Comparisons (Archive): International Inter-Comparison Exercise (IICE) for Natural CRMs development

Summary

Certified Reference Materials (CRMs) are needed to develop and validate method analysis, and also for quality monitoring of established radioanalytical processes. International efforts of experienced laboratories often contribute their expertise to CRM research and production. Radioactive CRMs are used to support the quality of radioactivity content determinations in different materials.

Description

After the Fukushima accident in March 2011, a considerable amount of radioactive contamination was discharged into the environment. As a consequence, the food had to be screened and analyzed for radionuclides, and corresponding CRMs for specific foods were needed. The Japan Society for Analytical Chemistry (JSAC), the National Metrological Institute of Japan (NMIJ), and the National Food Research Institute (NFRI) organized International Inter-Comparison Exercises to develop a series of environmental CRMs for radioactivity analysis in food. The prepared CRMs were certified based on the results of Japanese and international laboratories. 

The objective of the IICEs is to confirm reliability of the radioactivity concentrations of Cs-134, Cs-137, K-40 and Sr-90 in the candidate CRMs. Cs-134, Cs-137, and Sr-90 are the major radionuclides of interest in contaminated terrestrial materials after a nuclear accident. The NIST Radioactivity Group participated in the IICE certification process for Brown Rice, Fish Meat, and Fish Bone Ash CRMs. We pursued two approaches for the gamma analysis: non-destructive (measurement of the material as it was received) and destructive (measurement of dissolved material). Both methods were in good agreement, and the reported results were a combination of the two values. 

Table 1. NIST Results for Radioactivity content in the Brown Rice CRM

Radionuclide	NIST value (Bq/kg)		CRM (Japanese) value (Bq/kg)
	Non-destructive	Destructive
Cs-134	141 ± 9	141 ± 7	141 ± 9
Cs-137	207 ± 9	208 ± 7	210 ± 13
K-40	75 ± 9		75 ± 7

 

 Table 2. NIST Results for Radioactivity content in the Fish Meat (FM) and Fish Bone Ash (FB) CRMs

CRM	Massic Activity (Bq/kg)
	Cs-134	Cs-134 2u	Cs-137	Cs-137 2u	Sr-90	Sr-90 2u	K-40	K-40 2u
FM	64.7	7.9	194.1	24			345	50
FB	147.6	7.8	444.0	27	11.6	0.4	737	145

 

Preliminary Results reported to the Japan Institute of International Affairs (JIIA) by the IICE’s Laboratories

 

 

 

 

 

 

 

Notice of Online Archive: This project has ended and thus this page is no longer being updated and remains online for informational and historical purposes only. The information is accurate as of February 2021.