Transfer fallout/milk

If vg is taken as 3 mm s-1, then a dosage of 1 Bqs m-3 of 131I in air gives 3 x 10-3 Bq m-2 fallout. The ratio of thyroid doses from milk compared with inhalation are then as shown in Table 3.9. The calculated ratio of 20 for adults compares with an increase of about 10 in the thyroid activity of Leeds residents attributed to consumption of milk in the days after the passage of the plume of activity from the Windscale accident (Fig. 3.7). The transfer factor fallout/milk in the Leeds area was lower than that assumed in the calculations leading to Table 3.8... 

If there is fallout from nuclear weapons tests, or from reactor accidents, milk is likely to be the predominant source of 90Sr in diet, and an important source of 137Cs. A few days will intervene between an episode of fallout and the peak concentration in milk, giving time for preventative measures. It is therefore important to know the transfer factors, so that the future levels in milk can be predicted from the amount of fallout. The transfer depends on the retention of the fallout on the foliage, the amount of herbage eaten by the cattle, and the fraction of the cow s daily intake secreted per litre of milk. The transfer factor feed/milk is defined... 

Table 2.19. Transfer coefficients from fallout to milk following foliar uptake...

Transfer coefficients can also be deduced from statistics of the levels of 90Sr and 137Cs in milk measured during monitoring of the fallout from nuclear weapon tests. This has the advantage over experimental work of taking into account variations in agricultural practices, but introduces complications such as the use of root crops and imported feed for cattle and the uptake by crops from the soil of activity deposited in previous years. UNSCEAR (1977) analysed data from a number of countries, obtained in the years 1958-74, in the form,... 

Fig. 2.11. Transfer of Cs and Sr from fallout to milk. Experimental results of Van den Hoek et al. (1960). Lines are as calculated by Linsley et al. (1986).

Table 2.20. Parameters of transfer function of 90Sr from fallout to milk (m2d r1) (UNSCEAR, 1977)...

Ward, G.M., Keszthelyi, B., Kangar, B., Kralovansky, V.P. Johnson, J.E. (1989). Transfer of 137Cs to milk and meat in Hungary from Chernobyl fallout. Health Physics, 57, 587-92. 

Table 3.7 shows the dose to the thyroid from inhaling 131I and Table 3.8 shows the dose from 131I in milk (Kendall etal., 1987 Linsley et al., 1986). As usual in hazard evaluation, the calculations are conservative, the assumed intakes and transfers being towards the upper end of the range of possible values. In Table 3.8, the infant thyroid dose per Bq m-2 of 131I fallout is derived as follows. The... 

In Cumbria, after the Windscale accident, a ban on the sale of local milk was made effective within 3 d. If vg for1311 in the area of maximum fallout downwind of Windscale was 3 mm s-1, then the measured deposition of 1 x 106 Bq m-2 corresponds to an air dosage of 3 x 10s Bqs m-3. From Table 3.7, this would give a theoretical thyroid dose to a child of 40 mSv which corresponds to the lower end of the range given in the first row of Table 3.10. If there had been no ban, and if the transfer from fallout to milk had followed the theoretical curve A in Fig. 3.6, then from Table 3.8 a child drinking 0.92 1 of milk per day would have received a thyroid dose of 1.4 Sv. 

Knapp also sought to deduce the maximum concentration C/(max) of 131I in milk resulting from the fallout, using records of tests in the 1960s where gamma dose and C/ were both measured, Garner s (1960) data on transfer from cattle feed to milk, and Booker s (1958) measurements after the Windscale accident. 

Hardy EP, Rivera J. 1968. Transfer of fallout strontium-90 to cows milk. J Dairy Sci 51(8) 1210-1214. 

It then seemed that the major problem would be the fallout of radioactive iodine onto grass, which would then be eaten by cattle, and make its way to the cows milk. Iodine collects in the thyroid gland, and so if there were radioactive iodine contamination in the milk, it would be transferred to the human thyroid when the... 

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