Monthly Archives: January 2015


Radioactive Materials Security – What is IC Quantity?

Hi, Dr. Zoomie – I am putting together a radioactive materials license and they’re asking me what sort of security I have and whether or not I have an “IC quantity” of radionuclides. To be honest with you, I’m not sure what an “IC quantity” is, and I’m also not sure how much security I need. Help!

OK – so let’s try to get this sorted out for you, and it shouldn’t be too bad (hopefully)!

First let’s tackle the easy one. “IC” stands for Increased Controls – a concept that came out within the last decade or so (the new security regulations are only a year or so old). That’s the amount of radioactivity that calls for higher levels of security. If you have less than the IC quantity then you don’t have to worry; more than the IC quantity and security becomes a bigger issue. IC quantities are listed in 10 CFR 37 – for Cs-137 for example the IC quantity is 27 curies; as long as you have less than 27 Ci of Cs-137 on your license then you don’t have to worry about the added IC precautions.

Let’s say you have three nuclides (A, B, and C) and the IC limit is 10 Ci for nuclide A, 20 Ci for nuclide B, and 30 Ci for nuclide C. What you have on hand is 6 Ci of nuclide A, 10 Ci for nuclide B, and 6 Ci of nuclide C. You don’t have an IC quantity of any single nuclide – are you off the hook? Sadly no, and it’s because of the sum of fractions rule. 6 Ci of nuclide A is 60% of the IC limit for that nuclide, 10 Ci of nuclide B is 50% of the limit for it, and 6 Ci of nuclide C is 20% of that limit. If you add these up (0.6+0.5+0.2) you come out with 1.3 – if the sum of the fractions is less than 1.0 then you’re OK; since you come in above that level then IC applies to you (sorry).

OK – so that’s what IC means and when you have to use it; now let’s get into the harder question about how to secure your materials.

The bottom line is that, no matter how much (or how little) radionuclide you have on hand, you need to make sure that nobody can steal it and that nobody can accidentally be exposed to enough radiation to hurt them. The less risk a source poses the less security you need to have. But no matter how minor a source, you are required to take steps to make sure that nobody can just come in off the street and take your radioactive materials without being stopped.

Fiber Optic Active Seal Installation

Fiber Optic Active Seal

So – say all you have is a soil density (“nuclear”) gauge, a lead paint analyzer, or a tank level gauge. The portable devices (lead paint analyzer and soil density gauge) are going to have to be kept locked up at all times. In your office they will have to be kept in a locked room, preferably in a locked cabinet or safe inside that room for added security. Better yet is to limit access to the room to only those people who are permitted to use the source. But the bottom line is that you have to do what you can to keep it from being stolen. In the field, by the way, this means keeping a device locked into the trunk of a car or in a toolbox that locks and that’s fastened to your van or pickup truck.

If you have a higher-activity source or a combination of sources that call under the IC regimen then you’ve got even more work to do. In addition to seeing to the physical security of the source you’re going to have to work with your on-site security or with a security contractor because you’re going to have to submit fingerprints of all the workers who will have access to the source, conduct a background check, and make sure that they are considered to be trustworthy and reliable. If they don’t pass the background check, if they refuse to be fingerprinted, or if their fingerprints have shown up somewhere that they shouldn’t then you probably won’t be able to give that person access to your higher-activity sources.

There are a lot of other aspects to the IC program – you should really check out 10 CFR 37 for all the details – but these are what seem to trip people up the most.

A few other things to keep in mind, with any level of radioactive materials. One is that keys are a weak point of many security systems because they can be copied, lost, or taken with a departing worker. It is far better to have keycard access or, at least, a numeric keypad to gain access to a room. If a key is compromised then you have to call a locksmith and issue new keys to everyone with access to a particular room. On the other hand, if a disgruntled employee leaves your company all you have to do is to revoke authorization for his keycard, or change the key code – much easier and less expensive.

The other thing to remember is that it’s hard to defend against an insider who has legitimate access to a radioactive source. This could be a disgruntled employee, someone who’s looking for quick cash, or a criminal who managed to make it past your background check. But it could also be a loyal employee who is being threatened or who is under substantial pressure. The bottom line is that anyone who has legitimate access to your radioactive sources has the potential to become a weak point in your security program – this is one good reason to conduct periodic evaluations of a person’s reliability to try to make sure they haven’t become a threat since their last check.

Finally, you should consider going beyond the bare minimum required by the regs. Consider asking your local police precinct to visit your facility and take a look at your physical security – they might see things that you would miss. You might want to put in cameras at critical doors to keep track of who’s entering and leaving secured rooms, and you might even consider thermal or motion detectors in your most sensitive spaces. Don’t use flimsy doors (and especially not doors with windows in them) to safeguard high-activity sources, don’t store them near (or in) a loading dock area, and so forth. Let’s face it – in addition to the cost of the sources themselves, a terrorist attack can cause a huge economic impact on your community – you (and your company) don’t want that to come from one of your sources. This is another good reason to ask a professional to evaluate your facility and make recommendations – and for you to follow those recommendations.

Good luck!

Is It Safe To Wear Jewelry With Irradiated Gems?

Dear Dr. Zoomie – I heard that jewelers sometimes irradiate gemstones. Why do they do this (and how is it done)? Is it safe for me to wear jewelry with irradiated gems? I’ve got enough to worry about already!

Well, it is true that a lot of gemstones are irradiated, but they’re completely safe to wear so you can relax a little bit! And now that you’re (hopefully) calmed down a little bit, here’s what happens.

It’s no secret that gems come in a lot of colors and there’s been a tremendous amount of scientific study into why, say, rubies are red and sapphires are blue (both have similar chemical formulae) while diamonds can be pink, blue, colorless, or any of a number of other colors. The general answer is that gemstone color comes from the interaction of the stones with light – some colors are absorbed, some are refracted within the gem, and some are reflected. There’s a ton of sciences, including some fairly heavy-duty physics – that goes into understanding why this occurs and, to be honest, much of it is over my head. But part of the short and (relatively) simple explanation is that different elements absorb (or fail to absorb) different colors of light. The presence of trace amounts of manganese (for example) can give rise to a purple color, iron can turn an otherwise colorless crystal gray or black, copper tints it green or blue, uranium gives us yellow and orange, and so forth. So a crystal’s chemistry can help determine its color.

Irradiated Gemstones - Colorless and other diamonds (left) can be artificially irradiated causing a variety of colors. Some of the irradiated colors are then heated as a second step, resulting in additional colors (group right).

Colorless gemstones can be artificially irradiated causing a variety of colors. Photo by GIA.

But there’s more than this because light has to pass through a crystal and the structure of that crystal also helps to determine which wavelengths (or colors) of light pass through the crystal, are absorbed, or are reflected. Not only that, but the distribution of electrical charge within a crystal also plays a role. This is where the radiation comes in – ionizing radiation can alter the distribution of electrical charge, and slamming neutrons into a crystal can dislodge atoms from their precise alignment, disrupting the crystal structure. Both of these phenomena will change a gemstone’s color – the most common example is topaz; irradiation can turn a rather boring brown or tan topaz into a lovely blue; light blue if it sits in a beam of high-energy electrons and a deeper blue after being bombarded with neutrons in a nuclear reactor. And other gems are irradiated as well – diamonds can be made yellow (for example), but topaz is the most common.

OK – so that’s why and how it works, but you’re concerned about the health risks, and justifiably so, if only because it would be too bad to spend good money on beautiful gemstone that places you at risk every time you put it on. So what we need to find out is whether or not an irradiated gemstone somehow stores the radiation it’s exposed to, or if it becomes radioactive itself.

The first question is easy – irradiated objects do not store radiation and they don’t re-emit it later. Think of a brightly lit room that lacks windows (light is, after all, just a form of radiation). When you turn the lights off the room gets dark – the chairs, tables, walls and so forth don’t glow with the stored light because the light isn’t stored in these objects; when the lights are turned off the irradiation stops and everything gets dark. Just the same with ionizing radiation – when the irradiation stops, that’s it; end of story.

Having said that, some forms of irradiation can make objects become radioactive. I know that this sounds as though I’m contradicting what I just said, but there’s an important distinction between an irradiated object storing and releasing the radiation it was exposed to versus it becoming radioactive itself. What if, for example, you paint a table with glow-in-the-dark paint that’s activated by exposure to light? In this case, exposure to the lights causes the paint to become activated – it causes chemical changes in the paint. Now when you turn out the lights the paint will glow (but the unpainted table will not), fading slowly over time. The paint is NOT releasing the same light that it absorbed – what the light does is to induce a chemical change in the paint that causes it to glow for awhile. By the same token, hitting a non-radioactive material with neutrons (which are present in a nuclear reactor core) causes some of the atoms to become radioactive. But this only happens with objects that are exposed to neutron radiation or to the very highest energies of beta or gamma radiation, and this can only happen in the core of a nuclear reactor or in very high-energy particle accelerators. And, as with the glow-in-the-dark paint, this induced radioactivity fades relatively quickly. By the time a gemstone is sold any radioactivity that was created has long since faded to undetectable levels and they certainly pose no risk to the buyer (or to the wearer).

Another part of this is regulatory – in order for an irradiation facility to sell their gemstones and ship them to the jewelry store they have to be able to show that the stones meet regulatory criteria – they simply aren’t allowed to ship anything that’s still “hot.” This is another protection against your buying jewelry that might put you at risk.

So – the physics of irradiation are such that only gemstones irradiated in a nuclear reactor can become radioactive at all; everything else will simply have the color changed. Physics also controls the rate at which these gems will become non-radioactive, and this typically happens fairly quickly (a few days to a few weeks). And regulations require that these gems be confirmed to be safe before they can be sold to you. For all of these reasons I feel comfortable saying that, even though your beautiful deep blue topaz might have once spent some time inside of a nuclear reactor, it’s safe for you to wear.

But wasn’t there an incident awhile back where people were hurt by radioactive jewelry?

Yes there was – several people were hurt in fact. But this had nothing to do with irradiated gemstones and we think that all of the jewelry in question was rounded up and accounted for. Here’s what happened.

About a century ago people started using radioactivity to treat cancer. One of the therapies that was used involved putting radioactivity (radium, primarily) into gold capsules. These capsules would be inserted into a tumor and the radiation would destroy the tumor. After they were used (or if they weren’t used) these gold capsules were supposed to be disposed of as radioactive waste. Except that some weren’t – somehow a number of these capsules were sold to gold dealer and melted down into gold that was sold to jewelers and made into jewelry. The whole story is too involved to really get into here, but the short version is that several people got skin burns from radioactive rings before the source was tracked down – a number of scientific and medical papers were written on the subject. Luckily, some perceptive physicians figured out what was happening and contacted the regulators – notices went out and the tainted gold was rounded up and disposed of properly. There might still be minor amounts of this gold out there somewhere, but the vast majority seems to have been rounded up and there haven’t been any reported injuries (or contaminated gold) in the last few decades.

Finally – keep in mind that this involved gold that was contaminated by radioactivity; not gold (or gems) that was irradiated. Again, any irradiated gems you buy are a different kettle of fish and they won’t put you at risk.