Module 1 – Basic Radiation Principles Radiation Safety Training
Radiation Postings / Labels • Rule .03 (11) specifies requirements for: • posting or labeling • Rooms • Containers • Machines • exemptions to above Standard Radiation Symbol
Laboratory Postings Required “Notice to Workers” and Emergency Contact Information should be posted at the entrance to your lab Caution Sign and Hazards Radioactive Materials Posting Lab Emergency Phone Numbers Georgia DNR Notice to Workers RSO Emergency Phone Numbers
Door Sign • Waste Containers (every 180 o) • Radioactive Materials Use Hoods • RAM Use and Storage Areas • Any location that contains RAM
Required posting when an area exceeds 5 mrem/hr. • or exceeds 100 mrem in 5 consecutive days • containers are included, but surveyed at 6 inches for dose rate Reach your yearly whole body limit of 5 rem in ~1000 hours (42 days)
Posted when decontamination of a large area is in progress. • Usually posted on a barricade • Authorized by RSO entry only • PPE is required for entry • Instructions accompany this posting.
Posted when airborne contamination fills a large contained area • Usually posted on a barricade • Authorized by RSO entry only • Respiration equipment and PPE is required for entry • Instructions accompany this posting.
Conspicuously posted in an area where an open x-ray beam is present • Usually applies to non- medical open beam x-ray equipment.
Emergency Warnings • Temporary postings may be placed to warn of emergency procedures in progress • DO NOT CROSS MARKED BARRIERS or ENTER POSTED AREAS Follow Emergency Responder Instructions
Read the Posting !! • Radiation signs contain important information • If you don’t know about the radiation or radioactive materials ASK !! • Be forewarned
Chp 1, “Radiation Safety Organization” Chp 2, “Principles of Radiation Safety”” Chp 3, “Radiation Exposure Limits” Chp 4, “Facilities and Equipment Considerations” Chp 5, “Procurement and Transfer of Radioactive Materials” Chp 6, “Radiological Surveys” Chp 7, “Radiological Postings” Chp 8, “Response to Radiological Incidents” Chp 9, “Laboratory Procedures” Chp 10, “Radioactive Waste Handling and Disposal” Chp 11, “Radiological Improvement Program” 2003 Chp 12, “Radiation Producing Equipment”
RADIATION PHYSICAL FORMS –BASIC DEFINITIONS
Structure of the Atom Nucleus Neutrons + + + Protons Electrons (Electron Clouds)
Elements and Isotopes Half-Life 1 – 10 days 10-100 days Periodic Table of Elements Chart of the Nuclides
Radioactivity Definition Any spontaneous change in the state of the nucleus accompanied by the release of energy. Major Types alpha () particle emission (decay) beta () particle emission (-), positron emission (+) and orbital electron capture (ec) gamma () decay including internal conversion
Radioactivity • Radioactivity and radioactive properties of nuclides are; • Determined by nuclear considerations only! • Independent of the chemical and physical states of the radioisotope • Cannot be changed by any means except for decay • Unique to the respective radionuclide
Ionizing Radiation + + Definition - Any type of radiation possessing enough energy to eject an electron from an atom, thus producing an ion. Major Types of Ionizing Radiation Alpha, Beta, Gamma Alpha Particle Large Mass (nuclei) – Helium Atom with a +2 charge Beta Particle Small Mass - Electron (subatomic particle) No Mass (Electromagnetic Radiation) Gamma Photon and X-Rays
a) External radiation hazard Typical laboratory quantities of uranium salts do not represent a significant external radiation hazard, as the alpha particles do not penetrate the external dead layer of skin. There are beta and gamma emitters in the 238U decay chain, but the betas also do not have enough energy to penetrate the skin, and the amount of gamma radiation is minimal.
b) Inhalation or ingestion hazard The primary radiological hazard arises from inhalation or ingestion of the uranium compound, which leads to irradiation of lung and bone cells causing an increased risk of cancer. A chemical hazard also arises from inhalation or ingestion, as uranium is a heavy metal and can damage the kidneys. Absorption through the skin is not significant, but contact with the substance can cause irritation and increases the risk of ingestion. Overall, there is a minimal external risk from the radiation emitted by uranyl acetate and uranyl nitrate, and a relatively large risk arising from internal exposure following inhalation or ingestion. It is therefore essential to adopt appropriate controls when handling unsealed uranium salts to minimise this risk: reduce the amount being handled as much as possible contain the unsealed sources to prevent contamination maintain a high level of cleanliness.
Hazard control and safe practice With the most serious hazard arising from inhalation or ingestion, extra care should be taken to prevent any possibility of inhaling fine particles. Gloves must always be worn when handling or weighing out the uranium salts. Under normal circumstances when using the compound infrequently and working with small quantities of up to 10g, respiratory protection is not necessary. Avoid contamination of bench surfaces by using spill trays (metal or plastic) with disposable coverings such as benchcote and clean the surface after use. If an appropriate thin window GM tube survey meter is available, then it can be used to monitor for contamination. Apply the same principles when working in solution.
Activity Definition – The rate of decay of a radioactive sample, i.e. by the number of atoms that decay per unit time. Units of Activity
International Unit of Activity Becquerel (Bq) 1.00 Bq = 1 dps 60.00 Bq = 1 dpm 1.00 Ci = 3.7 x 1010 Bq
Know the difference!!!! radiation energy in the form of particles or waves emitted from a radiation source contamination radioactive material in an undesirable location Can radiation be contamination?Can contamination be radiation?
HALF-LIFE (T1/2) The time required for a radioactive substance to loose 50 percent of its activity by decay. Each radionuclide has an unique half-life. Half-life is expressed by the following Expression; A =A0e-l(Dt) Where; Ao = original activity l = .693/half-life of nuclide Dt = difference between reference date and present time
Counts, Count Rate, Net Count Rate & Background Counts are the number of non-qualifiable radioactive events seen by a detector Count rate is the number of counts seen per unit time as counts per second (cps) and counts per minute (cpm). Net count rate is the number of counts seen per unit time adjusted for the background count rate Background is the ambient count rate
Counting Efficiency Counting efficiency is the calibration of count rate in a specific detector where to quantify and express the observed count rate in units of radioactivity Cpm/dpm = efficiency Each isotope of interest has it own counting efficiency, Liquid Efficiencies (LSC) H-3 (.35), C-14 (.85), P-32(.98), P-33(.85) S-35(.85), I-125(.75), I-131(.85) P-32 Cerenkov(.30)
Liquids/Wastes Counting Calculations Sample CPM – Background CPM 2.22E+6 DPM/uCi X EFF X V(G)=uCi/V(G) Liquid Efficiencies (LSC) H-3 (.35), C-14 (.85), P-32(.98), P-33(.85) S-35(.85), I-125(.75), I-131(.85) P-32 Cerenkov(.30)
Wipe Test Calculations Results must be in DPM/100 cm2 DPM/ 100 cm2 = Wipe CPM – BKG CPM (Eff) For all Isotopes Eff = 0.33 Therefore; DPM/ 100 cm2 = (Wipe CPM – BKG CPM) X 3
Determination of Minimum Detectable Activity (MDA) _________________ MDA in dpm = 2.71 + 4.66 √ bkg cpm x count time (eff) (count time) ______________MDA in uCi/ml = 2.71 + 4.66 √ bkg cpm x count time (2.22E+6 DPM/uCi)(Sample Vol.)(eff) (count time) MDA is the activity threshold for the counting instrument for a given background…to decrease this value, increase your counting timeot increase your sample size. Results less than this value are reported as <MDA
Radiation Dosimetry Units Exposure, X: amount of charge produced anywhere in air by the complete stoppage of all electrons liberated by photons in an incremental volume of air per unit mass of air in that volume. Standard International (SI) unit: Coulomb/kilogram (C/kg) Traditional unit: roentgen ( R ) 1 R = 2.58x10-4 C/kg Exposure definition applies only to photons of energy less than or equal to 3 MeV interacting in air.
Radiation Dosimetry Units Absorbed dose: RAD is the energy deposited by any type of ionizing radiation in a volume element of mass. SI unit: gray (Gy) Traditional unit: rad 1Gy = 100 rad Absorbed dose definition applies to all forms of ionizing radiation in any material.
Biological effect of radiation Y at dose X Biological effect of 250 kVp x-rays at dose X Both produce the same biological effect. ) ( Relative Biological Effectiveness and Quality Factor Relative Biological Effectiveness (RBE) Quality factor (Q) radiationQ photon, 1 proton, neutron 10 alpha 20
Relative Biological Effectiveness Ln (S) Shoulder of curve indicates cell repair at low doses No shoulder - no cell repair Neutrons Effect Gamma Photons Dn Dg Same Biological Effect Different Dose from 2 types of radiation Dose