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Predicting and forecasting reactivity and flux using long short-term memory models in pebble bed reactors during run-in

Published: November 7, 2025 | arXiv ID: 2511.05118v1

By: Ian Kolaja , Ludovic Jantzen , Tatiana Siaraferas and more

BigTech Affiliations: University of California, Berkeley

Potential Business Impact:

Predicts how nuclear reactors will work safely.

Business Areas:
Nuclear Science and Engineering

Pebble bed reactor (PBR) operation presents unique advantages and challenges due to the ability to continuously change the fuel mixture and excess reactivity. Each operation parameter affects reactivity on a different timescale. For example, fuel insertion changes may take months to fully propagate, whereas control rod movements have immediate effects. In-core measurements are further limited by the high temperatures, intense neutron flux, and dynamic motion of the fuel bed. In this study, long short-term memory (LSTM) networks are trained to predict reactivity, flux profiles, and power profiles as functions of operating history and synthetic batch-level pebble measurements, such as discharge burnup distributions. The model's performance is evaluated using unseen temporal data, achieving an $R^2$ of 0.9914 on the testing set. The capability of the network to forecast reactivity responses to future operational changes is also examined, and its application for optimizing reactor running-in procedures is explored.

Country of Origin
🇺🇸 United States

Page Count
13 pages

Category
Electrical Engineering and Systems Science:
Systems and Control