☢️Radiochemistry Unit 13 – Radiation Safety and Protection

Fundamentals of Radiation

• Radiation is the emission or transmission of energy in the form of waves or particles through space or a medium
• Ionizing radiation has enough energy to remove electrons from atoms or molecules, creating ions
• Non-ionizing radiation does not have enough energy to ionize atoms or molecules (radio waves, microwaves, visible light)
• Radioactivity is the spontaneous emission of radiation from unstable atomic nuclei
• Half-life is the time required for half of a given quantity of a radioactive substance to decay
• Activity is the rate of decay of a radioactive substance, measured in becquerels (Bq) or curies (Ci)
  • 1 Bq = 1 disintegration per second
  • 1 Ci = 3.7 × 10^10 disintegrations per second
• Radiation can be attenuated by shielding materials (lead, concrete, water)

Types of Ionizing Radiation

• Alpha particles consist of two protons and two neutrons, equivalent to a helium nucleus
  • Highly ionizing but short range, can be stopped by a sheet of paper or skin
  • Hazardous when inhaled or ingested
• Beta particles are high-energy electrons emitted from the nucleus during radioactive decay
  • More penetrating than alpha particles, can be stopped by a few millimeters of aluminum or plastic
  • Can cause skin burns and be hazardous when inhaled or ingested
• Gamma rays are high-energy electromagnetic radiation emitted from the nucleus during radioactive decay
  • Highly penetrating, requires dense materials like lead or concrete for shielding
  • Can cause whole-body irradiation
• X-rays are similar to gamma rays but originate from the electron shell rather than the nucleus
• Neutron radiation occurs when neutrons are ejected from the nucleus during nuclear reactions or spontaneous fission
  • Highly penetrating and can cause activation of materials
  • Requires specialized shielding (water, paraffin wax, boron)

Radiation Exposure and Dose

• Exposure is a measure of the amount of ionization produced in air by X-rays or gamma rays, measured in roentgens (R)
• Absorbed dose is the amount of energy deposited per unit mass of material, measured in grays (Gy) or rads
  • 1 Gy = 1 J/kg
  • 1 rad = 0.01 Gy
• Equivalent dose takes into account the biological effectiveness of different types of radiation, measured in sieverts (Sv) or rem
  • Obtained by multiplying the absorbed dose by a quality factor (QF) specific to each type of radiation
  • 1 Sv = 1 J/kg × QF
  • 1 rem = 0.01 Sv
• Effective dose is the sum of the equivalent doses to each organ or tissue, weighted by their radiation sensitivity, also measured in Sv or rem
• Committed dose is the total dose received over a 50-year period following the intake of a radioactive substance
• Collective dose is the sum of the individual doses received by a group of people, measured in person-Sv or person-rem

Biological Effects of Radiation

• Radiation can cause direct damage to biomolecules (DNA, proteins, lipids) or indirect damage through the production of free radicals
• Deterministic effects have a threshold dose below which the effect does not occur, and the severity increases with dose (skin erythema, cataracts, sterility)
• Stochastic effects have no threshold dose, and the probability of the effect increases with dose (cancer, genetic mutations)
• Acute radiation syndrome (ARS) occurs when the body receives a high dose of radiation over a short period
  • Hematopoietic syndrome (0.7-10 Gy): damage to bone marrow and immune system
  • Gastrointestinal syndrome (10-50 Gy): damage to intestinal lining
  • Neurovascular syndrome (>50 Gy): damage to nervous system and cardiovascular system
• Chronic radiation exposure can lead to an increased risk of cancer, cataracts, and cardiovascular disease
• Teratogenic effects can occur when a developing embryo or fetus is exposed to radiation (growth retardation, malformations, mental retardation)
• Genetic effects are the result of radiation-induced mutations in germ cells that can be passed on to future generations

Radiation Detection and Measurement

• Gas-filled detectors rely on the ionization of a gas by radiation (ionization chambers, proportional counters, Geiger-Müller tubes)
  • Ionization chambers measure the total charge produced by radiation
  • Proportional counters amplify the charge through gas multiplication
  • Geiger-Müller tubes produce a large pulse for each ionizing event
• Scintillation detectors use materials that emit light when exposed to radiation (NaI(Tl), plastic scintillators)
  • The light is converted to an electrical signal by a photomultiplier tube
• Semiconductor detectors use materials like silicon or germanium that produce electron-hole pairs when exposed to radiation
• Neutron detectors rely on nuclear reactions to detect neutrons (BF3 proportional counters, 3He proportional counters)
• Thermoluminescent dosimeters (TLDs) measure accumulated dose by heating a crystal and measuring the released light
• Film badges use radiation-sensitive film to measure accumulated dose
• Survey meters are portable devices used to measure radiation levels in an area (dose rate meters, contamination meters)
• Spectrometers measure the energy distribution of radiation (gamma spectrometers, alpha spectrometers)

Radiation Safety Principles

• Time, distance, and shielding are the three basic principles of radiation protection
  • Minimize time spent in radiation areas
  • Maximize distance from radiation sources
  • Use appropriate shielding materials
• ALARA (As Low As Reasonably Achievable) is the guiding principle for radiation protection
  • Optimize procedures to reduce exposure
  • Use engineering controls (ventilation, remote handling)
  • Implement administrative controls (training, procedures, signage)
• Contamination control involves preventing the spread of radioactive materials
  • Use containment devices (glove boxes, fume hoods)
  • Practice good housekeeping and personal hygiene
  • Monitor for contamination regularly
• Proper waste management is essential for minimizing environmental impact
  • Segregate waste by type (solid, liquid, gaseous) and activity level
  • Use appropriate containers and labeling
  • Follow regulations for storage, treatment, and disposal
• Radiation areas should be properly marked with signs and labels
  • Controlled areas have restricted access and require dosimetry
  • Radiation areas have dose rates >0.05 mSv/h at 30 cm from the source
  • High radiation areas have dose rates >1 mSv/h at 30 cm from the source
  • Very high radiation areas have dose rates >5 Gy/h at 1 m from the source
• Dosimetry programs monitor individual and workplace exposures
  • Personal dosimeters (TLDs, OSLDs, electronic dosimeters) measure individual dose
  • Area monitors measure dose rates in specific locations
  • Bioassay programs monitor internal contamination through urine or fecal analysis

Personal Protective Equipment (PPE)

• PPE is used to minimize external and internal exposure to radiation and contamination
• Protective clothing includes lab coats, coveralls, shoe covers, and gloves
  • Should be made of materials that are easy to decontaminate (cotton, polyester)
  • Disposable PPE is used in high contamination areas
• Respiratory protection is used to prevent inhalation of radioactive particles or gases
  • Particulate respirators (N95, P100) filter out particles
  • Supplied-air respirators provide clean air from an external source
  • Self-contained breathing apparatus (SCBA) provides air from a portable tank
• Face and eye protection includes safety glasses, goggles, and face shields
• Dosimeters should be worn outside of PPE to measure actual exposure
• PPE should be properly donned, doffed, and disposed of to avoid contamination
  • Use a step-off pad when removing PPE
  • Monitor hands, feet, and clothing for contamination after removing PPE
• PPE should be regularly inspected and maintained to ensure effectiveness

Regulatory Framework and Standards

• International Commission on Radiological Protection (ICRP) provides recommendations for radiation protection
  • ICRP Publication 103 (2007) is the current set of recommendations
• International Atomic Energy Agency (IAEA) develops safety standards and guides for member states
  • IAEA Safety Standards Series includes General Safety Requirements (GSR) and Specific Safety Guides (SSG)
• National regulatory bodies implement and enforce radiation protection regulations
  • In the United States, the Nuclear Regulatory Commission (NRC) regulates the use of byproduct, source, and special nuclear materials
  • The Environmental Protection Agency (EPA) sets standards for public exposure and environmental releases
  • The Occupational Safety and Health Administration (OSHA) regulates workplace safety, including radiation exposure
• Dose limits are set to protect workers and the public from the harmful effects of radiation
  • Occupational dose limit: 50 mSv/year, with a maximum of 100 mSv over 5 years
  • Public dose limit: 1 mSv/year
  • Dose limits for specific organs (lens of the eye, skin, hands and feet) are also established
• Licensees must implement radiation protection programs that comply with regulations
  • Radiation Safety Officer (RSO) is responsible for overseeing the program
  • Radiation Safety Committee (RSC) reviews and approves the use of radioactive materials
  • Written policies and procedures must be developed and followed
• Recordkeeping and reporting requirements ensure compliance and transparency
  • Personnel monitoring records must be maintained for the lifetime of the facility
  • Incident and overexposure reports must be submitted to the regulatory body
  • Annual reports on the radiation protection program must be provided to management

Emergency Procedures and Decontamination

• Emergency procedures are designed to minimize the consequences of accidents or incidents involving radiation
• Spill procedures involve containing and cleaning up radioactive contamination
  • Notify personnel and restrict access to the area
  • Use absorbent materials to prevent the spread of contamination
  • Decontaminate surfaces using appropriate methods (washing, wiping, vacuuming)
  • Monitor the area to ensure contamination levels are below regulatory limits
• Fire procedures prioritize life safety and fire control
  • Evacuate personnel and notify emergency responders
  • Use appropriate extinguishing agents (water, foam, dry chemical)
  • Monitor for radioactive contamination in smoke and runoff water
• Medical emergencies involving radiation exposure or contamination require specialized care
  • Assess and treat life-threatening injuries first
  • Remove contaminated clothing and decontaminate skin
  • Estimate dose and monitor for acute radiation syndrome
  • Consult with radiation medicine specialists
• Decontamination involves removing or reducing radioactive contamination from surfaces, equipment, or personnel
  • Physical methods include washing, wiping, brushing, and vacuuming
  • Chemical methods use solutions to dissolve or chelate contaminants (detergents, acids, chelating agents)
  • Mechanical methods use abrasion or ultrasonic cleaning to remove contamination
  • Decontamination wastes must be properly characterized, packaged, and disposed of
• Personnel decontamination follows a systematic approach
  • Remove contaminated clothing and store in labeled containers
  • Survey skin and hair for contamination using a sensitive detector
  • Wash contaminated areas with mild soap and lukewarm water, starting with the least affected areas
  • Avoid harsh scrubbing or abrasive materials that can damage the skin
  • Monitor the effectiveness of decontamination and repeat as necessary
  • Refer to medical attention if contamination persists or skin damage occurs
• Emergency drills and exercises are conducted regularly to test response capabilities and identify areas for improvement
  • Tabletop exercises involve discussion-based scenarios
  • Functional exercises test specific functions or capabilities
  • Full-scale exercises simulate realistic conditions and involve multiple organizations