University of Victoria Radiation Safety Refresher Course

Transcription

1 University of Victoria Radiation Safety Refresher Course Catherine Franz Radiation Safety Officer Occupational Health, Safety & Environment Telephone:

2 Overview Welcome to the online Radiation Refresher Course. The course is intended as a refresher training only. If you have not completed in-class radiation safety training you must do so prior to working with radiation. The intent of this course is to ensure that all persons handling and responsible for radioactive materials are properly trained, informed of the hazards and are familiar with the regulations and policies of possessing and handling radioactive sources. This is to ensure there is no undue risk to health, safety, security and the environment. In order to successfully complete and receive credit for the course, a score of 80% must be achieved on the quiz.

3 Course Outline I.BASIC THEORY II.TYPES OF RADIATION III.RADIATION UNITS IV.ROLES AND RESPONSIBILITIES V.RADIATION PROTECTION VI.INSTRUMENTATION VII.EMERGENCY PROCEDURES

4 I. BASIC THEORY Radiation Energy in the form of waves or particles Ionizing Radiation Radiation that can produce ions in the material it passes through by stripping electrons Non-ionizing radiation does not have sufficient energy to ionize or to break chemical bonds.

5 Non-ionizing Ionizing Radio Infrared V i s i b l e Ultra-Violet Light X-Rays Gamma Rays Cosmic Rays Electromagnetic Wavelength (nm)

6 Definitions Isotopes: atoms of the same element with the same number of protons but different number of neutrons. Nuclide: general term referring to any known isotope, whether stable or unstable, of any chemical element. Radionuclide: an unstable (radioactive) nuclide.

7 Nuclear Stability Stable nuclides have an ideal ratio of protons to neutrons If the ratio differs from the ideal, the nucleus becomes unstable and will undergo radioactive decay to achieve stability. Radioactive Decay: the spontaneous rearrangement of an unstable atom to a more stable form. The excess energy is emitted in the form of electromagnetic or particle radiation.

8 Nuclear Stability 1 H (Hydrogen): 1 proton STABLE 2 H (Deuterium): 1 proton, 1 neutron STABLE 3 H (Tritium): 1 proton, 2 neutrons 8 UNSTABLE

9 Radioactive Decay Each radionuclide decays at a specific rate per unit time which is not affected by physical or chemical processes Radioactive Half-Life (T 1/2 ): Time required for half the original number of radioactive atoms to decay into atoms of a different chemical element Effective Half-Life: Time required for any isotope in the body to be diminished by 50% as a result of radioactive decay and biological elimination

10 II. TYPES OF RADIATION ALPHA PARTICLES BETA PARTICLES GAMMA RADIATION X-RAYS

11 Alpha Particles Large charged particle identical in mass to a helium atom. Originates in the nucleus Range in air is short (few centimeters) Stopped by a piece of paper and the outer dead layer of skin. Example of alpha decay: Ra Rn

12 Beta Particles Small charged particle identical in mass to an electron. Can be either negatrons or positrons (similar to electrons but with a +ve charge) Originate in the nucleus Emit continuous spectrum of energies to a maximum value low energy beta : <250 kev (max) high energy beta : >250 kev (max) Range in air can be several meters. A thick layer of plastic is an effective shield. Example of beta decay: P S

13 Gamma Radiation Electromagnetic photons emitted from the nuclei of radioactive atoms. Very high-energy ionizing radiation. Have no mass and no electrical charge. Occurs when the nucleus of a radioactive atom has too much energy. Often follows the emission of a beta particle. Highly penetrating requires lead or concrete shielding. Causes severe damage to internal organs.

14 X-Rays X-rays are emitted when high speed electrons are slowed down or change direction due to the atoms in a target material. (Bremsstrahlung) X-rays originate in the electron fields surrounding the nucleus or are machineproduced.

15 Bremsstrahlung Radiation Braking Radiation When beta particles pass through matter, X-rays can be produced. As the beta particle approaches the nucleus, the strong attractive forces cause a rapid change in direction, producing photon energy.

16 Bremsstrahlung As the atomic number of the absorbing material increases, more secondary radiation is produced Bremsstrahlung may be more of an exposure problem than the beta particles which were originally being shielded against This is why low density material (e.g. plexiglass) is a more effective shield for beta emitters 16

17 III. RADIATION UNITS ACTIVITY

18 Activity ACTIVITY: a quantity for describing the amount of radioactivity, based on the number of transformations per unit time. Units: Becquerel (Bq) S.I. Unit is the quantity of radioactive material in which one atom is transformed per second. Therefore: 1 Bq = 1 dps (disintegration per second) Curie (Ci) conventional unit Is the quantity of radioactive material in which 3.7 x 1010 atoms disintegrate per second

19 Activity The curie is a large unit of activity. The terms millicurie (mci) or microcurie (µci) are more commonly used. The conversions between Ci and Bq are shown below: 1 Ci = 3.7 x Bq or 37 GBq 1 mci = 3.7 x 10 7 Bq or 37 MBq 1 µci = 3.7 x 10 4 Bq or 37 kbq Please note that the units cpm (counts per minute) and dpm (disintegrations per minute) are not equivalent. CPM is often used in liquid scintillation counting and portable radiation detection instruments, but must be converted to obtain the actual activity.

20 IV. ROLES AND RESPONSIBILITIES REGULATORY AND STANDARDS AGENCIES UNIVERSITY OF VICTORIA, RADIATION PROTECTION PROGRAM: STRUCTURE AND RESPONSIBILITES

21 Regulatory and Standards Agencies Canadian Nuclear Safety Commission (CNSC) WorkSafe BC Radiation Protection Services of BCCDC Radiation Protection Bureau of Canada

22 Canadian Nuclear Safety Commission (CNSC) Is an independent federal organization which regulates nuclear energy and the use of nuclear materials in Canada. Enforces compliance with the Nuclear Safety and Control Act, regulations, and any licence conditions imposed by the commission. CNSC website:

23 WorkSafe BC Occupational Health & Safety Regulation Part 7: Noise, Vibration, Radiation and Temperature Outlines: Exposure limits Requirement for an exposure control plan Requirements for protecting an unborn child Monitoring exposure requirements Requirement for radiation surveys

24 Radiation Protection Services of BCCDC Key Functions: Hazard identification and evaluation Risk assessment and communication Monitoring programs and audits Radiation health protection & harm prevention Expert advice and primary consultation Technical training; field & laboratory services Policy and legislation advocacy and support Emergency preparedness and response support BCCDC website:

25 Radiation Protection Bureau of Canada The Radiation Protection Bureau of Canada is a part of Health Canada. RPB website: RPB is a federal organization which enforces the Radiation Emitting Devices Act and provides information, conducts research and provides services in radiation protection (National Dose Registry).

26 University of Victoria Radiation Protection Program: Structure and Responsibilities

27 ADMINISTRATION R S O CNSC (Canadian Nuclear Safety Commission) UVIC Radiation Safety Committee Radioisotope Permit Holder Consolidated License Legislation, Federal Inspectors Permits Policies and Procedures UVIC Faculty Authorized User UVIC Staff, Students

28 CNSC Consolidated Radioisotope Licensing Agreement The University of Victoria has a consolidated radioisotope licensing agreement with the CNSC. Some of the activities covered in the agreement include: Maximum quantities allowed in possession Project approval Area classification and storage Bioassay and dosimetry Lab decommissioning Contamination and survey meter requirements Report requirements

29 UVic Radiation Safety Policies & Procedures The success of any Radiation Safety Program is vitally dependent on the cooperation of the individuals involved in all aspects of radioisotope use. It is therefore essential that all users be thoroughly familiar with the policies and procedures outlined in UVic s Radiation Safety Manual. The Radiation Safety Policies & Procedures manual is available online at: pdf In addition, in each lab where radiation is stored/used, a hard copy should be made available. The next few slides highlight some of the responsibilities of Permit Holders and Radiation Users.

30 Provide Adequate Facilities, Equipment and Instruments Provide designated radiation work areas Provide an annually calibrated survey meter Permit Holder Provide adequate shielding Conduct regular lab inspections

31 Personnel Management Ensure personnel are properly instructed and supervised Inform RSO, by memo, of any new users Permit Holder Ensure experiments after hours will be properly attended Laboratories are secured against unauthorized access

32 Inventory & Waste Management Maintain inventory database Follow UVic procedures for waste disposal Permit Holder Ensure proper labeling and storage of sources Do not exceed permitted possession limits

33 Working Safely Be familiar with and comply with UVic s Radiation Safety Regulations Policies and Procedures Successfully complete UVic s Radiation Safety Course Radiation User Ensure that use of sources of radiation does not endanger others Report any incident or accident

34 V. RADIATION PROTECTION BIOLOGICAL EFFECTS PRINCIPLES OF RADIATION PROTECTION CONTAMINATION CONTROL

35 Biological Effects DETERMINISTIC: Severity increases with radiation dose Examples: hair loss, skin reddening, cataract induction STOCHASTIC: Probability of occurrence increases with radiation dose Examples: cancer induction, genetic mutations

36 Radiation Damage 4 STAGES: Energy deposited in cells causing ionization of atoms Ions interact with other molecules Interactions with important organic molecules causing chemical changes Biological changes

37 Radiation Damage POTENTIAL FOR DAMAGE AFFECTED BY: Type of radioactive decay Energy of radioactive decay Half-life of the radioisotope Rate at which radioisotope is excreted from the body Radiosensitivity of the critical organ

38 Principles of Radiation Protection TIME DISTANCE SHIELDING CONTAMINATION CONTROL

39 Time The shorter the time spent working with radioactive material, the smaller the exposure Reducing the time by 1/2 will reduce the dose by 1/2 Shorter times can be achieved by pre-planning: mark out the work area and assemble all equipment ensure all equipment is working do a dry-run consult someone more experienced with the experiment

40 Distance The greater the distance between the radioactive material and the user, the smaller the radiation exposure. For gamma radiation, the intensity varies inversely with the square of the distance from the source. Doubling the distance will reduce the dose rate by a factor of 4.

41 Distance Increasing the distance can be achieved by: Working at arms length Using remote manipulations devices when working with stock solutions Returning the stock vial to storage immediately after use Avoid ordering multi-millicurie quantities

42 Shielding By choosing the correct absorber material to place between the user and the radiation source, exposure can be reduced or eliminated. Examples: Shielding composed of low molecular weight atoms for beta emitters ( 32 P) plexiglass, wood, glass, water. Shielding composed of high molecular weight atoms for gamma or x-ray emitters ( 125 I) lead.

43 Contamination Control Internal Contamination Entry of radioactive material into the body by ingestion, inhalation, absorption or injection. Laboratory Contamination The spread of radioactive material through improper experimental and housekeeping techniques.

44 Preventing Internal Contamination Ingestion: No eating or drinking in the lab Wash hands before leaving the lab Inhalation: When working with volatile radioactive material, work only in an approved fumehood (consult with RSO) Absorption: Use gloves and wear a lab coat Wait for cuts to heal before working with radioactive materials Take extra care when working with syringes or other sharps Wash hands before leaving the lab

45 Preventing Lab Contamination Prepare work area: Cover bench with absorbent liner and mark area with radiation tape Label equipment, fridges/freezers and waste containers where radioactive sources are used and stored Work in a tray if handling large volumes of liquids After completing work: Monitor area, equipment and yourself (hands, lab coat, shoes) Decontaminate if necessary Remove all wastes do not let wastes accumulate Change absorbent liner on bench if necessary

46 VI. INSTRUMENTATION DOSIMETERS SURVEY METERS LIQUID SCINTILLATION COUNTERS

47 Dosimetry People who work with radiation sources or in the vicinity of radiation sources may routinely be exposed to radiation. The amount of radiation received is called radiation dose. The measurement of such doses is known as radiation dosimetry Radiation Safety Institute of Canada

48 Radiation Doses Radiation doses fall into two categories: External radiation dose Internal radiation dose Internal radiation doses are measured using: Bioassays Specialized dosimeters External radiation doses are measured using dosimeters.

49 Dosimeters DO NOT provide protection from radiation exposure Required ONLY when there is a possibility of exceeding 1 msv per year Used for personnel monitoring, including whole body badges or extremity rings Compact, sensitive and environmentally insensitive Measures accumulated dose over a long period of time Automated system allows for dose tracking

50 Maximum Permissible Doses Person Period Effective Dose (msv) Nuclear Energy Worker (NEW) (a) One-year dosimetry period (a) Five-year dosimetry period (a) 50 (a) 100 Public (Includes all UVic radiation users) One calendar year 1

51 Survey Meters Designed to measure the rate of radiation events. Count rate (cpm) Radiation dose rate (μsv/h) Exposure rate (mr/h) Usually hand-held Battery operated Multi-purpose Detector probes available for measuring all types of radiation.

52 Survey Meters Geiger-Mueller (G-M) tube Gas-filled detector (He, Ne, Ar) Particle radiation ionizes gas molecules Not efficient for x-rays or gamma rays Suitable for 14C, 35S and 32P Solid Scintillation Detector Large crystal detector (NaI) Crystals emit light photons due to particle/wave energy Recommended for gamma and x-rays

53 Indirect Monitoring Liquid Scintillation Counters Highly sensitive detection technology Large, immobile and expensive Programmable The energy of radioactive decay is converted into visible light which is detected by the counter

54 Wipe Testing Used to detect low levels of removable contamination for both alpha and beta emitters Only effective method for detecting low energy betas ( 3 H, 14 C, 35 S) Effective in detecting contamination where room background is high

55 Wipe Test - Procedures Wipe the work bench, floor, storage areas, lab coat, equipment With gloves on, wipe an area of approx 100 cm 2 with a moistened cotton swab or filter paper Place swab into a vial and add scintillation cocktail Count samples in a LSC, including a blank Record and keep results

56 Wipe Test Results Contamination checks must be done at least weekly in areas where radionuclides are regularly used or stored If any measurements are above background, the area must be decontaminated and re-wiped Contamination monitoring records must be kept for 3 years

57 VII. EMERGENCY PROCEDURES SPILLS PERSONAL CONTAMINATION EMERGENCY CONTACTS

58 Accidents & Incidents Accident: defined as any unintended situation or event, which causes injury to personnel or property damage. Incident: defined as minor occurrences that do not cause injury or damage. The most likely type of radiation incident occurring in a laboratory is a Spill.

59 Spills Radiation spill kits and spill procedures should be available in each lab where radiation is used. In the event of a spill or personal contamination, the Radiation Safety Officer shall be notified IMMEDIATELY at

60 Emergency Contacts If further assistance is required (ambulance/fire), or assistance is required after hours use the following numbers: Campus Security local 7599 (24 hour emergency number) Emergency Services 911 or 9-911

61 Further Information Information regarding purchasing, inventory control, pregnant personnel, waste handling, transportation and packaging, and receipt of radioactive materials can all be found in UVic s Radiation Safety Policies and Procedures manual.

62 Radiation Refresher Quiz A reminder that this course is not a substitute for the inclass radiation safety training. If you are ready to take the quiz, click the link below: PROCEED TO QUIZ The quiz is a pdf document. Send your completed quiz by fax to Local 6359 or by Campus mail to: Occupational Health, Safety & Environment, Sedgewick B127.