IEEE 497:2010 pdf free download – IEEE Standard Criteria for Accident Monitoring Instrumentation for Nuclear Power Generating Stations
6.4 lsolation
For Type A,Type B, and Type C variables，the transmission of signals between accident monitoringinstrumentation and any system not meeting the minimum design requirements stated herein shall bethrough isolation devices. These isolation devices shall be classified as part of the accident monitoringinstrumentation and shall meet the requirements of this standard. No credible failure external to theaccident monitoring instrumentation shall be transmitted through the isolation device in such a way as toprevent the accident monitoring channel from meeting the performance requirements. A failure of anisolation device is evaluated in the same manner as a failure of other equipment in the accident monitoringinstrumentation. Isolation devices shall meet the requirements of IEEE Std 384.
6.5 lnformation ambiguity
For Type A, Type B, and Type C variables, the failure of an accident monitoring instrument channel shallnot result in information ambiguity that could lead the operator to defeat or fail to accomplish a requiredsafety function (for example, the redundant displays disagree and the operator cannot readily deduce whichchannel has failed). If analysis shows that credible failures can result in information ambiguity, a signalvalidation technique should be employed. If the signal validation process cannot be automaticallyaccomplished，additional information shall be provided to allow the operators to deduce the actualconditions so that they may properly perform their role.
6.10 Control of access
The design shall permit the administrative control of access to instrument channel calibration adjustments,test points,and controls used to remove an accident monitoring instrument channel from service. Theseadministrative controls shall be supported by provisions within the accident monitoring instrumentation, byprovisions in the nuclear power generating station design, or by a combination thereof.
6.11 Maintenance and repair
Accident monitoring instrumentation shall be designed to facilitate maintenance,repair and adjustment.Consideration shall be given to potential inaccessibility during the accident in determination of equipmentselection and location.
6.12 Minimizing measurements
To the extent practical, the same variables and displays shall be used for accident monitoring as are usedfor normal operation of the plant to enable the plant operators to use, during an accident situation, variablesand displays with which they are most familiar.
6.13 Auxiliary supporting features
Systems or components that provide services that are required for the accident monitoring instrumentationto accomplish its functions shall meet the applicable requirements of that instrumentation. Auxiliarysupporting features for accident monitoring instrumentation provided for those variables identified inaccordance with Clause 4 are part of the related display channel and shall meet applicable criteria.
For example，a cabinet cooling fan required to maintain signal conditioning modules within designtemperature range is an auxiliary supporting feature.
Other components，equipment and systems that perform a function that is not required for the accidentmonitoring instrumentation to provide required information to the operator，and are part of the accidentmonitoring instrumentation by association (that is,not isolated from the accident monitoringinstrumentation) shall be designed so that these components,equipment and systems do not degrade thecapability of the accident monitoring instrumentation to function.
6.14 Portable instruments
When required as part of an EOP or an AOP, portable instruments may be used to obtain data. In suchcases, the instruments, the means of communicating data to the control room, and the means of analyzingdata to obtain information shall be considered part of the accident monitoring channels. The equipment thatforms part of this accident monitoring instrumentation shall meet the criteria for the applicable variabletype.