Plutonium Ratios Research Articles

Modelling the Sorption of Actinides onto Cement: An Approach with the Surface Co-Precipitation Model

ABSTRACTAn approach, assuming that co-precipitation on the surface of the cement phase dominates ‘sorption’, is proposed and discussed to interpret the sorption behaviour of the cement-complex system. This model takes account of the mineralogical composition of Ordinary Portland Cement (OPC) and assumes that Calcium Silicate Hydrates (C-S-H) dominates the sorption (fixation) of actinide onto OPC and that a small amount of surface co-precipitation of actinides with calcium hydroxide in the structure of C-S-H is formed during the late period of the fixation process. Therefore, this will be referred to as the ‘Surface Co-Precipitation Model (SCPM)’. The modelling results show generally good agreement between the predicted and measured distribution ratios of plutonium, thorium and neptunium, of which the dominant species in high pH solution are neutral species, on OPC.

The distribution and history of nuclear weapons related contamination in sediments from the Ob River, Siberia as determined by isotopic ratios of plutonium and neptunium

Isotopic ratios of Pu and Np measured in sediment cores from 5 locations in the Ob River drainage basin show clear evidence of input from sources other than global fallout (non-fallout sources). Historical contaminant records obtained by combining isotopic ratio information with chronological information indicate that non-fallout inputs are from several sources that have varied significantly over the past 50 years. Unique isotopic signatures observed in sediments from tributaries that drain areas containing known or suspected sources of non-fallout contamination are used to identify the source of materials in sediments collected at downstream locations. These data can lead to a better understanding of the transport behavior, fate, and relative importance of particle reactive, weapons related contaminants originating from the nuclear facilities Mayak, Tomsk-7, and Semipalitinsk, which lie within the drainage basin. From our work to date, we draw the following conclusions: (1) Persistent non-fallout contamination is observed in the Ob River above its confluence with the Irtysh River, indicating contamination from the Tomsk-7 facility. (2) Non-fallout contamination in the Tobol River above its confluence with the Irtysh River indicates contamination from the Mayak facility. (3) Non-fallout contamination in the Irtysh River above its confluence with the Tobol River indicates contamination from the Semipalitinsk weapons test site. (4) The occurrence of isotopic ratios in Ob Delta sediments that are similar to those observed in source tributaries suggests that contamination from at least two sources has been transported along the length of the river system. (5) Global fallout, a result of high-yield atmospheric weapons tests conducted by the FSU and USA primarily, is the dominant source of Pu and Np to the region; however, there have been brief periods when inputs from non-fallout sources exceeded those from global fallout.

Hot particles of the Yenisei River flood plain, Russia

Some high-activity hot particles (HP) were found in the flood plain of the Yenisei River, near the Krasnoyarsk Mining-and-Chemical Combine (MCC), and their radionuclide compositions were determined. The ratios of plutonium and caesium isotopes in the particles are indicative of their reactor origin. The 137Cs activity of the particles amounts to 29,200 kBq/particle, which is higher than the corresponding activities of the fuel particles that formed as a result of the accident at the Chernobyl NPP. All the particles have been divided into two major groups according to the 137Cs/ 134Cs ratio: in the first group, the 137Cs/ 134Cs ratio is more than or equal to 3000, and in the second the 137Cs/ 134Cs ratio is less than or equal to 1000. The particles of the first and the second groups were preliminarily estimated to be formed 30 and 20 years ago, which suggests that there must have been at least two accidents at the MCC reactors, with part of the fuel released into the Yenisei River.

240Pu/ 239Pu isotopic ratios and 239+240Pu total measurements in surface and deep waters around Mururoa and Fangataufa atolls compared with Rangiroa atoll (French Polynesia)

The average values of 240Pu/ 239Pu mass isotopic ratios of plutonium deposited in Mururoa and Fangataufa atoll sediments by French atmospheric nuclear tests range from 3.5 to 5%. In order to assess the near field and far field influence of those deposits in the open ocean, two water profiles were measured for 239+240Pu and 240Pu/ 239Pu using, for the first time, an Inductively Coupled Plasma Mass Spectrometer which was developed to achieve femtogram detection limits. One site was located at the limit of the French territorial waters, which is 22 km distant from Mururoa. The second site was located close to Rangiroa atoll, at a distance of approximately 1200-km from French nuclear test sites. The sample volumes were approximately 500 litres and plutonium was purified prior to mass spectrometry and alpha spectrometry measurements. In Rangiroa, the 239+240Pu profile is comparable with those already determined in world open oceans but the maximum detected activity, 9 mBq/m 3 at 500–600 m is a lot lower than those measured in the northern hemisphere. 240Pu/ 239Pu ratios were measured between 500 and 1000 m and were not statistically different from the typical 0.18±0.01 ratio which characterises the global fallout. Consequently, any influence of plutonium from the tests in Mururoa and Fangataufa is not apparent at Rangiroa. The vertical distribution of 239+240Pu near Mururoa shows similar changes with depth but with a slight increase in concentration. 240Pu/ 239Pu mass ratios vary with depth, from 7 to 10% in the upper 500 m and in the deep waters (below 1000 m) to 15–16% between 600 and 1000 m. A contribution from plutonium deposited in the sediments at Mururoa and Fangataufa is observed at the limit of territorial waters, especially in surface and deep waters.

The effect of temperature on the extraction of plutonium(VI) from nitric acid into dodecane by di(2-ethylhexyl)sulphoxide

The effect of temperature on the extraction of plutonium(VI) into dodecane by di(2-eth-ylhexyl)sulphoxide (DEHSO) has been investigated as a function of temperature in the range 25–50°C using a wide range of concentrations of both nitric acid as well as DEHSO. The results show that the distribution ratios of plutonium(VI) considerably decrease with increasing temperature. From the variation of the distribution ratio ( D pu) with temperature, the thermodynamic parameters such as the free energy (Δ G), enthalpy (Δ H), and entropy (Δ S) changes associated with the formation of PuO 2(NO 3) 2·2DEHSO have been evaluated following a least squares method. Extraction of plutonium(VI) from nitric acid by DEHSO is invariably exothermic in nature and is mainly enthalpy controlled, the entropy change counteracting in all cases. Values of Δ H are not much affected by increase in nitric acid concentration. Negative values of Δ S are indicative of a smaller entropy gain due to loss of hydration water molecules compared to entropy loss due to complex formation.

Plutonium-244 dating I. Initial ratio of plutonium to uranium in the allende meteorite

Re-examination of all known xenon isotope data for the carbonaceous chondrite Allende reveals that this meteorite contains as much as (22±1)·10−1 2 csSTP per gram of fissogenic136Xe (136fXe) from the extinct nuclide244Pu and it appears to have started to retain its xenon more than 4800 million years ago, when the244Pu to238U ratio in the solar system was 0.113±0.006 (atom/atom).

Determination of isotopic ratios of plutonium and curium by internal conversion electron spectrometry

The isotopic ratios240Pu/239Pu in plutonium samples purified freshly and allowed to stand for a long time were determined by using a high resolution internal conversion electron spectrometer. As a result, it was proved that the above ratios can be determined accurately and precisely. The method was also examined further through a similar determination with curium samples.

Studies on the adsorption of plutonium (IV) on alumina from phosphoric acid-nitric acid solution

Results of experiments on the adsorption of plutonium (IV) on alumina and their application to the recovery of plutonium from analytical waste solutions containing phosphoric-nitric acid are reported. Distribution ratios of plutonium (IV) between alumina and solutions containing varying concentrations of phosphoric acid and nitric acid are determined. The influence of various ions like UO22+, Fe3+, MoO42−, VO2+ and SO42− on the distribution ratio is evaluated. Saturation values of adsorption of plutonium (IV) on alumina and optimum conditions for loading and elution of plutonium on a column packed with alumina are described.

Origin and isotopic ratios of plutonium in the Barents and Greenland Seas

Isotopic ratios 238Pu/ 239 + 240Pu and 241Pu/ 239 + 240Pu vary depending on the source of the Pu. The values for samples contaminated from distinct sources can be compared with those affected only by global fallout. The present study reports isotopic ratios determined radiochemically in samples collected in the Barents and Greenland Seas during the Swedish Arctic Expedition “YMER 80”. Long-range transport and transfer factors of plutonium from European nuclear fuel reprocessing facilities into the Arctic Ocean were evaluated. About 80% of the plutonium released in dissolved form from such facilities is removed by sedimentation processes before reaching the Barents and Greenland Seas.

A gamma-spectrometric method for the determination of plutonium isotope ratios

A gamma-spectrometric method using an intrinsic high resolution germanium detector has been developed for the determination of isotope ratios of plutonium from samples in solution form. The method is based on the assay of low energy gamma-rays of238Pu,239Pu,240Pu and241Pu and does not require the use of branching intensities or the knowledge of detection efficiencies for different gamma rays. Since low energy gamma-rays are used, the effect of241Am has also been studied. It is found that results are not affected up to 0.5 wt% of241Am in plutonium samples. An accuracy of 3% is achievable in the determination of240Pu/239Pu and241Pu/239Pu atom ratios as demonstrated by carrying out measurements on isotopic standards of plutonium.

Retention of Plutonium and Americium by Rock

The relative migration ratio of plutonium in various rocks is approximately 100 micrometers per meter of water flow; the corresponding migration ratio for americium is about 500 micrometers per meter of water flow. Under these conditions radioactive decay will have taken place to such an extent that little plutonium and americium can reach the external environment from a well-designed and isolated geological repository site.

Retention of Plutonium and Americium by Rock

The relative migration ratio of plutonium in various rocks is approximately 100 micrometers per meter of waterflow; the corresponding migration ratio for americium is about 500 micrometers per meter of water flow. Under these conditions radioactive decay will have taken place to such an extent that little plutonium and americium can reach the external environment from a well-designed and isolated geological repository site.

Etude compar�e des teneurs en plutonium chez divers mollusques de quelques sites littoraux fran�ais

Plutonium contents of various species of molluscs sampled from several sites along the French coast were measured in order to reveal any distributional patterns of the plutonium levels. The influence of the La Hague nuclear fuel reprocessing plant was apparent in the immediate proximity of the waste-disposal outfall (Ecalgrain Bay), and to a lesser degree in an oyster farming center situated about 50 km east of the Bay of Ecalgrain (St. Vaast-la-Hougue). Plutonium concentrations in molluscs from the remaining sites were quite comparable to levels that have been measured in similar species subject only to plutonium derived from atmospheric fallout. All molluscs, except those from Ecalgrain Bay, displayed higher levels of plutonium in the shell than in the soft parts, a finding in agreement with similar studies which have been reported recently. However, those individuals sampled from the vicinity of the outfall consistently displayed shell: soft parts plutonium ratios of less than 1. This difference may reflect different physico-chemical forms of this isotope present at the different sampling stations. With the exception of Crepidula fornicata shell, the tissues of filter-feeding molluscs do not appear to concentrate plutonium above the level found in other types of molluscs.

The gamma-spectrometric determination of [formula omitted] ratios and its application to fuel burn-up

High resolution gamma-spectrometry was applied to determine the 241Pu/ 239Pu isotopic ratios in plutonium bearing fuels. The photopeaks at 129, 148 and 208 keV were utilized. From the 241Pu/ 239Pu ratio, the integrated neutron flux and the burn-up can be calculated. The method has been tested by comparing the results obtained from uranium and plutonium ratios in a Pu/U fuel.

Americium and plutonium urine excretion following acute inhalation exposures to high-fired oxides.

Abstract Twenty-five persons incurred measurable inhalation exposures during a plutonium fire in 1965. Exposures ranged up to 17 times the maximum permissible lung burden as estimated by whole-body counting. Urine excretion of americium and plutonium was studied for six months following the accident. The ratio of plutonium to americium alpha activity in the urine averaged 1.5-1. The exposure material initially contained an alpha ratio of 11-1 plutonium to americium. There was no apparent change in this ratio with time during the period of study. Typical excretion curves for subjects treated with DTPA and for nontreated subjects are discussed.

The Occurrence of Plutonium in Nature

Plutonium has been chemically separated from seven different ores and the ratios of plutonium to uranium determined. This ratio was found to be fairly constant in pitchblende and monazite ores, in which the uranium content varied from 50% t o 0.24%, and substantially less in carnotite and fergusonite.