T. Sy N.’s scientific contributions

White rice is a main food for Asian people. In the framework of Forum for Nuclear Cooperation in Asia (FNCA), therefore, the eight Asian countries: China, Indonesia, Japan, Korea, Malaysia, the Philippines, Thailand and Vietnam selected white rice as a common target sample for a collaboration study since 2008. Accordingly, rice samples were purchased and prepared by following a protocol that had been proposed for this study. The groups of elements that were analyzed by using neutron activation analysis in the white rice samples were toxic elements and nutrient elements, including: Al, As, Br, Ca, Cl, Co, Cr, Cs, Fe, K, Mg, Mn, Na, Rb and Zn. The analytical results were compared between the different countries and evaluated by using the Tolerable Intake Level of World Health Organization (WHO) and Recommended Dietary Allowance or Adequate Intake (AI) of the U.S. Institute of Medicine (IOM) guideline values. These data will be very useful in the monitoring of the levels of food contamination and in the evaluation of the nutritional status for people living in Vietnam and other Asian countries.

An auto-pneumatic transfer system has been installed at the Dalat research reactor for rapid instrument neutron activation analysis based on very short-lived nuclides. This system can be used to perform short irradiations in seconds either in the vertical channel 13-2 or in the horizontal thermal column of the reactor. The transferring time of sample from irradiation to measurement position is approximately 3.2 seconds. A loss-free counting system using HPGE detector has been also setup in compacting with the pneumatic transfer system for measurement of sample’s activity, automatically starting for data acquisition at irradiated sample’s arrival. This new facility was tested and shown to have high potential for the determination of short-lived nuclides with half-lives from 10 ¸ 100 seconds. This work presents the results of timing parameter measurements, characterization of irradiation facilities, and application of this system to determining Selenium concentration in several biological reference materials.