EFTed - Event/Fault Tree Editor and Display

Printable version of all EFTed Help Pages.

Contact Information

Contact:	Robert H. Morris	PO Box 2008, MS 6085
	Program Manager	Oak Ridge, TN 37830
	Modeling and Simulation Group	tel: (865) 576-5878
	Computational Sciences and Engineering Division	fax: (865) 576-0003
	Computing and Computational Sciences Directorate	email: visac@ornl.gov
	Oak Ridge National Laboratory	web: visac.ornl.gov

Overview

EFTed is a graphical editor/display program for event tree/fault tree problems. EFTed can be used as a standalone program to prepare the input decks for EFcalc, or called from within other programs, such as VISAC. EFTed can be operated in three modes:

view mode - where the entire structure of the event trees and fault trees can be viewed
edit mode - where the event trees and fault trees can be changed
results mode - where the results of the event/fault tree calculation are also displayed

Input/Output Files

The files that EFTed uses are all described in the documentation for EFcalc. For each project, the following files are required: *.bas, *.equ, *.etr, *.con. For results mode, the *.dmg and *.ans files are also required.

View Mode

The basic layout of EFTed is a set of tabbed panes showing each of the event trees in the given problem. Each event tree can be viewed by clicking on the tab for that event tree.

Event trees consist of a set of sequences, defined as the failure or non-failure of specific fault tree gates. At the end of each sequence is either a consequence name or the name of another event tree. In the example above, the first of five event trees is shown. It has four consequences defined by the failure or non-failure of two fault tree gates: "loop" and "loca". Each sequence leads to another event tree, which can then be viewed by clicking on its tab. This is referred to as a master event tree that points to four different slave event trees.

The top of any event tree consists of a banner listing the top-level gates of the fault trees. Associated with each of these major systems is a simple failure probability. The simple failure probability is the probability that the system will fail when the initiating event occurs, independent of any damage inflicted on the components of the plant.

To view the fault tree associated with a top-level gate listed in the event tree banner, simply left click on its name. A more detailed description of a top-level gate can be found by positioning the mouse cursor over the name. For example, placing the cursor on the "loop" button, a pop-up window will display "Off Site Power". Clicking on "loop" gives us the fault tree for the "loop" gate, shown below.

Note that the typical symbols used in probabilistic safety analysis are used to display the fault trees. Gates are shown as either an AND gate (blue symbol above), an OR gate (red symbol) or a TRANSFER gate (yellow triangle). Individual components of the plant are shown as basic events (pink circles). Gates can consist of any number of other gates and basic events. TRANSFER gates can be shown by left clicking on the either the triangle or the name box above the triangle.

In any of the three modes, more detailed information about a gate or basic event can be obtained by right clicking on the symbol or name box.

Edit Mode

In edit mode, EFTed allows the event trees and underlying fault trees to be changed in a variety of ways. The menu bar at the top of the event tree window allows users to do the following:

Add/Edit consequences
Add a new Event Tree
Edit Event Tree properties (its name and its description)
Delete an Event Tree

Within the event tree that is shown, columns can be added or deleted and sequences can be added or deleted. Below is the event tree for "LPLA", a loss of off site power and a loss of coolant accident at the same time. The edit targets can be toggled on/off using "Display/Toggle Edit Targets" menu bar.

The following editing actions listed in the table below can be made to an event tree in edit mode.

Desired Edit	Mouse Action	Where	Comment
add a column	left click	green arrow	The arrow shows where the new column will be placed. One can add a column based on an existing gate or a new gate.
delete a column	right click	green arrow	Only on columns that have no forks.
add a failure path	left click	green fork	Duplicates consequence of above branch.
delete a failure path	left click	red circle-x	Only works on undeveloped branches.
change consequence	left click	consequence	Can ony choose from existing list. To add new consequences, first define them using the "Edit/Add-Edit Consequences" menu bar.
change simplefailure probability	left click	probability	Actually, this is associated with the top-level gate, not the event tree.
view fault tree	left click	column name	Gives editable fault tree in separate window.

For editing fault trees, right clicking on any gate or event will show a pop-up a menu with five choices:

copy - this selects the gate for copying. When copying a basic event, both the old and new events will be shown. When copying a gate, the gate will move to its own fault tree window and both the old and new locations of that gate will be replaced by the TRANSFER gate symbol.
paste - this will paste the gate or event currently in memory as a child of selected gate
delete - will delete this gate
add input - will bring up a screen allowing user to specifiy child gates and events
edit properties - for changing gate description, logic type (AND or OR)

Of course, not all of the above options will be enabled for each type of gate.

Six different operators can be used. They are listed in the table below.

name	inputs	failed if ...
and	>0	all inputs are failed
or	>0	at least one input is failed
not	1	input is not failed
nand	>0	at least one input is not-failed
nor	>0	all inputs are not-failed
xor	2	only 1 input is failed

Some editing options are also available without the pop-up menu. A gate or basic event can be moved to a different location on the tree by left-clicking and dragging it to its new parent. Clicking on a TRANSFER gate will bring up a separate window for that gate.

When done editing, use the menu bar "File/Save" to save your changes. Use "File/Exit" to leave the program.

Results Mode

The results of the event/fault tree calculation are shown for each sequence of each event tree and the failure probabilities for each gate and basic event is shown in the fault trees. Failure probabilities of each event tree branch point are also given. Only event trees that have a probability of occurring are shown in the tab list.

In the example above, the damage to the plant was such that off-site power was lost with a 100% probability, making the sequences in the "RT" and "LOCA" event trees impossible. Only the "LOOP" event tree has a non-zero result that can be displayed.

For a slave event tree, the highest probability of a certain consequence can be highlighted in red. The consequence of interest is chosen using the menu bar "Display/Choose Active Consequence". An example for "moderate - moderate core damage" is shown below.

The red line immiedatlely shows the user which system will likely cause the selected consequence. The user can then display that gate by left clicking on the top-level gate name.

In this example, the "ep" fault tree failed due to the failure of "control", which is shown above. Note that gates and basic events with high failure probabilities are easily found with the large-red "X" placed on their symbols. The threshold value, above which the red "X"'s will show, can be changed by the user by using the menu "Display/Set Kill Threshold" command. The above example has the kill threshold set to 0.75.

Oak Ridge National Laboratory, 2004

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