The sudden departure last week of long-serving managing director Graham Olrich from Credit Union Australia, has left a space at the top of Australia's biggest credit union.Deputy to Olrich, Rob Nicholls, has assumed the role as acting chief executive officer in the interim, but the internal plan was not for Nicholls to ultimately succeed Olrich."The board hasn't decided what they are going to do yet, but they have two options -  advertise to recruit, or put me in the chair for a while and work through succession," said Nicholls."I am happy to act for as long as the board would require."Nicholls said after the merger with Australian National three years ago, when he became deputy to Olrich, the CUA internal strategy was for Nicholls to help Olrich with succession planning internally."The plan was then I would probably move on in about a year from now, which would create the space for the succession (for Olrich)."That has suddenly changed, so we are in a position now where I can stand in immediately and act, while the board considers the actions."Nicholls confirmed he will apply for the vacant role of chief executive officer.