Validation of a radiochemical method for the determination of 55 Fe and 63 Ni in water and steel samples from decommissi
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Validation of a radiochemical method for the determination of 55Fe and 63Ni in water and steel samples from decommissioning activities J. A. Corcho‑Alvarado1 · H. Sahli1 · S. Röllin1 · C. von Gunten1 · R. Gosteli1 · J. Ossola1 · M. Stauffer1 Received: 28 April 2020 © Akadémiai Kiadó, Budapest, Hungary 2020
Abstract We present the validation of a radiochemical procedure for the determination of 55Fe and 63Ni in water and steel samples from nuclear decommissioning activities. The in-house validation was an essential requirement of the accreditation to ISO/ IEC 17025. A combination of co-precipitation, anion chromatography and extraction chromatography steps was used for separating and purifying both radionuclides. The activities were measured by liquid scintillation counting. Due to the lack of reference materials, the method was validated by analysing simulated samples and by the standard addition technique. The parameters precision/accuracy, repeatability/linearity, selectivity/specificity, decision threshold, detection limit and uncertainty of the method were evaluated. Keywords 63Ni · 55Fe · Steel · Water · Nuclear decommissioning
Introduction After 47 years of continuous operation, the Mühleberg Nuclear Power Plant (NPP) in Switzerland was permanently shut down in December 2019. Nuclear decommissioning has therefore become an important issue in Switzerland. The decommissioning of this NPP started in January 2020 and will continue for approximately a period of 15 years. One of the most important decommissioning activities will be the dismantling of the nuclear reactor. Materials and equipment near the reactor case may be activated by the long-term irradiation with neutrons from the reactor core and can therefore be radioactive [1, 2]. Before dismantling and stocking these materials/equipment, they must be checked for radiation [2]. The radiological characterisation is essential for a cost-effective dismantling planning and for minimizing the radiation exposure of the staff involved in dismantling activities. A large number of neutron activated radionuclides are gamma emitters and their contents in the construction materials of the reactor can be rather easily determined by nondestructive methods like gamma-ray spectrometry [2, 3]. Some important radionuclides are, nonetheless, alpha or beta * J. A. Corcho‑Alvarado [email protected] 1
Nuclear Chemistry Division, Spiez Laboratory, Federal Office for Civil Protection, 3700 Spiez, Switzerland
emitters and destructive methods need to be used for their analyses. Iron-55 (55Fe) and nickel-63 (63Ni) are among the so-called difficult-to-measure radionuclides. Both radionuclides can be produced by neutron activation reactions in the structural materials of a nuclear reactor [1, 2]. 55 Fe (half-life: 2.747 years) is the most abundant neutron activated radionuclide in a nuclear power plant shortly after shutdown [4]. 55Fe is produced by the reactions 54Fe(n,γ)55Fe and 56Fe(n,2n)55Fe (Table 1). This radionuclide can be found in high levels in steel, and at
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