Improvement of the AMS-technique and applications to 3H and 59Ni Measurements

Abstract: Accelerator mass spectrometry (AMS) is a highly sensitive technique for counting atoms. Its main advantage in comparison with radiometric methods is the smaller amount of sample required (by a factor of a thousand). The method has a high efficiency and requires only some ten mg of sample material. The radioisotope 59Ni is of great importance in nuclear waste management in the nuclear industry. This isotope is produced by the neutron activation of the stable 58Ni, close to the core of nuclear reactors. Due to its long half-life, it is necessary to determine its activity concentration in the various construction materials in connection with classification and storage considerations. In this thesis, further development of the 59Ni detection technique, using the small 3 MV tandem accelerator in Lund, is presented. Some results of measurements on 59Ni samples from nuclear power plants are presented. Improvements of the detection and chemical purification methods of the stainless steel samples, to reduce the content of the interfering isobar 59Co have been made. In order to make heavy ion AMS feasible at the Lund accelerator facility, new improvements on the AMS technique and in the detection technique have been developed. The performance and the improvements of the new gas stripper with terminal pumping are presented. Charge state distributions for various isotopes used in AMS analysis have been measured. Characteristic X-ray cross-sections have been measured for Fe, Ni and Cu ions in connection with the 59Ni project. The radioisotope 3H is the most frequently utilized isotope in biomedicine, and has numerous applications, e.g. determination of total body water, metabolism studies, dosimetry measurements, etc. The development of tritium AMS is expected to have a great impact in biomedical research for two reasons: tritium is the most widely used radioisotope in biomedicine, and secondly, used in conjunction with 14C, it allows low-level, double-labelling experiments. In this thesis, development of the chemical procedure for sample preparation and of the tritium detection technique using a 3 MV tandetron accelerator at the Rossendorf Research Centre, Germany, are presented. The first measurements of the blood samples from patients after administration of tritiated water are presented.