RPT 223 Instructional Resources
Module 11: Determine Worker Dose Using In-Vitro Bioassay
Table of Contents:
Resources Key 2
Module Readings and Homework 2
Primary Scenario “Determine Worker Dose from an Intake of Sr-90 using In Vitro Bioassay” 2
Transfer Scenario “Determine Worker Dose from an Intake of H-3 using In Vitro Bioassay” 2
Primary Scenario “Determine Worker Dose from an Intake of Pu-241 using In Vitro Bioassay” 3
Transfer Scenario “Determine Worker Dose from an Intake of I-131 using In Vitro Bioassay” 3
Module Assessment Items 4
Primary Scenario “Determine Worker Dose from an Intake of Sr-90 using In Vitro Bioassay” 4
Primary Scenario “Determine Worker Dose from an Intake of Pu-241 using In Vitro Bioassay” 4
Transfer Scenario Solutions 5
Transfer Scenario “Determine Worker Dose from an Intake of H-3 using In Vitro Bioassay” 5
Transfer Scenario “Determine Worker Dose from an Intake of I-131 using In Vitro Bioassay 5
ACAD References 7
Resources Key
This refers to: / This reference:ACAD / National Academy for Nuclear Training, Uniform Curriculum Guide for Nuclear Power Plant Technician, Maintenance, and Nonlicensed Operations Personnel Associate Degree Programs, ACAD 08-006.
DOE-SG / Office of Environmental, Safety and Health: Radiological Control Technician Training Site Academic Training Study Guide Phase I, Project Number TRNG-0003
Available at: http://nsedu.rnet.missouri.edu/docshare/. File is located under the Docs/General Curriculum/DOE materials folder.
G. / Gollnick, D. (2006). Basic Radiation Protection Technology, 5th Ed. Pacific Radiation Corporation, Altadena, CA.
NUREG/CF-4884 / Regulatory Guideline published by the Nuclear Regulatory Commission for Interpretation of Bioassay Measurements
Available at: http://nsedu.rnet.missouri.edu/docshare/. File is located under the General Curriculum/Regulations and Standards folder
10CFR20 – Appendix B / Title 10 of the Code of Federal Regulations, Part 10. Appendix B – Annual Limits on Intake, Derived Air Concentrations and Effluent Limits
Available at: http://nsedu.rnet.missouri.edu/docshare/. File is located under the General Curriculum/Regulations and Standards folder
Module Readings and Homework
Primary Scenario “Determine Worker Dose from an Intake of Sr-90 using In Vitro Bioassay”
Core Concept: In-vitro bioassay for determining internal doseHomework (end of chapter)
Readings / Calculation Items / Non-calculation Items
G. Chap 9, 352-360
G. Chap 9, 374-377
DOE-SG Mod 2.04-15 to 2.04-17 / G. Chap 9, #14, 18, S-3,
G. Chap 9, page 377, sample problem 3 / G. Chap 9, #2, 3, 4 ,7, 9, 10
Transfer Scenario “Determine Worker Dose from an Intake of H-3 using In Vitro Bioassay”
Refer to readings and homework for primary scenario above.
Primary Scenario “Determine Worker Dose from an Intake of Pu-241 using In Vitro Bioassay”
Core Concept: Dose from internal alpha emittersHomework (end of chapter)
Readings / Calculation Items / Non-calculation Items
G. Chap 14, 623, 626 / G. Chap 14, #14
Core Concept: Techniques for determining alpha contamination via bioassay
Homework (end of chapter)
Readings / Calculation Items / Non-calculation Items
G. Chap 9, 371-374 / G. Chap 9, #20
Transfer Scenario “Determine Worker Dose from an Intake of I-131 using In Vitro Bioassay”
Refer to readings and homework for primary scenario above.
Module Assessment Items
Note: If instructors wish to increase the difficulty of any item, then we suggest you use it as the basis for an in-class discussion, and / or require students to write an explanation for why a particular choice is correct.
Primary Scenario “Determine Worker Dose from an Intake of Sr-90 using In Vitro Bioassay”
Primary Scenario “Determine Worker Dose from an Intake of Pu-241 using In Vitro Bioassay”
1. A worker in a nuclear power plant has been contaminated around the face with large particles of an isotope that has the following characteristics: Beta decay 100% of the time emitting a 1.45 MeV beta, followed by two gamma-rays at energies of 0.87 and 1.54 MeV. What methods could be used for determining the intake of this isotope? Select ALL that apply.
a. In vivo counting using a whole body counter (Correct)
b. Beta analysis of urine or feces (Correct)
c. Gamma-ray analysis of urine or feces (Correct)
d. Contamination smears from the workers face.
2. In this instance, what would be the preferred method for determining intake?
a. In vivo counting using a whole body counter (Correct)
b. Beta analysis of urine or feces
c. Gamma-ray analysis of urine or feces
d. Contamination smears from the workers face
A worker in a nuclear power plant has been contaminated with 1 AMAD particles of an nuclide that has the following characteristics: beta decay 98% of the time with an Emax of 0.75 MeV and alpha decay 2% of the time. Answer questions 3 and 4 as they pertain to this incident.
3. What methods could be used for determining the intake of this isotope? Select ALL that apply.
a. In vivo counting using a whole body counter
b. Beta analysis of urine or feces (Correct)
c. Gamma-ray analysis of urine or feces
d. Contamination smears from the workers face
e. Alpha spectrometric analysis of urine or feces (Correct)
4. In this instance, what would be the preferred method for determining whole body intake?
a. In vivo counting using a whole body counter
b. Beta or alpha analysis of urine or feces (Correct)
c. Gamma-ray analysis of urine or feces
d. Contamination smears from the workers face
5. The inhalation NALI for 131I is 50 μCi and the DAC is 2 x 10-8 μCi/ml. Which of the following factors are used to convert the nALI to the DAC? Select ALL that apply.
a. The particle size of the iodine compounds that are inhaled
b. The assumed respiration rate for reference man (Correct)
c. The number of working hours in a year (Correct)
d. The retention factor for the inhaled iodine compound
e. DACs are not based upon the ALI
Use the following scenario to answer questions 6 through 8.
The piping in an equipment room at a nuclear power plant has developed a small leak, releasing a fine mist of radioactive water. This is resulting in particulates in the room that, if inhaled, would result in an intake. A work order has been processed which will stop this leak. Based upon measurements of general radiation exposure rates in the room, the air in the room and the estimated time for stopping the leak, the projected CEDE to a worker would be 4 mrem and the TEDE would be 28 mrem. The particulate radioactivity in the air is determined to be 8 times the Derived Air Concentration (DAC). Respiratory protection has been suggested to eliminate this dose, but the room is hot, humid, and poorly lit and the RPT reviewing this work order has suggested that no respiratory protection be use.
6. Concerning the decision to not use respiratory protection, which of the following statements do you believe are true? Select ALL that apply.
a. Internal doses should be avoided at all costs since the radioactive material is introduced into the body.
b. The plant ALARA practices would dictate that this 4 mrem should be avoided if at all possible.
c. Since the external dose is large, more attention could be given to reducing the external dose. (Correct)
d. Since respiratory protection could significantly reduce the TEDE, it should be required.
7. The worker notes that the DAC is 8 times the published value for the radioactive particulate in the room. Although he will only be in the room for an estimated 12 minutes or 0.2 hours, he questions the decision to not wear respiratory protection at this high DAC level. Which of the following RPT responses is correct? Select ALL that apply.
a. The DAC is based upon 2000 hours of exposure in a working year, and the worker will only be exposed for a few minutes (Correct)
b. Assuming the job takes 0.2 hours, the resulting dose would be about 4 mrem (Correct)
c. Although the DAC is 8 times the published value, the risk of personnel injury is too great and the dose will have to be allowed
d. The DAC is only for general guidance and planning and is not used to determine actual dose
8. If the inhaled dose is only due to alpha particles, which of the following statements are correct? Select ALL that apply.
a. Alphas have short range and high quality factors which increases their effective dose when breathed. (Correct)
b. Since the alpha particles are suspended in the air, both the external and internal alpha doses need to be considered.
c. Beta particles (as charged particles like alphas) are only of concern for internal dose.
d. The DAC calculation has already taken into account the quality factor for alphas, so the dose estimate is still correct. (Correct)
Transfer Scenario Solutions
Transfer Scenario “Determine Worker Dose from an Intake of H-3 using In Vitro Bioassay”
The 5-day, cumulative urine sample resulted in 93 nCi of 90Sr in 7500 ml.
This must corrected for the assumed “reference man” urinary output which is 1400 ml per day for males or 7000 ml in 5 days. Thus the activity for calculational purposes is 93 nCi * 7500/7000 = 100 nCi = 0.1 uCi
Since the intake was assumed to be inhalation, and 90Sr is normally soluble, this means the clearance class is D. The retention factor for 90Sr can be found in NUREG/CF-4884, page B-77. The IRF used is the IRF for the midpoint of the 5 day sample, or 2.5 days. This can be interpolated between the 2 day value of 0.132 and the 3 day value of 0.169, resulting in an IRF of 0.15
The intake is thus 0.1 uCi/0.15 = 0.67 uCi.
The nALI for the surface of the bone from 10CFR20 – Appendix B for 90Sr is 20 uCi. Thus the %nALI = 0.67 uCi/20 uCi * 100% = 3.3%
Since an nALI delivers a dose 0f 500 mSv to the bone surface, the dose to the bone surface is 500 mSv * 3.3% = 16.7 mSv.
The sALI for the whole body is also from 10CFR20 – Appendix B for 90Sr and is also 20 uCi. Thus the %sALI = 0.67 uCi/20 uCi * 100% = 3.3%
Since an sALI delivers a dose 0f 50 mSv to the whole body, the dose to the whole body is 50 mSv * 3.3% = 1.67 mSv.
Transfer Scenario “Determine Worker Dose from an Intake of I-131 using In Vitro Bioassay
The 5-day, cumulative urine sample resulted in 0.05 uCi of 131I in 7500 ml.
This must corrected for the assumed “reference man” urinary output for a female which is 1000 ml per day or 5000 ml in 5 days. Thus the activity for calculational purposes is 0.05 uCi * 7500/5000 = 0.075 uCi
Since all iodine intakes are assumed to be inhalation, this means the clearance class is D. The retention factor for iodine can be found in NUREG/CF-4884, page B-103. The IRF used is the IRF for the midpoint of the 5 day sample, or 2.5 days. This can be interpolated between the 2 day value of 0.341 and the 3 day value of 0.329, resulting in an IRF of 0.33
The intake is thus 0.075 uCi/0.33 = 0.227 uCi.
The nALI for the thyroid from 10CFR20 – Appendix B for 131I is 50 uCi. Thus the %nALI = 0.227 uCi/50 uCi * 100% = 0.45%
Since an nALI delivers a dose 0f 500 mSv to the thyroid, the dose to the thyroid is 500 mSv * 0.45% = 2.3 mSv.
The sALI for the whole body is also from 10CFR20 – Appendix B for 131I and is 200 uCi. Thus the %sALI = 0.227 uCi/200 uCi * 100% = 0.11%
Since an sALI delivers a dose 0f 50 mSv to the whole body, the dose to the whole body is 50 mSv * 0.11% = 0.056 mSv.
ACAD References
3.3.3 INTERACTIONS OF RADIATION WITH MATTER
· Describe the processes and characteristics of heavy charged particle (alpha particles, protons) interaction with matter to include:
– Range of alpha particles in air, water, and tissue
3.3.4 BIOLOGICAL EFFECTS AND RISKS ASSOCIATED WITH EXPOSURE TO IONIZING RADIATION
· Describe situations where the risk due to exposure to internally deposited radioactivity would be lower than the increased risks that would result from the use of respiratory protective equipment.
3.3.7 INTERNAL DOSEMETRY
· Describe the means for assessing uptake of radioactivity (bioassays), including
– Whole-body count
– Urinalysis
– Fecal analysis
– Nasal smears
– Airborne radionuclide concentrations
· Discuss the required frequency for performance of bioassays including
– Initial
– Periodic
– Alowing potential uptake
– On termination
3.3.9 CONTAMINATION CONTROLs
· Discuss the reason for having lower limits for alpha contamination.
3.3.10 AIRBORNE RADIOACTIVITY CONTROL
· Describe the procedure for determining the derived air concentration, derived air concentration hours, and annual limit on intake for a worker in an airborne radioactivity area.
Module 10 Determine Worker Dose Using In-Vitro Bioassay
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