Safety conformity, design guidance

With regard to guidance on selection of application software design methods and techniques, systems with a safety requirement up to SIL 3 should be designed in accordance with the instructions given in the supplier s safety manual as part of a system conforming with lEC 61508. For SIL 4 systems, the developer should additionally confirm that the selected methods do conform with the requirements of lEC 61508-3. 

Protec ion of the Class IE power supplies to safety-related equipment from the effects of an undervoltage condition of the offsite power source thus conforms to the guidance of BTP PSB-1, and this issue is, therefore, resolved for the System 80+ Standard Design. 

Since the testing for pressurizer safety valves conforms to the guidance given in NUREG-0737 and since testing requirements on PORV, associated block valves, and ATWS events do not apply, this issue is resolved for the System 80+ Standard Design. 

The Memorandum of Guidance to the Electricity at Work Regulations refers to the Standard and notes that installations that are designed in conformity with it are likely to achieve compliance with the Electricity at Work Regulations 1989. The HSE s electrical inspectors will generally use BS 7671 as a main guide when checking the safety of electrical distribution systems. 

Effective human-machine interfaces for systems important to safety are necessary to provide the operator with accurate, complete and timely information on plant status and to enable proper operation of the systems controlled by the l C systems. The Requirements for Design require that systematic consideration of human factors and the human-machine interface be included in the design process (Ref. [1], para. 5.50). The human-machine interface for I C systems important to safety should conform to the guidance given in Section 6 of this Safety Guide. 

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