Nuclear Fission Reactor Thermal-Hydraulics (NUFRETH) - UKAEA

Lead Research Organisation: CCFE/UKAEA
Department Name: Culham Centre for Fusion Energy

Abstract

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Publications

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Description The Nuclear Fission Reactor Thermal-Hydraulics (NUFRETH) grant sought to establish a testing facility for large-scale, high pressure and high temperature (15.5 MPa, 345 °C) nuclear thermal hydraulics and heat transfer in water-cooled components with high resolution diagnostics. The project was funded through the EPSRC's National Nuclear User (NNUF) programme and commenced in October 2021. The facility is intended to be strategically key in offering capabilities to both the fission and fusion communities to enhance knowledge transfer through an open-access facility for academia and industry.

Early in the project, challenges to the delivery of the planned capability within the grant timescales and budget were encountered that required a change in scope. In particular, significant inflation and extended component lead times were encountered, caused by labour shortages and the release of pent-up demand after the COVID pandemic, alongside a lack of availability of raw materials due to the conflict in eastern Europe and supply issues from China. As a result, the scope of work was reduced, in agreement with EPSRC, to cover the Concept Design, Interim Preliminary Design and selected de-risking activities for the proposed future facility. No capital purchasing was undertaken as a deliberate decision to avoid redundant spend on components that would yield only a partial system.

As a result of these challenges, the grant has delivered the following outcomes that have advanced the design of the facility:
• Facility Use Case and Requirements Documentation: Definition of system operating parameters and phenomena of interest for range of users as outlined in original grant proposal. Formalisation of stakeholder and system requirements to meet desired use cases.
• Concept Design: Initial concept design of system, including primary flow loop functional basis, system layout, and hazard identification.
• Interim Preliminary Design: Matured system design to increase confidence in achieving system requirements, including design description, general arrangement drawings, flow sheets, concept of operations, preliminary component identification, and safety analysis.
• Equipment Specifications: Draft equipment specifications for long lead-time items, including main circulation pump and system Initial Test Unit.
• Future Engineering Timeline and System Cost Evaluation: Definition of the remaining engineering phases, with timeline estimations, and detailed cost breakdown for remaining resource and equipment spend required to reach full facility realisation.

These deliverables will be invaluable in taking forward the facility to full realisation through other funding mechanisms.

Within the facility design, a number of technical challenges not envisaged at the initial proposal stage have been identified. While solutions for these are present within the current design, additional complexity and equipment cost are the resultant trade-off. Therefore, in order to maintain a reasonable balance against the facility research goals, a further set of outcomes of the grant are a number of recommendations for rationalisation in future stages of the facility realisation. This includes:
• Identification of potential system modifications and trade-off with use cases that would enable lower complexity, lower cost solutions to be found.
• Concept design of a "Demonstration Test Unit" for utilisation on smaller existing facilities at UKAEA to act as a de-risking precursor for some of the key diagnostic systems.
• Compilation of a Lessons Learnt Register to enable knowledge transfer of technical and project risks and issues to the future delivery team.
Exploitation Route The project has been extensively documented and brought to a controlled close that allows the further development of the envisaged facility to be pursued at a later date, eventually leading to its full realisation. The key steps leading to this outcome will be:
• System Design Review and Optimisation: Review of changes to the research landscape in the interim period since the original proposal and identification of relevant potential system modifications to reduce cost and complexity.
• Detailed Design: Finalisation of the system design to a point sufficient to enable procurement of all equipment and installation on site.
• Facility Manufacture & Build: Procurement, manufacture, delivery, and installation of system on-site.
• Commissioning & Acceptance: Commissioning of system and handover to operations.

The requirements for these steps have been captured within the existing project outcomes, including detailed breakdowns of timeline and cost estimations. Additional intermediate steps to take forward the outcomes of the completed work without requiring build of the full system are possible through the development of the "Demonstration Test Unit", which would provide a lower cost de-risking of key diagnostic techniques alongside achievement of a valuable subset of the original research goals.
Sectors Energy