"We were at less than zero (per cent) late Wednesday night and early Thursday morning," utility spokesperson Kathleen Duguay stated in an email to CBC News.
"We have been evaluating the benefit of going to zero since early last week."
NB Power says it continues to have problems with the chemistry of the water in Lepreau's non-nuclear boilers, an issue that caused the reactor to be turned off once already in December.
Duguay says that, in combination with ongoing problems refuelling the reactor, led to a decision to power Lepreau down almost completely to allow both issues to be tackled at once.
She said it won't be known until next week when the reactor will be able to be powered back up.
Refuelling will resume when the reactor is back online.
Lepreau has operated at less than full capacity since coming back online last November, following a four-and-a-half year refurbishment."