Aktivnosti radiocezija u pšenici u Hrvatskoj

Results of systematic, long-term measurements of 137Cs activities in wheat are summarized. 137Cs fallout activity affected wheat activity the coefficient of correlation being 0.91. A model used by UNSCEAR was used to describe l37Cs transfer from fallout deposition to wheat. The transfer coefficient was calculated to be 6.1 x 10-3 Bq yr kg-1/(Bq m-2). The dose incuned by wheat consumption was estimated for the Croatian population, the annual collective equivalent dose being approximately 550 man Sv for the 1965-1992 period. After the Chernobyl nuclear accident the 134Cs: 137Cs activity ratio in wheat was - 0.5, and did not differ from that for other environmental samples.Prikazani su rezultati dugogodišnjih sustavnih mjerenja aktivnosti 137Cs u pšenici. Aktvnost 137Cs u radioaktivnim oborinama utječe na aktivnost pšenice, uz koeficijent korelacije 0,91. Transfer 137Cs od radioaktivnih oborina do pšenice najbolje opisuje model UNSCEAR-a. Transferni koeficijent procijenjen je na 6.1 x 10-3 Bq god kg-1/(Bq m-2). Kolektivna ekvivalentna doza uslijed konzumacije pšenice za hrvatsku populaciju procijenjena je na oko 550 čovjek Sv za period od 1965. do 1992. godine. Poslije nuklearne nesreće u Černobilju omjer aktivnosti 134Cs:137Cs u pšenici bio je - 0,5 i nije se razlikovao od vrijednosti omjera u ostalim uzorcima iz okoliša

Radioactivity in Biosphere and Occupational Exposure in Croatia

U radu su prikazani rezultati sustavnog istraživanja radioaktivnosti životne i radne sredine u Republici Hrvatskoj od početka šezdesetih godina. Istraživana je radioaktivnost zraka, oborina, tla, rijeka, mora i jezera, pitke vode te ljudske i stočne hrane, kao i vanjska izloženost za radnike profesionalno izložene ionizirajućem zračenju. Maksimalna radioaktivna kontaminacija fisijskim radionuklidima zabilježena je ranih šezdesetih godina, u vrijeme najintenzivnijih atmosferskih nuklearnih pokusa. Od tada radioaktivnost radioaktivnih oborina eksponencijalno opada. Nuklearna nesreća u Čornobilju dovela je u Republici Hrvatskoj do ponovnog povećanja radioaktivnosti 137Cs u okolišu, dok je povećanje radioaktivnosti 90Sr, zbog njegove manje hlapljivosti, bilo neznatno. No, nakon tog kratkotrajnog povećanja ponovno je došlo do eksponencijalnog pada radioaktivnosti, tako da je godine 1998. prosječna brzina apsorbirane doze u zraku iznosila 0,128±0,004 μGy/h. Prosječan pripadnik hrvatske populacije je stoga zbog izloženosti osnovnom zračenju na godišnjoj razini primio dozu od oko 1,12±0,04 mSv. Ukupna kolektivna doza uključuje i dozu uzrokovanu primjenom izvora ionizirajućih zračenja u medicini te je značajan naglasak stavljen na kontrolu kakvoće izvora zračenja (koja se sustavno provodi od 1985) kako bi se smanjila ukupna kolektivna doza koju primi hrvatsko pučanstvo.This paper presents results of long-term investigations of radioactivity in general and occupational environments in the Republic of Croatia. Investigations of environmental radioactivity and occupational exposure monitoring in Croatia have been systematic since the early sixties. Investigations included radioactivity of the air, fallout, soil, river, sea and lake water, tap water, human foodstuffs, and animal feed. External dosimetry monitoring is carried out for workers occupationally exposed to ionising radiation in medicine, and industry. Radioactive contamination with fission radionuclides is associated with deposition of fallout originating from atmospheric explosions of nuclear weapons as well as from regular operation of nuclear facilities. Among hundreds of different radionuclides contained in various types of fallout only a few significantly contribute to the dose, particularly 90Sr and 137Cs. The maximum radioactive contamination with fission radionuclides was recorded in the early sixties, at the time of most intensive atmospheric nuclear tests. The fallout radioactivity has been exponentially decreasing ever since. The nuclear accident at Chornobyl temporarily raised 137Cs radioactivity levels in Croatia, whereas the increase in 90Sr radioactivity was not significant due to its low volatility. After a short-term increase, radioactivity dropped back to the pre-Chornobyl levels. Apart from radioactivity of fission products, investigations involved natural radioactivity and technologically enhanced natural radioactivity. Particular attention has been paid to radon as the most relevant source of natural radiation for humans. In 1998, the average absorbed dose in the air was 0.128±0.004 μGy/h. Consequently, an average Croat received the annual dose of 1.12±0.04 mSv through exposure to background radiation. However, as the overall collective dose includes the dose received by medical and civil use of radiation sources, significant effort has been put on the quality control of radiation sources (systematically implemented since 1985) as an important step for reducing the overall collective dose of Croatian population