As a starting point consult the Nunavut Consolidation of Boilers and Pressure Vessels Regulations R-006-93 for useful information on pressure equipment exemptions and requirements of Nunavut. Always consult the chief inspector of a jurisdiction. The act is found here. The Gazette publishes changes to the regulations.
Nunavut Canadian Registration Numbers for fitting registrations are issued by ACI Central who is the designated regulatory authority for seven provinces and territories that include: Newfoundland, Nunavut, Prince Edward Island, New Brunswick, Nova Scotia, North West Territories, Yukon. This small agency located on Prince Edward Island vastly simplifies what could be a terribly long and bureaucratic process of dealing with seven entities.
For boilers, pressure vessels and piping system registration applications you may also contact the Nunavut government, Community and Government Services, Boiler Safety division, Public Works and Services for more information.