André A.C. Santos

Performance of some operating parameters of a TRIGA research reactor in natural convective cooling

In order to study the safety aspects connected with the permanent increase of the maximum steady state power of the IPR-R1 TRIGA Reactor of the Nuclear Technology Development Centre (CDTN) at Belo Horizonte (Brazil), experimental measures were performed with the reactor working in power steps from ‘zero’ power up to 265 kW. The experiments were performed with the pool forced cooling system turned off. A number of parameters were measured in real-time such as fuel and water temperatures, radiation levels, reactivity and influence of cooling system. This paper summarises the behaviour of the operational parameters and presents some of the recent results obtained. Information on all aspects of reactor operation was displayed on the Data Acquisition System (DAS) shown the IPR-R1 real-time performance. The DAS was developed to monitor and record all operational parameters. Information displayed on the monitor was recorded on hard disk in a historical database.

Experimental Investigation and Computational Validation of Thermal Stratification in Piping Systems of PWR Reactors

One phase thermally stratified flow occurs in horizontal piping where two different layers of the same liquid flow separately without appreciable mixing due to the low velocities and difference in density (and temperature). This condition results in a varying temperature dis‐ tribution in the pipe wall and in an excessive differential expansion between the upper and lower parts of the pipe walls. This phenomenon can induce thermal fatigue in the piping system threatening its integrity. In some safety related piping systems of pressurized water reactors (PWR) plants, temperature differences of about 200 oC can be found in a narrow band around the hot and cold water interface. To assess potential piping damage due to thermal stratification, it is necessary to determine the transient temperature distributions in the pipe wall (Häfner, 2004) (Schuler and Herter, 2004).