Shielding Alpha, Beta, and Gamma Radiation 11/08 Integrated Science 3

Transcription

1 Shielding Alpha, Beta, and Gamma Radiation 11/08 Integrated Science 3 Name Per. Introduction The term radioactivity refers to the activity of unstable atoms. Radioactive substances send out very energetic particles or rays in an effort to become more stable. The different types of radiation are alpha, beta and gamma radiation. All of these have the ability to change the chemical makeup of matter including living tissue. When matter is changed, the molecules that makeup the matter is changed. They are broken apart as radiation knocks electrons out of the atoms, leaving them with a positive charge. Charged atoms are called ions. Therefore, these types of radiation are known as ionizing radiation. These types of radiation are further described in the table below. Additional Background Research: 1. Read sections 9.9, 9.10, 9.11 and 9.12 (pages ) in the Global Science textbook (Christensen, 2000). 2. Answer the following questions: a. Describe how alpha and beta particles usually change the atoms they smash into. b. Describe how mutations affect organisms. c. Explain why alpha and beta radiation is more dangerous inside your body than outside of you.

2 3. Complete Activity 9.9 in your Global Science textbook: Calculate your Personal Radiation Dose by completing the table below. DO NOT WRITE IN THE TEXTBOOK! Radiation Source Dose Received (mrem/yr) Your Dose (mrem/yr) Cosmic radiation where you live 26 add for your elevation above sea level: 1,000-2, 2,000-5, 3,000-9, 4, Type of house: if stone, concrete or masonry 7 Ground radiation 32 Water, food, air 40 Natural gas for cooking or heating 2 Weapons fallout 4 X-rays: Chest, teeth (each) G.I. tract (each) Radiopharmaceutical exam (each) Jet plane travel (for each 5 hours of flight) Nuclear power plant adjacent to home TV viewing each hour/day Hours per day x 0.15 Total: The U.S. annual average dose is 360 mrems. How does your total dose compare to that? How might you change the way you live to reduce the quantity of radiation you are exposed to?

3 Procedures to Design Experiment 1. Together with another group you will be conducting an experiment that tests the relative ability of different shield types to prevent the penetration of alpha, beta, and gamma radiation. SHIELDS AVAILABLE: Polyvinyl 5mil; Polyvinyl 10mil; Plastic ; Plastic ; Aluminum ; Aluminum ; Lead ; Lead Considering both the physical properties of alpha, beta and gamma radiation and the data collected from the Counting Lab, complete the Experimental Organizer for the experiment your lab team will conduct. Be thorough, making sure to reference the particular properties you are basing your assumptions and expectations on. Title: Shielding Lab Experimental Organizer Hypothesis: (make predictions about which type of shield will effectively block each type of radiation) Independent Variable: Category: IV Levels # Trials Dependent Variable (include units): Category: Constants:

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5 Procedures to Collect Data: 1. Set your Nuclear Lab Station/Geiger counter to take twenty (20) second counts at 800 volts. 2. Take and record two background readings. Average the two background readings and record the average background reading in the data table below. Background Reading #1 Background Reading #2 Average Background Reading 3. Take 3 readings with each of the following radioisotopes (Sr-40 emitting beta particles and Co-60 emitting gamma rays), matched with each shield your group has been assigned. Data for alpha radiation has been provided for you. To take readings place the appropriate shield into the top slot of the Geiger counter. Then, place one radioisotope, label side down, into the loading tray and slide the tray into the slot directly below the shield (2 nd from the top). Take and record a twenty-second reading. 4. Subtract the average background reading from each count registered on the Geiger counter for each radioisotope before recording data in the appropriate data table. 5. Gather data from your classmates to complete the data tables and calculate mean counts detected. Data Tables: Directions: Record the data collected for each radioisotope in the space below. Remember to subtract the average background reading from each count registered on the Geiger Counter before recording these values. Data Table 1: Radiation Detected for Radioisotope emitting Alpha (α) Radiation Type of Shield Geiger Counter Reading (counts) trials Mean Reading (counts) No Shield (control) Polyvinyl 5 mil Polyvinyl 10 mil Plastic Plastic Aluminum Aluminum Lead Lead

6 Data Table 2: Radiation Detected for Radioisotope emitting Beta (β) Radiation Type of Shield Geiger Counter Reading (counts) trials No Shield (control) Mean Reading (counts) Polyvinyl 5 mil Polyvinyl 10 mil Plastic.030 Plastic.040 Aluminum.025 Aluminum.090 Lead.064 Lead.250 Data Table 3: Radiation Detected for Radioisotope emitting Gamma (γ) Radiation Type of Shield Geiger Counter Reading (counts) trials No Shield (control) Mean Reading (counts) Polyvinyl 5 mil Polyvinyl 10 mil Plastic.030 Plastic.040 Aluminum.025 Aluminum.090 Lead.064 Lead.250

7 Graph: Construct the appropriate graph(s) to present the data collected for each radioisotope. The graph(s) will present the average count for each radioisotope with each shield tested. Discussion: Write a Discussion that summarizes the results of this experiment. *Refer to Guidelines for Experimental Research, page 15 for directions on how to write a discussion. In your analysis of the data, explain how the different materials used to shield the radiation affected the radiation detected by the Geiger counter. Consider: a. the mass and/or charge of each type of radiation. b. why each type of radiation either penetrates or is blocked by each shield tested. c. trends and anomalies you identified in your data. Use actual data values in your explanation. Based on what you ve learned about the biological effects of radiation, include in your discussion the importance of using effective shielding materials when constructing a Nuclear Power Plant.