Traces of Radioactive I-131 in Rain Water and Milk Samples in Romania

Measurements of I-131 (T1/2 = 8.04 days) have been performed in IFIN-HH's underground laboratory situated in Unirea salt mine from Slanic-Prahova, Romania. The rain water samples were collected in March 27th in Brasov and in March 27th, 29th and April 2nd in Slanic. Also sheep milk was collected in Slanic area and subsequently measured. The samples were measured in the IFIN-HH's underground laboratory in ultra-low radiation background, using a high resolution gamma-ray spectrometer equipped with a GeHP detector having a FWHM = 1.80 keV at 1332.48 keV at the second Co-60 gamma-ray, and a relative efficiency of 22.8%. The results show a specific activity of I-131 from 0.17 to 0.87 Bq/dm^3. In the sheep milk from Slanic area the specific activity of I-131 was about 6 Bq/dm^3


Introduction
The Fukushima accident started on March 11 th , 2011 causes the release of significant amounts of 131 I, 171 Cs and other radioactive isotopes in the environment. The atmospheric currents spread the radioactive contamination all over northern hemisphere. According with meteorological information the radioactive cloud has reached the Romanian territory beginning with March 25-26, [1, 2]. The meteorological conditions over Romania were characterised by small rains. Six sample, five of rain water and one of sheep milk, were taken for analyse.  -equivalent depth from cosmic ray muon measurements: 610 mwe (meter water equivalent), [4].

Measurements and results
The measurements were performed with a CANBERRA ultralow GeHP system, equipped with a detector having a relative efficiency of 22.8 %, assisted by an INSPECTOR 2000 multichannel analyser and GENIE 2000 software code. The detector is housed in a 10 cm Lead and 2 cm Copper shield, which assures a reduction of the background of 1600 times with respect to the spectrum collected outdoor at surface, see Fig. 2. The efficiency of the measurement system was determined with IAEA-444 reference material which is a soil from China containing a cocktail of 109 Cd, 60 Co, 137 Cs, 54 Mn and 65 Zn radionuclides. The energy dependence of efficiency is represented in log-log graph in Fig. 3.   Fig. 3 Efficiency versus energy for the spectrometric system equipped with an ultra-low GeHP detector with 22.8 % relative efficiency Samples of rain water were collected beginning with March 27 and were measured in cylindrical plastic box of 75 mm diameter and 35 mm high. The volume of measured samples was 80 cm3. The 131 I line at 364.48 keV has been seen in all collected spectra. This aspect is illustrated for rain water sample collected in the morning of March 29 th in Slanic in Fig. 4. The specific activities of 131 I in the rain water samples are presented in Tab. 1. In April 5th a sheep milk sample has been collected and subsequently measured in the same way as rain water samples. The specific activity of 131 I measured in sheep milk is 5.2 ± 0.5 Bq/dm 3 .

Comments
From the results, one can observe the presence of 131 I in very small amounts in the precipitation and milk recorded beginning with 27 March 2011 in Brasov and Slanic Prahova, Romania. The specific activity in rain water of 131 I varies from 0,15 Bq/m 2 to 0,75 Bq/m 2 .
For the moment, no other data have been available for analyses, but even so we can suppose that the 131 I originates from Fukushima nuclear accident. For this reason, the environmental radioactivity, especially in rain water and milk, is monitored continuously in order to assess the level of radioactive deposition.
The measured activities are far bellow any intervention limits. For instance in Japan the limit for drinking water was set at 300 Bq/dm 3 for adults and children and 100 Bq/dm 3 for infants [6]. The values measured by us are 2 to 3 order or magnitude lower than these limits. In sheep milk the 131 I concentration is more than an order of magnitude lower than the limits.
The presence of 131 I over Romania demonstrates that the consequences of a nuclear accident could be put in to evidence even at more than 10,000 km away which also demonstrates that at this moment the radioactive plume originating in Fukushima is spread practically all over the Northern Hemisphere.