Modeling and simulation of a natural circulation water-tube steam boiler

In the present work, the overall behavior of a steam boiler is investigated using RELAP5/MOD3.2 system code at three different operating loads. Main thermal-hydraulic parameters are analyzed at steady-states corresponding to 60%, 100% and 110% of the boiler nominal load. RELAP5 system code is widely used in the design and safety analysis of nuclear reactor installations as well as for conventional facilities in recent years. The steam boiler studied herein is a water-tube natural circulation type used in a natural gas liquefaction complex for superheated steam production purposes. A complete model of the steam boiler has been developed for the RELAP5 code. This model, that is also suitable for transient simulation, has been used for the reconstruction of three steady-state tests in order to assess the steam boiler safety features during the operation. The model includes all parts that can eventually influence the safety of the steam boiler particularly the control and regulation system. A qualification process has been undertaken in the aim to verify the capability of the model to reproduce the main parameters of the steam boiler. This process revealed that RELAP5 system code results matches significantly the experimental data of the steam boiler. Finally, it should be mentioned that the results obtained so far are very encouraging for studying the general behavior of the steam boiler in transient operating conditions, as well as for evaluating its safety under hypothetical scenarios.This step will be undertaken in the near future and will allow the check of the code capability to simulate thermal-hydraulic phenomena occurring in the steam boiler during transient operation.