Comparing computer code for radiation worker safety

Faculty is standing infront of a building


How do you quickly calculate a worker's radiation skin dose in the event of exposure? VARSKIN--maintained and updated at Oregon State--is one of the main computer codes used by the Nuclear Regulatory Commission, and undergrad Logan Anspach's peer-reviewed paper examines how it stacks up against other tools.

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Season 6
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ODEGAARD: I’m Jens Odegaard and welcome to season 6 of “Engineering Out Loud.” This season we’re excited to feature student research and projects from fresh-faced undergrads up through the grizzled ranks of the doctoral level.

What these students are doing in school is already impacting our day to day lives through things like software solutions for helping those living with mental illness take control of their health to impacting the generation and storage of renewable energy. Or like today’s story, using computer code to help keep workers exposed to radiation safe.

[MUSIC: "The Ether Bunny" by Eyes Closed Audio used with permission of a Creative Commons Attribution license.]

NARRATOR: From the College of Engineering at Oregon State University this is “Engineering Out Loud.”

ODEGAARD: If you can, think back to the end of your sophomore year. That transitional period where everyone is finishing off the standard core classes that we all takes in common, and starting to split off into the more specific upper level undergraduate tracks. It’s also probably the time that you started getting serious and looking for internships.

It’s in this transitional period that we meet Logan Anspach pursuing his degree in radiation health physics.

ANSPACH: It's at this point where I don't have a ton of experience in the field, I haven't taken a ton of classes, but I really want to try to get an internship. It's going to be pretty difficult to get an internship, so I thought, well, why don't I just email Dr. Hamby and just say: "Is there anything going on at the Rad. Center that I can help with?" And he said, ‘Oh, why don't you just come down to my office, let's talk.’” And then he basically offered me a summer job that has became this project.

[MUSIC: “Pretty and Cruddy Beat” by Podington Bear used with permission of a Creative Commons Attribution-Noncommercial license.]

ODEGAARD: Dr. Hamby is radiation health physics professor David Hamby in the College of Engineering. The Rad. Center is the Oregon State Radiation Center here on campus which houses a variety of radiation- and nuclear-related labs and facilities. The project Logan mentioned? Eh, no big deal, just lead authorship as an undergrad on a peer-reviewed research paper published in one of the premier journals. You know, basically the undergraduate academic equivalent of hitting a game winning grand slam in the College World Series. But first let’s take a step back back. What is radiation health physics? Here’s Kathryn Higley, head of the College of Engineering’s School of Nuclear Science and Engineering. She’s also one of the world’s top health physicists. I caught up with her for an impromptu interview in her office, so excuse the audio quality.

HIGLEY: So health physics is really sort of the art and science of radiation protection and so you use your knowledge of radiation detection of radiation safety limitations to help manage programs, to help oversee maybe technicians that are doing decontamination or doing remediation of facilities and things like that.

ODEGAARD: A common oversight role for health physicists would be checking up on equipment that we’re all familiar with.

ANSPACH: My dad is an MRI tech and an X-Ray tech, he's like, "Oh, yeah, I have state health physicists come in all the time, and they do checks on our X-ray machines."

ODEGAARD: Really, health physics boils down to understanding how radiation interacts with biological systems like us humans, animals, and plant life. From there, you can set radiation dose limits to keep radiation exposure at a safe level.

ANSPACH: Radiation protection in the quick sense is really just making sure that people do not exceed doses that are harmful to them. The idea is trying to find a balance between the beneficial use of radiation, nuclear power, and medical uses as well. So, it's a lot of limiting and monitoring radiation exposure, to ensure that we are in still in this realm of beneficial use of radiation technology.

ODEGAARD: When we’re talking about radiation protection, we’re really talking about protection from ionizing radiation as opposed to non-ionizing radiation. Non-ionizing radiation, radiation like microwaves and radiowaves doesn’t have enough energy to cause damage. Ionizing radiation on the other hand is radiation that has enough energy to cause damage. Think X-rays for example, or on the very low energy end of ionizing radiation, ultraviolet light.

Oregonians like myself get a crash course in radiation damage every winter when they leave the fog and rain and head to the sunshine of Hawaii, forget the SPF 45, and promptly burn themselves in nature’s oven. In addition to feeling like you took a blowtorch to your skin, the over-exposure to UV light is causing tissue damage. This is because, it’s actually causing damage by messing with the electrons in the atoms, which make up the molecules, which make up the cells, which make up you. Now as I said, ultraviolet radiation is on the very low end of ionizing radiation. But it’s ionizing radiation like X-rays or radioactive waste with a lot more energy that damages at a whole new level.

ANSPACH: So the general term is ionizing radiation which means that it ionizes atoms; it'll strip electrons. So, when you have DNA in your body, it bonds with other nucleotides, through the interaction of electrons. So when you are stripping those electrons, it'll break DNA strands, which can reorganize themselves. That's a big issue because DNA tells your cells how to work, what to do. So, if you're getting dosed, way too high, exceedingly, you can potentially lead down the road to the proliferation of cancer or other issues.

ODEGAARD: In other words, ionizing radiation destroys the electron-bond or the glue that holds atoms together by stripping the the electrons from the atoms. From a radiation protection and safety side, the trick is to limit the radiation dose from sources that can be controlled. Some radiation dose can’t be controlled, because we’re all exposed to natural dose of ionizing radiation in our everyday lives. In the U.S., we measure radiation exposure in rem and on average the annual dose per person is 620 millirem or .6 rem, that’s according to the National Council on Radiation Protection and Measurements.

[MUSIC: “Low Jack” by Podington Bear used with permission of a Creative Commons Attribution-NonCommercial license.]

Of that .6 rem, 50% is from natural sources like the radioactive gases radon and thoron, and cosmic radiation from space. The other 50% comes primarily from medical sources, things like CT scans and nuclear medicine procedures, and to a much lower extent industrial or occupational dose. It’s these non-natural sources of ionizing radiation that are regulated and limited by agencies like the Nuclear Regulatory Commission or NRC.

The NRC sets the annual dose limit for radiation workers to 5 rem total. To help keep track of this worker dose, the NRC uses a variety of computer codes to estimate and calculate the dose. One of these codes is called VARSKIN. First developed in 1987, there have been iterations over time as computers have advanced, and around 2007, Oregon State’s Radiation Dosimetry Group headed by David Hamby took over the development and maintenance of the VARSKIN code. Logan’s part of this group working on VARSKIN. VARSKIN is used to calculate dose from exposure to radioactive particles or other contamination on or near the skin. This exposure could happen in a variety of scenarios:

HIGLEY: So anyone that's working say in the field or in the lab where you have a particulate version of radioactive material could potentially get a flake of this material on their skin. It's more common say in the nuclear industry where people are working with water lines, pressurized water lines that come off the primary system, and there is the potential for corrosion products and maybe some rust flakes or such that could be in the water. I mean, think about if you're changing out a hot water heater and some of the crud that can be at the bottom of that, it's a little bit different in a nuclear power facility, but it's the same general kind of concept. You have some solids in there, really small amounts, and that radioactive particle could potentially get on your clothing and on your gloves. Depending on how you doff your work clothes, potentially could move onto your skin.

ODEGAARD: Once the exposure happens, it’s necessary to quickly calculate the dose.

ANSPACH: So, the cool thing about VARSKIN is it's pretty easy to use; it's kind of a quick calculator that you don't need to know a ton of programming to know how to do, which a lot of other tools do use a lot of programing. So, if some company wants to use this, they can easily train their people how to use it.

ODEGAARD: VARSKIN contains a library of hundreds of sources of radiation. And through a series of dropdown menus you can select a variety of information about the source, its size and shape, how large the affected area of skin is, and other relevant information. It then spits out a dose estimate.

ANSPACH: Let's say, for instance, I have a spill of cobalt-60 on the back of my hand. Well, it's approximately in this area, 10 square centimeters; let me, I'll enter this data into VARSKIN - you just pick cobalt-60, you'll put this on a spill of 10 square centimeters, and you'll say well, it was on there for a minute. And you can put the data in, and it'll calculate an approximate dose. That's very quick to send to the NRC, and they can do their calculations as well, and say, "Hey, okay, thank you for letting us know about this."

ODEGAARD: Reporting and verifying these dose estimates helps keep workers safe as well keeping companies in compliance with federal law. To ensure accuracy, VARSKIN’s calculations need to be compared to other dose tools and literature. It’s here that Logan’s peer-reviewed paper comes into the picture. Just as consumer software evolves and is updated, so too is VARSKIN. And as it was updated, it became necessary to compare VARSKIN to other tools and literature to make sure it was calculating dose at a comparably accurate level. Logan had seen some papers comparing VARSKIN to other tools and emailed Professor Hamby.

ANSPACH: Basically, I started with, "Hey, we have these papers that came out, and it's comparing other data, from MCMP, other tools, to VARSKIN, and VARSKIN is falling short in these categories."

ODEGAARD: The categories, as might be expected for work that eventually became a peer-reviewed scientific paper, were pretty technical. But basically it looked like they needed to examine more closely whether VARSKIN was accurately calculating dose when a source was interacting with the electrons in the atoms of the skin.

ANSPACH: And Dr. Hamby really what he wanted me to do is just run all these comparisons, start looking at data. Just run as many comparisons as I can, make these charts, pull out all this data, and say, “Just try to visualize this.” Say, "What's going on here?" And at that point, we sat down and said, “Okay, like, this is where VARSKIN's falling short in these scenarios -- why is that?” And we sat out to figure that out.

ODEGAARD: In this case, figuring out if VARSKIN was calculating dose at a comparably accurate level meant hours and hours with a laptop. Logan pored over paper after paper, importing graphs and charts and tables from other research and computer codes into Excel to build a scenario library so to speak. He then took this data from the comparison papers and tools and ran these scenarios in VARSKIN to see how it was holding up.

ANSPACH: So what we found is that VARSKIN does compare pretty well to a lot of the data that exists currently.

ODEGAARD: Logan worked on this comparison from the summer after his sophomore year through his junior year at which point Professor Hamby felt it was ready for the limelight.

ANSPACH: I mean at that point, he said: “This could become a paper, I think, if you compare. Especially the NRC, they would love to see something like this, because it's their tool.”

ODEGAARD: Logan took lead authorship with Professor Hamby co-authoring the paper. They submitted it to the journal of Radiation Protection Dosimetry from Oxford University in the fall of 2017, and it was published in January 2018. I’ve put the link to the paper on our website at Logan’s now finishing up his senior year at Oregon State and is weighing his future options.

ANSPACH: Talking to Dr. Hamby about it as well, I still want to get my master's done, master’s of science. And I'm hoping to continue with VARSKIN in that regard.

ODEGAARD: Whether further academic pursuits related to VARSKIN happen or not, Logan, before even graduating with his bachelor’s degree, has already made his mark with published research informing the highest levels of regulating agencies in the nuclear and health physics fields. So for now, we’ll let Logan end it with some advice to his fellow students.

ANSPACH: For undergraduate students, I really encourage you to reach out to your professors and say, “Hey, I'm just willing to help.” So, if you are able to reach out to your professors and start early on even something that you might find a little mundane, it could become an internship in the future, it could become a job.

ODEGAARD from interview: It could become a peer-reviewed paper.

ANSPACH: It could become a peer-reviewed paper.

ODEGAARD from interview: That’s awesome, what brought you to Oregon State initially?

ANSPACH: Well, I’m from Portland initially…

[MUSIC: “Pretty and Cruddy Beat” by Podington Bear used with permission of a Creative Commons Attribution-Noncommercial license.]

ODEGAARD: This episode was produced and hosted by me, Jens Odegaard. Audio editing was by the awesome Brian Blythe. He makes music under the name Mortal Thing and just released his first album “On Nature.” You should check it out on Spotify or anywhere else you buy or stream your music. Our intro music is “The Ether Bunny” by Eyes Closed Audio. You can find them on SoundCloud and we used their song with permission of a Creative Commons attribution license. Other music and sound effects in this episode were also used with appropriate licenses, and you can find those links on our website. For more episodes, visit our website Also, please subscribe by searching “Engineering Out Loud” on your favorite podcast app. See ya on the flipside.

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