Document: NUREG-0800
Document ID: 5e40cf60-028d-44c3-b9b8-735a6a68a48a
Document Type: srp
Title: Revision 6 - August 2016
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML1602/ML16020A036.pdf
Revision Date: 2023-06
Chapter: 7
Section ID: 7
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Content:
missions describing a software development process or verification methods that include real-time concerns. Limiting Response Times Limiting response times should be shown to be consistent with safety requirements (e.g., suppress power oscillations, prevent fuel design limits from being exceeded, prevent a non-coolable core geometry). Setpoint analyses and limiting response times should also be shown to be consistent. The reviewer should verify that limiting response times are acceptable to the organizations responsible for reactor systems, electrical systems, and plant systems before accepting the limiting response times as a basis for timing requirements. Digital Computer Timing Requirements Digital computer timing should be shown to be consistent with the limiting response times and characteristics of the computer hardware, software, and data communications systems. Computer system timing requirements that should be addressed in software requirements specifications are described in SRP BTP 7-14, “Guidance on Software Reviews for Digital Computer-Based Instrumentation and Control Systems.” Architecture The level of detail in the architectural description should be sufficient that the Staff can determine the number of message delays and computational delays interposed between the sensor and the actuator. An allocation of time delays to elements of the system and software architecture should be available. In initial design phases (e.g., at the point of design certification application), an estimated allocation of time delays to elements of the proposed architecture should be available. Subsequent detailed design and implementation should develop refined timing allocations down to unit levels in the software architecture. A design should be feasible with currently known methods and representative equipment. Design timing feasibility may be demonstrated by allocating a timing budget to components of the system architecture so that the entire system meets its