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The safety analysis of an industrial installation is extensively based on modeling and simulation. However, the analysis of simulation using realistic computer codes like RELAP5/Mod3.2 will help understand thermal-hydraulic behavior of an installation during normal and accidental conditions. In a steam boiler operation, it is very important to evaluate numerous accident scenarios under real plant conditions. One of the main accidental transients is tube rupture of steam boiler. The main objective of this study consists toinvestigate the behavior of an industrial steam boiler installed in the complex of natural gas liquefaction (LNG) at Skikda in Algeria during feed water line break accident. A RELAP5 model was set up to simulate the entire system, the model represents all steam boiler components to be suitable for the analysis of the several accidents. The control and regulation systems are also considered. The model was qualified against the steam boiler data at steady-state conditions. As seen from the results, a good agreement was obtained. The transient simulation results show that the thermal-hydraulic code correctly predicts the behavior of the main steam boiler parameters and how the control system, when required, can successfully mitigate the accident.

The present paper consists of a numerical investigation carried out for primary break up analysis of a vertical water jet. Many parameters impact the flow development such as velocity, turbulence and nozzle shape. In this work, two types of nozzle geometries have been performed, the first is a capillary circular and the second is conical. The calculations have been performed using the CFD Code Fluent of ANSYS, considering laminar and turbulent flow regimes. While turbulence was modelled using RNG k-ε of RANS approach. The main results show that the jet evolves differently in the two considered nozzle geometries comparing the jet intact lengths, drop sizes and distance between successive drops. It is observed that the turbulence increases substantially the jet intact length and enables the jet breakup at the lower part of the water column. For the conical nozzle case, the jet instabilities grow quickly resulting a drop size in the same order of the jet diameter and an intact length larger in comparison with the circular nozzle case.

This study is a contribution for radiation dose calculations of a hypothetical accident of a 1 MW research reactor Triga Mark II using HotSpot code. A postulated accidental release of noble gases and halogens were considered. The total effective dose (TED) was estimated for 1 day and 50 years after release. The total damage of fuel element cladding with a maximum radioactivity was considered. The obtained results show minimal TED values at the beginning of the release and at a shorter distance from the source. The maximum calculation results are acceptable and below the recommended public dose limit., Ovo istraživanje doprinos je izračunima doze zračenja hipotetske nesreće istraživačkog reaktora Triga Mark II od 1 MW primjenom HotSpot koda. Razmatrano je slučajno oslobađanje plemenitih plinova i halogena. Određena je vrijednost ukupne učinkovite doze nakon 1 dana i nakon 50 godina. Razmatrano je ukupno oštećenje obloge dijela s maksimalnom radioaktivnošću. Dobiveni rezultati pokazuju minimalne vrijednosti ukupne učinkovite doze na početku ispuštanja i na manjoj udaljenosti od izvora. Maksimalni rezultati izračuna su prihvatljivi i ispod preporučenog doznog ograničenja.

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.