On the Revision of Control Index Levels on the Ingestion of Food and Water in the Guidelines for Radiological Emergency Preparedness and Countermeasures in Japan.

Food safety regulations: what we learned from the Fukushima nuclear accident

“…Finally, RCIL jk is the RCIL of indicator radionuclide(s) for age group j and food category k. To yield the index value, the calculated RCIL value minimal among infants, children and adults for each food category was rounded off to a smaller value on the safe side (Suga and Ichikawa, 2000). Further details of approaches taken to calculate the index values for radioiodines and radiocesiums are provided below, for which parameters used are listed in Tables 4 and 5.…”

“…Variable T (d) is a period of time for food intake per annum (T ¼ 365). Factor W jk (kg/d or L/d) is the mean daily food intake (MDFI) for age group j and food category k. Values of MDFI for adults originate from the data in the National Nutrition Survey conducted in 1986 (MHW, 1988), and those for infants and children were adapted from the data obtained by the National Institute of Radiological Sciences (Chiba, Japan) (Suga and Ichikawa, 2000). MDFI of milk and drinking water consumed by infants includes the mass of breast milk, cow's milk, powdered milk, and water used to dissolve the milk powder.…”

“…CF for a committed effective dose is the sum of that for committed tissue or organ equivalent doses each multiplied by tissue weighting factors. Whereas the International Commission on Radiological Protection (ICRP) has provided age-specific CF values each for six age groups (ICRP, 1992b), only three groups (infants, children and adults) were dealt to calculate RCIL (Suga and Ichikawa, 2000). CF values were taken from those listed in ICRP Publication 67 (ICRP, 1992b) and…”

“…f i values for coexisting radionuclides were calculated as the ratio of each simulated radioactive concentration inside the reactor at 0.5 d after shutdown of the pressurized water reactor (PWR) where fuel having an initial concentration of 3% is burned at 30 GWd/ton. ORIGEN2 code (Croff, 1980) was used to simulate concentrations of each radionuclide, and a time point of 0.5 d was chosen to exclude short-lived radionuclides that are unlikely to contaminate food (Suga and Ichikawa, 2000).…”

“…Herein, IL is expressed in the committed dose per annum (mSv/y), and the index values expressed in radioactive concentrations (Bq/kg) fall under DIL. To determine the index values, the radioactive concentration giving IL (RCIL) was calculated for each radionuclide group using equation (5) (Suga and Ichikawa, 2000).…”