Environmental Radiological Surveillance at
Nuclear Power Plants

A well-equipped Environment Survey Laboratory (ESL) is established at each nuclear power plant site by BARC well before the commissioning of the plant. The primary aim of the environmental monitoring programme is to demonstrate compliance with the radiation exposure limits set for members of public. In pre-operational phase, ESLs generate baseline data on the levels of external radiation dose and concentration of natural radioactivity (Uranium & Thorium and their daughter products, Potasium-40 etc.) and radionuclides due to global weapon fallout (Strontium-90, Cesium-137 etc.). This requires a detailed measurement of these radionuclides in different environmental matrices (air, water, fish, silt, sediment, soil, vegetation, goat thyroid, vegetable, milk, grass, crops, fruits, meat and other dietary items) covering 30 km radial distance around the plant. The number and type of samples and sampling frequency is optimised for each site on the basis of the nature of operating facilities, utilization of local natural resources, existence of population clusters and related demographic data.

Mainly three types of environmental samples are collected and analyzed. The first category of samples are directly relevant to the estimation of dose received by the members of public like drinking water, air and locally produced dietary items consumed by the public. The second category are trend indicators for build up of radionuclides, if any, such as weeds, sediment, soil, grass etc. The third category includes sensitive indicator organisms that accumulate specific radionuclides to a great extent and these serve as very sensitive detectors or markers. For example goat thyroid for the detection of low levels of fresh radioactive fallout of Iodine-31.

In the operational phase, the ESL continuously monitors the external radiation exposure levels in the environment, measures meteorological parameters and analyzes the distribution and concentration of reactor related radionuclides in samples of different environmental matrices to assess the contribution, if any, from the plant releases.

In general, even after thirty years of operation of nuclear power plants, the levels of radionuclides in terrestrial samples such as soil, crop, vegetation, milk, meat, egg etc. are at global weapon fallout levels and there is no significant contribution from plant operations. In aquatic samples such as water, fish and sediments in the vicinity of discharge area show a small increase in the levels of Hydrogen-3 and Cesium -137, but the levels are insignificant from health point of view.

Experience of extensive environmental monitoring has shown that even a hypothetical individual staying at plant exclusion boundary (1.6 km) will receive only about 8% of dose limits (1 mSv/y) prescribed for members of public, in case of Tarapur Atomic Power Station, Rajasthan Atomic Power Station and Madras Atomic Power Station, and less than 1% in case of Narora Atomic Power Station, Kakrapar Atomic Power Station, Kaiga Generating Station, and RAPS-3 & 4 due to improved design features. At distances greater than 1.6 km, the doses to the members of public continuously get reduced and are insignificant compared to doses received from natural sources.