The second fundamental principle which has remained in the rules since outset is the Safety Document sys­tem. The rules state that the forms used for Safety Documents in controlled areas of nuclear licensed sites, shall contain a Radiological Control Document which specifies the radiological precautions which are required.

Under normal operations the dose rates and con­tamination levels of an area will be relatively constant and thus will be zoned as appropriate. There is no need to specify additional precautions to those already in existence in the area. However, if maintenance is carried out on a plant item in the area, then the work itself may significantly increase the hazards and thus it is necessary to specify the radiological precautions necessary on the radiological control document.

Any maintenance work in radiation areas R3 or R4, or contamination areas C2, C3 or C4 must not be undertaken unless it is covered by a Safety Document with Radiological Control Document. Further, access only to R4 or C4 areas must also be covered by a Safety Document with Radiological Control Document.

A Safety Document with Radiological Control Do­cument is issued by a Senior Authorised Person (Nu­clear Radiations), SAP (NR) who is responsible for specifying the radiological precautions. The SAP (NR) may call on the Health Physicist for advice in pre­paring the content of the radiological section at any time if it is thought necessary. However, the rules specify that this advice must be called for when work is to be done in a region which is normally sealed and which may contain loose radioactivity. This advice is issued in the form of a Health Physies Certificate by an Accredited Health Physicist.