Environmental Engineering Reference
In-Depth Information
CLB-A technique:
of metrics and weight coefficients and takes into
account features of technological and architectural
aspects of applied diversity (sensors, HW, SW,
design, etc.).
Besides, an acceptable value of diversity cor-
relates with NUREG-A in this technique.
1. Features of CLB-based assessment technique
are the following:
a. It is based on a classification of diversity
types described in (Kharchenko, 2011)
and detailing NUREG classification.
b. A main document is a multilevel check-
list (CL) and questionnaires for assess-
ment of diversity type application.
c. Diversity metric is normalized [0,1].
d. It may be used as a stage of I&C safety
assessment (calculation of ?-factor,
reliability and safety indicators using
RBD or MM).
2. Assessment procedure consists of the fol-
lowing stages:
a. Analysis of I&C specification, design
and development process.
b. Identification of MVS types, product/
process diversity (according to pre-
sented CL).
c. Determination of metric values for
different n types of applied diversity
(local diversity metrics μ
i
for diversity
type di, metrics μ
ij
for diversity subtype
dij.
d. Determination (correction) of weight
coefficients ω
i
(ω
ij
) of metrics.
e. Calculation of the general diversity
metric μ for system:
Diversity Assessment Tools
NUREG-A-based tool:
NUREG-A-based tool sup-
ports corresponding technique and allows calculat-
ing the diversity metric according to attributes and
criteria, values of weights (Kharchenko, 1999).
CLB-A-based tool:
Tool DivA (Diver-
sity Analysis Helper) (Kharchenko, et al., 2012;
Kharchenko, et al., 2012), is based on CLB-A and
has main window displays (Figure 27):
• Hierarchy (multi-level and extensible) of
diversity types.
• Calculated results (weights, metrics,…)
• Options for metric calculations.
Green colours mean diversity type is included
in result of calculation. Gray colours mean diver-
sity type is disabled for managing. User can add
new diversity subtype for a selected type.
There are a few metric calculation options:
•
Fixed Value:
User inputs metric manually.
•
Value determined by children:
Metric is
calculated as the sum of sub-types metrics.
•
Pre-deined value:
Shows an additional
window, where a user can select pre-de-
ined metric.
•
Value determined by help questions:
Shows additional window with helper.
µ Σω Σω µ
=
, i = 1,…, n; j = 1,…, n .
i
ij
ij
i
GMB-A technique analysis:
This technique
is a next step of developing CLB-based one. It is
additionally based on a graph model of diversity
types for two-version I&C systems (number of
joint nodes, k; length of a minimal version, n
min
).
It details CLB-A technique regarding evaluation
The special window appears after selection,
for example, of “Pre-defined value” option on
main window. Features of this and other options
are the following:
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