Geiger muller counter

it covers types of counter for measurem,ent of radioactive substances also cover about radioactivity its causes effects and types of radioactive pollution

1. RADIOACTIVE POLLUTIONS & DETECTORS PRESENTED BY: ARCHIT BHARTI (ME MODULAR 2020) R.N. 201502 ARUN(ME MODULAR 2020) R.N. 201503

2. CONTENTS What is Radioactive Pollution? Types Sources Effects Detection and Measurement

3. What is radioactive pollution The ability of certain materials to emit the protons(alpha particles),electrons(beta particles) and Gamma rays by their nuclei is known as radioactivity. Radioactive pollution, like any other kind of pollution, The release of radioactive substance or high-energy particles into the environment by human activities or natural process.

4. Radioactive Contamination Radioactive contamination , also called radiological contamination , is the presence of radioactive substances on surfaces or within solids, liquids or Gases ( including The human body), where their presence is unintended or undesirable Such contamination presents a hazard because of the radioactive decay of the contaminants, which emit Harmful ionizing Radiation such as alpha or beta particles, gamma rays or neutrons .

5. Types of radiations   Non-ionizing radiations Ionizing radiations Non-ionizing radiations: Electromagnetic waves of a longer wavelength lower frequency lower energy. which are near ultraviolet rays to radio waves are known as non-ionizing radiations. These radiations have not enough amount of energy to ionize atoms or molecules .

6. Ionizing Radiations Ionizing radiations: These radiations are electromagnetic radiations that have short wavelength /high frequency and high energy like gamma rays, x-rays, These rays of energy like alpha, beta, and gamma are generated in radioactive decay have the ability to ionize molecules and atoms via which they travel. They also have ability to change molecules and atoms into charged ions. Radioactive decay is a process from which alpha, beta, and gamma radiations are generated .

7. Sources of radioactive pollutions Natural sources of radiation: Natural sources of radiation are mentioned below: In natural sources of radioactive pollution, atomic radioactive minerals are one among them. Cosmic rays possess high energy ionizing electromagnetic radiation. Another source of radioactive radiation is naturally occurring radioisotopes. Radioisotopes are found in soil/Rocks in small quantity. Radioactive elements like radium, thorium, uranium, isotopes of potassium and carbon occur in lithosphere

8. Anthropogenic sources of radiation: Human activities mentioned below include in sources of radioactive pollution: Nuclear tests Nuclear reactors Diagnostic medical applications Nuclear Wastes Nuclear explosions Nuclear metal processing

9. FALLOUT When the radioactive is spread through the atmosphere . Local fallout: Quite intense but short lived. Troposphere Fallout:It deposited in lower atmosphere at later time and cover a large area depending on mateorological condition. Stratospheric fallout:Which release extremely fine particles into the upper atmosphere,may continue for years .after an explosion and attain a worldwide distribution.

10. Effects of radioactive pollutions On Human Beings The impact of radioactive pollution on human beings can vary from mild to fatal; the magnitude of the adverse effects largely depends on the level and duration of exposure to radioactivity. Low levels of localized exposure may only have a superficial effect and cause mild skin irritation. Long-term exposure or exposure to high amounts of radiation can have far more serious health effects. Radioactive rays can cause irreparable damage to DNA molecules and can lead to a life-threatening condition.

11. Effects of Radioactive Pollution The rapidly growing/dividing cells, like those of the skin, bone marrow, are more sensitive towards radioactive emissions. On the other hand, cells that do not undergo rapid cell division, such as bone cells and nervous cells, aren't damaged so easily. Skin cancer, lu n g cancer a n d thyroi d c a n cer are some of the common types of cancers caused by radiation effect.

12. Detecting of Radiations Radiations can not be detected by sight,hearing,smelling,feeling . TYPES OF RADIATION DETECTOS Geiger counters Scintillation counters Film badges

13. Geiger Muller Counter Detection and measurement

14. What is GM Counter? It is kind of nuclear detector which is capable of detecting nuclear radiations It can be alpha beta gamma or any other nuclear particle which is capable of doing ionization

15. History The original detection principle was discovered in 1908. The development of the Geiger Muller tube in 1928 that the Geiger Muller Counter became a practical instrument. It has been very popular due to its robust sensing element and relatively low cost.

16. Old GM Counter

17. Advance version of GM Counter

18. GM Counter used for Millitary purpose

19. C onstruction of GM Counter It consist of Geiger Muller tube which is is a hollow metallic cylinder and it consists of gaseous medium. Gas medium consist of noble gas and mixture of organic compound like alcohol. Metallic cylinder is connected to negative terminal of a very high tension battery and it is acting as cathode .

20. C onstruction of GM Counter( contd ) In centre of cylinder we have metallic electrode made out of tungsten which is connected to load resistor and then connected to positive terminal of battery it act as anode Across this load resistor we have electronic setup which determines any kind of pot. Drop across resistor a counter is also associated to count this kind of events over a period of time.

21. Operating Principle When external particle cause ionization and creates positive ion and free electron due to high pot difference electron are accelerated towards centre of the tube. This electron acquire high velocity also collides with other gaseous molecule and it is capable of inducing secondary ionization. These two electrons are also accelerated towards centre also causes further ionization leads to chain reaction or avalanche effect or townsend avalanche.

22. How it works

23. How it works When radiation is present outside the detector. Some of the radiation enters the GM tube. When radiation strikes with the gas molecules in the tube it causes ionization some of the gas molecules are turned into positive ions and electrons. These ions are subjected to external electrical field. Positive ions are accelerated towards metallic surface. Electrons are accelerated towards anode and it is further capable of causing ionization .

24. How it works( contd ) These electrons also collide with gas molecule which comes in its path for inducing secondary ionization. These two electrons also accelerated and further cause ionization this process leads to chain reaction or avalanche effect which causes whole lot ionization before reaching central electrode. This kind of effect is called avalanche effect or townsend avalanche. When these electrons reaches the central electrode they are absorbed by anode . Electrons causes voltage drop across resistor which is detected by electronics and counter counts these events and if loudspeaker is connected you can hear a loud click every time particles are detected .

25. Operating Principle This is the principle on which our GM counter works Avalanche effect takes place on the entire tube.

26. Operating Principle The ionization is considerably amplified within the tube by the Townsend Discharge effect to produce an easily measured detection pulse This large pulse from the tube makes the G-M counter cheap to manufacture ,as the subsequent electronics is greatly simplified.

27. Dead Time When electron completes the circuit and meets the positive ions recombination takes place to create neutral molecule bringing back set up to orginal state. This entire process take little time during this no particle can be detected by counter. The time for which GM counter not responsive for incoming particles is called dead time It ranges from 200µs -400  

28. Quenching When electron recombine with positive ion that might emits a high energy photon it can start avalanche effect which can give false count so it needs to be restored to its orginal state through a process called quenching It is achieved by other organic compound present in tube (it absorbs the energy of photon )or by external means e.g by automatically disconnecting applied voltage source after every count .

29. Advantages Simple to build. Easily available in market. It has high sensitivity. Output pulse is high so amplification needed is very small

30. Limitation of GM Counter It can’t distinguish between two particles Output is same for different particles having different energies. Incapacity of GM counter to measure radiation during dead time

31. Application For the detection of alpha and beta particles To detect radioactive rocks and minerals in the course of mineral prospecting or as a mineral collector. To check for environmental levels of radioactivity. For police or first responders to analysis for making an intial determination of radiation risk. To check radiation level absorbed by human .

32. Scintillation Counter

33. Topics T o Cover Principle Block Diagram Scintillator Photomultiplier tube Crystal used Working Advantages & Applications

34. What is Scintillation Counter ? It is an instrument for detecting and measuring ionizing radiation by using the excitation effect of incident radiation on a scintillating material and detecting the resultant light pulses. It is invented in 1944 by Sir Samuel Curran.

35. Construction It consists of a scintillator which generates photons in response to incident radiation. A sensitive photomultiplier tube(PMT) which converts the light to an electrical signal and electronics to process the signal High tension battery Load resistor

36. Principle When high energy atomic radiations are incident on a surface coated with some fluorescent material,then flashes of light(called scintillations) are produced. The scintillations are detected with the help of a photomultiplier tube,that give rise to an equivalent electric pulse .

37. Block Diagram The S cintillation Counter has mainly three parts: (1)Scintillator (2) Photomutiplier (3) Counter Atomic Radiations Scintillator Photomultiplier Counter

38. Scintillator The scintillator is made from single crystal that should have following characteristics : High efficiency Transparent to light Stable under experimental conditions. Suitable value of refractive index .

39. Popular Types of Crystals Used as Scintillator Cesium iodide( for detection proton and alpha particles). Zinc Sulphide (for detection of alpha particles). Organic Phosphorous are used for detection of gamma rays. Xenon are used for UV radiation. Thallium activated Sodium Iodide.(The major drawback of this crystal is that it is hygroscopic in nature so it is sealed in an air tight container)for detection of gamma rays

40. Photomultiplier Tube About ten dynodes which are specially designed and properly positioned for automatic focusing of electrons(called dynodes) Each dynodes performs two functions : (1)collection of photoelectrons from previous dynode (2)emission of low energy electrons The potential of the dynodes is kept in the increasing order as we move from cathode to anode

41. Scintillation Detector

42. Working The radiations are allowed to enter the scintillator through a window. When high energy radiations strike the crystal,short duration scintillations are emitted. The photons of light emitted by the scintillator are made to strike the photo sensitive cathode of photomultiplier tube. Photoelectrons emitted from cathode are directed towards 1 st dynodes that give rise to secondary emission of electrons. The secondary electrons emitted from the surface of 1 st dynodes get accelerated toward 2 nd dynodes( at higher potential comparison to 1 st )

43. Working( contd ) This process repeats up to the last dynode and electrons get much more multiplied in number. A high energy pulse is delivered to the counting device through the anode( also called collector of PM tube). The electric pulse from the PM tube is amplified and is then delivered to the electronic counting device through a discriminator( that removes the undesired noise pulse)

44. Advantages Dead time is less compared to GM tube which means high count rate is possible. Counting efficiency is high High precision Energy of particles can be distinguished

45. Application Border security Personnel and environmental monitoring for radioactive contaminaton . Hand held radiation survey meters Nuclear plant safety. National Security

46. Research paper This paper is about radioactive waste management This paper discuss about: (1) Radioactive waste generation. (2) Classification. (3) Processing (4) Storage (5) Treatment of radioactive waste.

47. Generation of Radioactive Waste Radioactive waste is generated from number of sources (1) Nuclear fuel (2) Nuclear weapon (3) Medical waste (4) Industrial waste Nuclear weapon produces majority of waste. Medical waste contains Beta particle and Gamma ray emitters Radium,Uranium thorium decay products present in earth crust. Coal industry,fertilizers industry,building industry are few industry generally contains NORM. There are more than 440 nuclear detectors 70 new nuclear plants are under construction of electricity generation .

48. Generation(contd.) Last 4 decades entire industry has produced 71780 metric tons of used nuclear fuel. Nuclear fuel 95% Uranium 1% other heavy element such as curium,americium,Plutonium-239 each has extremely long half life. One nuclear plants generates 20metric tons of used nuclear fuel. US has 71862 tons of waste but no permanent solution to store material. Japan produces 20000 tons of spent nuclear fuel. This spent nuclear fuel is approximately 50000 times the fission product of Hiroshima bomb.

49. Generation(contd.) Most of this waste is being temporirly stored at Nuclear power plant sites & remain separated from natural environment. Scientist tested remote desert area of new mexico for waste disposal site.

50. Types of Radioactive Waste Low level waste(contaminated industrial waste). Transuranic waste( production of nuclear weapons) Uranium mill tailings from the mining of uranium ore. Spent nuclear fuel(SNF)& High level waste other highly radioactive waste. NORM(Normally occurring radioactive waste ).

51. Classification of Radioactive waste According to IAEA which publishes radioactive waste safety standards has classified waste into 6 categories: (1)Exempt waste (2)Very short lived waste (3) Very low level waste (4) Low level waste (5) Intermediate level waste (6) High level waste

52. Exempt Waste It contains radioactive materials at a level which is not considered harmful to people or surrounding environment. It consist of small concentration of radio nuclides it doesn’t require protection from radiation. Materials such as concrete, plaster, bricks metals used on nuclear power sites. Such material are not harmful don’t require disposal facility .

53. Very Short Lived Waste It has radio nuclides of very short life. This waste is harmful for short period of time. Such waste is stored until activity falls to the level of exempt waste not harmful to environment. Waste from industrial and medical applications .

54. Very Low Level Waste Waste arises from operation & decommissioning of nuclear facilities with level of activity above the levels of specified clearance of waste materials. Safety from such waste is achieved by its safe disposal in engineered surface landfill type facilities .

55. Low Level Waste It is generated from hospitals and industry which mainly has paper,tools,clothing ,needles etc. It contains mostly short lived radioactive material in very small amount. It doesn’t require shielding during handling & transport is suitable for shallow land burial. To reduce its volume its often compacted or incinerated before disposal .

56. Intermediate Level Waste Waste contains long lived radio nuclides in quantities that need more isolation from environment and generally requires shielding. Reactors metal cladding,resins chemical sludge is classified as intermediate level waste. Disposal of ILW is carried at depth of few tens to few hundreds of meter. ILW consist of 7% of volume & 4% of radioactivity world’s waste.

57. High Level Waste It produced from reprocessing of nuclear fuel. It accounts for 3% of volume but 95% of radioactivity of world’s radioactive waste. It is generated from uranium fuel & transuranic elements present in nuclear reactor core. It contains both long and short lived nuclides. There exposure has harmful effects on env . & hence disposing it safely is of utmost importance. Burying of HLW deep inside geologically sea beds is safest way for disposal .

58. References Radioactivity and Radiation by Mark Rodgers, Springer International Publishing. Atomic and Nuclear Physics by Dr.N Subhramanyam,S.Chand . Introductory Nuclear Physics by Samuel Wong PHI. https:// en.wikipedia.org/wiki/Radioactive_waste https:// www.researchgate.net/publication/275967382_A_review_of_radioactive_waste_management https:// www.researchgate.net/publication/335227283_Role_of_Geiger_Muller_Counter_in_Modern_Physics

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