The purpose of this project is to investigate the performance of the NRC WAFAC and commission it as a primary standard. Significant enhancements were implemented to improve signal to noise ratio, measurement reproducibility and to eliminate electric field distortion. Validation of the ionization chamber was then carried out with a low-energy X-ray beam (31 keV) where the air kerma rate had been previously established using the existing NRC primary standard free-air chamber. Agreement between the two devices was obtained within the combined measurement uncertainties of less than 0.5 %. Measurements were also made with a 125I LDR seed and these gave results that were consistent at the 1 % level with the manufacturer's stated seed activity (traceable to NIST).
The overall standard uncertainty in the determination of air kerma strength using the NRC WAFAC is estimated to be 3 %, which reaches the target uncertainty for the standard.