Document: NUREG-0800
Document ID: 96afb1d6-6ce9-41e4-b4ec-1fc7747bc0b2
Document Type: srp
Title: Revision 8 – January 2021
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML2033/ML20339A647.pdf
Revision Date: 2023-05
Chapter: 7
Section ID: 7
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ess point 4, design information showing the following: – controls and displays provided in the MCR to perform manual system- or division-level actuation of critical safety functions – controls and displays are independent and diverse from the equipment performing the same functions within the proposed DI&C system, so that they are not vulnerable to the same CCF as the proposed system – controls and displays have sufficient quality to support the manual operator actions during the associated event conditions, if the equipment used is NSR 6. Additional Items for Consideration The reviewer should use the acceptance criteria described in Section B.3 of this BTP and the detailed guidance of NUREG/CR-6303 and NUREG/CR-7007 to evaluate the applicant’s D3 assessment. During this evaluation, the reviewer should consider the topics described below. 6.1 System Representation as Blocks As described in NUREG/CR-6303, a block is a representation of a physical subset of equipment and software for which it can be credibly assumed that internal failures, including the effects of latent design defects, will not propagate to equipment or software outside of the block. A block can also be a software macro or subroutine, such as a voting block or a proportional–integral– derivative block, that is used by multiple functional applications. Representations of systems or components using blocks may not show the inner workings of each block. Typical examples of blocks are computers, local area networks, software macros and subroutines, and programmable logic controllers. When a block is used by multiple design functions using the same software (within the logic or divisions), a failure within the block can result in a CCF of all design functions that use that block. The reviewer should consider whether the applicant’s D3 assessment describes the diversity of the proposed DI&C system or component across blocks. When considering the effects of a postulated CCF, the reviewer may