To ensure that those items included in the mainte­nance schedule have a thorough overhaul and are done in a consistent way at each prescribed interval, maintenance instructions for the craftsmen are pre­pared. These will detail the stages of work required during its overhaul to ensure that all items of main­tenance are covered. The maintenance instruction will carry a Quality Assurance procedure that records the checks to be carried out at each stage of the work. ~ The maintenance instructions may be vetted by the Nuclear Installations Inspectorate to satisfy them that the work is of an adequate nature. All the work car­ried out under the maintenance schedule has to be fully recorded and submitted to the Nil by the end of each biennial overhaul.