Improvement of the numerical method on underground containment of fission products in the hypothetical accident at underground nuclear power plant

As one of means to extend the siting nuclear power plant, the construction of underground nuclear power plant is now under study. The underground containment for the fission products in the accident can be expected on the safety in special measure. The existing numerical method, which simulates the movement of the fission products through the surrounding ground of the underground cavity in the hypothetical accident at underground nuclear power plant, is limited in the application and is still not satisfactory on the accuracy of the numerical calculation. Accordingly, the development of more useful analysis method has been necessary. The new analysis method with use of the artificial viscosity, the approximation of concentrated mass type and etc. has been developed to settle the problem on the above mentioned numerical analysis method. It has been satisfied that the calculated values by new numerical analysis method agree very much with theoretical values and the method can be calculated in any case of the analytical model with practical geographical features and radioactive fission products. Therefore, the numerical analysis method, which simulates the movement of the fission products through the surrounding ground of the cavity in the hypothetical accident at underground nuclear power plant, has been established. (author)