🗊Презентация Radiation safety training

Radiation Safety Training Radiation Safety Training

Basic Radiation Theory and Fundamentals Basic Radiation Theory and Fundamentals Sources of Ionizing Radiation Biological Effects and Risks of Exposure to Ionizing Radiation Radiation Protection Standards Controlling Radiation Dose Radiation Monitoring Responsibilities for Radiation Protection Emergency Response Radiation Safety Training Exam

Nucleus: Contains Protons (+1 charge) and Neutrons (no charge) Nuclear Diameter ~ 10-15 m Electrons: orbit the nucleus (-1 charge) Atomic Diameter ~ 10-10 m More than 99.9% of the atomic mass and all the positive charge are in the nucleus ! Atomic vs. Nuclear Dimensions !

Ionizing versus Non-Ionizing Radiation Ionizing versus Non-Ionizing Radiation

Absorbed The rad (radiation absorbed dose) is the energy deposited per unit mass by Dose ionizing radiation in a material. One rad equals 100 ergs per gram. The SI unit of absorbed dose is the Gray. 1 Gy = 1 Joule/kg = 100 rad Dose Takes into account the biological effectiveness, or quality, of different types of Equivalent radiation. Dose Equivalent, measured in rems or Sieverts, is equal to the absorbed dose times a quality factor (Q). Equivalent Takes into account the different probability of effects that occur with the same Dose absorbed dose delivered by radiations with different weighting factors (WR). The SI unit of Equivalent dose is the Sievert. 1 Sv = 100 rem Exposure The unit of radiation exposure in air is the Roentgen (R). It is defined as that quantity of x-rays causing ionization in air equal to 2.58 x 10-4 coulombs per kilogram (C/kg). Air Kerma Kinetic Energy Released per unit Mass of a small volume of air when it is irradiated by an x-ray beam. Kerma is measured in Gy.

Radioactivity: The spontaneous decomposition or disintegration of unstable atomic nuclei is termed radioactivity. The energy and particles which are emitted during the decomposition /decay process are called radiation. Units of Measure: Becquerel (1 disintegration per second) Curie (3.7 x 1010 decays per second) Contamination: Simply put, contamination is radioactivity where it is not wanted or controlled. Units of Measure: Becquerels per liter (Bq/L) - if gas or liquid Bq/cm2 or µCi/m2 - if on a surface Atomic Number (Z): Number of protons in the nucleus. Mass Number (A): Number of neutrons and protons in the nucleus. Isotopes: Chemical elements with the same Z number .

Photodisintegration X-Ray disappears => liberates a proton, neutron or alpha particle Photoelectric Effect X-Ray disappears => liberates an atomic electron

Compton Scatter X-Ray survives => liberates an electron while changing course and losing some energy Pair Production X-Ray disappears => creates an electron / positron pair

Common Sources of Ionizing Radiation Common Sources of Ionizing Radiation Sources of Background Radiation Exposure Natural Background Medical Diagnosis and Treatment Manufactured/Industrial Sources Sources of Occupational Radiation Exposure Radiation Hazards in the Workplace

Biological Response to Ionizing Radiation – Key Terms Biological Response to Ionizing Radiation – Key Terms Somatic, Stochastic, Deterministic, Heritable Radiation Biology – Mechanisms & Effects Factors Affecting Biological Response Total Dose, Dose Rate, Radiation Type & Energy Area of the Body Irradiated, Cell Sensitivity, Individual Sensitivity Radiation Risks Quantifying Risks The acceptability of Risks

Radiation Biology – Key Terms Somatic Effects: biological effects that occur on the exposed individual Deterministic Effects: definite threshold; the severity of effect increases with dose (Examples: cataracts; erythema; infertility) Stochastic Effects: probabilistic in nature; existence of a threshold not clear; probability of occurrence increases with dose (Examples: cancer – DNA is the target of concern) Heritable Effects: a physical mutation or trait that is passed on to offspring; these have never been observed in humans but are believed to be possible.

Radiation Causes Ionizations of: ATOMS which may affect MOLECULES which may affect CELLS which may affect TISSUES which may affect ORGANS which may affect THE WHOLE BODY

Radiation Biology – Mechanisms DNA is the Target of Concern (Deoxyribonucleic acid [DNA] encodes the genetic instructions used in the development and functioning of all known living organisms) Direct and Indirect Effects DNA strand breaks (Direct Effect) Water molecule dislocation (Indirect Effect) Reactive species formation (Indirect Effect) Radiation Causes Ionization and Excitation in Water (H+ OH- H20+ H20- H20* e- H202)

Radiation Biology – Affects What can Happen after Direct or Indirect DNA Damage? Detection and Repair Cell Death DNA Changes With No Negative Effects DNA Changes With Deleterious Effects

Radiation Biology – Factors Affecting Biological Response Total Dose Received & Dose Rate Greater total dose and dose rates generally equate to more damage Type and Energy of Radiation Alpha particles are more damaging than X-Rays Higher energy = greater effect Area of Body Irradiated Effects increase with area irradiated Cell Sensitivity Rapidly dividing cells and cells that have a long dividing future tend to be more sensitive Individual Sensitivity Each person responds differently

Acute versus Chronic Exposures Chronic radiation exposures: low doses over long time periods Acute radiation exposures: high doses over short time periods The following effects are associated with acute, whole body exposures:

Radiation Risk Radiation Exposure Is Assumed to Increase Cancer Risk Approximately 35 – 45% of all people will develop cancer in their lifetime – aside from radiation exposure. Approximately 20% of all people will develop a fatal cancer in their lifetime – aside from radiation exposure. If 10,000 people all received 1,000 mrem, (1 rem), (10 mSv) of radiation exposure, we would expect 5 or 6 to die from radiation related cancer and 2,000 to die from all other cancer sources. Risk of developing a fatal cancer from radiation exposure: 5.5 x 10-4 per rem or 5.5 x 10-2 per Sv

The Principles of Radiological Protection The Principles of Radiological Protection Epidemiological Studies Dose Response Models National / International Recommendations & Laws Occupational Limits Facility Control Levels Protection of the Embryo/Fetus Protection of the General Public (100 mrem; 1 mSv)

Justification – No practice shall be adopted unless its introduction produces a net positive benefit. This is a societal decision. Optimization – All exposures shall be kept ALARA, economic and social factors being taken into account. Limitation – Individual exposures shall not exceed the limits.

Epidemiology – the study of patterns, causes, and effects of health and disease conditions in defined populations. Epidemiology – the study of patterns, causes, and effects of health and disease conditions in defined populations. UNSCEAR - United Nations Scientific Committee on the Effects of Atomic Radiation Sources of Human Population Radiation Epidemiological Data Atomic Bomb Survivors Radiotherapy Patients Occupational Radium Dial Painters, Miners (Radon Exposure), Radiologists, Nuclear Workers Environment Chernobyl Accident, Weapons Test Fallout, Natural Background

Epidemiological studies are performed and presented Epidemiological studies are performed and presented UNSCEAR World Health Organization National and International agencies make recommendations International Atomic Energy Agency (IAEA) International Commission on Radiological Protection (ICRP) National Council on Radiological Protection and Measurements (NCRP) Country, State and Local Laws Exposure Limits and Guidance Documents

Unrestricted Area – Any area that is not controlled for the purposes of radiation safety (offices, break rooms, meeting rooms, non-production, non-test areas) Unrestricted Area – Any area that is not controlled for the purposes of radiation safety (offices, break rooms, meeting rooms, non-production, non-test areas) Controlled Areas – Access is controlled for radiation protection purposes (includes areas adjacent to mega voltage enclosures) Restricted Areas – Access is prevented or limited for the purpose of protecting individuals from undue risks from radiation exposure (includes inside test cells / bunkers when radiation is being generated

The developing embryo/fetus, with rapidly dividing cells, is sensitive to many environmental factors including ionizing radiation. The developing embryo/fetus, with rapidly dividing cells, is sensitive to many environmental factors including ionizing radiation. The embryo/fetus is most susceptible to developing adverse health effects if exposed during the time period 8-15 weeks after conception. Declaration of Pregnancy Additional safety precautions are available to declared pregnant workers The declaration must be submitted (in writing) to the RSO Detailed training material and information will be made available A historical dose assessment and job analysis will be performed Temporary changes to job duties will be considered A fetal dosimeter will be issued

Member of the Public: means an individual who is not a radiation worker, has not received radiation safety training and who is not monitored for occupational exposure Member of the Public: means an individual who is not a radiation worker, has not received radiation safety training and who is not monitored for occupational exposure The strict exposure limit to a member of the public is: 100 mrem/yr (1 mSv/yr) Members of the public are not allowed unescorted access to test cell or bunker areas.

Radiation Protection Policies and Procedures The ALARA Concept (Time, Distance and Shielding) Signs, Labels, and Postings Access Controls

ALARA is an acronym for As Low As Reasonably Achievable. Since it is assumed that any radiation exposure involves some risk, doses shall be maintained as far below the regulatory limits as is practical. To keep doses ALARA, the three most commonly used techniques are: time, distance and shielding. Time – whenever practical, minimize the time spent near sources of radiation and minimize the output from RGMs. Distance – to the extent practical, maximize the distance between personnel and radiation sources. Shielding – incorporate attenuating barriers between radiation sources and personnel whenever practical.

Some areas require specific authorization or an escort prior to entry. Be aware of and adhere to the following Hazard Communication: symbols, signs and other warnings located within and near restricted or controlled areas.

Operators must physically enter the test cell, bunker or shielded enclosure to ensure no persons are within the enclosure and it is safe in all respects to generate radiation. Operators must physically enter the test cell, bunker or shielded enclosure to ensure no persons are within the enclosure and it is safe in all respects to generate radiation. Once the test cell is cleared and the door closed, access must be continually monitored, otherwise the cell must be re-cleared prior to the next Beam-On. Personnel who need access to an enclosure must get permission from the operator prior to entry. It is absolutely forbidden to generate radiation while persons are within an Accuray shielded enclosure. It is prohibited to enter a cell in which a radiation device is in use.

Personnel Monitoring Personnel Monitoring Facility Monitoring Radiation Detectors

Dosimetry Use is a Requirement for all Radiation Workers Dosimetry Use is a Requirement for all Radiation Workers Basic Dosimetry Use Guidelines Include: Keep away from non-occupational radiation sources such as: Airport checked luggage scans Medical and dental imaging Prevent the dosimeter from receiving excessive exposure to heat, sunlight or moisture Promptly exchange at regular intervals (usually every three months) Notify radiation safety personnel when a dosimeter is lost, damaged or accidentally exposed

Test Cell/Bunker Commissioning and Routine Leakage Surveys Test Cell/Bunker Commissioning and Routine Leakage Surveys

Radiation Leakage Surveys and Area Monitoring Radiation Leakage Surveys and Area Monitoring Gas Filled Detectors –Ionization Chambers Benefits – rugged, inexpensive, appropriate for Accuray environment except primary beam measurements Potential Problems - recombination, dead time, pile up, RF & magnetic field interference

Briefly inspect the instrument for physical damage or excessive wear. Briefly inspect the instrument for physical damage or excessive wear. Ensure the instrument has been recently calibrated. Power on the instrument and perform a battery check. Note the natural background radiation level and fluctuations in instrument response. Always lead with the detector, maximizing your distance from radiation sources. Think ALARA and caution is warranted as exposure rates approach or exceed: 10 mR/hr; 100 µSv/hr

Management Responsibilities Management Responsibilities Promote a positive radiation safety culture and ensure adequate resources exist to develop/maintain a robust radiation safety program Radiation Safety Organization Responsibilities Ensure protection of persons, the environment and property Ensure regulatory compliance and advise on technical issues Individuals’ Responsibilities Adhere to all radiation worker requirements, postings, and controls Demonstrate responsibility and accountability through an informed, disciplined and cautious attitude toward radiation Individuals’ Rights Stay informed of all risks and associated controls prior to performing radiation work duties Have access to personal dose records

Limit the radiation dose to involved persons … the first action during any emergency is to turn off the machine. Limit the radiation dose to involved persons … the first action during any emergency is to turn off the machine. If radioactive materials are involved, limit the spread of contamination. Seek assistance from experienced radiation safety professionals. Contact the Accuray RSO and local Radiation Safety Personnel. Evacuate the immediate area of the incident. Control entry to the scene of the accident. Indentify and isolate persons who may have received significant radiation exposures. Record all details of the event chronologically.

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