Chapter 12
HRHuman ResourcesTD Training & Development
¾ ICRP-26/30
¾ 10 CFR Part 20, Appendix B, Table 1
H-201 - Health Physics Technology - Slide 1 - International Commission on Radiological Protection (ICRP) Publications 26 & 30
H-201 - Health Physics Technology - Slide 2 - Objectives
¾ Discuss the concept of the ICRP Reference Man
¾ Demonstrate an understanding of CDE, CEDE, and WT ¾ Discuss the technical bases for internal dose calculations as published in ICRP 30 ¾ Understand the ICRP 30 methods for determining the ALIs and DACs that are used in 10 CFR 20 ¾ Determine CEDE or CDE using DACs and ALIs
H-201 - Health Physics Technology - Slide 3 - ICRP 23: Reference Man
Provides average parameters for the “Reference Man” used in internal dose calculations:
¾ Weighs 70 kg (58 kg for female)
¾ Bth20l/idilihtktiitBreathes 20 l/min doing light work activity
¾ Excretion rates: 1400 ml/day - urine 300 g/day – feces
¾ ICRP 23 Also includes the masses of several important organs used in internal dose calculations
H-201 - Health Physics Technology - Slide 4 - ICRP 26 (1977)
¾ Included recommendations for annual occupational dose limits (adopted by NRC in 10 CFR Part 20)
¾ Introduced the concepts of Effective Dose Equivalent and Committed Dose Equivalent
¾ Included the Quality Factors (Q) used in calculating Dose Equivalent (based on LET)
¾ Includes the Tissue Weighting Factors (wT) used for calculating Effective Dose Equivalent
H-201 - Health Physics Technology - Slide 5 - ICRP 26 Quality Factors
Note: Additional Quality Factors are given for neutrons in 10 CFR 20.1003, which range from 2 – 11, depending on the neutron energy. ICRP 26 Weighting Factors
“The proportion of the risk of stochastic effects resulting from irradiation of that organ or tissue to the total risk of stochastic effects when the whole body is irradiated uniformly.”
Organs wT Gonads 0.25 Breast 0.15 Red Bone Marrow 0.12 * 0.06 for Lung 0.12 each of five Thyroid 0.03 remainder Bone Surfaces 0.03 organs Remainder 0.3*
H-201 - Health Physics Technology - Slide 7 - Weighting Factors ICRP-26, 60, and 103
(1977) (2007) ICRP 30
¾ Provides the mathematical methods for calculating the ALIs and DACs found in Part 20, Appendix B
¾ Provides the technical basis for determining the Dose Conversion Factors (()DCFs) found in FGR 11
¾ Provides the dosimetric models and metabolic data used to calculate Intake Retention Fractions (IRF) found in NUREG/CR-4884
H-201 - Health Physics Technology - Slide 9 - ICRP 30 Dosimetric Models
¾ Model for respiratory system
¾ Model for gastrointestinal tract
¾ MdlfModel for b one
¾ Model for submersion in a radioactive cloud
H-201 - Health Physics Technology - Slide 10 - ICRP 30 Dosimetric Model Example:
GI Tract ICRP-30 GI Tract Model
¾ The primary site of absorption of radioactive materials from the GI tract to body fluids is the small intestine
¾ The paramet er d escribi ng this i s call ed f 1, the fractional uptake from the small intestine to blood
¾ f1 is primarily a function of solubility (chemical form) of the radionuclide inhaled or ingested. The
higher the solubility, the higher the f1
H-201 - Health Physics Technology - Slide 12 - ICRP-30 Model for Organ Dose Source Organ
The organ in which the radionuclide is localized and assumed to be uniformly distributed
H-201 - Health Physics Technology - Slide 14 - Target Organ
Target organs are the organs in the body that are irradiated by the radiations emitted from radionuclides within nearby source organs.
H-201 - Health Physics Technology - Slide 15 - Source and Target Organs
Target and source organ may be different
Example:
Dose to ovaries From liver
H-201 - Health Physics Technology - Slide 16 - Source and Target Organs
Target and source organ may be the same
Example: Dose to liver from liver
H-201 - Health Physics Technology - Slide 17 - Source and Target Organs
Source organ may be enclosed by target organ
Dose to Example: bladder wall from bladder contents
H-201 - Health Physics Technology - Slide 18 - Source and Target Organs
Target organ may be enclosed by source organ
Dose to marrow Example: from bone
H-201 - Health Physics Technology - Slide 19 - Multiple Source Organs
Example: Dose to uterus from stomach and bladder
H-201 - Health Physics Technology - Slide 20 - ICRP 30 Method for Calculating Internal Dose
¾ The dosimetric models in ICRP 30 were used to approximate how different radionuclides move through the body
¾ These models tell us the total number of transformations a radionuclide undergoes in each source organ as it moves through the body
¾ They also tell us the amount of energy that is deposited in target organ from each transformation occurring in a source organ (SEE)
H-201 - Health Physics Technology - Slide 21 - ICRP 30 Method for Calculating Internal Dose ¾ If you know the total number of transformations of a radionuclide in a source organ AND the energy per transformation that is deposited in a target organ, you can determine the dose to that target organ.
¾ To calculate CEDE, you then have to sum the doses to all target organs in the body from all source organs
H-201 - Health Physics Technology - Slide 22 - ICRP-30 Values for Inhaled I-131
(ICRP30-71) ICRP 30 Secondary Limits
¾ ICRP 30 introduced secondary limits that could be used operationally, in addition to the dose limits recommended in ICRP-26.
¾ These limits are the ALIs and DACs that were later publis he d in 10 CFR 20 Appen dix B (more on Appen dix B later…)
¾ ALIs and DACs were derived for common isotopes and chemical compounds using the ICRP-30 models.
¾ ALIs were determined for both the inhalation and ingestion pathways (lung model and GI model).
H-201 - Health Physics Technology - Slide 24 - Annual Limit on Intake (ALI)
¾ The ICRP 30 ALIs were limits on the amount of radioactive material taken into the body of an adult worker. ALIs are given in μCi or Bq.
¾ The ALI i s d efi ned as th e small er val ue of i nt ak e of a given radionuclide that would result in a CEDE of 5 rem or a CDE of 50 rem to any individual tissue or organ.
H-201 - Health Physics Technology - Slide 25 - Stochastic vs. Deterministic ALIs
¾ A large percentage of radionuclides were found to have ALIs that were stochastically based (i.e., 1 ALI = 5 rem CEDE)
¾ However, for some radionuclides, a given tissue would recei ve 50 rem bfbefore th e wh hlole b bdody would receive an effective dose equivalent of 5 rem.
¾ These radionuclides have deterministically based ALIs for that given organ or tissue. In these cases, ICRP printed the limiting organ in the tables of ALIs.
(See ICRP-71)
H-201 - Health Physics Technology - Slide 26 - Derived Air Concentration (DAC)
¾ The derived air concentration (DAC) is the concentration of radioactive material in air which, if breathed doing light work activity over a year, will result in one ALI.
¾ ICRP 30 published DACs for use in calculating inhalation doses and submersion doses
¾ DACs are typically given in μCi/mL or Bq/m3
Note: One year is considered to be 40 hours per week and 50 weeks per year.
H-201 - Health Physics Technology - Slide 27 - Derived Air Concentration (DAC)
The breathing rate for a reference man performing light work is listed as 20 liters per minute in ICRP 23, so the amount of air breathed during a working year is:
(40 h/wk )()x(50 wk/ y)(y)x(20 L/min )()x(60 min/h )()x(1000 ml/L ) = 2.4 x 109 ml/y
Therefore,
DAC (μCi/ml) = ALI (μCi) / 2.4 x 109 ml
H-201 - Health Physics Technology - Slide 28 - 10 CFR 20 Appendix B
H-201 - Health Physics Technology - Slide 29 - Appendix B lists the ALIs and DACs that were derived in ICRP 30 plus a lot more information.
(See page 10CFR20 Appendix B-1) Solubility Class for Inhaled Material
¾ For a radionuclide that is inhaled, we must know the solubility class to select the correct ALI or DAC from 10 CFR 20 Appendix B.
¾ Solubilityyp class depends on the chemical form of the compound, so a radioisotope may have more than one class.
¾ The solubility class is ultimately based upon the clearance of the radionuclide from the pulmonary region of the lung.
H-201 - Health Physics Technology - Slide 31 - Solubility Class for Inhaled Material
¾ Class D has a clearance time of less than 10 days
¾ Class W has a clearance time of from 10 to 100 days
¾ Class Y has a clearance time of ggyreater than 100 days
Note: If the class of the compound is unknown, assume the most conservative case.
H-201 - Health Physics Technology - Slide 32 - Solubility Class for Inhaled Material
¾ The first isotope of a radionuclide in Appendix B will list all the solubility classes for the various chemical compounds of that radionuclide.
¾ Knowinggp the class for a particular chemical form, ,y you then find the ALI or DAC for any other isotope of that radionuclide that has the same chemical form.
H-201 - Health Physics Technology - Slide 33 - Inhalation Class Example
¾ What is the inhalation ALI for Bromine-80m in the form of silver bromide (AgBr)?
¾ From the “see 74mBr” under Bromine-80m, you notice that bromides of silver are class W.
¾ Knowing the class, you then look under the Bromine- 80m listing and find that the ALI is 1E+4 μCi.
Note: Look in the Inhalation column, not the Oral Ingestion listing!
H-201 - Health Physics Technology - Slide 34 - DAC Problem #1
Given the class “W” inhalation ALI for Co-60 is 200 μCi, calculate the DAC and compare your result to that listed in 10 CFR Part 20
H-201 - Health Physics Technology - Slide 35 - Answer to DAC Problem #1
Given the class “W” inhalation ALI for Co-60 is 200 μCi, calculate the DAC and compare your result to that listed in 10 CFR Part 20:
DAC (μCi/ml) = ALI ( μCi)/) / 24x102.4 x 109 ml
DAC (μCi/ml) = 200 μCi / 2.4 x 109 ml
DAC = 8.3 x 10-8 μCi/ml
Compare this result to the value in 10 CFR Part 20!
H-201 - Health Physics Technology - Slide 36 - Exposure in DAC-hours (Stochastic)
If a worker is in a work area with an air concentration of 1 DAC for 2000 works hours, we can say that worker’s exposure is 2000 DAC-hours
From the definition of the DAC, we also know:
2000 DAC-hours = 5 rem if the airborne radionuclide(s) are stochastically based.
Therefore, 1 DAC-hour = 2.5 mrem/DAC-hr
H-201 - Health Physics Technology - Slide 37 - Exposure in DAC-hours (Deterministic)
If that same worker has an exposure of 2000 DAC-hours to a radionuclide that is deterministically based, we know that his total exposure will give him 50 rem to a specific tissue or organ. So in this case,
2000 DAC-hours = 50 rem
So for airborne radionuclide(s) that are deterministically based,
1 DAC-hour = 25 mrem/DAC-hr
H-201 - Health Physics Technology - Slide 38 - TEDE Problem #1
In conducting an inspection, you are to enter an area and observe a work activity for two hours.
The RWP indicates that the general area dose rate is 10 mrem/h and the airborne concentration for a stochastically limiting radionuclide is 0.05 DAC. What is your estimated total dose for this inspection?
H-201 - Health Physics Technology - Slide 39 - TODE/TEDE Problem #2
In conducting an inspection you are to enter an area and observe a work activity for two hours.
The RWP indicates that the general area dose rate is 20 mrem/h and the airborne concentration for I -131 is 1E-8 μCi/ml AND 2E-8 μCi/ml for Cs-137 .
What is your estimated TODE to the thyroid and TEDE for this inspection?
H-201 - Health Physics Technology - Slide 40 - END OF ICRP-26/30 AND 10 CFR PART 20 APPENDIX B
H-201 - Health Physics Technology - Slide 41 - END OF CHAPTER 12
H-201 - Health Physics Technology - Slide 42 -