Hideaki Matsue

Accurate and efficient determination of boron content in volcanic rocks by neutron induced prompt gamma-ray analysis

An accurate and efficient analytical method using neutron-induced prompt γ-ray was developed for the determination of boron contents in volcanic rocks. We corrected the effect of sample geometry and flux fluctuation by using silicon as an internal standard. However, we found that the slopes of the calibration line vary among volcanic samples with different matrix. Because the increase of boron activity correlates positively with γ-ray count rate of hydrogen (water), we call this as the hydrogen effect. The hydrogen effect was confirmed by our experiment in which the boron activities showed systematic increase with the amount of added hydrogen (water). Most volcanic rocks, however, contain little water (<2 wt.%) to show this effect. We determined boron contents in various volcanic rocks in order to confirm the validity of the procedure that we established. The analyzed boron contents agreed well with the previous reported values. For efficient PGA of boron in volcanic rocks, we recommend JB-2 (GSJ standard rock) as a single geochemical standard, because of its high boron content (31.2 ppm).

Accurate determination of arsenic in arsenobetaine standard solutions of BCR-626 and NMIJ CRM 7901-a by neutron activation analysis coupled with internal standard method.

Neutron activation analysis (NAA) coupled with an internal standard method was applied for the determination of As in the certified reference material (CRM) of arsenobetaine (AB) standard solutions to verify their certified values. Gold was used as an internal standard to compensate for the difference of the neutron exposure in an irradiation capsule and to improve the sample-to-sample repeatability. Application of the internal standard method significantly improved linearity of the calibration curve up to 1 microg of As, too. The analytical reliability of the proposed method was evaluated by k(0)-standardization NAA. The analytical results of As in AB standard solutions of BCR-626 and NMIJ CRM 7901-a were (499+/-55)mgkg(-1) (k=2) and (10.16+/-0.15)mgkg(-1) (k=2), respectively. These values were found to be 15-20% higher than the certified values. The between-bottle variation of BCR-626 was much larger than the expanded uncertainty of the certified value, although that of NMIJ CRM 7901-a was almost negligible.

Carbon-14 analysis in solidified product of non-metallic solid waste by a combination of alkaline fusion and gaseous CO2 trapping

In order to establish a simple and rapid analytical method for (14)C in solidified products made from non-metallic low-level radioactive solid wastes such as concrete, mortar and glass by melting treatment, a radiochemical analysis in combination with alkaline fusion as a sample decomposition method was examined. A simulated solidified product containing (14)C, which was prepared by using nuclear reaction (14)N(n, p)(14)C with thermal neutron irradiation, was analyzed by the present method to compare with a conventional radiochemical analysis using oxidizing combustion. The reproducible and quantitative recovery of (14)C from the simulated solidified product indicates that the present method is more efficient for (14)C analysis in solidified products than the conventional method using oxidizing combustion.

Distribution of boron in wood treated with aqueous and methanolic boric acid solutions

The distributions of boron in Japanese cedar (Cryptomeria japonica D. Don) sapwood blocks treated with aqueous or methanolic boric acid [B(OH)3] solutions were explored through Raman spectroscopy and prompt gamma-ray analysis (PGA). B(OH)3 was the sole boron species observed in Raman spectra of the wood blocks treated with either solution. Plots of weight gain of the treated wood blocks versus boron concentration in treatment solutions were found to be linear. The results indicated that the methanolic solution makes it possible to impregnate wood with much larger amounts of boron than the aqueous solution. PGA confirmed that B(OH)3 was highly enriched near the end grains of the treated wood blocks. Raman measurements suggested that boron content in the bulk of the wood block is not as large as expected from the weight gain of the treated wood blocks when an ordinary air-drying method is used. It was concluded that the aqueous solution impregnates the cell walls of wood with boron more easily than the methanolic solution.

Two-dimensional differential calibration method for a neutron dosemeter using a thermal neutron beam

A new thermal neutron calibration method to experimentally determine the energy response function of a neutron detector using a pulse parallel beam and the time-of-flight (TOF) technique is developed. The calibration method was experimentally demonstrated for a (3)He proportional counter and an electric personal dosemeter using a pulsed thermal neutron beam from the research reactor JRR-3M. The responses of the detectors were successfully obtained as a function of neutron energy. However, detailed information on the detector structure is required to obtain the spatial response distribution for the detector. The authors further propose an improved calibration method obtaining the spatial response distribution using a pulsed narrow beam, the TOF technique and a beam scanning technique.

Analysis of boron in wood treated with boric acid solutions using Doppler broadening method of prompt gamma-rays

Wood preservatives such as boric acid and/or borate have been expected to emerge as effective substitutes for chromated copper arsenate (CCA) because of their lower toxicity. However, such preservatives have not been commercially available in Japan because these boron compounds are easily eluted from wood by rainwater. We have applied a multipronged approach to the problem of preventing the easy elution of boron. To obtain knowledge of the chemical species and distribution of boron in wood, we have explored wood treated with aqueous and methanolic boric acid solutions by using Raman spectroscopy. The methods of analyzing boron in the solid state are restricted to Raman spectroscopy and only a few other techniques. Regarding the analysis of boron contained in wood, there has so far been only an electron probe microanalysis (EPMA) study of boron distribution other than our Raman studies. The Raman technique enables us to identify boron species in wood, because boric acid and most borates show several characteristic Raman bands. However, Raman spectroscopy is not sensitive enough to detect low concentrations of boron species in wood and is not suitable for quantitative analysis of solid samples. In general, there are few analytical techniques that can determine the boron content in solids. However, the recent development of neutron-induced prompt gamma-ray analysis (PGA) has allowed us to obtain a powerful tool for the detection of trace amounts of boron in various samples, which is basically in a category of neutron-activation analysis although on-line measurement is absolutely necessary. Boron is one of the elements for which PGA has an ultimate sensitivity by using 478-keV prompt gamma-rays emitted from Li produced in the B (n, a) Li reaction. Li represents the Li atomic nucleus in an excited state. The cross section of the nuclear reaction is 3838 barn for the thermalneutron capture. Such a large cross section should lead to high analytical sensitivity. The PGA analysis of boron provides us not only the information on boron contents but also on boron states by probing the Doppler broadened line shape of 478-keV gamma-ray. The initial recoil energy imparted to a Li ion by the nuclear reaction is 840keV, corresponding to an initial velocity (4.8 × 10 ms) of a Li nucleus. A Li nucleus with a lifetime of 1.05 × 10 s emits a 478-keV gamma-ray in flight, which leads to Doppler energy shift. Because the direction of the Li recoil is isotropic, the spectral line shape is observed with Doppler broadening. An energetic Li ion loses kinetic energy through interaction with atoms that the moving ion encounters in medium. It was proved experimentally and theoretically that the velocity v(t) decreases with time t as follows:

Neutron Activation Property of Colemanite-Peridotite Concrete

Abstract Trace element analysis using instrumental neutron activation analysis for neutron shield concrete made from colemanite and peridotite rocks is carried out. Also, an activation estimation for the concrete wall in the accelerator neutron source facility is calculated using the obtained element data. The results show that the amount of short-half-life nuclide production in the neutron shield concrete is ˜1/100 that of limestone concrete and also that the amount of 60Co production is 1/5 to 1/8 that of limestone concrete. From these results, the activation property of the neutron shield concrete was found to be much less than that of the limestone concrete, which has been previously reported as having low activation.

Development of two-dimensional differential calibration method for a neutron dosimeter using a thermal neutron beam

We developed a new thermal neutron calibration method to be able to experimentally determine an energy response function of a neutron detector using a pulse parallel beam and the time-of-flight (TOF) technique. The calibration method was experimentally demonstrated for a 3He proportional counter and an electric personal dosimeter using a pulsed thermal neutron beam from the research reactor, JRR-3M. The responses of the detectors were successfully obtained as a function of the neutron energy. To solve the point at issue for the calibration method, we also propose an idea of an improved calibration method using a pulsed narrow beam, the TOF technique and a beam scanning technique. The improved calibration method does not require detailed information of the detector structure.

Quantitative Evaluation of Ion‐implanted Arsenic in Silicon by Instrumental Neutron Activation Analysis

Certified reference materials (CRMs) of shallow arsenic implants in silicon are now under development at the National Metrology Institute of Japan (NMIJ). The amount of ion‐implanted arsenic atoms is quantified by Instrumental Neutron Activation Analysis (INAA) using research reactor JRR‐3 in Japan Atomic Energy Agency (JAEA). It is found that this method can evaluate arsenic amounts of 1015 atoms/cm2 with small uncertainties, and is adaptable to shallower dopants. The estimated uncertainties can satisfy the industrial demands for reference materials to calibrate the implanted dose of arsenic at shallow junctions.

Analytical basis for neutron-activation analysis measuring nuclides witha half-life of second order.

日本原子力研究所の研究用原子炉JRR-3Mの放射化分析設備(PN-3)を使用し,半減期秒オーダーの短寿命核種を利用する中性子放射化分析(NAA)の基礎検討を行った.PN-3は,高速の気送管照射装置と高計数率用γ線スペクトロメーターから構成され,短寿命核種を利用したNAAを迅速に行うことができる.短寿命核種NAAで重要な高計数率γ線測定法,照射カプセル材質,中性子束の変動等基礎条件の検討を行い,(n,γ)反応によって半減期0.7～100秒の放射性核種を生成する20元素について,分析感度と検出限界を測定した.本法ではSc,In,Dy,Hfが最も高感度であり,その検出限界は4.2～14ngであった.又,他の方法では定量が困難なFの検出限界は530ngであった.本法が有効な元素F,Se,Sc,Hf,In及びDyについて,各種標準物質等の分析に応用し,精度,正確さ及び検出限界を評価した.