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Calibration of ambient dose equivalent rate meters in reference fields of neutron radionuclide sources

The ambient dose equivalent or ambient dose equivalent rate for neutron radiation is measured with portable direct-reading instruments. For numerous applications (e.g., for checking permissible boundary values for the dose rate at a CASTOR transport container), it is prescribed that the instruments being used have been calibrated in order to ensure measured values traceable to a primary standard.

For the calibration of area neutron monitors, radionuclide neutron sources are used at PTB. The calibration, performed in accordance with the international standards ISO 8529, Part 1 - 3 and IEC 61005, covers the determination of the calibration factor, of the linearity of the response, and of the photon sensitivity. The calibration factor of an area monitor must be independent of the conditions prevailing in the measurement room, i.e., it is to be determined for a free-field fluence rate in vacuum. The radiation from neutrons directly from the source is, however, always accompanied by a scattered radiation component which has to be corrected for using a suitable method (e.g., the shadow object method or the distance variation method, see ISO 8529-3).

The measurement results are compiled in a calibration certificate. The measurand is usually the ambient dose equivalent H*(10). Calibrations with respect to the neutron fluence rate are also possible. These services are provided in accordance with the quality assurance system of PTB. The fees are fixed in accordance with the regulations governing charges for services rendered by the PTB.


In case of questions or to interest in calibrations please contact the Working Group (Opens window for sending emailneutronendosimetrie(at)ptb.de).