Patent Application
20100084561
Embodiments of the inventions herein relate to systems, devices, and methods for collection of radionuclides.
Many sites globally have ground water and surface water contamination resulting from past activities associated with nuclear reactors, nuclear fuel reprocessing, or uranium enrichment. Some of the primary environmental contaminants are radionuclides with long to moderate half-lives that should be measured and monitored to determine the extent of plume migration and potential exposure to the general public. Predominant among these radionuclide contaminants are the isotopes strontium-90 (90Sr) and technetium-99 (99Tc). These isotopes can be difficult to measure and monitor because they decay by pure beta particle emission and do not release any measurable gamma or x-ray photons. Consequently in situ gamma detectors that are often used for other isotopes are not applicable to 99Tc and 90Sr isotope measurements. For measurement of these isotopes, samples are typically physically collected from monitoring wells (grab samples) and transported to be analyzed in analytical laboratories, usually by lengthy and expensive separation procedures.
Recently, it is desired to reduce costs of sampling and monitoring plume activities. Numerous monitoring wells have incorporated automated down-hole water level, water temperature and electrical conductivity (salinity) sensors. In addition, many of these systems are also equipped with telemetry for remote network access to data. However, despite these automated measurement capabilities, liquid grab-samples are taken and transported to a laboratory for analysis for most chemical and radiological analysis. These monitoring and sampling activities are performed on schedules ranging from monthly to yearly. Often it can take weeks to months to receive data. The costs associated with obtaining the grab-samples and performing subsequent analysis may be excessive. Sampling events are also subject to weather conditions. Accordingly, it is desirable to develop other systems, devices, and methods for collecting, detecting, and/or monitoring radioisotopes.
A radionuclide detector system including a collection device comprises a mixture of a polymer, a fluorescent agent, and a selective chemical extractant. The detector system includes at least one photomultiplier tube (PMT).
A device, used for collection of radionuclides, includes a mixture of a polymer, a fluorescent organic scintillator, and a chemical extractant.
A method for detecting radionuclides includes collecting and concentrating radionuclides from an aqueous environment within a collector device comprising a mixture comprising a polymer, a fluorescent organic scintillator, and a chemical extractant.
Embodiments of the invention are described below with reference to the following accompanying drawings.
Systems, devices, and methods of the present invention are used for collection, concentration, detection and/or monitoring of radionuclides in an aqueous environments, such as rivers, lakes and groundwater systems, where potential contamination exists from nuclear reactors, nuclear fuel reprocessing or uranium enrichment. The systems and devices have been developed to monitor isotopes such as strontium-90 (90Sr) and technetium-99(99Tc). Since such isotopes decay by pure beta particle emission, not releasing any measurable gamma or x-ray photons, such isotopes are difficult to measure and monitor.
Water plumes can be contaminated with 99Tc and/or 90Sr. Technetium exists predominately as the highly mobile pertechnetate anion (99TcO4−), being extremely mobile in both ground water and surface water. Due to the relatively high activities, ease of transport, and potential hazard, the 99Tc radionuclide requires constant and regular monitoring. At particular sites 99Tc has been known to have migrated offsite and be present in ground water plumes at concentrations that exceed various water standards. 90Sr activities are relatively localized but can also be found in relatively high concentrations in some locations. Accordingly, detection and monitoring of 90Sr and 99Tc, as well as other radionuclides, at locations is desirable.
The systems, devices, and methods of the invention are described below primarily with respect to use in an aqueous environment such as a monitoring well for detection, collection, concentration and/or monitoring of one or both of 99Tc and 90Sr. It is to be understood, however, that the invention contemplates additional embodiments where these systems, devices, and methodologies are adapted for alternative nuclides.
Systems, devices, and methods of the invention enable collection, concentration, detection and monitoring of radionuclides without performing “grab-samples” and offsite analysis.
Any device described may have a composite structure which contains a polymer, a fluorescent agent, such as a fluorescent organic scintillator, and a chemical extractant, which is referred to as a ligand. The polymer may be a macroporous polymer that is doped with an organic fluorescent agent to become a scintillating polymer. The macroporous polymer can be, for example, polyvinyltoluene, polymethylmethacrylate or polystyrene.
An organic ligand is sequestered within the macroporous polymer. Such ligand will be specific for the isotope of interest and will be chosen based upon its selectivity for the element of interest in the given environment conditions. For example, ALIQUAT® 336 may be utilized as a ligand to separate and concentrate 99Tc (in the form of 99TcO4−) in various types of aqueous environments, which may contain other man-made or naturally occurring radionuclides.
The composite structure 12 is synthesized utilizing a mixture consisting of a solvent, a monomer, an organic scintillator, and a ligand. The monomer is then polymerized to form a plastic containing the scintillator and ligand. The polymerization method forms a macroporous solid having numerous channels and voids allowing liquid transport therethrough. The polymer may be formed into small beads, thin films, strips, and/or blocks. Alternatively, the polymer may be dissolved utilizing a solvent, the ligand added, with solidification of the polymer and ligand in a water bath.
For the present invention, suitable scintillators include anthracene and stilbene. In some instances p-terphenyl activated with diphenylbutadiene may be used. In some instances it may be preferable to add an additional compound during polymerization of the composite structure as a wavelength shifter to provide an emission spectrum to match the spectral response of a photomultiplier tube (PMT).
An organic ligand is used to capture the radioisotope while the scintillating polymer is used as a plastic scintillation detector. Such a configuration allows the radioisotope to be concentrated inside the actual detector, providing high counting efficiency while concentrating the radioisotope for a desired period when very low detection capability is desired. The kinetic energy of the particle decay (alpha or beta) causes electron excitation in the organic scintillating molecules, which then releases fluorescent energy as the electrons in the molecules return to a ground state.
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Where device 100 is to be used in an aqueous environment, composite 112 may be encased in a housing 122. Housing 122 preferably comprises a thin easily formed material. Typical materials used for housing 122 include but are not limited to aluminum and stainless steel. Any surfaces of the housing 122 that may contact the polymer may be coated and polished to provide a reflective surface.
Housing 122 includes an inlet port 117 and an outlet port 119 made of any convenient non-reflective material. While the relative location of the passageway 114, inlet 117 and outlet 119 are for convenience, it is desirable to configure the housing 122 to minimize light transmission and/or reflection. For example, it is desirable to have inlet port 117 and outlet port 119 located at right angles relative to one another on the housing 122. Ports 117 and 119 may be constructed of non-reflective, corrosion resistant material such as, for example, polyethylene (PE), high density polyethylene (HDPE), low density polyethylene (LDPE), etc.
The device 100 illustrated in
When the device 100 is used in an aqueous environment, water can be made to flow by gravity or pumping through the housing 122. The radionuclide collection and/or concentration can comprise binding the radionuclide to the ligand sequestered within the polymer and scintillator. Particle decay (alpha or beta) then causes electron excitation in the fluorescent organic scintillating molecule. Fluorescent energy is then released and can be detected as a fluorescent signal.
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In particular embodiments, system 200 can comprise two photomultiplier tubes 250, 252 attached directly to the housing 222 and disposed 180° with respect to each other. A photodiode may also be utilized in conjunction with each PMT (not shown).
The system 200 additionally includes appropriate suitable conventional telemetry to provide remote monitoring and data transmission capability. System 200 includes, for example, a transmitter 260 having antenna 262. Such can emit data signals 280 which can be passed by a transponder such as a satellite transponder 282 by retransmitted signal 284. A receiver 270 having receiving antenna 272 can receive the retransmitted signal and can provide for data viewing by the end user. Typically the data signal 280 will be encrypted and receiver 270 will have decryption capabilities.
When using system 200, the output of the photomultiplier tube(s) 250, 252 can be amplified to increase an initial fluorescent signal. A photodiode or alternative photo detector may also be utilized. The electronic signal from the PMT can be transmitted to an end user at a desired location.
The systems, devices, and methods of the invention avoid the need for obtaining grab samples and the time and expense of transporting such samples to distant sites for analysis since real-time data analysis is afforded by the present system. Additionally, the devices of the invention can be adapted for a particular environment and tailored to specific radionuclides. Accordingly, devices, systems and methods of the invention can be highly advantageous relative to conventional techniques and devices.
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The system 200 additionally includes appropriate suitable conventional telemetry to provide remote monitoring and data transmission capability. System 200 includes, for example, a transmitter 260 having antenna 262. Such can emit data signals 280 which can be passed by a transponder such as a satellite transponder 282 by retransmitted signal 284. A receiver 270 having receiving antenna 272 can receive the retransmitted signal and can provide for data viewing by the end user. Typically the data signal 280 will be encrypted and receiver 270 will have decryption capabilities.
When using system 200, the output of the photomultiplier tube(s) 250, 252 can be amplified to increase an initial fluorescent signal. A photodiode or alternative photo detector may also be utilized. The electronic signal from the PMT can be transmitted to an end user at a desired location.
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Device 100 comprises two photomultiplier tubes 250, 252 attached directly to the housing 222 and disposed 180° with respect to each other and scintillating plate 20 having a scintillator coating 24 thereon as described herein for the water from the well to flow thereover. The PMT(s) converts fluorescent light energy to electrical energy. As mentioned above, composition 212 can include another compound which may be a wavelength shifter to tailor the emission spectrum to match the spectral response of the PMT. A photodiode may also be utilized in conjunction with each PMT (not shown).
The system 200 additionally includes appropriate suitable conventional telemetry to provide remote monitoring and data transmission capability. System 200 includes, for example, a transmitter 260 having antenna 262. Such can emit data signals 280 which can be passed by a transponder such as a satellite transponder 282 by retransmitted signal 284. A receiver 270 having receiving antenna 272 can receive the retransmitted signal and can provide for data viewing by the end user. Typically the data signal 280 will be encrypted and receiver 270 will have decryption capabilities.
When using system 200, the output of the photomultiplier tube(s) 250, 252 can be amplified to increase an initial fluorescent signal. A photodiode or alternative photo detector may also be utilized. The electronic signal from the PMT can be transmitted to an end user at a desired, predetermined location.
It is to be understood that the inventions herein are not limited to the specific features shown and described herein. The invention is, therefore, claimed in any of its forms or modifications within the proper scope of the appended claims appropriately interpreted in accordance with the doctrine of equivalents.
The United States Government has certain rights in this invention pursuant to Contract No. DE-AC07-05ID14517 between the United States Department of Energy and Battelle Energy Alliance, LLC.
