Challenge to ultra-trace analytical techniques of nuclear materials in environmental samples for safeguards at JAERI: methodologies for physical and chemical form estimation

From a viewpoint of physical and chemical form estimation, ultra-trace analytical techniques of nuclear materials in environmental samples for safeguards have been investigated at Japan Atomic Energy Research Institute. This article deals with (1) an outline of the developed techniques for bulk and particle analyses of uranium and plutonium in the safeguards environmental samples; (2) current R&D on techniques relating to estimation of the physical and chemical form, such as SEM images and EDX spectra for fine particles of nuclear materials and fission track observation applicable to fissile materials; and (3) possible analytical methodologies, as future works, applicable to ultra-trace amounts of nuclear materials in environmental samples.     

Study on the etching conditions of polycarbonate detectors for particle analysis of safeguards environmental samples

The fission track technique was applied to the particle analysis for safeguards environmental samples to obtain information about the isotope ratio of nuclear materials in individual particles. To detect the particles containing nuclear material with high detection efficiency and less particle loss, the influence of uranium enrichments on etching conditions of a fission track detector made of polycarbonate was investigated. It was shown that the increase in uranium enrichment shortened the suitable etching time both for particle detection and for less particle loss. From the results obtained, it was suggested that the screening of the uranium particles according to the enrichment is possible by controlling the etching time of the detector.     

Accelerator mass spectrometry: ultra-sensitive analysis for global science

Accelerator mass spectrometry (AMS) is the analytical technique of choice for the detection of long-lived radionuclides that cannot be practically analysed with decay counting or conventional mass spectrometry. AMS has been used for the analysis of ¹⁴C, ¹⁰Be, ³⁶Cl and other cosmogenic radionuclides in archaeology, geology and environmental science. In addition, the ultrasensitivity of AMS is being applied in biomedicine to study the exposure of human tissues to chemicals and biomolecules at attomole levels. AMS is also being considered for the detection of anthropogenic radionuclides, such as ¹²⁹I and ²³⁶U, in environmental samples for the verification of the nuclear non-proliferation agreements. The state of the art of AMS is reviewed with examples from some recent applications.