MAM-D - Power Reactor Centennial Ballroom 300D 09:30 - 11:15
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| Chair(s): Rick Adams
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MAM-D.1
09:30 Thirty Years of International NPP Worker Outage Dose Reduction Operating Experience Sharing under OECD NEA /IAEA ISOE Program DW Miller*, University of Illinois
; BR Boyer, Tennessee Valley Authority
Abstract: Thirty Years of International ALARA Information Exchange: Successes in Worker Dose Reduction & Plant Asset Preservation
By Brad Boyer, TVA RP Fleet Manager & David W. Miller, University of Illinois
Abstract:
Preservation of the US operating fleet of nuclear power plant components and systems is critical for the safe and efficient operating of units for the next 40 years. The paper describes dose reduction studies to reduce dose to workers and preserve plant components based on 30 years of successful ALARA information exchange under the OECD NEA/IAEA ISOE program involving 350 reactors in 27 countries.
The North American Technical Center, ISOE (Information System on Occupational Exposure) has provided operational health physicists with new technology and RP management lessons learned to prevent reoccurrence since 1992. The paper describes new ALARA tools and technology developed by US national labs and universities to help Radiation Protection Managers maintain worker doses ALARA. New technology discussed include colloid removing resins and chemical engineering solutions to address Co-60 and Ag-110m contaminates in plant piping and components. Over 20 US PWRs have achieved outage doses from 14-person rem to 25-person rem compared to European PWRs recording 60-to-70-person rem. US successes are being shared with European RPMs under the ISOE program of expert working groups to solve RPM problems.
The North American Technical Center has also beta tested the new pixelated, 3D CdZnTe individual isotope mapping system at the Cook Nuclear Plant in 2014. The new technology was developed under 20 years of US government research grants to the University of Michigan. The new technology has over 70 units in use at US and Canadian RP Departments. The IAEA has selected the new technology to replace the IAEA safeguard isotopic surveillance instrumentation in 2022.
NATC ISOE plans for the next 30 years will be discussed by the Chairperson of the ISOE Management Board, Bradley Boyer, TVA RP Fleet Manager.
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MAM-D.2
09:45 Radiological Characterization in Bare Leu U-10mo Before And After Heat Treatment D Calderin Morales*, Pacific Northwest National Laboratory
; ZF Huber, Pacific Northwest National Laboratory; CZ Soderquiest, Pacific Northwest National Laboratory; CL Arendt, Pacific Northwest National Laboratory; VV Joshi, Pacific Northwest National Laboratory; KP Brooks, Pacific Northwest National Laboratory; MA Rossiter, Pacific Northwest National Laboratory; C Lavender, Pacific Northwest National Laboratory
Abstract: Fuel for the U.S. high-performance research reactor fleet is undergoing significant development as the United States moves away from using highly enriched uranium dispersion fuels. The proposed fuel is a high-density, low-enriched uranium (LEU, 19.75 wt% U 235) alloyed with ten weight percent molybdenum fuel (known as LEU U 10Mo). The LEU U-10Mo material undergoes several thermal processing steps to attain the desired form and meet the specifications of the fuel plate. The present work focuses on methods to characterize and understand the contamination level variability in bare fuel (as cast and cut to ingots), prior to and after heat treatment. Contamination level variation is suspected to originate from ingrowth of uranium decay products over time, together with diffusion and accumulation on the outer surface. To characterize the uranium decay products ingrown in the alloy without interference from uranium and molybdenum, a source-sample of LEU U-10Mo (two years after processing, analyzed as-is) was dissolved in concentrated acid. The uranium and molybdenum were separated out by anion exchange, leaving the decay chain products in solution. The solution was analyzed by gamma and alpha spectroscopy. The gamma spectra shows a cluttered spectrum with minor components of the decay chains and high uncertainty on the nuclide identification. The alpha spectroscopy results clearly showed ingrowth of Th-228, Ra-224, Rn-220, Po-216 (daughters of U 232/236), and Th-230 from U-234. The level of ingrown Th-230 activity is approximately equal to the ingrowth expected from U-234 after two years’ decay. Presence of Po-215 in the alpha spectrum proves that Ac-227 and likely its parent Pa-231 were also present. It was also hypothesized that thermal processing influenced diffusion of uranium decay products from the interior to the surface of the alloy. To test this hypothesis, a sample was thermally treated in a furnace at 900°C for 144 hours under vacuum, while another sample (from the same material) was kept as control. Next, the samples underwent controlled etching to remove thin layers approximately 5 microns thick. This step was repeated two more times to quantify the progeny levels at three different depths in the sample. The surface beta/gamma and alpha activities of the homogenized sample were higher than the activities measured for the same sample before heat treatment (Mo homogenization). Of significance, the homogenized sample had 51% less mass; however, it exhibited more surface activity (alpha and beta/gamma). The alpha activity increased by 12% and the beta/gamma activity increased by a factor of 2.5. The beta-to-alpha activity ratio also increased by a factor of 1.50. The thermal processing experiment showed that the surface of the heat-treated sample had more progeny activity than the surface of the non-heat-treated sample per layer etched. This behavior was noticed for Th 234/Pa 234m, Th-230, Th-228, and Po-215. The activity was higher at the first surface etched from the heat-treated sample, while subsequently etched layers from the same sample seemed to be “depleted” in decay products relative to proportions that would be expected. The mechanism involved can potentially be attributed to vacancy movements among the atoms. In these vacancy movements, atoms exchange positions or move collectively via grain boundary diffusion, chemical diffusion, and intrinsic diffusion. Future research will investigate mechanisms in more depth
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MAM-D.3
10:00 Advantages Of Real-Time Positioning for Nuclear Power Health PhysicsOperations NB Rashidifard*, Mirion Technologies
; D Jarrow, Mirion Technologies; J Kost, Mirion Technologies; W Berrien, Mirion Technologies; F Moerel, Mirion Technologies
Abstract: Operating Nuclear Power Plants have a unique Health Physics environment and require unique support to minimize exposure to personnel. This is especially true during refueling outages where there is a constant turnover of complex radiological evolutions. These challenges have been difficult over the years due to a shrinking number of experience staff. The introduction of telemetry hardware and software helped bring real-time data out of the work areas to be monitored by Health Physics staff. Limitations to this approach were technological at the time and was not able to provide positioning data without the use of camera systems. This need inspired the development of the Orion Real-Time Location System to provide the modern tools needed to promote efficiency while maintaining constant radiological coverage. Orion represents the next generation in Health Physics supervision using radiological telemetry uniquely blending real-time radiological data with dynamic position location. Using Orion the location and radiological data associated with Electronic Personal Dosimetry, Area Monitors, Airborne Contamination monitors are all visualized in 2D or 3D environments, providing a valuable ALARA tool.
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MAM-D.4
10:15 The Effect of Radiation and Dose on Diffusion Pump Oil JP Smith*, Department of Environmental Engineering and Sciences, Clemson University
; CS Wright, Department of Environmental Engineering and Sciences, Clemson University; G Larson, Savannah River National Laboratory, Aiken, SC; T Guin, Savannah River National Laboratory, Aiken, SC; VN Bliznyuk, Department of Environmental Engineering and Sciences, Clemson University, Center for Nuclear Environmental Engineering Sciences and Radioactive Waste Management, Clemson University; TA DeVol, Department of Environmental Engineering and Sciences, Clemson University, Center for Nuclear Environmental Engineering Sciences and Radioactive Waste Management, Clemson University
Abstract: This research quantifies some of the chemical and physical changes that occur to commercially-available diffusion pump oils irradiated with gamma-ray and neutron radiation up to 10 MGy. One aliphatic, two silicon, and two polyphenyl ether diffusion pump oils were each irradiated up to 1.5 MGy at a dose rate of 20 kGy/hr using a Co-60 source at Savanna River National Laboratory (SRNL). Neutron irradiation up to 10 MGy was conducted incore at the Rhode Island Nuclear Science Center (RINSC) TRIGA reactor at a flux on the order of 1013 n/cm2*s. Neutron irradiation led to some activation of the oil which was identified using gross alpha/beta counting, liquid scintillation (LSC), and gamma spectroscopy with a High Purity Germanium detector (HPGe). Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, and Nuclear Magnetic Resonance (NMR) were used to quantify changes in cross linking and polymerization in the irradiated oils as well as changes to chemical structure. Initial inspection after irradiation showed that the viscosity of the oils increased, and the color was noticeably darker. Viscosity was measured before and after irradiation to quantify physical changes in the oils as a result of radiation. FTIR was unable to discern any difference between irradiated and unirradiated oil, but preliminary testing using Raman spectroscopy looks promising. These experiments are being conducted as part of an investigation into cost-efficient alternatives to the turbo cryopumps that are currently designated for the ITER fusion reactor. Critical to the application of diffusion pumps in a radiation environment is to assure that the physical and chemical properties of the oil be maintained for a reasonable lifetime.
This work is being funded under ARPA-E grant #DE-AR0001376.
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MAM-D.5
10:30 Research Reactor Waste Challenges/Achievements DD Doenges*, University of Missouri Research Reactor
Abstract: This presentation will outline the challenges of sending a once in 10 year Type B waste shipment out of the University of Missouri Research Reactor. It explains the nature of the shipment and the unique Health Physics challenges that were presented. This will also discuss the facility wide effort that went into performing the shipment and the coordination effort that was needed.
Secondly this will discuss the lessons learned and how they impacted a second shipment less than 2 years later.
Finally, there will be discussion on the challenges with sending small items containing high concentration or concentrations of TRU material based on restrictions in averaging waste by volume or mass.
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MAM-D.6
11:00 Current Status of Radiation Controlled Areas in Korean Nuclear Power Plants SJ Kim*, Chosun University
; WS Choi, Chosun University; JH Son, Chosun University; HP Kim, Chosun University; CJ Song, Chosun University
Abstract: There are various radiation sources in nuclear power plants (NPPs). The radiation controlled areas (RCAs) in NPPs are operated to protect workers from these radiation sources and provide appropriate radiation protection measures. The operation of RCAs in Korean NPPs is required by the Korean Nuclear Safety Act based on the 1990 Recommendations of the International Committee on Radiological Protection. According to the Korean regulation, the RCA is defined as an area in which the external radiation dose and rate, the concentration of radioactive materials in the air, or the degree of surface contamination of materials polluted by radioactive materials exceeding the limit determined by rules of the Nuclear Safety and Security Commission. Public access must be restricted for radiation safety in the RCAs, and protection measures are required to prevent excessive radiation exposure. In addition, high radiation areas are classified as areas where the external radiation dose rate may exceed or exceed 1 mS h-1 at a distance of 30 cm from the surface of the radiation source or shield in RCAs. In Korea, a total of 24 NPPs are in operation, including 21 pressurized water reactors (PWRs) and 3 pressurized heavy water reactors (PHWRs). The RCAs are set up for each NPP. Korean PWRs operate four, six, or eight zones in the RCAs based on dose rate criteria. In Korean PHWRs, the RCAs are classified based on access conditions, the representative areas, working hours, and the target dose rates. This paper introduced the RCAs in Korean NPPs by investigating the final safety analysis report of each NPP.
Acknowledgment
This research was supported by the Nuclear Safety Research Program through the Korea Foundation of Nuclear Safety using the financial resource granted by the Nuclear Safety and Security Commission of the Republic of Korea (No. 2106024-0121-SB110).
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