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2025 annual assessments out for U.S. reactors
The Nuclear Regulatory Commission has released its 2025 annual performance assessments of the country’s 95 operating commercial nuclear reactors. And of the 95 reactors, all but five earned the highest marks.
Nuclear power plant assessments can fall under one of five categories: Licensee Response, Regulatory Response, Degraded Cornerstone, Degraded Performance, and Unacceptable Performance. Ninety reactors fell under Licensee Response, the highest performance category in safety and security. Plants that achieve this level of performance are subject to a Reactor Oversight Process (ROP) baseline inspection.
Ross Pivovar, Ole Wieckhorst
Nuclear Technology | Volume 205 | Number 7 | July 2019 | Pages 945-950
Regular Technical Paper | doi.org/10.1080/00295450.2018.1548220
Articles are hosted by Taylor and Francis Online.
All licensable critical heat flux (CHF) correlations/regressions models must determine and demonstrate a “design limit” that bounds the CHF correlation predicted/measured residuals via a 95/95 tolerance limit. This is a quick and straightforward calculation when the residuals are well behaved, exhibiting no trends and no heteroscedasticity. However, as models become increasingly complex and as required parameter ranges become more extended, the likelihood of nonconservative subregions increases. A suggested solution from the open literature is the overly conservative approach of basing the design limit on the subregion with the largest variance. This approach unavoidably overly constrains the overall regression model and often is too conservative for subregions due to a loss in degrees of freedom. Quantile regressions alleviate these issues by smoothly varying the design limit based on covariates and adapting to each subregion. Thus, a quantile regression achieves the objective of appropriately bounding all subregions without overly biasing the overall regression model.