United States Nuclear Regulatory Commission - Protecting People and the Environment

TH27  Defense-in-Depth: A Historical Perspective within a Dynamic Regulatory Framework

Since the beginning of the peaceful use of nuclear energy, the idea that multiple barriers – physical and procedural – has been used to prevent and mitigate the consequences of events to protect the public from the harmful effects of radiation. This concept is embodied in the philosophy of Defense-in-Depth (DID) that is a cornerstone of every safety decision made by regulators and users of nuclear energy.  The NRC is nearing completion of a NUREG documenting the history of DID covering all of the uses of nuclear energy (power generation, materials, medical, waste, transportation, and security) building on insights gained from both domestic and international efforts.  While the specific terminology and how the concept is implemented may be different depending on the program area, the underlying philosophy is the same.  The goals of this session are to share the history of the development of this concept, move past the differences in terminology and implementation to understanding how DID has been used within a dynamic regulatory framework, and DID’s role in safety decision-making.  From the discussions participants should have a better understanding of how DID has been used, what the impediments to its use have been, and solutions to overcome these impediments.  Insights from the international community, the NRC, the nuclear industry, and non-government organizations will provide an opportunity for a broad range of views on DID and its role in assuring public health and safety.  An outcome of the sessions is that hopefully participants will have a better historical perspective on DID that will support more effective safety decision-making by both regulators and the users of nuclear energy.




  • John Nakoski, Branch Chief, Division of Risk Analysis, RES/NRC tel: 301-251-7612, e-mail: John.Nakoski@nrc.gov
Page Last Reviewed/Updated Friday, June 05, 2015