Determination of technetium-99 and neptunium-237 in environmental samples by inductively coupled plasma mass spectrometry

Critical comparison of radiometric and mass spectrometric methods for the determination of radionuclides in environmental, biological and nuclear waste samples

“…Detection limits of 1 mBq and 8 mBq were reported for GM counter and silicon detector, respectively for 50 hours counting [163,164]. LSC has a high counting efficiency for 63 Ni (70%), it is therefore widely used for the determination of 63 Ni [18,[165][166][167][168][169], the reported detection limit of LSC is 14-37 mBq for 30-1000 minutes counting time [18,169]. A slightly higher detection limit of LSC results from the relatively high background count rate of LSC (3-10 CPM) compared to GM counting and silicon detector (0.2 CPM).…”

“…The interest in the determination of 63 Ni and 59 Ni results from the characterization of radioactive wastes for the decommissioning and disposal of nuclear waste, and the use in a number of applications including cosmic radiation studies, biomedical tracing and neutron dosimetry (Table 1) [18,[155][156][157][158]. 63 Ni is a pure beta emitting radionuclide (Table 4), the radiometric methods including windowless gas flow GM counters, beta spectrometry with semiconductor detectors and LSC have been used for its determination. 59 Ni decays by electron capture with emission of X-rays, it can therefore be determined by X-ray spectrometry.…”

“…In the determination of 63 Ni by gas flow GM counter or semiconductor detector, the 63 Ni has to be prepared as thin source to minimize self-adsorption. This is usually carried out by electrodeposited of Ni on a metal disk.…”

“…Because of the difficulties in identifying radioisotopes from the continuous energy spectrum of pure beta-emitters, they have to completely be separated from the matrix and other radionuclides before counting. Chemical separation of 63 Ni is usually carried out by precipitating nickel as a hydroxide and then extracting the Ni-DMG (dimethyl glyoxime) complex using either solvent extraction or extraction chromatography, sometimes combined with an anion exchange step. A decontamination factor of 10 5 or higher was obtained using a combination of these methods [18].…”

“…A decontamination factor of 10 5 or higher was obtained using a combination of these methods [18]. Chemical separation does not separate 63 Ni from 59 Ni, but since both 63 Ni and 59 Ni are produced by thermal neutron reactions with stable nickel 62 Ni (3.65%) and 58 Ni (68.1%), the initial activity ratio of 63 Ni/ 59 Ni is around 100 or higher, which means that only 63 Ni is measured by LSC counting. In addition, the signal of 59 Ni in LSC occurs in the low energy part of the spectrum, which makes the interference of 59 Ni to the 63 Ni spectrum very limited.…”