The 61st Annual Meeting of the Health Physics Society

17-21 July 2016, Spokane, WA

Single Session



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TAM-C - Special Session: Environmental Radon

111 B   08:30 - 12:00

Chair(s): Matthew Barnett
 
TAM-C.1   08:30  Environmental Radiation Dosimetry for the Techa River Population BM Napier*, PNNL ; MD Degteva, Urals Research Center for Radiation Medicine

Abstract: Members of the Techa River Cohort (TRC) are being studied in an effort to test the hypothesis that exposure at low-to-moderate dose rates has the same effectiveness as exposure at high dose rates. The goal for the Techa River Dosimetry System (TRDS) is to provide the best possible assessment of individual external and internal doses for use in epidemiological studies of the TRC members and other persons who were exposed beginning in 1949 to releases of radioactive materials from the Mayak Production Association. A significant portion of these releases consisted of long-lived radionuclides, mainly 90Sr. A large area in the same Urals region was also contaminated with long-lived radioactive materials in 1957 when the East Urals Radioactive Trace (EURT) was formed following an explosion of a high-level waste tank. Dose reconstruction in the TRDS is based on the use of a large number of measurements of long-lived radionuclides in people and in the environment and external exposure rate measurements in places where populations lived. The doses are supported strongly by 33,000 measurements made with a tooth-beta counter, 10,000 measurements of bones collected at autopsy, and 44,000 measurements made with a special whole body counter. The traditional approach of modeling all steps of the pathway of exposure is used as a backup only when other approaches were exhausted. The TRDS calculates doses from external exposures from living along the banks of the Techa River and in the region of the EURT and internal exposures from intakes acquired along the Techa River and in EURT villages. Individual residence-history data are used. The end point of dose accumulation is also determined individually. Medical X-ray exposure can be considered as a confounding source of radiation exposure for the TRC members and the TRDS calculates doses from X-ray procedures. The TRDS version created in 2000 was used initially to derive risk coefficients for the TRC members; an improved version (TRDS-2009) was later used. An update, providing individual uncertainty estimates, is scheduled for 2016. TRDS doses are being used in companion epidemiological studies. The TRDS methods have been referenced by the NCRP, supplemented by efforts of the European Commission, and are being incorporated by UNSCEAR.

TAM-C.2   09:00  Monitoring and Displaying Radon Measurements in Washington MJ Brennan*, Washington Office of Radiation Protection ; T Echeverria, Washington Department of Health

Abstract: Radon measurements are useful for determining the radon levels in a particular building, but it has been difficult to aggregate the information to help with the "Larger Picture". This is particularly true in states with small or no Radon Programs, and lacking the resources to dedicate to data management. This has led to a reliance on the decades-old Environmental Protection Agency Radon Zone Map, which has limitations. The Washington Tracking Network (WTN) provides a new tool for displaying radon information in ways more useful for the public. The WTN also captures other information which can be used to better understand radon distribution and exposure patterns. As with any work in progress, there are improvements that can be made. There are also limits set by existing technology and data structure and quality. Ways of addressing these limits, applicability to other states, and possible advances in handling radon measurement data will be discussed.

TAM-C.3   09:15  A comparison of 11CO2 and 85Kr as calibration gases for a beta-detecting stack monitor for PET manufacturing facilities DJ Krueger*, Siemens Molecular Imaging ; WR Moroney, Siemens Molecular Imaging; FL Plastini, Siemens Molecular Imaging; JM Parkin, Ultra Electronics � Nuclear Control systems

Abstract: An increase in scrutiny on the calibration of stack monitors for PET nuclide production facilities presents some technical challenges. The main PET radiopharmaceutical nuclide is 18F. Its normally volatile form (H18F) is very reactive and unsuitable for calibrating stack monitors unless converted to a non-reactive, volatile compound; this has proved difficult with current automated chemistry modules used in PET drug manufacturing. 11CO2 gas, which is mainly non-reactive, can be produced at some PET cyclotrons and used for gas calibrations, but not all facilities are equipped with the targets and support equipment to allow its production. For stack monitor systems that rely upon the detection of the beta (positron) to quantify activity, the use of 85Kr was investigated as an alternative. 85Kr is a non-reactive gas with a 10 year half-life; its beta energy is very close to 18F’s positron energy and it is commercially available. The Ultra Electronics Nuclear Control Systems (UENCS) stack monitor removes a sample from the duct and passes it through a fixed volume counting chamber that counts betas/positrons in a thin plastic scintillator. 11CO2 was created in the cyclotron and pushed to a syringe in a hot cell. The hot cell is ventilated to a duct where the UENCS sample is withdrawn. The activity in the syringe was verified in a dose calibrator and released inside of a hotcell. 85Kr was obtained in gas cylinders; a manifold with pressure gauge allowed equalizing the pressure in two tanks and activity was calculated using the Ideal Gas Law. In addition to comparing the detector response to 11C and 85Kr, the detection chamber was exposed externally to a 137Cs solid source in a reproducible geometry. The solid source allows for a check on the detector response that can be used as a constancy test to determine if the calibration remains within a specified response range into the future. Results are presented, demonstrating a suitably close agreement between the calibration factor obtained using 11C gas and 85Kr gas, indicating the promise of the proposed method for system calibration.

TAM-C.4   09:30  Evaluation of an Upward Trend in Background Counts from a Stack Continuous Air Monitor JM Barnett, PNNL ; JP Rishel*, PNNL

Abstract: The Pacific Northwest National Laboratory Radiochemical Processing Laboratory is designed as a multi-purpose non-reactor nuclear research facility. Regulations require continuously sampled and monitored radiological exhaust from the main stack. During the last annual continuous air monitor (CAM) calibration, the measured alpha and beta/gamma background counts continued to trend higher than normal, particularly when compared to historical background counts from previous calibrations. The source of the high background counts was assessed through a historical analysis of previous calibration results, a comparison to the record sample data, and an evaluation to building radon emissions which showed elevated radon/progeny in the sample stream. An environmental assessment is underway to address the cause(s) of the increased background/radon measurements including evaluating building research activities, associated radioactive material usage and storage, whether the CAM is internally contaminated, and the adequacy of procedures. Resolution should provide a path forward for continued optimal operations whereby there is consistent correlation between sample data and monitoring results.

TAM-C.5   09:45  The WIPP Radiological Release Effluent Correlations RH Hayes*, North Carolina State University

Abstract: The radiological event from February 14th of 2014 at the WIPP allowed a unique test for consequence assessment applications. The radioactive effluent was monitored using representative sampling, and the off-site air samplers were properly operating throughout the release. The predictive abilities from NARAC when compared to measurements taken during the release demonstrated impressive accuracy and precision of this capability. The relative bias, correlation and potential dosimetric implications are sufficient to show meaningful utility for both emergency response and nonproliferation applications.

TAM-C.6   10:30  Open Sites with Radiocesium Contaminated Soil: Evaluating Dose Rates and Remediation Strategies A Malins*, Japan Atomic Energy Agency ; H Kurikami, Japan Atomic Energy Agency; S Nakama, Japan Atomic Energy Agency; M Machida, Japan Atomic Energy Agency; A Kitamura, Japan Atomic Energy Agency

Abstract: This presentation covers some of JAEA's research into the relationship between radiocesium distributions within soil and air dose rates. Relevant factors include the spatial distribution of the radiocesium and its depth distribution within the ground. These factors evolve over time due to weathering. JAEA has been monitoring air dose rates and radiocesium in soil cores over Fukushima Prefecture since the 2011 Fukushima Daiichi accident. We developed a tool to calculate ambient dose equivalent rates (H*(10)) from arbitrary radiocesium input distributions, and validated the tool using our Fukushima data. We have performed a systematic analysis of how H*(10) changes under different soil remediation scenarios. Both the initial radiocesium depth distribution and the extent of remediation (mass depth and area) were variables considered in the analysis. The results can be used to gauge the reduction in H*(10) after remediation, given the chosen method, extent, and the number of years elapsed post-fallout.

TAM-C.7   11:00  Darlington Newbuild Environmental Assessment - An Overview DB Chambers*, Arcadis

Abstract: The existing Darlington Nuclear site is approximately 60 km east of Toronto on the north shore of Lake Ontario. The Darlington Nuclear site currently hosts four large Candu reactors and onsite used fuel dry storage facility. Ontario Power Generation (OPG), the operator of the Darlington site has proposed the construction of up to four new nuclear reactors at Darlington. The Project is expected to generate up to 4,800 megawatts of electricity for delivery to the Ontario grid as a component of Ontario's commitment to maintain nuclear supply of Ontario's electricity at 50%. In support of this project, a multi-year environmental assessment (EA) was performed to assess site preparation, construction, operation of the reactors and related facilities for approximately 60 years, including the management of conventional and radioactive waste; and the decommissioning and eventual abandonment of the nuclear reactors and associated facilities. The EA was submitted to a Federal review Panel which started to meet the week following the Fukushima incident. On October 30, 2009, the Minister and the President of the Canadian Nuclear Safety Commissions appointed a three-member Joint Review Panel (Panel) to consider the environmental assessment for the Project and concluded that the Project is not likely to cause significant adverse environmental effects, provided the mitigation measures proposed and commitments made by OPG during the review, and the Panel’s recommendations are implemented. This paper reviews a number of the technical issues that arose during the preparation of the EIS and how they were addressed in the EA and in the Hearing. A short commentary on the challenges of communicating technical issues with the public are also discussed.



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