Influence Diagram Modeling of Nuclear Spare Parts Process

Headnote

Abstract

Spare parts inventory levels at nuclear generation plants have neared all-time highs at some facilities. As part of an ongoing research project, the authors are developing a decision making framework for nuclear spare parts management. This paper describes the use of an influence diagram model to represent the existing spare parts process at a United States nuclear facility. We then discuss how this model can be extended to develop an interview protocol for subsequent data collection using the Analytic Hierarchy Process. The influence diagram drives the overall analysis of determining best practices for the spare parts process for continuous improvement.

Keywords

Electric utilities, influence diagram, spare parts, nuclear power

1. Background

The United States nuclear energy industry has faced challenges in recent years. Plants are aging, and many states have begun to deregulate electricity generation. Under regulation, costs of doing business were recovered in customer rates. However, under deregulation, cost recovery of generation-related expenses is no longer guaranteed as utilities are now operating as competitive businesses [1]. Therefore, management processes must be reengineered to support the competitive business environment. One such area that needs particular attention is plant spare part management.

Spare parts inventories have neared all-time highs at some nuclear facilities. Under regulation, the costs of buying and holding spare parts were recovered. Parts were kept on-hand in the name of plant safety. However, Scala, Needy, and Rajgopal [2] argue that plants have many safety systems in place to effectively shut down the plant if it became compromised in some way and that spare parts are more typically held to prevent revenue loss. As a result, a need exists to improve spare parts management support. The authors are engaged in a research project to address spare parts management and are working to build a quantitative model that minimizes plant downtime and revenue loss while maintaining plant safety. For a further discussion on deregulation and the nuclear spare parts problem, see [1, 2].

The authors' model will address the criticality of the part with respect to the utility's bottom line. That is, if something fails in the plant, and the parts are not available to fix it, the plant may have to be off-lined or de-rated, depending on the system that failed and...