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Plutonium, Neptunium and Uranium Trace Amounts

#3217


Valence States Determination of Plutonium, Neptunium and Uranium Trace Amounts in Environmental Samples by Chemiluminescence Laser Spectroscopy Methods

Tech Area / Field

  • ENV-MIN/Monitoring and Instrumentation/Environment

Status
3 Approved without Funding

Registration date
16.03.2005

Leading Institute
Khlopin Radium Institute, Russia, St Petersburg

Collaborators

  • Idaho National Engineering and Environmental Laboratory, USA, ID, Idaho Falls\nNagoya University / Graduate School of Engineering, Japan, Nagoya\nJapan Atomic Energy Agency, Japan, Ibaraki\nEuropean Commission / Joint Research Center / Institute for Transuranium Elements, Germany, Karlsruhe\nArgonne National Laboratory (ANL) / Chemistry Division, USA, IL, Argonne

Project summary

Laser spectroscopy gives the unique possibilities for detection of actinides in environmental samples. The combination of the high sensitivity and high selectivity with simultaneous determination of actinide valence state is an essential characteristic of laser spectroscopy, which is extremely important for application both in fundamental and applied fields. The most important subjects of detection are plutonium, neptunium, and uranium traces. The most sensitive laser spectroscopic methods involve detection of actinide luminescence in solutions (for example Time Resolved Laser Induced Fluorescence, TRLIF) with limit of detection (LOD) up to 10-12 M. Unfortunately, plutonium, neptunium, and some valence forms of uranium do not give direct photoluminescence in solutions and for their detection not most sensitive laser spectroscopy methods are used. Along with traditional absorption spectroscopy (LOD 10-5M), they are Laser Induced Photoacoustic Spectroscopy (LPAS) (LOD 10-7M) and laser spectroscopy with the use of the effect of thermal lens (TLS) (LOD = 10-6 M). However, despite low sensitivity, these methods allow obtaining information on actinide valence state in solutions and therefore they are widely used for these purposes.

In our experiments we first observed the chemiluminescence of actinide solutions caused by excitation of plutonium, neptunium and uranium with pulse laser radiation and studied the kinetics of this phenomenon. At present the chemiluminescence effects are widely used in biology and medicine for detection of trace amounts of various substances; in so doing the limit of detection reaches 10-11 M. In this case, it is possible to determine the element valence states and type of molecules. We have demonstrated for the first time the possibility of application of chemiluminescence methods to radiochemistry for detection of trace amounts of plutonium, neptunium, uranium and other actinides in solutions.

This project is devoted to optimization of procedure based on chemiluminescence effects for detection of trace amounts of plutonium, neptunium, and uranium in solutions with parallel estimation of valence states of actinides to be detected and also analysis of environmental samples. During the project execution the existing experimental installation will be modernized and the procedure of chemiluminescent analysis of trace amounts of actinides will be optimized. This optimization involves determination of the optimal parameters of laser radiation, the choice of the optimal scheme of actinide excitation, the optimal composition of the solutions, the optimal scheme of chemiluminescence registration, and the optimal parameters for registration of chemiluminescence using technique with time resolution. The experiments will be carried out both with model samples and with actual environmental samples. We are going to use our previous results and experience for optimization of the procedure and to reach the LOD up to 10-10 - 10-13M, i.e. improve the sensitivity of plutonium detection in solutions by 4–6 order of magnitude in comparison with the LIPAS and TLS methods; at the same time, the optimized procedure will allow obtaining the same information on actinide state as in the case of using the LIPAS and TLS methods.

The technology to be developed during the project execution will be applied for solution of two types of problems. The first problem involves analysis of trace amounts of plutonium, neptunium, and uranium in various samples. The second one, apparently most important, is determination of valence states of plutonium, neptunium, and uranium. At present, the other technologies have not such unique combination of high sensitivity and possibility of simultaneous determination of actinide characteristics in solutions. In optimisation of excitation process and registration of chemiluminescence induced by the laser-excited actinides in the solution, the technology to be developed in the Project will allow us to accelerate and simplify the analysis of trace amounts of plutonium, neptunium, uranium, and other actinides in various samples and reduce the price of this analysis.

The proposed technology will be used for detection of plutonium and neptunium in various environmental samples and study of actinide characteristics in these samples.


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