The challenge
Nuclear energy will play an increasingly important role in supporting the UK’s goal to reach net zero emissions by 2050, and 2045 in Scotland. With predicted growth in this sector, there is a global need for high quality data to accurately model the next generation of nuclear reactor systems. Proper understanding of this data is key for the deployment of new reactors, as it ensures improved safety, sustainability, efficiency and cost.
All modern reactor design is based on complex modelling and nuclear modelling relies on the concept of a ‘neutron cross-section’ which reflects the likelihood of interaction between an incident neutron and a target nucleus. This determines the reactor energy-production rate and waste production rate for a given neutron density and a given mass of fission material, as well as allowing predictions for the performance of new reactor designs. This cross-section data can be used to give confidence (+/-10%) in the system modelling and resulting fuel compositions used.
This data requires precise measurements, which can be technically challenging to perform, as there are many experimental conditions that need to be satisfied and controlled simultaneously. Long measurement times are often required, significantly impacting measurement costs and contributing to data uncertainty.
The level of measurement capability required for these precise measurements and optimisation of nuclear data required collaboration between NPL, NNL and the University of Manchester (UoM).
The solution
NPL is a world-leader in well-characterised neutron fields. However, it did not have the instrumentation to perform fission studies. Acquiring and maintaining such instrumentation is challenging since it is unavailable commercially, and requires lengthy and expensive development.
The Advanced Fuel Cycle Programme (AFCP) promotes fuel cycle innovation to secure a net zero future by helping equip the UK with the right skills, technology and networks. It leverages cross-country collaboration and cutting-edge science to steer the direction of future energy systems. As part of the AFCP Nuclear Data project, NPL has partnered with the University of Manchester (UoM), a world-leading centre for fission studies and detector development, to bring a new approach to nuclear data collection and uncertainty reduction.
By combining both organisation’s resources and expertise, the project aims to:
- Prove the capability of UoM’s fission chamber to advance nuclear measurements
- Demonstrate NPL’s ability to measure Uranium 236/238 nuclear data.
The partnership provides UoM with access to the NPL neutron facility to test their detector and gives NPL the ability to use the detector for nuclear data measurement.
The impact
NPL’s unique combination of measurement capabilities improved the data measured. For example, NPL absolute cross-section measurements were performed and compared with relative measurements that were collected elsewhere. This enabled systematic errors in existing measurements to be highlighted, which can now be used to update nuclear data libraries.
Other key complimentary capabilities include radiochemistry and activity measurements, which are needed for manufacturing and characterising targets. This will ultimately reduce the uncertainty in nuclear data that the nuclear industry can rely upon.
The AFCP’s Nuclear Data project has encouraged several upgrades to NPL’s facility including an increased neutron fluence (or dose) and a smaller fluence uncertainty. This can potentially benefit the broader UK nuclear community.