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Published on: November 9, 2015
Standardisation of 210Pb
1Centre for Ionising Radiation Metrology, National Physical Laboratory, Teddington, Middlesex, UK. denise.woods@npl.co.uk
Summary
Standardizing lead-210 (210Pb) is challenging due to its daughters. Chemical separation of 210Pb and using liquid scintillation-gamma coincidence counting improved accuracy for this important radionuclide.
Area of Science:
- Nuclear physics
- Radiochemistry
- Metrology
Background:
- Standardizing lead-210 (210Pb) is complex due to its decay daughters, bismuth-210 (210Bi) and polonium-210 (210Po).
- Low-energy beta emissions from 210Pb and low detection efficiencies in proportional counters necessitate large extrapolations, increasing uncertainty.
- Conventional 4π(PC)-gamma coincidence techniques are limited by these factors.
Purpose of the Study:
- To develop a reliable standardization method for 210Pb.
- To overcome the challenges posed by daughter products and low-energy emissions.
- To reduce uncertainties in 210Pb activity measurements.
Main Methods:
- Chemical separation of 210Pb from its daughter products (210Bi, 210Po).
- Standardization of purified 210Pb using the 4π(LS)-gamma coincidence technique.
- Calibration of a germanium spectrometer using Americium-241 (241Am) for photon emission measurements.
Main Results:
- A chemically separated 210Pb solution was successfully standardized.
- The 4π(LS)-gamma coincidence technique provided a more reliable measurement.
- Germanium spectrometry, calibrated with 241Am, was suitable for characterizing photon emissions.
Conclusions:
- Chemical separation is crucial for accurate 210Pb standardization.
- The 4π(LS)-gamma coincidence method offers improved accuracy over 4π(PC)-gamma methods.
- Ionization chambers are unsuitable for 210Pb standardization due to low-energy photon emissions.
