Radiation Safety & Health Physics Blog

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.