Neutron reference fields from radionuclide sources

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The International Organization for Standardization (ISO) recommends different radionuclide neutron sources for the calibration of measuring instruments for use in radiation protection in its standards ISO 8529, part 1-3. An irradiation facility with such sources (²⁵²Cf, unmoderated and moderated by 15 cm D₂O, ²⁴¹Am-Be) is available at PTB for calibrations of area monitors as well as calibrations of and comparison measurements for personal neutron dosemeters. The measuring quantities are the ambient and the personal dose equivalent. Furthermore, spectrometers and neutron detectors are examined and calibrated with respect to neutron fluence.

The radiation fields of the radionuclide sources are well characterized. The strengths of the neutron sources were determined at the British metrology institute, NPL, by the primary method manganese bath method. The spectral neutron fluence at the place of measurement was measured with spectrometers and determined by neutron transport calculations. The relative standard uncertainty for the neutron fluence is 0.7 % to 2.3 %, depending on the neutron source. The neutron fluence also serves to determine dose equivalent quantities (e.g., the ambient dose equivalent) using the recommended fluence-to-dose conversion coefficients.

Irradiation facility with radionuclide sources (room size: 7 m x 7 m x 6.5 m):

• ²⁴¹Am-⁹Be(α,n)
• ²⁵²Cf(sf)
• ²⁵²Cf(sf) with D₂O moderator

Details of the calibration capabilities with radionuclide neutron sources can be found here.

For further information please contact the Working Group
(neutronendosimetrie(at)ptb.de).

Literature

• Kluge, H (1998):
  Irradiation facility with radioactive reference neutron sources: Basic principles
  PTB-Report N-34. Physikalisch-Technische Bundesanstalt, Braunschweig.