▁ 2 0 0 6 , ▁elev ated ▁levels ▁of ▁lead ▁were ▁detected ▁ab o ard ▁the ▁sub marine ; ▁they ▁were ▁believed ▁to ▁come ▁from ▁the ▁lead - br ick ▁ball ast ▁blocks ▁used ▁ab o ard ▁Cor ner ▁Brook . ▁Between ▁October ▁ 2 0 0 6 ▁and ▁January ▁ 2 0 0 8 , ▁Cor ner ▁Brook ▁was ▁active ▁for ▁only ▁ 8 1 ▁days . ▁The ▁sub marine ▁participated ▁in ▁NAT O ▁exercise ▁' No ble ▁Mar iner ' ▁during ▁May ▁ 2 0 0 7 . ▁During ▁the ▁exercise , ▁which ▁occurred ▁in ▁the ▁Balt ic ▁region , ▁Cor ner ▁Brook ▁successfully ▁closed ▁with ▁the ▁aircraft ▁car rier ▁ ▁without ▁being ▁detected . ▁The ▁sub marine ▁returned ▁to ▁Canada , ▁and ▁in ▁August , ▁she ▁participated ▁in ▁Operation ▁N ano ok , ▁a ▁so vere ig nt y ▁exercise ▁held ▁in ▁and ▁around ▁I q al uit ▁and ▁the ▁B aff in ▁Island ▁coast al ▁and ▁Hudson ▁Stra it ▁areas . ▁That ▁year , ▁Cor ner ▁Brook ▁participated ▁in ▁the ▁NAT O ▁exercise ▁" No ble ▁War rior ", ▁mark ing ▁the ▁first ▁time ▁in ▁ 1 5 ▁years ▁that ▁a ▁Canadian ▁sub marine ▁had ▁been ▁present ▁in ▁European ▁waters . ▁ ▁In ▁February ▁ 2 0 0 8 , ▁Cor ner ▁Brook ▁depart ed ▁from ▁Hal if ax ▁during ▁a ▁snow st orm ▁for ▁a ▁three - month ▁deployment ▁to ▁the ▁Car ib bean ▁Sea . ▁As ▁part ▁of ▁the ▁deployment , ▁the ▁sub marine ▁operated ▁with