UNIVERSITI TEKNIKAL MALAYSIA MELAKA
PRELIMINARY STUDY AND MEASUREMENT OF CUTTING
TOOL COATING THICKNESS BY USING ALPHA THICKNESS
GAUGING METHOD
This report submitted in accordance with requirement of the Universiti Teknikal
Malaysia Melaka (UTeM) for the Bachelor Degree of Manufacturing Engineering
(Manufacturing Process) with Honours.
by
NURAZLINA BINTI IBRAHIM
FACULTY OF MANUFACTURING ENGINEERING
2010
UNIVERSITI TEKNIKAL MALAYSIA MELAKA
BORANG PENGESAHAN STATUS LAPORAN PROJEK SARJANA MUDA
JUDUL: PRELIMINARY STUDY AND MEASUREMENT OF CUTTING TOOL COATING
THICKNESS BY USING ALPHA THICKNESS GAUGING METHOD
SESI PENGAJIAN : 2009/2010 Semester 1
Saya NURAZLINA BINTI IBRAHIM
mengaku membenarkan Laporan PSM ini disimpan di Perpustakaan Universiti
Teknikal Malaysia Melaka (UTeM) dengan syarat-syarat kegunaan seperti berikut:
1. Laporan PSM adalah hak milik Universiti Teknikal Malaysia Melaka dan penulis.
2. Perpustakaan Universiti Teknikal Malaysia Melaka dibenarkan membuat salinan
untuk tujuan pengajian sahaja dengan izin penulis.
3. Perpustakaan dibenarkan membuat salinan laporan PSM ini sebagai bahan
pertukaran antara institusi pengajian tinggi.
4. **Sila tandakan (√)
SULIT
TERHAD
√
(Mengandungi maklumat yang berdarjah keselamatan
atau kepentingan Malaysia yang termaktub di dalam
AKTA RAHSIA RASMI 1972)
(Mengandungi maklumat TERHAD yang telah ditentukan
oleh organisasi/badan di mana penyelidikan dijalankan)
TIDAK TERHAD
Disahkan oleh:
(TANDATANGAN PENULIS)
(TANDATANGAN PENYELIA)
Alamat Tetap:
LADANG FELDA SEMARING,
P.O.BOX NO.7 AMBS,
23400 DUNGUN, TERENGGANU.
Cop Rasmi:
Tarikh: 25th MAY, 2010
Tarikh: 25th MAY, 2009
** Jika Laporan PSM ini SULIT atau TERHAD, sila lampirkan surat daripada pihak berkuasa/organisasi
berkenaan dengan menyatakan sekali sebab dan tempoh laporan PSM ini perlu dikelaskan sebagai SULIT
atau TERHAD.
DECLARATION
I hereby, declared this report entitled “Preliminary Study and Measurement of Cutting
Tool Coating Thickness by Using Alpha Thickness Gauging Method” is the results of my
own research except as cited in references.
Signature
:…………………………………
Author’s Name
: NURAZLINA BINTI IBRAHIM
Date
: 25th MAY, 2010
APPROVAL
This PSM submitted to the senate of UTeM and has been as partial fulfillment of the
requirements for the degree of Bachelor of Manufacturing Engineering (Manufacturing
Process). The member of the supervisory committee is as follow:
……………………………………
En. Mohamad Nizam Bin Ayof
Main Supervisor
ii
ABSTRACT
Coatings thickness of cutting tool perform a variety of important functions including
protecting and improving the performance in machining. Accurately, measuring the
thickness of these coatings helps maintain product quality and control production costs.
These projects are preliminary study and measure the cutting tool coating thickness by
using Alpha Thickness Gauging Method. This project highlights the consideration of
effects on the accuracy of measurement when using this method. Radioactive material
used in the experiments is Radium-226 and Americium-241, while the coating material
to be measured is made of Aluminum Titanium Nitride (TiAIN). There have 10 types of
cutting tools that used in different coating thickness to be measured. Measurement
readings are displayed on the Gieger Muller Counter which records the number of
particles detected by Counter Tube - Type B. All measurement data is recorded in the
table and based on the data, the graph was plotted to compare the accuracy of the
measurement reading between Alpha Thickness Gauging Method and destructive
method of Scanning Electron Microscope (SEM). Verification was performed on the
graph to determine the accuracy of the measurement readings obtained from the
experiment using a sample of unknown coating thickness. Results showed that the use of
radioactive material Americium-241 can produce better measurement readings than the
use of Radium-238. During the experiment carried out several factors that have affected
the accuracy of the measurement readings were detected. In future study, these factors
can be improved in order to produce more accurate measurement readings.
i
ABSTRAK
Ketebalan lapisan mata alat merupakan suatu fungsi yang penting untuk melindungi dan
meningkatkan prestasi pemotongan dalam pemesinan. Dengan lebih tepat lagi,
pengukuran ketebalan lapisan mata alat ini mampu mengekalkan kualiti produk dan
mengawal kos pengeluran. Projek ini adalah untuk mengkaji dan mengukur ketebalan
lapisan mata alat dengan menggunakan Kaedah Tolok Ketebalan Alpha. Projek ini
mengetengahkan pertimbangan terhadap kesan kepada ketepatan pengukuran apabila
menggunakan kaedah ini. Bahan radioaktif yang digunakan sebagai ujikaji dalam projek
ini adalah Radium-226 dan Americium-241, sementara bahan lapisan pada mata alat
yang di ukur adalah diperbuat daripada Aluminum Titanium Nitride (TiAIN). Terdapat
10 jenis mata alat yang digunakan mempunyai ketebalan yang berbeza untuk di ukur.
Bacaan pengukuran tertera pada Kaunter Gieger Muller yang mana berfungsi untuk
rekod jumlah zarah yang dikesan oleh Kaunter Tiub – Jenis B. Semua data pengukuran
direkodkan di dalam satu jadual dan berdasarkan data tersebut, graf yang telah diplot
untuk membandingkan ketepatan bacaan pengukuran antara Kaedah Tolok Ketebalan
Alpha dan kaedah pemusnah iaitu Scanning Elektron Microscope (SEM). Pengesahan
telah dilakukan ke atas graf tersebut bagi menentukan ketepatan bacaan pengukuran
yang diperolehi daripada hasil experimen menggunakan sampel tidak diketahui
ketebalan lapisannya. Keputusan menunjukkan bahawa penggunaan bahan radioaktif
jenis Americium-241 dapat menghasilkan bacaan pengukuran yang lebih baik
berbanding jenis Radium-238. Sepanjang experimen dijalankan terdapat beberapa faktor
yang telah mempengaruhi ketepatan bacaan pengukuran telah dikesan. Bagi kajian akan
datang, faktor-faktor ini boleh diperbaiki agar dapat menghasilkan bacaan pengukuran
yang lebih tepat.
ii
DEDICATION
To my beloved parents, Mr. Ibrahim Bin Mamat and Mrs. Rohanah Binti Zahari, thank
you for your support and thanks for everything. My sisters and brothers, thank you for
encouraging me to do well in this writing.
iii
ACKNOWLEDGEMENTS
In the name of Allah, the most gracious, the most merciful, Alhamdulillah and
grateful with permission from Allah I have done my Projek Sarjana Muda activities.
Firstly, special thanks dedicated to Universiti Teknikal Malaysia Melaka for giving the
cooperation while doing this study and especially to all staff in Faculty of Manufacturing
Engineering. Also a lot of thank to my family for their support because without their
mental and physical supported it won’t be easy for me to complete this study. Special
thanks to the important person, my supervisor whose guides me in this study En.
Mohammad Nizam Bin Ayof. This person that gave me a lot advices and guidelines to
make sure this study can be performed smoothly without any problem and produce the
best result.
Also I would like to wish my greatest grateful especially to my family and my
close friends for all their support. Finally, I would like to wish thank you a lot to
anybody who has given all the support and contribution to me in this study. May Allah
bless all of you.
iv
TABLE OF CONTENT
Abstract
i
Abstrak
ii
Dedication
iii
Acknowledgement
iv
Table of Content
v
List of Tables
ix
List of Figures
x
List of Abbreviations
xii
1. INTRODUCTION
1.1
Background of the Project
1
1.2
Objective
2
1.3
Problem Statement
2
1.4
Scope
2
2. LITERATURE REVIEW
2.1
Introduction
3
2.2
Coating of Cutting Tool
3
2.3
Cutting Tool Material
4
2.4
Coating Thickness Measurement
5
2.4.1
Destructive Tests
6
2.4.2
Non-destructive Test (NDT)
7
2.4.2.1 A Method to Measure the Mean Thickness and Non-uniformity of Non-
7
Uniform Thin Film by Alpha-Ray Thickness Gauge
2.5
Radioactive Source
8
2.5.1
Concept of Ionizing Radiation
8
2.5.1.1 Atoms and Ions
9
2.5.2
9
Ionizing Process
v
2.5.3
Sources of Ionizing Radiation
10
2.5.3.1Radioactive Materials
10
2.5.3.2Machine Generator
11
2.5.4
Characteristics of Ionizing Radiation
12
2.5.5
Exponential Decay
14
2.5.6
The Half Life
15
2.5.7
Quantity and Unit
16
2.5.8
Applications of Ionizing Radiation
17
2.5.8.1Area of Applications
18
2.5.9
Radium
20
2.5.9.1 Use of Radium
20
2.5.9.2 The Affect in the Body
21
2.5.9.3 Primary Health Effect
21
2.5.10 Americium-241
22
2.5.10.1Radioactivity and Decay
23
2.5.10.2Use of Americium
24
2.6
Gauging
24
2.6.1
Bulk Density
24
2.6.2
Alpha-Particle Transmission
25
2.6.3
Thickness
26
2.6.3.1 Alpha Particles
27
2.6.4
Photon Scattering
27
2.7
Radiation Detector
28
2.7.1
Purposes and Properties of Detector Systems
29
2.7.2
Geiger-Muller Counters
29
2.8
Calibration Term of Coating Thickness Gages
32
3. METHODOLOGY
3.1
Introduction
35
3.2
Flow Chart of PSMI and PSMII
36
3.2.1
Project Implementation Procedures
38
vi
3.3
Equipment and materials used
39
3.3.1
The Specification of Radioactive Materials
40
3.3.2
The Specification of Coating Materials
42
3.3.3
Cutting Tool Material
43
3.3.3.1 The Properties of Sintered Tungsten Carbide
43
3.3.4
Vacuum Machine
43
3.3.5
The Equipment of Alpha Thickness Gauging Method
45
3.4
The Procedure to Coat the Cutting Tool
47
3.5
The Flow Chart of the Measurement Procedure by Using Alpha
50
Thickness Gauge
3.5.1
Procedure of Measure the Coating Thickness by Using Alpha
51
Thickness Gauge
4. RESULT AND DISCUSSION
4.1
Introduction
53
4.2
Result of Coating Thickness Measurement by Alpha Thickness Gauge
53
(Nondestructive Method)
4.2.1
Coating Thickness Measurement Using Radium-238
55
4.2.2
Coating Thickness Measurement Using Americium-241
56
4.3
Result of Coating Thickness Measurement by Scanning Electron
57
Microscope (Destructive Method)
4.4
Comparison of Coating Thickness Measurement Result between
58
Alpha Thickness Gauging Method and Scanning Electron Microscope
(SEM) Method
4.4.1
Graph of Backscattering Rate (Counts/60s) versus Coating Thickness
59
(μm) for Coating Thickness Measurement by Using Radium-238
4.4.2
Graph of Backscattering Rate (Counts/60s) versus Coating Thickness
61
(μm) for Coating Thickness Measurement Using Americium-241
4.5
Validation of Graph Using Unknown Thickness Sample
63
4.5.1
Validation of Graph of Coating Thickness Measurement Using
64
Radium-238
vii
4.5.2
Validation of Graph of Coating Thickness Measurement Using
66
Americium-241
4.6
Result Validation
68
4.6.1
Factors Affecting the Measurement Readings
69
4.7
Radiation Protection
72
5. CONCLUSION
5.1
Conclusion
74
5.2
Recommendations for Future Study
75
REFERENCES
77
APPENDICES
A
Ghant Chart of PSM I
B
Ghant Chart of PSM II
viii
LIST OF TABLE
2.1
Half-life for radioactive element
12
3.1
The Principle Emissions
40
3.2
The Specification of Radium-226 and Uranium-238
41
3.3
Specification of Titanium-Aluminum-Nitride (TiAIN)
42
3.4
Sumitomo SPGN120308S cutting tool dimensions
48
4.1
Data Collection of Measurement Using Radium-238
55
4.2
Data Collection of Measurement Using Americium-241
56
4.3
Data Collection of Measurement Using Scanning Electron Microscope
58
(SEM) Method
4.4
Data of Coating Thickness by SEM (μm) and Average Counts/60s by
59
Radium-238
4.5
Data of Coating Thickness by SEM (μm) and Average Counts/60s
61
by Americium-241
4.6
The Value of Counts/60 for Unknown Thickness Using Radium-238
64
4.7
The Value of Counts/60 for Unknown Thickness Using Americium-241
66
ix
LIST OF FIGURE
2.1
Types of Ionizing Radiation
13
2.2
Weld X-Ray
19
2.3
Using Radiation to Control Paper Thickness
20
2.7
Geiger Muller Tube Cross Section Depicting the Progression of the Geiger
Discharge
31
2.8
Two Commercial Hand Held Portable Gas-Filled Detectors.
33
3.1
The Flow Chart of the PSMI
36
3.2
The Flow Chart of the PSMII
37
3.3
Vacuum PVD System
44
3.4
Base Plate
45
3.5
The Counter Tube Holder, Source Holder and Plate Holder
45
3.6
The Thick Lead Plate
45
3.7
Counter Tube – Type B
46
3.8
Geiger Muller Counter – Phywe
46
3.9
Source Ra-226
46
3.10
PVD Unbalanced Magnetron Sputtering System VACTEC Korea
Model VTC PVD 1000
47
3.11
Substrate Holder inside Coating Chamber
47
3.12
Tungsten Carbide Cutting Tool insert commercially made by Sumitomo
48
3.13
The Flow Chart of the Measurement Procedure
51
4.1
The Measurement of Coating Thickness by Alpha Thickness Gauging
54
Method
4.2
Two Types of Alpha Radioactive Source; (a) Americium-241 and
54
(b) Radium-238
4.3
The Image of Cutting Tool Coating Thickness (Measure by Scanning
Electron Microscope (SEM))
x
57
4.4
Graph of Backscattering Rate (Counts/60s) vs. Coating Thickness (μm)
60
for Coating Thickness Measurement by Using Radium-238
4.5
Graph of Backscattering Rate (Counts/60s) vs. Coating Thickness (μm)
62
for Coating Thickness Measurement Using Americium-241
4.6
The Trend Equation for Measurement Using Radium-238
64
4.7
The Trend Equation for Measurement Using Americium-241
66
4.8
Sample of Cutting Tool
69
4.9
The Image of Cutting Tool Coating Thickness; (a) Coating Thickness is
70
Uniform and (b) Coating Thickness is Non-Uniform
4.10
Position of the Double-Sided Tape and Samples of Cutting Tool on the
Plate Holder
xi
71
LIST OF ABBREVIATIONS
HSS
-
High Speed Steel
CVD
-
Chemical Vapor Deposition
PVD
-
Physical Vapor Deposition
ANSI
-
American National Standard Institute
NDT
-
Non-Destructive Test
Ra-238
-
Radium-238
Am-241
-
Americium-241
Pu-239
-
Plutonium-239
Co-60
-
Cobalt-60
UV
-
Ultra Violet
TiAIN
-
Titanium-Aluminum-Nitride
WC
-
Tungsten Carbide
SEM
-
Scanning Electron Microscope
xii
CHAPTER 1
INTRODUCTION
1.1
Background of the Project
Coating thickness is an important variable that plays a role in product quality, process
control and cost control. Measurement the thickness of cutting tool can be done with
many different instruments. Commonly used measuring techniques for coating thickness
of cutting tool include destructive coating thickness such as micrometer, vernier caliper
and microscope. Understanding the equipment that is available for coating thickness
measurement and how to use it is useful to every coating of cutting tool.
This project will study and do analysis on measurement the coating thickness of cutting
tool by using radioactive alpha source which is alpha thickness gauging method. The
alpha thickness gauging method is nondestructive coating thickness which consists of
two basic components; a source of radiation, and a radiation detector. The cutting tool to
be measured is placed between the source and detector.
The project will broadly involve a few tasks such as developed nondestructive method to
measure the coating thickness of cutting tool by using alpha thickness gauging method
and compare with destructive method.
1
1.2
Problem Statement
Measurement the coating thickness of cutting tool commonly used destructive
measuring techniques such as height measurement (measuring before and after with a
micrometer) and optical cross-sectioning (cutting the coated part/tool and viewing the
cut microscopically). These techniques are time-consuming, difficult to perform and are
subject to user interpretation and other measurement errors. Although this method’s
principles are easy to understand, opportunities abound for introducing errors. It takes
skill to prepare the sample and interpret the results. Also, adjusting the measurement
reticule to a jagged or indistinct interface can generate inaccuracy, particularly between
different users. This method is used when inexpensive, nondestructive methods aren't
possible, or as a means of confirming nondestructive test results.
1.3
i.
Objectives
To develop a method to measurement the cutting tool coating thickness by using
alpha thickness gauging method.
ii.
To investigate the accuracy of alpha thickness gauging method.
iii.
To identify factors which influenced measurement the coating thickness of
cutting tools by using alpha thickness gauge.
1.4
Scope
The project will involve the experimentation on the several critical factors should be
considered when evaluating instrument in measurement the coating thickness of cutting
tool. Some of the consideration need to be evaluated is the variation within the sample
being measured, resolution of the readings and the accuracy of the actual measurement.
2
CHAPTER 2
LITERATURE REVIEW
2.1
Introduction
Literature review or academic study is one earlier research process to help in process
introduce new method for measurement the coating thickness of cutting tool. Through
this method early retrieval on a project weakness and advantage will be acquired through
study method and comparison with present method / equipment. With this literature
review also a product produced can fulfill current need without fomenting.
2.2
Coating of Cutting Tool
Coatings have become such an indispensable part of most cutting tool grades that 70 75% of all carbide tools are now coated. Coatings improve wear resistance, they increase
tool life, and they broaden the application range of a given grade, and enable use at
higher speeds. By improving performance, coatings are helping cutting tool
manufacturers respond to changing workpiece materials and process requirements.
Today's machining operations can involve high-speed machining, dry machining, use of
more near-net-shape workpieces, tighter surface finish and dimensional tolerances, and
increased use of untended machining, which places a premium on edge security and tool
reliability.
Improved wear resistance results from coating materials' high hardness, chemical
inertness, and low coefficients of friction. In uncoated tools, increased wear resistance-
3
obtained by increasing the amount of hard carbides in the material, as described in part 1
of this series of articles--is traded off against lower toughness.
The processes used to add coatings to cutting tools-regardless of whether the substrate is
High Speed Steel (HSS), cemented carbide, cermets, ceramic, or a super hard material-are chemical vapor deposition (CVD) and physical vapor deposition (PVD). The process
selected depends on tool material composition and geometry, and on the intended
application of the tool. (Destefani, 2002)
2.3
Cutting Tool Material
As rates of metal removal have increased, so has the need for heat resistant cutting tools.
The result has been a progression from high-speed steels to carbide and on to ceramics
and other super hard materials.
Developed around 1900, high-speed steels cut four times faster than the carbon steels
they replaced. There are over 30 grades of high-speed steel, in three main categories:
tungsten, molybdenum, and molybdenum-cobalt based grades. Since the 1960s the
development of powdered metal high-speed steel has allowed the production of near-net
shaped cutting tools, such as drills, milling cutters and form tools. The use of coatings,
particularly titanium nitride, allows high-speed steel tools to cut faster and last longer.
Titanium nitride provided a high surface hardness, resist corrosion and it minimizes
friction.
In industry today, carbide tools have replaced high-speed steels in most applications.
These carbide and coated carbide tools cut about 3 to 5 times faster than high-speed
steels. Cemented carbide is a power metal product consisting of fine carbide particles
cemented together with a binder of cobalt. The major categories of hard carbide include
tungsten carbide, titanium carbide, tantalum carbide and niobium carbide. Each type of
carbide affects the cutting tools characteristic differently. For example, a higher tungsten
4
content increase wears resistance, but reduces tool strength. A higher percentage of
cobalt binder increase strength, but lowers the wear resistance.
Carbide is used in solid round tools or in the form of replaceable inserts. Every
manufacturer of carbide tools offers a variety for specific applications. The proper
choice can double tool life or double the cutting speed of the same tool. Shock-resistant
types are used for interrupted cutting. Harder, chemically-stable types are required for
high speed finishing of steel. More heat-resistant tools are needed for machining the
superalloys, like Inconel and Hastelloy.
There are no effective standards for choosing carbide grade specifications so it is
necessary to rely on the carbide suppliers to recommend grades for given applications.
Manufactures do use an ANSI code to identify their proprietary carbide product line.
Two-thirds of all carbides tools are coated. Coated tools should be considered for most
applications because of their longer life and faster machining. Coating broadens the
applications of a specific carbide tool. These coatings are applied in multiple layers of
under 0.001 of an inch thickness. The main carbide insert and cutting tool coating
materials are titanium carbide, titanium nitride, aluminum oxide and titanium carbon
nitride. (Society of Manufacturing Engineers, 2002)
2.4
Coating Thickness Measurement
Coatings perform a variety of important functions including protecting and beautifying
outdoor structures and manufactured goods. Accurately measuring the thickness of these
coatings helps maintain product quality and control production costs.
Several types of instruments are available to measure coatings in their uncured (wet) or
cured (dry) state. Proper instrument selection is crucial to obtaining accurate, meaningful
results. Instrument selection is dependant upon the type and thickness range of the
5
coating, the substrate material, the shape of the part, and the need for statistical analysis.
To make this choice, one must understand the different technologies available for
coating thickness measurement.
Measuring techniques are either destructive or non-destructive. Non-destructive methods
include magnetic, eddy current, ultrasonic, and micrometer measurement. Destructive
methods include cross sectioning and gravimetric (mass) measurement. Methods are also
available for pre-cured liquid and coating powder measurement. (Beamish, 2008)
2.4.1
Destructive Tests
Destructive technique is to cut the coated part in a cross section and measure the film
thickness by viewing the cut microscopically. Another cross sectioning technique uses a
scaled microscope to view a geometric incision through the dry-film coating. A special
cutting tool is used to make a small, precise V-groove through the coating and into the
substrate. Gages are available that come complete with cutting tips and illuminated
scaled magnifier.
While the principles of this destructive method are easy to understand, there are
opportunities for measuring error. It takes skill to prepare the sample and interpret the
results. Adjusting the measurement reticule to a jagged or indistinct interface may create
inaccuracy, particularly between different operators. This method is used when
inexpensive, nondestructive methods are not possible, or as a way of confirming
nondestructive results. ASTM D 4138 outlines a standard method for this measurement
system. (Beamish, 2008)
6
2.4.2
Non-destructive Test (NDT)
Non-destructive testing (NDT) used to detect, inspect, and measure flaws, bond
integrity, and other material conditions without permanently altering or destroying the
examined part or product. (Lomax, 2009)
2.4.2.1 A Method to Measure the Mean Thickness and Non-uniformity of Nonuniform Thin Film by Alpha-Ray Thickness Gauge
The alpha-ray thickness gauge is used to measure non-destructively the thicknesses of
thin films, and up to the present day, a thin film with uniform thickness is only taken up
as the object of alpha-ray thickness gauge. When the thickness is determined from the
displacement between the absorption curves in the presence and absence of thin film, the
absorption curve must be displaced in parallel. When many uniform particles were
dispersed as sample, the shape of the absorption curve was calculated as the sum of
many absorption curves corresponding to the thin films with different thicknesses.
By the comparison of the calculated and measured absorption curves, the number of
particles, or the mean superficial density can be determined. This means the extension of
thickness measurement from uniform to non-uniform films. Furthermore, these particle
models being applied to non-uniform thin film, the possibility of measuring the mean
thickness and non-uniformity was discussed. As the result, if the maximum difference of
the thickness was more than 0.2mg / cm 2 , the non-uniformity was considered to
distinguish by the usual equipment. In this paper, an alpha-ray thickness gauge using the
absorption curve method was treated, but one can apply this easily to an alpha-ray
thickness gauge using alpha-ray energy spectra before and after the penetration of thin
film. (Miyahara, Yoshida and Watanabe, 1977)
7
2.5
Radioactive Source
Radiation sources, utilizing either radioactive materials or radiation generators, are used
throughout the world for a wide variety of peaceful purposes, in industry, medicine,
research and education. They are also used for various military purposes. Many are in
the form of sealed sources with the radioactive materials firmly contained or bound
within a suitable capsule or housing. The risks posed by these sources and materials vary
widely, depending on such factors as the radionuclide, the physical and chemical form,
and the activity. Unless breached or leaking, sealed sources present a risk from external
radiation exposure only. However, breached or leaking sealed sources, as well as
unsealed radioactive materials, may lead to contamination of the environment and the
intake of radioactive materials into the Human body.
The International Basic Safety Standards provide an internationally harmonized basis for
ensuring the safe and secure use of sources of ionizing radiation. Because of the wide
variety of uses and activities of radiation sources, a categorization system is necessary so
that the controls that are applied to the sources are commensurate with the radiological
risks. (Vienna, 1996)
2.5.1
Concept of Ionizing Radiation
The energy emitted by non-ionizing radiation is less than 30  34eV . Radiations that
have the energy above the aforementioned value are categorized as ionizing radiation.
Since they cannot be detected by our senses, special devices must be used. (MINT,
2005)
8