Introduction   To improve the utility of pump and motor in CCS system, it is necessary to evaluate the condition of pipes located in first bay of nuclear power station turbine plant.

    Method   For the convenience of calculatiion, different pipe conditions were evaluated with several proper assumptions. Mathematical modeling and fluid mechanic analysis were also applied in the evaluation.

    Result   Our evaluation indicates that CCS can still work safely even in the most unfavor assumption on the maximal flow of broken pipe.

    Conclusion   Our method shows correct and solid result in evalution and the method is expected to be applied in design of subsequent constructions in the future.