N4A3  Instrumentation in Environmental and Safety Applications

Thursday, Nov. 5  08:30-10:10  Golden West

Session Chair:  Zane Bell, , United States; David Chichester, Idaho National Laboratory, United States

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(08:30) N4A3-1, Performance of a Characteristic X-ray Camera to Identify Contamination of Radioactive Cesium

S. Kobayashi1, T. Shinomiya1, Y. Goto2, Y. Terakado2, A. Yamanishi3, H. Kitamura1, K. Tanimoto2, Y. Uchihori1

1National Insititute for Radiological Sciences, Chiba, Japan
2Meisei Electric Co., Ltd, Isezaki, Japan
3IHI Corporation, Tokyo, Japan
The lightweight, high sensitivity and low-price camera to image Cs-137 contamination in environment has been developed. These three merits have not been realized by recent gamma cameras and Compton cameras. The camera images Cs-137 distribution by detecting the characteristic X-rays from it instead of gamma-rays. We have investigated the performance of the characteristic X-ray camera (CXRC) in detail and the specification is summarized.

(08:50) N4A3-2, Pilot Study of the Application of Plastic Scintillation Microspheres to Rn-222 Detection and Measurement

K. K. Mitev1, I. S. Dimitrova1, A. Tarancon2, D. S. Pressyanov1, L. T. Tsankov1, T. A. Boshkova1, S. B. Georgiev1, R. J. Sekalova1, J. F. Garcia2

1Faculty of Physics, Sofia University, Sofia, Bulgaria
2Department of Analytical Chemistry, University of Barcelona, Barcelona, Spain
The work tests the possibility to use plastic scintillation microspheres (PSms) for a new application - to detect Rn-222 (radon) in air and water. The idea is to expose PSms in the media and to measure them by scintillation counting. The applicability of this approach depends on the ability of PSms to absorb Rn-222 from the environment. This ability is characterized by the sampling efficiency (the ratio of the activity absorbed in the sample volume to the activity in an equal volume of the ambient media). The sampling efficiency of PSms synthesized from polystyrene to Rn-222 in air and water was studied experimentally. PSms were exposed to controlled Rn-222 activity concentration and the activity inside them was determined by gamma-spectrometry with HPGe detector. The sampling efficiency of PSms with average radius of 34 µm exposed in air for 40h at 24°C was estimated at 4.95 ± 0.54. The sampling efficiency of PSms with average radius of 29 µm exposed in water for 94h at 20°C was estimated at 37.2 ± 5.1. The results showed that polystyrene PSms concentrate Rn-222 in their volume and could be used to sample it from the ambient media. To describe the processes of radon transport inside a polystyrene sphere a theoretical model is used. Based on it, equations for the evolution of radon activity and its distribution in the PSms are derived. Examples for their application are presented. Estimates of the counting efficiency of PSms (the ratio of the counting rate and the absorbed activity) were also obtained for two scintillation counters. It was noted that when the quantity of PSms in the vial increases, the counting efficiency decreases and the spectrum shape changes. The effect is associated with optical quenching in the PSms sample. Overall, the presented results demonstrate the feasibility of Rn-222 detection by exposure and scintillation counting of polystyrene PSms.

(09:10) N4A3-3, Tests of CDs/DVDs as Passive Radon and Thoron Detectors for Mines and Caves

D. Pressyanov1, D. Dimitrov2, S. Georgiev1, I. Dimitrova1

1Sofia University, Sofia, Bulgaria
2Mining and Geology University, Sofia, Bulgaria
Radon (222Rn) exposure is evident health hazard in a substantial number of underground mines. Exposure to thoron (220Rn) is usually considered to be of secondary importance, but radiation data regarding 220Rn is very scarce compared to that for 222Rn. In planning area and personal monitoring in underground places (mines and caves) 220Rn issue should be addressed at least for two reasons: (1) to revise the possibility for increased exposure related to 220Rn; (2) To ensure that 222Rn results are not biased due to the sensitivity of detectors to 220Rn, as it was recently found for many commercial 222Rn detectors. In this report we test the applicability of CDs/DVDs as novel passive detectors for differential measurements of 222Rn and 220Rn in underground mines and caves. This is achieved by etching and counting alpha tracks at two different depths beneath the disk surface and analysis of the signals. To test the performance of the method and to check whether there is significant presence of thoron, 13 CDs were exposed in the underground galleries of a metal mine for 4 months. Results revealed that both 222Rn and 220Rn are present at the monitored places and in some cases the levels of 220Rn are higher than those of 222Rn. The CDs proved to be appropriate for measurements in the underground environment and stayed undamaged during the exposure. Additionally, dedicated laboratory experiments were made to test an approach to expand the range of 220Rn concentrations measurable at high 222Rn concentrations. The method proved its applicability for differential measurements of 222Rn and 220Rn over a wide range of concentrations. Radon concentrations well below the regulatory levels for workers are measurable even within 1 month exposure.

(09:30) N4A3-4, The Application of Muon Tomography to the Monitoring of Stored Carbon Dioxide in Carbon Capture and Storage

L. F. Thompson1, P. M. Chadwick2, S. J. Clark3, A. Cole1, M. Coleman4, J. G. Gluyas3, J. Klinger1, V. A. Kudryavtsev1, D. L. Lincoln5, S. J. Nolan2, S. Pal1, S. M. Paling6, N. J. C. Spooner1, D. Woodward1

1Department of Physics and Astronomy, University of Sheffield, Sheffield, United Kingdom
2Department of Physics, Durham University, Durham, United Kingdom
3Department of Earth Sciences, Durham University, Durham, United Kingdom
4NASA Jet Propulsion Laboratory, Pasadena, CA, USA
5Department of Civil and Structural Engineering, University of Sheffield, Sheffield, United Kingdom
6STFC Boulby Underground Science Facility, Boulby, United Kingdom
Current methods of monitoring subsurface CO2, such as repeat seismic surveys, are episodic, costly, and require highly skilled personnel to operate. Simulations based on simplified models have previously shown that muon tomography could be used to continuously monitor CO2 injection and migration. We present a model of the monitoring of CO2 plume evolution in a geological reservoir using muon tomography. The stratigraphy in the vicinity of a nominal test facility is modelled using geological data, and a numerical fluid flow model is used to describe the time evolution of the CO2 plume. A planar detection region with a surface area of 1000 m2 is considered, at a vertical depth of 776 m below the seabed. We find that one year of constant CO2 injection leads to changes in the column density of ?? 1%, and that the CO2 plume is already resolvable with an exposure time of order 50 days. The design and performance of the operation of a prototype borehole detector, deployed in a mock borehole in the Boulby Underground Laboratory, is also discussed.

(09:50) N4A3-5, B-RAD: a New Radiation Survey Meter for Operation in Intense Magnetic Fields

D. Celeste1, A. Curioni1, A. Fazzi2, D. Perrin1, C. Pirovano2, M. Silari1, V. Varoli2

1CERN, 1211 Geneva 23, Switzerland
2Department of Energy, Politecnico of Milano, 20156, Milano, Italy
B-RAD is a novel, hand-held radiation survey meter, capable of operating in regions of strong magnetic field up to 1 Tesla. This innovative device was developed on request of the LHC experiments, which asked CERN Radiation Protection group an instrument to perform measurements of the residual radioactivity (radiation surveys) in the experimental halls and inside the ATLAS detector with the magnetic field still on. Starting in 2010, the instrument was developed in a joint collaboration between the CERN RP group and the Polytechnic of Milan, Italy. The sensitivity range, in terms of dose rate for gamma radiation, is from 0.1 µSv/h (background radiation level) to a 1 mSv/h. B-RAD covers the energy range for gamma rays between 60 keV and 1.3 MeV. The instrument consists of two parts: an active probe and a counting unit. Five devices have been built and made available for routine use at CERN. Here we will present the device, results from its characterization, and plans for further developments.