Today’s necessity- and goal to reduce carbon emissions in tandem with finite fossil resources and rising oil prices, demand for an alternative and cleaner energy source to power the world dredging fleet. In parallel, recent research in naval architecture iterates the potential role for nuclear-based propulsion on board of ’energy-intense’ merchant vessels (approx. 20 MWe+ installed power) [16][20][23]. Powering a (large) trailing suction hopper dredger (30.000m3+) by an on-board small modular nuclear reactor would cut direct greenhouse gas emissions by 100%.

The power demand on board of trailing suction hopper dredger is fluctuating continuously. A reactor is typically applied for supplying constant power. The objective of this thesis was to research the transient load capabilities of a nuclear-powered trailing suction hopper dredger.
First, for the on-board nuclear installation, a graphite-moderated high temperature gas reactor was opted for which is cooled by helium gas. This reactor type has a technology readiness level of 9 and small-modular-reactor concepts of this type are being developed. Both the open- and closed helium Brayton cycle concepts show greatest potential for power conversion. It was shown that the reactor, the heat exchangers and the turbomachinery play an important role in both the overall efficiency of operation and the transient load limits of the system as a whole.

Second, a thermodynamic model was built to be able to simulate the effects of different control mechanisms in realising load-following. Bypass- and compressor throttling control performed best and allowed the reactor to ramp down at lower rate, which is a favourable feature. For a 100% reduction in power output, the reactor would have to ramp down to 47% and 34% of nominal power respectively.

Third, it was investigated how the limitations in load-following would effect the operational profile of a HTGR-powered TSHD. The suggested closed helium Brayton cycle cannot perform adequate load following to the fluctuating demand of a conventional TSHD today without an auxiliary source of energy. When keeping reactor ramping rates below 10%/minute, a 25MWe HTGR-powered TSHD would see peaks in power imbalance up to 10 MW. However, a 3MWh ESS was considered to perform power take-in and power take-off. In presence of such auxiliary power source, the operational profile of a TSHD would not have to be changed.

Looking ahead, it is crucial to investigate the impact of repetitive power transients on the controllability and lifespan of both the reactor and other components within the power cycle. Additionally, a more in-depth study of the aerodynamic characteristics of the helium turbomachinery is necessary. Lastly, incorporating supplementary nuclear kinetics analysis could help validate the findings presented in this report.