"Determination of electrical power to be supplied to LOBI heaters", University of Pisa Report, DCMN - NT 011(80), Pisa (I), June 1980

The document deals with the description of an analytical and numerical model to determine the electrical power to be supplied to hollow rods, available in the LOBI experimental simulator, in order to simulate the performance of the nuclear fuel. Hollow rods are easy to construct but have a thermal capacity much lower than the reference nuclear fuel rods. The difference becomes important in transient conditions. In those conditions electrical power must be controlled in order to reproduce the temperature transient expected on the surface of the nuclear fuel rods. A complex software was developed to determine the electrical power transient based on the inverse solution for transient conduction heat transfer, i.e. the Fourier equation. Reference conditions (surface temperature and heat flux) were calculated by the RELAP code for nuclear fuel in the expected experimental conditions and were transformed into electrical power to be supplied to LOBI heaters during the actual experimental conditions (obviously if the Relap prediction were wrong – to be demonstrated a posteriori – the calculated transient for electrical power resulted inconsistent with the occurring thermal-hydraulic conditions). The program was used in a number of experiments performed in LOBI. LOBI was a Pressurized Water Reactor (PWR) simulator installed in the EC center of Ispra Italy supported by EURATOM