Nuclear Terminology: Getting it Right

On Sunday morning, March 13, 2011, I was reading an AP story entitled “Japan fights nuclear threat” by Eric Talmadge and Yuri Kageyama that really pounded home for me again the need to educate the press and public at large prior to potential disasters, particularly ones involving radiation and nuclear plants.

In talking about the blast at one of the Fukushima reactors, the article says,

“Nine residents of a town near the plant who later evacuated the area tested positive for radiation exposure, though officials said they showed no health problems.”

This choice of words perpetuates a fairly common misunderstanding about the difference between radiation and radioactive contamination. It is not possible in general to test someone for exposure to radiation unless they happened to be wearing some sort of dosimetry when they were exposed. For instance, if you get a medical X-ray, then go down the street to a laboratory it would not be possible for them to run a test and tell if you had the X-ray or not. What these people were likely tested for was radioactive contamination, the presence of particles of radioactive material on their skin or clothing. Unless some of that material was inhaled or ingested, it can be removed through decontamination, stopping the exposure they were receiving from the contamination.

More specific to what is going on in the damaged reactor vessel, the article says,

“..Japanese nuclear agency spokesman Shinji Kinjo acknowledged there were still fears of a meltdown – the collapse of a power plant’s systems, rendering it unable to regulate temperatures and keep the reactor fuel cool.”

In my training as a nuclear engineer, “meltdown” describes only the fuel in the reactor getting to high enough temperatures to melt from lack of cooling. Three Mile Island’s reactor core melted down part of the way, though it didn’t melt through the reactor vessel. The term does not describe the collapse or failure of a power plant’s systems necessarily, though a reactor fuel core is not going to get hot enough to melt down unless a high enough water level cannot be maintained to cool the fuel in the reactor. As long as the reactor vessel is not breached, the primary coolant system would remain intact and a meltdown would not directly impact any other systems than possibly the containment system designed to contain any radioactive material releases from a reactor failure.

Both of these points may seem to be very technical and not important to have just right. My concern is that if people do not see the proper terminology, then they come to believe the terminology that they do see is used correctly. To me, this can create problems in understanding properly presented information provided later, information being put out honestly to support people making good decisions to protect themselves or to inform them why protective actions are not needed.

See IEM’s website for more information on our capabilities and experience in Nuclear Safety, Nuclear Security, and Radiological Emergency Preparedness.


Author: Gary Scronce, Director of Preparedness Programs