Decoding Nuclear Data: Are We Sure About Our Reactors' Blueprints?

The EXFOR database is a compilation of experimental nuclear reaction data. It encompasses various types of reactions, including neutron reactions, threshold reactions, isomeric transitions, angular distributions, and data from resonance regions. This database is crucial for understanding nuclear processes because it provides the relationship between incident energy (or angle) and the corresponding cross-section, which indicates the probability of neutron interaction. Scientists use EXFOR data to validate and improve the accuracy of nuclear reaction models and simulations, which are essential for reactor design, nuclear safety assessments, and nuclear waste management.

The Nuclear Energy Agency (NEA) Data Bank plays a crucial role in ensuring the accuracy and reliability of nuclear reaction data. It compiles and updates data from various sources, making it accessible to scientists and engineers worldwide. The NEA Data Bank collaborates with organizations like the Société de Calcul Mathématique to develop statistical methods for cross-checking the consistency between experimental data from the EXFOR database and evaluated nuclear data libraries such as ENDF/B-VII.1, JEFF-3.2, JENDL-4.0, and TENDL-2014. These efforts help identify suspicious data and potential flaws, ultimately improving the quality and reliability of nuclear data used in numerous applications.

A key difference lies in the nature of the data. In EXFOR, data consists of discrete points derived from experimental measurements, representing the relationship between incident energy or angle and the cross-section. These points come with uncertainties. In contrast, evaluated nuclear data libraries like ENDF provide continuous functions that model nuclear reactions. While ENDF data primarily provides cross-section uncertainty, both EXFOR and ENDF's uncertainty are very important during comparison. Both types of data are essential, with EXFOR serving as a source of experimental validation for the models used in evaluated libraries.

The accuracy of nuclear reaction data is vital for nuclear reactor safety because these data directly influence reactor design, safety assessments, and operational efficiency. Accurate data from sources like EXFOR and ENDF helps in predicting how neutrons interact with reactor materials, which is essential for controlling the nuclear chain reaction. Incorrect data could lead to inaccurate predictions of reactor behavior, potentially affecting the reactor's ability to control the reaction or leading to unexpected conditions. Furthermore, precise data is necessary for nuclear waste management, ensuring the safe handling and storage of radioactive materials.

Statistical methods are employed to cross-check the consistency between experimental data in EXFOR and evaluated nuclear data libraries like ENDF/B-VII.1, JEFF-3.2, JENDL-4.0, and TENDL-2014. These methods involve comparing the experimental data points from EXFOR with the models and calculations from the evaluated libraries. By developing a consistency ranking for each EXFOR entry, researchers can identify suspicious data or potential discrepancies. This helps in pinpointing areas where the evaluated data files might need refinement, leading to more accurate and reliable nuclear reaction data. The process focuses on identifying outliers and evaluating data, specifically in the complex resonance energy ranges, and aims to enhance the overall quality of nuclear data used in nuclear technology.