Author Archives: Dr. Zoomie

How Dangerous is 100 Micro Roentgen/hour?

There are actually two issues here – one is about the safety of the dose rate (1 microGy or 100 microR per hour); the other is whether or not that dose rate is accurate.

Let’s tackle the first one first. A dose rate of 100 microR/hr (1 microGy/hr) is not dangerous. If this dose rate is accurate, living in it continuously (8760 hours per year) will give you a radiation dose of about 0.9 R/hr (9 mGy/yr). This is not a trivial dose – it’s about three times as much as what we’re normally exposed to in a year from natural sources (on average). At the same time, it’s less than 20% as much as nuclear workers in the US are permitted to receive in a year and a little less than half of what radiation workers in Europe are permitted to receive in a year. In addition, it’s less than half the radiation dose rate I measured in Ramsar Iran, which has the highest natural radiation levels of any inhabited place in the world. The residents in Ramsar do not appear to be suffering any ill health effects from their exposure there – it seems unlikely that the dose rate you mention will cause any harm to you.

Now – on to the second question!

One thing that you have to determine is whether or not the readings you note are accurate, and a lot of that depends on the exact kind of radiation instrument you’re using. I used a GM instrument in the Navy and I continue to use them today – they’re incredibly useful. But I also recognize their limitations; one of which is that they’re not very accurate at measuring radiation dose rate – especially from low-energy gamma radiation and even more so at low dose rates. One of the first questions I’d have to ask is whether it’s a digital display, or an electro-mechanical one with a needle pointing at the dose rate. If it’s the latter, I’d also be interested in knowing if the meter is on the very lowest scale with the needle pointing at the very lowest tick mark on the meter face – if this is the case then I would take that reading with a considerable grain of salt; in general, I try to use a meter only when the reading is somewhere between about 20–80% of the range of the scale.
Another question to ask is the size of the GM tube – a larger (and more expensive) tube is more accurate than a smaller, cheaper one.

But the main factor is that GM tubes – unless they are a type of tube called “energy-compensated” – are not accurate at measuring radiation from more than one specific energy. So if your GM was calibrated (for example) using Cs-137 – which has a gamma energy of 662 keV (1 keV = 1000 electron volts) then it can only accurately measure radiation dose from gammas of that exact energy. If you’re using that to measure natural background radiation – with a lower average energy – then the reading is going to be off by a factor of up to 10. This is because the meter “expects” that every bit of radiation entering it has the same energy as Cs-137; if the radiation is lower-energy then the reading will be higher than the actual dose rates.

Anyhow – my best guess is that the dose rate displayed by your instrument is likely not accurate for the reasons given here. But even if it is accurate, this level of radiation exposure should not be harmful.

How Do You Receive Radioactive Materials?

Hi, Dr. Zoomie – I’m working on a radioactive materials license application and it says I need to have a procedure for receiving radioactive materials. What are they looking for?

Virtually every radioactive materials license is going to require you to tell the regulators how you plan to receive radioactive materials at your facility – what precautions you plan to take, what checks you’re going to perform, and so forth. You might only receive radioactive materials once a month – maybe only once a year. Or, on the other hand, if you are at a nuclear pharmacy, a large hospital, or a large research university then you might be receiving multiple packages daily. However frequently you receive shipments, though, you’ve got to have a procedure to make sure it’s done correctly.

The easy way to do it is to commit to using the model procedure that your regulator has almost certainly developed. For example, one of my consulting clients (they had what’s called a broadscope radioactive materials license) had a line in their license application that simply stated “For receipt of radioactive materials we commit to using the model procedure found in Appendix I of NUREG 1556 vol. 11 (Consolidated Guidance About Licenses of Broad Scope).” And that’s all you really need. You can certainly draft your own receipt procedure, but if you do so then you have to be able to show that your procedure is at least as good as the model procedure.

There are a couple of things that have to be part of your procedure – whether you write your own or use the model procedure.

  • All radioactive packages should be delivered directly to the RSO if at all possible.
  • If the RSO is not available (vacation, illness, travel, restroom, etc.) then the package should be placed in a secure location until the RSO can retrieve it.
  • Alternately, the RSO may designate qualified radiation workers to receive radioactive packages in his/her absence.
  • Each package needs to be visually inspected for damage or evidence of leaking contents, surveyed for radiation dose rates (and possibly contamination), and the contents checked against the shipping papers. Most of these checks are required to be performed within three working hours of the package delivery.
  • All of these checks and surveys must be documented and you are required to maintain these records.
  • And if any contamination limits or radiation dose rates are excessive, you need to let the carrier and your regulators know as soon as possible.

With regards to the first point (delivery directly to the RSO), this is important. I worked in radiation safety at one university where a radioactive package was somehow lost between being signed for by University Receiving and delivery to Radiation Safety. In another, a man was ordering radioactive materials to be delivered to him personally, then sending them out to colleagues of his overseas. In both cases, the problems was solved by requiring all radioactive materials to be delivered only to Radiation Safety (and in the latter case, the man was arrested).

Finally, one last thing to consider….

If you regularly receive packages of radioactive materials you should consider having a dedicated location for this purpose. For example, perhaps you can take a corner of a workbench to cover with a benchpad (e.g. plastic-backed absorbent paper). In addition, you should have a secure storage location where the packages can be stored until you can perform the receipt inspection and surveys – and where you can store the materials until they’re moved to their permanent storage or use location.

The Do’s and Don’ts of Transporting Radioactive Materials

Dear Dr. Zoomie – can you give me some good “do” and “don’t” suggestions for transporting radioactive materials? I’m sorta new to all this.

Boy – there’s an open-ended question! And so many things to choose from…hard to know where to start. So let’s see what comes to mind.

  • DO take a minute to properly secure your radioactive materials, especially if they’re in the back of a pickup or open bed truck. A company I used to work for sort of forgot to do this and a nuclear soil density gauge bounced out of the back of the truck when it was driving from a job site. Took us two years to find it again.
  • DON’T let bandits hijack your truck, especially when it contains a dangerous amount of radioactivity. This happened in Mexico a few years ago and got international attention…and not the good sort that increases your sales. One way to help with this is to make sure you have GPS tracking on any vehicles carrying dangerous levels of radioactivity.
  • DO make sure your radiation instruments have been calibrated – especially the ones you’re using to determine the Transport Index (TI) and for other surveys (more on this in a later posting).
    • DO make sure you label the packages correctly (White I, Yellow II, Yellow III) according to the radiation level you measure
    • DO make sure you remember to measure radiation dose rates on the package, outside the truck, and in the driver’s area
Labels Used on Radioactive Materials Packages

Labels Used on Radioactive Materials Packages

  • DON’T re-use Type A packages unless they are:
    • Designed to be reusable or
    • You’ve tested them and can document that they meet the criteria to be a Type A package
  • DON’T park a truck or car with radioactive materials in a sketchy place and leave it unattended – even if it is locked. Unlike a past consulting client whose driver left his locked car in San Francisco’s Tenderloin District (high drug use). The car was broken into, the radioactive materials (medicine intended to be used the next day) were stolen and were probably ingested by the thief, hoping to get high.
    • As an aside – when a cop asks you how he can tell if a drug addict has ingested radioactive iodine (which will destroy the thyroid), DON’T tell him to look for someone who looks lethargic since he will probably tell you the same thing he told me; “In this part of town, everyone looks lethargic. Got anything else?”
  • DO make sure that you and anyone else shipping or transporting radioactive materials have received proper training within the last three years.
  • DO make sure that your radioactive materials are blocked and braced so they can’t shift around in the vehicle when it starts, stops, turns corners, hits bumps, and so forth.
  • DO make sure you lock everything up so nobody can walk away with your radioactive source(s) or the equipment they’re inside
  • DO make sure you contract with a reputable company anytime you ship radioactive materials!
  • DON’T do this (please, please, please):
Punctured package containing radioactive material

Punctured package containing radioactive material

  • DO remember to fill out shipping papers and/or manifest – even when it’s your vehicle transporting your sources to a remote job site
    • And while you’re at it…DO remember to fill out the radioactivity in SI units (1 Ci = 37 GBq, 1 µCi = 37 kBq, etc.)
    • And DO remember to store the shipping papers in the door pocket, on the passenger’s seat, or another place in the driver’s compartment where responders can find them easily in case of an accident

How Do You Package Radioactive Materials for Shipment?

Yo, Dr. Z! I need to learn about how to package radioactive materials for shipment and I’ve got to admit I don’t know where to start. Can you help get me started?

Good luck, man – you’ve got your work cut out for you. I went over this a little bit a few posts ago, but there is certainly a lot of detail to fill in. So let’s get started!

The first thing you need to know is where to find the rules – that’s in the transportation regs. Specifically, you need to look at Subpart I of 49 CFR 173 (49 CFR 173.401 – 477). And right away you’re going to notice a lot of terms with definitions that are not really intuitive. But you have to be able to understand them if you’re going to be able to do this correctly.

So here goes….

First, there are two “forms” of radioactive materials:

Special form means that the radioactivity is in a sealed source or something similar. Specifically, it means that the radioactivity is sealed up inside a welded metal capsule of some sort. Unless they develop leaks, special form materials are unlikely to cause contamination. The A1 limit (more on this shortly) applies to special form radioactive materials.

Special Form

An example of a capsule used for Special Form

Normal form (also called “other than special form”) is everything else. These are unsealed radioactive materials – it could be contaminated soil from a remediation project, radiopharmaceuticals intended to be injected into patients to diagnose disease, or radio-labeled chemicals intended for use in research. The A2 limit applies to normal form radioactive materials.

Normal Form

Example of containers used for Normal Form

OK – so now we get to types of packages. The most common types are Type A and Type B – these will cover all of your packaging needs unless you’re shipping something fairly esoteric (fissile materials, for example, or radioactive materials that are pyrophoric). Virtually all radioactive materials travel inside of Type A packages – these can be as simple as a sturdy cardboard box, metal ammo cans that you get at an Army-Navy surplus store, or something similar (more on this in a moment). Type A packages are used to transport A1 or A2 quantities of radioactivity, so let’s take a brief detour to figure out what in the world this means. And I know this is starting to get confusing – but bear with me for a minute and hopefully it will be a little more clear.

Type A packaging

An example of a container used to meet Type A packaging requirements

There’s a table in 49 CFR 173.435 that gives A1 and A2 quantities for a bunch of radionuclides. If the amount of radioactivity you’re trying to ship is less than the A1 activity (for special form radioactive material) or less than the A2 activity (for normal form) then you can ship the radioactive material in a Type A container. If you’ve got more than that then you have to use a Type B container.

OK – so how does this work in practice? Well…say you’re trying to ship a Cs-137 source with an activity of 20 Ci. What sort of package do you need to ship it in?

So – start off by going to the table I just mentioned. If you scroll down to Cs-137, it lists the A1 limit of 54 Ci. Since your source is 20 Ci, and 20 Ci is less than 54 Ci, it means that you can ship your radioactive source in a Type A package – easy peasy! And if your Cs-137 is not in a sealed source? Well, go a couple of columns to the right to see the A2 (normal form) column and you see that the A2 value for Cs-137 is only 16 Ci. So your 20 Ci of normal form Cs-137 has to be shipped in a Type B container, which is another kettle of fish entirely.

This helps you to figure out how your radioactivity has to be packaged, but we still need to figure out exactly what is meant by a Type A or Type B package. For this, you have to go to another part of the regs – 49 CFR 173.410 is where they start (for typical industrial packages) with additional information given in 49 CFR 173.411-412 and 415. In addition, if you’re going to certify a package yourself, 49 CFR 173.465-466 goes into all of the tests that you have to perform (and that the package has to pass – and that have to be documented) to show the package will be acceptable. For example, you have to show that the package can maintain its integrity when it’s sprayed with water, when it’s dropped onto a hard surface, when it’s dropped onto a corner of the package, when it’s stacked 5 high in a warehouse, and so forth.

So a reasonable question is “Where do I get these packages?”

One answer is that you can do it yourself. To do this, take whatever box you want to ship your radioactive materials in, outfit it the way you plan to use it, and test it. So, for example, if you’re going to have a Styrofoam insert, put that inside the box. If you plan to have your source inside a 25-pound lead shield, put the lead shield inside the box and the Styrofoam insert. If you’re going to seal the box up with strapping tape, buy some of the tape and tape up the box. And then you put it through all of the tests and document that it’s passed them all. Alternately, you can buy a Type A package (make sure it comes with a certificate that confirms it’s been tested). There are also reusable Type A containers – a metal box, for example, that can be locked with a padlock and that’s been tested to make sure it meets the Type A package criteria.

Package Types

Package Types

One last thing, and then I’ll try to put all of this together. If your source comes in higher than the A1 or A2 limits then you have to ship them in a Type B container. If what you have is an industrial radiography source then the camera itself is going to be an acceptable Type B container. But for the most part, Type B containers are fairly large contraptions that can weigh several thousand pounds and take up a fair amount of space – they’re usually transported by highly qualified companies that specialize in shipping high levels of radioactivity. And if you’re shipping some of the more esoteric types of radioactive materials (fissile materials, for example) then you’ve got to meet other criteria. But the people who are shipping things like this are also going to have to go through a LOT of training and they’ll know the requirements very well.

Type B Containers

Type B Containers being hauled on a semi truck

OK – so let’s try to summarize all of this.

  1. You’re trying to figure out how to ship, say, a 10-Ci sealed source (remember, a sealed source is considered to be special form) of Co-60
  2. You go to 49 CFR 173.435 and you see that the A1 limit (for special form) for Co-60 is 10 Ci. Whew – your source is less than this, so you can use a Type A package!
  3. You dig through your supplies and find that you have a reusable Type A package at your facility.
  4. You round up the Type A certificate to ensure that you (or someone else) tested the package properly.
  5. You stick your source in the package and ship it off to its destination.
    1. And if it’s a reusable package – don’t forget to insist that it be returned!

How Do You Label Radioactive Materials for Shipping?

Dear Dr. Zoomie: We’re a well-logging company and we ship and transport radioactive materials sometimes and I just found out we’re supposed be labeling our packages. I’m not quite sure how to figure out the right label to use. Can you help me? Thanks!

Yeah – this is a common question and a place where people make a lot of mistakes. First, the chances that your vehicle will be stopped and that you’ll get in trouble for making a mistake – pretty slim odds. On the other hand, you have to follow the rules whether you think you’re going to get caught or not – it’s the right thing to do. Not only that, but if you’re doing things the right way it doesn’t matter if you do get stopped because you’ll be doing things correctly. So here goes!

The first concept you have to learn is the Transport Index (abbreviated TI). The Transport Index is just the radiation dose rate that you measure at a distance of 1 meter from your package, in mR/hr. So if you get a reading of, say, 1.3 mR/hr a meter away from the package then the TI is 1.3; if you put some additional shielding around the same source and reduce the dose rate to 0.5 then the TI (for the exact same source) is reduced to 0.5. So the TI has nothing to do with the amount of radioactivity in the package – it only reflects the radiation dose rate you measure a meter from the package surface.

A few things to remember – alpha radiation can’t even penetrate through a sheet of paper, so if your package contains only alpha radioactivity then your TI will be zero no matter how much radioactivity is present (beta sources are similar – you might get readings from a high-energy beta emitter such as strontium-90, but might have no readings at all from a carbon-14 source). In addition, you have to remember that a neutron-emitting source (such as many well-logging sources) will be emitting radiation that might not be detected by all radiation instruments – you need to use a neutron detector to measure neutron radiation. Oh – and don’t use a Geiger counter to measure radiation dose rates unless it’s an energy-compensated GM; any other sort of GM detector is likely to give erroneous readings.

OK – so once you’ve got the TI figured out then you can get a start on figuring out how to label your package.

There are three labels you have to choose from, White 1, Yellow 2, and Yellow 3.

White 1 Radiation Label

White 1 Radiation Label

White 1 Radiation Label

The lowest level of label is a White 1. If the radiation level at the surface of the package (what you would measure by putting your radiation detector on contact with the package surface) is less than 0.5 mR/hr then it can be labeled with the White 1 label. White 1 packages don’t have a Transport Index – by the time you get to a distance of a meter there won’t be anything that you can measure.

Yellow 2 Radiation Label

Yellow 2 Radiation Label

Yellow 2 Radiation Label


Next is Yellow 2.  You will use a Yellow 2 label for packages with surface radiation dose rates of up to 50 mR/hr and that are less than 1 mR/hr (TI < 1) at a distance of 1 meter.

Yellow 3 Radiation Label

Yellow 3 Radiation Label

Yellow 3 Radiation Label

The highest level of label is the Yellow 3. These are used to label any packages with surface radiation dose rates in excess of 50 mR/hr OR for any packages with a TI greater than 1 (that is, where dose rate is higher than 1 mR/hr at a distance of 1 meter from the package).

One thing to keep in mind is that if your sources are expected to be transported a lot (soil density gauges, industrial radiography sources, and well logging sources are frequently transported from job site to job site), the carrying cases or packaging will very likely to be properly labeled by the manufacturer already. In that case, all you need to do is to check the radiation dose rates to make sure they’re what you expect to see (if the shielding is compromised somehow dose rates might be too high; if the source falls out of the shield then the dose rates will be too low).

Now that you’ve (hopefully) figured out how to label your packages, you need to know whether or not you can carry a particular package inside your vehicle – or someone else’s. Here, what matters is whether or not the vehicle is a common carrier (e.g. Federal Express) or an exclusive use vehicle (this can be your company truck or a contract carrier); it also matters whether or not the vehicle is open (a flat-bed truck or in the bed of a pickup truck that’s not covered).

If you’re shipping a radioactive package with a common carrier then the radiation dose rate has to be less than 200 mR/hr on contact with the exterior of the package and it has to have a TI of less than 10 (remember – this means that the dose rate measured 1 meter from the package can’t exceed 10 mR/hr).

If you’re transporting the radioactive materials in your own vehicle or with a contract carrier then you have a little more latitude. Here, if the vehicle is closed, you can have surface radiation dose rates up to 1 R/hr (1000 mR/hr) and up to 200 mR/hr on contact with the vehicle’s surface. For an open vehicle you’re limited to 200 mR/hr on contact with the package surface as well as at the edge of the vehicle’s bed. In both cases, you can’t exceed a dose rate of 10 mR/hr two meters from the side of the vehicle and no more than 2 mR/hr in the cab.

The last thing to mention is that some vehicles will have to be placarded – specifically, any vehicle carrying a Yellow 3 package as well as trucks carrying a category of radioactive materials called “low specific activity” (or LSA) material – this primarily comes from remediation of contaminated sites.

Radiation Placard Position on Trucks

Radiation Placard Position on Truck and Trailer

Remember – there’s a lot more to radioactive materials transportation than labeling the packages and placarding the trucks properly.  I’ll have some more postings on the topic, and you can also find information in a booklet published online by the Nuclear Regulatory Commission.

If you’re interested in attending a training course Nevada Technical Associates conducts courses on the topic of Transportation of Radioactive Materials and holds courses several times a year.

How Do You Transport Radioactive Materials?

Hi, Dr. Zoomie – got a question for you. We have some small radioactive sources in some soil gauges that we have to drive from job site to job site. I just took over as RSO and my boss told me to make sure we’re doing the transportation right. Can you tell me what I should be looking out for?

Wow – it might not seem like it, but there’s a LOT that goes into this; too much for a single posting. So let me give a sort of overview here and then I’ll get into some of the details later (there have been a lot of transportation questions lately, so it seems like a good topic to cover in some detail). For starters, the regulations you’ll need to follow are scattered through the Code of Federal Regulations – specifically, Title 49, Parts 171-173 (of 49 CFR 171-173).

So – first of all – if you are transporting or shipping radioactive materials (including your soil density gauges) then you or somebody else at your company is required to attend training in radioactive materials transportation every 3 years. If you don’t have any records showing anybody attending this training then this is something you need to take care of as soon as you can. Incidentally, there are a lot of hazmat transportation courses and most of them include a little bit of information on radioactive materials. But if you are driving these sources around every day then I would strongly advise taking a class that focuses on radioactive materials transportation and shipping since those classes tend to be taught by people who really know the details of radioactive shipments (and believe me, there are LOTS of details).

Second, I also need to differentiate between transportation and shipping. If you are driving the radioactive materials around yourself then you’re transporting radioactive materials. If you’re packaging them and handing them off to somebody else then you’re shipping. But either way you need to have the training every three years. On – you only have to worry about this if your radioactive materials are going to be moving by vehicle over public roads. At a university I used to work for we would transfer radioactive materials by walking them over to the appropriate building – so no need for special packaging or anything. And if you’re moving the materials over, say, an industrial campus that the public can’t access then you also don’t need to worry since these are not public roads.

packaging for transporting radioactive materials

Packaging for transporting radioactive materials

Whether you’re transporting or shipping you need to make sure that the materials are properly packaged. There are three main categories of radioactive materials – Type A, B, and C. Type A quantities of radioactive materials are to be packaged in Type A packages; Type B quantities must be transported in Type B packages, and Type C quantities are transported in (wait for it…) Type C packages – it makes an odd sort of sense. Type A packages don’t need to be very elaborate – some Type A quantities are shipped in strong cardboard boxes sealed with tough packing tape. By comparison, Type B packages are virtually indestructible – there are some videos online that show not only the size of these things, but some of the testing done to confirm that they’ll keep truly dangerous amounts of radioactivity safe, even under dire circumstances. Shown here are a stock photo of a Type A container and a photo I took of a Type B container that was used to transport a high-activity radioactive source – although the Type B container isn’t fully assembled (the two pieces shown are bolted together, one atop the other) you can get an idea of the size and ruggedness of these things.

Workers are loading an irradiated source into a Type B container for shipping.

Workers are loading an irradiated source into a Type B container for shipping.

One big thing to remember – with any package – is that it has to be certified as a Type A, B, or C package! And unless it’s certified then you can’t use it. Now, in your case, your gauge and shipping case (if it came with one) have already been certified as a Type A container so you don’t need to worry about this. But anyone reading this who is shipping or transporting, say, radioactive samples, radiopharmaceuticals, and that sort of thing…well, you might be tempted to just re-use the Type A package you received your last shipment in. And you would be wrong to do so since you haven’t certified the package the way that you normally use it, pack it, and seal it.

You also have to make sure the package is properly labeled – the categories here are White I, Yellow II, and Yellow III depending on the radiation dose rates you measure a meter away from the package (the transport index) and on the package surface. There’s some good information about all of this in a number of places online – one the most easily understandable is on a site maintained by the National Institutes of Health.

There’s a lot more than this on the topic of transportation and shipping, but this is a good place to stop for this overview. As I said, I’ve had a number of other questions so stand by for more details on labeling, packaging, transportation index, and so forth. But this should get you started. If you’re interested in attending a training course Nevada Technical Associates conducts courses on the topic of Transportation of Radioactive Materials and holds courses several times a year.

What’s the Deal with Yucca Mountain?

So, Dr. Zoomie:  what’s the deal with Yucca Mountain?

North Portal of Yucca Mountain

North Portal of Yucca Mountain

In the mid-1990s I was on a technical advisory committee to the organization that was working to find a location for a low-level radioactive waste disposal facility that was to service several states in the Midwest. Even with stringent siting criteria there were a number of locations that would have been acceptable; what stopped the process was that the Midwest Compact decided to pull the plug – changes on the national level made it more attractive to continue using existing sites than to start up a new one. At present, there are a number of sites for the disposal of low-level radioactive waste, but the nation is still struggling to answer a question that many nations have already satisfactorily addressed – where to put the nation’s high-level radioactive waste. This process has recently come up in the news again. This is an important topic – one that warrants more than a single posting – so I’d like to discuss various aspects of the science behind high-level radioactive waste disposal in general, and of Yucca Mountain in particular, over the space of a couple of postings. But first I’d like to start with an overview of where high-level radioactive waste (HLW) comes from and a little bit of history on this topic. So history this week, then we’ll get into the science.

By definition HLW is “highly radioactive material produced as a byproduct of the reactions that occur inside nuclear reactors.” It includes both spent reactor fuel (fuel removed from the reactor because it no longer has enough fissionable U-235 to easily sustain a chain reaction) and waste produced during the reprocessing of spent fuel. HLW can be hot – both thermally and radioactively – and it has to be handled with care. Not only that, but some of the nuclides remain hot for decades to millennia so it has to be kept secure for at least as long as the Pyramids have been standing. There are a lot of factors that enter into storing HLW safely – too many to go into here, but I’ll try to cover them in future postings as well.

All nuclear reactors produce HLW during their operation – a typical reactor will be refueled every year or two; during a refueling outage much of the fuel is shuffled around in the core and the remainder is removed. In other nations the spent fuel is reprocessed – plutonium that was produced during reactor operations is removed and residual fissionable U-235 can be removed as well; whatever’s left over is disposed of as HLW. Until recently plans were to dispose of HLW beneath Yucca Mountain, located in the Nevada desert, but those plans have been on hold for several years. Here’s what happened.

In 1982, realizing that the US needed a long-term plan for high-level waste, the Nuclear Waste Policy Act was enacted into law. This law tasked the Department of Energy (DOE) with developing a repository, the Environmental Protection Agency was instructed to develop environmental safety standards and to evaluate a repository’s safety, and the Nuclear Regulatory Agency was told to develop appropriate regulations. DOE started a long process that led them to Yucca Mountain. Without getting into the details, Yucca Mountain, by 1987 the DOE was beginning to investigate its suitability as a deep geologic repository and Congress approved it in 2002. Instead of solving the issue, though, this only seemed to serve as incentive to those opposed to the site – both inside and outside of Nevada. Both scientific studies and legal/political opposition continued until 2011, when Congress pulled the plug on Yucca Mountain. And there’s where the issue seemed to rest until just recently, when the issue came up yet again. At present it seems the issue isn’t settled after all – but who knows what will happen next year.

At the same time, all of our nuclear power plants are continuing to operate and to produce HLW. At first it was stored on-site in wet storage – immersed in water. As the spent fuel pools began to fill up the nuclear power plants got permission to re-rack their fuel (the spacing of the spent fuel rods is carefully controlled to prevent the possibility of a criticality). With pools continuing to fill up – and still no place to permanently take the waste – the NRC authorized dry cask storage – taking the spent fuel out of the swimming pool and putting it into land-based casks. And that’s where matters stand today – over 50 individual reactor sites are storing their HLW on site in a combination of dry casks and re-racked swimming pools.

All this being said, Yucca Mountain is hugely controversial. There’s not space here to go into all of the controversy – it gets into geology, transportation, groundwater and surface water, and more – but if there’s an interest I’ll try to cover some of the controversy in future postings.

Staying Safe in a Radiological or Nuclear Attack

Dear Dr. Zoomie: Last week a big nuclear terrorism exercise made the news, and I can’t help but wonder “What do I do if something like this happens for real? How do I keep myself and my family safe?”

I’ve been working on this, and related topics for some time and can say, first off, that most of our immediate instincts are wrong. If you can do the right thing – and do it quickly – even a nuclear attack can be survived. But in the case of a nuclear attack, it’s what you do in the first few minutes – before the first public service announcement – that will save your life. Or not. Anyhow – I can’t promise that following the steps listed here are guaranteed to save your life in the case of a nuclear attack. But I can tell you that following these steps will maximize your chance of survival. Oh – I’ll also point out that much of this (sheltering, for example) is simply sound advice for any major attack; not just radiological or nuclear, but also for chemical, biological, bombs, and even most cases of active shooters.

  1. Don’t try to evacuate – go into the nearest (and largest) safe building and wait until the fallout pattern can be mapped so that we know where it’s safe to go outside versus where it’s dangerously radioactive. If you’re outside and in the wrong place (the fallout plume) you will die – if you shelter in a building (as far away from the walls and roof as possible) you will survive. As soon as the plume footprint is known, the government will let us know who should continue sheltering, when it’s safe to evacuate, and the route to take that will give the lowest radiation dose. As the Brits say – Go in, Stay in, Tune in.
  2. Don’t pick your kids up from school or day care! If you are in the fallout plume then radiation levels will be dangerously high. If you go outside, you will pick up a fatal dose of radiation. If you get your kids out of school then they will also receive a fatal radiation dose. The safest thing for everybody is for all of you to shelter indoors.
  3. Prepare – not just for this, but for any big bad thing that might happen. What’s the best building for you to shelter in near work? Around your favorite hangouts? Near home? Where will you find water for the 1-3 days you might have to shelter (for example – you can drink the water in the toilet tank, fruit juice and beer will keep you hydrated, bottled water, etc.)? How about a few days’ worth of food (might finally get around to eating those canned yams!)? You can’t starve to death in a few days, and probably won’t die of thirst either – but we also want to have the strength to evacuate when the time comes.
  4. Make up a family communication and reunion plan – do you know how you’ll let your kids, spouse, etc. that you’re OK? Where will you meet up when the sheltering order is lifted? Figure this out now because an emergency is not the time to be winging it. Even if you can’t find each other right away, you can at least know that everyone is OK. And remember – you might not have to talk directly! Having everyone call in to grandparents, good family friends, etc. will also let everyone know that everyone else is OK.
  5. Radiation and pregnancy – it takes a lot more radiation to cause problems with pregnancy than most people think. Also, most physicians don’t know as much about the reproductive effects of radiation as one might think – after Chernobyl there were at least 100,000 women who had unnecessary abortions because their doctors gave them poor medical advice. Before making any decision about terminating a pregnancy – or letting a pregnancy proceed – talk with someone who can help you to figure out how much dose your baby received and whether or not it’s enough dose to cause problems. THEN you can take this information to your OB/GYN to see if the risk from the radiation – combined with other risk factors (age, alcohol and tobacco use, health problems, etc.) – is unacceptable. You can find a knowledgeable professional by contacting the Health Physics Society ( and then clicking on “Public Information” and “Ask the Experts.” Choose the “Pregnancy and Radiation” topic area.

One other thing – a lot of people might want to buy their own radiation detectors so they can find out for themselves if they’re safe. There’s no problem with this – but they need to buy a GOOD detector (not a cheap and inaccurate one) that will give accurate readings up to dangerously high levels. Some types of detectors overload at levels that are still safe – you want to avoid these. In addition, some kinds of radiation detectors are good for measuring radiation dose and others are designed to measure contamination – you can’t just use any radiation detector for all purposes. Two radiation detectors I’ve used and think highly of are the Dosime and the Ludlum Model 25. Both are solid radiation detectors that give accurate dose rate readings anywhere from normal natural radiation all the way to dangerously high levels. Both are affordable, and both are made by companies that make professional-quality radiation instruments.

Finally, learn how to use the detector, learn what normal “background” radiation levels are in your area, and use the meter every now and again to make sure it’s still operating properly and to remind yourself how to use it. Otherwise you might end up with an inoperable meter, the wrong type of meter, or one you don’t know how to use. Using the wrong instrument (or the right instrument, but improperly) can be more dangerous than performing no survey at all because it can lead to a false sense of safety. And – by the way – most “Geiger counters” are NOT the right instrument to use for something like this!

Does Weapons-Grade Uranium Pose a Health Risk When Handled?

Dear Dr. Zoomie – I was watching The Man in the High Castle and there was a bit about weapons-grade uranium posing a health risk to people around it. Is this true?

I’ve been watching this series too and I just watched that episode myself. I have to admit I was happy to see one of the “bad guys” who was concerned about the health of the public. On the other hand, I was disappointed that the writers (and researchers) got this part wrong. The short version is that uranium – even highly enriched uranium – is simply not very radioactive. I can confirm this from personal measurements – I’ve made radiation dose rate measurements on depleted uranium, natural uranium, and enriched uranium and none of them are very radioactive. Here’s why:

There are a couple of ways to approach this question. The easiest one is to do a calculation using something called a gamma constant – the gamma constant tells us the radiation dose rate from a given activity of a radionuclide at a given distance. For U-235 (the isotope of uranium used to make nuclear weapons) the gamma constant is only about 0.176 mR/hr from 1 curie of radioactivity at a distance of one meter). So now we just have to figure out how many curies of U-235 there are in a nuclear weapon.

The Little Boy nuclear weapon used highly enriched uranium – about 64 kg (141 pounds) of it. This is significantly more than what’s used in modern weapons, but it was our first one and the designers still needed to figure out some of the tricks we use today. Since the uranium in The Man in the High Castle was also intended for a country’s first nuclear weapons we’ll assume they were using this same amount of uranium. OK – this gets us a weight, but we need an activity to use the gamma constant. So a little more work is in order.

Every nuclide also has what’s called a “specific activity” – the amount of radioactivity (in curies or in the international unit of Becquerel). This is the amount of radioactivity in 1 gram of that radionuclide. For U-235 the specific activity is 91 microcuries per gram, so 1 kg will have a thousand times as much, or 91 mCi and the 64 kg in Little Boy would contain 5.8 Ci – to make the math easy, let’s call it 6 Ci.

So – if 1 Ci gives a dose rate of 0.176 mR/hr at a distance of 1 meter, 6 Ci will produce a dose rate of 0.176 x 6 = 1.056 R/hr at a distance of 1 meter. The actual dose rate from the Little Boy bomb was probably lower than this because it wasn’t 100% U-235, and the other nuclide present (U-238) has an even lower specific activity. But let’s use a dose rate of 1 R/hr at a distance of 1 meter – again, to make the math a little easier.

Now we’re to the final part – what health effects do we expect to see from this level of radiation exposure?

The lowest radiation exposure that’s been shown to cause short-term health effects is about 25 rem – this will cause your blood cell counts to drop for a few months due to damage to the blood-forming organs. It takes about 100 rem to cause radiation sickness, about 400 rem to give someone a 50% chance of death (without medical treatment), and nearly 1000 rem to be fatal. With a dose rate of 1 R/hr at a distance of 1 meter this part’s easy – it’ll take 25 hours of exposure to cause a change in blood cell counts, 400 hours to give a 50% risk of death, and 1000 hours to cause death. At a speed of 60 mph it takes about 50 hours to cross the US – not even enough time to develop radiation sickness. And that’s for a person sitting for that whole time at a distance of 1 meter from the uranium – a person in the next row (or the next seat) further away would receive only half (or less) that amount of radiation.

So – when we put all of this together it seems fairly safe to say that even a person sitting right next to all that uranium on a cross-country trip wouldn’t even get radiation sickness. Which means that The Man in the High Castle is overstating things a bit – nuclear weapons are bad when they explode, but they don’t give off dangerous levels of radiation.

Can Hospitals Refuse Patients Who’ve Been Contaminated with Radiation?

Hi, Dr. Zoomie – I’ve heard that sometimes hospitals don’t want to admit patients if they’re contaminated with radioactivity. There’s always a chance that one of my workers might need medical attention and they could be contaminated. How can we make sure that our people get the medical attention they need, even if they’re contaminated? I know it’s sort of far-fetched, but you never know.

You know, this isn’t as far-fetched as you might think. I won’t say it happens all the time, but workplace accidents happen all the time and it’s certainly not unreasonable to believe that you could end up with a contaminated injured person. One scenario that comes to mind almost happened to me a few times – a person’s carrying radioactive liquids and trips and falls down. Just falling on a level surface can hurt someone, especially if they hit their head. But a person can also fall down a stairway or brain themselves on a piece of machinery – the possibilities are endless, as we all know. In any event, you have to know that all of your injured people will get prompt medical attention, even if they’re contaminated with radioactivity.

The first thing is to call whatever hospital your people will be sent to as well as whoever will be taking them there – local EMTs, ambulance service, fire department, or whoever it is that makes these runs. All of you need to meet so that you can all talk through what needs to be done so that your people get the medical care they need with the fewest delays possible. This will probably require that you frankly discuss with the others the type and amount of radioactivity your folks might be contaminated with, the risk that it would pose, and how to work with it safely. And what you need to make sure they understand is that a contaminated patient poses little to no risk to medical caregivers – in fact, there’s virtually no plausible circumstance I can think of in which a person at an industrial, medical, or research facility can be contaminated badly enough that it would pose a risk to medical caregivers.

What the ambulance company needs to know is how to keep their drivers, medics, and ambulances from becoming contaminated; or when this contamination might be warranted. When the patient is critically injured and every minute counts, the most important thing is to try to stabilize the patient and get them to the hospital as soon as possible. We can always decontaminate an ambulance, but if a person suffers irreparable harm or if they die…these can’t be un-done. This means that we do whatever decontamination is possible – but only to the extent that it doesn’t delay any medically necessary care or attention.

If time does permit, there are some things that can be done to reduce the spread of contamination to an ambulance. Removing outer clothing will remove up to 75% of the contamination. Wrapping a person in a blanket or sheet reduces contamination even further, as does putting them in a Tyvek or disposable “bunny suit” to contain the contamination on their clothes and body. If there’s even more time, you can work on decontamination – wipe them down with a damp sponge or washcloth – but only if time permits. Something else you can do to limit the spread of contamination to an ambulance is to cover as much of the ambulance’s interior as possible. Also, remember that any nuclear medicine patient contains more radioactivity than virtually any contaminated worker, and many of them will also have a fair amount of skin contamination as well.

OK – this gets your person into the ambulance and on their way to the hospital, but you still have to persuade the hospital to let your contaminated workers into the emergency room.

As I mentioned earlier, if the patient is critically injured – if every minute counts – there is neither the time nor the need to decontaminate them prior to treating them. In this case, standard hospital precautions will suffice to keep the medical caregivers safe. So as long as they’re wearing gloves, a mask, and maybe a surgical gown – taking precautions to keep the contamination off of their skin – they should be OK. Having said that, even if they DO get some contamination on their skin it’s not the end of the world – I used to do water chemistry on nuclear reactors and I had skin contamination a number of times; every time it cleaned up with soap and water fairly quickly. I think of radioactive contamination as being like changing a diaper – I don’t want to get anything on my hands but, if I do, I just wash my hands and go on with my day. So – if their condition is critical – the patient can be taken directly to a trauma bay and worked on without posing a risk to the medical staff.

Having said that, it can take days, weeks, even months to decontaminate an emergency room and you don’t want to do that unless it’s necessary. If the hospital has a chance to prepare, there are some things that can be done to reduce contamination of their facilities. Most effective is to put down floor coverings – plastic (preferably textured to prevent slipping) or plastic-backed paper. They can also cover the examination table with plastic, and can even put a plastic covering over the lights, trays, and anything else that might come in contact with a contaminated patient. Even better is if the floor is covered with a seamless floor covering, but this obviously can’t be done on the spur of the moment.

You can see a lot of this in the photo below, which I took at the Fukushima University Medical Center a few weeks after the reactor accident – this is the same trauma bay where the two workers who had radiation burns were initially treated.

A Trauma Bay at the Fukushima University Medical Center

A Trauma Bay at the Fukushima University Medical Center

I could go into a lot more details, but space doesn’t permit. So for the purposes of this article, let it suffice to say that the risks to medical caregivers are well-known, they are very low, and can be managed. While it’s best to prevent contamination in either the hospital or the ambulance, if the patient is in urgent need of medical attention, the patient must come first. And for any medical responder, taking standard safety precautions will help to keep them from being contaminated.

So…. If you are concerned that one of your people might be contaminated with radioactivity AND might need medical attention you need to work out the details with both your local hospital(s) and whoever will be transporting the patient to the hospital. Make sure that they understand the (lack of) risks a patient might pose them and, between you, come to an agreement as to what everyone needs to do in order to ensure your people get the medical care they need, without undue delay if their condition is critical. And the time to do this is now – before one of your people is hurt.