1. Nuclear Science Merit Badge:
Radiation Health & Safety

2. Radiation http://www.med.yale.edu/library/exhibits/curie/hand.html

3. Learning Objectives Types of Radiation
Consequences of exposure to radiation
Uses in the medical field
Radiation containment

4. What is Radiation?
Radiation is the process in which energetic particles or waves travel through a medium or space.
Generally refers to electromagnetic (EM) radiation (charged particles)
Examples: Sunlight, Microwaves, Sound waves (non-EM)

5. Types of EM Radiation Non-Ionizing Ionizing Radio waves Visible light
Microwaves
Ionizing
X-rays
Gamma rays

6. Ionizing Radiation
Ionization is caused when an electron is added to or removed from an atom.
Ionizing radiation is radiation that has sufficient energy to strip electrons from atoms, thus making them ions.
The remaining positively charged atom and the free electron are called “ion pairs.”

7. Ionizing Radiation
An X-ray is a type of ionizing radiation that has a wavelength in the range of 0.01 to 10 nanometers.
A Gamma ray is a type of ionizing radiation that has higher energy than X-rays and has a wavelength less than .01 nanometers.
Concrete or lead are needed to shield against these radiations

8. Electroscope http://www.mikeconrady.com/Documents/electroscope1.bmp

9. History Behind Radiation
X-rays were first discovered by Wilhelm Roentgen in 1895.
He noticed how the rays could pass through some materials and not others.
The rays could be detected using a photographic plate

10. History Behind Radiation
Henri Becquerel discovered that uranium caused a photographic plate to be fogged, just like X-rays.
In 1898, Marie Curie gave this property the name radioactivity.
Radioactivity is the tendency of an element to give off charged particles or rays (i.e., to emit energy).

11. Charged Particles
Two charged particles that are emitted by a radioactive element are
Alpha (α) particles
Beta (β) particles 11

12. Charged Particles An alpha particle has two protons and two neutrons
Same as He2+
Mass: 4 AMU
No electrons! 12

13. Charged Particles A beta particle is an electron or a positron.
Electron charge: -1 e
Positron charge: +1 e

14. Cloud Chamber
A cloud chamber can be used to track the path of electrically charged particles.
When a magnetic field is applied it is able to identify the charge and velocity of the particle.
Cloud Chamber Video

15. Radioisotopes
Isotopes of an atom that are radioactive are called radioisotopes.
These atoms are radioactive because they have too much energy to be stable; they will release energy until they become stable.
This is called radioactive decay. The modern words are “spontaneous nuclear transformation.”

16. Radioactive Decay
In the process of radioactive decay, an atom actually changes from one element to another by changing its number of protons.
The half-life of a radioactive substance is the amount of time required for it to lose one half of its radioactivity and transform into another element.

17. Activity Time!!
Let’s demonstrate half-life using a piece of paper!

18. Radioactive Decay
Radioactivity (or “activity”) is measured in units of:
“curie” Ci
Defined as 3.7 x 1010 decays per second
The traditional unit
“becquerel”. Bq
Defined as 1 decay per second
The SI unit

19. Types of Radioactive Decay
Alpha decay
Nucleus emits an α particle
Loses 2 protons, 2 neutrons
Beta decay
Nucleus emits a β particle
Converts a neutron into a proton and an electron (i.e., the beta particle)

20. Examples Half life = 5.2 years Half life = 4,468,000,000 years
colbolt-60 that is used in cancer therapy, decays to
nickel-60 with loss of a β particle.
Half life = 4,468,000,000 years
radioactive decay of Uranium-238 by alpha emission.

21. Radiation Hazards and Safeguards

22. The International Radiation Symbol
The international radiation symbol (also known as trefoil) first appeared in 1946, at the University of California, Berkeley Radiation Laboratory.
At the time, it was rendered as magenta with a blue background.
The modern version is black against a yellow background

23. Why should ionizing radiation be controlled?
Ionizing radiation can damage living tissue in the human body.
It can create reactive molecules that are poisons in the body.

24. Acute (Deterministic) Radiation Effects
Acute radiation symptoms are caused by high levels of radiation usually over a short period of time
They cannot be predicted with certainty.
Examples: erythema (redness of the skin) and epilation (hair loss)

25. Chronic (Stochastic) Radiation Effects
Chronic radiation symptoms are caused by low-level radiation over a long period of time.
Effects are based on probabilities.
Exposure to low levels of radiation increase a person’s chances to get cancer.

26. Radiation Exposure Levels & Effects
0.62 rem/y – average annual radiation exposure in the U.S.
2 rem/y – international radiation exposure limit
5 rem/y – current US NRC radiation exposure limit
25 rem – measureable blood changes
100 rem – onset of radiation sickness

27. Radiation Exposure Levels & Effects
200 rem – radiation sickness with worse symptoms in less time
400 rem – approximately the lethal dose for 50% of the population in 30 days
1,000 rem – death probable within about weeks, effects on the gastrointestinal tract
5,000 rem – death probable within 1-2 days, effects on the central nervous system

28. Nuclear Technologies

29. Radiation in Medicine Radiology: X-ray imaging.
Nuclear Medicine: Following radioactive tracers in the body.
Radiation Therapy: for the treatment of cancer

30. Radiation Therapy External beam treatments Radionuclide
(brachytherapy)

31. Radiation in Agriculture
Radiation used to kill pests, preserve harvested crops.
Helps detect level of pollution and fertilizer in crops.
Delay sprouting and spoilage

32. Radiation in Industry Process control using radiation gauges
Check for leaks in underground pipes.
Control thickness of manufactured materials
Americium 241-alpha emmiter

33. Radiation in Security X-ray checks of baggage Whole-body scanners
of passengers
Smoke detectors in homes and offices

34. Radiation in Space Mars rovers Satellites International Space Station
Deep-space Probes
Radioisotope
Thermoelectric
Generators (RTG)

35. Radiation in Science Radiocarbon Dating – Carbon-14
Neutron activation - “Finding a needle in a haystack”
Engine testing

36. Differences in dose types

37. Thought experiment
Alpha particles do MUCH more biological damage with a given amount of dosage than gamma rays.
Why?

38. Answer
Gamma rays penetrate straight through virtually any material, including tissue, while alpha particles are easily stopped by thin barriers, including human skin.
Alpha particles will thus deposit their energy into a human much more readily than gamma rays, resulting in more tissue damage.

39. Typical Radiation Detectors
Film packet
Thermoluminescent Dosimeter (TLD)
Ionization chamber
Geiger-Müller (GM) Detector
Scintillation Detector

40. Radiation Kit

41. Thought experiment 2
How does distance effect the measurement of radiation?
How does shielding effect the measurement of radiation?
How does time effect the measurement of radiation?

42. Answer
With increasing distance the radiation dose rate drops since the concentration of particles decreases

43. Answer #2
Shielding reduces the amount of radiation that reaches you, reducing the dose rate

44. Answer #3
A shorter time period doesn’t reduce the dose rate, however since you’re exposed to the source for less time you receive less dose.

45. Background Radiation Rocks and soil Cosmic radiation Solar radiation
Background Radiation is radiation that is a natural part of our environment.
Rocks and soil
Cosmic radiation
Solar radiation
Radon gas
Food and water
From human made sources
X-ray machines
Other medical uses
Tritium dial wristwatches
Gas lantern mantles
Smoke detectors

46. Radiation Regulations
ALARA- As Low As Reasonably Achievable
Time, Distance, and Shielding
National and International limit – 5 rem/y (5000 mrem/y)
Public limit – 100 mrem/y
Radiation Hazard symbol
Displayed at places where radioactive materials are used and stored.

47. ALARA SCENARIOS

48. What we learned Types and effects of Radiation Uses of radiation
Consequences of exposure
Containment techniques