Products & Services
Neutron measurement capabilities
Services
- Neutron fluence and dose standards: thermal
- Neutron fluence and dose standards: 50 keV to 17 MeV
- Neutron fluence and dose standards: radionuclide source based
- Measurement and Hire of Radionuclide Neutron Sources
- Field Measurement of Neutron Dose Quantities
Neutron fluence and dose standards: thermal
- Standardised thermal neutron fields: Characterised thermal neutron fields for the calibration of neutron sensitive devices and for irradiation purposes. The fluence rate is determined by the activation of gold or manganese foils in terms of known thermal neutron capture cross sections.
- Transfer standards for thermal neutron fields: The thermal neutron fluence rate can be measured at the customers’ premises using gold foils as the transfer standard. The fluence rate is determined in terms of the known neutron capture cross sections for gold.
Neutron fluence and dose standards: 50 keV to 17 MeV
- Standardised mono-energetic neutron fields: Well characterised mono-energetic neutron fields covering the greater part of the energy range from 8 keV to 6 MeV are available for the calibration of neutron sensitive devices and for irradiation purposes. The fields are characterised by measurements of neutron fluence rate, neutron energy and neutron energy resolution.
- Transfer standards (Long Counter): The DePangher long counter (PLC) is widely adopted as a secondary standard. Purchasers of PLCs may have their instrument compared with the NPL standard PLC. A PLC is also available on short-term hire.
Neutron fluence and dose standards: radionuclide source based
- Radionuclide source based neutron fluence standard: A variety of radionuclide neutron sources are available to provide well-characterised neutron fields for calibrating neutron sensitive devices or for irradiating samples. The sources include those types recommended by ISO (ISO 8529), i.e. 241Am-Be, 241Am-B, and both 'bare' and heavy water moderated 252Cf sources. Other sources available are: 241Am-Li and 241Am-F.
- HSE performance tests for dosimetry services that monitor external whole body fast neutron radiations. Neutron sources used are 252Cf and 241Am-Be as stated in the HSE measurement protocol. All dose equivalent ranges required by the HSE can be provided, the highest range being between 30 to 50 mSv for both 241Am-Be and 252Cf.
Measurement and Hire of Radionuclide Neutron Sources
- Standardisation of radionuclide neutron sources: The total emission rate of a radionuclide neutron source can be determined using the manganese sulphate bath technique (range of neutron emissions rate from 10 thousand per sec to 1000 million per sec) or a moderating assembly incorporating boron tri-fluoride proportional counters (100 per sec to 1 million per sec).
- Anisotropy correction factors: The emission of most radionuclide neutron sources is not isotropic. The variation of emission relative to the axis of the source is determined in a low-scatter area by means of a long counter.
- Hire of radionuclide neutron sources: A range of radionuclide source types, with measured neutron emission rates and anisotropy factors, are available for short-term hire. Shielded transport containers are also available.
Field Measurement of Neutron Dose Quantities
- Spectrometry for determination of neutron dose quantities: NPL has developed a number of well-characterised neutron spectrometry systems for 'in-the-field' neutron dosimetry. From measurements with one or more of these systems it is possible to derive information about the neutron energy spectrum and on a range of dosimetric quantities. Measurements can be made in mixed neutron and photon fields (i.e. around a medical linear accelerator) using a passive detector system.
- Measurement of dose quantities using micro-dosimetry: Tissue equivalent proportional counters measure dose deposition in tissue volumes with micro-metre dimensions and are capable of simultaneously measuring the absorbed dose from neutrons and gamma-rays in a mixed radiation field. Information about the radiation quality, and hence dose equivalent, can be derived from the measured micro-dosimetric spectra.
Contact
Customer Services tel: +44 20 8943 8637
E-mail: neutron_enquiries@npl.co.uk
Neutron Metrology products & services
- NPL is one of the few laboratories in the UK that can offer performance testing of dosimetry services for fast neutron radiation.
- Radiation levels at aircraft cruising altitudes are twenty times higher than at sea level. The main source is galactic cosmic radiation, primarily generated by exploding stars within our own galaxy.
- Microdosimetry is a useful tool in the measurement of radiation levels in the workplace and has one distinct advantage over other techniques: it records a spectrum that can be analysed to give separate photon and neutron dose rates and dose equivalent rates in a single measurement.
- NPL is one of the few national standards laboratories worldwide that offers an absolute measurement of the total emission rate of a radionuclide neutron source into 4π steradians.
- At NPL well-characterised mono-energetic neutron fields covering the greater part of the energy range 70 keV to 5 MeV are routinely available for the calibration of neutron sensitive devices or for irradiation purposes.
- NPL has particular expertise both in the measurement of neutron fields and in calculations with neutron transport codes. This expertise is available to customers in a variety of ways depending on the scope and nature of the work.
- NPL can undertake on-site spectrometry measurements which, in addition to providing information for radiation protection applications, can also be used for example to determine the neutron output from a range of devices.
- A variety of radionuclide neutron sources are available to provide, at NPL, well-characterised neutron fields for calibrating neutron sensitive devices or for irradiating samples.
- Well characterised thermal neutron fields are available at NPL for the calibration of neutron measuring devices e.g. area survey instruments or personal dosemeters, and for irradiation purposes.
- The transfer standard for thermal neutron fluence is based on the activation of gold foils and the subsequent measurement of the induced activity. The activity is directly proportional to the fluence but also depends on the neutron spectrum.