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Standardization of ²³⁷Np
Lizbeth Laureano-Perez1, R Fitzgerald1, R Collé1
1Physical Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899-8462, USA.
Standardizing Neptunium-237 (Np-237) activity measurements is crucial. Researchers confirmed that the Np-237/Protactinium-233 (Pa-233) radioactive equilibrium is disrupted during sample preparation.
Area of Science:
- Nuclear chemistry
- Radiochemistry
- Metrology
Background:
- Accurate quantification of radionuclides like Neptunium-237 (Np-237) is essential for nuclear applications.
- Standardization ensures reliable activity measurements for Np-237, a key actinide.
- Understanding ingrowth and decay of daughter products, such as Protactinium-233 (Pa-233), is critical for accurate standardization.
Purpose of the Study:
- To establish a certified massic activity for Np-237.
- To investigate the impact of sample handling on the Np-237/Pa-233 radioactive equilibrium.
- To validate measurement techniques for Np-237 standardization.
Main Methods:
- 4πβ liquid scintillation (LS) counting utilizing the CIEMAT/NIST efficiency tracing method with a tritium (³H) standard.
- High-resolution germanium detector (HPGe) gamma-ray spectrometry.
- 4πβ(LS)-γ(NaI) anticoincidence counting.
Main Results:
- Certified massic activity for Np-237 was obtained using the CIEMAT/NIST method with corrections for Pa-233.
- Confirmatory measurements by HPGe gamma-ray spectrometry and anticoincidence counting showed agreement within uncertainties.
- The Np-237/Pa-233 radioactive equilibrium was confirmed to be disturbed by dilutions and aliquot removal.
Conclusions:
- The applied methods provide reliable Np-237 standardization.
- Sample preparation procedures must account for the disturbed Np-237/Pa-233 equilibrium.
- Accurate Np-237 metrology is achievable with appropriate daughter nuclide corrections.
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