TPM-C - Decontamination and Decommissioning Woodrow Wilson C 14:30 - 17:00
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| Chair(s): Tom Hansen, Nasser Rashidifard
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TPM-C.1
14:30 Decommissioning Planning for Building 58 at University of Nevada, Reno TW Hansen*, Southeast Compact Commission
; MC Jo, University of Nevada, Reno
Abstract: Building 58 is situated just north of downtown Reno on the University of Nevada, Reno campus. The building is a two-story plus basement unreinforced masonry structure with a usable area of approximately 8,700 square feet. The U.S. Bureau of Mines occupied the building from 1921 through 1954, and the building was contaminated with Ra-226 as a result of activities the Bureau conducted from 1921 to 1924. The target objective of the decommissioning project was to decontaminate the building in a manner that allowed for full, unrestricted occupancy. Immediately upon successful decontamination, the University intended to refurbish the building in a manner that retained its historical significance. A radiological characterization survey was accomplished in 2017 and consisted of gross gamma scans, exposure rate measurements, total surface radioactivity measurements, and removable radioactivity measurements. It was concluded at that time that the building was impacted by residual Ra-226 radioactivity exceeding the acceptable surface contamination levels in U.S. Nuclear Regulatory Commission Regulatory Guide 8.23, Radiation Safety Surveys at Medical Institutions. The Characterization Report described the radiological conditions that were observed on accessible surfaces, however, and many of the building’s remaining original interior surfaces had been covered with newer building materials. The building was also occupied at the time of characterization which impacted the extent to which invasive characterization activities could be performed. Consequently, an additional data collection was accomplished in 2021 to determine the nature and extent of contamination on original surfaces and to evaluate the effectiveness of remediation alternatives. The focus of this presentation is the additional data collection that was performed in 2021, the lessons learned from that activity, and the manner in which that data was used to achieve the project objective.
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TPM-C.2
14:45 Improved Clearance Verification by Use of the Sum of Fractions SR Adams*, Tetra Tech EC, Inc.
; J Jiselmark, Green Field Strategies AB, Sweden; RA Meck, Science and Technology Systems, LLC
Abstract: A previous work (JRP 41:216) showed that the sum of fractions (SOF) of nuclides and its quantified uncertainty can improve verification of clearance. We calculate each addend (fraction) of the SOF, that is, the ratio of the nuclide concentration to its clearance concentration and include the uncertainty of each parameter that constitutes the SOF addend in a Monte Carlo calculation. After a reasonably large number of simulations, we generate a probability curve of the SOF. To demonstrate clearance criteria are met the SOF must add to one or less. The SOF inequality is also known as the unity rule.
We wanted to demonstrate this method with real measurements. We chose measurements from a former site used in the 1950s and 1960s to develop and test nuclear power plant fuel assemblies with varying low enrichments of 235U. The enrichments ranged from 2.7 to 3.9 percent, and the radionuclides of concern were U-234, 235, 238 and their decay products. ICP—MS analysis of the soil samples demonstrated that 234U contributed 70 – 80 percent of the uranium radioactivity. MicroShield code calculations demonstrated that >99.99 percent of the gamma flux from U-234, 235, 238 were in the range of 60 keV to 200 keV. The final status survey was performed using NaI detectors with single channel analyzers calibrated to this energy range. MicroShield and RESRAD codes were used to correlate gamma count rate to U-234, 235, 238 concentrations. We used RESRAD to calculate the clearance concentration (Sv/y)/(Bq/m2) for a residential scenario and included the uncertainty for each nuclide (https://resrad.evs.anl.gov).
Our simulations sampled the entire population of the measurements, and thus there was no need to approximate the data with a predefined distribution, e.g., a log-normal distribution. Our method calculates the mean rather than the median in contrast to the method in MARSSIM and other non-parametric methods. Thus, we calculate the dose to the average member of the critical group. Further, this method is realistic rather than conservative since it uses the real data and their uncertainties. Our use of RESRAD enables one to calculate the time variation of the dose, which is important for uranium mixtures. If the appropriate quality controls are implemented for site characterization, those measurements can be used and become a part of the entire distribution. In that way, there could be a cost saving. Taken together, our emphasis on uncertainty and our method improves the verification of clearance.
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TPM-C.3
15:00 Hard to Detect Radionuclides – A Decontamination & Decommissioning Contractor’s Perspective MP Long*, UCOR
; W Adams, UCOR
Abstract: The U.S. Department of Energy Oak Ridge Office of Environmental Management Contractor—United Cleanup Oak Ridge (UCOR) requested an exemption from 10 Code of Federal Regulations Part 835, Appendix D, Surface Contamination Values. This request modified Appendix D to include a category for hard-to-detect (HTD) radionuclides at 10,000 dpm/100 cm2 removable and 50,000 dpm/100 cm2 total surface contamination values for Plutonium-241, and other HTD radionuclides such as Carbon-14, Iron 55, Nickel-59, and Nickel-63.
A technical basis was prepared to evaluate radiological exposure hazards associated with these radionuclides to on-site workers and the public. Common facility inventories were evaluated to ensure easily detectable indicator radionuclides would ensure compliance with the requested exemption.
This exemption continues the current practice for conducting radiological surveys using standard field instruments for monitoring detectable radionuclides and accommodates special situations where the affected radionuclides are identified (e.g., Pu-241, Ni-63, C-14) using indicator radionuclides.
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TPM-C.4
15:15 Efficacy Of Various Products For The Decontamination Of Actinides In An Ex Vivo Model Of Healthy Or Wounded Skin A Van der Meeren*, The French Alternative Energies and Atomic Energy Commission
; K Devilliers, The French Alternative Energies and Atomic Energy Commission; S Bohand, Orano; F Caire-Maurisier, Central Pharmacy of french Army; M Pasteur, Central Pharmacy of french Army; NM Griffiths, The French Alternative Energies and Atomic Energy Commission
Abstract: Skin contamination by α-emitting actinides such as plutonium (Pu) and americium (Am) is a risk for workers during nuclear fuel production and reactor decommissioning. Decontamination of skin is an important medical countermeasure in order to limit potential internal contamination. Current decontamination recommendations include undressing of victim and followed by skin washing using soap or chelating agents, such as Diethylene Triamine Pentaacetic Acid (DTPA). However, empirical decontamination protocols with numerous products are frequently encountered. In the present study, we assessed the comparative efficacy of different decontaminants and protocols using a recently developed ex vivo rat skin model. Delimited areas of healthy or damaged skin were contaminated with Pu or Am solutions of known properties. Decontamination with different agents was begun after 30 min or 2 h. Among decontamination products, we tested water, DTPA (solution or gel), Trait rouge® cleansing gel, Osmogel, a calixarene nanoemulsion and different hydrogel wound dressings. Only sterile products (water, DTPA solution or gel) were used on damaged skin. Sample activity contained in each decontamination step, as well as the remaining activity in skin were measured by liquid scintillation counting or X/gamma spectrometry. Data indicate that 1- an early decontamination is always more effective than a later one, 2- healthy skin is easier to decontaminate than damaged skin, 3- for healthy skin, the more soluble contaminants are easier to remove, which is not the case for damaged skin. Our ex vivo method using rat skin provides a simple, cheap, rapid “high throughput screening” to evaluate decontamination efficacy for multiple products proposed for actinide-contaminated skin. Finally, our study demonstrates that the highest efficacy is obtained with a DTPA loaded-gel for both Pu and Am in different decontamination protocols and thus is of practical interest
This work has been funded within the frame of the CEA-Orano-PCA agreement.
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TPM-C.5
15:30 Break
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TPM-C.6
16:00 Tritium Inventory Sampling and Characterization G Ascione*, Princeton Plasma Physics Laboratory
; JL Malo, Princeton Plasma Physics Laboratory; AF Carpe, Princeton Plasma Physics Laboratory; SW Langish, Princeton Plasma Physics Laboratory; T Guttadora, Princeton Plasma Physics Laboratory; CR Ferguson, Longenecker & Associates
Abstract: The Princeton Plasma Physics Laboratory (PPPL) at Princeton University (PU) is the DOE national laboratory for magnetic fusion energy and basic plasma physics research. The Tokamak Fusion Test Reactor (TFTR) operated for 15 years, from 1982 to 1997. From November 1993 to April 1997 a mixture of deuterium-tritium (D-T) was used to fuel experiments, leaving the reactor system in an activated and contaminated state. In 2002 PPPL completed a successful D&D project focused on the TFTR reactor removal, leaving the tritium storage and delivery systems in place for future use. In 2021 PPPL initiated the Tritium Systems Demolition and Disposal (TSDD) project to remove all the remaining tritium systems from the facility. Measurements of highly contaminated molecular sieve beds were required to accurately characterize the tritium waste stream and were also used to characterize the facility (DOE-STD-1027-218) during the project. The large size and unique orientation of the molecular sieve beds required inventive techniques for sampling and analysis of the sieve bed material, and a methodology to analyze and quantify the tritium loading on each of three recovery sieve beds. A “wet equilibrium” method was used to develop estimates of the tritium loading for each of the three beds. The results of this analysis put PPPL’s total tritium site inventory at just over 18,000 Ci, characterizing the tritium facility as a Category III Nuclear Facility. The result of the TSDD project and accurate characterization of the inventory was the successful and safe removal of all the tritium inventory from PPPL in early 2023. This project presented some unique Health Physics challenges working with high specific activity material. A discussion of the instrumentation, procedural methods, algorithms, and sampling equipment will be presented.
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TPM-C.7
16:15 Lessons Learned In Health Physics Oversight and Radiological Protection during Tritium Systems Demolition and Disposal (TSDD) at the Princeton Plasma Physics Laboratory (PPPL) JL Malo*, Princeton University
; G Ascione, Princeton University; JW Horner, Princeton University; JW Rayment, Princeton University; DW Thompson, Princeton University; RM Brown, Princeton University; CE Stires, Princeton University; RA Hitchner, Princeton University
Abstract: Princeton Plasma Physics Laboratory (PPPL) is a Department of Energy national laboratory operated by Princeton University dedicated to developing the scientific and technological knowledge base for fusion energy. The Tokamak Fusion Test Reactor (TFTR), which operated from 1982 to 1997 was the first in the world to use a 50/50 Deuterium-tritium mixture, fueled by tritium storage and delivery systems. TFTR was safely decommissioned in 2002, with activated and contaminated legacy tritium systems and equipment retained for future use. In 2021, the Tritium Systems Demolition and Disposal (TSDD) project was initiated to facilitate the removal of all remaining highly contaminated systems and equipment from the facility. This paper will discuss some of the key technical challenges associated with the scope of the project, including the need for radioactive waste characterization, line breaks on contaminated systems, metal pipe cutting, and removal of highly contaminated molecular sieve beds, while protecting personnel, the public, and the environment.
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TPM-C.8
16:30 Gamma Spectroscopy on a Large Scale: Quantification of Uranium in CaF2 Pond Sludge in Super Sacks KE Meyer*, Mirion Technologies - Canberra
; FL Bronson, Mirion Technologies - Canberra
Abstract: Mirion Technologies was contracted to develop, calibrate, and deploy two high-throughput high-resolution gamma spectroscopy systems to quantify low concentrations of uranium in 3.1 million cubic feet of pond sludge to be excavated, packaged into 258 ft3 LiftPacs, and shipped by railcar to a LLW disposal facility. The disposal criterion was <500 ppm total U (average) per railcar. Mirion first performed proof of principle onsite measurements of representative loaded LiftPacs using a single ISOCS-calibrated HPGe detector. The LiftPacs were modeled using ISOCSTM (InSitu Object Calibration Software) mathematical efficiency calibration software [1]. Based on these results, two Mirion MILCC® (Mobile ISOCS Large Container Counter) systems were configured and deployed to the site. Each system consisted of two parallel HPGe detectors, lead collimators and shields, and LYNXTM MCA’s mounted on a cart, connected to a remote laptop computer. The carts were mounted on rails inside a custom ISO trailer to position the detectors at four fixed positions. Loaded LiftPacs were staged outside the trailer at the four positions and counted for ten minutes each. The gamma spectra for each item were summed and analyzed using NDA2000 software, which was also used for monitoring daily QA and background measurements. Mirion wrote the operating procedures for the system and performed weekly and quarterly data reviews. The customer operated the systems. Over 18 months of operation the two systems achieved a combined throughput of up to 100 LiftPacs per day. Approximately 12,200 LiftPacs were measured, equivalent to 116,000 cubic yards of CaF2 waste material. Excavation and characterization of all impoundment ponds was completed in November of 2020.
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TPM-C.9
16:45 Moonage MARSSIM (a shout out to Ziggy stardust) N Rashidifard*, Mirion
Abstract: Watching television shows with experts performing measurements always leave more questions than answers since the goals are to generate ratings. Recent shows feature land areas claiming to be connected to extraterrestrial activity, one of such involved GPS mapping radiation surveys. These often feature miscellaneous equipment and lack of rigor for a proper survey. One always thinks about how the results would turn out if a proper survey protocol was used to assess these land areas. To demonstrate this a land area survey conducted on the areas involved in the 1965 “Incident at Exeter” located in Exeter and Kensington, NH. Spectroscopic gamma, ambient dose rates, and gross neutron count rates will be mapped over the areas in put into GIS. MARSSIM methodology will be employed and results presented. This presentation is intended to show MARSSIM methods and approaches using a lighthearted pop culture twist.
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