|
Product Info
>> Features
WinNUPRA is a software
package for performing probabilistic risk/safety assessments (PRAs/PSAs). The system
consists of six major analysis modules designed to generate and analyze minimal cutset
solutions of various fault trees and cutset equations for accident sequences. Operations
are provided for direct solution of fault trees, for their minimum cutsets, and for
Boolean manipulation (merging) of cutset equations. The basic functions of each of the
modules are presented below.
Event Tree Editor
The Event Tree Module allows you to create, edit,
quantify, and print Event Trees. An event tree is a graphical representation of a sequence
of functional states or events and their consequences. It is a technique for tracing an
accident sequence following an initiating event in terms of the success or failure of
significant subsequent actions. These actions include both accident-mitigating actions and
normal operating actions; they can be either system actions or operator actions. The
purpose of event tree analysis is to identify those event sequences leading to the defined
undesirable event.
Fault
Tree Editor
The Fault Tree Module works primarily with fault
tree files (file type LGC). A major portion of the functions in this module are
devoted to creating and editing fault tree files that can be displayed in WinNUPRA's fault
tree graphic format. Additional options allow you to:
 | Print graphs of the fault trees in WinNUPRA format or formatted listings
of fault tree components. |
| Update fault tree event descriptions from BED (Basic Event
Database) files or vice versa. |
| Update the data in Linked Fault Trees from BED files. |
| Export a WinNUPRA fault tree for use in the SETS analysis program. |
In WinNUPRA, three basic event groups are used: Basic Events,
Gates, and Transfers. A Basic Event is an event having no other events
contributing to its failure. A Gate is a logic gate to which other events are logically
connected. Gates can further be represented by three logical types: AND gates, OR
gates, and K out of N gates. Transfers represent a connection between separate
parts of a fault tree model (internal transfer) or may connect different fault trees
(external transfer).
In WinNUPRA, fault trees are developed in virtual
"pages". Each "page" of a fault tree contains a grid of 12 rows by 6
columns. Transfers are used to connect the fault tree logic from one virtual page to the
next virtual page within a fault tree. In this format, gates play an important role in the
graphical structure references. Each gate is uniquely named according to the fault tree
name, page number, and page position.
Data File Editor
The Data File Editor is used to edit the data
files. Three types of data files are used: PRM (parameter file), BED (basic
event data file), and SEQ (sequence file). The PRM file contains parametric
failure data applicable to a specific component type and failure mode. The BED file
contains component and failure mode specific data. BED files are also used to
"set" house events. The SEQ file contains sequence data developed from
the selected event trees.
Six different types of basic events are supported in WinNUPRA. These
are:
| Repairable (Type 1), |
| Periodically Tested (Type 2), |
| Failure on Demand (Type 3), |
| Running Failure (Type 4), |
| Module (Type 5), |
| Logical (Type 6). |
Display and Edit operations can be performed on records in all
the file types: Basic Event Data Files (file type BED), Parameter Files (file type PRM),
and Sequence Files (file type SEQ). The module also contains several options to
automatically update one type of data file from another or to recalculate values in the
records of the file being edited. Finally, new BED files can be created by copying
an existing BED file or selecting a subgroup of events from an existing BED file.
Calculation
Module
The calculation operations and related options
performed in the Calculation Module are listed and described below.
Link Fault Tree
Since fault trees may contain external transfers, to be solved they
must be connected or "Linked" together. This function links the desired fault
trees and saves the resulting "linked" tree in a file with the extension LKC.
Solve Fault Tree for Cutsets
This function is used to generate the minimal cutset equation for the
desired fault tree logic model. Both unlinked (LGC) and linked fault trees may be
solved. The resulting cutset equation is stored in a file with the extension EQN.
Edit Cutsets
Some function cutset equations or sequence cutset equations may require
further analyst input before they are used to quantify or merge event tree sequence
equations. These changes generally come under the heading of cutset editing. Typical
reasons for this are the absence of "NOT" gate modeling, operator actions or
common cause failures that may have been modeled inconsistently. Therefore a cutset editor
is provided to allow the user to manually edit a cutset equation (EQN) file. If a
large number of systematic changes are desired, this feature can be used in an automated
mode.
Merge Cutset Equations
When minimal cutset solutions are available for the individual
functional events in an event tree file, the sequence cutset equations for the accident
sequences in that event tree can be created. The minimal cutset solutions for the
challenged events in each accident sequence are combined with Boolean operators to produce
the sequence cutset equation. Merging performs this process, as well as the deletion of
cutset equations that represent impossible combinations of events.
Concatenate Cutset Equations
A series of cutset equations can be joined together. Concatenation is
the ANDing together of independent cutset equations. This operation concatenates all of
the core melt sequence equations into a single plant damage equation. The resulting
equation can be truncated, if desired.
Quantify a Cutset Equation
This operation substitutes the point estimates for the frequency of
basic events into the cutset equation and calculates the numerical value for the failure
probability or event frequency represented by that cutset equation.
Minimalize a Cutset Equation
Occasionally, non-minimal cutsets may be generated or there may be
doubt about whether the cutsets obtained are minimal. This can occur when the results of
several types of analyses (internal, fire, flood, seismic, etc.) are combined. This
operation processes a cutset equation and performs a Boolean reduction, resulting in a
minimalized cutset equation.
Batch Processing
All of the above listed functions can be performed together in a single
batch operation. This completely automates the solution process. If minor changes to a
quantification are desired, the instructions can be easily modified to perform only the
operations necessary to incorporate the change. The Batch Process in WinNUPRA 2.1 also
includes Importance Analysis, Sensitivity Analysis, and Uncertainty Analysis.
Results Module
As its name implies the WinNUPRA Results Module
works with the results from operations in other modules, particularly with results from
the computational operations in the Calculation Module.
The Integrated Results options are used to display and print
summary reports of the accident sequence data produced in the Calculation Module. The
results can be sorted by Initiator, Sequence, Status Class, Component Failure, or
Component Success. Selected groups of results can be charted and graphed.
Variational analyses on concatenated sequence cutset equations
representing a Level 1 PSA, can be performed to obtain measures of Importance, Sensitivity,
and Uncertainty. Importance is calculated using the following measures: Risk
Achievement Worth, Risk Reduction Worth, Generalized Importance, and Joint Importance.
Sensitivity analyses can easily be performed with respect to variation in parameter
values. The user can specify values for particular individual events and the outcome
frequency is re-computed for comparison with the frequency without the substitutions. The
Uncertainty Analysis option performs a Monte Carlo simulation, in a series of trials, on
the basic events, in the cutset equation for the outcome of interest. In each trial,
values of the parameter with defined distributions are chosen randomly from the parameter
distributions. The resulting basic event values are substituted into the cutset equation,
and the outcome frequency is computed. The results of many hundreds of trials are then
ordered by the outcome values. The fifth percentile, for example, in this distribution of
outcome values represents the 95% level of confidence that the actual values lies above
that outcome value.
The user can also view and print any of the viewable files in the
current model. He can display and interactively edit any WinNUPRA cutset equation file
with the Cutset Editor, as an alternative to automated editing of
cutset equations.
Tools Module
The Tools Module is a collection of useful Tools,
which supports creating and maintaining WinNUPRA models. The following tools are
available:
| Common Cause Failure Expansion
|
| Automatic Conversion of Undeveloped Basic Events to
External Transfers
|
| Automatic Conversion of External Transfers to
Undeveloped Basic Events
|
| Cross Reference Lists of all External Transfer Gates
|
| Detecting and fixing duplicate Fault Tree Identifiers
|
| 
