Protection Against Radiation

1. Protection Against Radiation ACADs (08-006) Covered Keywords contamination, decontamination, dose equivalent, effective dose, committed dose, absorbed dose, exposure dose, committed dose equivalent, committed effective dose equivalent, radiation exposure limits, airborne radiation, 10CFR20, 10CFR100, NRC, time distance shielding, shielding, exposure control, buildup, protective clothing, ALARA, deep, shallow. Description This module explains the legal requirements to ensure radiation exposure is controlled. Legal limits are discussed along with the ways to limit exposure.

2. Overview • Legal standards and administrative procedures to protect radiation workers from the hazards of radiation exposure • All employees in nuclear industry required to comply with certain federal government regulations with respect to radiation protection • Plants licensed by the Nuclear Regulatory Commission (NRC) must meet all established radiation protection criteria Module 4: Protection Against Radiation NET 130 Module 4: Protection Against Radiation 2

3. Overview • Protection from Radiation • Time-distance-shielding concept • If exposure time is minimized, dose is minimal • Shielding: when time and distance criteria are impractical • Decontamination (external) • Protective clothing • Internal contamination and resulting exposure is difficult to measure • Not all of the effects of radionuclides that may get into the body are known • Once radioactivity enters the body, only natural biological processes and radiological decay can remove it. • To avoid this hazard, respiratory protection equipment is worn to prevent inhaling airborne radioactivity in designated areas. Module 4: Protection Against Radiation NET 130 Module 4: Protection Against Radiation 3

4. Overview • Actual incidents involving overexposure have contributed to knowledge about radiation damage. • Results studied and policies established to prevent recurrence • Can be avoided by: • Proper application of established procedure • Being aware of changing plant conditions • Adhering to basic exposure reduction principles of time, distance, and shielding • Studies of long-term effects still being conducted • Measures have been devised and implemented to prevent exposure to unnecessary radiation, even at low dose levels. • Refer to SOERs 85-3 and 01-1 Module 4: Protection Against Radiation NET 130 Module 4: Protection Against Radiation 4

5. Natural Background Radiation: Cosmic • Everyone is inevitably exposed • Sources: • Cosmic • Terrestrial • Internal • Cosmic • From sources external to the earth, mainly the sun • Exposure depends on latitude and altitude • At 70deg latitude and sea level, dose rate from cosmic rays measures about 28 mrem/year Module 4: Protection Against Radiation NET 130 Module 4: Protection Against Radiation 5

6. Natural Background Radiation: Terrestrial • In the air: Radon isotopes and their daughters • Products of uranium-238 and thorium-232 decay • In water: Radium-226 and Radium-228 • In the Earth • Common minerals used as building materials • Granite can cause 150 mrem exposure per year • Limestone: 20 mrem/yr • Monazite • Mineral in rock or sand form • Contains thorium -- can produce high background levels • India: about 100000 people receive a dose of 1500 mrem/yr • Brazil: 30000 people receive about 1000 mrem/yr • In some cases, peak dose rates are on the order of 23000 mrem/yr • Uranium: Typical uranium miner receives 5000 mrem/yr • A person living in a wood house is exposed to about 104 mrem/yr of natural background radiation • A person living in a brick and concrete house is exposed to about 145 to 300 mrem/yr Image source: Wikimedia.org (public domain) Module 4: Protection Against Radiation NET 130 Module 4: Protection Against Radiation 6

7. Natural Background Radiation: Internal • Exposure from radioactive materials that are inside the body naturally. • Dose rate typically about 26 mrem/yr • Potassium-40 accounts for about 90% of the total • The average estimated dose rate per person for all types of background radiation combined is approximately 125 mrem/year Module 4: Protection Against Radiation NET 130 Module 4: Protection Against Radiation 7

8. Man-Made Radiation and Legal Limits • Protection from natural background radiation is impossible • Legal limits for protection are specifically for man-made radiation only • Major sources • Medical diagnosis and therapy • X-rays alone: average American is exposed to 50 mrem/yr whole body and up to 1000 mrem/yr local dose • Nuclear weapon testing • Some consumer products • Television sets, cigarettes, and watches contribute a few mrem/yr • Industrial exposure • Legal standards apply only to occupational exposure • People employed in industries where exposure to man-made (non-background) radiation occurs Module 4: Protection Against Radiation NET 130 Module 4: Protection Against Radiation 8

9. Average Annual Exposure Human-Made Radiation Sources: 70 mRem/year Naturally-Occurring Radiation Sources: 300 mRem/year Module 4: Protection Against Radiation

10. Human-Made Sources • Power generation • Nuclear • Coal • Gas • Nuclear weapons testing • Medical • X rays • Chemotherapy • etc • Industrial • Consumer products • Lantern mantles • Cigarettes • etc Module 4: Protection Against Radiation NET 130 Module 4: Protection Against Radiation 10

11. Legal Standards for Rad. Protection: 10CFR • Nuclear Regulatory Commission (NRC) • Licenses and regulates the nuclear industry • Derives authority from Title 10 of the Code of Federal Regulations • 10 CFR presently consists of about 180 parts • Parts that specifically address radiation: • Part 19 (10CFR19): “Notices, Instructions, and Reports to Workers; Inspections” • Part 20 (10CFR20): “Standards for Protection Against Radiation" • Part 100 (10CFR100): “Reactor Site Criteria” • Each licensed facility is legally required to comply with all regulations in Title 10, or be subject to civil penalties. • Every single individual employed in the nuclear industry should understand how he/she is legally protected. Module 4: Protection Against Radiation NET 130 Module 4: Protection Against Radiation 11

12. 10CFR19 • Details workers’ rights and responsibilities in regard to radiation exposure • Establishes requirements concerning radiological working conditions • Outlines options available to workers to ensure compliance • Each licensee (e.g., a nuclear power plant) is required to post conspicuously within the facility the following documents: • Regulations in 10CFR19 and 10CFR20 • The facility's license and all associated amendments • Operating procedures • Notice of violations of radiological working conditions and response from licensee • If posting not practical, may post a description and location of the document • Must also post Form NRC 3, “Notice to Employees in Restricted Areas” frequented by employees Module 4: Protection Against Radiation NET 130 Module 4: Protection Against Radiation 12

13. 10CFR19 • Licensee required to furnish exposure information to any individual upon request • Workers are to be kept informed of the status of radioactive materials or radiation levels in "restricted areas" • All employees are to be trained in health protection procedures involving radiation exposure • NRC may conduct inspections of physical working conditions, activities, and records of the plant. • Employees may be consulted during inspections, or they may report any possible violations to the inspector • In the event that an individual suspects violations of 10CFR regulations, he/she may request an inspection • A worker is permitted to conduct an inspection with the NRC • Complaint must be warranted • Arguments may be presented at an informal hearing instead of an inspection • Name of person making complaint is withheld unless the individual authorizes its release Module 4: Protection Against Radiation NET 130 Module 4: Protection Against Radiation 13

14. 10CFR100 • “Reactor Site Criteria” • Regulations concerning public safety in the event of a major accident • Criteria used in evaluating a site for new nuclear deployment (NND – new reactor construction) • Intended use of reactor • Application of engineering standards to design • Safety features and radioactive release boundaries • Population density and land use • Physical characteristics such as seismology, meteorology, geology, and hydrology • NRC makes an evaluation for each new site and issues construction license if acceptable Module 4: Protection Against Radiation NET 130 Module 4: Protection Against Radiation 14

15. 10CFR100 • Exclusion Area • Area surrounding the reactor • Licensee has authority to determine all activities including exclusion or removal of personnel and property from area • Low Population Zone • Area immediately surrounding Exclusion Area • Contains residents, the total number and density of which are such that there is a reasonable probability that protective measures could be taken on their behalf in the event of a serious accident Low Population Exclusion Reactor Area Zone Module 4: Protection Against Radiation NET 130 Module 4: Protection Against Radiation 15

16. 10CFR20 • Establishes industry standards and routine requirements for protecting plant personnel and the public from radiation hazards. • Maintain radiation exposures and radioactive releases As Low As Reasonably Achievable (ALARA) • Defines terms used in the regulations • Definitions are exact and must be known by operators • See “Vocabulary” section Module 4: Protection Against Radiation NET 130 Module 4: Protection Against Radiation 16

17. Units of Radiation Dose • Occupational Dose • Dose received by an individual during course of employment, in activities/duties that involve exposure to radiation and/or radioactive materials • Exposure Dose • Units of Roentgen (R) • Measurement of the exposure to ionizing radiation equivalent to 2.58 E-4 coulombs/kg of air • Absorbed Dose • Units of Rad or gray (1 gray = 100 rad) • Measurement of the amount of energy deposited (absorbed) in a material, equivalent to 100 ergs/gm. Module 4: Protection Against Radiation NET 130 Module 4: Protection Against Radiation 17

18. Units of Radiation Dose • Dose Equivalent (DE) • DE = (Absorbed Dose) x (QF) • Unit of Roentgen equivalent man (Rem) or Sievert (1 Sv = 100 Rem) • Expresses the effects of all types of radiation on a biologically equivalent basis • Effective Dose Equivalent (EDE) • EDE = S[(DE) x (WT)] • WT = Tissue weighting factor • Estimate of the effect of a localized partial-body exposure on the whole body • For a partial-body dose equivalent, multiply by WT for that particular tissue Module 4: Protection Against Radiation NET 130 Module 4: Protection Against Radiation 18

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20. Units of Radiation Dose • Committed Dose Equivalent (CDE) • Once a radionuclide has been deposited in the body, exposed person is “committed” to the dose resulting from the decay of that radionuclide so long as it is present in the body • Committed dose = dose occurring over the next 50 years (for radiation workers) or 70 years (for general public) after deposition • Committed Effective Dose Equivalent (CEDE) • CEDE = S[(CDE) x (WT)] Module 4: Protection Against Radiation NET 130 Module 4: Protection Against Radiation 20

21. Units of Radiation Dose • Collective Dose • Means for expressing the societal impact of radiation exposures to population groups • Product of # of people exposed and their average dose • Expressed in terms of “person-Sv” or “person-Rem" • Collective dose equivalent • Calculated based upon specific tissues or organs • Collective effective dose equivalent • Calculated in terms of the whole body equivalent Module 4: Protection Against Radiation NET 130 Module 4: Protection Against Radiation 21

22. Units of Radiation Dose • Deep Dose Equivalent (DDE) • Applies to external whole body exposure • Dose equivalent at tissue depth of 1 cm • Shallow Dose Equivalent (SDE) • Applies to the external exposure of the skin or an extremity • Dose equivalent at tissue depth of 0.007 cm averaged over an area of 1 cm2 • Total Effective Dose Equivalent (TEDE) • Sum of the DDE (external exposure) and the CEDE (internal exposure) Module 4: Protection Against Radiation NET 130 Module 4: Protection Against Radiation 22

23. Radiation Exposure Limits • Occupational Exposure • 10CFR20 establishes occupational exposure limitations for individuals in restricted areas • Station Management for local plant also establishes site administrative limits • Minors • Annual occupational dose limits for minors are 10% of the annual dose limits specified for adult workers. Module 4: Protection Against Radiation NET 130 Module 4: Protection Against Radiation 23

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25. Radiation Exposure Limits • General Public • Plants must keep TEDE to individual members of the public below 100 mrem/yr • Planned Special Exposures • Plant may authorize an adult worker to receive doses in addition to the daily occupational dose • Worker cannot exceed annual limit (about 5 Rem TEDE) as specified in 10CFR20 Worker cannot exceed 5x the annual limits during his/her lifetime (5 X 5 = 25 Rem) during the planned special exposure period. Module 4: Protection Against Radiation NET 130 Module 4: Protection Against Radiation 25

26. Radiation Exposure Limits • Whole Body Radiation Exposure • Head, trunk, extremities (hands, forearms, feet, and ankles), active blood forming organs, lens of the eyes, and gonads • Total lifetime whole-body accumulated dose to one individual may not exceed 5N x 1000 mrem TEDE • N = age of the individual in years • Whole-body accumulated dose must be determined by the plant and recorded on Form NRC 4, “Occupational External Radiation Exposure History". • Radiation exposure is always restricted to the lowest value of any applicable limits (ALARA) Module 4: Protection Against Radiation

27. Restricted Areas • Area to which access is limited by the plant for purposes of protecting individuals from risks from exposure to radiation and radioactive materials • Unrestricted Area: any area to which access is not controlled Barrier Fence Unrestricted Area Turbine Building Reactor Building Intermed. Building Aux Bldg Control Building Fuel Bldg Restricted Area Module 4: Protection Against Radiation

28. Radiation/High Radiation Areas • Restricted areas subdivided into: • Radiation Areas • Any area in which radiation levels could result in an individual receiving 5 mREM in 1 hour, at a distance of 30 cm from the source • Typically defined as an area with general area dose rates of 5 – 99 mRem/hr • High Radiation Areas • Any area in which radiation levels could result in an individual receiving 100 mREM in 1 hour, at a distance of 30 cm from the source • Typically defined as an area with general area dose rates of 100 – 999 mREM/hr • 10CFR20 requires these areas to be marked with a radiation symbol plus identifying words • CAUTION: RADIATION AREA • CAUTION: HIGH RADIATION AREA • GRAVE DANGER: VERY HIGH RADIATION AREA Image source: Wikimedia.org (public domain) Module 4: Protection Against Radiation

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31. Radiation/High Radiation Areas • 10CFR20: At any access point to a high radiation area, the following conditions must exist: • Access door must be equipped with a visible or audible alarm that will activate upon opening, warning the entrant • Access door must be locked except when access is required, at which point positive control over each entrant must be maintained. • Access point must be equipped with a control device (automatic shield) that will decrease the dose rate to < 100 mREM/hr upon entry Module 4: Protection Against Radiation

32. Personnel Monitoring Equipment • Form NRC 5, “Current Occupational External Radiation Exposure“ • Plant maintain records of individuals requiring personnel monitoring • NRC 5 maintains the total lifetime accumulated dose to the individual from various types of radiation • Entries are made at least quarterly • Devices worn or carried by workers to measure dose • Must be worn by: • Anyone who enters a restricted area and receives, or is likely to receive in 1 year, a dose in excess of 10% of 10CFR limits • Anyone who enters a high or very high radiation area Image source: Wikipedia.org (public domain) Module 4: Protection Against Radiation

33. Airborne Radioactive Material • Radioactive material that has been dispersed through the atmosphere, in the form of either particles or gases • Can be caused from radioactive particulates, iodine, noble gases, or tritium oxide • Primary concern: potential for deposition inside the body • Ingestion: do not eat/drink inside Radiologically Controlled Areas • Absorption and Cuts: use protective clothing • Inhalation: use engineering controls, cleanliness controls, and respiratory equipment Module 4: Protection Against Radiation

34. 10CFR20: Internal Exposure • To determine amount of radioactive material inside your body and as a baseline to detect any internal contamination in the future, a whole body count is given prior to entry into the reactor containment area • Additional whole body counts are given: • Annually • Anytime internal contamination is expected • Termination of employment • 10CFR20 appendices give specific limits regarding sources of internal exposure • Appendix B, Tables 1, 2, and 3 • Appendix C Module 4: Protection Against Radiation

35. 10CFR 20, Appendix B, Table 1 • Occupational values for radionuclide concentration limits • Determine internal dose due to ingestion and inhalation • Col 1: ALI for oral ingestion • Col 2: ALI for inhalation • Col 3: DAC values • Classes • D: t½ < 10 days • W: t½ = 10 to 100 days • Y: t½ > 100 days Module 4: Protection Against Radiation Source: NRC.gov (public domain)

36. Annual Limit of Intake (ALI) • Max allowable limit for amount of radioactive material taken into the body of an adult worker by inhalation OR ingestion in a year 1 ALI = 5 Rem CEDE (whole body) 1 ALI = 50 Rem CDE (individual organ or tissue) • Example: Thorium-228 • This means that if a worker swallows Th-228 of activity 6E0 = 6 mCi OR inhales Th-228 of activity 1E-2 = 0.01 mCi, he/she has received 1 ALI and cannot be allowed to risk further internal exposure. • Worker would be subject to 5 Rem whole-body equivalent exposure, or 50 Rem local exposure to the specific tissues in contact with the ingested material. Source: NRC.gov (public domain) Module 4: Protection Against Radiation

37. Derived Air Concentration (DAC) • Concentration of a given radionuclide in air which, if breathed for a working year of 2000 hours, results in an intake of one ALI • DAC = Nuclide activity (µCi/ml) ÷ DAC limit from table (µCi/ml) • DAC-hrs = DAC x time (in hours) 2000 DAC-hrs = 1 ALI = 5 Rem CEDE = 50 Rem CDE 1 DAC-hr = 0.0025 Rem = 2.5 mRem = 0.0005 ALI • Example: Th-228 • This means that if a worker breathes air contaminated with Th-228 of activity 4E-12 mCi per mL of air, he/she has received 1 DAC. • If this occurred over a period of one working year (~2000 hrs), the worker has received 1 ALI and cannot be allowed to risk further internal exposure. Source: NRC.gov (public domain) Module 4: Protection Against Radiation

38. 10CFR 20, Appendix B, Table 2 • Radionuclide concentration limits (µCi/ml ) for airborne and liquid effluents released to environment (unrestricted areas) • Col 1: air • Col 2: water • Activity limits are such that continuous inhalation or ingestion over 365 days would result in TEDE of 50 mRem Module 4: Protection Against Radiation Source: NRC.gov (public domain)

39. 10CFR 20, Appendix B, Table 3 • Monthly radionuclide concentration limits (µCi/ml) for releases to sanitary sewer systems Module 4: Protection Against Radiation Source: NRC.gov (public domain)

40. 10CFR 20, Appendix C • Lists activity values of specified radionuclides in units of microcuries (µCi) • An area containing any radioactive material in excess of 10X the listed activity value must have a sign posted: Caution Radioactive Materials • Exceptions • Material is stored less than 8 hours • Area is attended by an individual assuming control to prevent exposure to others Source: NRC.gov (public domain) Module 4: Protection Against Radiation

41. 10CFR20: Notifying the NRC • Certain radiation events must be reported to the NRC within a certain timeframe • Reports of exposure to individuals • Loss of licensed material or other radioactive materials of certain amounts designated below • Etc.. • Depending on the specific risk posed by the event, the notification might have to be: • Immediate (call) • Within 24 hours (call) • Within 30 days (written report) Module 4: Protection Against Radiation

42. External Exposure Control: Time • 3 basic mechanisms of external exposure control: • Time • Distance • Shielding • Dose Rate: Dose per unit time (e.g., mR/hr) • Example: • Compare the total dose received by a person in a 100 mR/hr field for 15 minutes and one who remained there for 45 minutes. Module 4: Protection Against Radiation

43. Exposure vs. Exposure Rate • EXPOSURE: total amount • EXPOSURE RATE: amount per unit time 100 mR HR 1 HOUR 100 mR 2 HOURS 200 mR 400 mR 4 HOURS Expo- sure Rate Stay Time 800 mR 8 HOURS Exposure Module 4: Protection Against Radiation

44. External Exposure Control: Distance • 3 basic mechanisms of external exposure control: • Time • Distance • Shielding • Distance • Radiation beam spreads wider as distance from source increases • Thus penetrating radiation decreases in intensity as distance from source increases • Exposure minimized by maintaining the maximum feasible distance from source • Decrease is function of source’s geometry. Four types: • Point source (simplest) • Line source • Plane source • Tank source Module 4: Protection Against Radiation

45. DISTANCE vs. EXPOSURE 5 ft Radiation Source 4 mR 2 ft 1 ft 25 mR 100 mR DISTANCE EXPOSURE Module 4: Protection Against Radiation

46. Dose Rate Formulas, in terms of Distance • Point Source: Small concentrated source I1d12 = I2d22 (inverse square law) • I = radiation intensity in mR/hr • d = distance from source • Line Source: e.g., a pipe I1d1= I2d2 • Applies only up to d = ½L, where L= length of line source • Beyond that, Inverse Square Law is used Module 4: Protection Against Radiation

47. Point Source Example • Calculate the dose rate at 20 feet if a reading taken at 5 inches is 100 R/hr from a point source. Module 4: Protection Against Radiation

48. Line Source Example • Calculate the dose rate at 10 and 15 feet from a 20 foot pipe if the measured dose rate at five feet is 150 mR/hr. Module 4: Protection Against Radiation

49. External Exposure Control: Shielding • 3 basic mechanisms of external exposure control: • Time • Distance • Shielding • Shield • A material that is placed between a source of radiation and personnel in order to protect individuals from excessive exposure • Used if time and distance are not sufficient or practical • Material type and thickness required is function of type and energy of radiation Module 4: Protection Against Radiation

50. Module 4: Protection Against Radiation