MAM-B - Decommissioning and Decontamination North 222ABC 11:00 - 11:45
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| Chair(s): Ethan Asano
, Latha Vasudevan
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MAM-B.1
11:00 Hybrid Radiation Transport Methods for Detector Response Modeling of US EPA Superfund Counts Per Minute (CPM) Calculator EA Asano*, Texas A&M University
; D Coleman, Texas A&M University; A Perry, Texas A&M University; G Davidson, Oak Ridge National Laboratory; F Dolislager, Oak Ridge National Laboratory; S Walker, U.S. Environmental Protection Agency; S Dewji, Texas A&M University
Abstract: The Health Risk and Regulatory Analysis team at Oak Ridge National Laboratory has requested modeling research for validation of the Environmental Protection Agency’s Counts-Per-Minute calculator scheduled to be released in 2021 by the Environmental Protection Agency’s Superfund program. This tool will calculate the anticipated radiation detector reading in counts per minute that corresponds to a cleanup goal by converting radioactivity in either pCi/cm2 or pCi/g to counts per minute. This tool will help to reduce the amount of interim sampling during site investigation, but not eliminate final confirmation sampling for site release. Radiation transport modeling using the Monte Carlo N-Particle radiation transport code and hybrid Monte Carlo code, Shift, were employed to model detector responses for four NaI(Tl) scintillation detectors (0.5x1, 1x1, 2x2, and 3x3-inch) for various depths of gamma-ray contamination distributed in various media. Source-detector distances of 0.5 cm, 1 cm, 2.54 cm, 10 cm, and 30 cm were modeled. Media of soil, concrete, wood, steel, drywall, glass, and drywall were evaluated for contamination depths ranging from surface to a depth of an infinite thickness in each medium for photon energies ranging from 20 keV to 3 MeV. Monoenergetic response function data for each of the media, contamination depths, and detectors were calculated using Monte Carlo N-Particle radiation transport code for the Surface Counts-Per-Minute energy deposition. Shift was harnessed to increase computational speed of particle transport in high attenuating media for Volume Counts-Per-Minute to obtain cell fluxes. Volume cell flux values from Shift were integrated with a response function from Monte Carlo N-Particle radiation transport code to convert cell flux to energy deposition. Interpolation of the monoenergetic to expected radionuclide emissions were conducted using the International Commission on Radiological Protection Publication 107 decay data.
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MAM-B.2
11:15 Laboratory Exercises Illustrating Radiation Instrument Selection, Surveying, Source Search, and Decontamination for College Students and the General Public JD Noey*, University of Michigan
; KJ Kearfott, University of Michigan
Abstract: Radioactive contamination poses an ever-present possibility when dealing with any radioactive materials. With the risk of higher active sources leaking to ruptured button sources, one must not only be familiar with performing routine safety checks but know how to handle the situation in the event of radioactive contamination. In a situation where unnecessary exposure, internal contamination, or external contamination is found, it is critical to assess the situation and follow each step appropriately, from controlling area access to knowing who to contact. Given the high hazard radioactive contamination present, it is difficult to model such a situation to gain practical knowledge and training. Most university students do not gain the necessary experience of handling a hazardous scenario until they encounter it firsthand. A formal laboratory experiment, taking less than 2 h to complete, was developed to safely create a scenario where students can practice surveying for radioactive material and handling radioactive contamination. This teaches students how to select proper survey instruments, use appropriate surveying techniques, and follow exact steps in the event of suspected radioactive contamination.
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MAM-B.3
11:30 Design Concept for Autonomous Robot for Sub-surface Environmental Characterization at Decommissioning Sites CE Bayne*, Department of Nuclear Engineering, Texas A&M University
; CC Smith, Department of Nuclear Engineering, Texas A&M University; WW Smither, Department of Nuclear Engineering, Texas A&M University; JT Torres, Department of Nuclear Engineering, Texas A&M University; SM Fowler, Department of Nuclear Engineering, Texas A&M University; SA Dewji, Department of Nuclear Engineering, Texas A&M University
Abstract: The current process of performing sub-surface site characterization in nuclear decommissioning projects involves many labor and time intensive procedures, such as manual sample acquisition, sample transportation, and off-site sample analysis. A design for an autonomous robot capable of sub-surface sample acquisition, on-board sample analysis with depth-dependency, and sample transportation is proposed to significantly reduce the human labor costs, as well as reduce the length of time to characterize decommissioned sites. The proposed design concept is capable of all three of the required functions, and a comparison will be made to current operations which entail sub-surface characterization surveys conducted manually by personnel. The on-board sample analysis design function was approached through the utilization of a sodium-iodide detector, bismuth shielding, and on-board gamma spectroscopy. Dosage limits were defined by the decommissioning regulatory requirements provided by MARSSIM, and the detector’s functional capabilities were determined by comparing its minimum detectable activity to the activities associated with the regulatory dosage limits. Evaluated areas of the design concept include source term estimations, detector systems and their capabilities, sample storage design, detector and sample shielding, and inventory and data management.
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