monitors?
Unfortunately, there have been occasions when licensable radioactive materials have been shipped to a landfill and disposed of, inadvertently (we hope). When identified after-the-fact, the result was a remedial action project of great expense to the landfill operator, as well as a lot of disruption in his routine operations. Even after the fact, state agencies began watching the landfill even closer to be sure the problem didn’t happen again. So to make life easier on themselves, landfill operators began installing radiation detectors on entrance gates so that they will know about the presence of radioactivity before it enters one of their disposal cells.
How often do the landfill operators hear alarms with their monitors?
Quite frequently, in fact. Some of the monitors in use are so sensitive that they are able to detect the presence of very, very low levels of radioactivity.
Like refractory brick?
Right you are!
So what happens when an alarm goes off?
The landfill operator generally secures the truckload of material, notifies the company that shipped the waste about the problem, and notifies their state authorities. They may perform some more detailed surveys in order to try to find out why the alarm went off, but most of the time they just leave it to the shipper to sort things out by simply turning the truck around and sending it back home. As you might imagine, this can be an expensive (and irritating delay) for the shipper who only wanted to get rid of some useless junk.
Is there always radioactivity present when a gate monitor alarms?
Not always. Like I said before, some of these devices are so sensitive that they will alarm even when nothing more than a statistical fluctuation in the ambient radiation background occurs. However, landfill operators are expert at operating landfills . . . not at interpreting the output from a radiation detection instrument. That is why they typically send the offending shipment back to where it came from rather than trying to deal with it themselves.
I think I see where we are headed. If I have an oven or furnace with some refractory brick in it, I really don’t have any kind of a radiological problem until I try to dump the brick in a landfill. Right?
I’m afraid so. Every single day, more and more shipments of what appears to be plain ‘ole brick from a disassembled oven, heater, furnace or exhaust stack are rejected for disposal at a conventional landfill simply because they caused a gate monitor to alarm.
Gee, that is a problem. That could really slow down a demolition project. And if we have to dispose of the bricks as radioactive waste, wouldn’t that be really expensive?
If the bricks were, indeed, classified as radioactive waste, disposal in a low-level waste landfill would definitely be more expensive than disposal in a local industrial or construction landfill. That is why it is important to determine whether they meet the classification or not.
Are you saying that even though the bricks contain radioactivity, they may still be eligible for disposal in my local landfill?
Most of the time, yes they can. But you will need to take a few precautionary steps first.
First, it is important to know exactly how much radioactivity is in the brick. This is easy enough to do by simply sending a representative sample or two to a conventional radioanalytical laboratory.
If all refractory brick is the same, can’t I just analyze one sample then assume those results are good for any oven or any other device that contains the brick?
Unfortunately, no. The concentration of uranium and thorium in the brick differs depending upon where its feed material was mined, and what types of clay mixtures were used in its production. They can vary from “barely detectable” levels of radioactivity, to levels that are clearly elevated above the natural background.
Okay, so once I have some analytical results from the stack of bricks I want to dispose of, what happens next?
The next step is to do what is known as a “pathways analysis”, showing that even though the bricks are radioactive, they present a negligible radiation exposure potential to landfill workers, and even to members of the general public long after the landfill is closed and capped.
Is it hard to do a pathways analysis?
Not for a qualified radiation protection professional. It is actually a fairly straight-forward process that takes very little time. The only things needed to complete the work are the radionuclide concentrations in the refractory brick, how much brick you want to dispose of, and a few details about the landfill’s operations and closure plans.
Okay, if I get one of those pathways analyses done, and if it shows that the doses to all applicable exposure groups is negligible, then what?
First you will need to share you findings with the landfill operator. Remember, they want to dispose of your surplus material, because that is how they make their money. But they do not want to get into a position of having to remediate their landfill under a state or federal order. So if you can convince them that you are on solid technical, regulatory and health/safety ground by disposing of the brick in their landfill, you are one more step along the road to eventual disposal of your brick.
After the landfill operator is on board, what is the next step?
Next you and the operator will need to share your findings with the radiation protection bureau in the state that hosts the landfill. The professionals in this organization will review the pathways analysis results, make sure that reasonably conservative assumptions (i.e., those designed to maximize the resulting dose) were used in all calculations, and whether there are any other issues that need to be addressed. If they find that everything looks “A-OK” from a regulatory standpoint, and that there is no question about negative radiological impacts to any population groups, they will typically issue the landfill operator a letter of exemption, permitting them to accept your old brick even if the gate monitor alarms.
So then I can let the trucks roll?
Yes you can. As they often say, “all of your ducks will be in order”.
How long does it take to do all of this stuff? In other words, if I have a partially disassembled oven that I was hoping to get rid of right away, how long will it take to get it into the landfill?
I’m afraid you will have to allow yourself a minimum of 45 days.
Goodness! Why so long?
It typically takes 30 days to get the analytical results back from the representative bricks you send to a laboratory. You can ask for quicker turn-around times from the lab, but the cost per analysis goes up considerably if you do.
Okay, that’s 30 days. What about the remaining 15?
Once you have your analytical results back, you will need to prepare the pathways analysis, present the information to the landfill operator and assure their buy-in, then submit the package to the regulatory agency for their review and approval. These steps can easily take 15 days. In fact, they can often take between 60 and 120 days, depending upon how busy the regulatory agency is at the time your application arrives, and how experienced they are at reviewing the types of calculations you submit.
Wow. You mean that I have to plan ahead by as much as four months just to get approval to dispose of some old refractory brick?
Shorter approval times are possible, but these are typically the exception, rather than the rule.
And if I just go ahead and dispose of the bricks without going through the approval process?
There is a chance that the landfill you have selected does not have a gate monitor, although those chances get smaller and smaller every day. If so, you may be able to slide a few truckloads in without raising any concerns. But there is always the chance that a state agency will come to the landfill at a later date, perform an inspection that involves a walk-over radiation survey of some number of disposal cells, and . . . guess what? As you can imagine, neither the landfill operator nor the regulator will be pleased as it will probably take them quite a bit of time (and expense) to figure out what is causing the elevated exposure rates. However, they will eventually track the source back to you.
Uh oh. That doesn’t sound too good.
No it doesn’t. And things could get even worse when they do come knocking on your door. You might find all of your disposal privileges suspended entirely, or you might find your demolition project delayed long beyond your allotted schedule, or even worse.
Imagine your management receiving a call from the local newspaper asking why they tried to dispose of radioactive waste at the local landfill. After they mumble a bit about the radioactivity being naturally-occurring, you will quickly see that reporters don’t know naturally-occurring radioactivity from a hole in the ground. So the article comes out in tomorrow’s edition of the local newspaper, with your firm’s name prominently displayed in the headlines.
You’re right. Not a good thing to have happen.
But there’s more. If the landfill operator has to go to great expense to retrieve your brick, you can pretty much count on their attorney calling your attorney to see about cost recovery. And if the landfill suffers any untoward publicity themselves for inadvertently “disposing of radioactivity”, your firm will likely take another legal hit.
Okay. Okay! I see what you mean. I definitely won’t dispose of any used refractory brick without securing the necessary approvals first. But what happens if I go through the pathways analysis and find out that I can’t meet the dose level that the state agency considers to be safe?
In that case, your only options are to try to recycle the brick through alternative users, or to dispose of them at a low-level radioactive waste landfill. In either event, you will need to have the analytical data in hand anyway. In addition, you will need to be sure your shipment to a recycler or radioactive waste facility meets all applicable Department of Transportation requirements before it hits the open road.
I believe I now understand why you have included refractory brick in this tutorial. It certainly is useful material, but it does come with a bit of a problem. But would you mind giving me a brief summary?
Not at all. First off, the radioactivity in refractory brick is of low concentration and, when used the way it is supposed to be used, presents no discernible radiation-related health effects to people in its vicinity. However, the radioactivity is often detectable using conventional radiation survey instruments, and is easily identified by the gate monitors that are present at most landfills. Therefore, if you are looking at a demolition or construction project that includes disposal of refractory brick in the local landfill, you will need to give yourself enough time to go through a series of straight-forward steps to ensure the transfer is smooth and free of any negative publicity or regulatory interferences.
Are there places I can go to get help with these types of disposals and shipments?
Absolutely. Just be sure your source of assistance is qualified to perform the necessary calculational and analytical tasks, and that they have been through the process before. It will save you a lot of time and money in the long run. And if it turns out that the radionuclide content in the refractory brick is just too high to permit disposal in the local landfill, your source can help you identify some alternatives.
Any chance that Plexus-NSD is one of those sources?
As a matter of fact, we are. Just give us a call.
Before we start tearing out our oven, right?