Document: NUREG-0800
Document ID: 6acfc377-3e1c-4cb9-b2d1-500f564d2f4b
Document Type: srp
Title: Draft Revision 6 – August 2015
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML1515/ML15159B011.pdf
Revision Date: 2023-06
Chapter: 7
Section ID: 7
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CFR Title: 

Content:
iting load conditions and be chosen by persons independent of the persons who designed the system. Both analytical and test techniques of timing analysis have drawbacks. It is difficult to demonstrate completeness of timing tests. Completeness is easier to demonstrate for analyses, but analyses predict extreme times that are not actually possible. Therefore, analysis and testing are often combined in a complementary manner to confirm that a system can meet the limiting response times. Measurement methods should be appropriate to the resolution and detail required. Timing measurements should meet projections or the anomalies should be satisfactorily explained (NUREG/CR-6083, Sections 2.1, 2.3.3, and 2.3.4). Use of Cyclic Real-Time Executive In systems that include a cyclic real-time executive (operating system), a typical cycle includes application modules, diagnostic modules, and other support modules. A watch-dog timer is normally set at the beginning of each cycle and reset at the end. If the cycle is not completed before the watch-dog timer period is complete, an error is generated. A basis should be provided that describes the cycle and demonstrates that the watch-dog timer is correctly implemented, the time required for the application modules does not exceed the allotted time given in the architecture timing budget, and diagnostic and other support modules will not cause the allotted time to be exceeded. Use of Part-Scale Prototypes In systems that have not been implemented and tested on a full scale, expected system delays on scale-up should be calculated and shown to be less than limiting system response times (NUREG/CR-6083, Sections 2.1.3 and 2.1.4). A basis should be provided that describes the effects of adding sensors, divisions, communication links, controllers, computer nodes, or actuation devices required to scale the test system to full scale. BTP 7-21-9 Draft Revision 6 – August 2015 Test data should confirm scaling as well as performance