(SATURN CDT) Prediction and Mitigation of Flow-Induced Vibration in Nuclear Thermowell Instrumentation for Current and Next-Generation Reactors

About the Project

Saturn_Nuclear_CDT

UoM_Nuclear

The Challenge

Temperature measurement is not glamorous — until it fails. In a nuclear power plant, a thermowell is the slender protective sheath that keeps a temperature sensor alive inside a pipe carrying coolant at 350°C, 150 bar, and flow velocities exceeding 10 m/s. It is a small component with an outsized safety role: without it, the reactor control and safety systems are blind.

Thermowells fail. On 8 December 1995, a thermowell fractured inside Japan's Monju fast breeder reactor. The fracture was caused by vortex-induced vibration — cyclic oscillations driven by fluid flowing past the device — and the consequences were severe: several hundred kilograms of molten sodium flooded the secondary cooling circuit, igniting a major fire. The reactor was shut down for fifteen years. Investigations revealed that the failure was not caused by the classical vortex shedding modes captured by design codes, but by symmetric in-line oscillations that existing standards simply did not account for.

Thirty years on, those standards have improved — but not enough. The current industry benchmark, ASME PTC 19.3 TW, was written for conventional cylindrical geometries in single-phase water flow. It does not adequately address suppression geometries, liquid metal coolants, two-phase flows, or the transient partially filled piping conditions encountered during reactor startup and shutdown. As the United Kingdom accelerates its small modular reactor (SMR) programme and extends the operational life of its existing pressurised water reactor fleet, this gap has become a documented safety-critical vulnerability.

This project will close it.

The Research

Working at the intersection of experimental fluid dynamics, computational mechanics, and nuclear engineering, you will develop and validate a parametric predictive framework for thermowell integrity across the full range of nuclear-relevant operating conditions.

The starting point is strong. The University of Liverpool and Endress+Hauser recently completed a collaborative experimental campaign investigating vortex-induced vibration on cylindrical and helicoidal thermowell geometries. The results were striking: helicoidal designs achieved greater than 90% reduction in vibration amplitude compared to standard cylinders. That campaign demonstrated proof-of-concept and established the experimental and industrial partnership on which this PhD is built. Your task is to go further — extending these findings to the extreme conditions of advanced reactor environments and transforming empirical observations into predictive engineering tools.

The project is structured around seven objectives:

• O1 — Couple industry-standard CFD and finite element solvers to simulate fluid-structure interaction (FSI) for thermowell geometries under nuclear operating conditions.
• O2 — Parametrise thermowell geometry (cylindrical, tapered, stepped, helicoidal) for integration with the FSI framework.
• O3 — Extend the FSI capability to nuclear-specific conditions: liquid sodium properties, two-phase coolant flows, and partially filled piping during transients.
• O4 — Develop a fatigue life prediction model — including a safety margin calculation toolbox — driven by static and harmonic fluid loads from FSI simulations, validated against thermowell failure data.
• O5 — Build a geometry optimiser that maximises fatigue life for a specified reactor operating envelope, enabling bespoke thermowell design.
• O6 — Conduct experimental validation using water and simulant fluids at Liverpool's Very Large Scale Pipe Flow (VLSPF) facility.
• O7 — Undertake industrial validation at Endress+Hauser test facilities and, subject to access agreements, at nuclear-sector partner sites.

The computational work will use commercial codes (ANSYS, STAR-CCM+) alongside open-source tools (OpenFOAM). Experimental work at the VLSPF facility — one of the largest university pipe flow installations in the UK — will involve particle image velocimetry, laser Doppler anemometry, accelerometry, and laser vibrometry. The result will be a validated, geometry-agnostic design toolbox directly applicable to reactor new-build and life extension programmes.

SATURN CDTs are defined by their breadth of preparation, and this project exemplifies that philosophy. You will develop simultaneously as a computational engineer, an experimentalist, and a nuclear professional.

On the computational side, you will build expertise in coupled CFD-FE simulation and parametric optimisation — skills that are increasingly central to digital engineering in the nuclear sector. On the experimental side, hands-on work at the VLSPF facility will develop your command of advanced flow and vibration measurement techniques, alongside a rigorous understanding of scaling laws and similitude essential for any nuclear experimental programme. The SATURN Boot Camp will provide foundational grounding in reactor systems, nuclear materials, coolant chemistry, and regulatory frameworks. Through the industrial partnership with Endress+Hauser, you will gain direct exposure to commercial R&D practice and technology transfer processes. Potential secondments to the National Nuclear Laboratory or Rolls-Royce SMR will further develop your professional network and sector awareness

Nuclear Boot Camp (Months 1 - 3)

The Bootcamp is based in Manchester. For any of our students based at partner institutions, SATURN can offer you accommodation in Manchester and cover the cost.

Eligibility

We are looking for a motivated graduate with a strong first degree (2:1 or above, or equivalent) in mechanical engineering, aerospace engineering, or a closely related discipline. A background in one or more of the following is advantageous: computational fluid dynamics, structural mechanics, experimental fluid dynamics, or signal processing. Prior knowledge of nuclear engineering is not required — SATURN provides that foundation. Please contact Dr Fichera at Sebastiano.fichera@liverpool.ac.uk

How to apply

Please complete the Enquiry Form to express your interest. We strongly recommend you contact the project supervisor after completing the form to speak to them about your suitability for the project.

Equality, diversity and inclusion

Equality, diversity and inclusion is fundamental to the success of The University of Manchester, and is at the heart of all of our activities. We know that diversity strengthens our research community, leading to enhanced research creativity, productivity and quality, and societal and economic impact.

We actively encourage applicants from diverse career paths and backgrounds and from all sections of the community, regardless of age, disability, ethnicity, gender, gender expression, sexual orientation and transgender status.

We also support applications from those returning from a career break or other roles. We consider offering flexible study arrangements (including part-time: 50%, 60% or 80%, depending on the project/funder).

Funding Notes

The EPSRC funded Studentship with the University of Liverpool and will cover full tuition fees at the Home student rate and a maintenance grant for 4 years, starting at a stipend of £26,000 pa. for 2026-2027.