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Nuclear metrology

Radioactive gas standards

Providing gas standards for the calibration of stack, area and environmental monitoring

Gas standards of 3H, 14C, 85Kr and 133Xe are realised by means of absolute length-compensated internal-gas proportional counting. Our system can be used to measure gases over a range of activity concentrations with an accuracy as low as ± 1 % (k = 2). The system is compatible with a range of carrier gases and container types, including cylinders and glass ampoules.

Current areas of research include:

  • Short-lived radionuclides – development of methods for production of gases for direct production, calibration and measurement, which supports stack monitoring. This can be used in medical isotope production facilities, nuclear power plants and criticality monitoring.
  • Radiocarbon gas standards – calibration and standards of a new generation of instruments for environmental-level 14C labelled methane and carbon dioxide. These instruments have applications in biogas security and nuclear waste repository monitoring.
  • Inter-comparisons – participation with other NMIs and metrology laboratories to support traceability to the SI. Currently, NPL is organising an inter-comparison of 133Xe, which is a key signature of nuclear weapons testing and is globally monitored by the Preparatory Commission for the CTBTO.
  • Flow-through dilution rig – development of a rig that will be capable of traceably diluting a radioactive gas standard. It is intended to produce dilute streams of tritium and 14C gases to environmental levels for the calibration of bubbler systems, which are commonly used at nuclear facilities.

Find out more about NPL's Standard radionuclide solutions service

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