kkm was the only swiss nuclear power plant that did not have an unlimited operating license. due to the problems noticed during the commissioning and to some ongoing tests on the emergency cooling systems performed in the united states, until 1980 it received a series of six-month license extensions, then increased to one year. they were followed by a five-year, a seven-year, and a ten-year license extension. these extensions were justified by technical improvements the operator was instructed to perform. the operating license was extended again in 1998 and was due to expire on 31 december 2012; however, an unlimited license was granted on 21 december 2009.