Now for the Feature
Presentation…
Nuclear
R D TION
Since Antoine Henri Becquerel’s accidental “stumble” onto the
phosphorescent ability of uranium and Marie and Pierre Curie’s
discovery and coining of the term “radio-active,” nuclear radiation has
traveled a long way in its history of construction and destruction. It
played an important role in World War II and the Cold War. Now,
nuclear radiation pervades modern society, making its appearance in
medicine, in nuclear electric plants, and in never-ending research. This
is a journey to uncover its fundamental mechanics…
The Discovery
of
Radioactivity
A. H. Becquerel 1896
•Natural radioactivity was first observed in 1896 by A. H. Becquerel, who discovered that
when salts of uranium are in an unexposed photographic plate carefully protected from light,
the plate becomes exposed.
• the salts exhibit phosphorescence and are able to produce fluorescence. Since these effects
are produced both by salts and by pure uranium, radioactivity must be a property
Marie and Pierre Curie 1898
•Won the Nobel Prize in 1903 for their research on
the phenomena Marie named radioactivity.
•Marie and Pierre Curie extended the work on
radioactivity, demonstrating the radioactive
properties of thorium.
•Their work also led to the discovery of two new
elements--polonium and radium in 1898.
THE
CURIES
Others who contributed...
Frédéric and Irène
Joliot-Curie
discovered the
first example of
artificial
radioactivity in 1934
by bombarding
nonradioactive
elements with alpha
particles.
In 1899 E. Rutherford
discovered and named
alpha and beta radiation,
and in 1900 P. Villard
identified gamma
radiation.
Harriet Brooks
Harriet Brooks' first
real discovery came
from working with
radium, After studying
and observing the
emanation from radium,
Brooks decided that it
had to be a gas.
E. Rutherford
Frédéric and
Irène JoliotCurie
Radioactivity
Radioactivity refers to the phenomenon in which particles are
emitted from the nucleus of an atom due to nuclear instability
The products of radioactivity—alpha,
beta, and gamma—were distinguished
when scientists found that they could be
separated by either a magnetic or
electric field
Radioactive Elements
Not all nuclei are stable; however,
they will decay into a more stable
atom. This radioactive decay is
completely spontaneous.
There are three ways that a nucleus
can decay. It may give out :
•an alpha particle (symbol a)
•a beta particle (symbol b)
•a gamma ray (symbol g)
Radioactive Decay Equations
Mass Number
E
Atomic Number
Element Symbol
Half-Life
The one way to apply half-life is the explain the process of
radioactive decay and its relationship to the concept of
half-life. The primary intent is to demonstrate how the halflife of a radionuclide can be used in practical ways to
"fingerprint" radioactive materials, to "date" organic
materials, to estimate the age of the earth, and to optimize
the medical benefits of radionuclide usage.
Half-Life Calculations
Definition: The length of time for half of a given number of atoms of a
radioactive nuclide to decay
Equations:
n = Number of half life cycles =
Time passed
Half life of isotope
Original amount(g) x 0.5n = Final remaining amount(g)
Final amount (g) x 2n = Original amount (g)
Radiation Units
Gray (Gy): One joule of energy per kilogram of tissue; absorbed dose
Rad: Absorbed dose
Becquerel (Bq): Measure of actual radioactivity in material; S.I. unit
Curie (Ci): Activity of radioactive source
Sievert (Sv): Takes into account biological effects of different types of radiation
REM: Converted dose-equivalent from rads or grays; biologically effective dose
Roentgens: Intensity of radiation source
Dose Equivalent (DE): may be regarded as an expression of dose in terms of
its biological effect.
Conversions:
1 Bq = 1 disintegration per second (dps)
1 Ci = 3.7 x 1010 dps
1 Ci = 3.7 x 1010 Bq
1 gray = 100 rads
1 sievert = 100 rem
1 becquerel = 27 picocuries or 2.7 x 10-11 curies
Sources of Radiation



Two types of radiation: nonionizing and ionizing
Grays (Gy) measure the energy of radiation
absorbed by the target in joules per kilogram.
Rems (Sv) measure dose quantity in joules per
kilogram.

The Rems and Grays both measure the effect of
radiation on the target, but the rem takes into account
the effects of different types of radiation on human
tissue.
Some forms of Exposure

Amount of exposure differs.

Sun’s ultraviolet rays

Water

Atmosphere

Electromagnetic fields

Nuclear bombs and reactors

Occupation
Nonionizing Radiation



The kind we are exposed to day-to-day (i.e. lowfrequency electromagnetic fields)
Generally harmless
Electric appliances, power lines, radio/TV broadcasting,
thunderstorms, radar, telecommunicates, light, etc.




Can pass through human bodies without apparent
effects
Microwaves: high intensities can cause heating of tissue and
burn injuries to skin
Ultraviolet: cause skin cancer
Cell phones: expose sensitive parts of the human body to
radiation; try not to use often
Ionizing Radiation



The more dangerous type
Where radioactive particles remove the valence
electrons of the elements in living materials and
changes the chemical reactivity of the affected atoms.
Damages biological molecules (proteins/nucleic acids)
and ruptures cell membranes.
Biological Effects
Dosage (Gy)
Damage
>100
Central nervous system; loss of coordination and death
within 1-2 days
9-100
Gastrointestinal tract; nausea, vomiting, and diarrhea.
Dehydration results in death in several weeks
3-9 (Therapy)
Bone marrow damage, loss of appetite and hair,
hemorrhaging, inflammation, and secondary infections
<3
Non lethal, but can cause loss of appetite and hair,
hemorrhaging and diarrhea.
**Average exposure for a U.S. resident is around 0.36 Rem per year
2 mSv/year
Typical background radiation experienced by everyone (av 1.5 mSv in Australia, 3 mSv in
North America).
1.5 to 2.0 mSv/year
Average dose to Australian uranium miners, above background and medical.
2.4 mSv/year
Average dose to US nuclear industry employees.
up to 5 mSv/year
Typical incremental dose for aircrew in middle latitudes.
9 mSv/year
Exposure by airline crew flying the New York - Tokyo polar route.
10 mSv/year
Maximum actual dose to Australian uranium miners.
20 mSv/year
Current limit (averaged) for nuclear industry employees and uranium miners.
50 mSv/year
Former routine limit for nuclear industry employees. It is also the dose rate which arises from
natural background levels in several places in Iran, India and Europe.
100 mSv/year
Lowest level at which any increase in cancer is clearly evident. Above this, the probability of
cancer occurrence (rather than the severity) increases with dose.
350 mSv/lifetime
Criterion for relocating people after Chernobyl accident.
1000 mSv/cumulative
Would probably cause a fatal cancer many years later in 5 of every 100 persons exposed to it
(ie. if the normal incidence of fatal cancer were 25%, this dose would increase it to 30%).
1000 mSv/single dose
Causes (temporary) radiation sickness such as nausea and decreased white blood cell count,
but not death. Above this, severity of illness increases with dose.
5000 mSv/single dose
Would kill about half those receiving it within a month. (The 28 people who died within four
months of the Chernobyl disaster appear to have received more than 5000 mSv in a few days,
while those who sufered acute radiation sickness averaged doses of 3400 mSv.)
10,000 mSv/single dose
Fatal within a few weeks.
 Invented
Geiger.
from a German Physicist Hans
 Works
by measuring the amount of
ionization produced.
 Radiation particles enter the tube and turn
into ions.
 Ions are electrically charged.
The Geiger Counter Are:
1) Nuclear Chemist
2) nuclear power plants
3) Teachers
4) emergency services
5) HAZMAT
6) Homeland security
7) EMT’s
8) Golf
ball companies.
 The
detector uses americium- 241.
 It sends out a beam of neutrons in a straight line
 When smoke enter the detector the smoke
breaks the line, and that’s when it rings.
Conclusion…
The present advancement in the understanding of
nuclear radiation has been brought about by numerous
people through years of research and experimentation.
Its complexity is shown in the many units involved. This
exploration has guided you through the fundamentals of
nuclear radiation. It is now your turn to dive deeper into
the areas specific to your interests. Perhaps one day
your name will be written in the book of radioactive
history…
Works Cited
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Achey, Phillip M. ""Radiation Biology"" McGRAW-HILL ENCYCLOPEDIA OF Science & Technology. 9th ed. 15
vols. Chicago, IL: McGraw-Hill, 2002.
Farndon, John . "The Curies." MAS Ultra - School Edition. 11/08/07
<http://search.ebscohost.com/login.aspx?direct=true&db=ulh&AN=9389372&site=src-live>.
Harvey, Blatt. America's Environmental Report Card. Cambridge, MA: MIT P, 2005.
Hicks, Jennifer. "Harriet Brooks: Working with Radioactivity ." Ebsco. 11/08/07
<http://search.ebscohost.com/login.aspx?direct=true&db=mih&AN=19998096&site=src-live>.
"Images SI INC." Images SI INC. 2007 . Images SI, Inc. 12 Nov 2007 <http://www.imagesco.com/>.
Lerner, K. Lee, and Lerner W. Brenda, eds. "Radioactive Fallout." The GALE ENCYCLOPEDIA of SCIENCE. 3rd
ed. 5 vols. Detroit, MI: Thomson Gale, 2004.
Lerner, K. Lee, and Lerner W. Brenda, eds. "Radioactive pollution." The GALE ENCYCLOPEDIA of SCIENCE.
3rd ed. 5 vols. Detroit, MI: Thomson Gale, 2004.
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2005.
"Radioactive Smoke Alarms." Radioactive Smoke Alarms. December 1999. 12 Nov 2007
<http://www.ccsa.asn.au/nic/UraniumUse/Smokealarms.htm>.
“Radioactivity ." Columbia Encyclopedia. 11/08/07
<http://search.ebscohost.com/login.aspx?direct=true&db=umh&AN=IXBradioact&site=src-live>.
Settle, Frank. "The Biological Effects of Nuclear Radiation." Chemcases. 2005. National Science
Foundation. 9 Nov. 2007 <http://www.chemcases.com/2003version/nuclear/nc-14.htm>.