Development of gamma-ray/x-ray spectrometric methods for monitoring the contamination of soil with241Am and Pu

Abstract

The principal sources of plutonium and americium entering the environment are tests of nuclear weapons, the accident at the Chernobyl nuclear power station, and discharges from radiochemical factories. It is necessary to monitor the contamination of soil these produce from the levels caused by global radioactive fallout. The 241pu content in plutonium contaminating soil can vary by an appreciable factor (see Table I). This determines the contribution of 241Anl to the total c~ activity of the soil or of a sample prepared from it.The constancy of the ratio Apu/AAm on contaminated territory is of great importance for the introduction of -r/x-ray spectrometric methods. The number of analyses required for its determination depends on this. According to data in [4][5][6] plutonium is present in soil in various forms: water-insoluble, exchange, mobile, etc. The ratios between these forms differ depending on the content of organic matter, the pH of the medium, the composition of the soil minerals, and other factors. The rate of migration of plutonium is influenced by the conditions of the landscape geochemistry and the intensity of the microbiological processes.In soil samples selected from the accident zone at the Chernobyl nuclear power station, the presence of radionuclides was discovered in particles of destroyed nuclear fuel, aggregates of fuel particles with reactor graphite, and bituminous carbon and secondary radioactive particles [7]. Fuel particles are almost insoluble in aqueous solutions, but as they decompose the radionuclides pass into a mobile state. According to data from natural investigations of the migration of plutonium in soil following an accident in the South Urals in 1957, the rate of such migration and the nature of the plutonium distribution hardly differ from those established in the accident zone at the Chernobyl nuclear power station [8].Although the behavior of americium in natural media is less well studied than that of plutonium, it is considered that the laws governing the migration of plutonium also characterize that of americium [9] According to data in [10] which were obtained in a zone adjacent to the Chernobyl nuclear power station, the ratio between the concentrations of 241Am and 239pu + 24~ in the soil corresponded to their average ratio in the reactor fuel at the time of the accident, i.e.. no influence of migration was discovered. However, one cannot completely ignore the possible influence of migration on the ratio Ar,u/AAm and one must include a determination of this ratio for several samples from different sections when planning to investigate new territories.A radiochemical method is normally used for quantitatively determining plutonium in the environment. This includes the stages of selecting and preparing a sample, splitting it up, initially extracting and subsequently separating the plutonium from other elements, preparing a thin sample, and measuring its tx radiation in counter or spectrometric regimes. The plutonium from the soil samples is extracted either by leachin...

Depth profiling of Pu, 241Am and 137Cs in soils from southern Belarus measured by ICP-MS and ? and ? spectrometry

“…The E c ~59.6 keV 241 Am emission line was used as described elsewhere. 13 Determinations of 137 Cs and 134 Cs were performed via gamma-lines with energies of 661.66 keV and 604.7 keV, respectively. The 137 Cs-134 Cs spectrometer was equipped with a DGDK-80B-3 semiconductor detector (Aspect Ltd., Dubna, Russia).…”

“…Precipitation of iron hydroxide from alkali-treated solution of soils for 241 Am measurement via gamma-spectrometry was performed as described elsewhere. 13 In addition, a digestion of soil samples with potassium pyrosulfate preparation procedure was performed for ICP-MS determinations of 2391240 Pu activities at Northern Arizona University. Approximately 0.30-0.35 g of ashed soil were mixed with 1.0-1.1 g of potassium pyrosulfate in a 40 ml borosilicate glass vial.…”

Reagent-based remediation of soil contaminated with transuranium elements

“…In contrast to the α-spectrometric method, it does not require prolonged, preliminary radiochemical preparation of the sample [5]. The express-analysis [6] is based on total plutonium isotope determination according to the x-rays which they emit and γ-spectrometric measurement of 241 Am [7,8]. For plutonium, the XL β line, corresponding to the energy 17.2 keV of the characteristic L-series radiation of uranium UL β , with the highest radiation yield was used.…”