National Physical Laboratory

Neutron Metrology

The NPL Neutron Metrology Group (NMG) operates world-leading facilities for measuring neutron source emission rates and providing an extensive range of accelerator- and source-based calibration fields.

Neutrons have many uses. Their ability to induce nuclear fission makes them fundamental to nuclear power. Their penetrating nature makes them useful probes into the composition and structure of materials. In addition to their industrial uses they have medical applications, such as isotope production. In all cases, it is important to know how many neutrons there are, and what risk they pose to anyone present.

A number of radionuclide sources (with broad energy spectra) are available at NPL for measurement services, as are monoenergetic neutrons derived from the NMG's 3.5 MV Van de Graaff accelerator.

Another key area of the NMG's capabilities is field measurements using active and passive systems to measure neutron fluence rates and energy spectra. Also available are several novel instruments such as those for measuring cosmic ray doses to air crew.

Research is undertaken within the Group to develop the range of standards and to address some of the deficiencies of neutron measuring devices.

Neutron Users' Club

The Neutron Users' Club (NUC) acts as a focal point for discussion of the problems of neutron measurements. It aims to facilitate the exchange of information between members on research and development activities in this area and on the neutron facilities in the UK.

Useful Links

UK Nuclear Science Forum (UKNSF),
and Nuclear Data Advice and Links
The UKNSF provides a focal point for nuclear data experimenters and evaluators in the nuclear industry, nuclear medicine and protection of the environment.


The NMG collaborates with other NMIs worldwide and is keen to extend its collaborative activities.
Further collaboration activities


Please note that the information will not be divulged to third parties, or used without your permission