1. International Atomic Energy Agency Individual Monitoring ASSESSMENT OF OCCUPATIONAL EXPOSURE DUE EXTERNAL RADIATION SOURCES AND INTAKES OF RADIONUCLIDES

2. International Atomic Energy Agency Individual Monitoring - Unit objectives The objective of this unit is to outline the principles that should govern individual monitoring programmes, including selection of people to be monitoring, monitoring for different radiation types, dosimeter characteristic selection, dosimeter placement, direct and indirect methods for intake measurements. At the completion of the unit, the student should understand basic principles, and be able to determine what type of dosimeter and intake measurement method should be used, and how it should be applied in practice.

3. International Atomic Energy Agency Individual Monitoring – Module Outline l Individual Monitoring Objectives and Principles l Routine Monitoring Programme Design l Task Related Monitoring l Special Monitoring l Dosimeter Selection l Operational Dosimetry Considerations l Methods of Intake Measurement l Use of Material & Individual Specific Data

4. International Atomic Energy Agency Individual Monitoring Objectives and Principles

5. International Atomic Energy Agency Individual monitoring has several objectives Demonstration of good working practices, including adequacy of: u supervision u training u engineering standards

6. International Atomic Energy Agency Individual monitoring objectives The general objective of operational monitoring programmes is the assessment of workplace conditions and individual exposures, u to demonstrate compliance with legal requirements. u Evaluation and development of operating procedures. The assessment of doses due to intakes of radioactive material constitutes an integral part of any radiation protection programme.

7. International Atomic Energy Agency Individual monitoring objectives Provision of information that may help motivate workers to reduce exposure. Provision of information for evaluation of dose following an accident. Data for medical purposes. Provision of data for use in epidemiological studies. Risk-benefit analyses.

8. International Atomic Energy Agency Possible exposure conditions must be considered The nature, frequency and precision of individual monitoring should consider l magnitude of exposure levels due to external radiation and intakes of radionuclides, l possible fluctuations in exposure levels, l likelihood of potential exposures, l magnitude of potential exposures.

9. International Atomic Energy Agency Designation of workplace areas Determination of the need for monitoring begins with designation of workplace areas u Supervised areas u Controlled areas Area designation is based on knowledge of workplace conditions and the potential for worker exposure

10. International Atomic Energy Agency Each worker should be provided with an integrating dosimeter. Where dose rates in the workplace can vary significantly, An additional self-reading pocket dosemeter and/or a warning device should be issued for dose control purposes, A worker should be enrolled in an internal exposure monitoring programme when there is a likelihood of an intake that exceeds a predetermined level Individual monitoring in controlled areas

11. International Atomic Energy Agency Designation of workplace areas Guidance on the designation of areas is given in the Guide on Occupational Exposure If operational procedures are set up controlling normal exposures or to prevent or reduce the possibility of intake, a controlled area will, in general, need to be established

12. International Atomic Energy Agency Individual monitoring is not required in supervised areas A limited number of individual monitors may be used, however, Individual monitoring for the purpose of dose records may be good practice for all workers in a supervised area.

13. International Atomic Energy Agency To monitor or not to monitor? The decision to conduct intake monitoring may not be simple Routine monitoring only for: u Workers in controlled areas u Contamination control and u When significant intakes can be expected. From experience, if the committed effective dose (CED) > 1 mSv is unlikely, u Individual monitoring may be unnecessary u Workplace monitoring may be in order.

14. International Atomic Energy Agency Establishing the need for monitoring of intake Individual or area monitoring need depends on: Amount of radioactive material present Radionuclide(s) involved Physical and chemical form Type of containment used Operations performed and General working conditions

15. International Atomic Energy Agency Establishing the need for monitoring Examples: Workers handling sealed sources, or unsealed sources in reliable containment, may need to be monitored for external exposure, but not necessarily for internal exposure Workers handling radionuclides such as tritium, I-125 or Pu-239 may need monitoring for internal exposure, but not for external exposure

16. International Atomic Energy Agency Situations that may call for monitoring Some situations where routine individual monitoring may be appropriate include: Handling of large quantities of gaseous or volatile materials, e.g. 3 H and its compounds in; u Large scale production processes u Heavy water reactors and u Luminizing; Processing of plutonium and other transuranic elements;

17. International Atomic Energy Agency Situations that may call for monitoring Mining, milling and processing of thorium ores Use of thorium and its compounds – can lead to exposure from radioactive dusts, and thoron (Rn-220) and its progeny); Mining, milling and refining of high grade uranium ores; Processing of natural and slightly enriched uranium, and reactor fuel fabrication;

18. International Atomic Energy Agency Situations that may call for monitoring Bulk production of radioisotopes; Working in mines and other workplaces where radon levels exceed a specified action level; Handling radiopharmaceuticals, such as I-131 for therapy, in large quantities; Reactor maintenance  exposure due to fission and activation products

19. International Atomic Energy Agency Need for monitoring depends on exposure potential * * ISO/TC 85/SC 2/WG13/SG1, Monitoring of Workers Occupationally Exposed to a Risk of Internal Contamination with Radioactive Material

20. International Atomic Energy Agency Individual monitoring is based on exposure potential. l Committed effective dose of  1 mSv in a year? l Consider various factors, including: u The physical form safety factor f fs, u The handling safety factor f hs, u The protection safety factor f ps. l Material form (e.g. volatile liquid, powder) may be taken into account both directly (i.e., f fs ) and indirectly, through the protective measures being taken (i.e. f hs and/or f ps )

21. International Atomic Energy Agency Physical form safety factor f fs Based on the physical and chemical properties of the material being handled. In the majority of cases, should be given a value of 0.01.

22. International Atomic Energy Agency Handling safety factor f hs Based on experience of the operation being performed and the form of the material.

23. International Atomic Energy Agency Handling safety factors, f hs Storage (stock solution)0.01 Very simple wet operations0.1 Normal chemical operations1 Complex wet operations (spills)10 Simple dry operations10 Handling of volatile compounds100 Dry and dusty operations100

24. International Atomic Energy Agency Protection safety factor f ps Based on the use of permanent laboratory protective equipment (e.g. glove box, fume hood). Open bench operations1 Fume hood0.1 Glove box0.01

25. International Atomic Energy Agency Specific radionuclide ‘decision factor’ d j = (A j e(g) j,inh f fs f hs f ps ) / 0.001 A j - cumulative activity of radionuclide j in the workplace over a year, e(g) j,inh - inhalation dose coefficient (Sv/Bq) for inhalation of radionuclide j, 0.001 -conversion from Sv to mSv.

26. International Atomic Energy Agency decision factor Cumulative decision factor l Cumulative decision factor, D, for all radionuclides in the workplace; l If D is 1 or higher, a need for individual monitoring would be indicated, l If D is less than 1, individual monitoring may not be necessary.

27. International Atomic Energy Agency Use of decision factor - an example l Single radionuclide handled on the open bench (f ps = 1). l Normal chemical operations (f hs = 1). l Default value of f fs = 0.01. l For d j = 1, A j = 0.1/e(g) j,inh l I j,inh,L = 0.02/e(g) I,inh l A i = 5 I j,inh,L

28. International Atomic Energy Agency More than one radionuclide in the workplace? Decisions to conduct individual monitoring for the separate radionuclides may be based on the following criteria: All radionuclides for which d j  1 shall be monitored; l When D  1, radionuclides for which d j  0.3 should be monitored; and l Monitoring of radionuclides for which d j is much less than 0.1 is unnecessary.

29. International Atomic Energy Agency Workplace example l Insoluble Pu-239 l Normal chemical operations in a fume hood. l Default AMAD for workplaces of 5 µm. l Values of f fs, f hs, and f ps are taken to be 0.01, 1.0, and 0.1, respectively. l Then:

30. International Atomic Energy Agency Workplace example - 239 Pu l Individual monitoring would be required if A Pu239, the activity of 239 Pu, is greater than: l Otherwise, individual monitoring would not be required.

31. International Atomic Energy Agency Workplace example - 239 Pu + 137 Cs l Cs-137 is handled in the same workplace, l d Pu239 remains the same, and l Decision factor for Cs-137 is given by: l where A Cs137 is the activity of Cs-137 present in the workplace.

32. International Atomic Energy Agency Workplace example - 239 Pu + 137 Cs l If: l Individual monitoring should be performed for any nuclide for which, d j  0.3, for: u Pu-239 if A Pu239 is greater than 36 kBq, u Cs-137 if A Cs137 is greater than 45,000 kBq. l Individual monitoring is unnecessary for Pu- 239 if A Pu239 is much less than 12 kBq and for Cs-137 if A Cs137 is much less than 15,000 kBq.

33. International Atomic Energy Agency Individual vs. Workplace monitoring Individual monitoring may not be feasible for some radionuclides because of: u Radiation type(s) emitted and u Detection sensitivity of monitoring methods In such situations, reliance must be placed on workplace monitoring However, for some radionuclides, e.g. 3 H, individual monitoring may be more sensitive than workplace monitoring

34. International Atomic Energy Agency Monitoring for new operations Individual monitoring is likely to be needed for new operations As experience in the workplace is accumulated, the need for routine individual monitoring should be kept under review Workplace monitoring may be found to be sufficient for radiological protection purposes

35. International Atomic Energy Agency If individual monitoring is required Select or establish monitoring service that: l is approved by the Regulatory Authority, l can provide adequate dosimeter systems to estimate H P (d) at appropriate values of d, l can perform direct or indirect intake measurements and assessment of CED, l is responsible for the accuracy and reliability of the dose assessment, and l can evaluate dosimeters and monitor intake within a short time if an overexposure is indicated.

36. International Atomic Energy Agency Routine Monitoring Programme Design

37. International Atomic Energy Agency Routine Monitoring Programme Design l Monitoring conducted on a fixed schedule for selected workers is routine monitoring. l Basic requirements for u personal dosimeters u intake monitoring and internal dose assessments. l Set of monitoring period, monitoring frequency.

38. International Atomic Energy Agency Basic requirements for personal dosimeters Provide a reliable measurement of the appropriate quantities, i.e. H P (0.07) and H P (10), for almost all practical situations, independent of type, energy and incident angle of the radiation, and with a prescribed overall accuracy.

39. International Atomic Energy Agency Additional criteria are important for the practical use of dosimeters Acceptable cost. Low weight, convenient size and shape. Mechanically strong, waterproof and dust tight. Adaptability to various applications, e.g. measurement of body and extremity dose.

40. International Atomic Energy Agency Additional criteria are important for the practical use of dosimeters Unambiguous identification. Ease of handling. Rapid, trouble-free, unambiguous readout. Suitability for automatic processing. Reliable supplier.

41. International Atomic Energy Agency Internal exposure monitoring limitations Internal exposure monitoring has several limitations. These limitations should be considered in the design of an adequate monitoring programme. Monitoring does not measure directly the committed effective dose to the individual.

42. International Atomic Energy Agency Internal exposure monitoring limitations l Biokinetic models are needed to: u determine intake from excreta sample activity levels, u determine intake from body content, u calculate the committed effective dose from the estimated intake

43. International Atomic Energy Agency Further internal monitoring limitations Measurements may be subject to interference from other radionuclides present in the body: Natural 40 K present naturally Cs-137 from global fallout and Chernobyl accident Uranium naturally present in the diet Radiopharmaceuticals administered for diagnostic or therapeutic purposes

44. International Atomic Energy Agency Interference from “background” radionuclides Establish the radionuclide body content from previous intakes Particularly important when the non- occupational intakes are elevated, e.g. in mining areas with high domestic radon exposure Workers should have bioassay measurements before working with radioactive materials to establish a ‘background’ level.

45. International Atomic Energy Agency Interference from Radiopharmaceuticals Radiopharmaceuticals can interfere with bioassays for some time after administration Duration of interference depends on: u Properties of the agent administered and u Radionuclides present at the workplace Request workers to report administration of radiopharmaceuticals It can then be determined if adequate internal monitoring can be performed

46. International Atomic Energy Agency Frequency of Individual Monitoring BSS: “The nature, frequency and precision of individual monitoring shall be determined with consideration of the magnitude and possible fluctuations of exposure levels and the likelihood and magnitude of potential exposures.” Characterize the workplace to determine the appropriate frequency and type of monitoring!

47. International Atomic Energy Agency Monitoring Period – External Radiation Depends on the exposure situation and working conditions. For external radiation a week to a month is often convenient. More than 1 month may be undesirable, since it is more difficult to determine the reason for an exposure with time.

48. International Atomic Energy Agency Monitoring Period – External Radiation For people who usually do not receive a measurable dose, a 3-month monitoring period may be suitable. Direct reading dosimeters should be worn in addition to the official dosimeter, if daily monitoring is required.

49. International Atomic Energy Agency Individual monitoring frequency – Intake Monitoring Chemical and physical forms (e.g. particle size) determine material behaviour on intake and biokinetics in the body These in turn determine the retention and excretion routes and rates, and hence the type of measurements to be performed and their frequency

50. International Atomic Energy Agency Individual monitoring frequency – Intake Monitoring Identify radionuclides in use and determine their chemical and physical forms Consider possible changes of these forms under accident conditions; u e.g. the release of uranium hexafluoride into the atmosphere results in the production of HF and uranyl fluoride * * Although the emphasis here is on the radiation effects, it should be pointed out, that the HF production means an extreme chemical hazard

51. International Atomic Energy Agency Proper frequency minimizes intake uncertainty Set body content measurement and bioassay sampling schedules to minimize intake estimate uncertainties due to the unknown time of an intake, i.e. u If acute intake occurs immediately after previous assay or just before recent assay u Assuming intake at the monitoring period midpoint under- or overestimates the intake Monitoring period should be short enough that the under- or overestimation  factor of 3

52. International Atomic Energy Agency Determining the monitoring frequency Monitoring period, ΔT, depends on: Radionuclide retention, R(t) Radionuclide clearance, E(t) Sensitivity of the measurement process, i.e. MDA of measurement Acceptable uncertainty Committed effective dose, e(50)

53. International Atomic Energy Agency Determining the monitoring frequency For in vivo measurements e(50)  MDA/R(ΔT)  365/ΔT ≤ 1 mSv/year For in vitro measurements e(50)  MDA/E(ΔT)  365/ΔT ≤ 1 mSv/year Maximum overestimation shouldn’t exceed the factor of 3 (usually it is more restrictive than requirement on underestimation) If exposure occurs at ΔT/2, it means; R(1)/R(ΔT/2) ≤ 3 E(1)/E(ΔT/2) ≤ 3

54. International Atomic Energy Agency Recommended maximum time intervals for routine monitoring

55. International Atomic Energy Agency Suggested maximum time intervals for routine monitoring for uranium compounds

56. International Atomic Energy Agency Suggested maximum time intervals for routine monitoring for actinide compounds

57. International Atomic Energy Agency Recommended monitoring interval tolerances Unreasonable to expect bioassay measurements to be preformed on exact schedule Monitoring interval - DaysTolerance - Days 15  2 30  4 60  7 90  14 180  30 365  30

58. International Atomic Energy Agency Schedule to avoid missing an intake Schedule monitoring to ensure an intake above a predetermined level is not ‘missed’ Intake could be missed if, u As a result of clearance, u Body content or daily excretion declines to a level below the minimum significant activity of the measurement during the time between intake and measurement

59. International Atomic Energy Agency Schedule to avoid missing an intake m(t) - Fraction of an intake in the body (direct measurement) or being excreted from the body (indirect measurement), depends on: Physical half-life Biokinetics of the radionuclide, and The time since intake

60. International Atomic Energy Agency Schedule to avoid missing an intake An intake I and the resulting committed effective dose E(50) would be missed if, I  m(t) is less than the MSA* Monitoring frequency should be set so that intakes corresponding to more than 5% of the annual dose limit are not missed. * Minimum Significant Activity

61. International Atomic Energy Agency Monitoring frequency depends on sensitivity Monitoring frequency is largely driven by the sensitivity of the measurement technique Measurement techniques should be as sensitive as possible However, associated costs related to u Most sensitive techniques u Frequent monitoring measurements should be balanced against risk of doses are underestimated or missed

62. International Atomic Energy Agency Additional methods for better sensitivity Measurement method and frequency should detect intakes  a specified dose limit fraction If goal cannot be realized because of: u Lack of analytical sensitivity u Unacceptably long counting times u Short sampling intervals required for excreta collection Additional methods – e.g. improved workplace monitoring and personal air sampling - should be used for adequate worker protection

63. International Atomic Energy Agency Internal exposure monitoring limitations - Timing of measurements Results for the estimation of chronic intakes can depend on when the monitoring is done If radionuclides have a significant early clearance, difference between pre- and post- weekend measurements may be significant These should be reviewed individually if chronic exposure is possible

64. International Atomic Energy Agency Internal exposure monitoring limitations - Timing of measurements If nuclides have long effective half-lives, u Amount present in the body and u Amount excreted depend on the number of years for which the worker has been exposed These amounts may increase with exposure Retained activity from previous years’ intakes should generally be taken to be part of the background for the current year

65. International Atomic Energy Agency Task Related Monitoring

66. International Atomic Energy Agency Task related monitoring Not routine, i.e. it is not regularly scheduled Conducted to provide information about a particular operation, and give a basis for decisions on the conduct of the operation Useful when short term procedure conditions would be unsatisfactory for long term use Usually conducted the same as routine monitoring, unless the circumstances of the operation dictate otherwise

67. International Atomic Energy Agency Special Monitoring

68. International Atomic Energy Agency Special monitoring May be necessary as a result of: u Known or suspected exposures u An unusual incident, e.g. loss of containment of radioactive materials as indicated by an air or surface sample, or u Following an accident Usually prompted by a result of a routine bioassay measurement exceeding the derived investigation level. It may also result from occasional samples such as nose blows, swipes or others

69. International Atomic Energy Agency Special monitoring Measurement techniques for special monitoring usually the same as routine measurement However, improved sensitivity or a faster processing time may be needed Advise the laboratory that the sample analysis or the direct measurement has priority over routine measurements Inform the laboratory that samples may have a higher than normal level of activity Necessary precautions may be taken to prevent contamination of other samples

70. International Atomic Energy Agency Recommended methods for special monitoring after inhalation Legend** Recommended* Supplementary NB: Nose blow EA: Expired air WB: Whole body Th: Thyroid

71. International Atomic Energy Agency Recommended methods for special monitoring after inhalation

72. International Atomic Energy Agency Recommended methods for special monitoring after inhalation LegendNB: Nose blowEA: Expired air

73. International Atomic Energy Agency Dosimeter Selection

74. International Atomic Energy Agency Dosimeter selection If the type and dose rate levels in penetrating radiation fields are known, it is usually sufficient to use one type of dosimeter. The primary dosimeter should provide an estimate of the effective dose by assessment of H P (10).

75. International Atomic Energy Agency The following types of dosimeters may be used: Photon dosimeters only for H P (10), Discriminating photon dosimeters giving H P (10), and an indication of radiation type and effective energy, and detection of high energy electrons. Film badge holderPanasonicHarshaw

76. International Atomic Energy Agency The following types of dosimeters may be used: Beta-photon dosimeters giving information on the dose equivalents H P (0.07) and H P (10), Extremity dosimeters for beta-photon radiation, or photon radiation only giving information on H P (0.07), and Neutron dosimeters for H P (10).

77. International Atomic Energy Agency Dosimeter selection l When beta radiation is unimportant, a one- element dosimeter is adequate in most situations if irradiation of the body is more or less homogeneous. l Without correction, it will overestimate the dose equivalent to most organs and tissues. l One-element TLD or phosphate glass dosimeters can be used over a wide energy range if they have only small energy dependence.

78. International Atomic Energy Agency Beta dosimeter selection l If betas may contribute significantly to the radiation field, discriminating dosimeters should be used. l When betas dominate, beta-photon dosimeters should be used. l Only weakly penetrating beta radiation needs a thin detector, with filters 7 mg/cm 2 thick tissue substitute.

79. International Atomic Energy Agency Personal dosimeters for photons and betas Procedures to correct for energy and angular dependence of the dosimeter reading: u Filters (absorbers) and radiators in front of the detector for energy compensation. u Indication of radiation quality using, for instance, ratio of two detectors behind filters with different energy response. u Simulation of the required energy dependence by combining detectors with different response functions.

80. International Atomic Energy Agency Monitoring of extremity dose l When the extremity doses will be much greater than the whole body dose, extremity dosimeters should be worn. l The dosimeter should be worn on the extremity where the dose is expected to have its highest value. l Usually extremity monitoring is used for the hand and, in particular, the finger tips. l An extremity dosimeter should estimate H P (0.07).

81. International Atomic Energy Agency Extremity monitoring l A simple, one element TLD may be sufficient. l Should be placed on the most highly exposed finger facing the source. l For low penetrating beta radiation, u the detector should be thin, and u filtered by a tissue equivalent material so that the dose at a nominal depth of 7 mg/cm 2 can be assessed u measurement in the range 5 to 10 mg/cm 2 would suffice

82. International Atomic Energy Agency l In most work situations a single, basic dosimeter worn on the body can be used to estimate of H P (10) for electrons and photons. l In highly inhomogeneous radiation fields, the maximum value of average dose over 1 cm 2 should be assessed. Monitoring for strongly penetrating radiation - Electrons and Photons

83. International Atomic Energy Agency Monitoring for strongly penetrating radiation - Electrons and Photons When the worker's doses are at or near the dose limits, it may be worthwhile to obtain additional information about the radiation conditions, e.g. u from measurements at the workplace or u by using discriminating dosimeters, u a better estimate of effective dose can be made

84. International Atomic Energy Agency Monitoring for strongly penetrating radiation - Neutrons l Principles of individual monitoring for neutrons are the same as for photons and electrons. l No single, simple type can provide adequate neutron dose information over the full neutron energy range. l It may be necessary to use more than one type of neutron dosimeter.

85. International Atomic Energy Agency Monitoring for strongly penetrating radiation - Neutrons l Neutron to gamma ratios vary by two orders of magnitude in some neutron fields. l Neutron effective dose not usually be determined from gamma doses by assuming a constant workplace factor.

86. International Atomic Energy Agency Personal neutron dosimeters No single neutron dosimeter currently meets personal dosimetry needs at all workplaces. Calibrations that take into account the conditions and characteristics of the workplace may be necessary.

87. International Atomic Energy Agency Personal neutron dosimeters Application of a combined dosimeter system, together with some knowledge of workplace characteristics will normally be suitable for neutron monitoring, e.g. l Albedo techniques for low energy neutrons, and l Solid state track detectors for high energy neutrons

88. International Atomic Energy Agency Operational Dosimetry Considerations

89. International Atomic Energy Agency Dosimeter placement The dosimeter should be placed in a position representative of the most highly exposed part of the surface of the torso. – Normally on the front of the body

90. International Atomic Energy Agency Dosimeter placement Body locations representing skin and whole body are usually not the same. When fields are highly non-uniform, additional dosimeters on other parts of the body may be useful.

91. International Atomic Energy Agency Dosimeter placement For weakly penetrating radiation and extremity monitoring, other dosimeters are needed to estimate H P (0.07). Additional dosimeters will be needed if doses may approach 3/10 of the dose equivalent limits.

92. International Atomic Energy Agency Dosimeter placement In special situations (ex. medical radiology where protective clothing such as lead aprons are used), more than one dosimeter may be used: u one under the protective apron, and u one on unshielded parts of the body to provide information on the exposure to the unshielded part of the body (skin, eye, etc).

93. International Atomic Energy Agency Weakly penetrating radiation Skin will often be exposed to a mixture of weakly and strongly penetrating radiation. An estimate of the skin dose is necessary for both types of radiation together. For weak beta radiation (< 0.5 MeV) the same degree of difficulty in measurement exists as for neutrons. H P (0.07) is used to assess skin doses averaged over 1 cm 2 for practical radiological protection

94. International Atomic Energy Agency Weakly penetrating radiation When protective clothing is worn, the dosimeter should be worn at the position where the skin is likely to be most seriously exposed (i.e. at the unprotected part of the body). If the exposure is inhomogeneous, it may be necessary to use more than one dosimeter. The maximum value of the measurements averaged over 1 cm 2 should be used as representative of H P (0.07).

95. International Atomic Energy Agency Exposure to the lens of the eye H P (3) can be assessed from the indication of H P (10) and H P (0.07). Dosimeters used for this purpose should be worn near the eyes (e.g. on the forehead or on a cap). If H P (10) and H P (0.07) are below the relevant dose limits, the value of H P (3) will nearly always be below the dose limit for the lens of the eye (150 mSv).

96. International Atomic Energy Agency Operational monitoring with personnel dosimeters l Supplementary dosimeters may be needed to detect short-term changes in the working radiation area. u direct reading pen dosimeters u active warning pocket dosimeters l Most warning instruments use GM- counters or silicone diode detectors for photons above 30 keV and 20 keV.

97. International Atomic Energy Agency Methods of Intake Measurement

98. International Atomic Energy Agency Individual monitoring methods Individual monitoring for intakes consists of sequential measurements done by: Direct methods u Whole body counting u Organ counting (e.g. thyroid or lung monitoring) Indirect methods u Analysis of samples of excreta u Analysis of selected body fluids or tissues u Personal air samplers is also used

99. International Atomic Energy Agency Individual monitoring limitations l The analytical methods used for individual monitoring sometimes do not have adequate sensitivity to detect the activity levels of interest, therefore u A system of workplace and personnel monitoring may be needed to determine radionuclide intakes u Fixed or personal air samplers (PASs) may be used to determine the airborne concentrations of radioactive material

100. International Atomic Energy Agency Workplace monitoring Workplace monitoring is used in many situations involving radionuclide exposure May be used to demonstrate satisfactory working conditions or where individual monitoring may not be sufficient May be appropriate when contamination levels are low, for example in a research laboratory using small quantities of radioactive tracers

101. International Atomic Energy Agency Direct vs. Indirect measurements Radionuclide intake can be determined by either direct or indirect measurement methods Direct measurement of photons is also referred to as body activity measurements, whole body monitoring or whole body counting Indirect measurements include activity in either biological or physical samples Each type has advantages and disadvantages The selection of one over another depends on the nature of the radiation to be measured

102. International Atomic Energy Agency Direct measurements Direct measurements: u Rapid u Convenient u Can estimate activity in the whole body or a defined part of the body u Less dependent on biokinetic models than indirect monitoring

103. International Atomic Energy Agency Direct measurements Direct methods are useful only for those radionuclides which emit photons: u Of sufficient energy, and u In sufficient numbers, u To escape from the body and u Be measured by an external detector Direct measurements are particularly useful for fission and activation products

104. International Atomic Energy Agency Direct measurements - Limitations Radionuclides which do not emit energetic photons (e.g. 3 H, 14 C, 90 Sr- 90 Y) can usually be measured only by indirect methods Pu-239 emits weak x-rays and may be measured by either method Some higher energy beta emitters, e.g. 32 P or 90 Sr -90 Y, can sometimes be measured ‘directly’ via the bremsstrahlung produced These measurements have a relatively high minimum detectable activities and are not usually employed for routine monitoring

105. International Atomic Energy Agency Direct measurements May have greater calibration uncertainties, especially for low energy photon emitters May require the worker to be removed from work involving radiation exposure for the period over which the retention characteristics are measured Often need special, well shielded, and expensive facilities and equipment.

106. International Atomic Energy Agency Direct measurements Useful in qualitative and quantitative determinations of radionuclides Can assist in identifying the mode of intake by determining the distribution of activity Sequential measurements can reveal activity redistribution and give information about the total body retention and biokinetics

107. International Atomic Energy Agency Indirect measurements Generally interfere less with workers duties However, require access to a radiochemical analytical laboratory Analytical laboratory may also be used for measuring environmental samples Perform high level (e.g. reactor water chemistry) and low level (e.g. bioassay or environmental samples) work in separate laboratories

108. International Atomic Energy Agency Indirect measurements - Excreta Excreta measurements determine the rate of loss of radioactive materials from the body by a particular route Must be related to intake or body content by a biokinetic model Radiochemical analyses  low detection levels  sensitive detection of body activity

109. International Atomic Energy Agency Indirect measurements – Air samples Can be difficult to interpret - air concentration may not represent breathing zone Personal air sampler (PAS) placed on the worker’s lapel or protective headgear can collect more representative samples Sample comprising only a few particles still a problem Air concentrations * breathing rates * measured exposure times  estimated intake

110. International Atomic Energy Agency Indirect measurements – Air samples Use of PASs only estimates intake Cannot be used to refine a dose estimate based on individual retention characteristics PAS measurements cannot be repeated Can provide intake estimates for nuclides such as 14 C (particulate), 239 Pu, 232 Th and 235 U, when other methods may have insufficient sensitivity Interpretation depends on the dose coefficients and the derived air concentration (DAC)

111. International Atomic Energy Agency Particles size is important Particle size influences deposition of inhaled particulates in the respiratory tract Correct interpretation of bioassay and dose assessment depends on particle size data Determine airborne particle size distribution using cascade impactors or other methods BB bb Al ET 2 0.1110100 AMAD (  m) 100 10 1 0.1 0.01 Regional deposition (%) ET 1

112. International Atomic Energy Agency Particles size is important Measurements should, at least, include the concentration of the respirable fraction Some models for interpreting PAS results discriminate against non-respirable particles Dose assessment improves with more site and material specific information

113. International Atomic Energy Agency AMAD (activity median aerodynamic diameter) The aerodynamic diameter of an airborne particle is the diameter that a sphere of unit density would need to have in order to have the same terminal velocity when settling in air as the particle of interest The value of aerodynamic diameter such that 50% of the airborne activity in a specified aerosol is associated with particles smaller than the AMAD and 50% of the activity is associated with particles larger than the AMAD

114. International Atomic Energy Agency Determination of committed effective dose Measurements are used to determine intake The intake, multiplied by the dose coefficient, gives an estimate of committed effective dose Dose coefficients have been calculated by the ICRP and are given in the BSS In some situations, direct measurements may be used to determine whole body or individual organ dose rates directly

115. International Atomic Energy Agency DOSE COEFFICIENTS FOR SELECTED RADIONUCLIDES Radionuclide InhalationIngestion Type /form (a) e(g)inh (Sv/Bq) f1e(g)ing (Sv/Bq) AMAD = 1μmAMAD = 5μm H-3HTO (c)1.8 E-11(b)11.8 E-11 OBT4.1 E-11(b)14.2 E-11 Gas1.8 E-15(b) C-14Vapour5.8 E-10(b)15.8 E-10 CO 2 6.2 E-12(b) CO8.0 E-13(b) P-32F8.0 E-101.1 E-090.82.3 E-10 M3.2 E-092.9 E-09 Fe-55F7.7 E-109.2 E-100.13.3 E-10 M3.7 E-103.3 E-10 Fe-59F2.2 E-093.0 E-090.11.8 E-09 M3.5 E-093.2 E-09 Co-60M9.6 E-097.1 E-090.13.4 E-09 S2.9 E-081.7 E-080.052.5 E-09 Sr-85F3.9 E-105.6 E-100.35.6 E-10 S7.7 E-106.4 E-100.013.3 E-10

116. International Atomic Energy Agency Measurement detection limits Measurement methods have limits of detection arising from: u Naturally occurring radioactive materials u Statistical fluctuations in counting rates, and u Factors related to sample preparation and analysis Minimum significant activity (MSA) and minimum detectable activity (MDA)will be discussed in another unit

117. International Atomic Energy Agency Use of Material and Individual Specific Data

118. International Atomic Energy Agency Biokinetic models Biokinetic models for most radionuclides u Developed by the ICRP u Use reference parameter values u Are based on Reference Man data, and u Observed radionuclide behaviour in humans and animals Have been developed for defined chemical forms of radionuclides, and Are generally used for planning purposes

119. International Atomic Energy Agency Biokinetic models Characterize particular workplace conditions to determine forms actually present In some circumstances, the chemical or physical forms of the radionuclides will not correspond to the reference biokinetic models Then, material specific models may need to be developed

120. International Atomic Energy Agency Specific biokinetic models For small intakes, i.e. a few per cent of the dose limit, reference models are probably good enough If the intake estimate  6 mSv, model parameters for; Specific material(s), and Individual(s) may be needed for better estimate of the committed effective dose

121. International Atomic Energy Agency Specific biokinetic models Specific models can be developed from sequential direct and indirect measurements of the exposed workers Analysis of workplace air and surface contamination samples can also assist in the interpretation of bioassay measurements Example - Measure 241 Am/ 239,240 Pu from direct lung measurement of 241 Am to assess plutonium intakes or inhaled particle solubility

122. International Atomic Energy Agency Need for specific information Common example – aerosol particle size a worker would likely inhale differs significantly from ICRP 5 μm AMAD default value Fractions of inhaled materials deposited in various regions of the respiratory tract would have to be determined from the ICRP respiratory tract model, and An appropriate dose coefficient calculated

123. International Atomic Energy Agency Need for specific information More specific information may also be needed on the material solubility characteristics Can be obtained from experimental studies in animals or by in vitro solubility studies Retrospective determination of particle characteristics may be difficult Consideration should be given to obtaining material specific information when setting up worker monitoring programmes

124. International Atomic Energy Agency Individual variability There are differences between individuals in excretion rates and other biokinetic parameters for the same intake Individual variability may be more significant than the differences between generic and individual specific biokinetic models Excreta sample collection periods should be sufficiently long to reduce this variability, e.g. 24 hours for urine and 72 hours for faeces Use of individual specific model parameters should be rare under routine circumstances.

125. International Atomic Energy Agency References FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS, INTERNATIONAL ATOMIC ENERGY AGENCY, INTERNATIONAL LABOUR ORGANISATION, OECD NUCLEAR ENERGY AGENCY, PAN AMERICAN HEALTH ORGANIZATION, WORLD HEALTH ORGANIZATION, International Basic Safety Standards for Protection against Ionizing Radiation and for the Safety of Radiation Sources, Safety Series No. 115, IAEA, Vienna (1996). INTERNATIONAL ATOMIC ENERGY AGENCY, INTERNATIONAL LABOUR OFFICE, Occupational Radiation Protection, Safety Standards Series No. RS-G-1.1, IAEA, Vienna (1999). INTERNATIONAL ATOMIC ENERGY AGENCY, Assessment of Occupational Exposure Due to Intakes of Radionuclides, Safety Guide No. RS-G-1.2, ISBN 92-0-101999-8 (1999). INTERNATIONAL ATOMIC ENERGY AGENCY, Assessment of Occupational Exposure Due to External Sources of Radiation, Safety Guide RS-G-1.3 (1999). INTERNATIONAL ATOMIC ENERGY AGENCY, Neutron Monitoring for Radiological Protection, Technical Reports Series No. 252, IAEA, Vienna (1985). INTERNATIONAL COMMISSION ON RADIATION UNITS AND MEASUREMENTS, Measurement of Dose Equivalents Resulting from External Photon and Electron Radiations, Report No. 47, ICRU, Bethesda, MD (1992). INTERNATIONAL COMMISSION ON RADIATION UNITS AND MEASUREMENTS, Quantities and Units in Radiation Protection Dosimetry, Report No. 51, ICRU, Bethesda, MD (1993).

126. International Atomic Energy Agency References INTERNATIONAL COMMISSION ON RADIOLOGICAL PROTECTION, General Principles for the Radiation Protection of Workers, Publication No. 75, Pergamon Press, Oxford and New York (1997). NATIONAL COUNCIL ON RADIATION PROTECTION MEASUREMENTS, Use of Personal Monitors to Estimate Effective Dose Equivalent and Effective Dose to Workers for External Exposure to Low-LET Radiations, Report No. 122, NCRP, Washington, DC (1995). INTERNATIONAL ATOMIC ENERGY AGENCY, Direct Methods for Measuring Radionuclides in the Human Body, Safety Series No. 114, IAEA, Vienna (1996). INTERNATIONAL ATOMIC ENERGY AGENCY, Indirect Methods for Assessing Intakes of Radionuclides Causing Occupational Exposure, Safety Guide, Safety Reports Series No. 18, ISBN 92-0-100600-4 (2000). INTERNATIONAL COMMISSION ON RADIATION UNITS AND MEASUREMENTS, Direct Determination of the Body Content Of Radionuclides, ICRU Report 69, Journal of the ICRU Volume 3, No 1, (2003). INTERNATIONAL COMMISSION ON RADIOLOGICAL PROTECTION, Individual Monitoring for Internal Exposure of Workers: Replacement of ICRP Publication 54, ICRP Publication 78, Annals of the ICRP 27(3-4), Pergamon Press, Oxford (1997).