By Nolan O'Brien
Mark Hart has earned an unusual nickname over the years. It isn’t due to his work ensuring the safety and security of nuclear weapons, nor is it due to his prior hands-on work with plutonium.
Rather, LLNL scientist Hart is known for perusing antique shops, fairs and garage sales with Geiger counter and black light in hand, searching for items to add to his collection of radioactive antiques and artifacts. To dealers at these events, Hart has come to be known as Dr. Radiation.
This extraordinary hobby, and his associated passion for public and professional education, has led Hart and his wife Jane to give more than 140 talks about radiation since 1993, helping audiences from all over the world gain a foundation for understanding radiation and radioactivity in the environment.
“There’s a certain satisfaction with giving the gift of knowledge,” Hart said. “The void created by ignorance can be filled with fear. We seek to replace fear with knowledge and understanding.”
Hart’s fascination with radiation grew from his work at a plutonium foundry in the 1990s. “Instead of sleeping through the radiation safety training, I was really interested,” he said. “I began to realize how much I didn’t yet understand.”
Seeing his interest, a coworker from Hazards Control took Hart to an antique store in Martinez where they had dinnerware with radioactive material in it. Hart recalled a diminutive, gray-haired shopkeeper. When Hart told her that he was looking for radioactive antiques, she pointed him to a few items.
“I asked her how she knew they were radioactive,” Hart said, recalling the conversation. “She told me, ‘I used a Geiger counter on it, and it gave off a lot of ohms.’ I bit my tongue, knowing that ohm is a measure of electrical resistance, not radioactivity. There are times when you should educate and there are times when you should go with the flow. However, that was an early hint that even folks who are aware of radioactivity in their environment don’t really understand it very well.”
Hart’s first talk on the topic of radiation came about when his niece at Westmont College heard that he was working in a plutonium foundry. She asked if he would be willing to give a talk on radiation. He agreed.
“I took a paper bag with seven antiques with me,” Hart said. “The professor had me speak before the class in a lecture hall, and I had the items out on the table up front. Nobody paid any attention to them until I mentioned about halfway through the talk that they are old consumer items that contain radioactive material. I was amazed by the college students’ reaction. After the half hour talk, most of the students stayed around for another hour to check out the antiques with a Geiger counter that I brought and ask more questions. That’s when I realized that there was something to this in terms of public education and having an accompanying exhibit of radioactive items.”
After a few talks to students and church groups, Mark reconnected with Jane. They had dated years prior but ended up going down different paths when they went away to college. Hart told her about his newfound hobby and the talks he had been giving. The two have functioned as a team ever since, both as a couple and also as collectors and partners in public and professional education.
Their collection now consists of more than 740 items, and they have given talks with exhibits of more than 100 radioactive items in communities across the country and in Canada to audiences including West Point cadets, U.S. Senate staffers, members of the U.S. Special Operations Command, NASA staff and delegations from South Korea and Qatar, among others.
One of the unique items in their exhibit is a 16 million-year-old megalodon tooth. Based on its size, around 3 inches long, Hart estimates that the tooth came from a 50-foot ancestor of the modern great white. It was found in the Savannah River delta, downstream from the plutonium production plant at the DOE Savannah River Site. The tooth itself is radioactive, which raised the question in Hart’s mind whether its radioactive properties were naturally occurring or due to contamination from the plant, which used river water to cool its reactors. Hart called in a few favors and had an analysis done on the tooth, which showed that the radiation is due to naturally occurring uranium.
“Many people don’t realize that there are 2.7 parts per million of uranium in the Earth’s crust,” Hart said. “It is found virtually everywhere in nature — in rocks, soil, plants and our bodies. It’s also present in small quantities in seawater, which was the key to turning this shark tooth into a radioactive fossil.”
When uranium in seawater flowed past the megalodon skeleton and came into contact with carbon in the tooth, the uranium precipitated from the seawater to the bone, going from a water soluble +6 ion to an insoluble +4 ion. Over millions of years, uranium had concentrated in the tooth. This is a process similar to how minable uranium deposits are formed.
Another popular item in his collection is a naturally occurring mineral called autunite, which Hart jokingly refers to as “Kryptonite.” His autunite specimen features ribbons of naturally occurring uranium on the surface, which glow green under a blacklight. The fluorescence is not due to uranium’s radioactivity, Hart points out, but a property similar to dayglow paint. As he brings his Geiger counter close to the small rock, it comes to life with a crackling sound from low levels of alpha, beta and gamma radiation.
The fluorescent properties of uranium have been used for nearly 2,000 years to color consumer products, like Vaseline glass. Hart estimates that the Vaseline glass items in his collection contain less than 5 percent uranium by weight. Hart’s favorite Vaseline glass piece is an intricately patterned glass water pitcher made in Illinois around 1870, 25 years before radioactivity was discovered by Henri Becquerel in 1896. This discovery was made after experimenting with naturally occurring fluorescent compounds, like those found in Hart’s autunite sample.
As Hart begins his talk on radiation, he drinks from a Vaseline glass wine goblet. He points out that the uranium is dissolved within the glass, and that while the glass contains radioactive material — emitting alpha, beta and gamma radiation, similar to the autunite — the radiation from the Vaseline glass does not make the food or drink radioactive.
“Some people think that radiation is like a contagion spreading from item to item,” Hart said. “They’re afraid because they don’t understand how radiation works. Can radiation be dangerous? Yes, absolutely. But when radiation is put in perspective, there is no reason to be afraid of low-level radiation from radioactive potassium in a banana or the fact that there are roughly half a million naturally occurring radioactive disintegrations occurring in the human body every minute. When we give folks a chance to take a look at some of our items on exhibit and when we have a conversation about the various types of low-level radioactivity in our environment, that fear melts away. There’s something really fulfilling when I see those a-ha moments on people’s faces.”