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Neutron-induced prompt gamma-ray analysis (PGA) was applied to seven meteorite samples (Allende, Zagami, Acfer 209, ALH77005, ALH84001, EET79001 and Neagari). Samples were irradiated in both the thermal neutron and the cold neutron guided beams of JRR-3M at JAERI. Multiple samples of an Allende standard powder were analyzed for Si using two different methods: (1) the comparison method, using a Si standard, and (2) the mono-standard method, using Fe as an internal reference element. The Si concentrations determined by these two methods are in good agreement with literature values. The analytical sensitivity for Si using the cold neutron guided beam is -14.3• higher than that for the thermal neutron guided beam. Other elements determined (B, Ca, Ti and S) also showed higher sensitivities using the cold neutron beam. The other meteorites studied showed some anomalous B and S values likely due to the effects of terrestrial weathering/contamination.

Nondestructive determination of major and trace elements within voluminous materials has been demonstrated by prompt y-ray neutron activation analysis 9 Some fragmented pieces of pottery bowls considered to have been produced in the late 18th century were analyzed by a new internal monostandard method, and noticeable differences of the elemental contents and significant correlations of the elemental distributions were observed among the samples 9 The possibility of identification of producing areas of unearthened material is demonstrated by the analytical results and the applicability of this method to the investigation of precious samples in a completely nondestructive way is verified in practice 9

When extraterrestrial materials are returned to the earth by future space missions, these materials are to be subjected to the initial examination. For such purposes, measurements are desired to be done non-destructively. In this study, we investigated the applicability of non-destructive prompt gamma-ray analysis (PGA) for determining chemical composition of the returned materials, focusing on levels of induced radioactivities and the effect on isotopic composition by PGA. Under current conditions applied for the PGA facility at the Japan Atomic Energy Research Institute, essentially no residual radioactivities remain after appropriate cooling, making the same specimen analyzed by PGA usable for further research without any restriction. The effect on isotopic composition by PGA was examined both for neutron-induced reactions and for neutron-induced nuclear fission of 235 U. No significant effect can be brought by neutron-induced reactions even for some noble gas nuclides such as 80 Kr and 128 I, which can be augmented by (n, γ ) reactions on neighboring halogens. Neutron-induced nuclear fission reactions of 235 U yield essentially no effect on isotopic composition. In addition, PGA has several advantages over other nondestructive analytical methods such as instrumental neutron activation analysis (INAA) and synchrotron radiation x-ray fluorescence (SR-XRF); INAA leaves a significant level of induced-radioactivities and SR-XRF yields less reliable and less accurate values for elemental composition. Judging from these features and characteristics, it is concluded that PGA can be one of the most suitable analytical methods potentially applicable for initial analysis of returned samples from space.

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