NEA report calls for more accurate data on SNF heat decay

The OECD Nuclear Energy Agency has issued a report calling for more-detailed information on tracking the decay heat of spent nuclear fuel from light water reactors. According to the NEA, the report highlights the increasing importance of accurate decay heat estimations due to evolving fuel characteristics, including higher initial fuel enrichment, increased burn-up rates, and extended reactor cycle lengths.

The report, Summary of the NEA Assessment on Spent Nuclear Fuel Decay Heat for Light Water Reactors, summarizes the findings of a subgroup of the NEA's Working Party on Nuclear Criticality Safety (WPNCS), which ran from January 2022 to January 2024.

The WPNCS subgroup examined experimental methods, computational models, and uncertainties in decay heat estimation and emphasized the need for new calorimetric measurements due to a lack of data for fuel types such as mixed oxide (MOX), water-water energetic reactor (VVER), and CANDU.

The main findings of the WPNCS are reported in the extended article, "An Introduction to Spent Nuclear Fuel Decay Heat for Light Water Reactors: A Review from the NEA WPNCS," published in the EPJ Nuclear Sciences and Technologies Journal.

Recommendations: As the precise knowledge of the decay heat of the various fuel types affects the safety and economy of the back end of the fuel cycle, the NEA report recommends the following:

• Extend the current experimental database to include evolving fuel types.
• Improve the theoretical understanding and nuclear data surrounding the calculation of decay heat.
• Improve the understanding of best-estimate calculations and conservative estimations.
• Improve the understanding of biases and uncertainties.

According to the NEA, the list of recommendations is not comprehensive but represents the main priorities of the WPNCS subgroup.

The NEA operates within the framework of the Organization for Economic Co-operation and Development and is located just outside Paris, France.