A study on the establishment of a method for determining H-3 radioactivity in the atmosphere

Project information:
- Managerial level: Ministry
- Duration: 02 years (From January 2013 to December2014)
- Contact email: thuhaus@gmail.com

        The project, led by Nguyen Thi Thu Ha in collaboration with colleagues at the Environmental Radioactivity Monitoring and Impact Assessment Centre, and Nuclear Technique Application Centre, Institute for Nuclear Science and Technology (INST) aims to successfully build up a technical procedure for determining Tritium (denoted as H-3) radioactivity in the atmosphere (using the modern MARC-7000 sampler), which can be widely used in future. The project also aims to obtain initial background information about the radioactivity of H-3 in the air in Hanoi.

        In order to achieve the goals, the project team divided the research content into four main items as follows:

          - Item 1: Providing an overview on H-3;

          - Item 2: Carrying out the formulation of method for determining H-3      radioactivity in the atmosphere;

          - Item 3: Recapitulating the research findings to propose an analysis        procedure for determining the radioactivity of H-3 in the atmosphere;

          - Item 4: Developing practical applications.

       After the implementation of the project in two years, the team obtained remarkable results. The analysis procedure for determining the radioactivity of H-3 in the air was successfully established with high quality, reliability and applicability in practice. The H-3 minimum detectable activity (MDA) in the atmosphere was then at 4mBq/m3. For the confirmation of the procedure, 24 air samples in Hanoi (including 12 samples in dry season and 12 others in rainy season; 2 samples per week) were collected in order to implement H-3 analysis, sample enrichment and purifying, and determining H-3 concentration in the collected samples. The results of the experiment indicated that:

          - Average efficiency of H-3 collection in the atmosphere was 74.82%;

          - Average activity error was 9.62% (the highest value stood at 10.65%);

          - The minimum radioactivity of H-3 in the 24 samples was 13.42mBq/m3;

          - The maximum radioactivity of H-3 in the 24 samples was 38.15mBq/m3;

          - The monthly average radioactivity of H-3 was 22.39mBq/m3 with the    standard deviation of 4.84mBq/m3. This value was 5.6 times higher than MDA value and equivalent to H-3 background level in several countries.

       These findings were presented at the National Nuclear Science and Technology Conferences in 2013 and in 2015.

       At present, in the hope of continuously gathering statistical data on H-3 concentration in Hanoi atmosphere to meet the needs of radiation monitoring, as well as of effective utilization of the MARC-7000 Tritium sampler, the project team has been collecting Tritium air samples by the MARC-7000 system with the frequency of 2 pairs of samples per month, in which, each pair (including one sample for Tritium vapor (HTO) analysis and the other for gaseous Tritium (HT) analysis) has been collected in two weeks.

       It was stated that the research results made a considerable contribution to the development of research method and monitoring the environmental radioactivity to meet the technical requirements of Vietnam national network on environmental radiation monitoring and early warning. In addition, the obtained results provided vital items of data for the preliminary investigation of H-3 radiation background in the atmosphere to monitor its variation due to activities of nuclear power plants (NPPs) in compliance with radiation safety standards through three periods, including before construction, under construction and equipment installation, and in operation.

 INST