ANALYSIS OF A CORE DISRUPTIVE ACCIDENT IN A LIQUID-METAL-COOLED FAST BREEDER REACTOR USING THE NEAR-CHARACTERISTIC METHOD

The pressure disturbance propagation through a weakly compressible med ium, bound by rigid structure as well as material interfaces, has an i mportant bearing on the safety analysis of liquid-metal-cooled fast br eeder reactors. The analyses have been carried out using numerical alg orithms based on Eulerian, Lagrangian, or mixed formulations. Even tho ugh the results obtained from these schemes compared well with the ben chmark experimental results, certain drawbacks, such as less accurate treatment of material interfaces in the Eulerian schemes and mesh dist ortion in the Lagrangian schemes, and so forth, remain. These drawback s may be overcome by using a method of characteristics in two dimensio ns known as the near-characteristic method to solve the problem. The r egion of interest is discretized into Eulerian grids, and the flow par ameters are obtained from the compatibility equations corresponding to the near characteristics generated from the gridpoints. The material interfaces are tracked explicitly, using the near-characteristic schem e. The scheme is used to analyze a typical core disruptive accident pr oblem, and the results are compared with experimental results as well as those obtained using two other numerical schemes. Good agreement is observed among the results; indeed, the one-dimensional problem of ex ploding wire phenomena and the two-dimensional problem of core disrupt ive accident analysis validate the effectiveness of the scheme. The fu ture extension of the present scheme will include fluid structure inte raction and complex internal structures.