Laboratory Safety 197/405. Types of Radiation 198/405

Transcription

1 Laboratory Safety 197/405 Types of Radiation 198/405

2 Particle Radiation Alpha He nucleus (heavy particle) +2 charge Internal hazard only Beta Electron -1 charge Internal and external hazard Neutron 199/405 Photon Radiation Gammas and X-rays are identical except in their origin Gammas - produced from the nucleus of an atom X-rays are produced outside the nucleus of an atom Very penetrating radiation Must have shielding for protection 200/405

3 Shielding for, and Neutron shielding material depends on the energy of the neutrons 201/405 Radiation Units Exposure (R) (roentgen) 조사선량 ( 공기 ) Amount of charge produced per unit mass of air from x-rays and gamma rays. Based on the quantity of electrical charges produced in air by X-ray or Gamma photons. 1R=2 billion pr Absorbed Dose (rad) 흡수선량 ( 물질 ) Radiation Absorbed Dose is the work energy resulting from the absorption of one ROENTGEN or 6.24 E5 Mev Amount of Energy deposited per unit mass of material. 1Gy (GRAY) = 100 rad. Dose Equivalent (rem) 선량당량 ( 인체 ) Roentgen Equivalent Mammal is equal to the absorbed does in RADS multiplied by a quality factor The absorbed dose is weighted by the radiation type and tissue susceptibility to biological damage. 1 Sv (SIEVERT) = 100 rem 202/405

4 Measure of Amount of radioactive material Radiation Units Quantity Activity Unit curie (Ci) Ionization in air Absorbed energy per mass Exposure Absorbed Dose roentgen (R) rad 203/405 Absorbed dose weighted by type of radiation Dose Equivalent For most types of radiation rem 1 R 1 rad 1 rem Radiation Units Exposure (R) (roentgen) Absorbed Dose (rad) Dose Equivalent (rem) 204/405

5 Radiation Units 대상 단위명, 기호 정의 SI 단위 조사선량 R 공기 1kg 당 2.58 x 10-4 쿨롱의에너지흡수가있을때의선량. 1C/kg (= 3,876 R) 흡수선량 rad 물질 1g 당 100erg 의에너지흡수를 1red 로한다. 1Gy = 1J/kg = 100 rad 선량당량 rem 흡수선량 (D,rad) X 선량계수 (Q) X 수정계수 (N) 1Sv = D(Gy) X Q X N = 100 rem 방사능 Ci 3.7 X 개 / 초의비율로원자핵이붕괴될때의양을 1Ci 로한다. 1Bq = 2.7 X Ci 205/405 Units of Radioactivity Curie (Ci) = 2.22 X dpm or 3.7 X dps Becquerel (Bq) = 1 dps Maximum Dose/year = 5 REM or 50 msv Maximum Dose/year for Declared Pregnant Woman & Minors= 0.5 REM or 5 msv 206/405

6 Units of Exposure The threshold for damage to the human body is 100 rad. It is a measurement of exposure. 1 Rad = 1 Rem (10 msv) 1 rem = 1000 mrem Then, 100,000 mrem = 100 Rad 207/405 Examples of Natural Radiation 자연방사선에의한인체의피폭선량은 1년간평균 mrem 208/405

7 Smoking 담배를하루에 1 갑씩 1 년간계속피운사람의발암확률은, 7,000~28,000 mrem 의방사선피폭을받은사람의발암확률과같다. 209/405 Life Expectancy Lost Health Risk Smoking 20 cigs a day Overweight (15%) Alcohol (US Average) All Accidents Occupational dose (1 Rem/yr) Est. Life Lost 6 years 2 years 1 year 207 days 51 days 210/405

8 RADIATION PROTECTION PRINCIPLES The body may be irradiated in two general ways: Externally from radioactive material or radiation sources, External doses can be the result of exposure to gamma, X-ray, or high energy beta emitters. Low energy beta and alpha emitters lack the energy needed to penetrate the outer layer of skin and subsequently present less of an external hazard; they are of more concern when ingested. Internally from radioactive material deposited in the body. 211/405 RADIATION PROTECTION PRINCIPLES The external dose an individual receives depends on the following factors: exposure, time, distance, and shielding. Exposure. The "strength" (activity, mr/hr, etc.) of the radiation source. By reducing the amount of radioactive material used, dose can be reduced. Time. The total dose received from an external source also depends on the amount of time actually exposed to the source. Therefore, any time that is spent near a source should be minimized and used effectively. 212/405

9 RADIATION PROTECTION PRINCIPLES Distance. By increasing the distance between the source of exposure and an individual, the dose received can be significantly reduced. When an individual doubles his/her distance from a source, the dose will usually be reduced by approximately one-fourth. Shielding. When radiation sources are being used, absorbing material or shields can be incorporated to reduce exposure levels. The specific shielding material and thickness is dependent on the amount and type of radiation involved. 213/405 RADIATION PROTECTION PRINCIPLES Internal exposure results from the absorption, ingestion or inhalation of radioactive material. This material can be incorporated in the body in several ways: by breathing radioactive gases, vapors or dust by consuming radioactive material transferred from contaminated hands, tobacco products, food or drink by entering through a wound by absorption through the skin 214/405

10 RADIATION PROTECTION PRINCIPLES The fundamental objectives of radiation protection measures are: to limit entry of radionuclides into the human body (via ingestion, inhalation, absorption, or through open wounds) to quantities as low as reasonably achievable (ALARA) and always within the established limits. to limit exposure to external radiation to levels that the established dose limits are below and as low as reasonably achievable. 215/405 RI Lab Safety Rules Eating, drinking, smoking, and the application of cosmetics are prohibited in a room where radioactive materials are used or stored. Protective gloves shall be worn when handling contaminated or potentially contaminated items. Persons with open wounds should be particularly careful when working with radioactive materials (the wound should be properly covered). Hands should be washed thoroughly after handling radioactive materials, especially before eating. Food items shall not be stored in areas or equipment designated for radioactive materials. Personnel monitoring badges shall be worn in restricted areas, as applicable. 216/405

11 RI Lab Safety Rules Conduct radiation meter surveys after each use and wipe test surveys frequently (document at least monthly). When measurements are abnormal, find the cause and correct. When using volatile radionuclides (e.g. iodine) or heating radioactive solutions, always perform work in a properly operating fume hood. Label all containers of radioactive materials, including radionuclide, amount and date. Utilize shielding when necessary to maintain radiation levels as low as reasonably achievable (ALARA). Store radioactive material in locked cabinets/refrigerators or keep the laboratory door locked when lab personnel are not present. 217/405 Biological Effects Many groups exposed to ionizing radiation at high levels resulted in adverse effects. Somatic effects Prompt - skin burns and cataracts Delayed - cancer Genetic effects Teratogenetic effects 218/405

12 Cancer Radiation can damage cells through two methods; Production of free radicals Direct damage to the DNA. Risk factor for radiation dose: 4% increase in risk of dying of cancer for every 100 rem of dose. Normal cancer risk is 10%. 219/405 Radiation Doses and Dose Limits Flight from Los Angeles to London Annual public dose limit Annual natural background Fetal dose limit Barium enema Annual radiation worker dose limit Heart catheterization (skin dose) Life saving actions guidance (NCRP-116) Mild acute radiation syndrome LD 50/60 for humans (bone marrow dose) Radiation therapy (localized & fractionated) 5 mrem 100 mrem 300 mrem 500 mrem 870 mrem 5,000 mrem 26,000 mrem 50,000 mrem 200,000 mrem 350,000 mrem 6,000,000 mrem 220/405

13 Acute Exposure Large Doses Received in a Short Time Period Accidents Nuclear War Cancer Therapy Short Term Effects (Acute Radiation Syndrome 150 to 350 rad Whole Body) Anorexia, Nausea, Erythema, Fatigue, Vomiting, Hemorrhage, Diarrhea, Mortality 221/405 Acute Radiation Syndrome Occurs only in patients who have received very high radiation doses (greater than approximately 100 rem) to most of the body Dose ~ 15 rem No symptoms, possible chromosomal aberrations Dose ~ 50 rem No symptoms, minor decreases in white cells and platelets 222/405

14 Acute Radiation Syndrome Hematopoietic Component Dose ~ 100 rem ~10% exhibit nausea and vomiting within 48 hr mildly depressed blood counts Dose ~ 350 rem ~90% exhibit nausea/vomiting within 12 hr, 10% exhibit diarrhea within 8 hr severe bone marrow depression ~50% mortality without supportive care Dose ~ 500 rem ~50% mortality with supportive care Dose ~ 1000 rem % mortality despite supportive care 223/405 Acute Radiation Syndrome Gastrointestinal and CNS Components Dose > 1000 rem - damage to GI system severe nausea, vomiting and diarrhea (within minutes) short latent period (days to hours) usually fatal in weeks to days Dose > 3,000 rem - damage to CNS vomiting, diarrhea, confusion, severe hypotension within minutes collapse of cardiovascular and CNS fatal within 24 to 72 hours 224/405

15 Effects of Acute Whole Body Exposure on Man Absorbed Dose (Rads) Effect 10,000 1, Death in a few hours Death within days Death within weeks LD 50/30 Probable Recovery No observable effect Blood changes definite 1st Blood change obs 225/405 Chronic Health Effects from Radiation Radiation is a weak carcinogen at low doses No unique effects (type, latency, pathology) Natural incidence of cancer ~ 40%; mortality ~ 25% Risk of fatal cancer is estimated as ~ 5% per 100 rem A dose of 5 rem increases the risk of fatal cancer by ~ 0.25% A dose of 25 rem increases the risk of fatal cancer by ~ 1.25% 226/405

16 Variations in Sensitivity Wide variation in the radio sensitivity of various species Plants/microorganisms vs. mammals Wide variation among cell types Cells which divide are more sensitive Non-differentiated cells are more sensitive Highly differentiated cells (like nerve cells) are less sensitive 227/405 Variations in Sensitivity 동 물 X 선또는 선에대한반치사 (LD 50 ) 선량 양당나귀돼지염소개사람모르모트원숭이새앙쥐토끼흰쥐 2.05 (Gy) 2.30 ~ ~ ~ 3.20 ~ ~ ~ ~ ~ ~ /405

17 Effects on the Fetus The fetus consists of rapidly dividing cells Dividing cells are more sensitive to radiation effects than non-dividing cells Effects of low level radiation are difficult to measure A lower dose limit is used for the fetus 229/405 Genetic Effects It is possible to damage the hereditary material in a cell nucleus by external influences like Ionizing radiation, chemicals, etc. Effects that occur as a result of exposure to a hazard while in-utero are called teratogenic effects Teratogenic effects are thought to be more severe during weeks 8~17 of pregnancy - the period of formation of the body s organs A higher incidence of mental retardation was found among children irradiated in-utero during the bombings of Hiroshima and Nagasaki 230/405