Physics SPM Form 5 Chapter : Radioactivity

1. RADIOACTIVITY
BY :
AIN NADHIRAH BINTI MAZDI
FAIZAL
MUHAMMAD NURARIF BIN
SULEIMAN
MUHAMMAD ARIQ BIN ISMAIL
5 AL-BIRUNI

2. INTRODUCTIONIN 1896, BEQUEREL, A FRENCH PHYSICIST DISCOVERED THAT CRYSTALS OF
URANIUM SALTS EMITTED PENETRATING RAYS SIMILAR TO X-RAYS WHICH
COULD FOG PHOTOGRAPHIC PLATES. TWO YEARS AFTER THIS PIERRE
AND MARIE CURRIE DISCOVERED OTHER ELEMENTS: POLONIUM AND RADIUM
WHICH HAD THIS PROPERTY. THE EMISSION WAS KNOWN AS RADIOACTIVITY.
The Stability of Nuclei
Protons and Netrons are held together in the nucleus of an atom by the strong-force.
This force acts over a very short distance of about ~1 fm, (10-15m) and over this short
distance it can overcome the electromagnetic repulsion between the positively
charged protons. Nuclei with radii that are within the range of the Strong force are
stable. As atomic number increases the radius of the nucleus also increases and the
element becomes unstable. This instablity manifests itself as the emission of particles
or energy from the nucleus. The elements with atomic number greater than 82 are
radioactive.
Radioactivity is the spontaneous and
randomemission of radioactive rays from
unstable radioactive materials to become more
stable material.

3. PROPERTIES OF
RADIOISOTOPES
• EMITS RADIOACTIVE RADIATION.
• RADIOACTIVE RADIATIONS CAN KILL CELLS.
• RADIOACTIVE RADIATIONS HAVE DIFFERENT PENETRATINGABILITY WITH MATERIALS OF
DIFFERENT THICKNESS AND DENSITIES.
• RADIOACTIVE RADIATIONS CAN CAUSE CELL MUTATION.
• RADIOACTIVE RADIATIONS CAN IONISE MOLECULES.
• ITS ACTIVITY DECREASES WITH TIME.
• RADIOISOTOPES HAVE THE SAME CHEMICAL PROPERTIES AS NON-RADIOACTIVE ISOTOPES
OF THE SAME ELEMENT.

4. APPLICATIONS OF
RADIOISOTOPES

5. To diagnose of thyroid disease using iodine-123
To treat an overactive thyroid gland and
certain kinds of thyroid cancer by using
sodium iodide labelled with radioactive iodine
To detect position of blood clots
or thrombosis using Sodium-24
injected in the bloodstream

6. To detect and treat brain tumor using
phosphorus-32
To study the circulation of iron in the
blood using iron-59
To sterilise medical equipments
and to destroy cancer cells in
radiotherapy radioisotope cobalt-
60 is used

7. Pests can be killed using radioactive
rays esp using gamma rays
To stop pests from reproducing, induced mutation by using
gamma rays can be employed. But this has the probability of
producing GMO and resistant pests

8. To be used as tracers in the
effectiveness of fertilisers using nitrogen-
15 and phosphorus -32
To induce genetic mutation in a
plant in order to produce a better
strain which has higher resistance
against pest and diseases

9. C-14 is another radioactive isotope that decays to C-12. This isotope is found in all
living organisms. Once an organism dies, the C-14 begins to decay. The half-life of
C-14, however, is only 5,730 years. Because of its short half-life, the number of C-
14 isotopes in a sample is negligible after about 50,000 years, making it impossible
to use for dating older samples. C-14 is used often in dating artifacts from humans.
For determining age of fossils older than 60,000 years one
uses a potassium-argon dating technique. Potassium dating
has a half life of 1.3 billion years, thus allowing the age of rocks
several billions years old to be determined. A more accurate
"argon-argon" dating technique (determining the ratio between
argon-39 and argon-40) has also been developed.

10. To measure geological time.
During the formation of rocks, some radioisotopes such as uranium-238 are
trapped. As the decay continues, the proportion of uranium-238 decreases slowly
resulting in the equally slow growth of its product lead-206. An estimate of the age
of the rock can be inferred from the relative proportions of lead and uranium in the
rock.

11. 1. The thickness of paper, plastics, clothes and metal sheets need to be
standardised and this is done by placing a raioactive source at one side of
the material and a detector on the other side.
2. For sheets of metal, gamma ray is used. For plastics, clothes and paper,
beta particles are used.
3. The detector will register a higher count if the material is too thin and
lower register if too thick. The computer will make adjustments according to
the thickness of the material.

12. This mechanism is also used to
ensure that containers such as
cans and food packages are
filled to the specified amount.
Radioisotope is added to
engine oil so that its level of
wear and tear can be
determined.
In order to kill germs that cause
food to spoil quickly, gamma rays
are used.
If exposed to gamma
ray, latex becomes
harder without the need
for adding sulphur.

14. Nuclear Fission
-most commonly used form of NP
-U235 is a special Isotope of the normal
(inactive) U231
-Neutron collides with atom of U235
-atom splits into Krypton and Barium plus ENERGY
235U + 1 neutron →→ 2 neutrons + 92Kr + 142Ba + ENERGY
-fission of one U235 atom yields
Seven million times the energy of Exploding one TNT molecule
-control rods absorb neutrons
-controlling the reaction
-Supercritical reaction- resulting # neutrons > 1
-the reaction builds up

15. Supercritical Reaction
Additional Neutrons create a chain reaction, which is controlled by the
control rods .
Control Rods

16. Breeder Reactors
-The Breeder Reaction produces fissionable (weapons
grade) Plutonium239 from unfissionable U238
-U239 becomes Neptunium
-Neptunium becomes Plutonium239 that is available
for fission with Exposure to neutron
-BR- also fission reaction, but using different fuel.
Instead of fissioning U235, BR manipulates U238 into
Pu239

17. How is nuclear fission turned
into electrical energy?
• Powered by fission (primarily uranium-235)
• Fission heats water to steam
• Steam spins turbine, using dynamo effect to generate
electricity
• Steam circulated through cooling container; waste
water from cooling container exhausted into rivers
A little more detail…
• Fission rate controlled by (control) rods called moderators or nuclear poisons
• Moderators absorb or slow neutrons and thus mediate reaction
• Moderators can be used to stop all fission, if necessary (replace fuel or in case of danger)
• Some reactors use either a liquid metal (sodium, potassium) or gas (carbon dioxide,
helium) as heat exchange element.

18. DIAGRAM OF NUCLEAR PLANT

19. PROS AND CONS OF USING NUCLEAR
FISSION TO GENERATE ELECTRICITY
Pros:
•Environmentally, nuclear power has very little impact:
*does not depend on fossil fuels→ the carbon dioxide emission is minimal.
*Coal and natural gas power plants emit large amounts of carbon dioxide into the
atmosphere which contributes to ozone problems, acid rain, and global warming.
• Relatively inexpensive:
*Uranium is less expensive than oil, natural gas, or coal.
*Leads to lower energy cost for the consumer
•Because it does not depend on fossil fuels, fluctuations in oil and gas prices do not
affect its supply.
•Reliability:
*Nuclear power plants produce large amount of power on a consistent basis

20. Cons:
• Waste:
*Each nuclear power plant generates, on average, 20 metric tons of high-level radioactive waste which takes tens
of thousands of years to decay to safe radioactive levels. Plants also produce low
level radioactive waste which still takes thousands of years to decay.
• Costs:
*Expensive to store, monitor, and guard the large amounts of waste so that it doesn’t fall into the wrong hands, as
waste may be used in the production of nuclear weapons.
•The more power plants that are built, the higher the probability that some sort of breakdown in security would
occur somewhere in the world.
•Nuclear power is not a renewable energy resource. The energy source of nuclear power is Uranium, which is
scarce, as its supply is estimated to only last for the next 30-60 years depending on demand.

21. NEGATIVE EFFECTS OF
RADIOACTIVE SUBSTANCES
Radioactive substances emit radiations that are harmful to
living things. This is due to the ionisation and penetrating
properties of these radiations.
As the radiations pass through living cells, they ionise the
neighbouring atoms or molecules. The reactive ions that are
produced will
i. Interfere with the chemical processes in the cell.
ii. Induce mutations in the genetic structure of the cell.
At the same time, the radiations might kill the cell in body
tissues. If there are far too many cells that were destroyed, the
organism may die.

22. The amount of damage inflicted to humans depends on the types of radiation, dosage and exposure period, methods of insertion into the
body and location of exposure.
i. Types of radiation - Alpha particles outside the body are harmless because they can be stopped by the human skin.
ii. Dosage and exposure - Exposure to high dosage of radiation in a short period of time results in immediate symptoms such as vomitting,
increase in body temperature, blood composition change and many more.
iii. Methods of insertion into the body - The internal part of human body can be damaged by alpha particle that were ingested through food or
inhaled through air, this is due to the high ionising effect of Alpha particles.
iv. Cells that are actively dividing are more vulnerable to radiations. Skin cells in general can withstand higher dosage of radiation compared to
the other internal organ.

23. The harmful effects of radiation on humans can be divided into two categories which can be categorised as Somatic
effect or Genetic effect.
i. Somatic effect: includes damage to all parts of the body except the reproductive
organs. Symptoms include: fatigue, vomiting, hair loss, infertility in male, severe
skin burn and leukemia or cataracts (which may arise after a long period of time).
ii. Genetic effect: includes damage to
reproductive cells. Genetic defect can be passed
down to the next generations. Examples of
genetic defects include Down Syndrome,
Klinefelter Syndrome, Turner Syndrome.

24. PRECAUTIONARY STEPS IN HANDLING
RADIOACTIVE SUBSTANCES
• Experiments that involves radioactive substances are conducted in a room surrounded by
concrete walls.
• Strong radioactive substances are handled using remote-controlled mechanical arms from
a safe distance.
• Weak radioactive substances could be handled by using tweezers.
• Radioactive wastes must be disposed off by using suitable and safe methods. Rooms,
buildings, containers and radioactive storage places must be labelled with the sign for
radioactive substance. Radioactive substances are contained in thick lead containers.
• Protective suits and gears such as gloves and eye glasses made of lead are used at all
times when handling radioactive substances. These shields protect the workers from
harmful radiations.
• Workers handling radioactive substances must wear special badges which detect the
amount of radiation they are exposed to. Food and drinks are not allowed in places where
radioactive substances are handled.
tweezers
thick lead containers
Protective suits

25. PROPER MANAGEMENT OF
RADIOACTIVE WASTE
Low level radioactive wastes
Sources: Hospitals, nuclear power stations, industries, research laboratories.
Examples: Contaminated equipments, shoes, biohazard suit, clothing,
wrappers, air filters, gloves, etc.
Half-life: 10-50 years
Radioactivity level: low
Management: Solid wastes are stored
Intermediate level radioactive wastes
Sources: Nuclear power stations, industries, research laboratories
Examples: Component in nuclear reactors, chemical sediments
Half life: long
Radioactivity level: High
Management: Radioactive wastes are placed in concrete block and then buried underground

26. High level radioactive wastes
Sources: Nuclear power stations
Examples: Fuel rods used in nuclear power stations
Half life: 100 000 years or more
Radioactivity level: High
Management: Fuel rods are submerged in a pool of water to cool them down. The
rods are then stored in a steel container which are buried underground at a depth of
between 500m and 600m, dispose in ocean or mountain carvens
Deep Ocean Disposal
• The waste is placed in
borosilicate glass
containers
• These containers are
made to be unbreakable –
dumped into the deepest
and darkest places on
earth
Deep Geological Burial
• Waste is buried in caverns
• Away from water sources (under and above ground)
• Far from people or other living organisms
• Dry climate- not prone to harsh weather
conditions
• Yucca Mountain, Nevada

27. VIDEO OF
APPLICATIONSSodium-24 - A Radioisotope Hero in Industry
Radioisotopes in Medicine