The Swedish Radiation Safety Authority called on the Forsmark nuclear plant, near Uppsala, north of Stockholm, “to investigate… which measures would eventually be needed to strengthen physical protection” of the plant.

It noted in a statement that the trespassing by activists — who got over the plant’s fence using a fire truck’s ladder — “did not have any consequences from a radiation safety perspective.”

However it added, “the event shows a need for permit holders to nuclear installations to carry out additional analysis of the possibility for, and consequences of, trespassing into secure areas.”

Around 50 activists were arrested on June 14th for taking part in Greenpeace’s action at Forsmark. Some were later released and 29 were fined by an Uppsala court on Thursday.

In their protest, the activists, who dressed up as renewable energy sources such as wind, water and sun, demanded Swedish parliamentarians reject a government proposal on replacing Sweden’s 10 existing nuclear reactors at the end of their lifespans.

Three days later, on June 17th, the parliament approved the proposal.