Radiation Safety. Page 1. Introduction. Radiation is ENERGY IN TRANSIT in the form of high speed particles and electromagnetic waves.

Transcription

1 Radiation Safety Introduction Radiation is ENERGY IN TRANSIT in the form of high speed particles and electromagnetic waves. NOTE: We encounter electromagnetic ti waves every day. They make up our visible light, radio and television waves, ultra violet (UV), and microwaves with a spectrum of energies. These examples of electromagnetic waves do not cause ionizations of atoms because they do not carry enough energy to separate molecules or remove electrons from atoms. 2 Page 1

2 Introduction Ionizing radiation is radiation WITH enough energy so that during an interaction with an atom, it can remove tightly bound electrons from their orbits, causing the atom to become charged or ionized. Example is X-RAY Non-ionizing radiation is radiation WITHOUT enough energy to remove tightly bound electrons from their orbits around atoms. Example is LASER 3 Electromagnetic Spectrum 4 Page 2

3 Health Effects IONIZING DAMAGES chemical bonds NON-IONIZING Lower energy, CAN T DAMAGE bonds Alpha, Beta, Gamma, X-Ray Microwave, Infrared, Visible, Ultraviolet, Laser CUMULATIVE effects THRESHOLD effects damage from low levels damage occurs only of exposure that can addup over time no cumulative effects above a threshold level below threshold 5 Ionizing Radiation Types of Ionizing Radiation Alpha, Beta and Gamma rays from the decay of radioactive substances matter X-ray produced electronically by X-ray machines. X-ray machine emits radiation only when the machine is energised. Alpha Alpha decay is a radioactive process in which a particle with two neutrons and two protons is ejected from the nucleus of a radioactive atom. 6 Page 3

4 Ionizing Radiation Beta A beta is a high speed particle, identical to an electron, that is emitted from the nucleus of an atom. Gamma Gamma rays are electromagnetic waves or photons emitted from the nucleus (center) of an atom. 7 Ionizing Radiation X Ray X Rays are electromagnetic waves or photons not emitted from the nucleus, but normally emitted by energy changes in electrons. X-ray production OCCURS whenever electrons of high energy STRIKE a heavy metal target, like tungsten or copper. 8 Page 4

5 Penetrating Distances 9 Ionizing Radiation Dose Sievert (Sv), rem (roentgen-equivalent man) Old unit is rem where 1 Sv = 100 rem Sievert (Sv) is a unit of RADIATION DOSE due to ionizing radiation Express doses received by human beings Dose depends on ACTIVITY of radioactive source, distance, shielding and exposure time. Sievert is named after Rolf M. Sievert, a Swedish Physicist who was one of the pioneers in protection against ionizing radiation 10 Page 5

6 Effects Due To Ionizing Radiation Ionizing radiation can cause two main biological effects, namely Somatic effects (acute & chronic) in which the damage appears in the IRRADIATED PERSON HIMSELF, and Genetic effects which arise only in the OFFSPRING of the irradiated persons as a result of radiation damage to germ cells in the reproductive organs. 11 Acute Effects of Irradiation at Different Doses Dose (Sv) Effect 1,000 Spastic seizures; death in minutes. 100 Damage to central nervous system; death in hours. 10 Circulating changes; death in days. 1 Radiation sickness (nausea, vomiting, fatigue; following a short latent period epilation, loss of appetite, fever, diahorrea, rapid emaciation, and possible death); decrease in life expectancy and disease resistance; sterility, erythema reddening of the skin. 0.1 No obvious injury. 12 Page 6

7 Statistics for Chernobyl Accident Sv Casualties Deaths < Some Chronic Effects of Radiation Effect Mean Latent Period Evidence For Effect Leukemia 8-10 years Atomic bomb casualties, Medical X-ray treatmentt t Radium luminous dial Bone cancer 15 years painters Atomic bomb casualties, Thyroid cancer years Medical treatment Lung cancer years Mine workers Life shortening -- Experiments with mice Cataract 5-10 years Atomic bomb casualties 14 Page 7

8 Second Schedule - Part I Dose Limits For Radiation Workers (a) The dose from any medical or dental exposure as a patient, from the exposure to natural background radiation or from other exposures received by the radiation worker as a member of the public shall not be taken into account. Application Dose Limit per year (msv) Effective dose (whole body) 20 1 Equivalent dose in the lens of the eye the skin 2 the hands and feet (b) Where only a part or parts of the body are irradiated by external radiation, the effective dose received from external radiation shall be determined by calculating the sum W T H T over all organs and tissues irradiated, where ---- (i) H T is the equivalent dose received by any particular tissue or organ T; and (ii) W T is the weighting factor for that tissue or organ 1. The limit on effective dose (whole body) is 20 msv per year, averaged over defined periods of 5 years and with the further provision that the effective dose shall not exceed 50 msv in any single year. 2. The limit of 500 msv for skin is averaged over areas of no more than 1 cm 2 regardless of the area exposed 15 Second Schedule Part II Dose Limits For Individual Members Of The Public Application Effective dose (whole body) Equivalent dose in Dose Limit per year (msv) 1 1 the lens of the eye 15 the skin In special circumstances, a higher value of effective dose for the whole body is allowed in a single year provided that the average over 5 years does not exceed 1 msv per year. The limit shall apply to the sum of the relevant doses from the external exposure in the specified period and the committed effective dose 2. The limit of 50 msv for skin is averaged over areas of no more than 1 cm 2 regardless of the area exposed 16 Page 8

9 Control of Ionizing Radiation Exposure Whole body effective dose limit for radiation worker should not be more than 20 msv a year for whole body exposure and 1 msv a year for public members All unjustifiable doses should be avoided High dose accumulation is to be avoided for women of reproductive capacity 17 Reduction of Exposure to Ionizing Radiation Time Shielding Distance 18 Page 9

10 Reduction of Exposure to Ionizing Radiation Distance - keeping a RESPECTFUL distance from a radiation source is often the most effective way of REDUCING dose (moving from 1 m to 10 m from strong radioactive source reduce radiation dose received by 100 times). Shielding INCREASE the amount of shielding will DECREASE the amount of exposure. Time - radiation dose is directly proportional to exposure time. Keep exposure time to as SHORT as possible. 19 Control Measures Engineering Controls X-ray machine adequately shielded so that radiation level anywhere outside the enclosure when the X-ray machine is energized is within legal limit. Effective safety interlocks shall be provided so that when the X-ray machine has to be switched off before any enclosure door can be opened and cannot be switched on so long as the door is opened. Adequate warning to everyone in the vicinity i it shall be given by appropriate light or audible signals or both while X-ray machine is energized. 20 Page 10

11 Control Measures Example of Electrical Safety Lockout/Tagout (LOTO) Reproductive Health Hazard Radiation Safety 21 Operating a X-ray machine Licenses Apply for required licenses, L3 (machine), L5 (Supervision of R1 holder) and/or R1 (Radiation Worker) from National Environment Agency (NEA) Applicant must be at least 18 years old Medical Examination Before beginning radiation work. Must be certified fit for radiation work by registered medical doctor. If there is directive from NEA. 22 Page 11

12 Site Monitoring A monitoring survey is required after installation of a new X-ray machine, move a X-ray machine or modify a X- ray machine Geiger counter Scintillation counter Training All radiation worker must be adequately trained on operation of X-ray machine and know the hazards associated with the work. 23 Warning Label 24 Page 12

13 Safety Guides Follow the recommended safety guidelines from the equipment manufacturer Report any abnormal situation to immediate supervisor, Radiation Safety Officer and/or Safety Department Test interlocks at the frequency required for your particular type of X-ray machine Document and understand alignment procedures for the X-ray machine you own or use Pregnant radiation worker shall declare pregnancy to their immediate supervisor and managers so that arrangement can be made to exempt them from working X-ray machine during the pregnancy. 25 Personal Dosimeters Thermoluminescent Dosimeter (TLD) is used to measure the estimated radiation dose absorbed thru skin and body. TLD consists of TLD card and holder, also known as TLD badge. 26 Page 13

14 Personal Dosimeters TLD card provide early warning TLD card is issued bi-monthly TLD card is tested individually, data is retained forever (by NEA) After the TLD cards are processed, a dose report is generated Measures exposure in msv Identifies radiation energy, type, and direction 27 TLD Badge Do s and Don ts DO Put in TLD card properly in TLD holder with name appearing on window Wearer name should be against the wearer when TLD badge is worn Wear TLD at chest level when working around X-ray machine Keep TLD at workplace DON T Place TLD on X-ray machine Deliberately expose TLD to radiation Wear TLD during medical tests Expose TLD to heat 28 Page 14

15 Establish System for Reporting When Acquire a X-ray machine Dispose a X-ray machine Suspect an abnormal condition Move a X-ray machine Modify a X-ray machine Return a X-ray machine to service 29 Statutory Requirement Radiation Protection Act Radiation Protection (Ionizing Radiation) Licenses required for manufacture, possess, use and import, and sale of radioactive and irradiation apparatus Radiation workers must not be younger than 18 yrs old, required to register, go for medical examination, instructed to do radiation work and wear personal dosimeter. Not allowed to receive excess of annual dose limit in 2nd Schedule 30 Page 15

16 Statutory Requirement Radiation Protection (Ionizing Radiation) Regulations Medical examination include full blood examination & certified fit by approved registered doctor before engaged in radiation work Radiation worker has been adequately trained Transfer record in approved form for employees who had left the company Radioactive materials, irradiating apparatus and radiation areas must be appropriately labeled Safe storage and accounting of radiation sources Design aspects such as shielding, interlocks, warning devices, layout, instrumentation, ventilation must meet applicable requirements 31 Statutory Requirement Radiation Protection (Ionizing Radiation) Regulations Penalty for individual not exceeding $2000 Appropriate procedures in dealing with radiation accidents Calibration of area monitors and dosimeters L3 - license to keep or possess an irradiating apparatus (company) L5 -license to use irradiating at apparatus atus (individual) dua R1 - license to register as a radiation worker (individual using ionizing irradiating apparatus under supervision of licensee L5) 32 Page 16

17 Non-Ionizing Radiation Types of Non-Ionizing Radiation Electromagnetic radiation & fields with wavelengths greater than 100 nm & acoustic radiation & fields with frequencies above 16 KHz, Microwave Radiation Infrared Radiation Visible Radiation Ultraviolet Radiation Ultrasound Laser 33 Laser LASER is an acronym for Light Amplification by Stimulated Emission of Radiation LASER light differs from ordinary light in three ways, Monochromatic (single wavelength) Coherent (in-phase) Directional 34 Page 17

18 Laser Laser can pose more of a hazard than ordinary light because they can focus a lot of energy onto a small area LASERS ARE POINT SOURCES OF LIGHT LASER (POINT SOURCE) INCANDESCENT LIGHT BULB (EXTENDED SOURCE) 35 Laser Design Lasing media (gas, liquid, solid, semiconductor) Excitation mechanism (power supply, flash lamp, laser) Feedback mechanism (mirror, grating) Output coupler (partially reflecting mirror) Lasing medium Feedback mechanism Output Coupler Excitation mechanism 36 Page 18

19 Types of Laser Lasers are generally classified according to the materials used Gas (CO 2, Argon) Solid (Nd:YAG, Ti:Sa) Semiconductor (Gallium-Arsenide) Dye Mode of Operation Continuous Wave; Pulsed Wave; Q-switched Wavelength UV; Visible to Near IR; Mid to Far IR 37 Laser Hazards Beam Hazards Eye Skin Non Beam Hazards Chemical Electrical l Explosion Fire 38 Page 19

20 Laser Hazards Eye Hazards Risk for retinal injury is dependent on wavelength and/or total power entering the eye For wavelengths that focus on the retina, the optical gain of the eye is about 100,000 times! If the irradiance entering the eye is 1mW/cm 2, then the irradiance at the retina will be 100 W/cm 2 39 Laser Hazards Skin Hazard Skin injury from laser energy is primarily THERMAL (except for UV). Highly dependent d on: Beam Irradiance Exposure Duration 40 Page 20

21 Laser Hazards Non-beam Hazards Chemical Hazards - from dyes; from solvents used to clean optics Electrical Hazards from high voltage power supplies Explosion Hazards from high pressure arc lamps, from compressed gases Fire Hazards from electrical circuit, ignition of gases, flammable solvents BOOM 41 Laser Classification Class Description 1 Lasers that are inherently safe & incapable of producing dangerous levels of emissions 2 Do not normally present a hazard because of normal human bright-light aversion response. May present potential eye hazard if viewed directly for long time, 3a 3b Would not injure the eye if viewed for only momentary periods with the unaided eye, Eye damage possible if viewed with collection optics Hazardous under direct viewing or a reflected beam is viewed. 4 Hazardous under all viewing conditions, may produce significant skin hazards as well as fire hazards. 42 Page 21

22 Engineering Controls Protective housing that prevents human access during operation to laser Enclosed beam path Safety Interlocks Remote control firing Key actuated master control Beam stops and attenuators 43 Control Measures Example of Electrical Safety Lockout/Tagout t (LOTO) Radiation Safety 44 Page 22

23 Licenses Apply for required licenses, N2 (machine) and/or N3 (laser worker) from National Environment Agency Applicant must be at least 18 years old Medical Examination Before beginning laser work. Must be certified fit for laser work by registered medical doctor. Training All radiation worker must be adequately trained on operation of X-ray machine and know the hazards associated with the work. 45 Protective Eyewear Appropriate for all wavelengths in use Sufficient attenuation (Optical Density) at wavelengths in use Good visible light transmission Good field of viewing Comfortable to wear 46 Page 23

24 Warning Label LASER RADIATION DO NOT STARE INTO BEAM OR VIEW TYPE OF LASER POWER & WAVELENGTH CLASS 2 LASER PRODUCT Class 2 Laser Product LASER RADIATION DO NOT STARE INTO BEAM OR VIEW DIRECTLY WITH OPTICAL INSTRUMENTS TYPE OF LASER POWER & WAVELENGTH CLASS 3A LASER PRODUCT Class 3a Laser Product 47 Warning Label LASER RADIATION AVOID EXPOSURE TO BEAM TYPE OF LASER POWER & WAVELENGTH CLASS 3b LASER PRODUCT Class 3b Laser Product LASER RADIATION AVOID EYE OR SKIN EXPOSURE TO DIRECT OR SCATTERED RADIATION TYPE OF LASER POWER & WAVELENGTH CLASS 4 LASER PRODUCT Class 4 Laser Product 48 Page 24

25 Safety Guides Do not attempt to operate systems with enclosures open Do not defeat or tamper with safety interlocks Do not operate machine if enclosures are damaged Follow the recommended laser safety guidelines of the equipment manufacturer as in the user/service manual 49 For Repair Work Control access to the equipment during service e.g. Laser curtains, barriers, closing entranceways Post NOTICE sign at entranceway into controlled area After maintenance or servicing, Remove NOTICE sign Remove unnecessary objects from the vicinity of the laser Checked to confirm all safety interlocks are operating effectively NOTICE LASER REPAIR IN PROGRESS Laser Safety Eyewear Required 50 Page 25

26 Laser should be discharged in a non-reflective & fire resistant background Area should be cleared of personnel for a reasonable distance on all sides of laser beam Looking into the primary laser beam, specular reflections of the beam, including those from lens surface, should be avoided at all times Avoid aiming laser into eye to prevent looking along the axis of the beam which increases the hazard from reflections 51 Laser work should be carried out in areas of high general illuminations to keep pupils constricted thus limiting the energy which might inadvertently enter the eyes Personnel should be instructed on potential eye hazards & the importance of limiting unnecessary exposure Safety eyewear designed to filter off specific frequencies & to provide protection should be worn at all times. Binoculars or aiming telescopes should not be used to view direct laser beam or reflected beam from mirrors unless the beam intensities are greatly below safety levels. 52 Page 26

27 Statutory Requirement Radiation Protection Act The Radiation Protection (Non-Ionizing Radiation) Regulations Apply to the following non-ionizing i i apparatus: a) ultraviolet sunlamps (for irradiating living human body) ; b) microwave ovens ; c) medical and industrial ultrasound apparatus; d) magnetic resonance imaging (MRI) apparatus; e) entertainment lasers; and f) high power lasers N2 - license to keep or possess for use of class 3b & 4 lasers & ultrasound N3 - license to use class 3b & 4 lasers 53 Statutory Requirement The Radiation Protection (Non-Ionizing Radiation) Regulations Detail requirements in dealing with NIR Requirements on shielding, interlocks, warning devices Appropriately labeled to give adequate warning Worker must be at least 18 yrs old to perform laser radiation work, adequately trained & holds a license for class 3b or 4 lasers 54 Page 27

28 Thank You Page 28