Comparison of ICP-MS and SIMS techniques for determining uranium isotope ratios in individual particles.

The determination of uranium isotope ratios in individual particles is of great importance for nuclear safeguards. In the present study, an analytical technique by inductively coupled plasma mass spectrometry (ICP-MS) with a desolvation sample introduction system was applied to isotope ratio analysis of individual uranium particles. In ICP-MS analysis of individual uranium particles with diameters ranging from 0.6 to 4.2 microm in a standard reference material (NBL CRM U050), the use of the desolvation system for sample introduction improved the precision of (234)U/(238)U and (236)U/(238)U isotope ratios. The performance of ICP-MS with desolvation was compared with that of a conventionally used method, i.e., secondary ion mass spectrometry (SIMS). The analysis of test swipe samples taken at nuclear facilities implied that the performance of ICP-MS with desolvation was superior to that of SIMS in a viewpoint of accuracy, because the problems of agglomeration of uranium particles and molecular ion interferences by other elements could be avoided. These results indicated that ICP-MS with desolvation has an enough ability to become an effective tool for nuclear safeguards.

Depositional records of plutonium and (137)Cs released from Nagasaki atomic bomb in sediment of Nishiyama reservoir at Nagasaki.

In a sediment core of Nishiyama reservoir at Nagasaki city, depth profiles of (240)Pu/(239)Pu isotopic ratio, (239+240)Pu and (137)Cs activities were determined. Sediments containing plutonium and (137)Cs, which were deposited immediately after a detonation of Nagasaki atomic bomb, were identified in the core. Observed below the sediments were macroscopic charcoals, providing evidence for initial deposit of the fallout of the Nagasaki atomic bomb. This is the first entire depositional records of plutonium and (137)Cs released from the Nagasaki atomic bomb together with those from atmospheric nuclear tests.

Plutonium isotopes derived from Nagasaki atomic bomb in the sediment of Nishiyama reservoir at Nagasaki, Japan.

The source of plutonium in sediments deposited at Nishiyama reservoir at Nagasaki was characterized by their (240)Pu/(239)Pu atom ratio. The average ratio was approximately 0.03, except in two layers. The main source of the plutonium was the Nagasaki atomic bomb. The plutonium continues to flow into the reservoir even now. The (240)Pu/(239)Pu atom ratios in two layers were higher than the average, which showed that plutonium in these layers were made of those of nuclear tests added to those of the atomic bomb.

Particle isolation for analysis of uranium minor isotopes in individual particles by secondary ion mass spectrometry.

A new technique to measure (234)U/(238)U and (236)U/(238)U isotope ratios for individual particles in environmental samples was developed, which was a combination of particle isolation under scanning electron microscope (SEM) and secondary ion mass spectrometry (SIMS). The technique was verified by measuring (234)U/(238)U and (236)U/(238)U isotope ratios in individual particles in a simulated environmental sample containing uranium standard (NBL CRM U010) and Pb metal particles. When the uranium particles were not isolated, the relative deviations of the measured isotope ratios from the reference values increased with increasing the signal intensity ratio of (208)Pb to (238)U, which was due to the molecular ion interferences by the Pb particles co-existing in the sputtered area. By the isolation of individual uranium particles, the interferences were eliminated and the measured isotope ratios were in good agreement with the reference values. The maximum relative deviations among 20 particles were 8.9% for (234)U/(238)U and 13.1% for (236)U/(238)U isotope ratios, respectively. The technique was also successfully applied to the analysis of a real swipe sample containing various kinds of elements.

Development of analytical techniques for ultra trace amounts of nuclear materials in environmental samples using ICP-MS for safeguards

The authors have begun to develop analytical techniques for ultra trace amounts of nuclear materials and to prepare a clean chemistry laboratory for environmental sample analyses. The analytical techniques include bulk and particle analyses. For the bulk analysis, concentrations and isotopic ratios of U and/or Pu are determined by inductively-coupled plasma mass spectrometry (ICP-MS) and thermal ionization mass spectrometry (TIMS). In the particle analysis, isotopic ratios of U and/or Pu in each particle will be measured by secondary ion mass spectrometry (SIMS). This paper reports on the outline for the development of analytical techniques and the current situation of the development of the bulk analysis using ICP-MS is described.

[Development of passive telemetry system for intracranial pressure measurement with corrector of errors caused by temperature variation].

A new passive telemeter for the intracranial pressure monitoring have been developed. The completely implantable pressure sensor used in this system consists of a crystal, a coil and a ferrite rod attached on a diaphragm. The pressure on the diaphragm alters the volume of air in the receptacle and then the ferrite rod moves in and out of the coil and alters the resonance frequency of the sensor. Although the sensor doesn't have a battery or other energy storer, for example, a capacitor, the resonance frequency can be measured without contact. Therefore, at any time, we can measure the intracranial pressure with this sensor implanted under the scalp beforehand. However, not only pressure but also temperature alters the resonance frequency of the sensor, because the volume of air alters in proportion to temperature. Hence, we have developed a new passive telemetry pressure sensor which contains a passive telemetry temperature sensor. The temperature sensor consists of a coil and a special crystal whose resonance frequency varies with ambient temperature and its resonance frequency can be measured in the same way that we measure the resonance frequency of pressure sensor from outside of the body. With this system, we can measure the intracranial pressure about 60 times per second and the intracranial temperature every 8 seconds. The measured value of the pressure was automatically corrected by analog temperature correcting electric circuits. In animal experiment, the output of this system was similar to one of the catheter-tip type pressure transducer and we could observe the intracranial pressure altered synchronizing with respiration and with heart beat.