EXO--200 Muon Veto System

EXO200 is searching for neutrinoless double beta decay of $^{136}$Xe. This is process has not been observed and only occurs if the neutrino has a Majorana mass. If $^{136}$Xe decays via neutrinoless double beta decay it has a half life of $<$10$^{23}$yr. For such a low rate backgrounds need to be kept to a minimum. One source of backgrounds is cosmic-ray muons. Muons need to be vetoed with a efficiency of $>$90\% for EXO--200 to achieve it's desired sensitivity. I will to talk about the commissioning of the veto system and it's performance as part of the EXO--200 cosmic ray veto.