[en] Reactor pressure vessel head retensioning is on the critical path during outages, so when an unexpected outage occurred before planned tensioner system maintenance had been done at Niagara Mohawk Power Corporation's Nine Mile BWR Station I, the tool manufacturer was asked to send a service specialist to oversee the entire detensioning and retensioning sequence. The supervisor sent was able to deal with several minor problems as they occurred, ensuring that the entire procedure went smoothly and within schedule. (author)