Introduction to Radioisotopes: Measurements and Biological Effects UW Radiation Safety Training Manual Chapter 1: 1-3, 7 - 19 Chapter 2: 21 – 30

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/wp-content/uploads/2011/03/symbol_radiation_lg1.gif

Elements: a review

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

Isotopes All atoms of an element have the same number of

protons but can have different number of neutrons.

Mass number = # neutrons + # protons

Isotopes Different nuclear

configurations of an element are called isotopes

http://www.geog.ucsb.edu/~williams/hydrogen_isotope_masses.jpg

Nuclear Disintegration

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/radioactive-atom.gif

Radioactive Decay

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 32P) 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%20decay.jpg

Half-life

Each isotope has a distinct decay rate Physical half-life = T1/2

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

Half-life: the math NOT a linear process Think of isotope with a half-life

of 2 weeks: Start with 1000 atoms:

Time (weeks elapsed): # atoms remaining:

0 10002 5004 2506 1258 62.5

“Activity”

The # of nuclear decays / second = activity

http://faculty.sdmiramar.edu/fgarces/zCourse/All_Year/Ch100_MM/aMy_FilesLab/05LbMM_ActEx/Act05_NuclearChem/NuclearChem_pic/HalfLife.gif

Activity units

Curie = 3.7 X 10 10 dps Becquerel = 1 dps

Ionizing Radiation Radiation with sufficient

energy to directly or indirectly cause electron ejection

http://www.niucause another atom to release an electron.edu/ehs/images/ionizing%20radiation.jpg

Radiation safety goal

Deposit energy other places than in the worker’s tissues

Types of Hazards: External

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

Types of Hazards: Internal

Inhalation, ingestion, absorption through the skin Metabolized and stored in

body depending upon where element is needed

Measuring radiation: Roentgen vs. Rad

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.

Dose equivalence

Rem = unit of dose equivalence Rem = rad X Q

• Q ranges from 1 to 20

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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/mirai-en/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-cancer-ionizing-radiation.gif

Biological Effects of Radiation

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

Symptoms of Radiation Exposure

Acute exposure 200 rad = more than most

lifetime exposures• blood changes• nausea, vomiting, hair loss• diarrhea, dizziness, nervous

disorders, hemorrhage

Stochastic vs. Non-stochastic 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