Introduction to
Radioisotopes:
Measurements and
Biological Effects
UW Radiation Safety Training Manual
Chapter 1: 1-3, 7 - 19
Chapter 2: 21 – 30 http://popularlogistics.com/wpcontent/uploads/2011/03/symbol_radiation_lg1.gif

WHAT IS AN ELEMENT?

A substance that can not be broken down into simpler substances by ordinary chemical processes
• Protons
• Electrons
• Neutrons

The structure of the atom

Nucleus: dense central core formed by neutrons and protons.
Electrons orbit in various energy levels.
 atomic number
(Z) = # protons in atom http://www.sciencewithmrmilstid.com/media/atom.jpg


All atoms of an element have the same number of protons but can have different number of neutrons.

Mass number = # neutrons + # protons


Different nuclear configurations of an element are called isotopes http://www.geog.ucsb.edu/~williams/hydrogen_isotope_masses.jpg


The process by which unstable isotopes try to stabilize by rearranging their nuclear configuration and releasing energy

Usually change in atomic number http://www.ipj.gov.pl/common/images/dszd/glossary/en/radioactiv e-atom.gif


The process of giving off energy during nuclear rearrangement

Radioisotopes http://www.bu.edu/orccommittees/files/2010/05/radioisotopes.gif

Types of
Radiation:
 particles




2 neutrons + 2 protons with total charge = +2
Very short range in air
Usually not a hazard to workers
Internally , dangerous http://www.daviddarling.info/images/alpha_decay.jpg

Types of Radiation:
 particles
 charge = -1

Energy is emitted at various levels
• Low energy beta are only an internal hazard
• High energy beta (like 32 P) internal and external http://library.thinkquest.org/3471/tritium_decay.gif

Types of Radiation:
 and X-rays

Electromagnetic rays http://radchem.nevada.edu/classes/chem312/images/gamma%2
0decay.jpg



Each isotope has a distinct decay rate
Physical half-life = T
1/2
 the time required for a radioisotope to decrease to one-half its original amount http://www.cna.ca/curriculum/cna_radiation/images/gamma5-lg.jpg



NOT a linear process
Think of isotope with a half-life of 2 weeks:

Start with 1000 atoms:
Time (weeks elapsed): # atoms remaining:
0 1000
6
8
2
4
500
250
125
62.5


The # of nuclear decays / second = activity http://faculty.sdmiramar.edu/fgarces/zCourse/All_Year/Ch100_M
M/aMy_FilesLab/05LbMM_ActEx/Act05_NuclearChem/NuclearC hem_pic/HalfLife.gif



Curie = 3.7 X 10 10 dps
Becquerel = 1 dps


Radiation with sufficient energy to directly or indirectly cause electron ejection http://www.niu
cause another atom to release an electron .edu/ehs/images/ionizing%20radiation.jpg


Deposit energy other places than in the worker ’ s tissues


Radiation with energy to penetrate the outer layer of skin and deposit energy deep inside body tissues

3 major types
• Gamma and X-rays
• Neutrons
• High energy beta particles


Inhalation, ingestion, absorption through the skin

Metabolized and stored in body depending upon where element is needed




Roentgen (refers to gamma and x-rays)
Rad: radiation absorbed dose
The amount of damage done by 1 rad of alpha particles is much greater than the amount of damage by 1 rad of high energy beta particles.


Rem = unit of dose equivalence

Rem = rad X Q
• Q ranges from
1 to 20 http://alpcentauri.info/img8B.jpg

Biological Effects of
Radiation


Free radical formation
Can also directly interact with cellular components like DNA and damage them http://jolisfukyu.tokai-sc.jaea.go.jp/fukyu/miraien/2008/img/honbun/6-10.jpg

Possible outcomes of radiation-induced cell damage


 repair
 damaged cell repairs itself cell death mutations
 change in DNA which can eventually lead to cancer

Cells most susceptible to radiation damage
Cells that are:
 rapidly dividing

 have many future divisions undifferentiated http://www.encognitive.com/files
/images/development-of-cancerionizing-radiation.gif


Somatic: Arise directly from radiation damage and only occur in irradiated person

Hereditary: Arise in reproductive cells so damage can be passed on to future generations


Acute exposure

200 rad = more than most lifetime exposures
• blood changes
• nausea, vomiting, hair loss
• diarrhea, dizziness, nervous disorders, hemorrhage

Stochastic vs. Nonstochastic Effects

 stochastic effect arises from injury to one or a few cells
 all or none event non-stochastic effects are somatic effects
 increasing severity with increasing radiation dose