Introduction To Nuclear Power Module 3: Understanding Radiation and Its Effects

Transcription

1 Introduction To Nuclear Power Module 3: Understanding Radiation and Its Effects Course # 9CCKN1002 Nathan Hoffman, PhD Greg Johnson, PhD, PE Phil Rutherford R.Z. Litwin (Editor) 1

2 Introduction To Nuclear Power Course 1, Five Modules total Module 1: Basics of Nuclear Science Module 2: Reactor Engineering Module 3: Understanding Radiation and its Effects Module 4: Space Reactor History Module 5: Space Nuclear Safety 2

3 Module 3: Understanding Radiation & its Effects Five Lessons total Lesson 1 - Background Radiation Lesson 2 - Radiation Terminology Lesson 3 - Health Effects Lesson 4 - Cancer Risk Model Lesson 5 - Summary References Biography 3

4 Module 3: Understanding Radiation & its Effects Table of Contents Background Radiation (6) Radiation & Radioactivity in Our Environment (7) Radiation Levels for Various Household Items (8) Contributions to Background Radiation (9) Radiation Terminology (10) How Fast do Radioisotopes Decay? (11) Specific Activity (12) Difference between Radiation and Contamination (13) What is a Dose of Radiation? (14) Typical Radiation Doses (15) Regulatory Dose Limits (16) External Exposure vs. Internal Exposure (17) Effects of Shielding on Different Types of Radiation (18) 4

5 Module 3: Understanding Radiation & its Effects Table of Contents cont Health Effects (19) Types of Exposure and Health Effects (20) Somatic Health Effects from High Acute Doses (21) Populations with Health Effects from Acute Doses (22) Stochastic Cancer Effects (23) Radiosensitive Cells (24) Cancer Risk Model (25) Linear No-Threshold Model of Cancer Risk (26) Theoretical Cancer Risks of Radiation (27) Summary (28) Module Summary (29) References (30) Biography (31) 5

6 Module 3: Understanding Radiation & its Effects Lesson 1 Lesson 1 - Background Radiation Lesson 2 - Radiation Terminology Lesson 3 - Health Effects Lesson 4 - Cancer Risk Model Lesson 5 - Summary Learning Objectives for lesson 1: At the end of this lesson, the student will have a general understanding of the sources of naturally occurring environmental radiation. 6

7 Background Radiation Radiation and Radioactivity in our Environment Lesson 1 We are constantly exposed to low levels of radiation from outer space Low levels of naturally occurring radioactive material are in our environment, soil, rocks water and the food we eat Some consumer products also contain small amounts of radioactive material Aurora Borealis Lantern Mantle No Salt Smoke Detector Fiestaware Radiation and and radioactivity is is a natural part part of of our our environment 7

8 Background Radiation Radiation Levels from Various Household Items Lesson 1 Alpha Radiation Beta Radiation Gamma Radiation Household Item Radioactive (ZnS Scintillator) (Geiger-Muller Tube) (NaI Scintillator) Material counts/min dpm/100cm 2 counts/min dpm/100cm 2 micror/hour counts/min (gross) (net) (gross) (net) (gross) (gross) Background Radiation Smoke Detector Fertilizer (Superphosphate) Lead Crystal Glassware Fertilizer (Potassium Sulphate) NoSalt (Potassium Chloride) Weld Rod Household Airborne Dust Camping Lantern Mantle Fiestaware Americium-241 Uranium Lead-210 Potassium-40 Potassium-40 Thorium-232 Radon daughters Thorium-232 Uranium , , , , , , , , , , , ,000 37, , ,378 2,500 96, ,000 1,400 13,640 4, , ,000 2,000 19,490 45,000 1,775, ,000 Regulatory Standards for Release of Radiological Facilities and Materials Thorium Uranium Fission Products - 1,000-1, ,000-5, , , ,000 Common household items items are are radioactive 8

9 Background Radiation Contributions to Background Radiation Lesson 1 Average Background Exposure = mrem mrem per per year year 9

10 Module 3: Understanding Radiation & its Effects End of Lesson 1 This concludes this portion of the CBT. Please close this window and select the next module. 10

11 Module 3: Understanding Radiation & its Effects Lesson 2 Lesson 1 - Background Radiation Lesson 2 - Radiation Terminology Lesson 3 - Health Effects Lesson 4 - Cancer Risk Model Lesson 5 - Summary Learning Objectives for lesson 2: At the end of this lesson, the student will have a general understanding of radiation terminology, controls, regulatory limits and types of exposure. 11

12 Radiation Terminology How Fast do Radioisotopes Decay? Lesson 2 The half-life describes how quickly radioisotopes decay away with time. It is the time required for half of the unstable atoms to decay. Some Examples: Some natural isotopes (like uranium, thorium and potassium-40) have halflives that are billions of years, Most medical isotopes (like Technicium- 99m) last only a few hours to a few days Decay of carbon-14 τ 1/2 = 5,570 years N(t) = N 0 e -t/τ 1/2 Radioisotopes decay decay at at different rates, rates, from from fractions of of a second to to billions of of years years 12

13 Radiation Terminology Specific Activity Lesson 2 Specific activity is the amount of radioactivity (in curies) found in a gram of material. Radioactive material with a long halflife has low specific activity and therefore a relatively lower hazard Cobalt-60: 1 gram Half-life (years) Specific activity (Ci/g) Mass Cobalt ,130 1 gram Natural Uranium 2.2 billion 6.97 x ,620 tons Uranium fuel pellets: 1,620 tons The The amount of of radioactivity is is not not necessarily related related to to its its size size 13

14 Radiation Terminology Difference between Radiation and Contamination Lesson 2 Exposure to radiation will not contaminate you or make you radioactive Contamination is radioactive material spilled someplace you don t want it Contact with contamination can contaminate you with the material, resulting in continued exposure to radiation Radiation is is transfer of of energy. Contamination is is unwanted radioactive material 14

15 Radiation Terminology What is a Dose of Radiation? Lesson 2 R (roentgen) is a measure of exposure or the amount of ionization in air Rad (radiation absorbed dose) is a measure of the amount of energy deposited in any material (1 R = rad) Rem (roentgen equivalent man) is a measure of the amount of energy deposited in human tissue Rem is the measure of tissue damage 1 rem = 1 rad x quality factor Small doses expressed in mrem = 1/1000 rem R, R, rad radand and rem rem are are frequently (though incorrectly) used used interchangeably 15

16 Radiation Terminology Typical Radiation Doses Lesson 2 Average Dose to US Public from All sources Average Dose to US Public From Natural Sources Average Dose to US Public From Medical Uses Average dose to US Public from Weapons Fallout Coal Burning Power Plant Average dose to US Public from Nuclear Power Sleeping with one s partner Coast to coast airplane roundtrip Living in a brick house Chest X ray Working in a granite building Heart Stress Test CAT Scan (head and body) Therapeutic thyroid treatment (dose to the whole body) Smoking one pack of cigarettes per day (dose to lung) Wide Wide range range of of radiation doses doses from from different sources 360 mrem/year 300 mrem/year 60 mrem/year <1 mrem/year 0.2 mrem/year < 0.1 mrem/year 2 mrem/year 5 mrem 7 mrem/year 8 mrem 50 mrem/year 500 mrem 1,100 mrem 7,000 mrem 8,000 mrem/year 16

17 Radiation Terminology Regulatory Dose Limits Lesson 2 Regulatory Limit mrem/year Occupational Dose Limit for Radiation Workers - Whole body 5,000 - Lens of eye 15,000 - Extremities (arms, legs) 50,000 - Internal organs, skin 50,000 Limit for Radiation Workers (whole body) 2,000 rad-worker exposures during the last 10 years - Maximum annual individual (actual) Average annual (actual) 13 Limit for members of the public - Operating nuclear or radiological facility (total) - Airborne effluent - Drinking water suppliers exposures are are well well below below regulatory limits limits 17

18 Radiation Terminology External Exposure vs. Internal Exposure Lesson 2 External Exposure Source is external to the body Gammas and neutrons (cesium-137, cobalt-60, radium- 226, and reactors) Betas (skin only) Mitigated by shielding, distance and time Measured by dosimetry worn on the body (e.g. film badges, thermo-luminescent dosimeters) Internal Exposure Inhalation, ingestion, & dermal (e.g. cuts, abrasions) Alphas (uranium, thorium, plutonium) Mitigated by workplace air sampling, use of respirators Measured, after the fact, by urinalysis, whole body scans External exposure and and internal exposure require different controls 18

19 Radiation Terminology Effects of Shielding on Different Types of Radiation Lesson 2 Radiation exposure can can be be reduced by by shielding 19

20 Module 3: Understanding Radiation & its Effects End of Lesson 2 This concludes this portion of the CBT. Please close this window and select the next module. 20

21 Module 3: Understanding Radiation & its Effects Lesson 3 Lesson 1 - Background Radiation Lesson 2 - Radiation Terminology Lesson 3 - Health Effects Lesson 4 - Cancer Risk Model Lesson 5 - Summary Learning Objectives for lesson 3: At the end of this lesson, the student will have a general understanding of acute and chronic exposures, and somatic and stochastic health effects. 21

22 Health Effects Types of Exposure & Health Effects Lesson 3 Acute Dose Large radiation dose in a short period of time Large doses may result in observable health effects Early: Nausea & vomiting Hair loss, fatigue, & drop in white blood count Burns and wounds heal slowly Examples: medical therapeutic exposures and accidental exposure to sealed sources Chronic Dose Radiation dose received over a long period of time Body more easily repairs damage from chronic doses Does not usually result in immediate observable effects Examples: Background radiation and occupational exposure Health Health effects effects differ differ for for acute acute vs. vs. chronic exposures 22

23 Health Effects Somatic Health Effects from High Acute Doses Lesson 3 Dose (Rem) Effects First sign of physical effects (drop in white blood cell count) Threshold for vomiting (within a few hours of exposure) ~ 50% die within 60 days (with minimal supportive care) ~50 % die within 60 days (with supportive medical care) 1,000 ~ 100% die within 30 days High High acute acute doses doses result result in in immediate health health effects effects 23

24 Health Effects Populations with Health Effects from Acute Dose Lesson 3 High dose effects seen in: Early researchers Radium dial painters Early radiologists Atomic bomb survivors Populations near Chernobyl Medical treatments Criticality accidents In addition to acute effects, increased cancer rates were also evident from high level exposures Radium Dial Painters Fluoroscope Chernobyl At At high high doses doses and and dose dose rates rates we we know know that that radiation causes harm harm Roentgen s hand 24

25 Health Effects Stochastic Cancer Effects Lesson 3 Our body has ~ 60 trillion cells As a result of normal bodily processes, each cell suffers a DNA break about every 10 seconds, resulting in millions of DNA breaks per cell each year Majority are repaired Some cells die Small number of cells mutate, malfunction (cancer) Background radiation levels cause only a very small fraction of these breaks (~ 5 DNA breaks per cell each year) Our Our bodies bodies are are resilient resilient with with highly highly efficient efficient DNA DNA repair repair mechanisms. mechanisms. Radiation Radiation is is not not a major major cause cause of of cancer. cancer. 25

26 Health Effects Radiosensitive Cells Lesson 3 Rapidly dividing cells are more susceptible to radiation damage. Dividing Cells Examples of radiosensitive cells are Blood forming cells The intestinal lining Hair follicles A fetus Dividing cells cells are are the the most most radiosensitive 26

27 Module 3: Understanding Radiation & its Effects End of Lesson 3 This concludes this portion of the CBT. Please close this window and select the next module. 27

28 Module 3: Understanding Radiation & its Effects Lesson 4 Lesson 1 - Background Radiation Lesson 2 - Radiation Terminology Lesson 3 - Health Effects Lesson 4 - Cancer Risk Model Lesson 5 - Summary Learning Objectives for lesson 4: At the end of this lesson, the student will have a general understanding of the model used to estimate radiation induced cancer risk. 28

29 Cancer Risk Model Linear No-Threshold (LNT) Model of Cancer Risk Lesson 4 Regulatory bodies require the use of the linear-no-threshold (LNT) model of radiation risk LNT assumes that the risk of cancer is proportional to the exposure level (no matter how small) Radiation risk at low doses is extrapolated from observed cancer effects at high doses (e.g. from atomic bomb survivors) No physical effects have been observed at low doses typical of background radiation levels Controversial, conservative, assumes no threshold, lack of health effects in high background regions Linear threshold model Linear no threshold model A-bomb survivor data Many Many health health physicists believe that that no no cancer cancer risk risk exists exists below below ~ rem rem 29

30 Cancer Risk Model Theoretical Cancer Risks of Radiation Lesson 4 Radiation is assumed to increase one s risk of cancer The normal chance of dying of cancer is ~ 23% ~2,300 out of 10,000 Each additional rem of radiation exposure is assumed to increase that risk by 0.05% ~5 out of 10,000 Theoretical radiation cancer cancer risk risk is is low low compared to to all all other other cancer cancer risks risks 30

31 Module 3: Understanding Radiation & its Effects End of Lesson 4 This concludes this portion of the CBT. Please close this window and select the next module. 31

32 Module 3: Understanding Radiation & its Effects Lesson 5 Lesson 1 - Background Radiation Lesson 2 - Radiation Terminology Lesson 3 - Health Effects Lesson 4 - Cancer Risk Model Lesson 5 - Summary Learning Objectives for lesson 5: At the end of this lesson the student will have an understanding of the major points covered and be given the references used in this module. 32

33 Summary Lesson 5 Low levels of radiation and radioactivity are ubiquitous in our environment Regulatory process for the management and control of radioactive materials developed during the 50 years since the introduction of the Atomic Energy Act Conservative models utilized to calculate health risks 33

34 References Lesson 5 Boeing Canoga Park Radiation Safety web site Environmental Protection Agency Nuclear Regulatory Commission Department of Energy Other 34

35 Biography Phil Rutherford has an M.A. in physics, with a major in nuclear physics from Oxford University, and an M.S. in nuclear engineering from the University of Birmingham (UK). He has 31 years experience in the nuclear industry. His initial responsibilities were reactor analysis and plant transient analysis for GE s Nuclear Energy Division in San Jose, CA, and probabilistic risk assessment (PRA) for the South African Atomic Energy Board. During the 1980 s, he was responsible for reliability analysis and nuclear risk analysis for all of s ground-based and space-based nuclear power programs. In 1988 he became Manager of Nuclear Safety and Reliability (taking over from Joe Mills). Since 1990, he has managed the Radiation Safety department at Boeing s Santa Susana Field Laboratory where the Department of Energy is conducting facility decommissioning and environmental remediation. Phil was the nuclear safety sub-ipt for the JIMO Phase A, Task 2 study contract and the JIMO Phase B proposal. Lesson 5 35

36 Module 3: Understanding Radiation & its Effects End of Lesson 5 and CBT This concludes the CBT. Please close this window and the Table of Contents window. Then select the Test and Credit button. 36