On Friday the Finnish parliament by a 115-74 vote approved the building of the Russian owned Fennovoima plant in the town of Pyhäjoki, 150 kilometres from the Swedish coast.
The Swedish network Nuclear Free Gulf of Bothnia submitted 20,000 signatures earlier this week to Finnish lawmakers opposing the decision, saying they are worried about possible nuclear accidents and the environmental impact.
"It feels really horrible and wholly unacceptable," said no campaigner Lena Lagerstam to Swedish Radio.
Another member of the group, Elisabeth Holmström, told Swedish Radio News that "we are very determined because we can not just accept they will build a Russian reactor on the beach of the Gulf of Bothnia."
The pair added that the fight would go on to gather more names to the no petition.