Probabilistic Performance Assessment vs. the Safety Case Approach
- PDF / 748,006 Bytes
- 6 Pages / 432 x 648 pts Page_size
- 43 Downloads / 191 Views
MRS Advances © 2019 Materials Research Society DOI: 10.1557/adv.2018.681
Probabilistic Performance Assessment vs. the Safety Case Approach François Diaz-Maurin1,2 and Rodney C. Ewing1,3 1
Center for International Security and Cooperation, Stanford University, Stanford, CA 94305, USA Amphos 21 Consulting SL, C/ Venezuela 103, 08019 Barcelona, Spain 3 Department of Geological Sciences, Stanford University, Stanford, CA 94305, USA 2
ABSTRACT
The “safety case” approach has been developed to address the issue of evaluating the performance of a geologic repository in the face of the large uncertainty that results for evaluations that extend over hundreds of thousands of years. This paper reviews the concept of the safety case as it has been defined by the international community. We contrast the safety case approach with that presently used in the U.S. repository program. Especially, we focus on the role of uncertainty quantification. There are inconsistencies between the initial proposal to dealing with uncertainties in a safety case and current U.S. practice. The paper seeks to better define the safety case concept so that it can be usefully applied to the regulatory framework of the U.S. repository program.
INTRODUCTION Uncertainty quantification is one of the key issues in the safety analysis of geological repositories for radioactive waste disposal. In repository design, epistemic uncertainties arise when projecting coupled geophysical and geochemical processes over large temporal and spatial scales. These uncertainties limit the ability to predict the longterm behavior of the repository because of the unavoidable lack of knowledge about future geological conditions. In the U.S., probabilistic performance assessments (PPAs) have been used as the standard method in repository licensing [1]. Yet, the value of PPAs has been challenged [2]. PPAs include making probabilistic estimates of anticipated dose to the public or release to the environment hundreds of thousands of years into the future. These estimates are not compelling for regulatory decision-making because they cannot convincingly demonstrate whether a repository provides for a sufficient level of safety. Thus, one must expect public skepticism of statements that a repository is “safe enough.”
Downloaded from https://www.cambridge.org/core. Iowa State University Library, on 25 Jan 2019 at 05:44:02, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1557/adv.2018.681
PROBABILISTIC PERFORMANCE ASSESSMENT Probabilistic risk analysis (PRA) was developed for the safety assessment of engineered systems. PRA was applied to the safety analysis of nuclear power plants for the first time in 1975 in a report for the U.S. Nuclear Regulatory Commission (NRC) known as the “Rasmussen Study” [3]. During a workshop organized in 1976 by the ERDA (Energy Research and Development Administration, a precursor to the DOE), nuclear engineers and mathematicians from the NRC, who were familiar with the recently deve
Data Loading...
