cæsium / cesium

Et alkalimetal, der er det 55. grundstof i det periodiske system. Cæsium udvindes bl.a. i Canada, Namibia og i Zimbabwe.
Metallet bruges bl.a. i atomure og i atomkraftindustrien.
Cæsium 137 er et radioaktivt isotop af cæsium, som er formet som et fissionsprodukt ved nuklear fission, eksempelvis i atomkraftværker og ved atomvåbenforsøg.
/ An alkali metal, which is the 55th chemical element of the Periodic Table. Cesium is mined inter alia in Canada, Namibia and Zimbabwe. The metal is used particularly in atomic clocks and in the nuclear power industry.
Cesium 137 is a radioactive isotope of cesium, which is shaped as a fissionable product by nuclear fission, for example, in nuclear power plants and by nuclear-weapons testing.

Litteratur

Butterman, William C.; Brooks, William E.; Reese, Jr., Robert G. (2004). Mineral Commodity Profile: Cesium.
United States Geological Survey. - http://pubs.usgs.gov/of/2004/1432/2004-1432.pdf
US Department of the Interior: Fish and Wildlife Service: Endangered and Threatened Wildlife and Plants; 12-Month Finding on a Petition to List the Pacific Walrus as Endangered or Threatened. Federal Register / Vol. 76, No. 28 / Thursday, February 10, 2011 / Proposed Rules. - 46 s.
'We, the U.S. Fish and Wildlife Service, announce a 12-month finding on a petition to list the Pacific walrus (Odobenus rosmarus divergens) as endangered or threatened and to designate critical habitat under the Endangered Species Act of 1973, as amended'.
'Radionuclide (a radioactive substance) sources include atmospheric fallout from Chernobyl, nuclear weapons testing, and nuclear waste dumps in Russia'.
'It is projected that Cesium 137 from nuclear weapons testing fallout and Chernobyl may be liberated from storage in trees as the incidence of forest fires increases due to climate change'
Cesium-137 deposition and contamination of Japanese soils due to the Fukushima nuclear accident. / Teppei J. Yasunaria et al. PNAS. December 6, 2011. vol. 108. no. 49. - http://www.pnas.org/content/108/49/19530.full.pdf+html
Long-Term Reduction in 137Cs Concentration in Food Crops on Coral Atolls Resulting from Potassium Treatment. / W. Robison, E. Stone, T. Hamilton, C. Conrado.
Journal of Environmental RadioactivityVolume: 88; Journal Issue: 3. April 11, 2005.
'Bikini Island was contaminated March1, 1954 by the Bravo detonation (U.S nuclear test series, Castle) at Bikini Atoll. About 90% of the estimated dose from nuclear fallout to potential island residents is from cesium-137 (137Cs) transferred from soil to plants that are consumed by residents. Thus, radioecology research efforts have been focused on removing 137Cs from soil and/or reducing its uptake into vegetation.'
Migration of conservative and sorbing radionuclides in heterogeneous fractured rock aquifers at the Nevada Test Site. / Boryta, J. R.; Wolfsberg, A. V.
American Geophysical Union, Fall Meeting 2003, abstract #H11G-0935
The Nevada Test Site (NTS) is the United States continental nuclear weapons testing site. The larger underground tests, including BENHAM and TYBO, were conducted at Pahute Mesa. The BENHAM test, conducted in 1968, was detonated 1.4 km below the surface and the TYBO test, conducted in 1975, was detonated at a depth of 765 m. Between 1996 and 1998, several radionuclides were discovered in trace concentrations in a monitoring well complex 273 m from TYBO and 1300 m from BENHAM. Previous studies associated with these measurements have focused primarily on a) plutonium discovered in the observation wells, which was identified through isotopic finger printing as originating at BENHAM, b) colloid-facilitated plutonium transport processes, and c) vertical convection in subsurface nuclear test collapse chimneys. In addition to plutonium, several other non-, weakly-, and strongly-sorbing radionuclides were discovered in trace concentrations in the observation wells, including tritium, carbon-14, chlorine-36, iodine-129, technetium-99, neptunium-237, strontium-90, cesium-137, americium-241, and europium-152,154,155. The range in retardation processes affecting these different radionuclides provides additional information for assessing groundwater solute transport model formulations. For all radionuclides, simulation results are most sensitive to the fracture porosity and fracture aperture. Additionally, for weakly sorbing Np, simulation results are highly sensitive to the matrix sorption coefficient. For strongly sorbing species, migration in the absence of colloids can only be simulated if fracture apertures are set very large, reducing the amount of diffusion that can occur. For these species, colloid-facilitated transport appears to be a more likely explanation for the measurements. This is corroborated with colloid-transport model simulations.'
Whitcomb, Robert Cleckley, Jr.: Reconstruction and analysis of cesium-137 fallout deposition patterns in the Marshall Islands. University of Florida, 2000.
Determining Sources and Transport of Nuclear Contamination in Hudson River Sediments with Plutonium, Neptunium, and Cesium isotope ratios. / Kenna, T. C.; Chillrud, S. N.; Chaky, D. A.; Simpson, H. J.; McHugh, C. M.; Shuster, E. L.; Bopp, R. F.
American Geophysical Union, Fall Meeting 2004, abstract #H41I-05
'Different sources of radioactive contamination contain characteristic and identifiable isotopic signatures, which can be used to study sediment transport. We focus on Pu-239, Pu-240, Np-237 and Cs-137, which are strongly bound to fine grained sediments. The Hudson River drainage basin has received contamination from at least three separate sources: 1) global fallout from atmospheric testing of nuclear weapons, which contributed Pu, Np and Cs; 2) contamination resulting from reactor releases at the Indian Point Nuclear Power Plant (IPNPP) located on the Hudson River Estuary ˜70km north of New York Harbor, where records document releases of Cs-137; 3) contamination resulting from activities at the Knolls Atomic Power Laboratory (KAPL) located on the Mohawk River, where incomplete records document releases of Cs-137 but no mention is made of Pu or Np. Here we report measurements of Pu isotopes, Np-237 and Cs-137 for a series of sediment cores collected from various locations within the drainage basin: 1) Mohawk River downstream of KAPL, 2) Hudson River upstream of its confluence with the Mohawk River, and 3) lower Hudson River at a location in close proximity to IPNPP. In addition, we present data from selected samples from two other lower Hudson River locations: One site located ˜30km downstream of IPNPP and another ˜30km upstream of IPNPP. By comparing the isotopic ratios Pu-240/Pu-239, Np-237/Pu-239, and Cs-137/Pu-239, measured in fluvial sediments to mean global fallout values, it is possible to identify and resolve different sources of non-fallout contamination. To date, isotopic data for sediments indicate non-fallout sources of Pu-239, Pu-240, and Cs-137; Np-237, however, appears to originate from global fallout only. Mohawk River sediments downstream of KAPL exhibit enrichments in Pu-239, Pu-240, and Cs-137 that are 7 to 20 times higher than levels expected from global fallout as indicated from Np-237. The elevated levels, non-fallout isotopic signatures, and core location are all consistent with KAPL being a source of Pu and Cs isotopes. Sediments from upper Hudson River and a section of the lower Hudson Estuary both contain Cs-137 levels that are more than twice that expected from global fallout. While elevated Cs-137 in selected lower Hudson samples is consistent with reported reactor releases from IPNPP, there is no known source of non-fallout Cs in the upper Hudson. We have been able to estimate end-member isotopic compositions of radionuclides originating from KAPL as well as detect its presence and estimate its contribution to contaminant inventories far downstream in tidal Hudson sediments. By comparing KAPL-derived Pu-239 inventories measured in the Mohawk and Lower Hudson Rivers, we estimate a dilution factor of ˜140.


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