Widely present in the mixed wastes at the Hanford site, ethylenediametetraaceticacid (EDTA) can solubilize radionuclides such as plutonium and may increasetheir mobility in the environment. We have evaluated the sorption of Pu(IV)onto Hanford soil in the presence and in the absence of EDTA through laboratory-basedexperiments at ambient temperature and atmosphere. The sorption ratio (R%)was determined as a function of EDTA concentration and solid-liquid ratio.The sorption decreased significantly when EDTA concentration increased. Thediffusion of Pu(IV)–EDTA was relatively fast, with an effective diffusioncoefficient, D e = 3.54 . 10 –6 cm 2 /s at pH 5.25.
An On-Line Gamma Monitor profiles the concentration of uranium, plutonium, and americium in waste and product streams of the anion exchange process used to purify plutonium at Los Alamos. The Monitor employs passive gamma Spectrometry to measure the 59.5-KeV and 129-KeV gamma rays of241Am and239Pu, respectively. Because the uranium impurity in typical process streams has no gamma ray suitable for passive measurement, a novel radiotracer technique is used. Uranium-237, always present in plutonium processed at Los Alamos as a minor alpha-decay daughter of241Pu, has a 6.8-day half-life and 208-KeV gamma energy, which make it an ideal radiotracer for macro amounts of uranium in the process. The On-Line Gamma Monitor is used routinely to provide Los Alamos operators with continuous, real-time process control information.
Authors:K. Hirose, T. Miyao, M. Aoyama, and Y. Igarashisnm>
Plutonium isotopes in the Sea of Japan were determined to assess radioactive contamination. Concentrations of 239,240Pu in surface water of the Sea of Japan were maintained at a constant level over the past two decades in contrast to 137Cs. A median value of surface 239,240Pu in the Sea of Japan in this period was 5.6 mBq/m3 with the range between 2.1 and 14.0 mBq/m3, which is slightly higher than that in the western North Pacific. The vertical distribution of 239,240Pu showed a surface minimum, a subsurface maximum and gradual decrease with increasing depth. The 241Pu/239,240Pu activity ratios in water columns were almost constant except for surface water. In regard to 239,240Pu in surface water of the Sea of Japan, these findings suggest that rapid recycling of deeper plutonium occurs in the Sea of Japan due to deep convection in winter and biogeochemical processes such as particle scavenging and remineralization.
Authors:B. Araujo, H. Matsuda, E. Carvalho, and I. Araujo
A study of Pu recovery at trace level from U solutions by ion exchange technique is presented. Plutonium retention >99.5% onto strong anionic resin, AG-X8, from nitric acid solutions and a 92% recovery using 0.4M HNO3 at 60°C as eluent, were obtained. Uranium interference in Pu sorption from mixed U/Pu nitrate solutions with low U/Pu ratio (25) was not verified. However, for high U/Pu ratio solutions (10000), uranium interference in Pu retention on the resin, decreases to 59%. Selecting the loading conditions and using AG-X4 resin, 99% Pu retention was achieved. The Pu product is still contaminated with U and another purification cycle is recomended. A scheme for U/Pu first cycle separation is proposed.
The present plutonium levels in the Pacific Ocean are summarized. The 239,240Pu concentrations in surface seawaters in the early 2000s were in the range of 1.5 to 9.2 mBq·m−3 in the North Pacific and 0.8 to 4.1 mBq·m−3 in the South Pacific. There is no marked difference of surface 239,240Pu distributions between the North and South Pacific subtropical gyres. The vertical profile of 239,240Pu in the South Pacific was the similar pattern to that in the North Pacific, which is controlled by biogeochemical processes.
The 239,240Pu inventories (down to 2300 m) in the North Pacific are generally greater than that in the South Pacific, which reflects
the geographical distribution of global fallout and effect of close-in fallout in the Marshall Islands.
A new method of plutonium speciation in large volume of sea water was developed by using adsorption of Pu(IV)-Xylenol Orange chelate and Pu-Arsenazo chelate on XAD-2 resin, respectively. The tetravalent plutonium ion reacts selectively with Xylenol Orange in acid solution and that adsorbed on XAD-2 resin. Total plutonium can be collected onto the resin in the form of its Arsenazo-III complex. The determination of plutonium then was carried out by alpha-ray spectrometric method after decomposition of organic complexes and ion exchange separation. The present method is confirmed for convenient and rapid preconcentration procedure for plutonium shipboard chemistry.
Authors:K. Suresh Kumar, P. Magesvaran, D. Sreejeya, T. Kumar, B. Shreekumar, and P. Dey
During nuclear fuel reprocessing, monitoring of U and Pu concentration in every stage is very essential for process control
purpose. A simple and fast spectrophotometric method for a simultaneous estimation of U and Pu in Plutonium Uranium Recovery
by Extraction (PUREX) process’s tail end stream like Pu product where Pu concentration is much richer than that of U is described
here. The method involves reduction of the bulk amount of Pu to Pu(III) using ascorbic acid in 1 M HNO3. Visible absorption peaks were measured at 416 nm for U and at 600 nm for Pu using a fiber optic probe of path length 40 mm.
The methodology enables quantification of U and Pu concentration in the Pu product samples with a precision of 2.8 and 2.1%,
Studies on the individual potentiometric determination of uranium and plutonium in a single aliquot have been initiated recently
in our laboratory. It was required to adapt the reported procedures (for the precise determination of uranium and plutonium
individually when present together in a sample) at various stages to make them suitable for the successive application of
the procedures to the same aliquot. Two alternative schemes are proposed in the present work. In the first, plutonium is determined
by HClO4 oxidation followed by the determination of total uranium and plutonium by Zn(Hg) reduction. In the second, plutonium is determined
by AgO oxidation following the determination of total uranium and plutonium by Zn(Hg) reduction. Amount of uranium is computed
in both cases from the difference of two determinations. Precision for the assay of plutonium and uranium was found to be
±0.25% and ±0.35%, respectively, at milligram levels.
Authors:R. Jakopič, A. Verbruggen, R. Eykens, F. Kehoe, H. Kühn, Y. Kushigeta, U. Jacobsson, J. Bauwens, S. Richter, R. Wellum, and Y. Aregbe
In nuclear safeguards, precise and accurate isotopic analyses are needed for two major elements from the nuclear fuel cycle:
uranium and plutonium. This can be achieved by Isotope Dilution Mass Spectrometry (IDMS), which is one of the most reliable
analytical techniques for the determination of plutonium amount content to a high level of accuracy. In order to achieve reliable
isotope measurements isotopic reference materials with certified amount of plutonium and isotopic composition are required.
At the Institute for Reference Materials and Measurements (IRMM) various plutonium spike reference materials for isotopes
239Pu, 240Pu, 242Pu and 244Pu are available. This enabled the setup of an inter-calibration campaign inter-linking selected plutonium spikes on a metrological
basis applying state-of-the-art measurement procedures. The aim of this campaign is threefold: firstly to perform measurements
on selected plutonium spike isotopic reference materials for quality control purposes, secondly to verify the amount content
and the isotopic composition of the recently produced IRMM-1027m large sized dried (LSD) spikes and thirdly to demonstrate
IRMM’s measurement capabilities for plutonium analysis via external quality tools. The obtained results using various spike
isotopic reference materials will be presented and discussed in this paper. The measurement uncertainties of the IDMS results
were calculated according to the guide to the expression of uncertainty in measurement (GUM).
The extraction of plutonium(VI) and plutonium(III) from sulphuric acid by TOA in toluene has been studied as a function of
the acid and tri-octyl amine concentration. A comparison of the extraction properties of plutonium with those of uranium(VI)
and uranium(IV) has been made. It was found that the extraction properties of plutonium(VI) are very similar to those of uranium(VI)
and that TOA is a relatively poor extractant for plutonium(III). Uranium(IV) shows better extraction properties than plutonium(III).
The results obtained are considered in the light of the stabilities of the complexes formed by these elements in the organic
and aqueous phase. A method of separation of both elements by solvent extraction based on changing their oxidation states