Walkdowns - s1073ch20056

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identified in walkdowns. Vertical slice assessments are primarily diagnostic and would not generally

produce discrepancy resolutions or as-built documents.

Walkdowns. During walkdowns, the as-found configuration is identified by comparing the existing

physical configuration with the facility documentation to identify any discrepancies, typically by marking

up the documents. Appendix 11C provides detailed guidance for conducting walkdowns. Walkdowns

are sometimes conducted to record manufacturers' nameplate data from equipment, to identify missing

or incorrect equipment labeling, to determine the present material condition of equipment, and to

identify potential physical interactions between equipment (such as non-seismically qualified equipment

mounted In such a position as to impact seismically qualified equipment during an earthquake).

Physical configuration assessments may be performed on a sample basis, with the sample providing a

representative cross-section of component types within the system being assessed. The sample should

be large enough to ensure that a statistically significant portion of the system and its components are

chosen. For instance, the sample should Include major and minor components, large and small bore

piping, and instruments and controls. Minimum thresholds for determining an acceptable number of

discrepancies should be established prior to walkdowns based on proven statistical techniques (e.g.,

similar to those used in quality programs for the selection of samples and the determination of

acceptability).

If the initial physical assessments confirm that the facility documents accurately reflect the physical

configuration, further physical configuration assessments should be included on a sample basis with

periodic program effectiveness assessments. However, if the initial physical assessments indicate that

substantive discrepancies exist (either in number or type) between the physical configuration and its

documentation, appropriate immediate corrective actions should be identified to establish agreement

between the physical configuration and the facility documentation.

The corrective actions for substantive discrepancies include additional walkdowns to characterize and

determine the extent of the problem. Sometimes the discrepancies can be isolated to certain systems,

certain modification vintages, or certain change mechanisms (modification processes). If the extent of

the problem can be limited, appropriate corrective actions can be directed at the root cause. Where

control of the physical configuration has been lost, walkdowns of every important system may be

necessary. In this case, a justification for continued operations may be necessary if continued

operations are desired.

As-Builting Process. As-builting is a process that involves determining the actual physical configuration

that exists at a point in time, identifying any discrepancies with the facility documentation, and

technically resolving those discrepancies. In some cases, discrepancies arise simply because the

facility documentation is incomplete or inaccurate in some details. In other cases, discrepancies arise

because inadequately controlled hardware changes caused the physical configuration to become

different from the facility documentation. The level of detail of a particular facility document type

establishes the threshold of the corrections that need to be made. If a facility document provides, or is

intended to provide, a level of detail that includes information that does not agree with the actual

physical configuration, those discrepancies should be identified and resolved. Leaving incorrect or

unverified information on a document is likely to mislead users of the document. Further, any

information that is left on as-found documents and has not been verified should be clearly identified.

The resolution of the as-found discrepancies needs a technical review to determine if the physical

configuration is correct (in accordance with the currently-approved design requirements) or if the facility

documentation is correct (the physical configuration is not correct). In some cases, the resolution of a

discrepancy might be to establish the acceptability of the existing physical configuration and change the

design requirements. Technical approval from the design authority (i.e., design verification) should be

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