Evaluation of clab decay heat measurements from 2003 to 2021 under EPRI-SKB collaboration

Accurate estimation of decay heat for spent nuclear fuel is important for wet storage (spent fuel pool heat management), cask/canister loading campaigns (ensuring that temperature limits are met), dry storage system aging management, transportation, and eventual disposal. Clab decay heat measurements performed between 2003 and 2004 were published in 2006 and used across the globe for computer code validation purposes. Currently, Clab is the only facility in the world that performs full assembly decay heat measurements. Recently, EPRI and SKB entered into a collaborative agreement to evaluate and publish all Clab decay heat measurements performed between 2003 and 2021. The publicly available publication has not only extended the decay heat validation range significantly but has also improved characterization and evaluation of the measurements, including associated uncertainties. In this paper, an overview of Clab decay heat measurements and evaluation of the measurement uncertainties for the decay heat measurements performed between 2003 and 2021 are presented. Clab measurement uncertainty is re-evaluated to include previously unpublished calibration data, to assess the impact of data quality screening, and to review and revise certain prior conservative assumptions. The re-evaluation relies primarily on the accumulated population of Clab measured data. Finally, lessons learned and recommendations for future decay heat measurements are provided. • Decay heat validation range extended with high quality Clab measurements, including measurements that were publicly available before, that have low uncertainties. • Decay heat measurements with shorter cooling time and high decay heat are added. • Decay heat measurement uncertainty is re-evaluated and lower than 1 % (2σ) at high decay heat. • A list of screening criteria and lessons learned developed for future measurement campaigns.