The dynamic nature of risk in DOE facilities in the surveillance and maintenance program-with observations for risk communications.

We explore three case studies of facilities at two US Department of Energy (DOE) former nuclear weapons research and production sites-the Oak Ridge National Laboratory and the Hanford site-whose risk profiles have changed during their long-term management under the DOE's surveillance and maintenance (S&M) program. These case studies provide examples of the challenges faced in communicating to external stakeholders, such as federal and state regulators, local communities surrounding the site, as well as the general public, the circumstances surrounding unexpected events or the emergence/discovery of new risk-important information at historically high-risk sites. We identify common topics of importance from these case studies and suggest a taxonomy for risk communicators to use in informing the dialogues with individuals and organizations that may not be technically oriented or fully informed on the subject matter. The taxonomy is based on technical insights from the quintessential definition of risk known as the Kaplan-Garrick "risk triplet" as well as insights from regulatory guidance documents on risk communication with external stakeholders originally developed for the commercial nuclear power industry.

A structural description of the evolution of stakeholders and risk communication in the Department of Energy's defense nuclear facilities: Historical perspective, major stakeholders, and external events.

Regulators and policymakers are routinely challenged with explaining complex concepts concerning risk. Part of the challenge is helping external and internal stakeholders to understand the context behind risk-related information and decisions. This paper will describe the historical evolution of the safety and regulatory framework for an important category in the nuclear industry-defense nuclear facilities owned and operated by the US Department of Energy. In parallel with describing this evolution, three major events which occurred external to the complex of defense nuclear facilities will be summarized, and their impact on the maturation of the Department's safety and regulatory framework will be discussed. Finally, integrated with these two threads of discussion will be a chronicle of the changing set of involved organizations and the expanding set of external stakeholders involved in risk decisions-and therefore, the risk communications ecosystem surrounding defense nuclear facilities. It will be noted that this system was once describable as a classic "iron triangle," but now has progressed to a complex network of federal and state organizations, numerous congressional committees, and expanding sets of external stakeholders. It is hoped that a comprehensive discussion of the context of risk assessment in the defense nuclear facilities complex-addressing historical insights, organizational evolution, and the maturing structure of regulation-will provide enhanced opportunities for building trust and understanding in this complex environment.