Vertical and Horizontal Slice Assessments

DOESTD107393

I-B.5 ASSESSMENTS ELEMENT

Performance of the assessment element functions occurs over three phases or stages: Initial

Assessments (performed to support CM program planning); Post-Implementation Assessments

(performed after the development of various CM programs, program elements, and functions); and

Ongoing Assessments (established during CM program development and performed throughout the

operational life of the facility). Figure I-B-2 shows the major assessment functions or activities, grouped

by appropriate time frame, that are necessary to fully establish the assessments element.

The initial vertical and horizontal slice assessments accomplish the initial CM programmatic

effectiveness and initial physical configuration assessments. The initial CM programmatic assessments

review various existing programs, processes, and information related to configuration management to

determine which of these are already adequate for an effective CM program and which need

improvement. One-time, post-implementation assessments provide assurance that the CM program

elements and functions have been properly developed and are being implemented effectively. The

ongoing assessments provide assurance that proposed changes are acceptable and properly

implemented, that equipment continues to meet its design requirements, and that the overall CM

program is effectively meeting Its objectives.

Some functions fall into more than one timeframe. For instance, CM programmatic assessments are

conducted in the initial, post-implementation, and ongoing timeframe; physical configuration

assessments are also conducted in each time frame. Each of the assessments element functions has

ongoing activities.

Vertical and Horizontal Slice Assessments. The main objective of the initial CM assessments is to

assess existing programs and processes related to configuration management (such as change control,

the design process, and document control) in order to identify strengths and weaknesses as early in the

development phase as possible to determine whether upgrades are necessary. The extent of existing

CM functional deficiencies can be determined by assessing the technical adequacy and consistency

among the design requirements, physical configuration, and documentation. The magnitude and

underlying cause(s) of these deficiencies establish the foundation for improvements.

Initial programmatic assessments are a combination of vertical slice and horizontal slice assessments.

Vertical slice assessments are top-down, diagnostic evaluations performed on a selected system across

various programs that affect the hardware system. The primary objective of this application of vertical

slice assessments is to determine which programs have been effective for that facility system and which

programs have not been effective. Horizontal slice assessments concentrate on a single program, such

as change control or document control, and are also diagnostic, but cut across many systems to

determine the effectiveness of the program. Horizontal assessments also include assessments of topics

(such as seismic or fire protection) across many systems and organizations. Both assessments types

use many similar assessment techniques, although the focus is different.

Each assessment type can identify problems in existing control programs related to configuration

management through different but complementary approaches. Although it is necessary to correct

specific weaknesses that could cause system unavailability or unreliability, the primary purpose of these

diagnostic assessments is to identify the underlying causes that could affect other systems and

programs. Information acquired through these assessments is used to establish the basis for the CM

program development and implementation efforts. Increased in-house knowledge of system design and

program operation is an additional benefit of the assessment.

A frequently used form of a vertical slice assessment is the Safety System Function Inspection (SSFI).

Although an SSFI is not the only method for performing a vertical slice assessment, it is the

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