High-fidelity models are computationally intensive to work with in many-query applications, such as the design process of small modular reactors. A reduced order model of the high-fidelity model can still accurately determine the quantities of interest with only a fraction of the computational cost, and thus can potentially solve the aforementioned problem. However, reducing a high-fidelity model of a small modular reactor is complicated due to the large number of parameters involved in nuclear reactor models, as that leads to an exponentially increasing parameter space needed to be surveyed.

Disregarding the parameters with the smallest impact on the output and thereby reducing the total number of variables can limit the parameter space, and thus speed up the model reduction at the cost of some accuracy. Perturbation theory utilizes the benefits of adjoint theory to efficiently determine sensitivities of responses to all the variables in the model, which allows one to find the influence on the output of the different variables without the need for evaluating them all repeatedly. It is then possible to apply a reduced order modeling technique such as proper orthogonal decomposition to determine and select only the most important eigenmodes of the high-fidelity model and build a reduced model.

This approach is applied to three different neutronics model of the U-Battery, varying in complexity. The presented method has shown to alleviate computational cost significantly for all examined reduced models. However, the upfront cost of building the reduced models by sampling the high-fidelity models has been considerable, especially when evaluating the resulting accuracy of the reduced models. A proper selection of the proper orthogonal decomposition tolerances must be made to ensure sufficient accuracy and to prevent oversampling. Nonetheless, combining proper orthogonal decomposition with perturbation theory showed to be a promising way of selecting only a few parameters for participation in the building of reduced order models while minimizing the loss of accuracy compared to the high-fidelity model.

In this thesis, a new methodology called the adjoint method is developed to select an optimal set of beam angles and beam weights in external beam radiotherapy. The Linear Boltzmann Transport Equation is specifically adjusted for proton transport and forms the Fokker-Planck approximation. The Fokker-Planck approximation models proton transport. Only the continuous slowing down operator, the straggling operator and a source are considered in the approximation. Numerical analysis is performed to solve the Fokker-Planck approximation. The discretization of the energy domain is done with the Discontinuous Galerkin method, and ray-tracing of beams in the spatial domain is done with the Crank-Nicolson method. A minimum least squares objective function is introduced to find the optimal selection of beam angles. The gradient descent method is applied to find a local minimum of the objective function. The gradient is calculated by performing adjoint transport of protons. Adjoint transport is based on an adjoint source, which is changing every iteration based on the dose deposition. The dose deposition is computed using forward transport of protons and uses the newest optimization variables. This way, several iterations can be performed.

The Thorium Molten Salt Reactor is one of the technologies being investigated to offer large scale carbon-free energy production. Yet as it is a form of nuclear energy it is controversial, and TMSR research is underfunded. In an effort to combat the controversy, a communication strategy for TMSR research is developed. This communication strategy is focussed on Dutch governmental organisations and political parties. The central question in this thesis is: How could TMSR be communicated by nuclear scientists, in order to improve the quality of discussion about TMSR at the relevant governmental organisations in the Netherlands? This was researched creating an overview of all relevant governmental organisations and interviewing several of them. Several factors that influence the attitude were hereby questioned, such as their values as an organisation, the frame by which they view nuclear energy in general, their approach to climate change, and their focus in energy policy. The relevant governmental organisations were identified as: ministry of economic affairs and climate, the social economic council, PBL Netherlands Environmental Assessment Agency, and the political parties PvdA, VVD, D66, GL, and CDA. The consensus focussed Dutch political system, coupled with preference for a democratic approach to climate change, leads to a communication strategy based on negotiation. This negotiation must be done in a constructive way that acknowledges the needs of all attending parties. Thorium is explicitly not to be presented as a substitution to wind, solar, and the climate agreement, but as an addition to it. The creation of a Platform Energy Innovation as a discussion form is recommended. This platform is to facilitate discussion with all the above-mentioned organisations and several other supporting ones. The use of integrative negotiation has the potential to create the desired positive attitude without creating enemies and thereby secure a more stable future for TMSR research in the context of the Dutch energy transition.