Technetium-99m is commonly used in nuclear medicine as it emits gamma rays that can be detected externally. It has a short half-life of around 6 hours, so the radiation leaves the body quickly without accumulating. Technetium-99m is produced synthetically by bombarding molybdenum-98 with neutrons in nuclear reactors. It is used as a radioactive tracer in over 80% of nuclear medicine procedures worldwide due to its ideal properties of being a pure gamma emitter and having a short half-life.

1. By
Shireen Abdulrahman

2. Introduction
In nature there are nearly 300 nuclei, consisting of different
elements and their isotopes.
Isotopes are nuclei having the same number of protons but
different number of neutrons.
Radioactivity is the release of energy and matter that results
from changes in the nucleus of an atom.
Radioisotopes A version of a chemical element that has an
unstable nucleus and emits radiation during its decay to a stable
form.

3. Where Do Radioisotopes Come From?
Radioisotopes come from:
Nature, such as radon in the air or radium in the soil.
Nuclear reactors by bombarding atoms with high-energy
neutrons.

4. Radioisotopes radiation
Three predominant types of radiation are emitted by
radioisotopes:
1. alpha particles
2. beta particles
3. gamma rays.
 The different types of radiation have different penetration
powers.

5. Fig: penetration of radiation

6. The half-life of radioisotopes
A half-life of a radioactive material is the time it takes one-half
of the atoms of the radioisotope to decay by emitting radiation.
It can vary from a fraction of a second to millions of years.
The half-life of a radioisotope has implications about its use
and storage and disposal.

7. Fig: Isotopes half-life decay

8. Radioisotopes in Nuclear Energy
Production

9. The Basic of Nuclear Energy
 Nuclear power uses the energy created by controlled nuclear
reactions to produce electricity or uncontrolled nuclear reaction
to be used in nuclear weapons.

10. Nuclear Fission
Nuclear fission is the splitting of an atom's nucleus into parts
by capturing a neutron.
It is the most commonly used nuclear reaction for power
generation.
Nuclear fission produces heat (also called an exothermic
reaction), and electromagnetic radiation, and it produces large
amounts of energy that can be utilized for power.

11. Nuclear Fission
Fission produces neutrons which can then be captured by other
atoms to continue the reaction (chain reaction) with more
neutrons being produce at each step.
If too many neutrons are generated, the reaction can get out of
control and an explosion can occur.
To prevent this from occurring, control rods that absorb the
extra neutrons are interspersed with the fuel rods.
Uranium-235 is the most commonly used fuel for fission.

12. Fig: Nuclear fission

15. Nuclear Fusion
Nuclear fusion is another method to produce nuclear energy.
Two light elements, like tritium and deuterium, are forced to
fuse and form helium and a neutron.
This is the same reaction that fuels the sun and produces the
light and heat.
Unlike fission, fusion produces less energy, but the components
are more abundant and cheaper than uranium.

16. Fig: Nuclear fusion

17. Nuclear weapons
Nuclear weapons, like conventional bombs, are designed to
cause damage through an explosion, i.e. the release of a large
amount of energy in a short period of time.
In conventional bombs the explosion is created by a chemical
reaction, which involves the rearrangement of atoms to form
new molecules.
In nuclear weapons the explosion is created by changing the
atoms themselves - they are either split or fused to create new
atoms.

18. Fig: Nuclear warheads

19. Nuclear Materials
Nuclear materials are the key ingredients in nuclear weapons.
They include:
1. Fissile materials: which are composed of atoms that can be
split by neutrons in a self-sustaining chain-reaction to release
energy, and include plutonium-239 and uranium-235.

20. Nuclear Materials
2.Fussionable materials: In which the atoms can be fused in
order to release energy, and include deuterium and tritium.
3.Source materials: Which are used to boost nuclear weapons by
providing a source of additional atomic particles for fission.
They include tritium, polonium, beryllium, lithium-6 and
helium-3.

21. Uranium
When refined, uranium (U) is a silvery white, weakly
radioactive metal.
Uranium has an atomic number of 92 which means there are 92
protons and 92 electrons in the atomic structure.
U-238 has 146 protons in the nucleus, but the number of
neutrons can vary from 141 to 146.
It is the principle fuel for nuclear reactors, but it also used in
the manufacture of nuclear weapons.

22. Uranium Isotopes
 Natural uranium consists of three major isotopes:
1.uranium-238 (99.28% natural abundance).
2.uranium-235 (0.71%).
3.and uranium-234 (0.0054%).

23. Uranium Isotopes
 All three are radioactive, emitting alpha particles, with the
exception that all three of these isotopes have small
probabilities of undergoing spontaneous fission, rather than
alpha emission.
Table : Half-lives of Uranium Isotopes

24. Enriched uranium
Enriched uranium is a kind of uranium in which the percent
composition of uranium-235 has been increased through the
process of isotope separation.
Natural uranium is 99.284% 238U isotope, with 235U only
constituting about 0.711% of its weight.
235Uis the only isotope existing in nature (in any appreciable
amount) that is fissile with thermal neutrons.

25. Enriched uranium
Enriched uranium is a critical component for both civil nuclear
power generation and military nuclear weapons.
The 238U remaining after enrichment is known as depleted
uranium (DU), and is considerably less radioactive than even
natural uranium.

26. Uranium enrichment grades
Slightly enriched uranium (SEU)
Slightly enriched uranium (SEU) has a 235U concentration of
0.9% to 2%. This new grade is being used to replace natural
uranium (NU) fuel in some reactors
Low-enriched uranium (LEU)
Low-enriched uranium (LEU) has a lower than 20%
concentration of 235U.

27. Uranium enrichment grades
Highly enriched uranium (HEU)
 Highly enriched uranium (HEU) has a greater than 20% concentration of
235U or 233U.
 The fissile uranium in nuclear weapons usually contains 85% or more of
235U known as weapon(s)-grade.
 HEU is also used in fast neutron reactors, whose cores require about 20% or
more of fissile material, as well as in naval reactors, where it often contains
at least 50% 235U, but typically does not exceed 90%.
 Significant quantities of HEU are used in the production of medical
isotopes, for example molybdenum-99 for technetium-99m generators.

28. First nuclear weapon in history
Two major types of atomic bombs were developed by the United
States during World War II:
1. A uranium-based device (codenamed "Little Boy") whose
fissile material was highly enriched uranium.
2. A plutonium-based device (codenamed "Fat Man") whose
plutonium was derived from uranium-238.

29. First nuclear weapon in history
The uranium-based Little Boy device became the first nuclear
weapon used in war when it was detonated over the Japanese
city of Hiroshima on 6 August 1945.
Exploding with a yield equivalent to 12,500 tonnes of TNT, the
blast and thermal wave of the bomb destroyed nearly 50,000
buildings and killed approximately 75,000 people.

30. Fig: The mushroom cloud over Hiroshima after the dropping of the uranium-based atomic bomb
nicknamed 'Little Boy' (1945)

31. Uranium Nuclear Fission
A team led by Enrico Fermi in 1934 observed that bombarding
uranium with neutrons produces the emission of beta rays.
Uranium-235 was the first isotope that was found to be fissile.
Upon bombardment with slow neutrons, its uranium-235
isotope will most of the time divide into two smaller nuclei,
releasing nuclear binding energy in the form of warmth and
radiation and more neutrons.

32. Uranium Nuclear Fission
If these neutrons are absorbed by other uranium-235 nuclei, a
nuclear chain reaction occurs that may be explosive unless the
reaction is slowed by a neutron moderator, absorbing them.
As little as (7 kg) of uranium-235 can be used to make an
atomic bomb.

33. Fig: An induced nuclear fission event involving uranium-235

34. What Happens When People Are Exposed
to Radiation?
Radiation can affect the body in a number of ways, and the adverse
health effects of exposure may not be apparent for many years.
These adverse health effects can range from mild effects, such as
skin reddening, to serious effects such as cancer and death,
depending on the amount of radiation absorbed by the body (the
dose), the type of radiation, the route of exposure, and the length of
time a person was exposed.
Exposure to very large doses of radiation may cause death within a
few days or months.
Exposure to lower doses of radiation may lead to an increased risk of
developing cancer or other adverse health effects later in life.

35. Gulf War syndrome
Gulf war syndrome (GWS) or Gulf War illness (GWI) affects
veterans and civilians who were near conflicts during or
downwind of a chemical weapons depot demolition, after the
1991 Gulf War.
Approximately 250,000 of the 697,000 veterans who served in
the 1991 Gulf War are afflicted with enduring chronic multi-
symptom illness, a condition with serious consequences.
Epidemiological evidence is consistent with increased risk of
birth defects in the offspring of persons exposed to depleted
uranium.

36. Signs and symptoms
A wide range of acute and chronic symptoms have included:
fatigue
loss of muscle control
headaches
dizziness and loss of balance
memory problems
muscle and joint pain
indigestion
skin problems
immune system problems
birth defects

37. Depleted uranium exposure effect on gulf war
veterans
Depleted uranium (DU) was widely used in tank kinetic energy penetrator
and autocannon rounds for the first time in the Gulf War.
DU is a dense, weakly radioactive metal.
After military personnel began reporting unexplained health problems in the
aftermath of the Gulf War, questions were raised about the health effect of
exposure to depleted uranium.
Depleted uranium aerosol particles, if inhaled, would remain undissolved in
the lung for a great length of time and thus could be detected in urine.
Uranyl ion contamination has been found on and around depleted uranium
targets.

38. Depleted uranium exposure effect on gulf war
veterans
Several studies confirmed the presence of DU in the urine
of Gulf War veterans.
The use of DU in munitions is controversial because of
questions about potential long-term health effects.
DU has recently been recognized as a neurotoxin.
Epidemiological evidence is consistent with increased risk
of birth defects in the offspring of persons exposed to DU.

39. Radiation effects from Fukushima I
nuclear accidents
The radiation effects from the Fukushima I nuclear accidents
are the results of release of radioactive isotopes from the
Fukushima Nuclear Power Plant after the 2011 Tōhoku
earthquake and tsunami.
This occurred due to both deliberate pressure-reducing venting,
and through accidental and uncontrolled releases.
These conditions resulted in unsafe levels of radioactive
contamination in the air, in drinking water, milk and on certain
crops in the vicinity of the prefectures closest to the plant.

40. Fig: The explosion at the Fukushima nuclear plant.

41. Isotopes of possible concern
The isotope iodine-131 is easily absorbed by the thyroid.
Persons exposed to releases of I-131 from any source have a
higher risk for developing thyroid cancer or thyroid disease, or
both.
Iodine-131 has a short half-life at approximately 8 days.
Children are more vulnerable to I-131 than adults.
Increased risk for thyroid neoplasm remains elevated for at
least 40 years after exposure.

42. Isotopes of possible concern
Caesium-137 is also a particular threat because it behaves like
potassium and is taken-up by the cells throughout the body.
Cs-137 can cause acute radiation sickness, and increase the risk
for cancer because of exposure to high-energy gamma
radiation.
Internal exposure to Cs-137, through ingestion or inhalation,
allows the radioactive material to be distributed in the soft
tissues, especially muscle tissue, exposing these tissues to the
beta particles and gamma radiation and increasing cancer risk.

43. Isotopes of possible concern
Strontium-90 behaves like calcium, and tends to deposit in
bone and blood-forming tissue (bone marrow).
20–30% of ingested Sr-90 is absorbed and deposited in the
bone.
Internal exposure to Sr-90 is linked to bone cancer, cancer of
the soft tissue near the bone, and leukemia.

44. Isotopes of possible concern
Plutonium is also present in the fuel of the Unit 3 reactor and
in spent fuel rods, although there has been no indication that
plutonium has been detected outside the reactors.
Plutonium-239 is particularly long-lived and toxic with a half-
life of 24,000 years, and if it escaped in smoke from a burning
reactor and contaminated soil downwind, it would remain
hazardous for tens of thousands of years.

45. Radioisotopes in Nuclear
Medicine

46. Nuclear medicine
Nuclear medicine is a special field of medicine in which radioactive
materials are used for:
1. Conducting medical research.
2. generating diagnostic information relating to functioning of
specific organs.
3. Therapeutic treatment of ailing organs.
The radioactive materials used are generally called radionuclides or
radioactive tracers, meaning a form of an element that is radioactive
(radioisotops).
Technetium-99m is a reactor-produced radioisotop that is used in
more than 80% of nuclear medicin procedures worldwide.

47. Radionuclides
Radionuclides are powerful tools for diagnosing medical
disorders for three reasons:
1. Many chemical elements tend to concentrate in one part of
the body or another.
2. The radioactive form of an element behaves biologically in
exactly the same way that a nonradioactive form of the
element behaves.
3. Any radioactive material spontaneously decays, breaking
down into some other form with the emission of radiation.
That radiation can be detected by simple, well-known
means.

48. Important factors to consider when choosing a
radioisotope for medical use
1. It must emit gamma rays only:
Gamma rays pass through the body, which means they can be
detected with a 'gamma camera'.
Alpha particles would not be able to penetrate through the skin
so they could not be detected.
Gamma rays do not ionize cells inside the body so no damage
is caused. Alpha particles and beta particles would ionize cells,
which could lead to the formation of cancer cells.

49. Important factors to consider when choosing a
radioisotope for medical use
2. It must have a short half-life (typically around a few hours):
A short half-life ensures that all the radiation inside the
patient leaves the body quickly and does not accumulate.
3. It must be able to be easily administered to the patient.
Injections and tablets are used.

50. Technetium
Technetium is the chemical element with atomic number 43
and symbol Tc.
It is a silvery-gray radioactive metal with an appearance similar
to that of platinum.
It is commonly obtained as a gray powder.
Nearly all technetium is produced synthetically and only
minute amounts are found in nature.

51. Technetium
Its short-lived gamma ray-emitting nuclear isomer—
technetium-99m—is used in nuclear medicine for a wide
variety of diagnostic tests.
Technetium-99 is used as a gamma ray-free source of beta
particles.
Long-lived technetium isotopes produced commercially are by-
products of fission of uranium-235 in nuclear reactors and are
extracted from nuclear fuel rods.

52. Isotopes

53. Technetium-99m
 Technetium-99m is a major product of the fission of uranium-
235 (235 92U), making it the most common and most readily
available Tc isotope.

54. The technetium-99m decay chain
 A molybdemum-99 nucleus decays into a technetium-99m
nucleus by beta emission. After a period of a few hours or so
the technetium-99m emits a gamma ray and changes into
technetium-99.

55. Technetium -99m Production
Technetium below Uranium in the periodic element is actually
the only element which does not naturally occur.
Technetium -99m is produced by bombarding molybdenum
98Mo with neutrons. The resultant 99Mo decays with a half-life
of 66 hours to the metastable state of Tc .
This process permits the production of 99mTc for medical
purposes.

57. Why is technetium-99m a good tag for medical
imaging?
1. it's a pure gamma emitter .This means that it doesn't produce
more damaging alpha and beta particles and it's radioactivity
disappears after a few hours. Most substances aren't pure
gamma emitters.
2. The "short" half life of the isotope (in terms of human-activity
and metabolism) allows for scanning procedures which collect
data rapidly, but keep total patient radiation exposure low.

58. Common nuclear medicine techniques using
technetium-99m
 Bone scan
 Myocardial perfusion imaging
 Cardiac ventriculography
 Functional brain imaging
 Blood pool labeling

59. Exposure, contamination, and elimination
Radiation exposure due to diagnostic treatment involving
technetium-99m can be kept low.
Because technetium-99m has a short half-life and emits
primarily a gamma ray, its quick decay into the far-less
radioactive technetium-99 results in relatively low total
radiation dose to the patient per unit of initial activity after
administration, as compared to other radioisotopes.
In the form administered in these medical tests (usually
pertechnetate), technetium-99m and technetium-99 are
eliminated from the body within a few days.