Nuclear powerBenchmark data set validates global nuclear reactor codes

Published 24 March 2016

Nearly 100 commercial nuclear reactors supply one-fifth of America’s energy. For each fuel rod in a reactor assembly, only 5 percent of its energy is consumed before fission can no longer be sustained efficiently for power production and the fuel assembly must be replaced. Power plants currently store the used fuel on-site. Information on the composition of the used fuel is essential for the design of safe storage, transportation, and final repository facilities and for inspection and verification to safeguard nuclear materials. Improved accuracy in prediction of the spent fuel isotopic composition leads to increased efficiency in the facility designs and higher confidence in the safeguard protocols.

Nearly 100 commercial nuclear reactors supply one-fifth of America’s energy. For each fuel rod in a reactor assembly, only 5 percent of its energy is consumed before fission can no longer be sustained efficiently for power production and the fuel assembly must be replaced. Power plants currently store the used fuel on-site. Information on the composition of the used fuel is essential for the design of safe storage, transportation, and final repository facilities and for inspection and verification to safeguard nuclear materials. Improved accuracy in prediction of the spent fuel isotopic composition leads to increased efficiency in the facility designs and higher confidence in the safeguard protocols.   

To demonstrate the accuracy of computer codes for predicting the isotopic composition of used nuclear fuel and other radioactive waste, researchers in the United States have conducted experimental studies aimed at accurately characterizing used nuclear fuel to ensure it can be stored safely and efficiently. Using radiochemical techniques, they have analyzed the isotopic contents of fuel rods from many commercial nuclear reactors and compared the results with calculated values from nuclear reactor fuel simulation codes. One of the cornerstone validation data sets includes fuel from the Three Mile Island Unit 1 (TMI-1) reactor that was measured between 1998 and 2000.

ORNL reports that in 2012, Catherine Romano of the Department of Energy’s Oak Ridge National Laboratory (ORNL) identified a need to better understand the relationship between the isotopic content of used fuel as measured using nondestructive analysis (NDA) and the actual isotopic content of the fuel to strengthen nuclear safeguards. Romano is a member of ORNL’s Nuclear Material Detection and Characterization group and principal investigator of a National Nuclear Security Administration project through the Office of Defense Nuclear Nonproliferation to develop NDA methods for used fuel. In 2013, members of the project team at ORNL re-analyzed two fuel rods from the TMI-1 reactor that were previously used in a cornerstone data set. They used NDA measurements (from neutron and gamma ray detectors) and improved destructive radiochemical assay methods (of samples from dissolved fuel rods) to provide very accurate correlations between the NDA signals and measured isotopic concentrations. In addition, they compared the measured concentrations to simulations and cross-checked results against the earlier measurements.