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Lab Experiment

Name_____________________________-

 

This lab consists of two parts. One is an assay of your annual radiation exposure which is to be compared with the national annual average. The second is an excercise centered on radon gas and the risk it poses to you. Students in Dr. Volland's WAOL class should file reports using the equiz for the experiment.

All rights reserved 2002-2014,© Dr. Walt Volland

Revised July 21, 2014

Your Annual Dose, the U.S. Annual Average and Radon Exposure

Radiation is bombarding us everyday from multiple sources. Radiation comes at us from natural sources and human made sources. Natural radiation comes from are cosmic rays, minerals in the earth's crust and radioactive isotopes of elements incorporated into internal organs in our body. Human sources include medical radiation such as x-rays, consumer radiation such as TSA screening devices, the residue from atmospheric nuclear weapons testing and industrial processes.

Galactic cosmic rays GCR are made up of high energy electrons, protons, and atomic nuclei from our galaxy outside our solar system. For more visit this NASA page click for more .

cosmic ray source

Radioactive isotopes of elements that are part of naturally occuring minerals make the minerals radioactive. The intensity of the radioactivity depends on the concentration of the isotope and the kind of isotope included in the mineral. Typically minerals that contain potassium (K), uranium (U) and thorium (Th) are radioactive.

Radioactive decay produces Ionizing radiation.

Radiation is a loose term and includes such things as visible light, radio waves, ultraviolet light, and high energy particles capable of ionizing atoms and molecules. The last type is typically called ionizing radiation. When "ionizing" radiation passes through matter, it can knock electrons off of atoms and molecules. It can convert stable nuclei to radioactive isotopes and it can produce electrically charged particles. In living tissues, the electrically charged particles produced by radiation can affect normal biological processes.
There are various types of ionizing radiation, each having different characteristics. The common ionizing radiation types are:

  • Alpha particles are helium-4 atoms without their electrons. The alpha particle has a +2 charge. Alpha particles are emitted by atoms of elements such as uranium and radium. Alpha particles can be stopped completely by a sheet of paper or by the thin surface layer of our skin (epidermis). Ingestion or inhalation of alpha-emitting materials can expose internal tissues directly to alpha particles that can cause biological damage.
  • Beta particles are high energy electrons. They are more penetrating than alpha particles and can pass through 1-2 centimetres of water. In general, few millimeters thickness of about five to ten layers of household aluminum foil will stop beta particles.
  • Gamma rays are very high energy photons or light. Gamma rays, depending on their energy, can pass right through the human body, but can be stopped by thick walls of concrete or lead.
  • Neutrons are uncharged particles 0n1and do not directly ionize atoms or molecules.  Their interaction with the atoms of matter can give rise to alpha, beta, gamma, or X-rays which then ionize molecules. Neutrons are penetrating and can be stopped only by thick masses of concrete, water or other matter.

You can estimate your annual radiation dose from all sources using the following link http://epa.gov/radiation/understand/calculate.html or the table below. This table is adapted from A.R. Hinrichs: Energy, pp 335-336. Philadelphia, Saunders College Publishing, 1992.

The EPA adheres to a linear no-threshold (LNT) model for radiation exposure. This model assumes that all radiation exposure is harmful and that there is no threshold below which exposure is safe. The LNT theory might be questioned because humanity has experienced cosmic ray and natural radiation exposure forever. The principle behind evolution supposes that over the eons organic changes have occurred in life forms that lead to heartier, more resilient organisms. It would seem that humans should have evolved enough to safely survive the natural, constant, low level cosmic ray and natural radiation bombardment.  These sites provide data that raise questions about the validity of the LNT theory and the merits of the alternate radiation hormesis theory.

http://www.21stcenturysciencetech.com/articles/nuclear.html#Case%20of

http://www.wpi.edu/news/20078/radonstudy.html

http://www.ncbi.nlm.nih.gov/pubmed/19066487

This 1998 paper deals with the nonlinearity of radiation effects.

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1533290/pdf/envhper00536-0363.pdf

Half-life

The half-life of an isotope is the amount of time it takes for half of the radioactive atoms to decay into a more stable nuclide. Naturally abundant radioactive isotopes exist around us only because their half-lives are longer than the age of the earth. Uranium 238 (U-238) has a half-life of 4.5 billion years so it is naturally abundant. Cobalt-60 has a half-life of 5.27 years and is man made Most radioactive isotopes have short half-lives and must be produced in the laboratory to study or use.

Graphic displays for the decrease of radioactive nuclides are shown here. animation showing decreases in amount of radioactive isotope for 7 half lives

http://www.launc.tased.edu.au/online/sciences/PhysSci/done/nuclear/decay/Decay.htm

The amount of radioactive matter will decrease by 1/2 after every half life. This means if we start with 6000 atoms then after one half life there will be 3000 left, after a second half life there will be 1500 atoms left and after a third half life there will be 750 atoms. During these changes the amount of decay products will increase. Decay products like alpha particles do not accumulate. Alpha particles are energetic enough so they can strip electrons off of other particles when they collide. One theory holds that helium in our environment comes from the conversion of alpha particles to helium atoms.

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1086250/?page=1

Half-life times are unique for each radioactive nuclide.

.

 

 

 

Estimate of your annual dose

 

 

Sources of Radiation You add the contributions from each source to get your estimated exposure.

 

Annual dose in mrem

 

Location: Cosmic radiation at sea level
For your elevation (in feet) add this number of mrem

 

___26___

________

Where You Live

Elevation in feet

 mrem

Elevation

 mrem

Elevation

 mrem

 ---------------

 

1000

2

4000

15

7000

40

 ---------------

 

2000

5

5000

21

8000

53

---------------

 

3000

9

6000

29

9000

70

---------------

 

Ground or sealevel : U.S. average

 ___26___

 

Home construction: For stone, concrete, or masonry building add 7 mrem

 ________

What You Eat, Drink, and Breathe

Food, water air: U.S. average

Weapons test fallout

 ___24___

____4___

 

How You Live

 

X ray and radiopharmaceutical diagnosis:

Number of chest x rays _______ x 10

Number of lower gastrointestinal tract X rays _____ x 500

Number of radiopharmaceutical examinations _____ x 300

(Average dose to total U.S. population = 92 mrem)

 

 

________

________

________

Jet plane travel: For each 2500 miles add 1 mrem

________

TV viewing: Number of hours per day ____ x 0.15

________

How Close You Live to a Nuclear Plant

At site boundary: average number of hours per day _____ x 0.2

________

One mile away: average number of hours per day _____ x 0.02

________

Five miles away: average number of hours per day _____ x 0.002

________

Note: Maximum allowable dose determined by "as low as achievable"(ALARA) criteria established by the U.S. Nuclear Regulatory Commission. Experience shows that your actual dose is substantially less than these limits.

 --------------

 

Your total annual dose in mrem

________

2.

Comparing your estimated dose with the U.S.Annual Average

The average annual dose in the U.S. is about 620 mrem.

How does your annual dose compare with this average?

Is your annual estimated dose  high, average or low compared to the 620 mrem national average?

  

3.

Principle source of exposure

 

What source is the largest contributor to your annual dose?

a. Where I live.    

b. What I eat, drink, and breathe.        

c. How I live, x-rays, TV watching, jet travel.

d. How close I live to a nuclear reactor.

------------------------------------------------------

 
Radon properties and risks

Environmental Protection Agency, EPA and the United States Geological Survey

You are supposed to answer the questions below using information found at these sites.

EPA site that gives data on fatalities and risks to citizens

http://www.epa.gov/radon/healthrisks.html
 

U.S. Geological Survey answers the question: What is Radon?

http://www.webelements.com/webelements/elements/text/Rn/key.html

U.S. Geological Survey gives general radon risk potential for regions of the United States

http://www.lbl.gov/Science-Articles/Research-Review/Highlights/1993/radon-risk.html

http://www.epa.gov/iaq/radon/zonemap.html

OSHA description of Ionizing Radiation like beta, alpha, and gamma radiation.

 

http://www.osha.gov/SLTC/radiationionizing/

Answers to the questions: What is radiation? How is it measured? How is it produced?


http://www.accessexcellence.org/AE/AEC/CC/radioactivity.php

United States Nuclear Regulatory Commission dose, measurement, detection

http://www.nrc.gov/about-nrc/radiation/health-effects/measuring-radiation.html

Radon risks and radiation facts

QUESTIONS

Name _________________use equiz to file report


1. What isotope of radon ( give element symbol and mass number, X-134 ) is the radioactive and dangerous form? Give the symbol for radon
.

2. What radiation does this dangerous form of radon emit? ( beta, alpha, or gamma )   What does this particle do that makes it a problem?

3. What is the half-life for radon in days?

4. Approximately how much radon from a radon sample will be left after 3.8 days? 7.6 days?

5. What does the EPA say about the number of deaths per year that are the result of radon exposure?

6. What radiation makes radon a health risk ________, What health risk is associated with radon exposure? ________

7. What is the radon risk for your geographical( county) region? High, moderate , low.

For County information use this link http://www.epa.gov/radon/zonemap.html

 

DUPLICATE SET OF QUESTIONS


1. What isotope of radon ( mass number for isotope) is the radioactive and dangerous form? Give the symbol for radon

2. What radiation does this dangerous form of radon emit? ( beta, alpha, or gamma ) What does this particle do that makes it a problem?

3. What is the half life for radon?

4. Approximately how much of a radon sample will be left after 3.8 days? 7.6 days?

5. What does the EPA say about the number of deaths per year that are the result of radon exposure?

6. What radiation does Radon emit that causes lung ________ ?

7. What is the radon risk for your geographical( county) region? High, moderate , low.

For County information use this link

http://www.epa.gov/iaq/radon/zonemap.html