Vol.2,

379

This paper introduces the principles, instrumentation, implementation, and industrial applications of an on- line thermal neutron prompt- gamma element analysis system (using a ²⁵²Cf neutron source, Am- Be neutron source, or neutron generator). The energy resolution of the system at the H prompt- gamma full- energy photopeak (2.22325 MeV) is 3.6 keV. The concentration measurement error of Al₂O₃, Fe₂O₃, CaO and SiO₂ is ±0.3%, ±0.1%, ±0.4% and ±0.4%, respectively. The system has been tested on- site at both the Shandong and the Zhengzhou Aluminum Works. Our preliminary on- site measurements confirm that the stability, reliability, measurement range, and accuracy of the system can meet the requirements of the aluminum production process. Facilitation of this measurement at aluminum plants is expected to reduce plant costs by over 3 million dollars annually through reduced energy consumption, more rapid qualification of pulps being mixed during the production process, and in reduced labor costs.

283

An expert system for neutron activation analysis has been designed on personal computer. It is mainly structured by means of the MDBS GURU, and composed of three subsystems: spectrum analysis, experiment design and data management. The gamma spectra from multiple channel analyzer can be treated conveniently with conventional methods and/or intellectualized isotope identification based on expert experiences. Fuzzy variable and its algebra are employed for inferring and expression of some conclusions. A procedure for quality control has been created to check the analytical quality. Suggestion of planning an experiment for a certain material can be obtained, and a gamma spectrum can be predicted or simulated. There is a data bank for saving the element concentrations.

312

A combination of Soxhlet extraction, column chromatography and INAA with GC and GC- MS was used in this work for the study of the abundance patterns of 36 trace elements and their correlation in nearly 100 samples of crude oil and organic materials extracted from oil- forming source rocks from 10 main Chinese oilfields. The low V/Ni ratios of 0.01 to 0.3 state the oil- forming continent environment. The geochemical significance hinted from other trace element abundances is also briefly discussed.

463

This paper discusses a novel application of PIGE for the determination of ¹³C in breath sample. Samples of human breath, urea, glucose, benzamide, barium carbonate were analyzed against tank CO₂ and graphite standard. An accuracy check of the ¹³C determination (with reference to mass spectrometric "True" results) gave a relative error of only- 0.4% for PIGE. The performance of different standard in this determination was assessed. Relative standard deviation for the determination of ¹³C isotopic abundance in breath samples were <20%. Then, if a 25% change is conservatively assumed observable in ¹³C abundance, an increase in ¹³C percent isotopic abundance from the natural 1.11% (average) to only 1.39% may be detected.

455

469

Elemental profiles of brain tumour tissues from 15 male patients of astrocytomas (grade I- III) and normal human brain tissues of 23 male age matched autopsies as controls have been studied by INAA. A total of 18 elements Se, Na, K, Br, Cl, Mn, Mg. S, Ca, Cu, Hg, Cr, Fe, Rb, Zn, Co, Sc and P has been determined for this purpose. The analytical results showed that compared with the normal brain tissues, concentrations of Ca, Fe, Cu, Zn, Mn, Br and Sc were significantly higher in tumour tissues and that of Rb, K and P were lower while no differences for contents of Mg, S, Cr, Na and Cl were observed. A negative correlation between P and Ca in malignant and normal brain tissues was observed.

289

The geological samples: Cretaceous- Tertiary (K- T) boundary clays, meteorites, volcanic lava, and ultrabasic rock were separated into carbonate, metal, sulfide, oxide, silicate and acid- resistant residue by a selective chemical dissolution procedure developed in our laboratory. Some conclusions were drawn by analyzing the chemical speciation of anomalous iridium in the above samples and especially by studying the characteristics of mineral components in those residue phases. (1) It is impossible that the anomalous Ir was caused by geochemical enrichment; (2) The iridium enrichment in the K- T boundaries did not necessarily associate with kerogen; (3) The volcano activity has participated in the extinction event at the end of Cretaceous; (4) Extraterrestrial impact was the trigger of K- T event. Then, we proposed a mixed model by which the extant anomalous Ir in K- T boundary clays was interpreted as a combined effect of extraterrestrial impact, volcano eruption and post- depositional redistribution.

303

A new method of geogas (soil gas) collection and analysis, is briefly introduced. A geogas collector is buried at shallow depth to collect volatile compounds for a period of 60- 90 days. The adsorbed compounds are analyzed by INAA. This paper presents the multi- elemental anomaly of a gold deposit, Southwest China. The element contents and the multielemental anomaly of geogas were compared with those in the near- surface soil around the collector, background of the collector, and in gold ores. The geogas anomaly on gold deposit is demonstrated as a direct indicator of subsurface deposits.

731

A new method of NAA for sediment movement study is presented in this paper. Through analyzing the natural sediment, the information about natural tracing agents has been obtained, which can show the direction of sediment movement and relative discharge of sediment transportation. Test results in some areas, such as Shantou Harbour and Hangzhou Bay, are in good agreement with those from normal hydrologic measurements and some results are not obtainable with the latter. The NAA is economical, practical and reliable, and should be widely used in engineering practice.

491