H. Matsue

Efficiency calibration of a Ge detector in the 0.1–11.0 MeV region

Abstract An efficiency curve was constructed for a large-volume Ge detector located at the thermal-neutron beam line of the JRR-3M reactor at the Japan Atomic Energy Research Institute (JAERI). The calibrations for γ-ray energies below 2754 keV were accomplished with a large number of radioactive sources and above 2754 keV with the 12 C(n,γ) and 14 N(n,γ) reactions. This detector and its efficiency curve were subsequently used to determine accurately the photon emission probabilities of γ rays from the decays of 56 Co (T 1/2 =77 d ) and 66 Ga (9.5 h ) and from the 35 Cl(n,γ) reaction. These radiation sources can serve as secondary standards for efficiency calibrations.

Determination of boron in Japanese geochemical reference samples by neutron-induced prompt gamma-ray analysis

Determination of ppm levels of B in 21 igneous and sedimentary rocks of the Japanese geochemical reference samples prepared by the Geological Survey of Japan (GSJ) has been performed by neutron-induced prompt γ-ray analysis (PGA) using cold and thermal guided neutron beams of the JRR-3M. Owing to the Doppler broadened γ-ray line of B 478 keV, many elements such as Na, Ni, Cl and so on showed spectral interference in the determination of B. The interference was corrected by computer fitting and a reference peak method. The analytical results obtained by the present method almost agreed with the GSJ values recommended in 1994 within the standard deviation of the recommended values. Sodium contents determined by the PGA in the reference rock samples are also reported.

Multi-element analysis of environmental samples by cold and thermal guided neutron induced prompt gamma-ray measurement

Non-destructive multi-element determination in environmental samples by neutron-induced prompt γ-ray analysis (PGA) has been investigated. Comparative standardization for the elements including H, B, C, N, Na, Mg, Al, Si, P, S, Cl, K, Ca, Ti, Mn, Fe, Co, Cd, Sm, Gd, Hg by PGA has been carried out using the cold and thermal guided neutron beams of JRR-3M reactor and then several environmental reference materials have been analyzed. Accuracy and precision of better than 20% were found for these elemental analyses except for H, C, N and Cl in biological samples. Detection limits in various environmental matrices were 25 to 820 ng/g for B, Cd, Sm and Gd, 1.1 to 820 μg/g for H, Na, S, Cl, K, Ti, Mn, Co and Hg, and 0.031 to 10% for C, N, Mg, Al, Si, P, Ca and Fe. The present method is being applied to environmental studies of post war Persian Gulf together with INAA and ICP-MS.

Neutron induced prompt gamma-ray and instrumental neutron activation analyses of urban estuarine sediments

Neutron induced prompt γ-ray analysis (PGA) and instrumental neutron activation analysis (INAA) have been applied to the sediments collected from the Tama River estuary in Tokyo, Japan. The vertical distribution of 24 elements in the sediments was determined and the factors goveming the vertical profiles have been discussed. Major elements are distributed depending on weathering that proceeds much with increasing depth. Cadmium is highly concentrated in the deeper layer where sulphate ion is reduced to hydrogen sulphide. The distribution of several rare earth elements is also presented

The recommended k0-factors for neutron-induced prompt gamma-ray analysis and the prompt gamma-ray emission probabilities

Recommended k0-factors for gamma-lines of 24 elements useful for neutron-induced prompt gamma-ray analysis (PGA) and which are not influenced by neutron spectrum differences were obtained from the k0-factors measured with the cold and thermal neutron guided beams of JRR-3M, by statistical calculation. The prompt gamma-ray emission probabilities were derived from the recommended k0-factors using atomic weight, isotopic abundance and thermal neutron capture cross section all related to the k0-factors, for which one can obtain accurate data. The derived gamma-ray emission probabilities for the light elements (H to Ca) agreed well within ±10% with those of the ENSDF values, which reflect recent data while the agreement for heavy elements (Ti to Pb) was ±40% with those of the ENSDF, which are still composed of old data.

Neutron spectrum correction of k0-factors for k0-based neutron-induced prompt gamma-ray analysis

Neutron spectrum correction has been attempted for the k0-factors of the non-1/v elements which are affected neutron spectrum difference. Effective g-factors and Westcott g-factors, which are neutron spectrum correction factors obtained from an actual neutron spectrum and the Maxwellian distribution, respectively, for the non-1/v elements were calculated using their neutron cross section data of JENDEL-3.2. The neutron spectrum correction was made for the measured k0-factors of the non-1/v elements such as Cd, Sm and Gd with the cold and thermal guided neutron beams of JRR-3M using the g-factors. The corrected k0-factors between the cold and thermal neutron beams using both g-factors for both neutron beams agreed well for Cd. However, 9 to 44% deviations have been found for Sm and Gd, respectively.

Non-destructive determination of trace amounts of iodine in biological samples by epithermal neutron activation and Compton suppression gamma-ray spectrometry

In order to investigate the ingestion of iodine by human body and to know its content in organs, instrumental epithermal neutron activation analysis was used in conjunction with Compton suppression gamma-ray spectrometry by measuring the 128I short-lived nuclide. The interferences of 24Na and 38Cl induced from NaCl in a sample were reduced by factors of about 6 and 15 to 41 by employing the epithermal neutron activation and Compton suppression gamma-ray spectrometry, respectively. The present method can be used to determine iodine at levels higher than 11 ppb. It was applied to the determination of iodine of more than 35 ppb in various biological reference materials.

Measurement and evaluation of k0 factors for PGA at JAERI

In order to determine multiple elements by k0 standardization-based neutron induced prompt gamma-ray analysis (PGA), measurements and evaluation of k0 factors for the elements have been performed. The k0 factors using Cl as a comparator for 27 elements, which are effective for the analysis by PGA, were measured with precision almost less than 3% using the cold and thermal guided neutron beams at JRR-3M. The accuracy of the k0 factors were better than 10% except for the non-1/v elements of Cd and Sm. Neutron spectrum correction is necessary for common use of k0 factors of the non-1/v elements.

Usefulness of Prompt Gamma-Ray Analysis with Guided Neutron Beams Compared to NAA

A neutron-induced prompt γ-ray analysis (PGA) has become widely utilized due to the improved analytical sensitivities and detection limits especially by using low energy guided neutron beams. Current studies on the low energy neutron guided beam PGA are reviewed. Historical backgrounds, current analysis systems, advantages when compared with conventional NAA, standardization for elemental determination and analytical applications in JAERI of the guided beam PGA are described.

Vertical distribution of elements in non-polluted estuarine sediments determined by neutron induced prompt gamma-ray and instrumental neutron activation analyses

Neutron induced prompt gamma-ray analysis (PGA) and instrumental neutron activation analysis (INAA) have been applied to the sediments collected from the Yasaka River estuary in Oita Prefecture, Japan. The vertical distribution of 33 elements in the sediments has been determined and compared with that in more polluted estuarine sediments. While the S content increased with increasing depth because of a sulphide accumulation under reducing condition, the increase in sulphide-forming elements such as Ag, Cd, Co and Zn was not observed in the deeper section of the Yasaka River estuarine sediments.