The Halden Reactor Project (HRP) relies on extensive use of in-core instrumentation for both fuel and material testing in the Halden Boiling Water Reactor (HBWR). Separate loop systems have been installed in the reactor to simulate boiling water reactor and pressurized water reactor conditions. Reliable in-core instrumentation has been developed for measuring all key parameters both for fuel and material such as fission gas release, fuel temperature, fuel swelling/densification, cladding creep, etc. HRP has a fully equipped workshop for instrument production, and all our instruments are developed and made in-house. Instruments based upon the in-core linear variable differential transformer (LVDT) have been developed by HRP, such as the fuel pressure sensor, fuel rod expansion thermometer, fuel swelling, and cladding elongation. A special diameter gauge based upon the LVDT principle has also been developed to measure diametric changes of the fuel rods.

In order to characterize the irradiation conditions (both nuclear and chemical), the HRP has developed the miniaturized gamma thermometer and various types of electrochemical potential sensors. In addition, different types of self-powered neutron detectors have been developed. Ongoing development of in-core instrumentation and measurement techniques focuses on high-temperature conditions and new methods for crack detection and corrosion of fuel cladding materials. Another topic under development is online corrosion detection by means of electrochemical impedance spectroscopy. Initial in-core measurements have been performed at HRP.