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Radiation Safety Course

Radiation Safety Course. Dr Salim Siddiqui Radiation Safety Officer Room 301.212A Tel: 9266 7193 Curtin University of Technology. Learning Objectives On completion of this course , you should be able to demonstrate the knowledge of: 1. Sources of Radiation (Man-made and Natural)

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Radiation Safety Course

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  1. Radiation Safety Course Dr Salim Siddiqui Radiation Safety Officer Room 301.212A Tel: 9266 7193 Curtin University of Technology S.Siddiqui-Radiation Safety Notes

  2. Learning Objectives • On completion of this course, you should be able to demonstrate the knowledge of: • 1. Sources of Radiation (Man-made and Natural) • 2. Types of Radiation (Ionizing and Non Ionizing Radiation) • 3. General Characteristics of Radiation • 4. Radioactivity • 5. Quantification of Radiation (Units) • 6. Radiation Exposure Measurement • 7. ICRP Recommendations for Dose Limits (Permissible Dose) • 8. Radiation Hazards (External and Internal) • 9. Biological Effects of Radiation (Deterministic and Stochastic) • 10. International Commission on Radiological Protection. • 11. Radiation Safety Act and Regulations • 12. Role of RSO • 13. Role of EduSafe S.Siddiqui-Radiation Safety Notes

  3. 1. Sources of Radiation • Man-made sources: x-rays, radioisotopes. • Used in various industries, eg. Radiography, radiotherapy, nuclear medicine, mining etc. • (b) Natural sources: • (i) External: cosmic and terrestrial, uranium, thorium in soil, water. • (ii) Internal: Radionuclide within our body, e.g. C-14, K-40and also other radionuclides that are ingested and inhaled. • e.g. 222Rn gas. S.Siddiqui-Radiation Safety Notes

  4. 2. Types of Radiation (a) Ionizing Radiation Radiation having sufficient energy to cause ionization in matter. e.g. x-rays, gamma rays, charged particles neutrons. (NHMRC p r-34) (b) Non-ionizing Radiation Visible light, UV radiation, microwaves, laser, Infrared, Ultrasound S.Siddiqui-Radiation Safety Notes

  5. 3. General Characteristics of Radiations • Particulate Radiation: Sub-atomic particles with mass and charge. e.g. alpha, beta, protons, electrons, neutrons • EM Radiation: Electromagnetic waves with no mass and charge. e. g. X-rays, gamma rays. S.Siddiqui-Radiation Safety Notes

  6. Characteristics of Radiations Alpha particles • Generally emitted by heavy radioisotopes • It is a helium nucleus with two protons and two neutrons in the nucleus. • Typical energy range (4 – 8 MeV) • Low range (<10 cm in air, 60 μm in tissue) • Can be stopped by a sheet of paper Example S.Siddiqui-Radiation Safety Notes

  7. Beta particles • There are two types of beta decay 1. Negative beta decay • In this process a neutron in the nucleus transforms into a proton resulting in the emission of an electron and an anti-neutrino. 2. Positive beta decay • In this process a proton in the nucleus transforms into a neutron resulting in the emission of a positron and a neutrino. • Typical energy range is several keV to few MeV. Unlike alpha particle beta particle has continuous energy range. • Low range (a few mm in tissue) S.Siddiqui-Radiation Safety Notes

  8. Example of negative beta decay Example of positive beta decay S.Siddiqui-Radiation Safety Notes

  9. Gamma rays • -are electromagnet waves, that travel with the speed of light in vacuum (roughly air). • -have no charge • - are emitted from the excited nucleus following alpha or beta decay as tiny packets of energy called photons. • There are very few isotopes that are pure beta emitters and do not emit gamma rays. • e.g. H-3, C-14, P-32 S.Siddiqui-Radiation Safety Notes

  10. X-rays • are electromagnetic waves, that travel with the speed of light in vacuum (roughly air). • have no charge • x-rays are generated when fast moving electrons are decelerated in a high Z target. The emitted spectrum is continuous in energy (Bremsstrahlung spectrum). • characteristic x-rays are produced when an excited orbital electron drops back to a lower energy orbit. The difference between the two energy levels is emitted as an x-ray photon which appears as a line spectrum • x-rays are used in medical, research and other industries S.Siddiqui-Radiation Safety Notes

  11. Neutrons • These are neutral particles with no charge • There are no naturally occurring nuclei* which emit neutrons (* Except Californium-252) • Neutron sources used in industry and research are produced through nuclear reactions. • Emitted neutrons are not mono-energetic • Typically, En = 0.1 – 13 MeV S.Siddiqui-Radiation Safety Notes

  12. In general neutrons are produced by three main methods as follows: i) Nuclear reaction induced by alpha or gamma emitting isotopes ii) Nuclear reaction induced by charged particles from accelerator iii) Research reactors Example Ra - Be neutron source or Am-Be neutron source S.Siddiqui-Radiation Safety Notes

  13. Plastic Paper Lead Concrete Alpha radiation Beta radiation X and  radiation Neutron Penetrating abilities of various radiation Quiz: Which of these radiation can cause internal and external hazard? Ans. S.Siddiqui-Radiation Safety Notes

  14. No Parents remaining t 4. Radioactivity Spontaneous emission of radiation from unstable nuclei Radioactive decay law If N is the number of nuclei present and ΔN decay in time Δt, we find that S.Siddiqui-Radiation Safety Notes

  15. No No/2 No/4 No/8 2T/2 3T/2 T/2 Half-LifeTime taken for half the radioactive nuclei to decay. It varies, according to the isotope, from less than a few micro seconds to more than a billion years. S.Siddiqui-Radiation Safety Notes

  16. 5. Quantification of Radiation (Units) Activity: Determines the strength of a radioactive source.The number of disintegration occurring per unit of time is called the activity. Curie: it is the activity of that quantity of radioactive material in which 3.71010 atoms are disintegrating per second. Old unit: 1 Curie = 3.7x1010 dps SI unit: 1 Bq = 1 dps Quiz. Which source has a higher activity, 1 gram of 238U or 1 gram of 234Th? S.Siddiqui-Radiation Safety Notes

  17. 1 coulomb of charge produced in 1 kilogram of air 1 X unit of x or  radiation + + + + + + + - - - - - - - Exposure: measure of the amount of ionization produced in air by x or gamma radiation. Old unit: 1 R = 2.58 x 10-4 C/kg SI unit: 1 X unit = 1 C/kg Conversion: 1 X unit = 3881 R Roentgen: Amount of x or gamma radiation that will liberate a charge of 2.58 10-4 C in I kg of dry air at STP. Q. But how much energy is absorbed in matter? S.Siddiqui-Radiation Safety Notes

  18. 1 kilogram of any material 1 Gray of any radiation 1 Joule of energy deposited Radiation Absorbed Dose – (rad) Energy deposited by any type of radiation in any material (air, water, biological tissue etc) per unit mass. Old unit: 1 rad = 10 mJ/kg SI unit: 1 Gy = 1 J/kg Conversion: 1 Gy = 100 rad S.Siddiqui-Radiation Safety Notes

  19. Low density ionization High density ionization + + + + - - - - X-rays  particle + + + + + + + + - - - - - - - - Tissue Tissue Quiz. Which will deposit more energy in tissue, 1 rad of x-rays or 1 rad of ? Ans. Since  particles travel slower than x or  of the same energy. Therefore, it can produce more ionization within a small volume of the tissue, thus depositing more energy. S.Siddiqui-Radiation Safety Notes

  20. Quiz. Which will cause more damage to tissue? Ans. Since alpha particle deposits more energy, hence can cause more damage. So the chance of damage to tissue depends not only on the absorbed dose, but also on the: i) type and energy of radiation. ii) type of irradiated tissue S.Siddiqui-Radiation Safety Notes

  21. Type of Radiation Radiation Weighting Factor, wR x, , or  1.0  10 - 20 proton 10 neutron 5 - 20 The modified unit taking into account the type and energy of radiation is called the ‘Equivalent Dose’ Equivalent Dose = Absorbed Dose  wR Unit of equivalent dose is Sievert. (R. Sievert, Swedish radiologist) Some values of wR are given in the following table S.Siddiqui-Radiation Safety Notes

  22. However different tissues show different radiological sensitivities as shown in the table on next page: The modified unit taking into account the radiological sensitivities of radiation is called the ‘Effective Dose’ Effective Dose = Equivalent Dose  wT SI unit: Sievert Old unit = “rem” Effective Dose = Absorbed Dose  wR wT S.Siddiqui-Radiation Safety Notes

  23. S.Siddiqui-Radiation Safety Notes

  24. This unit of Effective dose is used only in radiation protection. Personal monitoring devices such as film badge are designed to record dose in Sievert. Quiz. Which will cause more damage to tissue 1 rem of x-rays or 1 rem of  ? Ans. S.Siddiqui-Radiation Safety Notes

  25. Summary Quantities and Units of Radiation S.Siddiqui-Radiation Safety Notes

  26. Summary Activity: 1 Curie = 3.7x1010 dps 1 Bq = 1 dps Exposure: 1 R = 2.58 x 10-4 C/kg 1 X unit = 1 C/kg 1 X unit = 3881 R Absorbed dose: 1 rad = 10 mJ/kg 1 Gy = 1 J/kg 1 Gy = 100 rad Equivalent Dose: Sievert = Gray  wR 1 Sv = 100 rem Effective Dose: Sievert = Gray  wR  wT S.Siddiqui-Radiation Safety Notes

  27. 6. Radiation Exposure Measurement • The standard detector is an ionization chamber • The current trough a resistor is a measure of exposure = C/kg/s = Gy/s • Personal Monitoring • - Film badges • - TLD (Thermo-luminescent dosimeter) (LiF: Mg, Ti) • - OSL* (Optically stimulated luminescence) (Al2O3: C) • - Curtin uses Luxel dosimeter (Sensitivity 0.01 mSv) S.Siddiqui-Radiation Safety Notes

  28. Personal Radiation Monitoring • Badges are issued by the RSO upon request • Badges are issued and collected quarterly • Badges are to be worn all the time when working with radiation • Badges should not be tempered or misused (Safety Regulation) • Inform your supervisor of any spills or unusual exposure to radiation S.Siddiqui-Radiation Safety Notes

  29. 7. ICRP Recommendations for Dose Limits The Effective Dose limits are as follows: • Occupational exposures: 20 mSv/year • (averaged over 5 consecutive years, and should not exceed 50 mSv in any single year) • General public: 1 mSv/year (averaged over 5 years) • Pregnancy: 1 mSv/y to the abdominal surface Note: These limits do not include, Natural background and Medical diagnosis and therapy dose S.Siddiqui-Radiation Safety Notes

  30. Equivalent Dose Limits • The eye lens:150 mSv/y • The skin: 500 mSv/y (over any 1 cm2 of skin) • The hands and feet: 500 mSv/y Note: For general public, the limits are 1/10th of the above values. S.Siddiqui-Radiation Safety Notes

  31. 8. Radiation Hazard • Two types of radiation hazard are involved when working with radioactive materials • External radiation hazard • Internal contamination hazard (i) External Hazard Associated with high activity sources that emit x, , neutron and high energy . These radiations can penetrate the body and result in a high absorbed dose. S.Siddiqui-Radiation Safety Notes

  32. STDA Rule to Reduce the External Hazard • SHIELDING: Keep suitable shielding between user and source eg. use Pb, concrete Al, perspex shielding • TIME: Minimize handling time • Dose = Dose rate x Time • DISTANCE: Maximize the distance between user and Source. • Dose rate  1/r2 • ACTIVITY: Minimize activity of the source. • Doe rate  Activity S.Siddiqui-Radiation Safety Notes

  33. In case of accident • don't touch any material • cordon off the area and place warning signs • stay at a safe distance from the accident site • don't leave the site unless you are checked of contamination • don't eat drink or smoke at the accident site • call the Radiation safety supervisor of your area or Radiation safety officer S.Siddiqui-Radiation Safety Notes

  34. ii) Internal HazardsRadionuclides emitting ,  taken internally into the human body can deposit their energy in the host tissue, thus causing damage. • Ingestion • from surface contamination. Eating drinking in workplace • Inhalation • from contaminated air, due to airborne dust, vapours • Absorption • either directly through the skin or through cuts and wounds The routes of entry into the body may be: S.Siddiqui-Radiation Safety Notes

  35. 9. Biological Effects • When radiation traverses through the tissue, following may happen: • (i) no damage to the cells • (ii) cell is damaged, but is repaired • (iii) cell survives but with permanent damage. • This is called mutation. Such cells multiply with deformity and are thought to eventuate in cancer. • (iv) cell is totally damaged. • (death of many cells causes Radiation sickness) S.Siddiqui-Radiation Safety Notes

  36. Somatic cancer in exposed person Genetic mutation in off springs 1. Stochastic at low doses radiation sickness, cataracts, skin damage etc 2. Deterministic at high doses Categories of Biological Effects S.Siddiqui-Radiation Safety Notes

  37. Categories of Biological Effects Biological effects may be divided into two categories: (i) Stochastic (ii) Deterministic (i) Stochastic effects Stochastic means chance or random effect in an exposed person. "An effect known to occur sometimes as a consequence to radiation, but which may or may not be expressed in a particular exposed person" (NHMRC, 1995, p r-36) S.Siddiqui-Radiation Safety Notes

  38. The probability of the effect is proportional to the dose, with out any dose threshold. This occur when the cell that has been irradiated is modified rather than killed. This may lead to cancer in the exposed person, or mutation in the off springs. S.Siddiqui-Radiation Safety Notes

  39. The stochastic effects are further classified as:  Somatic: When the effects appear in the exposed person. eg. cancer Genetic: When effects appear in the off springs of the exposed person, eg. mutation. This happens if the damage is incurred to the reproductive cells of the exposed person. S.Siddiqui-Radiation Safety Notes

  40. (ii) Deterministic effects Which can cause " partial loss of function of an organ or tissue (NHMRC, 1995, pr-32) These are caused when the dose is above the threshold value. The severity of the effect varies with the dose. Some of the examples are, radiation sickness, cataracts, and skin damage S.Siddiqui-Radiation Safety Notes

  41. 10. International Commission on Radiological Protection (ICRP) • ICRP was formed in 1928. It is a fully independent body, free of governments or nuclear industry constraints. • The function of the ICRP is: • (ii) set dose limits for radiation workers. • these limits are set to prevent the occurrence of deterministic effects by keeping doses below the thresholds for individual tissue and also to reduce the incidence of stochastic effects, to an acceptable level. (iii) set dose limits for general public. S.Siddiqui-Radiation Safety Notes

  42. Principles of Radiological Protection – ICRP 1977 • Justification of a practice: No practice involving exposures to radiation should be adopted unless it produces sufficient benefit to the exposed individuals or to society to offset the radiation detriment it causes. • (ii) Optimization of protection: In relation to any particular source within a practice, the magnitude of individual doses, the number of people exposed, and the likelihood of incurring exposures where these are not certain to be received should all be kept as low as reasonably achievable (ALARA Principle) economic and social factors being taken into account. • (iii) Dose limits: The exposures of individuals from the combination of all the relevant practices should be subject to dose limits, or to some control of risk in the case of potential exposures. • (ICRP Guidelines, 1991, from NHMRC 1995, p r-7) S.Siddiqui-Radiation Safety Notes

  43. National Health & Medical Research Council, NHMRC • NHMRC was formed in 1936 • The council is responsible for setting radiological protection standards in occupational, medical and public, in Australia. • NHMRC takes the recommendations of the ICRP as the basis for its own recommendations and then " implement legislation directed towards the effective control of exposure of people to radiation" (NHMRC, 1995, p r-v). S.Siddiqui-Radiation Safety Notes

  44. Radiological Council of WA • The Radiological Council of WA is appointed under the Radiation Safety Act 1975. It is a statutory body responsible for the administration of the Radiation Safety Act through the Radiation Health Section of the Health Department of WA. • Its function is: • (i) advising the minister for health on hazards of radiation • (ii) implementing and enforcing the Act • (iii) inducting inquiry into alleged contravention • (iv) suspending or cancelling licence and registration • (v) investigating and prosecuting offences under the act. S.Siddiqui-Radiation Safety Notes

  45. 11. Radiation Safety Act (1975) and Radiation Safety (General) Regulations (1983) • Under the State’s Radiation Safety Act, all premises holding x-ray equipment, radioactive substances (including radiation gauges) and prescribed electronic products ( including lasers and ultraviolet transilluminators) are registered with the Radiological Council of WA. • The registrant of the premises is responsible for the safe use of radioactive substances and the radiation generating equipments, and the safety of the users and the public as described in the Radiation Safety (General) Regulations (1983) S.Siddiqui-Radiation Safety Notes

  46. Radiation Safety Regulation • All premises involved with the radiation work are registered. • All radioactive substances, x-ray equipment and prescribed electronic products are registered. • All personnel involved in radiation work hold a valid personal radiation licence, or work under the supervision of a person holding a valid radiation licence • All personnel involved in radiation work are registered with the Radiation Safety Office. • All personnel involved in radiation work must wear personal radiation monitoring device. S.Siddiqui-Radiation Safety Notes

  47. 6. All Radiation monitoring equipment used in work place are maintained and regularly calibrated. 7. Any acquisition or use of radioactive materials must be reported to Radiation Safety Office. 8. Any project involving use of radiation or radioactive materials must obtain clearance from the Radiation Safety Office. Safety Rules for All When dealing with radiation work, each person is responsible for his/her own safety and also for the safety of people around. S.Siddiqui-Radiation Safety Notes

  48. 12. Role of the RSO • Ensures site, equipment and personnel are licensed as required by the RC. • Vetting students’ projects involving radiation • Ensure students are supervised by a licencee • Project details (candidacy) must be submitted to the RSO for approval. • Issue radiation approval number. • Issue radiation badges • Advise students to undergo radiation safety training. e.g. UWA unsealed course. S.Siddiqui-Radiation Safety Notes

  49. 13. Role of EduSafe • EduSafe is a specialist area within Curtin which provides professional advice and services in OSH, Workers’ Compensation, and Injury Management. It has overarching responsibility for OSH matters within Curtin and maintains an informative website which includes a section on Radiation Safety. • Compliance with Radiation Safety requirements is overseen by a Radiation Safety Officer (RSO), and Radiation Safety Supervisors have been appointed in the main departments or locations that use radioactive materials or devices that generate radiation. • Projects are approved by the RSO through EduSafe. • Incidents are reported to EduSafe on-line. End of Lecture S.Siddiqui-Radiation Safety Notes

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