By Benjamin Mallet PARIS (Reuters) -French utility EDF discovered a radioactive leak last Wednesday in the primary cooling circuit of its Civaux nuclear plant in southwestern France, the company said, adding there was no safety risk and no radioactivity was measured outside the plant. The leak could delay the reactor’s planned Jan. 8 restart, an industry source familiar with the situation told Reuters on Monday. “It is too soon to establish what impact this hazard will have on the duration of the reactor’s standstill,” EDF said, adding it was premature to suggest this would delay the reactor’s…