MainPage:Nuclear:Summer2013:RadiationEffectsPlants
| ⇐ Back to Summer 2013 |
| ⇐ Back to the Main_Page |
Brief Description of Goals
General
This experiment will test the effect of different levels and types of radioactivity in radioisotopes on bean plants' growth and development. Additionally, after the form and dosage level that has the greatest impact on the plants is determined, it will be applied to the plant at different stages of development (i.e. germination, 1 week after germination, 2 weeks after germination, etc). This research is significant because these radioisotopes are utilized in everyday life including the use of Am-241 in smoke detectors and medical diagnostics; Cs-137 in cancer treatment; and Sr-90 in bone cancer treatment and eye treatment.
Cosmic Ray Detector
The purpose of this detector is to establish the best scintillator size and number to determine an uncertainty of the fluctuation of cosmic radiation which contributes to the uncertainty of the overall radiation effecting the plants being tested. It also provides a method to check the dosage of the varying types of radiation from the following radioisotopes.
This website provides in-depth directions on how to construct a cosmic ray detector, and it's instructions provide us with a backbone from which we can design our own detector [1]
We have also done calculations according to the procedure laid out by this procedure:
ΔΩ=(A/4πR^2)*4π
Where ΔΩ equals the subtended solid angle (in steradians) of the cone the two detectors make, A equals the area of the paddle, and R equals the distance from the center of one paddle to a corner of the other.
flux=ΔΩ*Fv*A
Where Fv equals the published value for flux at sea level, which equals 0.66/(cm squared*min*steradians)
Using this method, we calculated the expected flux using the setup in the lab already [1.50/(cm squared*min*steradians)] and using larger sized paddles (14cmx10cmx1xcm) which gave us the expected flux of 9.19/(cm squared*min*steradians). If this process is to be trusted, making the paddles this size would result in an increase in flux of 613%, which makes the construction of new scintillators worthwhile.
Preliminary Test Results
Running the muon counter for a cycle of 24 hours (1440 minutes) a total of 1948 counts were recorded. At different times during Wednesday, July 7th, the count number was recorded in order to monitor for any jumps in the data. Fig. 1, Fig. 2, and Fig. 3 are graphs depicting the data collection.
A second test was run with the computer counting coincidences in addition to the counting module. After 24 hours the two counters were the same, however after the weekend, the counters were off by a factor of about 2,500 counts. The computer was the lower of the counts. After 94 hours, the percent difference of the computer to the count per minute of Nathaniel's test from last semester is 16%. The recent test had 1.26 count per minute on the computer compared to 1.5 count per minute of Nathaniel's test. The module had 1.66 counts per minute and a 11% deviation from Nathaniel's tests.
| Source | Initial Activity | Input Date | Current Activity | Radioactive Particle Distribution |
|---|---|---|---|---|
| Bi-210 | 12 μCi | 11/3/1972 | 0 μCi | β- and a little alpha |
| Cs-137 | 2.3 μCi | 7/1/1988 | 1.3 μCi | Gamma and Beta |
| Cs-137 | 17.8 μCi | 10/15/1965 | 5.92 μCi | Gamma and Beta |
| Cs-137 | 3.86 μCi | 10/15/1965 | 1.28 μCi | Gamma and Beta |
| UO2 - Ore | (1.90 g) | Alpha | ||
| Am-241 | 0.1 μCi | 10/1965 | 0.09 μCi | Primarily emits alpha, but also gamma |
| Co-60 | unknown | Gamma and Beta | ||
| Ru-106 | 5.5 μCi | 2/2/1977 | 1.05E-10 μCi | Beta |
| Sr-90 | 0.1 μCi | 6/2003 | 0.1 μCi | Beta and infrequently gamma |
| Sr-90 | 0.1 μCi | 6/2003 | 0.1 μCi | Beta and infrequently gamma |
Random Coincidences
Sometimes, electrons pass through the two scintillators of the detector and are incorrectly counted as muons, resulting in random coincidences. In order to decrease the amount of random coincides, we will test the cosmic ray detector with 3 and even 4 panels and compare the change in count and analyze each individual coincidence (i.e. when there is a coincidence between panels 1 and 2, 2 and 3, etc.).
Experimental Setup
To begin our experiments, we will test the effect of different low dosages and types of radiation (beta and gamma) on bean plants. After completing this portion of the experiment, we will select the dose that stimulated plant growth the most, and use it to test the effect of radiation on plants at different stages of development. To ensure that the plants germinate naturally, and without any radiation, we will germinate them in moist paper towels placed in plastic bags. This should reduce any unexpected deaths prior to germination and quicken the germination process. The seeds that germinate will be transferred to the soil in one of five cardboard boxes (33 by 33 cm). There will be two levels of independent variable in each box, and four repeated trials (two boxes per form of radiation). Therefor, for each type of radiation, there will be four levels of independent variables (total dose). To calculate the total dose, we are utilizing an online calculator, which calculates the expected dose and then we subtracted the attenuation of the soil from that number. Our dose levels (as displayed below) are relatively low, so it is not certain that they will have major or even any effect on the plants at all.
| Distance from Source (cm) | Cesium-137 (mrem/hr) | Cesium-137 through the soil (mrem/hr) | Total Gamma Dose (mrem) | Strontium-90 (mrem/hr) | Total Beta Dose (mrem) |
|---|---|---|---|---|---|
| 5.00 | 0.670 | 0.187 | 2.01 | 2.18 | 13.0 |
| 5.59 | 0.536 | 0.130 | 1.60 | 1.78 | 5.34 |
| 8.00 | 0.262 | 0.023 | 0.861 | 0.802 | 2.41 |
| 8.94 | 0.210 | 0.016 | 0.678 | 0.634 | 1.90 |
After this experiment, we will test the dosage with the most drastic results bean plants at different stages of development. The following stages will be tested: the seeds before they are placed in paper towels, germination, sapling (one week), and nearing adult (two to three weeks), and adult (over 3 weeks). We will expose the different plants for one week and compare them to a control with no radiation exposure. However, if dosages in the previous experiment have no effect on the plant growth, the layout of the next experiment will be modified.
On Tuesday, July 9th, 120 bean seeds were wrapped in wet paper towels, placed in two plastic bags, and tapped to a window. This method, instead on placing the seeds in soil, causes them to germinate quicker: these beans seeds were supposed to germinate in six to eight day, yet most of the seeds germinated by today (two days). The 105 Stringless Blue Lake bean plants will be used to test the different forms and dosages of radiation, while the 80 Top Notch Golden Wax Bush seeds will be used to test radiation's effect at different stages of development.
On Monday, July 15th, the seeds were transplanted into soil filled pots. The larger pot receive 500 mL of water each day, while the smaller pots receive 50 mL of water each day. The larger pots are to test the dosages displayed in the pots above, while much larger dosages will be tested with the smaller pots to determine if much larger dosages have a much greater effect on plant growth. The plants will be left without radiation for several days in order to ensure that none were injured during the transplant.
On Tuesday, July 16th, the 20 Top Notch Golden Wax Bush seeds were transplanted and 10 more seeds were placed in the wet paper towels to germinate.
Radiation and Aerogel
As a result of exposure to radiation, signs of yellowing have been found in aerogel tiles. Therefore, we will also explore the effect of beta and alpha radiation on aerogel.
After being exposed to Strontium-90 for approximately twenty four hours, the aerogel's color did not change. At 90 hours, there is still no discernible discoloration.