A gamma-emitting radionuclide is commonly measured qualitatively and quantitatively using a high-purity germanium (HPGe) detector. The precision of the measurement is determined by the HPGe detectors' performance. In this work, the long-term performance of the HPGe detector in the Central Laboratory for Radioactivity Measurements Intercomparison and Training (CLERMET) is evaluated using statistical analysis. The minimal detectable activity (MDA) and the detection limit (LD) were computed. The Full Energy Peak Efficiency (FEPE) was calculated using a standard mixed gamma solution source and confirmed using samples from the International Atomic Energy Agency (IAEA) (PTs). The acquired data allowed for the determination of the resolution, peak shape, and peak to Compton ratio of the HPGe detector as a function of gamma-ray energy due to the long-term operation. FWHM, FWTM, FWFM and both ratios of FWTM/FWHM and FWFM/FWHM were determined at 1332 keV (60Co). The findings are used to discuss the detector's long-term performance stability. Even after a lengthy time of use, the results reveal that detector performance has no effect on the full energy peak efficiency (FEPE). The laboratory results were in good agreement with the target value based on the IAEA PTs, confirming the laboratory's dependability and traceability. For method validations, Quality Assurance and Quality Control are required to improve the reliability and accuracy of results as well as to demonstrate the laboratory's performance and trustworthiness.Different analytical methods are developed for the determination of uranium isotopes in environmental samples using non-destructive and destructive analysis. Choice of an accurate and precise technique to get better performance and quality is essential for the results assessment and improvement. In this work different methods (Non-destructive method based on gamma spectrometer and destructive methods based on alpha spectrometer) were described to implement routine method for uranium isotopes determination in environmental samples. A set of IAEA reference certified samples were used for method verification.