Hi, Dr. Zoomie. Quick question for you – I’ve got a small radiation safety program and I’m wondering if I need to get dosimetry for my rad workers. How do I know what I need to do?
This question is either really simple or fairly complicated depending on how you approach it. The full answer is going to take a little time, but let me start with the easy version.
According to regulatory requirements, you are required to provide dosimetry to any radiation workers who can reasonably be expected to receive a dose of 10% of allowable limits – that’s 500 mrem (or 5 mSv) in a year. So in theory all you have to do is to evaluate the radiation dose rates in the areas where your workers spend their time and multiply that by the amount of time they spend in that area per year. For example, if the highest radiation dose rate is, say, 0.2 mR/hr and a person works in that area full-time then they can receive an annual dose of 400 mrem (40 hours per week times 50 working weeks per year times 0.2 mR/hr = 2000 hours x 0.2 mR/hr = 400 mR annually). So these workers are not required to be issued radiation dosimetry. Having said that, you might choose to give them dosimeters since they’re close to the level where badging is required – that’s up to you.
Another easy answer is to look at the model procedure for a radiation dosimetry program. This is found in the volume of NUREG 1556 that’s applicable to your type of a program, or in corresponding state regulatory guidance documents. For example, many model dosimetry procedures call for badging anyone who handles millicurie quantities of gamma or high-energy beta emitting radionuclides. Using this criterion, a lab worker (for example) who works with more than 1 mCi of P-32 (a high-energy beta emitter) is required to be issued a dosimeter, even if he or she never works with them long enough to receive an appreciable dose during the year. Other types of radiation safety programs – industrial radiography for example – are also required to badge specific categories of workers (the radiographer and radiographer’s assistant, in this case).
A third (and final, as far as I know) easy answer is just to give a dosimeter to everyone, but this only makes sense if your company is small enough that this won’t cost a fortune, and if your workers are worried about working around radiation.
OK – those are the easy answers, now let’s take a look at what happens when things get a little more complicated. Let’s look at a few specific types of radiation safety programs and see whether or not dosimetry might be called for. And please note – these are suggestions! You HAVE to follow the regs, but you’re not required to do anything in excess of what they require.
- Industrial radiography – the model procedures are almost certainly going to call for badging the radiographer and his or her assistant regardless of the amount of dose they normally receive. You might also consider putting a dosimeter inside the room where the camera is stored to measure radiation dose in this area – this is known as an area monitor.
- Blood bank irradiator (also research irradiators) – these are normally very well-shielded and dose to those working with them is typically fairly negligible. However, you will probably want to give dosimetry to those who operate the irradiator, just in case the shielding becomes cracked or damaged. It’s also a good idea to put at least one area monitor in the irradiator room and in adjacent spaces.
- Industrial gauges (tank level, density monitoring, process control, etc.) – these sources are typically relatively low-activity and well-shielded and workers usually receive very low exposures. However, it’s not a bad idea to badge anyone who works directly with the gauges – especially if they do maintenance on them or work near the beam that emanates from them.
- Soil density and soil moisture content gauges – dose rates here are also very low, but the operator often has the opportunity to expose the source directly to the air, so it usually makes sense to badge those who operate these gauges.
- Nuclear medicine technologists – even if the administered doses are low, these workers are exposed to patients (and sometimes to syringes or capsules) containing radionuclides and they certainly have the potential to receive higher exposures. Nuclear medicine techs (and radiology techs) should be badged unless they have been removed from duties involving any exposure to radiation or radioactivity.
- Small x-ray devices (lead paint analyzers, gauges to measure coating thickness, etc. – these, too, emit relatively low levels of radioactivity and are usually well-shielded. If they are used in a fixed location it makes sense to install area dosimeters at the operator’s station (or wherever workers stand during operation). If the devices are hand-held it is reasonable to badge the operators – this might include giving them extremity dosimeters (ring badges) if they have to hold the objects that are being tested.
- Veterinary clinics, podiatrists, dental offices, and similar places using diagnostic x-ray machines – a lot depends on where the x-ray machines are located. If they are in dedicated x-ray rooms then only the operator needs to have a dosimeter. Oh – if it’s necessary to have a person hold an animal during an x-ray then that person should be badged also if they’re a member of your staff (if the owner holds the animal then dosimetry isn’t needed since they’re only going to hold their pet once or twice a year). If you don’t have a dedicated x-ray room then you should consider having everyone leave the room during x-rays; if staff are going to be in the room routinely during x-rays then they should probably be badged also.
There are a lot of other possibilities – these only scratch the surface, but they should help to give you an idea as to who to consider badging at your facility.
Finally – there’s more to running a dosimetry program than just handing out dosimetry. You have to remember to exchange the badges from time to time (this could be monthly, quarterly, or semi-annually depending on your program), you have to remember to notify your badged personnel of their badge readings at least annually (and preferably after every read), and you have to remember to hang onto your dosimetry reports as long as you have your license. There’s more as well, but if you can attend to these bits then you’ll be off to a good start.
If you’d like to learn more about running a personnel dosimetry course you may want to consider Nevada Technical’s 2-day Personnel Dosimetry course which is given once a year in Las Vegas, NV.