A neutron-induced prompt -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.
The k0 standardization method has been studied and applied at JAERI for the accurate determination of multielements by neutron-induced prompt gamma-ray analysis (PGA). The k0 factors for 26 elements using Cl as a comparator were measured by the cold and thermal neutron guided beams of JRR-3M with an uncertainty less than 3% except for a few elements. The k0 factors for most elements obtained with both cold and thermal neutrons agreed within 3%, and agreed also with those measured at other cold and thermal neutron guided beams within 10%, except for a few elements. Multielement determinations in reference materials were performed using the k0 factors obtained to evaluate the accuracy and precision of this work.
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.
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.
Neutron spectra were measured by the time of flight method using a rotating disk chopper system in the JRR-3M prompt gamma
ray analysis system. Effective g-factors for non-1/v elements such as Cd, Sm and Gd were calculated from the measured neutron spectra and the neutron cross section data, and
they was used for correcting the k0-factors. The resulting k0-factors for the cold and thermal neutron beams agreed within 10%. Furthermore, the prompt gamma ray emission probabilities
of Cd, Sm and Gd were derived from the corrected k0-factors using other relevant physical constants.
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.
Non-destructive multi-element determination in environmental samples by neutron-induced prompt -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 g/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.
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.
A molecular rocket using nuclear recoil in metallocene inclusion complex has been studied. Sublimatographic separation of liberated metallocene molecule from metallocene cyclodextrin complex suggested that at least a small fraction was due to this molecular rocket process with soft landing, which causes no serious decomposition. In the retention-recoil energy relation, analysis also revealed a part which suggested the presence of the molecular rocket with and without decomposition.
Authors:E. Furuta, H. Nakahara, Y. Hatsukawa, H. Matsue, and H. Sakane
In Japan, cosmetics claiming hormesis effect are available through Internet. Although these cosmetics show the contents, they
never mention the minor elements and radioactive sources. The existence of radioisotopes, however, was observed by measurements
of the gamma-rays with a HPGe detector. In this study, in order to clarify the contents of trace elements, the hormesis cosmetics
including radioactive sources were analyzed using INAA, PGAA and NAA with multiple gamma-ray detection (NAAMG). Nineteen elements
were analyzed quantitatively in hormesis cosmetics by INAA, PGAA and NAAMG and 16 elements were detected qualitatively by