Transfer of radioiodine to milk

The transfer factor Fm from feed to milk is defined in equation (2.11) as the activity per litre expressed as a fraction of the activity ingested daily by the cow. Numerous measurements of Fm have been made by dosing cows with iodine isotopes or by comparing radioactive or stable iodine in milk and in the herbage eaten by the cows. Table 3.6 shows a selection of the results. Fm depends on the yield of milk and on seasonal factors (Gamer, 1971), but it does not appear to depend on the chemical form of the iodine (Bretthauer et al., 1972). Gamer (1971) recommended Fm = 5 x 10 3 d l-1 for UK conditions, but noted that US results tended towards a higher value. 

If there is fallout from an accidental emission of fission products, the activity on the ground can be measured quickly by gamma spec- 

From day 6 onwards, the slope of the curve corresponds to the effective half-life of 131I on herbage, namely 5 d. Assuming that this continues indefinitely, the area under curve A in Fig. 3.6 is 1.4 m2 d l-1. This is equivalent to the transfer factor km, defined by equation (2.12). Values of Fm for 131I and 137Cs are about the same, but the radioactive decay of 131I reduces km compared with that for137Cs (Table 2.19). Also shown in Fig. 3.6 are values of C/ as deduced from measurements near 

Analysis of feeding experiments UK conditions US conditions 5 x 10 3 1 x 10 2 Garner (1971) Garner (1971) 

Measurement of 131I from Chernobyl 1 x 10-3 Dreicer Klusek (1988) 

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