Analytical MORT

The development of MORT was initiated by the U.S. Atomic Energy Commission, and is described in Johnson (1980). MORT is a comprehensive analytical procedure that provides a disciplined method for detennining the causes and contributing factors of major accidents. It also serves as a tool to evaluate the quality of an existing safety program. 

A last reference here is the Guide to Use of the Management Oversight and Risk Tree (MORT). In the abstract for that publication, MORT is described as a comprehensive analytical procedure that provides a disciplined method for determining the systemic causes and contributing factors of accidents. This reference to performance errors is of particular interest. 

NRI. 2002. MORT user s manual. For use with the management Oversight Risk Tree analytical logic diagram, NRI, 2002. 

Like HazOp, MORT refers to both a specific analytical tool and to a broad approach to system safety. 

Analytical tree construction can be accomplished with only seven different symbols, even though some programs like MORT include a few other special purpose symbols. 

Buys, J.R. 1977. Standardization Guide for Construction and Use of MORT-Type Analytical Trees. ERDA 76-45/8 SSDC-8. Idaho Falls, ID Energy Research and Development Administration. 

The project evaluation tree is an analytical tree to be used primarily as a graphic check in basically the same manner as the management oversight and risk tree (see Chapter 18). The PET chart, however, contains fewer than 200 event symbols and no transfers the MORT chart contains approximately 1,500 events symbols, multiple transfers, transfers within transfers, and drafting breaks. The PET chart is divided into three branches procedures, personnel, and plant and hardware. 

The symbols used on the MORT chart are basically those used for other analytical trees (Chapter 10) and fault tree analysis (Chapter 15). They include the rectangle as the general event symbol, the circle as the base event symbol, the diamond as an undeveloped terminal event, the and gate, the or gate, and the ellipse as a constraint symbol (Rgs. 18-1 and 18-2). 

Figure 18-3 Transfers In addition to the triangle commonly used as the transfer symbol for analytical trees, the MORT chart also uses large capital letters as drafting break transfers and small ellipses as transfer symbols for assumed risks.

SSDC 5 Reported Sigruficant Observation (RSO) Studies SSDC 6 Training as Related to Behavioral Change SSDC 7B DOE Guide to the Classification of Recordable Accidents SSDC 8 Standardization Guide for Construction and Use of MORT Type Analytic... 

The ETBA is an analytical technique that can be of great assistance in preparation of the preliminary hazard list (PHL). It can also be quite useful in the development of a preliminary hazard analysis (PHA), subsystem hazard analysis (SSHA), or the more general system hazard analysis (SHA). The ETBA can also be used, depending on the specific system under consideration, in the development of the operating and support hazard analysis (O SHA), and, of course, during the MORT process from which the ETBA evolved. 

An analytical logic tree or diagram, from which MORT derives its name... 

In general, the remainder of this chapter focuses on the explanation of the various MORT event tree symbols and their use and meaning. Since the tree is an analytical model, the information presented in the previous chapter (on fault tree analysis) will be helpful and should be reviewed. 

The primary symbols used for most analytical trees have been used in the MORT event tree as well. These include the rectangle (primary or top event, and secondary, contributory or main events), the diamond (undeveloped event), the circle (basic event), the and gate, the or gate, the oval (conditional or constraint symbol), and the triangle (transfer gate or symbol). In addition to these symbols, the MORT... 

MORT can be equally useful and even more valuable, however, as an analytical tool to reduce or eliminate potential sources of accidents. Such uses have been frequent, but not widespread moreover, their application to criticality safety problems, with certain exceptions, has been neglected. Yet criticality safety requires the kind of thorou, highly disciplined, and carefuUy documented analysis that can be greatly strengthened by the use of MORT techniques. In addition, the author believes that training criticality safety professionals in the use of MORT early in their careers would not. only speed up their ability to use their formal training effectively, but would induce, at an early st in their career, those mental attitudes and disciplines prerequisite to effective performance. 

MORT User s Manual—For Use with the Management Oversight and Risk Tree Analytical Logic Diagram. DOE-76/45-4, SSDC, Revision 3. Washington, DC Department of Energy, 1992. Also available at http //www.eh.doe.gov/analy sis/trac/SSDC doc/l0003.txt. 

The primary symbols used for most analytical trees have been used in the MORT event tree as well. These include... 

Figure 13.3 The top branches of the MORT analytical event tree (Source DOE. ...

Project Evaluation Tree A system safety analytical technique which was developed from the more extensive management oversight and risk tree (MORT) method of analysis. A simplified and efifieient method to evaluate a project or operation. Especially usefiil in the analysis of accidents and hazards. 

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