Radioecological monitoring of the area surrounding the Leningrad NPP: results evaluation

The paper presents results of long-term monitoring of radioecological situation in the area surrounding the Leningrad NPP (LNPP), that covers the periods before the Chernobyl accident (1980-1985), during and immediately after the accident (1986-1992) and the late period (2013-2014). After the Chernobyl accident the enhanced radioactivity level in the environment including soil and vegetation was registered in the area surrounded the Leningrad NPP. Several test points for sampling were selected inside the 30-km zone around the LNPP. Before the accident, in 1985, 137Cs soil contamination density was 3 kBq/m2; immediately after the accident, in 1986, the contamination density increased by 10 fold. In the late period, in 2013, the 137Cs soil contamination density reduced significantly, however it exceeded the levels registered in 1985 by 2.6-7.3 times. 90Sr soil contamination density was 1.4-1.6 kBq/m2 both before and after the accident (1985-1992). The presence of artificial radionuclides in agricultural produce before 1985 was caused by global radioactive fall-outs, however no radionuclides emissions from the Leningrad NPP were registered. Average 137Cs content in grain and intertilled crops exceeded their content before 1986 by 19-44 times; the high content was associated with the contamination of the vegetation by airway. The 137Cs content in agricultural produce is still higher than the level registered before the Chernobyl accident by 1.4-2.1 times, but the current levels are many times less than the current acceptable level. The levels exceeding the acceptable magnitude are found in wild berries only, that grow in some swampland with 137Cs soil contamination density of 3-9 kBq/m2 near the LNPP. Dynamics of transfer factors of 90Sr and 137Cs from soil to agricultural produce in the LNPP area was evaluated. The soil properties and the Chernobyl fall-out are shown to affect the factor magnitude. Presented data demonstrate that the Leningrad NPP operating in the standard way does not influence strongly on radiological situation in the 30-km zone around the NPP.