Resolution of Generic Safety Issues: Issue 64: Identification of Protection System Instrument Sensing Lines ( NUREG-0933, Main Report with Supplements 1–34 )
Protection systems in nuclear power plants are required to meet the design criteria of IEEE-279, "Criteria for Protection Systems for Nuclear Power Generating Stations."397 One of the criteria of IEEE-279 requires that "...the protection system equipment (for example, interconnecting wiring, components, modules, etc.) shall be identified distinctively as being in the protection system. This identification shall distinguish between redundant portions of the protection system."
An area which has not been considered to be within the scope of this requirement is the mechanical sensing lines of the instrumentation which feed the protection system.
Since the sensing lines are essential to the reliable operation of the protection systems, identification of these lines would facilitate verification that sensing lines are appropriately separated and protected from external hazards.
ICSB proposed that OL applicants be required to identify protection system instrument sensing lines in accordance with a BTP drafted in 1982.398 DL did not issue the draft position based on their conclusion that it was a new requirement and, therefore, needed CRGR review.399 ICSB subsequently transmitted their position to CRGR.400 This position was to apply to all plants receiving an operating license six months after issuance of the position.
CRGR concluded that there would be little safety benefit derived from implementing the proposed requirement. Based on this conclusion and their cost estimates, CRGR rejected the proposed requirement and suggested that the issue continue to be considered as part of the proposed Regulatory Guide IC 126-5 which endorses ISA Standard S67.02.401
Based on the above CRGR action, we conclude that this issue has been RESOLVED and its resolution has resulted in no change in requirements, unless altered by actions on the future Regulatory Guide.