Document: NUREG-0800
Document ID: a2598df1-7ec6-43a6-9d2a-d8210d1f944f
Document Type: srp
Title: through 7.9. Additional information relevant to the review process can be found in the references in
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0525/ML052500461.pdf
Revision Date: 2023-06
Chapter: 7
Section ID: 7.1
CFR Part: 
CFR Title: 

Content:
e topics are discussed in more detail below. B.1. Qualification of Digital Instrumentation and Control Systems and Components Digital I&C systems require additional design and qualification approaches than are typically employed for analog systems. The performance of analog systems can typically be predicted by the use of engineering models. These models can also be used to predict the regions over which an analog system exhibits continuous performance. The ability to analyze design using models based upon physics principles, and the ability to use these models to establish a reasonable expectation of continuous performance over substantial ranges of input conditions are important factors used in the qualification of analog systems design. These factors enable extensive use of type testing, acceptance testing, and inspection of design outputs in qualifying the design of analog systems and components. If the design process ensures continuous behavior over a fixed Rev. 4 — June 1997 SRP 7.0-A-4 range of inputs, and testing at a finite sample of input conditions in each of the continuous ranges demonstrates acceptable performance, then performance at intermediate input values between the sampled test points can be inferred to be acceptable with a high degree of confidence. Digital I&C systems are fundamentally different from analog I&C systems in that minor errors in design and implementation can cause them to exhibit unexpected behavior. Consequently, the performance of digital systems over the entire range of input conditions cannot generally be inferred from testing at a sample of input conditions. The use of inspections, type testing, and acceptance testing of digital systems and components does not alone accomplish design qualification at high confidence levels. To address this issue, the Staff's approach to the review of design qualification for digital systems focuses, to a large extent, upon confirming that the applicant/licensee employed a high-quality