For our research project, we attempted to measure the counts of radiation in academic buildings around campus using a Geiger Müller (GM) tube attached to a LabQuest 2. We were also interested in seeing if the radiation levels observed correlated with the ages of the buildings tested. This is an important type of testing to do, as over-exposure to radiation, especially particles, which are high energy photons without mass, can lead to negative results. These can include radiation poisoning, as well as cancer and other genetic mutations. To conduct our research, we walked around each of the buildings at a steady pace for 5 minutes, moving the GM tube from side to side. When there was an indication of possible radiation contamination, the tube was focused on that area to determine if there was a higher radiation count.  For example, there are areas in Olmstead that have radiation warnings on the door, and we stopped and waved the Geiger tube there for a considerable amount of time to test for any radiation contamination that may have been leaking through.

Figure 1. The apparatus used for recording radiation. The GM tube is located on the right. It is a gas filled detector, which functions using a low-pressured inert gas to amplify the signal of any radiation entering the tube. Radiation passes through the gas in the device and the molecules in that gas are ionized, leaving positive and negative ions in the chamber. These ions move toward separate charged sides (the anode and cathode), creating a current which is then sent through the wire to the LabQuest 2 Device to be measured and recorded. Each , , or particle entering the tube is measured as one “count” of radiation.

 

Figure 2. Table of Average and Maximum radiation counts as compared with the age of the building. As read from left to right, the columns are labeled as (1) the buildings tested, with “Background” representing the data we collected between buildings to determine an average radiation level, (2) the average count of radiation observed in each building (per 0.1 of a minute over the course of 5 minutes), and (3) the highest amount of radiation observed in each building, and the age of the buildings that we observed. We initially hoped to be able to distinguish , , and radiation from each other, but upon further review, we determined the only types of radiation we were likely to detect were and high energy . This is because these travel further from their source than , and are generally emitted by the same type of material.

Figure 3. The average radiation counts compared with the age of the buildings. A trend line has been plotted to show the direction of correlation. The black line indicates the linear regression line of best fit, and the blue lines represent the upper and lower limits of the possible fit of that line, according to the standard deviation of the data.

Figure 4. The maximum radiation counts compared with the age of the buildings tested. A trend line has been plotted to show the direction of correlation. The black line indicates the linear regression line of best fit, and the blue lines represent the upper and lower limits of the possible fit of that line, according to the standard deviation of the data.

 

We plotted the above data observed in two graphs (Figures 3 & 4).  Figure 3 shows the average radiation levels by the year that the building was built, while figure 4 shows the maximum radiation level observed by the year the building was built.  According to the statistical testing, there is hardly any correlation in the data for either graph. In figure 3, r=0.275 and r²=0.076, and in figure 4, r=0.228, r²=0.052, where the “r” value indicates the closeness of correlation of the data, and the r² value indicates the percent of data that fits within that correlation. Since both are rather close to zero, this indicates very little fit in the data. Even so, the standard deviation of the average radiation values was only 0.41, which makes the range of possible best fit lines less than half a point higher or lower on either side of the already plotted line, and the maximum radiation level, although a bit higher, has a standard deviation of only 0.95, which still would only raise or lower the line of best fit by less than one count of radiation on either side of the already plotted line. Considering the already low levels of radiation, this standard deviation does not influence the significance of the data in terms of dangerousness of radiation.

The literature provided by Vernier, the makers of M tube and the LabQuest 2 device, states that expected background radiation levels should be between between 0-2.5 counts of radiation/0.1 min. Our average background radiation testing was within this range (avg=1.32 counts/0.1 min, max=3 counts/0.1 min). All of the average readings from buildings were also within this range (the highest average being taken in Skinner Hall: 2.44). Since the radiation count values are so low, and the statistical analysis does not indicate a high possibility that radiation levels are out of our tested range, we can conclude that Vassar campus is safe in terms of radiation levels.

What would you do differently if you had to do this project again?

If we had to redo this project, we would have monitored radiation levels in relation to the GPS coordinates of the buildings.  This would have allowed us to find a possible association between locations on campus and radiation levels. While this would have also more than likely ended up manifesting in insignificant results, it is possible that we could have found an interesting relationship between the two.  It is definitely possible that certain areas of campus are more radioactive than other areas of campus.

What would you do next if you had to continue this project for another 6 weeks?

If this class were to continue for another 6 weeks, we would have been able to attempt to differentiate between types of radiation detected by placing a few sheets of aluminum foil in front of the detector. Only radiation should be able to pass through this barrier, and the other types of radiation should not. We would certainly have tested this with materials we knew to be radioactive before we went into the field.  The data we collected with the Geiger tube did not differentiate between types of radiation.  This could be somewhat problematic.  Certain types of radiation (i.e. and low-energy ) are much less harmful to humans than other types of radiation (i.e. high-energy and ).  By knowing what kinds of radiation we are detecting, we could have more information about the potential risks facing the Vassar community.

What science did you learn during this project?

First of all, we learned about the purpose of the Geiger tube and how it works. This is explained earlier in this post.  We also learned about the different types of radiation, and the risks associated with each kind. radiations are short range particles that  are made up of helium-4 (4He) nuclei. They pose little external hazard. radiations are lighter short range particles made up of either electrons or positrons that can pose some risk, but are easily stopped by barriers as thin as a piece of paper. radiations are photons traveling at high speed that can cause major damage to DNA and other chemocellular functions. These are not easily stopped. Finally, we learned about compiling our data into concise and succinct data tables and graphs.

Information from an Interview with Professor Dave Jemiolo

Dave Jemiolo is the current radiation safety officer on Vassar’s campus, as well as a professor of Biology. We spoke with him about his experience dealing with an issue of radiation in Sanders Physics that came up a few years ago.

Jim Kelly, the radiation safety officer at the time, asked Professor Jemiolo to check out a darkroom below the auditorium in Sanders Physics. By using a geiger counter, he discovered that the entire floor of the room was hot with Radium contamination. He left x-ray paper overnight on the hottest parts of the floor and, upon review, saw that radiation had leached into the paper at various points. It seemed that a radioactive substance had been spilled on the floor, probably in the 1940s, and then some of it was unwittingly sealed in with varnish. He called in some specialists from off campus who ripped out the floor of the room. This led to the physics library below, where Jemiolo discovered background levels of radiation 3 times higher than normal in the entire room. Upon inspection, he discovered that the chemistry department had stored chemical compounds on shelves at one end of the room. Because they were alphabetized, elements like Thorium and Uranium were placed closed together. These two elements are natural radiation emitters, but had never been on license at Vassar before that point and were leaching radioactivity into the room.

In another instance, Professor Jemiolo was asked to check for radiation sources in the geology department. He suspected that radiation could be coming from naturally radioactive minerals stored there, in much the same way as those he discovered in Sanders Physics. He was right and prompted the removal of various minerals stored there. In an exciting turn of events, after removing radioactive minerals from a box and then removing the still hot box, he found radiation seeping through a wall. It was coming from a large rock of Uranium (oxide) that was radioactive enough to penetrate a solid wall.

What these two stories point to is the fact that not all radiation exists as we may imagine. There are many elements where radiation naturally occurs. Professor Jemiolo showed examples of this in one of the Biology labs, including potassium (one of its isotopes is a weak beta emitter).

Many things we are around on a daily basis emit radiation. Older clocks used to have their dials coated in a paint containing Radium because of its luminescent properties. Bananas are rich in Potassium. Some welding rods contain Thorium. This points to some interesting directions our research could have taken. It also is indicative of the many ways in which we are exposed to radiation on a daily basis, but at levels our body is usually capable of regulating or that do not pose a threat.