"FAC is the commencement of the controlled nuclear fission process for the first time and is a step towards the subsequent beginning of power production in a nuclear reactor," AERB Secretary Bhattacharya said in a statement.
"Several number of low power tests will be carried out in order to verify the conformance of reactor characteristics to the design objectives before granting clearance for the next commissioning stage which is the phase-wise increase in reactor power level," it said.
AERB had earlier granted the final permission for'Initial Fuel Loading'(IFL) for unit-1 in September last year.
Reviews were carried out by the specialist groups and the Advisory Committee for Project Safety Review of AERB at the facility in Kudankulam.
Following the clearance, some internal formalities were to be done at the KNPP and power production was likely in a month-and-a-half, a senior KNPP official said.