Search

Estimating the risks associated with radiation from long-lived fission products (LLFP) in radioactive waste is essential to ensure the long-term safety of potential disposal sites. In this study, the amount of 93Zr, a LLFP, was determined by ICP-MS after separating Zr from a spent nuclear fuel solution using a microvolume anion-exchange cartridge (TEDA cartridge). Zirconium in 9.4 M HCl was stably retained on the TEDA cartridge and readily eluted with 0.75 mL of a mixed solution of 9.4 M HCl and 0.01 M HF. The time taken to complete the Zr separation was 1.2 min. Almost all the other elements initially present in the spent nuclear fuel sample were removed, leading to accurate measurement of all six Zr isotopes (90Zr, 91Zr, 92Zr, 93Zr, 94Zr, and 96Zr). This demonstrated that the TEDA cartridge allowed highly selective separation of Zr regardless of its small bed volume of 0.08 cm3. The concentrations of these isotopes were determined by an isotope-dilution method using a natural Zr standard that has a different isotopic composition from that of the spent nuclear fuel sample. The amount of 93Zr in an initial spent nuclear fuel pellet was 1081 ± 79 ng per mg of 238U. The measured concentrations of all Zr isotopes, as well as the isotopic composition, were consistent with values predicted using a burnup calculation code.

The model dates of two enriched uranium materials were determined using a new method for nuclear forensics investigation. In this method, without spike addition, the 230Th/234U ratio was calculated from the measured ratios of 230Th/234Th and 234U/238U and from calculated 234Th/238U ratio in secular equilibrium. The model date obtained for the low-enriched uranium material was in agreement with the known production date. For the highly enriched uranium material, a more recent model date than the known production date was obtained. The 234U interference on 234Th counting in thermal ionization mass spectrometer measurement was suspected as a potential cause.

Isotope ratio analysis of individual uranium-plutonium (U-Pu) mixed oxide particles contained within environmental samples taken from nuclear facilities is proving to be increasingly important in the field of nuclear safeguards. However, isobaric interferences, such as 238U with 238Pu and 241Am with 241Pu, make it difficult to determine plutonium isotope ratios in mass spectrometric measurements. In the present study, the isotope ratios of 238Pu/239Pu, 240Pu/239Pu, 241Pu/239Pu, and 242Pu/239Pu were measured for individual Pu and U-Pu mixed oxide particles by a combination of alpha spectrometry and inductively coupled plasma mass spectrometry (ICP-MS). As a consequence, we were able to determine the 240Pu/239Pu, 241Pu/239Pu, and 242Pu/239Pu isotope ratios with ICP-MS after particle dissolution and chemical separation of plutonium with UTEVA resins. Furthermore, 238Pu/239Pu isotope ratios were able to be calculated by using both the 238Pu/(239Pu+240Pu) activity ratios that had been measured through alpha spectrometry and the 240Pu/239Pu isotope ratios determined through ICP-MS. Therefore, the combined use of alpha spectrometry and ICP-MS is useful in determining plutonium isotope ratios, including 238Pu/239Pu, in individual U-Pu mixed oxide particles.

An analytical procedure using micro-Raman spectroscopy (MRS) and secondary ion mass spectrometry (SIMS) was developed to elucidate both the chemical states and isotope ratios of individual micron-sized uranium particles. Each uranium particle was identified by scanning electron microscopy combined with energy dispersive X-ray detection and transferred onto each specific location on a substrate by micro-manipulation. After optimization of the analytical conditions, the chemical states of each uranium particle were determined with MRS non-destructively. The substrate containing each particle was then introduced into a SIMS instrument and uranium isotope ratios of each particle were determined. The developed method is expected to be used for clarifying the origin and history of each particle in environmental samples.

Sequential separation of 12 pg Pu and 50 ng of U, Pu, Th, Pb, and lanthanides in a calibration solution, with >93 % yield for the objective elements, was achieved within 6.3 h by an automatic system using a small anion-exchange column. The elements of interest in tree ring samples extracted from an 88-year-old pine tree were separated using this system, and 0.09 ng g−1 U was detected in the dry sample by inductively coupled plasma mass spectrometry. This separation technique is useful for ultra-trace quantitative and isotopic analyses of elements in small environmental samples.

The isotope ratio analysis of individual uranium particles in environmental samples taken at nuclear facilities is important to clarify their origins for nuclear safeguards. In the present study, automated particle screening was used to select uranium particles prior to precise isotope ratio analysis by thermal ionization mass spectrometry (TIMS). As a result, molecular ion interferences on the uranium mass region were able to be almost completely avoided in the analysis of real inspection samples using APM-TIMS. Therefore, the performance of APM-TIMS was sufficient for obtaining isotope ratio data of individual particles without molecular ion interferences., 原子力施設で採取された環境試料中の個々のウラン粒子の同位体比分析は、施設での未申告原子力活動を検知する上で重要である。本研究では、効率的な分析法の開発を目的として、自動粒子スクリーニングを利用して測定する粒子を選別し、表面電離質量分析法(TIMS)により同位体比分析を行う方法の開発を行った。本法により実際の査察試料を分析した結果、従来法に比べて分子イオンの影響を低減化して個々のウラン粒子の同位体比を決定することが可能なことが示され、本法の有効性が確かめられた。

Depth analysis of the surface oxide layer on a Mg2Si crystal was performed with X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS). In XPS, X-rays from synchrotron radiation with the energies between 2100 and 3300 eV were used as the excitation sources for depth analysis. The Si 1s and Mg 1s XPS spectra show the formation of a thinner SiO2-X layer at outermost surface and a thicker MgO layer at lower surface on the Mg2Si. In XAS, total electron yield and partial electron yield (PEY) acquisition modes were used for the measurement of Si K-edge. The PEY spectrum was obtained by detecting electrons with a fixed kinetic energy of 5, 10, 20, 30, 40, or 50 eV. Although the PEY spectrum with electrons of 5 eV shows similar features with the total electron yield spectrum, detection of electrons with 50 eV gives an increase in the ratio of a peak at 1843.7 eV to the peak assigned to Mg2Si. The peak at 1843.7 eV can be assigned to the formation of SiO2-X on the Mg2Si. From XPS and XAS results, it is indicated that a thinner SiO2-X layer at outermost surface and a thicker MgO layer at lower surface are formed at initial oxidation of the Mg2Si. Copyright © 2016 John Wiley & Sons, Ltd.

Estimating the risks associated with radiation from long-lived fission products (LLFP) in radioactive waste is essential to ensure the long-term safety of potential disposal sites. In this study, the amount of

In an inter-laboratory measurement comparison study, four laboratories determined 230Th–234U model ages of uranium certified reference material NBL U050 using isotope dilution mass spectrometry. The model dates determined by the participating laboratories range from 9 March 1956 to 19 October 1957, and are indistinguishable given the associated measurement uncertainties. These model ages are concordant with to slightly older than the known production age of NBL U050.

An analytical technique was developed by a combination of single particle dissolution, chemical separation of uranium, plutonium and americium with extraction chromatography using UTEVA resins and measurement with inductively coupled plasma mass spectrometry. This method was applied to plutonium isotope ratio analysis of individual U–Pu particles with U/Pu ratios ranging from 1 to 70. Consequently, 240Pu/239Pu, 241Pu/239Pu and 242Pu/239Pu isotope ratios were successfully determined, while it was impossible to determine 238Pu/239Pu ratios due to the high process blank values on m/z 238.

The analysis of isotope ratios in individual particles found in the environment is important to clarify the origins of the particles. In particular, the analysis of uranium particles in environmental samples from nuclear facilities is useful for detecting undeclared nuclear activities related to the production of nuclear weapons. Thermal ionization mass spectrometry (TIMS) combined with a fission track technique is an efficient method for determining the isotope ratios of individual uranium particles, but has a drawback called "particle-mixing". When some uranium particles are measured as a single particle and an average isotope ratio for the particles is obtained, it is called "particle mixing". This may lead to erroneous conclusions in terms of the particle sources that are identified. In the present study, microsampling using a scanning electron microscope was added to the fission track-TIMS procedure. The analysis of a mixture of SRM 950a and CRM U100 reference materials containing uranium particles indicated that particle mixing was almost completely avoided using the proposed technique. The performance of the proposed method was sufficient for obtaining reliable data for the sources of individual particles to be identified reliably.

The determination of the time (i.e., age) elapsed since the last purification of plutonium with chemical separation gives important information for monitoring nuclear activities related to reprocessing and nuclear weapon production. Although methods for the analysis of plutonium solutions have been extensively studied, few studies were conducted for the measurement of individual particles. In this work, a simple technique was developed for age determination of individual plutonium particles by a combination of single particle dissolution and measurement by inductively coupled plasma mass spectrometry (ICP-MS) without prior chemical separation. The analytical results of individual plutonium particles having an age of 5.98 y indicated that the use of 240 Pu/ 236 U ratios allowed for the determination of accurate ages, though that of 238 Pu/ 234 U and 239 Pu/ 235 U ratios was not suitable because of the contamination of natural uranium during the process of sample preparation. The developed technique is especially useful for the analysis of the samples containing a number of plutonium particles having different ages.

Isotope ratio analysis of individual uranium-plutonium (U-Pu) mixed oxide particles contained within environmental samples taken from nuclear facilities is proving to be increasingly important in the field of nuclear safeguards. However, isobaric interferences, such as

A fission track technique was used as a sample preparation method for subsequent isotope abundance ratio analysis of individual uranium containing particles with secondary ion mass spectrometry (SIMS) to measure the particles with higher enriched uranium efficiently. A polycarbonate film containing particles was irradiated with thermal neutrons and etched with 6 M NaOH solution. Each uranium containing particle was then identified by observing fission tracks created and a portion of the film having a uranium containing particle was cut out and put onto a glassy carbon planchet. The polycarbonate film, which gave the increases of background signals on the uranium mass region in SIMS analysis, was removed by plasma ashing with 200 W for 20 min. In the analysis of swipe samples having particles containing natural (NBL CRM 950a) or low enriched uranium (NBL CRM U100) with the fission track–SIMS method, uranium isotope abundance ratios were successfully determined. This method was then applied to the analysis of a real inspection swipe sample taken at a nuclear facility. As a consequence, the range of 235U/238U isotope abundance ratio between 0.0276 and 0.0438 was obtained, which was higher than that measured by SIMS without using a fission track technique (0.0225 and 0.0341). This indicates that the fission track–SIMS method is a powerful tool to identify the particle with higher enriched uranium in environmental samples efficiently.

Simultaneous determination of plutonium (Pu) and uranium (U) is preferred for analyzing the isotope ratio in Pu and U mixed samples such as the particles formed from MOX (mixed U–Pu oxide) fuels. In this study, we developed a method for the simultaneous measurement of all the plutonium and uranium isotopes without the need for chemical separation, using thermal ionization mass spectrometry (TIMS) with a continuous heating method. The MOX particles with sizes of 0.6–2.3 μm used in this study were made from a mixed solution of plutonium (SRM947) and uranium (U500, 50% 235U enriched). The isotope ratios of plutonium and uranium obtained for all the MOX particles, including the ones in the sub-micrometer size range, were in good agreement with the certified values within the range of error. In particular, the determination of the 238Pu/239Pu isotope ratio, which is difficult because of the isobaric interference of 238U, was performed accurately. The 238Pu/239Pu ratios were obtained by using a correction in which the background of 238U intensity at the 238Pu peak was estimated from the peak fitting of the 238U signal profile. In addition, the 241Pu/239Pu isotope ratio could be accurately measured without being influenced by the 241Am formed by the decay of 241Pu. For the MOX particles with diameters of 1.12 μm, the relative standard deviations (2RSDs) of the 238Pu/239Pu, 240Pu/239Pu, 241Pu/239Pu, and 242Pu/239Pu isotope ratios were 15.2%, 3.4%, 12.5%, and 5.1%, respectively. The relative standard deviations (2RSDs) of the 234U/238U, 235U/238U, and 236U/238U isotope ratios were 7.0%, 3.0%, and 41.2%, respectively. It is expected that the method developed in this study will become a powerful tool for the analysis of Pu and U mixed samples because of its ability to measure simultaneously even the minor isotopes of plutonium and uranium without any chemical separation.

A method for measuring isotope ratios of plutonium and uranium in plutonium or uranium–plutonium (Pu/U) mixture samples was developed by using a continuous heating method of thermal ionization mass spectrometry, which was previously shown to be effective in measuring isotope ratios of trace uranium. In this method, temperature of an evaporation filament is increased sequentially. This leads to measure the ratios of Pu and U at different temperatures in which each element is evaporated efficiently. Under optimal measurement conditions, the intensity of 239 Pu and the ratio of 240 Pu/ 239 Pu were measured down to sample amounts of 0.1 fg and 0.3 fg, respectively. In Pu/U mixture samples with pg-level masses and 0.01–10 Pu/U ratios, isotope ratios of 240 Pu/ 239 Pu and 235 U/ 238 U were measured simultaneously without chemical separation of samples. The relative standard deviation of the isotope ratios of 240 Pu/ 239 Pu and 235 U/ 238 U in the sample containing each 1 pg of plutonium and uranium were better than 2% and 4%, respectively. Moreover, 238 Pu/ 239 Pu ratios were obtained by using a correction in which the 238 U intensity was estimated from the 235 U intensity and the 235 U/ 238 U ratio. The results in this study suggest that the continuous heating method of thermal ionization mass spectrometry will be effective tool as a method for measuring isotope ratios in the Pu/U mixture samples.

Isotope ratio analysis of nuclear materials in individual particles is of great importance for nuclear safeguards. Although secondary ion mass spectrometry (SIMS) and thermal ionization mass spectrometry (TIMS) are utilized for the analysis of individual uranium particles, few studies were conducted for the analysis of individual uranium-plutonium mixed oxide particles. In this study, we applied SIMS and inductively coupled plasma mass spectrometry (ICP-MS) to the isotope ratio analysis of individual U-Pu mixed oxide particles. In the analysis of individual U-Pu particles prepared from mixed solution of uranium and plutonium standard reference materials, accurate 235 U/ 238 U, 240 Pu/ 239 Pu and 242 Pu/ 239 Pu isotope ratios were obtained with both methods. However, accurate analysis of 241 Pu/ 239 Pu isotope ratio was impossible, due to the interference of the 241 Am peak to the 241 Pu peak. In addition, it was indicated that the interference of the 238 UH peak to the 239 Pu peak has a possibility to prevent accurate analysis of plutonium isotope ratios. These problems would be avoided by a combination of ICP-MS and chemical separation of uranium, plutonium and americium in individual U-Pu particles.

The fission track technique is a sensitive detection method for particles which contain radio-nuclides like 235U or 239Pu. However, when the sample is a mixture of plutonium and uranium, discrimination between uranium particles and plutonium particles is difficult using this technique. In this study, we developed a method for detecting plutonium particles in a sample mixture of plutonium and uranium particles using alpha track and fission track techniques. The specific radioactivity (Bq/g) for alpha decay of plutonium is several orders of magnitude higher than that of uranium, indicating that the formation of the alpha track due to alpha decay of uranium can be disregarded under suitable conditions. While alpha tracks in addition to fission tracks were detected in a plutonium particle, only fission tracks were detected in a uranium particle, thereby making the alpha tracks an indicator for detecting particles containing plutonium. In addition, it was confirmed that there is a linear relationship between the numbers of alpha tracks produced by plutonium particles made of plutonium certified standard material and the ion intensities of the various plutonium isotopes measured by thermo-ionization mass spectrometry. Using this correlation, the accuracy in isotope ratios, signal intensity and measurement errors is presumable from the number of alpha tracks prior to the isotope ratio measurements by thermal ionization mass spectrometry. It is expected that this method will become an effective tool for plutonium particle analysis. The particles used in this study had sizes between 0.3 and 2.0 μm.

Surface characterization of a homoepitaxial β - FeSi 2 film grown on a β - FeSi 2 single crystal synthesized with a temperaturegradient solution method was performed by X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS). The annealing to remove native oxide layers on the crystal before homoepitaxial growth induced the formation of Fe-rich silicide in the surface. The XAS spectra confirm that the homoepitaxial β - FeSi 2 film can be grown on the crystal, while Fe-rich silicide is partially formed. The control of the surface chemical state is important to obtain homoepitaxial films with excellent quality.

Chemical state analysis by a combination of X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS) using synchrotron radiation is performed for β-FeSi 2 single crystals and homoepitaxial β-FeSi 2 films. The Si 2p XPS and Fe L-edge XAS spectra imply that the annealing at 1173 K to remove native oxide layers on the crystal induces the formation of FeSi in the surface. The formation of FeSi is also confirmed by Si K-edge XAS analysis. For the homoepitaxial β-FeSi 2 films grown on the crystals, the Si K-edge XAS spectra indicate that structurally homogeneous β-FeSi 2 films can be grown on the β-FeSi 2 single crystals when the substrate temperatures of 973 and 1073 K are applied for molecular beam epitaxy (MBE). Consequently, it is indicated that the combination of XPS and XAS using synchrotron radiation is a useful tool to clarify chemical states of β-FeSi 2 single crystals and homoepitaxial β-FeSi 2 films, which is important to reveal optimized growth conditions of homoepitaxial films.

A combination of X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS) using synchrotron radiation is applied to clarify surface chemical states of β-FeSi2 films fabricated by an ion-beam sputtering deposition method. The differences in the chemical states of the films fabricated at substrate temperatures of 873, 973 and 1173 K are investigated. For the film fabricated at 873 K, Si 2p XPS spectra indicate the formation of a relatively thicker SiO2 layer. In addition, Fe L-edge XAS spectra exhibit the formation of FeSi2−X by preferential oxidation of Si or the presence of unreacted Fe. The results for the film fabricated at 1173 K imply the existence of FeSi2 with α and ɛ phases. In contrast, the results for the film fabricated at 973 K indicate the formation of relatively homogeneous β-FeSi2. These imply that the relatively excellent crystal property of the film fabricated at 973 K is due to the formation of homogeneous β-FeSi2. As a conclusion, the combination of XPS and XAS using synchrotron radiation is a powerful tool to elucidate the surface chemical states of thin films.

A method to selectively detect uranium particles with high 235U enrichment has been developed; this method can contribute to improving particle analysis on nuclear safeguards environmental samples. The newly developed method involves three key components: (1) a two-step filtration system for particle recovery from swipe samples, (2) a system for controlling the etching time of fission track (FT) detector, and (3) a system for comparing the FT morphologies and particle sizes. The method to screen uranium particles according to their enrichment is focused on detecting highly enriched uranium particles preferentially in various particles recovered from swipe sample; this is one of the most important tasks involved in nuclear safeguards. In order to verify the effectiveness of the screening method developed, a mixture sample containing uranium particles with natural composition and those with 10% enrichment is used. It was shown that enrichment-based screening of uranium particles is possible by comparing the...

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 μm 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.

Anion-exchange porous sheets were prepared by radiation-induced graft polymerization and subsequent chemical modifications. A diethylamino (DEA) group as an anion-exchange group was introduced into the polymer chain grafted onto a porous sheet. The DEA group-introduced porous sheet was cut into disks 13 mm in diameter and 3 mm in thickness to fit an empty cylindrical cartridge (DEA cartridge). The DEA sheet had a DEA group of 3.4 mol/kg of the DEA-group-containing porous sheet and a linear velocity of 46 m/h at a permeation pressure of 0.1 MPa at 298 K. The adsorption capacity of the DEA cartridge for FeCl4− as a model ion in equilibrium with 1 g-Fe(III)/L in 10 M HCl was 0.17 mmol-Fe(III)/DEA cartridge. No Pu leakage during the permeation of 5 mL of 10 M HCl–0.1 M HNO3 containing Pu ionic species through the DEA cartridge was observed irrespective of the permeation rate ranging from 0.3 to 80 mL/min. A solution containing known amounts of 233U, 240Pu, and 241Am in 10 M HCl–0.1 M HNO3 was loaded onto the DEA cartridge. U and Pu were retained on the DEA cartridge, while Am was allowed to pass through the DEA cartridge. Subsequently, 7 M HNO3 and 1 M HCl as eluents were permeated to elute U and Pu from the DEA cartridge, respectively. The decontamination factor of U in a Pu fraction, defined by dividing the activity of U in the feed solution by that of U in the Pu fraction, was 2.7 × 105, which is desirable for the highly accurate ICP-MS determination of Pu for samples containing both U and Pu. The method using the DEA cartridge was validated by measuring isotopic compositions and quantities of U and Pu in a spent nuclear fuel sample by double-focusing magnetic sector ICP-MS.

The dependence of the precision of uranium isotope ratio on particle diameter in secondary ion mass spectrometry (SIMS) was investigated. Each uranium particle in certified reference materials with different isotopic composition (235U/238U = 0.01–1.00) was observed with a scanning electron microscope (SEM) and transferred by a manipulator on a glassy-carbon planchet for subsequent isotope ratio analysis with SIMS. The relative standard deviation (RSD) of uranium isotope ratios varied with particle diameter, the amount of less abundant uranium isotope and the number of measurement cycles. For the particle with the diameter less than 1.0 μm, the RSD significantly increased with increasing the number of measurement cycles, which is due to the difficulty of obtaining constant signals for a long duration. In contrast, no significant increase in the RSD was observed in the analysis of the particle with the diameter larger than 2.0 μm. As the results, it is estimated that the 235U amount of 4.5 fg is sufficient to obtain the 235U/238U ratio with the RSD within 5.0%. For the analysis of minor isotopes, the 234U amount of 0.42 fg and the 236U amount of 1.1 fg are sufficient to obtain the 234U/238U and 236U/238U ratios with the RSD within 20%, respectively.

The isotopic composition of single uranium and plutonium particles was measured with an inductively coupled plasma mass spectrometer (ICP-MS) and a thermal ionization mass spectrometer (TIMS). Particles deposited on a carbon planchet were first analyzed with an energy dispersive X-ray spectrometer (EDX) attached to a scanning electron microscope (SEM) and then transferred on to a silicon wafer using a manipulator. The particle on the silicon wafer was dissolved with nitric acid and the isotopic ratios of U and Pu were measured with ICP-MS and TIMS. The results obtained by both methods for particles of certified reference materials showed good agreement with the certified values within the expected uncertainty. The measurement uncertainties obtained in this study were similar for both mass spectrometric methods. This study was performed to establish the method of particle analysis with SEM, EDX, the particle manipulation and chemical preparation technique, and the measurement of isotopic ratios of U and Pu in a single particle by mass spectrometry.

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.

The capability of inductively coupled plasma mass spectrometry (ICP-MS) for the determination of uranium isotope ratios in individual particles was determined. For this purpose, we developed an experimental procedure including single particle transfer with a manipulator, chemical dissolution and isotope ratio analysis, and applied to the analysis of individual uranium particles in certified reference materials (NBL CRM U050 and U350). As the result, the 235 U/ 238 U isotope ratio for the particle with the diameter between 0.5 and 3.9 μm was successfully determined with the deviation from the certified ratio within 1.8%. The relative standard deviation (R.S.D.) of the 235 U/ 238 U isotope ratio was within 4.2%. Although the analysis of 234 U/ 238 U and 236 U/ 238 U isotope ratios gave the results with inferior precision, the R.S.D. within 20% was possible for the measurement of the particle with the diameter more than 2.1 μm. The developed procedure was successfully applied to the analysis of a simulated environmental sample prepared from a mixture of indoor dust (NIST SRM 2583) and uranium particles (NBL CRM U050, U350 and U950a). From the results, the proposed procedure was found to be an alternative analytical tool for nuclear safeguards.

In order to know the distribution of plutonium derived from the Nagasaki atomic bomb, soil samples were measured to determine the 240Pu/239Pu isotope ratio of and concentrations of 239+240Pu and 137Cs. The 239+240Pu concentrations in soils, except for Nishiyama area, were close to the average concentration of soil collected in Japan. In soils collected at the Nishiyama area and at the eastern area of Nagasaki Prefecture and at part of northern area in Kumamoto Prefecture, the 240Pu/239Pu ratios were lower than the global fallout values. This suggests that plutonium from the atomic bomb was deposited in the eastern area from the hypocenter reaching up to 100 km eastwards.

A diethylamino (DEA) group as an anion exchanger was introduced into a polymer chain grafted onto the pore surface of a porous sheet. The resultant porous sheet was cut into disks to fit a cylindrical cartridge (DEA cartridge) and the adsorption-elution behaviors for actinides were investigated. U and Pu in 10 M HCl-0.1 M HNO3 were adsorbed on the DEA cartridge, and quantitative recoveries were achieved with 7 M HNO3 and 1 M HCl, respectively. The elution curves of Pu with 10 M HCl-0.1 M HNO3 and 1 M HCl overlapped irrespective of its flow rate. The flow rates of the loading and stripping solutions permeating through the pores of the DEA disk were 6-10 times higher than those through the interstices of an anion-exchange-resin-bead-packed column. The decontamination factors evaluated from a mutual separation of Am, U, and Pu were higher than 104 for both U and Pu fractions. The time required for the mutual separation was approximately 1 h.

In order to assess the extent of the elimination of humidity and the presence of pine trees on the elemental composition of airborne dust, the concentration of 21 elements were measured in airborne dust collected with a high-volume sampler at JAERI by instrumental neutron activation analysis (INAA). It was found that the concentration of soil-origin elements, such as Al, Sc and Th, decreased as the humidity increased, and the Cl/Na ratio of sea salt constituent in the dust samples increased with the decrease of humidity after the felling of the trees.

Uranium, thorium, lead, and the lanthanides were automatically and sequentially separated with a single anion-exchange column. This separation was achieved using eluents consisting of a simple and highly pure acid mixture of HCl, HNO3, acetic acid, and HF. The elements of interest were separated from the major constituents, which included alkaline metal elements, alkaline earth metal elements, and iron. This simple and automatic system is driven with pressurized nitrogen gas and controlled using a computer program. An optimized separation was accomplished under the following conditions: a 50 mm long and 2 mm diameter column, 11 μm diameter anion-exchange resin, and a 35 μL min−1 flow rate. Using this system, 50 ng of varied elements in a 100 μL feed solution were perfectly separated within 5 h with >400 decontamination factors and >95% yield. In order to evaluate the performance of this system, a reference powdered rock sample was separated using this system. Abundances of objective elements, including 0.23 ng of lutetium, were accurately determined without corrections of chemical recovery yield or subtraction of the process blank. This separation technique saves time and effort for chemical processing, and is useful for ultra-trace quantitative and isotopic analyses of elements in small environmental samples.

Age of individual uranium-plutonium (U/Pu) mixed particles with various U/Pu atomic ratios (1-70) were determined by inductively coupled plasma mass spectrometry. Micron-sized particles were prepared from U and Pu certified reference materials. The Pu reference was stored for 4-6 years since the last purification (July 14, 2008). The Pu purification age was obtained from the (241)Am/(241)Pu ratio which was calculated from the product of three measured ratios of Pu and Am isotopes in the eluted fractions. These ratios were measured by a high-resolution inductively coupled plasma mass spectrometer equipped with a desolvation system. Femto-gram to pico-gram quantities of Am, U, and Pu in a sample solution were sequentially separated on a small anion-exchange column. The (241)Am/(241)Pu ratio was accurately determined by spiking pure (243)Am into the sample solution. The average determined age for the particles for the five independent U/Pu ratios was in good agreement with the expected age with high accuracy (difference age 0.27 years) and high precision (standard deviation 0.44 years). The described analytical technique can serve as an effective tool for nuclear safeguards and environmental radiochemistry. Figure Young (4-6 y) Pu purification age of individual U/Pu mixed micron-sized reference particles for the five independent U/Pu ratios (1-70) were determined with 0.27±0.44 y difference from the expected age. Sub pico-gram quantities of Am, U and Pu were sequentially separated a small column, and their isotope ratios were accurately measured using an ICP-MS by applying the (243)Am spiking technique to the analysis and correcting the impurity and the contaminations.

Thermal ionization mass spectrometry (TIMS) with a continuous heating technique is known as an effective method for measuring the isotope ratio in trace amounts of uranium. In this study, the analytical performance of thermal ionization mass spectrometry with a continuous heating technique was investigated using a standard plutonium solution (SRM 947). The influence of the heating rate of the evaporation filament on the precision and accuracy of the isotope ratios was examined using a plutonium solution sample at the fg level. Changing the heating rate of the evaporation filament on samples ranging from 0.1fg to 1000fg revealed that the influence of the heating rate on the precision and accuracy of the isotope ratios was slight around the heating rate range of 100-250mA/min. All of the isotope ratios of plutonium (SRM 947), (238)Pu/(239)Pu, (240)Pu/(239)Pu, (241)Pu/(239)Pu and (242)Pu/(239)Pu, were measured down to sample amounts of 70fg. The ratio of (240)Pu/(239)Pu was measured down to a sample amount of 0.1fg, which corresponds to a PuO2 particle with a diameter of 0.2μm. Moreover, the signals of (239)Pu could be detected with a sample amount of 0.03fg, which corresponds to the detection limit of (239)Pu of 0.006fg as estimated by the 3-sigma criterion. (238)Pu and (238)U were clearly distinguished owing to the difference in the evaporation temperature between (238)Pu and (238)U. In addition, (241)Pu and (241)Am formed by the decay of (241)Pu can be discriminated owing to the difference in the evaporation temperature. As a result, the ratios of (238)Pu/(239)Pu and (241)Pu/(239)Pu as well as (240)Pu/(239)Pu and (242)Pu/(239)Pu in plutonium samples could be measured by TIMS with a continuous heating technique and without any chemical separation processes.

The technique of single particle transfer was applied to quantitative analysis with total-reflection X-ray fluorescence (TXRF) spectrometry. The technique was evaluated by performing quantitative analysis of individual Cu particles with diameters between 3.9 and 13.2 μm. The direct quantitative analysis of the Cu particle transferred onto a Si carrier gave a discrepancy between measured and calculated Cu amounts due to the absorption effects of incident and fluorescent X-rays within the particle. By the correction for the absorption effects, the Cu amounts in individual particles could be determined with the deviation within 10.5%. When the Cu particles were dissolved with HNO 3 solution prior to the TXRF analysis, the deviation was improved to be within 3.8%. In this case, no correction for the absorption effects was needed for quantification.

Uranium and plutonium isotope ratios in individual uranium-plutonium (U-Pu) mixed particles with various U/Pu atomic ratios were analyzed without prior chemical separation by thermal ionization mass spectrometry (TIMS). Prior to measurement, micron-sized particles with U/Pu ratios of 1, 5, 10, 18, and 70 were produced from uranium and plutonium certified reference materials. In the TIMS analysis, the peaks of americium, plutonium, and uranium ion signals were successfully separated by continuously increasing the evaporation filament current. Consequently, the uranium and plutonium isotope ratios, except the (238)Pu/(239)Pu ratio, were successfully determined for the particles at all U/Pu ratios. This indicates that TIMS direct analysis allows for the measurement of individual U-Pu mixed particles without prior chemical separation.

A screening method for uranium particles according to their enrichment has been developed by using the characteristics of fission tracks, which depend on the enrichment of the uranium particles. A two-step filtration system that can collect particles with desired diameters was used for the collection of uranium particles from a swipe sample in order to avoid the influence of the differences in the diameter on the etching behavior of fission tracks. It was shown that the enrichment-based screening of the uranium particles is possible by controlling the etching time to detect fission tracks and by comparing fission track morphologies.

We have developed an effective method for fission track (FT) sample preparation to perform particle analysis of the safeguards environmental samples by the FT-thermal ionization mass spectrometry (TIMS) method. In this method, a FT detector and the layer containing particles are separated. The main feature of the developed FT sample is that the detection of a particle from the corresponding FT can be performed correctly and in a simple manner by fixing each one end of the detector and the particle layer and by using an etching tool. It is expected that this method will enhance the effectiveness of particle analysis.

Secondary ion mass spectrometry (SIMS) was used in combination with alpha track detection for the efficient analysis of uranium-bearing particles with higher 235U abundances in environmental samples. A polycarbonate film containing particles was prepared and placed in contact with a CR-39 plastic detector. After exposure for 28 days, the detector was etched in a NaOH solution and each uranium-bearing particle was identified through observation of the alpha tracks recorded in the detector. A portion of the film containing each uranium-bearing particle was cut out and put onto a glassy carbon planchet. The films on the planchet were decomposed through plasma ashing for subsequent uranium abundance ratio analysis with SIMS. The alpha track-SIMS analysis of 10 uranium-bearing particles in a sample taken from a nuclear facility enabled n(235U)/n(238U) abundance ratios in the range 0.0072–0.25 to be detected, which were significantly higher than those obtained by SIMS without alpha track detection. The duration of the whole analytical process for analysis of 10 particles was about 32 days. The detection efficiency was calculated to be 27.1±6.5%, based on the analysis of the particles in uranium reference materials. The detection limits, defined as the diameter of the particle which produces alpha tracks more than one for a 28-days exposure, were estimated to be 0.8, 0.9, 1.1, 2.1 and 3.0 μm for the particles having the same uranium abundance ratios with NBL CRM U850, U500, U350, U050 and U010 reference materials, respectively. The use of alpha track detection for subsequent SIMS analysis is an inexpensive and an efficient way to measure uranium-bearing particles with higher 235U abundances.

Airborne radioactive particles released by the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident in 2011 were collected with a cascade low-pressure impactor at the Japan Atomic Energy Agency (JAEA) in Tokai, Japan, 114 km south of the FDNPP. Size-fractionated samples were collected twice, in the periods of March 17-April 1, 2011, and May 9-13, 2011. These size-fractionated samplings were carried out in the earliest days at a short distance from the FDNPP. Radioactivity of short-lived nuclides (several ten days of half-life) was determined as well as (134)Cs and (137)Cs. The elemental composition of size-fractionated samples was also measured. In the first collection, the activity median aerodynamic diameter (AMAD) of (129m)Te, (140)Ba, (134)Cs, (136)Cs and (137)Cs was 1.5-1.6 μm, while the diameter of (131)I was 0.45 μm. The diameters of (134)Cs and (137)Cs in the second collection were expressed as three peaks at0.5 μm, 0.94 μm, and 7.8 μm. The (134)Cs/(137)Cs ratio of the first collection was 1.02 in total, but the ratio in the fine fractions was 0.91. A distribution map of (134)Cs/(137)Cs - (136)Cs/(137)Cs ratios was helpful in understanding the change of radioactive Cs composition. The Cs composition of size fractions0.43 μm and the composition in the 1.1-2.1 μm range (including the AMAD of 1.5-1.6 μm) were similar to the calculated compositions of fuels in the reactors No. 1 and No. 3 at the FDNPP using the ORIGEN-II code. The Cs composition collected in May, 2011 was similar to the calculation results of reactor No. 2 fuel composition. The change of Cs composition implies that the radioactive Cs was released from the three reactors at the FDNPP via different processes.

This work introduces a novel method of recovery of iron hydroxide using a DIAION CR-20 chelating resin column to determine Th isotopes in seawater with a sector field (SF) inductively coupled plasma mass spectrometer (ICP-MS). Thorium isotopes in seawater were co-precipitated with iron hydroxide, and this precipitate was sent to chelating resin column. Ferric ions in the iron hydroxide were bonded to functional groups of the chelating resin directly, resulting in a pH increase of the effluent by release of hydroxide ion from the iron hydroxide. The co-precipitated thorium isotopes were quantitatively collected within the column, which indicated that thorium was retained on the iron hydroxide remaining on the chelating column. The chelating column quantitatively collected 232 Th with iron hydroxide in seawater at flow rates of 20–25 mL min −1 . Based on this flow rate, a 5 L sample was processed within 3–4 h. The >20 h aging of iron hydroxide tends to reduce the recovery of 232 Th. The rapid collection method was successfully applied to the determination of 230 Th and 232 Th in open-ocean seawater samples.

Mossbauer spectroscopy was used to study iron in the β-, δ-, δ′- and e-iron tellurides in the temperature range from 300 to 1000 K. Mossbauer diffusional line broadening was observed in all phases except the e-phase. The activation energies for iron diffusional jump frequencies in the β-, δ- and δ′-phases increased in this order with increasing tellurium concentrations. This fact may be explained in terms of the nearest jump distance between the iron atom and the neighboring iron sites.

The diffusional line broadening of iron in δ-iron telluride (Fe 0.743 Te) polycrystal was measured by means of Mossbauer spectroscopy in the temperature range from 851 to 1000 K. The diffusional jump frequency and the activation energy for the diffusion of iron in δ-iron telluride obtained in this study are compared with those in β-, δ'-and ϵ-iron tellurides reported by the present authors previously. By assuming random walk, the diffusion coefficients of iron in δ-iron telluride are estimated from the diffusional jump frequencies for three different cases, and their results ar compared with eath other.

Information on plutonium isotope ratios in individual particles is of great importance for nuclear safeguards, nuclear forensics and so on. Although secondary ion mass spectrometry (SIMS) is successfully utilized for the analysis of individual uranium particles, the isobaric interference of americium-241 to plutonium-241 makes difficult to obtain accurate isotope ratios in individual plutonium particles. In the present work, an analytical technique by a combination of chemical separation and inductively coupled plasma mass spectrometry (ICP-MS) is developed and applied to isotope ratio analysis of individual sub-micrometer plutonium particles. The ICP-MS results for individual plutonium particles prepared from a standard reference material (NBL SRM-947) indicate that the use of a desolvation system for sample introduction improves the precision of isotope ratios. In addition, the accuracy of the 241 Pu/ 239 Pu isotope ratio is much improved, owing to the chemical separation of plutonium and americium. In conclusion, the performance of the proposed ICP-MS technique is sufficient for the analysis of individual plutonium particles.

57Fe Mossbauer spectroscopic studies on the β-Fe1.12Te, δ′-Fe1.33Te2 and e-FeTe2.11 samples have been performed in the temperature range from room temperature to 1000K. The isomer shifts of β-Fe1.12Te, δ′-Fe1.33Te2 and e-FeTe2.11 samples at 823K are 0.09, 0.18 and 0.17 mm/s, respectively. The smaller isomer shift of β-phase with iron in tetrahedral sites than those of δ′- and e-phases with iron in octahedral sites may be explained probably due to small shielding by d-electrons. The effects of temperature and composition on the isomer shift and quadrupole splitting are discussed.