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Conference Spotlight
Nuclear Energy Conference & Expo (NECX)
September 8–11, 2025
Atlanta, GA|Atlanta Marriott Marquis
Standards Program
The Standards Committee is responsible for the development and maintenance of voluntary consensus standards that address the design, analysis, and operation of components, systems, and facilities related to the application of nuclear science and technology. Find out What’s New, check out the Standards Store, or Get Involved today!
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Deep Space: The new frontier of radiation controls
In commercial nuclear power, there has always been a deliberate tension between the regulator and the utility owner. The regulator fundamentally exists to protect the worker, and the utility, to make a profit. It is a win-win balance.
From the U.S. nuclear industry has emerged a brilliantly successful occupational nuclear safety record—largely the result of an ALARA (as low as reasonably achievable) process that has driven exposure rates down to what only a decade ago would have been considered unthinkable. In the U.S. nuclear industry, the system has accomplished an excellent, nearly seamless process that succeeds to the benefit of both employee and utility owner.
D. Elbèze, D. van Houtte, E. Delchambre
Fusion Science and Technology | Volume 75 | Number 5 | July 2019 | Pages 405-411
Technical Paper | doi.org/10.1080/15361055.2019.1603534
Articles are hosted by Taylor and Francis Online.
In the Reliability, Availability, Maintainability, and Inspectability (RAMI) engineering approach used in nuclear fusion research, criticality identifies the failure modes that have the greatest impact on the availability of the studied system. Criticality is expressed as the product of the occurrence level with the severity level of failure modes. The analytical calculation shows that this formulation is equivalent to their availability provided that the duty cycle of basic functions is introduced to adjust the occurrence and the scales of occurrence and severity are homogeneous.
To consolidate the results obtained with a Reliability Block Diagram analysis, we performed a probabilistic study using an advanced Monte Carlo simulation code: the Primavera® Quantitative Schedule Risk Analysis. This method associates failure modes with conditional activities in a schedule and provides the density distribution of failures and tornado graphs to identify the highest criticality failures.
Statistical tests were performed for two operational systems, and we showed that the criticality evaluated with the RAMI approach was in good agreement with the results of the other methods. Thus, in many cases, the analytical formulas can be used during the Failure Mode, Effects, and Criticality Analysis to quickly assess availability by using a spreadsheet.