Thermo Alpha Monitor
Effluent waters leaving contaminated Department of Energy (DOE) sites sometimes contain alpha-emitting radioisotopes, such as Uranium-238, Uranium-234, and Plutonium-239. These radioisotopes are carcinogens regulated by the U.S. Environmental Protection Agency (EPA). Currently, surface and ground waters at contaminated DOE sites are monitored for alpha emitters (and other contaminants) by intermittent sampling, with analysis at a central laboratory. Shortcomings of the current approach include spikes (high, intermittent values) that are often undetected, a long time delay between sampling and data availability, and multiple handling and processing steps that make this approach susceptible to errors and mistakes.
A newly developed tool called the Thermo Alpha Monitor (TAM) has been developed to detect and analyze alpha-emitting radionuclides. In demonstrations, it has been proven to accurately measure naturally occurring and transuranic alpha emissions. The technology provides an on-line, in-situ method of collecting and concentrating dissolved radionuclides on a solid surface, with rapid quantification of specific, alpha-emitting particles. The TAM uses a solid-state, semiconductor counter. These counters are similar in concept to ionization chambers, and they offer advantages in the detection of radiation, particularly alpha particles. The energy lost by ionizing radiation, such as alpha particles, in semiconductor detectors results in the formation of ions. Under the influence of the imposed electric field, these ions drift to the contacts of opposite polarity, producing a short-duration (nanosecond) flow of electrical current. Additionally, the monitor provides greater control and assurance of final remediation level compliance and ALARA (As Low As Reasonably Achievable) compliance by reducing worker exposure to waste streams, as well as to chemicals in laboratory analysis.
Limitations and Concerns
TAM results must now be verified to be accepted by regulators. However, field experience with the monitor may eventually eliminate the need for “check” samples. The developer of this technology needs to understand better the underlying chemistry of the Thermo Alpha Monitor through additional laboratory and/or field tests. Methods for analyzing water streams need to be peer-reviewed and agency-approved. It is not clear how durable the monitor is, and if results will be accurate after several uses.
This technology provides nearly real-time analysis of radionuclides that emit alpha particles. It is currently designed for groundwater and surface water. In the future, the developer hopes that this technology will be able to detect alpha radiation from solid samples, non-aqueous liquids, gas streams, and solid surfaces.
Technology Development Status
The technology is in the demonstration phase of development.
Other Resources and Demonstrations
See http://www.xrfcorp.com/technology/radiation_detection.html for a description of common radiation detection methods. Field testing of the TAM was conducted at several locations within Oak Ridge National Laboratory (ORNL). Tests were conducted to evaluate the response of the instrument to a range of water chemistries, contaminant concentrations, and radioisotopes. Tests were conducted utilizing surface water, groundwater, and process waters to detect alpha emitters, primarily uranium, in a “near real time,” automated mode. The TAM was successfully demonstrated on water with radiation concentrations less than one hundredth of U.S. EPA’s proposed safe drinking water limit—i.e., less than 1 picoCurie per liter (pCi/l).
See http://www.clu-in.org/download/char/402-r-06-007.pdf for an inventory of radiological technologies. This document also explains the basic science behind various methods of radiation detection.