WPM-D - External Dosimetry Orange A 14:30 - 16:30
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| Chair(s): Chris Passmore
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WPM-D.1
14:30 Comparison of Extremity Dose for Nuclear Medicine Workers using Finger Stall and TLD Ring Dosimeters CN Passmore*, Landauer
; M Kirr, Landauer
Abstract: Nuclear medicine workers are exposed to a large extremity dose gradient from the base of the wrist to the fingertip. ORAMED (Optimization of RAdiation protection for MEDical staff) project indicated that the extremity dose can vary as much as a factor of 6 from the base to the fingertip.
In this paper extremity doses will be compared for a group of nuclear medicine workers wearing both Public Health England finger stalls and Landauer TLD Ring dosimeters. The participants in this study wore both dosimeters while working exclusively with Technetium99m and Iodine 123. The data set will follow 7 workers over a period of 5 years. The maximum extremity dose will be assessed in accordance with regulatory guidance and a comparison between the dosimeters worn at the fingertip and base will be determined.
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WPM-D.2
14:45 Comparison of Lens of the Eye Doses Determined Using Collar and Eye Dosimeters M Kirr*, Landauer
; C Passmore, Landauer
Abstract: Occupational doses to the lens of the eye (Hp(3)) has received a lot of attention in the past years as more scientific evidence regarding the effects of radiation on the eye was identified. In the medical arena characterized by uniform radiation fields, a popular method for lens of the eye estimation is to use a whole body dosimeter worn at the collar and calibrated using a whole body phantom. In this case the dose to the lens of eye would be calculated as a interpolation of Hp(10) and Hp(0.07) or direct calculation of Hp(3). Another category of workers are the ones performing procedures in non-uniform radiation fields as fluoroscopically guided procedures, interventional cardiology and radiology. Medical workers in these occupations work close to the radiation field, wear a lead aprons, and are exposed to scattered radiation. For these types of workers estimating the lens of the eye dose based on the collar dosimeter is not the most accurate method and the recommendation of the Radiation Safety Professionals is to wear dosimeters close to eye and calibrated using cylindrical phantom. Large database of workers who wore both whole body dosimeter at the collar while wearing a lens of eye dosimeter located in close proximity to the eye was studied to understand the pattern and differences between the two ways of lens of the eye dose estimation in real life applications.
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WPM-D.3
15:00 Improving Reproducibility in TLD Dosimetry Systems MJ Ramlo*, Thermo Fisher Scientific
Abstract: As TLD dosimetry, whole-body systems grow, some approaching a million dosimeters and dozens of readers, reproducibility between readers can become an ever-increasing concern. Over a few years’ effort a task-team, employing Design of Experiments techniques tested many factors suspected of introducing variability into readings. Numerous factors were identified as non-contributors, other factors were found to subtly affect reproducibility, and a limited couple were found to be very impactful.
The work presented here, shows how one key factor was investigated. The work led to a design change which improves reproducibility, reducing its value by as much as one half.
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WPM-D.4
15:45 An Introduction to Federal Guidance Report No. 15 MA Boyd, U.S. EPA
; J Nagata*, U.S. EPA; Boyd
Abstract: The U.S. Environmental Protection Agency's (EPA) Federal Guidance Report No. 15 (FGR 15) provides age-specific external dose coefficients for over 1200 radionuclides. Dose rate coefficients are provided for submersion in a contaminated atmospheric cloud (air submersion), immersion in contaminated water (water immersion), and exposure to contamination on or below the ground surface (ground exposure). FGR 15 allows the calculation of effective dose for reference individuals at ages newborn, 1, 5, 10, 15 years and adult. The dose coefficients incorporate the radiation and tissue weighting factors provided in the latest general recommendations of the International Commission on Radiological Protection (ICRP) in their Publication 103. FGR 15 does not replace its predecessor, FGR 12, which provides external dose coefficients for a reference adult using the definition of effective dose equivalent from ICRP Publication 26, since some U.S. regulations specify the older definition. Improvements in methodology and comparisons between FGR 12 and 15 are provided. Age-specific dose coefficients in FGR 15 improve the ability to do special assessments, particularly in exceptional situations where infants and children may be exposed to external radiation at doses of concern. EPA expects to also incorporate age-specific organ absorbed doses from FGR 15 into its calculation of new excess cancer risk coefficients.
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WPM-D.5
16:00 Regional Intercomparison on Hp(10) Measurements Using TLD and OSL M Arib*, King Faisal Specialist Hospital and Research Centre
; O Noor, King Faisal Specialist Hospital and Research Centre; B Moftah, King Faisal Specialist Hospital and Research Centre; i Algain, King Faisal Specialist Hospital and Research Centre; F Mayhoub, King Faisal Specialist Hospital and Research Centre; H Alhumaidan, King Faisal Specialist Hospital and Research Centre; M Alkudaibi, King Faisal Specialist Hospital and Research Centre; S Alshora, King Faisal Specialist Hospital and Research Centre; N Aledan, King Faisal Specialist Hospital and Research Centre
Abstract: Personal dosimeters are widely used in many countries where occupational exposure to ionizing radiation can occur, e.g. medical applications, education and research institutes, nuclear plants etc. Adequate radiation protection of workers is essential for the safe and acceptable use of any ionizing radiation. International Regulations recommend the organisation of international intercomparisons relating to radiation dose measurements for the control of occupational and other exposures.
In the framework of the IAEA TC regional project RAS6084, an intercomparison on measurements of the quantity personal dose equivalent Hp(10) in photon fields in the ARASIA Region was realized to which participated eight individual monitoring services from Jordan, Kuwait, Lebanon, Oman, Saudi Arabia and United Arab Emirates and Yemen). The SSDL of Saudi Arabia acted as the irradiating SSDL.
The intercomparison aimed at testing the dosimetry systems. For this purpose, the following irradiations were performed: Linearity test using Cs-137 irradiations at doses lying between 0.5 mSv to 10 mSv; Irradiation to 2 mSv using N-60, N-80 and N-150 X-rays for energy response and irradiation in Cs-137 with angular incidences of 0°, 45° and 60° for angular dependence. In addition, irradiation of the dosimeters was performed in mixed photon beams using different irradiation conditions (ISO Narrow beam N-150 (150 kV) and 137Cs gamma beam) simulating real workplace conditions and at a high dose of 100 mSv. This is a blind test to check the ability of the participants to measure doses in real working conditions and in accidental irradiation.
The results showed that all the participants have their results within the trumpet curve and therefore acceptable. The mean ratio of the Hp(10)measured over Hp(10)true was 1.035 ± 0.200 for all the results. This ratio is 1.026 ± 0.195 for linearity, 1.016 ± 0.161 for energy response, 0.997 ± 0.213 for angular response and 1.060 ± 0.196 for the Blind Test.
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WPM-D.6
16:15 Dose Rate Simulations of Uranium Ore Samples in the Grand Canyon Museum Collection CE Samuels*, Georgia Institute of Technology
; JW Inman, Georgia Institute of Technology; NE Hertel, Georgia Institute of Technology
Abstract: In light of the recent allegations that public exposure limits were exceeded at the Grand Canyon Museum Collection, we used Monte Carlo simulations to model exposure due to uranium ore stored in 5-gallon waste buckets. Two scenarios were considered: one in which the container was assumed to be perfectly sealed and one in which all radon was assumed to have escaped the bucket prior to decay. These two extremes should be bounding for the study. Three decay timelines were considered: one in which the uranium was allowed to decay for 30 years, one in which the uranium was allowed to decay for 50 years, and one in which the uranium had reached secular equilibrium with its daughter products. Although the contents of the containers were assumed to be a homogeneous mixture, simulations with packing factors of 50, 75, and 100 percent were also performed to provide insight into the level of self-attenuation of the radiations within the ore. The composition of the ore was based on samples taken from the Orphan Lode Mine.
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