Tadahiko Suzuta

Development of Moisture Separator With High Performance of Steam Generator

A steam generator of PWR plant has moisture separators with function to separate water from two-phase flow of water and steam. Recently, corresponding to the request for power uprating of current and/or future plants with large thermal capacity, development of high performance moisture separator, which can deal with the increasing steam flow rate, has been required. Therefore, MHI has developed the moisture separator with high performance (J Model) by conducting a verification test under actual plant operating conditions (high pressure and high temperature). The developed separator’s main features are: swirl vane hub with a small diameter, horizontal slits at riser barrel, and slots with lips at the downcomer barrel. Based on the combination of the high pressure test results and thermal hydraulic analyses, value of moisture carry over (MCO) at SG outlet was evaluated. The evaluation resulted in the MCO value of less than 0.01% (our target value: 0.1%).Copyright

Study on the Effect of the Cavity Flow on the Natural Circulation in the Piping System with a Closed End

It is necessary to evaluate the temperature of a valve when a specification of a valve is decided in a branch pipe connected to a main loop with a constant flow. The evaluation methods have been established in the case of the horizontal branch pipe below the main loop, and the method is based on the stable thermal stratification. However, a thermal stratification behavior is unstable in the horizontal branch pipe above the main loop because the cold fluid due to a heat removal in the branch pipe is higher than the hot fluid carried into the branch pipe by a cavity flow. The natural circulation is caused by the temperature and height difference between the main loop and the branch pipe. Since the interaction between the cavity flow and the natural circulation affects the natural circulation, it is not clear whether the developed method is applied to the phenomenon or not. Therefore, the experiments were carried out in order to understand the effect of the cavity flow on the natural circulation. From the results, the behavior of the natural circulation depends on the intersity of the cavity flow. In addition, the applicability of the CFD to the phenomenon under the cavity flow was verified only for the weak cavity flow such as 0.07 m/s of the average fluid velocity in the main loop.