L10 datta lecture on industrial radiation sources

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5th BAERA Training Course on Radiation Protection for
Radiation Control Officers (RCOs) of Industrial Practices
Bangladesh Atomic Energy Regulatory Authority
Agargaon, Dhaka
06-09 November 2017
L10: Radiation Sources & Equipment used in NDT, Well-
Logging, Irradiator and Nucleonic Gauge Practices
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Contents
 Radiation and Radioactivity
 Industrial Practices of Radiation Sources
 NDT
 Well-Logging
 Irradiator
 Nucleonic Gauge Practices
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 Radiation and Radioactivity

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RADIATION: A form of energy.
What is
Ionization?
Nonionizing radiation
Laser radiation: includes
ultraviolet, visible, and
infrared light
Although ultraviolet light
produces ions, but it is
considered as
nonionizing radiation
Total energy, E = hf = h c/
Electric
waves
-ray is the radiation emitted by nuclei and x-ray refers to radiation originating in transitions of atomic electrons.

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RADIOACTIVITY: Radiation from an unstable atom.
Diameter of an atom~10-10 m
Diameter of a nucleus~10-14 m
Unstable nuclei emit radiation.
How can you determine stability?

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Nuclear Stability
If there are either too many or too few neutrons for a given number of protons, the
resulting nucleus is not stable and it undergoes radioactive decay.
 The number of isotopes for each element varies from 3 to 29.
 Of about 1800 different nuclides known, only about 20% are stable.
 The stability of the nucleus depends on the ratio of neutrons to protons.
 The number of protons for known nuclides is shown plotted against the number of neutrons in above
figure.
 Pl. Notice: There are more neutrons than protons in nuclides with Z>20 (Ca)
Lacking in neutron:
+ decay, p is transformed into neutron
Excess in neutron:
- decay, n is transformed into proton


 N
O 15
7
15
8


 
F
O 19
9
19
8



Zero rest mass
No electrical charge
Both forms of -decay, the emitted electrons
appear with a continuous energy spectrum
max
max
3
.
0
:
4
.
0
:
E
E
E
E









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Laws of radioactive
decay
 N = number of radionuclide atoms
present at time t
 A = activity
 =decay constant
 t1/2 = half-life (specific property)
t
t
o
t
t
o
t
t
o
t
o
e
A
A
a
from
e
N
N
t
t
e
e
N
N
a
e
N
N
N
dt
dN
N
dt
dN
A































































2
1
2
1
2
1
2
1
693
.
0
693
.
0
2
1
2
1
0
]
_
[
693
.
0
2
ln
2
1
2
]
[







Einstein’s theory of relativity
• Einstein’s 1905 theory of relativity states that energy and matter
are equivalent, being different manifestations (appearance) of the
same thing.
• Their equivalence is given by: E = mc2
 E = energy (joule)
 m = mass of matter (kg)
 c = velocity of light (3x108 m/s)
• For a proton or a neutron, the energy equivalence of its mass is
 E (1 amu) = (1.67x10-27 kg) x (3x108 m/s)2
= 1.5x10-10 joule
= 931x106 eV (1 eV = 1.6 x 10-19 joules)
= 931 MeV
• Similarly, for an electron, E (me) = 0.51 MeV

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 Industrial Practices of Radiation Sources
 NDT
 Well-Logging
 Irradiator
 Nucleonic Gauge Practices

Beneficial
uses of
radiation
technology.

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Sealed
Sources used
in medicine,
industry and
research

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Activity Range for Various Radionuclide Applications
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 NDT
 GAMMA RADIOGRAPHY SOURCES AND CONTAINERS
 X RAY RADIOGRAPHY EQUIPMENT
 ACCELERATORS
 PIPE CRAWLER EQUIPMENT
 REAL TIME RADIOGRAPHY
 NEUTRON RADIOGRAPHY
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GAMMA RADIOGRAPHY SOURCES AND CONTAINERS
 Reference Books: 10 CFR PART 34--LICENSES FOR INDUSTRIAL RADIOGRAPHY AND
RADIATION SAFETY REQUIREMENTS FOR INDUSTRIAL RADIOGRAPHIC OPERATIONS
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NDT
 Industrial radiography is the process
of using radiation to “see” inside
manufactured products such as
metal castings or welded pipelines to
find out whether the products contain
flaws.
 It is not to be confused with the use
of ionizing radiation to change or
modify objects; radiography's
purpose is strictly viewing.
 Industrial radiography has grown out
of engineering, and is a major
element of nondestructive testing. It
is a method of inspecting materials
for hidden flaws by using the ability
of short X-rays and Gamma rays to
penetrate various materials.
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In February 1896, a
French scientist,
Henri Becquerel,
discovered radiation
coming from a
uranium bearing
mineral.
In December 1895,
a German scientist.
Wilhelm Roentgen,
discovered x-rays.
In 1898, Pierre
(French) and Marie
Curie (Polish)
discovered radiation
coming from radium.
The curie is a non-SI unit defined as that amount of
radioactivity which has the same disintegration rate as
1 gram of Ra-226 (3.7 x 1010 disintegrations per second,
or 37 GBq)

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 Iridium-192 is ideal for radiography, but other radionuclides can be used, depending
on the characteristics of the test object material.
 A sealed radiography source will not make other things radioactive unless the source
is leaking.
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The decay of iridium-192. It takes 75 days for
half of the iridium-192 to decay away. After
75 days an iridium-192 source has lost half
of its radioactivity.
Remember: A 1-cuire iridium source does not give the same
radiation dose as a 1-cuire cobalt source, why?
The iridium source and the cobalt source both have exactly
the same number of disintegrations per second, and a
disintegration of each produces about 2 gamma rays. But the
average energy of a gamma rays from cobalt is about twice
as great as the average energy of gamma rays from iridium.
So, the dose rate around the cobalt source will be greater
than the dose around the iridium source.

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 Example:
 Cobalt-60 has a half life of just over 5 years. If we start with 100 curies, how
much will we have in 20 years?
 Answer: Twenty years is equal to 4 half-lives. Therefore, the activity will be
100x1/2x1/2x1/2x1/2 = 6 ¼ curies.
17
D = D0
r0
r
æ
è
ç
ö
ø
÷
2

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 Example
 For a 100-curie iridium source, at what distance will the dose rate be 100
mR/hr ? [dose rate at 1 foot from a 1-cuire Iridium-192 source is 5.2 R/hr or
about 5 R/hr and for a 1-cuire Cobalt-60 source is 14.0 R/hr]
 By using the inverse square law,
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D = D0
r0
r
æ
è
ç
ö
ø
÷
2
Þ100mR / hr=100Ci´5R / hr / Ci
1ft
r
æ
è
ç
ö
ø
÷
2
Þr@70 ft....... Ans.
[ ]
If Maximum permissible doses (MPDs) = 5 rems/year = 50 mSv/year = 5
R/year, then calculate the safe distance. [1 year = 50 week x 5 days x 8 hours]

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 Must follow this guidelines:
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Class P: Portable exposure container, designed to be carried by one or
more persons. The mass of a Class P container does not exceed 50 kg.
Class M: Mobile, but not portable, exposure container designed to be
moved easily by a suitable means provided for the purpose, for example
a trolley.
Class F: Fixed, installed exposure container or one with mobility
restricted to the confines of a defined working location, such as a
shielded enclosure.

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Each exposure container or a metallic plate fixed to the container is to be permanently and
indelibly marked by engraving, stamping or other means with approved details including:
(a) the basic ionizing radiation symbol complying with the International Organization for
Standardization (ISO 361);
(b) the word RADIOACTIVE in letters not less than 10 mm in height;
(c) the maximum rating of the exposure container for the intended radionuclides in (Bq);
(d) ISO 3999 [10] or equivalent standard and edition which the exposure container and its
accessories conform to;
(e) the exposure container manufacturer’s name, the model number and serial number of the
device;
(f) the class, category and total mass of the exposure container;
(g) the mass of depleted uranium shielding, if applicable, or the indication ‘Contains depleted
uranium.’
In addition, the exposure container displays a durable fireproof label or tag bearing information
about the radioactive source contained in the exposure device, including:
(a) the chemical symbol and mass number of the radionuclide;
(b) the activity and date on which it was measured in Bq (or Ci);
(c) the identification number of the sealed source; and
(d) the identity of the source manufacturer.
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X RAY RADIOGRAPHY EQUIPMENT
 Two types of portable X ray tube assemblies (also called tubeheads) are common for
performing panoramic (radial beam) and directional exposures.
 The tube assembly is connected by cable to the control panel.
 The dose to the radiographer is affected by the
 cable length, X ray tube parameters and the tube assembly.
 Where radiography cannot be carried out in a shielded enclosure, cable lengths
typically are no less than 20 m for X ray generators up to 300 kV and longer for
equipment with higher tube potentials.
 Cables are laid out as straight as possible to maximize the benefit of distance
between radiographer and tube assembly.
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 The following features of the X ray assembly are necessary:
 Leakage radiation penetrates the wall of the X ray tube assembly to produce dose
rates other than those in the main beam. The penetrating power of leakage radiation
depends on the tube voltage and is particularly important when X ray tubes are
operated at more than 500 kV.
 Data on the maximum dose rates due to leakage radiation at the assembly’s surface
and at 1 m from the tube target are documented by the manufacturer and are
available for review by the Regulatory Authority. Typical maximum dose rate values
of leakage radiation from commercial assemblies are up to 100 μSv·h-1 at 1 m from
the target.
 The X ray tube assembly has a support that maintains the tube position without
tipping, slipping or vibrating during the operation of the machine.
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X RAY RADIOGRAPHY EQUIPMENT

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ACCELERATORS
 Accelerators can be used to generate high energy X rays (typically, 5 MeV) for radiographic
examinations requiring highly penetrating radiation.
 If the object to be radiographed will fit into an enclosure, then the X rays can be generated by a
large accelerator. This can be a linear accelerator housed in a shielded room adjacent to the
shielded radiography enclosure.
 Radiographic examinations of large structures such as bridges are done on site, and accelerators
for this type of work are smaller, usually cyclotrons.
 A mobile accelerator may be mounted on a large vehicle (e.g. truck) with the accelerator head
being mounted on a gantry to enable positioning of the radiation beam.
 A portable accelerator (Fig. 9) can be transported in a small vehicle (e.g. car) and carried into
position by the radiographers. The portable accelerator weighs approximately 100 kg, with the
ancillary equipment (e.g. controller, control panel, warning signals) being of similar weight.
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PIPE CRAWLER EQUIPMENT
 Pipe crawler equipment is used to radiograph welds on pipelines.
 The machines carry either an X ray tube assembly or a gamma source on a mobile
carriage which crawls along the inside of the pipe.
 They are powered either by batteries on the carriage, an internal combustion engine
or trailing cables from a generator.
 The crawler is activated and controlled by the radiographer from outside the pipe by
using a control source which normally consists of a low activity (137Cs) sealed
source mounted in a hand-held device and collimated.
 Radiation from the control source is received by a detector on the crawler. Typically,
the control source is moved along the outside of the pipe to initiate the crawler to
move in the desired forward or reverse direction.
 The control source is held against the outside of the pipe to make the crawler stop
and wait, and an exposure begins automatically about 10 s after the control source is
abruptly removed from the pipe’s surface. Some X ray crawlers are fitted with a low
activity ‘tell-tale’ radioactive source to help to identify the crawler’s position in the
pipeline.
 The pipe crawler and the control source are to be prepared and transported in
accordance with the requirements of IAEA Safety Standards Series No. ST-1 [7]. A
gamma pipeliner crawler is shown in Fig. 10, and Fig. 11 shows the general
construction.
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REAL TIME RADIOGRAPHY
 A variety of exposure devices are in use or under development for special applications.
 In order to keep pace with faster welding techniques and commercial production needs, real time
radiography, which is also called fluoroscopic imaging, uses digitally processed images displayed
on a high resolution monitor instead of on conventional X ray film.
 The X ray tubehead or exposure container is mounted diametrically opposite a radiation detector.
The objects to be radiographed are brought in front of the exposed source by using a conveyor
system, or the source and the detector are rotated around the object by a computer controlled
motor. Both methods produce a digitized image on a screen.
 The person interpreting the radiographic image views the meter on several monitors and must
decide to accept or reject each image before the system proceeds to the next frame.
 A real time system allows radiography of large cast housings, as shown in Fig. 12.
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NEUTRON RADIOGRAPHY
 Although still in its infancy, neutron radiography is being steadily developed.
 The range of applications includes the use of steady state and pulsed
beams of neutrons over a range of energies: subthermal, thermal,
epithermal and fast.
 In contrast to X and gamma rays, neutrons more easily penetrate heavy
metals such as steel, lead and uranium but neutrons are absorbed or
scattered in low density hydrogenous substances and certain materials
such as hydrides, boron, plastics, cadmium and gadolinium.
 Neutron sources include both radioisotopes and accelerators.
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Well-Logging
 Reference Books: 10CFR PART 39--LICENSES AND RADIATION SAFETY REQUIREMENTS
FOR WELL LOGGING
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Well Logging
 Well logging sources and devices are generally found in areas where
exploration for minerals is occurring, such as searching for coal, oil, natural
gas, or similar uses.
 The sources are usually contained in long (1–2 m, typically) but thin (<10
cm in diameter) devices which also contain detectors and various electronic
components.
 The actual size of the sources inside the devices is generally small. The
devices are heavy, due to the ruggedness needed for the environments in
which they are to be used.
 The activity of such sources usually ranges from several tens to several
hundreds of GBq. The most commonly used nuclides for gamma sources
are Cs-137 and Co-60 while Am-Be, Cf, and Ra-Be are used as neutron
sources.
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Well Logging
 The source usually consists of a chemical compound of the radionuclide (e.g. americium oxide,
radium sulphate, radium bromide, polonium oxide) mixed with the light element powder (e.g.
beryllium, boron, calcium fluoride, lithium hydroxide).
 The sources contain a significant amount of actinide activity and its mixture with light material
makes leakage a serious radiological hazard.
 Actual logging probes are more complicated and include secondary radiation detection equipment
as well as the power supply and electronic systems associated with radiation detection data
processing and control.
 When dealing with such equipment as waste, design data and associated diagrams, as well as
source removal/replacement procedures, should be available.
 Such sources are regularly transported in Type A or B neutron shielded containers between
facilities, and present no significant transport difficulties.
 Although seen as Category 2 [2], oil well logging sources emit neutrons which cannot be
measured with normal GM tube type detectors. This implies that these sources, when lost, may be
overlooked as dangerous whereas neutrons are many times more biologically damaging than
beta/gamma radiation.
 Furthermore, neutron interaction with matter is strongly dependent on the neutron energy. This
should be observed when dealing with such sources especially for shielding design.

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 There are four common nuclear logging techniques:
(1) The first, sometimes called the gamma measurement technique (different logging companies may
use brand names), simply measures and identifies the gamma rays emitted by naturally occurring
radionuclides in rocks to help distinguish the shale content of sedimentary rocks and aid
lithological identification. The log records the uranium, thorium and potassium content of the
rocks.
(2) The second technique, which provides a neutron–neutron or compensated neutron log,
demands a radioactive source of up to several hundred gigabecquerels of 241Am–Be or Pu–Be in
the tool to emit 4–5 MeV neutrons. An elongated skid hydraulically presses the tool against the
wall of the well and two radiation detectors, located at different distances from the source in the
tool, measure the neutrons backscattered by the rock formation. The relationship between the two
readings provides a porosity index for the rock. This indicates how porous the rock is and whether
it is likely to contain hydrocarbons or water.
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Well Logging

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(3) The third technique uses a tool, the gamma–gamma or density tool, which contains
two detectors and a 137Cs source, usually of up to 75 GBq. The amount of gamma
backscatter from the formation provides the density log that, together with the porosity
log, is a valuable indicator of the presence of gas. A brand name may refer to this
technique.
(4) The fourth technique, termed neutron–gamma logging, employs a tool that houses
a miniature linear accelerator. It contains up to several hundred gigabecquerels of tritium
(3H), a very low energy beta particle emitter. When a high voltage (typically 80 kV) is
applied to the device, it accelerates deuterium atoms (2H) that bombard the tritium target
and generate a large number of very high energy (14–15 MeV) neutrons in pulses lasting
a few microseconds. Certain nuclides become radioactive when hit by this neutron flux,
and their subsequent radioactive decay within the next few milliseconds can be
monitored when the process is repeated a great number of times per second. Either the
gamma radiation emitted as the activated atoms decay or the thermal neutron decay
characteristics are measured to identify the activated species of atoms [14]. The chlorine
or salt water content of the rocks is of particular interest. A brand name may refer to this
technique.
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Well Logging

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Irradiator
 Reference Books: 10CFR PART 36--LICENSES AND RADIATION SAFETY REQUIREMENTS
FOR IRRADIATORS
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Irradiator
 Ionizing radiation can modify physical, chemical and biological properties of the
irradiated materials. At present, the principal industrial applications of radiation are
sterilization of health care products including pharmaceuticals, irradiation of food and
agriculture products (for various end objectives, such as disinfestation, shelf life
extension, sprout inhibition, pest control and sterilization), and materials modification
(such as polymerization, polymer crosslinking and gemstone colourization).
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 A significant impetus was given to the radiation processing industry with the advent of
nuclear reactors, which have the capability to produce radioisotopes. Gamma ray
emitters like cobalt-60 became popular radiation sources for medical and industrial
applications. Many gamma ray irradiators have been built and it is estimated that
about 200 are currently in operation in Member States of the International Atomic
Energy Agency (IAEA). In recent times, the use of electron accelerators as a
radiation source (and sometimes equipped with X ray converter) is increasing.
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Irradiator

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 In a radiation process, a product or material is intentionally irradiated to preserve,
modify or improve its characteristics. This process is carried out by placing the
product in the vicinity of a radiation source (such as cobalt-60) for a fixed time interval
whereby the product is exposed to radiation emanating from the source. A fraction of
the radiation energy that reaches the product is absorbed by the product; the amount
depending on its mass and composition, and time of exposure. For each type of
product, a certain amount of radiation energy is needed to realize the desired effect in
the product; the exact value is determined through research.
 Radioactive material, such as a cobalt-60 source, emits radiation. However, the
product that is irradiated with gamma rays does not become radioactive, and thus it
can be handled normally. This is similar to X ray examination in a hospital for
diagnostic purposes; the patient is exposed to radiation (X rays) but he/she does not
become radioactive.
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Irradiator

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 The radionuclide cobalt-60 (Co-60 or 60Co27) is the most commonly used source of
gamma radiation for radiation technology, both for industrial and medical purposes.
 Production of radioactive cobalt starts with natural cobalt (metal), which is an element
with 100% abundance of the stable isotope cobalt-59. Cobalt-rich ore is rare and this
metal makes up only about 0.001% of the earth’s crust. Slugs (small cylinders) or
pellets made out of 99.9% pure cobalt sintered powder and generally welded in
Zircaloy capsules are placed in a nuclear power reactor, where they stay for a limited
period (about 18–24 months) depending on the neutron flux at the location.
 While in the reactor, a cobalt-59 atom absorbs a neutron and is converted into a
cobalt-60 atom. During the two years in the reactor, a small percentage of the atoms
in the cobalt slug are converted into cobalt-60 atoms.
 Specific activity is usually limited to about 120 Ci/g of cobalt (about 4 °— 1012
Bq/g). After irradiation, the capsules containing the cobalt slugs are further
encapsulated in corrosion resistant stainless steel to finally produce the finished
source pencils in a form such that gamma radiation can come through but not the
radioactive material (cobalt-60) itself (see Fig. 3).
 The required source geometry is obtained by loading these source pencils into
predetermined positions in source modules, and distributing these modules over the
source rack of the industrial irradiator (see Fig. 4).
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Irradiator

42
Irradiator
 Cobalt-60 (60Co27) decays (disintegrates) into a stable (non-radioactive) nickel
isotope (60Ni28) principally emitting one negative beta particle (of maximum energy
0.313 MeV) with a half-life of about 5.27 years (see Fig. 5).
 Nickel-60 thus produced is in an excited state, and it immediately emits two photons
of energy 1.17 and 1.33 MeV in succession to reach its stable state. These two
gamma ray photons are responsible for radiation processing in the cobalt-60
gamma irradiators.
 With the decay of every cobalt-60 atom, the strength or the radioactivity level of the
cobalt source is decreasing, such that the decrease amounts to 50% in about 5.27
years, or about 12% in one year. Additional pencils of cobalt-60 are added
periodically to the source rack to maintain the required capacity of the irradiator.
Cobalt-60 pencils are eventually removed from the irradiator at the end of their useful
life, which is typically 20 years.
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43
 Generally they are returned to the supplier for re-use, recycling or disposal. In about
50 years, 99.9% of cobalt-60 would decay into non-radioactive nickel.
 The current inventory of cobalt-60 in all the irradiation facilities around the world
would amount to more than 250 million curies [6]. Thus, it is important to realize the
vital role the nuclear power reactors play in bringing countless benefits to our lives
through use of cobalt in medical as well as industrial radiation applications.
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Irradiator

44
 Table A.I shows different levels of radiation dose that are relevant for various major
radiation applications. The commercial industrial applications are generally referred to
as ‘radiation processing’ and the relevant dose range may be referred to as ‘radiation
processing dose’ or ‘high dose’.
 Dose rate is the dose given in unit time and is determined by the activity of the
radiation source and the irradiation geometry. It is measured in, for example kGy/h or
Gy/s. Dose rate in a research irradiator can be up to 20 kGy/h. In an industrial facility
(for example, with 3 MCi of cobalt-60), it can be as high as 100 kGy/h near the
source, but on the average it is around 10 kGy/h.
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Irradiator

45
 Nucleonic Gauge Practices
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46
Nucleonic Gauge Practices
 Reference Books
46

47
 There are several hundred thousand nucleonic control systems (NCS) or nucleonic gauges
installed in industry all over the world. They have been widely used by various industries to
improve the quality of product, optimize processes, save energy and materials. The economic
benefits have been amply demonstrated and recognized by industry. Looking at trends in the
industrialization process of developing countries, there is evidence that NCS technology will
continue to play an important role in industry for many years to come.
 Nucleonic control systems (NCS) are defined here as: “Control by instrumental measurement
and analysis as based on the interaction between ionizing radiation and matter”. There are several
ways of applying the NCS, among them:
 􀂃 On-line (process),
 􀂃 Off-line (process),
 􀂃 In situ (well logging),
 􀂃 Used in laboratory (on samples), and
 􀂃 Portable, for site measurements.
 Simple nucleonic gauges first began to be used in industry over forty years ago. Since then, there
has been a continuous expansion in their usage. The competition from alternative methods shows
that NCS have survived and prospered in the past because of their superiority in certain areas to
conventional methods. The success of NCS is due primarily to the ability, conferred by their
unique properties, to collect data, which cannot be obtained by other investigative techniques.
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48
 PRINCIPLES OF NUCLEONIC GAUGES
 A nucleonic gauge consists of a suitable source (or a number of sources) of alpha, beta, gamma,
neutron or X ray radiation arranged in a fixed geometrical relationship with one or more radiation
detectors. Most of nucleonic gauges are based on a few most common nuclear techniques.
 Natural gamma-ray technique
 NCS based on natural gamma-ray technique utilize the correlation between natural gamma-ray
intensity measured in one or more pre-selected energy windows and the concentration of
particular elements (e.g. U, Th, K) or the value of a given parameter of interest (e.g. ash in coal).
 Transmission
 In the basic configuration of a transmission gauge the media to be measured is placed between
the radioactive source and the detector so that the radiation beam can be transmitted through it
(Fig.1). The media attenuates the emitted radiation (beta particles or photons) before reaching the
sensible volume of the detector. Both source and detector can be collimated. The radiation
intensity in the detector is a function of several parameter characteristics of the material.
48

49
49
The beta source
activities usually range
from 40 MBq to
40 GBq while gamma
sources usually contain
between 0.4
and 40 GBq.

50
 Dual energy gamma-ray transmission (DUET)
 This technique is probably the most common nucleonic method for on-the-belt
determination of ash content in coal. Ash content is determined by measuring the
transmission through coal of narrow beams of low and high-energy gamma rays (Fig.
2). The absorption of the lower energy gamma rays depends on ash content, due to
its higher average atomic number than that of coal matter, and on the mass per unit
area of coal. The absorption of the higher energy gamma rays depends almost
entirely on the mass per unit area of coal in the beam. Ash content is determined by
combining measurements of the two beams. The determination is independent of
both the bed thickness and the mass of the coal. The technique is also applicable to
the analysis of complex fluid flow where multiple energy beams are usefully applied.
50

51
 Backscattering
 Whenever a radiation beam interacts with matter a fraction of it is transmitted, a
fraction absorbed and a fraction is scattered from its original path (Fig. 3). If the
scattering angle is greater than 90o some photons or particles will come back
towards the original emission point; the measurement of this radiation is the basis of
the backscattering method.
51

52
 Gamma-ray backscatter
 Measurement of radiation emitted by a stationary gamma-ray source placed in the
nucleonic gauge and back-scattered from atoms of investigated matter enables some
properties of this matter to be determined. The gamma-rays interact with atomic
electrons resulting in scattering and absorption. Some of these gamma-rays emerge
back from the investigated mater with degraded energy and intensity (count rate)
characterizing the bulk density and the average chemical composition of the matter.
 Neutron scattering (moderating)
 Fast neutrons of high energies emitted from the neutron source collide with nuclei of
investigated matter reducing their energy. In general, neutrons lose more energy on
collision with light nuclei than with heavy nuclei. Due to its light nucleus hydrogen is
most effective in moderating neutrons from the source. As hydrogen is major
constituent of most liquids detection of the liquid through container walls is possible,
as well as measurement of the moisture (hydrogen density) of soils, coke or other
materials.
52

53
53
The beta source
activities usually
range from 40 to
200 MBq while
gamma sources can
contain up to
100 GBq.

54
 Reactive Gauges
 Certain low energy gamma and X rays can ionize specific atoms, causing them to
emit fluorescent X rays of characteristic energy. The detector measurement of the
fluorescent X rays indicates not only the presence of the specific atoms but also the
amount in the material. This principle is used by gauges which analyse the
constituents of materials such as ores and alloys and by gauges that measure the
thickness of coatings on substrates of dissimilar materials.
 Electrically operated high energy neutron generators can be used to induce non-
radioactive substances to become radioactive. The radionuclides formed emit
characteristic gamma rays which can be identified by their energy. These gauges or
logging tools are used to prospect for oil.
54
The source
activities
used range
from about
200 MBq to
40 GBq.

L10 datta lecture on industrial radiation sources

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