▁average ▁of ▁ 9 3 . 1 1 % ▁and ▁generated ▁over ▁ 5 , 0 0 0 ▁G Wh / year ▁of ▁energy ▁on ▁a ▁sust ained ▁basis ▁for ▁its ▁first ▁de cade ▁of ▁operations . ▁However , ▁numerous ▁problems ▁started ▁to ▁surface ▁in ▁the ▁mid ▁to ▁late ▁ 1 9 9 0 s , ▁due ▁to ▁poor ▁maintenance ▁and ▁low ▁invest ment . ▁In ▁mid - J anu ary ▁ 1 9 9 7 , ▁a ▁leak ▁near ▁the ▁re actor ▁core ▁forced ▁a ▁third ▁shut down ▁in ▁ 2 ▁years . ▁The ▁ 7 5 - day ▁sto pp age ▁was ▁caused ▁by ▁a ▁crack ed ▁fe eder ▁pipe . ▁The ▁human ▁error ▁cost ▁C $ 4 0 ▁million ▁in ▁rep airs ▁and ▁C $ 4 5 0 , 0 0 0 / day ▁to ▁purchase ▁replacement ▁power ▁from ▁Quebec . ▁ ▁Inc idents ▁ ▁In ▁ 1 9 9 0 , ▁assistant ▁plant ▁operator ▁Daniel ▁George ▁M ast on ▁was ▁charged ▁after ▁he ▁took ▁a ▁sample ▁of ▁heavy ▁water , ▁cont amin ated ▁with ▁tr it ium , ▁a ▁radio active ▁is ot ope ▁of ▁hydro gen , ▁from ▁the ▁moder ator ▁system ▁and ▁loaded ▁it ▁into ▁a ▁c af eter ia ▁drink ▁disp enser . ▁E ight ▁employees ▁d rank ▁some ▁of ▁the ▁cont amin ated ▁water . ▁One ▁individual ▁who ▁was ▁engaged ▁in ▁heat ▁stress ▁work , ▁requiring ▁altern ating ▁work , ▁rest , ▁and ▁re - h yd r ation ▁periods ▁consum ed ▁significantly ▁more ▁than