MAM-C - External Dosimetry Centennial Ballroom 300C 09:30 - 11:30
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| Chair(s): Nolan Hertel
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MAM-C.1
09:30 “Hostages to Compliance”: Optimizing Reasonableness and Implementing Critical Thinking in External Dosimetry CN Passmore*, Passmore Dosimetry Consulting Services
Abstract: On first impression, there is considerably guidance on establishing occupational monitoring for people working with or around radiation. A fundamental component of each radiation regulation provides conditions requiring individual monitoring for external occupational dose. This seems to be a good reasonable guide for health physicists to make decisions on who should be monitored, but in the end large population of workers monitored for external whole-body dose finish the year with no measurable occupational exposure. Why do we end up with so many people with no measurable dose? Are the regulatory requirements too conservative and restrictive on who should be monitored or is our interpretation as health physicist too conservative? Annual occupational radiation exposure reports from various national dose registries indicate 80 - 85% of people monitored have no measurable occupational exposure which could indicate unnecessary monitoring for workers across many industries and occupations. Are health physicists held hostages to compliance or is there a way to achieve compliance by applying more critical thinking? In this presentation, regulatory requirements are presented along with parameters that could impact the initial first impression on determining who should be monitored. In addition, potential approaches determining when monitoring is required will be evaluated and presented. Using these approaches, the health physicist could help optimize the radiation monitoring program and implement a more reasonable approach in making decision on external dosimetry monitoring.
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MAM-C.2
09:45 Radiation exposure during boating activities: towards more realistic modelling and less conservatism KT Griffin, Georgia Institute of Technology
; NE Hertel*, Georgia Institute of Technology
Abstract: Dose rate coefficients for an individual boating on a contaminated body of water are a practical dataset, given that radioactivity may be released into bodies of water through liquid discharges or accidental releases from a nuclear power plant. When calculating dose rate coefficients from external exposure during boating activities, the practice has been to make a conservative estimate by halving coefficients based on immersion in water. However, this general assumption overlooks important differences between the two scenarios – chiefly the distance from the source and the shielding provided by the hull of the boat. To determine the appropriateness of this approximate approach, a realistic boating scenario was modelled using the Monte Carlo N-Particle version 6 (MCNP6) code for a range of monoenergetic gamma emissions within the water, as well as for three common radionuclides found in reactor liquid effluents: Co-60, Cs-137, and Mn-54. Archival blueprints for a 12-foot rowboat were used to create a boat model within MCNP6. The computer software code PIMAL – Phantom wIth Moving Arms and Legs – was used to generate an adult male and female phantom in a seated position within the boat. Dose rate coefficient comparisons were made against reference values taken from the LADTAP II code as well as Federal Guidance Report 15. Differences between reference values currently used to estimate boating dose rate coefficients and those found through the realistic modelling techniques of this work are presented.
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MAM-C.3
10:00 CHARGED PARTICLE CONTRIBUTIONS TO LOCAL SKIN DOSE FROM NEUTRON IRRADIATIONS KG Veinot, Y-12 National Security Complex,
; NE Hertel*, Georgia Institute of Technology; MM Hiller, Independent Consultant; KF Eckerman, Independent Consultant
Abstract: For the preparation of the International Commission on Radiation Units and Measurements (ICRU) Report 95 (Operational Quantities for External Radiation Exposure), the authors performed a series of calculations to obtain the local skin dose due to monoenergetic neutrons. Computations were performed using the radiation transport code MCNP version 6.2 and a two-region slab phantom. In the ICRU report, the local skin dose was tallied at the recommended depth of interest (50 – 100 µm below the skin surface). Additional calculations of dose and charged particle fluences were performed to provide a clearer picture of the buildup of the absorbed dose near the skin surface. These calculations included depth-dose calculations using the slab phantom. This phantom has a surface layer with skin composition followed by the an ICRU tissue slab. As expected these calculations show that recoiling protons are the primary driver of absorbed dose for neutrons below about 10 MeV while at higher energies contributions from heavier charged particles become important in the delivery of absorbed dose. Using these depth-dose calculations, the buildup of the absorbed dose with depth will be presented and compared to absorbed dose estimates by the kerma approximation. These calculations serve to underscore the depths at which the kerma approximation can be used with little error to compute the absorbed dose.
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MAM-C.4
10:15 Thermo Fisher Scientific NetDose Dosimetry Service NVLAP Accreditation PJ LaFrate*, Thermo Fisher Scientific
Abstract: Thermo Fisher Scientific Dosimetry Services recently attained NVLAP accreditation for a new passive-digital personnel dosimeter called NetDose. Incorporating patented technology, this new dosimeter service meets the performance requirements of ANSI N13.11 along with ISO-IEC 17025-2017 quality management system requirements.
NVLAP accreditation is an independent, third party assessment of laboratory technical competence based on ISO/IEC 17025, “General Requirements for the Competence of Testing and Calibration Laboratories.” As part of accreditation approval, an accreditation assessment is performed by peer technical experts which provide greater confidence in a dosimetry provider’s dosimetry measurements. NVLAP accreditation is an NRC requirement for any dosimetry provider that provides dosimetry measurements used for dose-of-record providing additional confidence in their uniformity, accuracy, and traceability. NVLAP accreditation also provides a measure of credibility for ionizing radiation dosimetry service providers.
Here we will present the technical fundamentals of the NetDose dosimeter along with the process followed to obtain NVLAP accreditation including laboratory staffing, quality management system development, customer service development, personnel training and finally detailing the NVLAP onsite assessment and final approval.
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MAM-C.5
10:30 Revision of the ANSI/HPS N13.11-2009 T Ushino*, The MJW Companies
; LA Benevides, US Navy, Retired; WS Harris, Jr., US Army; KM Isbell, Oak Ridge National Laboratory; DF Jones, US Department of Energy; MW Lantz, Arizona Public Service, Retired; SC Perle, Mirion Dosimetry Service, Retired; RK Piper, Pacific Northwest National Laboratory; CG Soares, National Institute of Standards & Technology, Retired
Abstract: The draft revision of the ANSI/HPS N13.11-2009, "American National Standard for Dosimetry - Personnel Dosimetry Performance - Criteria for Testing," has been completed and submitted for review and balloting by the N13 Committee. The work group spent a great deal of time reviewing/correcting inconsistencies within the standard. The test category structure remains the same except for the addition of a fourth subcategory in Category V, Neutron/Photon mixtures. The number of photon spectra used for testing was slightly lowered with the removal of the two NIST Special (S) series beam codes. The WG added greater detail in the exact application of the testing in the various categories. Test irradiation ranges remain unchanged. The performance criteria remain unchanged. The values of L for the accident photon category and for all other categories remain unchanged, as well as the conversion coefficients for photons. The possibility of adding testing for the dose to the lens of the eye was explored but not included in this revision. New appendices were added to provide additional information.
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MAM-C.6
10:45 Thermo Fisher Scientific NetDose Dosimeter Performance MJ Ramlo*, Thermo Fisher Scientific
Abstract: Thermo Fisher Scientific introduces a new family of digital dosimeters called NetDose, beginning with its Gamma-only design. Incorporating patented technology, the dosimeter is designed to meet the performance requirements of ANSI N13.11 and IEC 62387, and meets all the regulatory requirements for deployment in North America and the European Union.
Selected performance results will be presented from the full suite of characterization tests conducted, including energy response, angular response, linearity, over-response, power, mechanical and environmental performance, alarming features, configuration controls, and overload characteristics.
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MAM-C.7
11:00 Occupational Dose Trends in Cardiology M Kirr*, Landauer
Abstract: Cardiology procedures that use ionizing radiation have been rapidly growing in the United States. Personnel working in this specialty are among workers with the highest occupational radiation doses when compared to other individuals that use ionizing radiation. To understand the occupational dose pattern experienced by this specialty in the last 3 years, dose data for more than 10,000 participants was analyzed. These participants wore Luxel+ dosimeters during 2019, 2020, and 2021. It was interesting to observe that the occupational dose per participant decreased substantially in 2021 relative to 2019. While some of the reduction could be associated with delays in diagnostic and treatment due to COVID-19 pandemic, another reason could be better implementation of ALARA principles. Using the dosimeter response data an estimation of the energy of the incident radiation on the dosimeter was evaluated. To understand the influence of the radiation safety practice, a look at the fraction of participants using effective dose calculation (EDE1 and EDE2) was also considered.
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