Beta and Gamma Activity Indicator for Ground Water
Development and Test of the Beta-, Gamma-Activity Indicator of the Radioactive Subterranean Waters
Tech Area / Field
- INS-DET/Detection Devices/Instrumentation
- ENV-MIN/Monitoring and Instrumentation/Environment
- ENV-WPC/Water Pollution and Control/Environment
3 Approved without Funding
VNIITF, Russia, Chelyabinsk reg., Snezhinsk
- MIFI, Russia, Moscow\nNPO Mayak, Russia, Chelyabinsk reg., Oziorsk
- University of Oklahoma / Institute for Science and Public Policy, USA, OK, Norman
Project summaryNuclear power engineering as well as radiochemical industries use water. After fuel is burnt up in the reactor core, fuel elements are kept in water pools for several years. After deep decontamination and monitoring, technological water is released into open hydrological net. Liquid and solid radioactive wastes (RW) are disposed in burial grounds. Leakage of radioactive materials and contaminated water into the Environment, including sewage and ground water, is possible due to imperfection of technological equipment, its wear, as well as loss of sealing in RW-bearing tanks (corrosion of structural materials), and in the case of accidents. History of atomic industry gives many examples of such situations, both local, regional (1957 accident at the chemical plant «MAYAK», at the nuclear power station in Three Mile Island (USA)), and global – accident at the Chernobyl nuclear power station in 1986. Thus, monitoring is very critical in the case of standard operation of nuclear industry facilities with the purpose to monitor their effect onto the Environment, and to timely detect accident releases, as well as after any emergency with the purpose to track its consequences.
Fission fragments, being products of nuclear power stations (NPS) and radiochemical facilities, are basic sources of radioactive contaminants of the Environment. Most hazardous are long-lived isotopes – Sr90 and Cs137 that mostly yielded during fission. Both isotopes are b-active, and Cs137 also emits g-quanta with energy Еg = 662 keV. The basic way of Sr90 propagation is water. Being the chemical analog of calcium, which is the constituent of practically all rocks, strontium in the ionic form migrates in ground water practically without delay.
In order to determine water activity one usually uses samples taken from geophysical holes drilled around potentially hazardous sites (burial grounds and atomic power stations). Monitoring procedure, from sampling till the moment when measurement results are analyzed, can take several days. Thus, after the procedure of extraction and evaporation, radiation equilibrium between Sr90 and Y90 gets violated. Correct determination of Sr90 activity by b-radiation requires certain time (~10 days) in order radiation equilibrium could be established. Number of holes can reach hundreds. It is necessary to analyze samples taken at different depth. Expensive and often toxic chemical reagents are used for nuclides isolation. Therefore, monitoring of ground waters using radiochemical methods is associated with great number of expensive analysis.
Monitoring can be simplified through application of the device, which allows assessment of b,g-contamination of water directly in a hole, i.e. without sampling. After radiochemical monitoring of the hole, the necessity in the repeated monitoring is conditioned by changes/presence of b,g-activity registered by the device that is constantly found in the hole or downloaded in a hole periodically. If results of radiochemical analysis give information about isotopic composition of radionuclides migrating with ground water, then analysis can be repeated in exceptional cases, and radiometer can be used for contamination level monitoring.
Goal of the Project proposal is to develop and test the indicator of b,g-activity in ground water on the basis of proportional thin-walled counters. This indicator will allow sampling-free measurements directly in holes at different depth down to 130 m.
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