ARTIFIC1AL RADIONUCLIDES IN WATERS OF THE LOWER SECTION OF THE RIVER EBRO (NORTHEAST SPAIN)

摘要

The river Ebro, in Northeast Spain, discharges into the Mediterranean Sea after flowing through several large cities and agricultural, mining and industrial areas. The Asco nuclear power plant (NPP) is located in the lower river section and comprises two pressurised--water reactor (PWR) units, from which low-level liquid radioactive waste is released to river waters under authority control, During the period 1989 to 1993, we carried out 29 sampling campaigns in order to determine ~3H, ~90Sr, ~l34Cs, ~137Cs, ~238Pu and ~239'240Pu in Ebro river waters at different locations, both upstream and downstream from the Asco NPP ~3H, ~l34C, and ~l37C, activities showed large variability as they ranged from < l.4 to l17±3 Bq L~-l, <0.27 to 22±l mBq L~-1 and <0.36 to 35±ll mBq L~-l, respectively. This behaviour, especially remarkable for tritium, was due to the detection of tank releases travelling downstream. The characteristic NPP ~l34C,/~137Cs ratio was found to be 0.6l±10.02 (N = 22). In the estuarine area, ~l37Cs traces from Mediterranean waters were observed and relatively enhanced tritium activities might possibly be present due to the accumulation of activity in the estuary.~ 90Sr and ~239,240Pu activities were homogeneous both in respect to time and space, showing mean activities 6.9±0.2 mBq L~-l (N = l0) and l .36±0.l0 mBq m~-3 (N = 3), respectively. These levels could only be attributed to nuclear weapons fallout leached by continental waters, as the impact from the plant appears to be negligible and no other sources are present in the area.