Nuclear-waste monitoring gets close to the source. (Analytical Chemistry).Some forms of nuclear radiation--such as the beta-emission from radioactive technetium-99--are particularly difficult to detect underground, partly because the radiation doesn't travel very far. A new prototype instrument may make this and other elements easier to trace in groundwater. Technitium-99 is produced during nuclear-reactor operation and nuclear-weapons production. It has a half-life of 212,000 years, and once it finds its way into groundwater it moves quickly, says analytical chemist Oleg Egorov of the Pacific Northwest National Laboratory The Pacific Northwest National Laboratory (PNNL) is one of nine United States Department of Energy (DOE) multiprogram national laboratories. The laboratory PNNL is located in Richland, Washington, and operates a marine research facility in Sequim, Washington. in Richland, Wash. For these reasons, this isotope isotope (ī`sətōp), in chemistry and physics, one of two or more atoms having the same atomic number but differing in atomic weight and mass number. The concept of isotope was introduced by F. needs to be carefully monitored in places such as the Hanford Site The Hanford Site is a facility of the government of the United States established to provide plutonium necessary for the development of nuclear weapons. It was established in 1943 as the Hanford Engineer Works, part of the Manhattan Project, and codenamed "Site W. , near Richland, where nuclear weapon materials were produced from the 1940s to the 1980s. Currently, researchers take groundwater samples from Hanford wells to a lab for a tedious analysis. If the water could be monitored by small detectors left inside the wells, analyses would be cheaper and quicker. Also, the containers now used to transport the well-water samples have to be treated as hazardous waste Hazardous waste Any solid, liquid, or gaseous waste materials that, if improperly managed or disposed of, may pose substantial hazards to human health and the environment. Every industrial country in the world has had problems with managing hazardous wastes. themselves, an issue that would disappear with in-well monitoring, says Egorov. "Our goal is something that you can take into the field and leave there," he says. Egorov and his coworkers have taken a step in that direction by building a prototype detector that monitors technitium-99 concentrations. The apparatus is roughly 1 meter long and contains a column packed with an absorbent absorbent /ab·sor·bent/ (-sor´bent) 1. able to take in, or suck up and incorporate. 2. a tissue structure involved in absorption. 3. a substance that absorbs or promotes absorption. material and so-called scintillation scintillation /scin·til·la·tion/ (sin?ti-la´shun) 1. an emission of sparks. 2. a subjective visual sensation, as of seeing sparks. 3. beads. When water tainted taint v. taint·ed, taint·ing, taints v.tr. 1. To affect with or as if with a disease. 2. To affect with decay or putrefaction; spoil. See Synonyms at contaminate. 3. with technetium-99 passes through the column, the isotope gets trapped by the absorbent material. Then the emitted beta-particles--high-speed electrons--hit the scintillation beads, which respond by emitting light that's picked up by sensors at either end of the column. The data can be transmitted to a computer as far as several miles away, says Egorov. The researchers have proven the detector's effectiveness in laboratory tests. They now plan to make their system more rugged so they can deploy it in a Hanford well by the end of next year.--J.G. |
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