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An approach based on sequential extraction separation and the subsequent ICP-MS measurement was introduced to determine 99Tc in radioactive wastes. The radwastes were firstly alkaline-fused and the 99Tc was separated by a sequential solvent extraction prior to ICP-MS measurement. NaDDC was selected as a chelation reagent in the solvent extraction processes. The influence of HCl and matrix concentration on the recovery yield and the effectiveness of removing isobar and unwanted radionuclides, such as 137Cs, 54Mn, 60Co and 110mAg, were evaluated. The designed sequential extraction procedure was optimized by an extraction experiment. The proposed technique is proven to be a simple and practical alternative for 99Tc determination in low-level radioactive wastes; chemical separation of 99Tc can be simplified and preconcentration such as precipitation and/or ion exchange, before the solvent extraction, can be excluded.

Performance of a 3.8 × 3.8 cm BGO detector used as a gamma ray spectrometer was tested after thermal neutron bombardment. The drift of photopeak channel as well as change of absolute counting efficiency and photopeak energy resolution became severe as the BGO detector was bombarded with thermal neutrons to 1013 nth/cm2. Irradiation with thermal neutrons beyond 1015 nth/cm2 disabled the BGO detector as a gamma ray spectrometer due to the intense interference from internal radioactivity induced by neutron reactions.

Application of bismuth germanate detector to high-energy gamma ray spectrometer is demonstrated. A 2.5″ × 2″ BGO detector is used to measure the 6.129 MeV decay gamma ray emitted from 16 N in reactor coolant, to identify the 10.829 MeV prompt photon for determination of explosive-like material, and to survey 5–15 MeV cosmic radiation on an elevated mountain. In all cases the BGO outperforms the conventional NaI scintillator due to its higher density and detecting efficiency.

A coincidence gamma spectrometer has been used to measure the 134Cs activity in the presence of intense interference from 137Cs and from natural radioactivity in environmental samples. The coincidence spectrometer, with a large BGO scintillator for gating purposes and a HPGe detector for the coincident spectrum, is designed to enhance the coincidence full energy peak counting rate of 134Cs and to suppress the single photon counting rate of 137Cs as well as other natural radionuclides. An overall enhancement factor of 120 is obtained in coincidence while the interfering full energy peaks are substantially suppressed. Absolute counting efficiency of the coincidence spectrometer is calibrated for environmental samples with activity ratios of A( 134 Cs )/A( 137 Cs ) down to 5 × 10−5. Other applications and the flexibility of the spectroscopic system are discussed.

High-resolution gamma-ray spectra of radioactive aqueous samples with volume of 0.1–4.0 L were measured using a 20% relative efficiency germanium detector. A total of 308 spectra, covering the photoenergy range of 50–1500 keV, were sorted and analyzed with various sample geometries. The optimum dimensions of a Marinelli-like container were obtained to maximize the count rate of aqueous samples up to 4 L. Relations among the radius, height and volume of the optimum geometry for the Marinelli-like container are established.