Title: International harmonized protocol for standard preparation,
irradiation and measurement for assuring metrological traceable results
in neutron activation analysis
Chairman: Peter Bode
Members: · E.A. De Nadai Fernandes, R.M. Lindstrom, J.
Kucera, B. Smodi, T. Weizhi, and A.Fajgelj
The single comparator calibration approach (the 'k0-method')
in neutron activation analysis is subject to various influencing factors,
which might vary from laboratory to laboratory. A critical review and
harmonization of measurement approaches is required to assure the highest
achievable metrological comparability of results obtained.
This project aims at the development of a guidance document (protocol)
for practitioners of neutron activation analysis related to calibration
of the neutron fluence rate, -spectrum shapes, and full energy photo
Instrumental neutron activation analysis (INAA) allows for multi-element
determinations without chemical pre-treatment of the test portion. The
INAA multi-elements capabilities are fully employed if the single comparator
calibration is used, also known as the 'k0-method'.
In contrast to the use of reference material for calibration, the k0-method
requires very critical calibration of input quantities, including the
thermal, epithermal and fast neutron fluence rate and gradients thereof
in the irradiation position, as well as of the full-energy photopeak
efficiency and the coincidence counting effects.
Each of these individual calibrations implies contribution to the uncertainty
of measurement, and combination thereof is not always straightforward
and may have to be assessed via Monte Carlo calculations.
The aim of this project is to provide practical guidance on
- preparation of standards for calibration the neutron spectrum characteristics
- assessment of correction factors for neutron self-shielding, gamma-ray
self attenuation and dimensional differences during irradiation and
- determination of the full-energy photopeak efficiency
- assessment of correction factors for coincidence effects during
- asssessment of the contributions of each individual calibration
step to the uncertainty of measurement
- elaboration on the traceability of the results thus obtained.
The protocol will account for differences that exist in sample packaging
in various laboratories, as well as in irradiation containers and facilities,
and in counting facilities. Where applicable, examples of EXCEL spreadsheet
calculations will be included.
Each of the task group members will use its own network of k0-method
practioners for consultation and information on e.g. side-specific irradiation
and measurement conditions. This will contribute to the development
of guidance and protocols for application of the k0-method
of standardization in a broad variety of NAA facilities.
Last Update: 11 October 2007
<project announcement to be published
in Chem. Int.>