1. 01/08/2018 Introduction to Radioactivity Some substances are classed as “radioactive” – this means that they are unstable and continuously give out radiation at random intervals and transformed into another isotope Radiation The nucleus is more stable after emitting some radiation – this is called “radioactive decay”. This process is NOT affected by temperature or other physical conditions.

2. 01/08/2018 Isotopes An isotope is an atom with a different number of neutrons: Each isotope has 8 protons – if it didn’t then it just wouldn’t be oxygen any more. Notice that the mass number is different. How many neutrons does each isotope have? A “radioisotope” is simply an isotope that is radioactive – e.g. carbon 14, which is used in carbon dating.

3. Naturally Occurring Radioactive Material NORM Radiation: The process of emitting energy in the form of waves or particles. All minerals and raw materials contain radionuclides of natural origin radioactive elements usually are present in very low concentrations in earth's crust and have isotopes. A large contribution of the radiation on earth is from the sun (solar) or from radioactive isotopes of the elements (terrestrial). There are three radioactive elements in nature, they are Uranium, Thorium and Potassium brought to the surface through, Magmatic activities, human activities such as oil and gas exploration or mining, and through natural processes (alterations) or like leakage of radon gas to the atmosphere or through dissolution in ground water.oil and gas explorationminingradon

4. What do we mean by Radioactivity? * An atom is unstable (radioactive) if these forces are unbalanced--if the nucleus has an excess of internal energy * Atoms found in nature are either stable or unstable Radioactive decay is the process in which an unstable atomic nucleus loses energy by emitting radiation in the form of particles or electromagnetic waves. It results in a decrease over time of the original amount of the radioactive material There are numerous types of radioactive decay. The general idea : An unstable nucleus releases energy (decay) to become more stable

5. Three Common Types of Radioactive Emissions - Penetrability * Alpha particles may be completely stopped by a sheet of paper. * Beta particles by aluminum shielding. * Gamma rays, however, can only be reduced by much more substantial obstacles, such as a very thick piece of lead or cement.

6. * Half-Life  The “half-life” (h) is the time it takes for half the atoms of a radioactive substance to decay. The decay of radioisotopes can be used to measure the material’s age.  For example, suppose we had 20,000 atoms of a radioactive substance. If the half-life is 1 hour, how many atoms of that substance would be left after: 10,000 (50%) 5,000 (25%) 2,500 (12.5%) 1 hour (one lifetime) ? 2 hours (two lifetimes) ? 3 hours (three lifetimes) ? Time #atoms remaining % of atoms remaining * Lifetime” of a particle is an alternate definition of the rate of decay, one which we prefer. It is just another way of expressing how fast the substance decays.

7. Problem: A sample of Iodine-131 had an original mass of 16g. How much will remain in 24 days if the half life is 8 days? Step 1: Half life’s = T (elapsed) / T half life = 24/8 = 3 Step 2: 16g (starting amount) 842g Half lives 123

8. The blue grid below represents a quantity of C 14. Each time you click, one half-life goes by and turns red. C 14 – blue N 14 - red As we begin notice that no time has gone by and that 100% of the material is C 14 Half lives % C 14 %N 14 Ratio of C 14 to N 14 0100%0%no ratio

9. The grid below represents a quantity of C 14. Each time you click, one half-life goes by and you see red. C 14 – blue N 14 - red Half lives % C 14 %N 14 Ratio of C 14 to N 14 0100%0%no ratio 150% 1:1 After 1 half-life (5730 years), 50% of the C 14 has decayed into N 14. The ratio of C 14 to N 14 is 1:1. There are equal amounts of the 2 elements.

10. The blue grid below represents a quantity of C 14. Each time you click, one half-life goes by and you see red. C 14 – blue N 14 - red Half lives % C 14 %N 14 Ratio of C 14 to N 14 0100%0%no ratio 150% 1:1 225%75%1:3 Now 2 half-lives have gone by for a total of 11,460 years. Half of the C 14 that was present at the end of half-life #1 has now decayed to N 14. Notice the C:N ratio. It will be useful later.

11. The blue grid below represents a quantity of C 14. Each time you click, one half-life goes by and you see red. C 14 – blue N 14 - red Half lives % C 14 %N 14 Ratio of C 14 to N 14 0100%0%no ratio 150% 1:1 225%75%1:3 312.5%87.5%1:7 After 3 half-lives (17,190 years) only 12.5% of the original C 14 remains. For each half-life period half of the material present decays. And again, notice the ratio, 1:7

12. Calculating Half-Life R (original amount) n (number of half-lifes) R. (1/2) n

13. Try it!!! Now lets try to solve a half-life calculation problem… 64 grams of Serenium-87, is left 4 grams after 20 days by radioactive decay. How long is its half life? Solution Initially, Sr is 64 grams, and after 20 days, it becomes 4 grams.The arrows represent the half-life. 64 g 64. ½ 64. ½. ½ 64.1/2.1/2.1/2 64. ½.1/2.1/2.1/2 It goes like this till it reaches 4 grams, in 20 days. n = 4 half-lifes And as we are given the information that this process happened in 20 days ; 4 half-lifes = 20 days 1 half life = 5 days

14. 01/08/2018 Ionisation Radiation is dangerous because it “ionises” atoms – in other words, it turns them into ions by “knocking off” electrons: Alpha radiation is the most ionising (basically, because it’s the biggest). Ionisation causes cells in living tissue to mutate يتحور, usually causing cancer, and causes molecules to break into bits called ions that then take part in other reactions.

15. Sources of gamma radiation we can determine the source of gamma radiation as:  Natural Source of Radiation  Artificial radio-isotopes  Background radiation

16. Natural Source of Radiation  While many naturally occurring elements have radioactive isotopes, only potassium 40 K, uranium ( 238 U and 235 U and their daughters) and thorium ( 232 Th and its daughters), have radioisotopes that produce gamma rays of sufficient energy and intensity to be measured by gamma ray spectrometry.  This is because their long half-lives, they still exist today and they are relatively abundant in the natural environment.

17. Artificial radio-isotopes  The development of nuclear energy has resulted in the creation of artificial radio-isotopes.  These are created during nuclear weapon سلاح test blasts انفجار عنيف and in research reactors for scientific and industrial uses.  137 Cs is the main gamma-emitting fall-out product from nuclear explosions and accidents. It has a single photopeak at 0.662 MeV and has a half-life of about 30 years.

18. Background radiation Radiation not originating from the earth’s surface is usually regarded as “background”, and is removed during data processing. There are three main sources of background radiation:  Atmospheric radon,  Cosmic background,  and instrument background.

19. They emit alpha and beta particles 96% as well as gamma rays 4%. Alpha and beta particles are harmful once inside the body where concentrates in the bone causes bone cancers and other bone abnormalities The hazardous elements found in NORM are Radium 226, 228 and Radon 222 (bone seekers) and also their daughter products. Each daughter has a half life time. A half- life of only 11 years, meaning that half of it decays every 11 years. Gamma rays are highly penetrating and some can pass through metals, Gamma rays, are harmful to humans with sufficient exposure.Gamma rays The degree of radioactivity is dependent on the concentration of the radioelemts and their daughters as will as the isotopes present in the mineral. Radioactivity – Is it a Health Problem? The Alpha, Beta and Gamma particles all add energy to the body’s tissues. The effect is called the Ionizing Energy. It can alter DNA. Even though Alpha particles are not very penetrative if the decaying atom is already in the body (inhalation, ingestion) they can cause trouble.

20. Absorbed Dose Depends on: Whether material is inside or outside body How long material remains in the body How much radioactive material there is The type of radiation it emits What its half-life is

21. Naturally Occurring Radioactive Material NORM There are three radioactive elements in nature, they are Uranium Thorium Potassium

22. What Is Uranium * Uranium as an element – The heaviest naturally occurring element (three main isotopes U-234, 235-0.71%, 238-99.28%) – Primary (U +4 ) (reduced-insoluble) & Secondary (U +6 ) (oxidized- soluble) *Uranium is a dense, silvery-white, slightly paramagnetic, toxic, radioactive metal. It is also ductile and malleable, lithophil and mobile Uranium is a highly reactive metal and reacts with almost of all the nonmetallic, elements and many of their compounds, uranium ignites spontaneously in air. * It dissolves in acids, but it is insoluble in alkalis * The mobility and concentration of uranium strongly dependent on the redox conditions.

23. Continue: *There are uranium minerals and uranium hosting minerals. Oxides: uraninite (crystalline UO 2-2.6 ), pitchblende (amorphous UO 2-2.6 ) Silicates: coffinite (USiO 4 ) 1-x (OH) 4x ) Phosphates: Autonite Ca(UO 2 ) 2 (PO 4 )2-10H 2 O Calcium Silicates: Uranophane Ca(UO 2 ) 2 (SiO 3 OH)2·5H 2 O Organic complexes & other forms Monazite, zircon, colombite, xenotime are the main uranium hosting minerals. * Uranium occurrence Uranium present almost everywhere, but in low concentrations. Earth crust, sea water, soil, plants and even in human body. *Granite and related rocks are the main resource and acidic volcanic is the second.

24. Why Uranium *Uranium is of great importance as a nuclear fuel. One kilogram of uranium has the capacity to produce as much energy as 1,500,000 kilograms (1,500 tonnes) of coal. The cheapest among the other energy resources (coal, oil and gas). No carbon emissions (no environmental pollution) Very limited solid waste. * Coloration Use (painting) * Isotopes production * Make weapons * Estimate the age of igneous rocks * Harden and strengthen steel * Shielding in military purposes, and for x-ray targets

25. Some important Facts *Uranium occurrence : A naturally occurring, anomalous concentration of uranium. *Uranium Deposit: A mass of naturally occurring mineral from which uranium could be exploited at present or in the future. *Uraneferous Rock: A rock contain up- normal uranium contents can form uranium deposit with natural geological processes. *Fertile Uranium Rock Unite : where the uranium can be minable.