Accurate knowledge of the neutron flux distribution in a nuclear reactor has many tangible benefits. Perhaps the most important are the contributions to reactor safety. Detailed knowledge allows reactor operators to identify off-normal conditions quickly before they cause serious complications. Furthermore, reactor safety margins can be accurately quantified. As advanced reactor types are proposed, new sensor systems should be developed together with new algorithms for neutron flux reconstruction. This thesis develops neutron flux reconstruction methods for in-core sensors placed in HTRs. Sensor systems developed for current generation reactors cannot be used in HTRs. The high temperatures inside HTRs preclude the use of existing in-core sensors, and complex flux phenomena arising from the inner reflector and three-dimensional fuel block arrangements suggest that new flux reconstruction methods should be developed as well. Computer simulations were run to generate detailed in- core neutron flux distributions representative of HTRs. Next, this data was used to test two different flux reconstruction algorithms. It was found that the reconstruction algorithm based on the proper orthogonal decomposition performed better than the algorithm based on linear interpolation.