[en] Systems transient-analysis codes can be expected to yield reasonably accurate results (order +-20% or so on system pressure) if carefully utilized and if the two-phase and transient-flow conditions are not severe. As the severity of the transient increases, the confidence that one may have in the results decreases. None of the existing codes is well assessed or verified for transient analysis, but all give qualitatively the same results, lending credence to their results. Users of these codes must be especially careful to initialize properly, must examine results with great concern for understanding the details in order to uncover anomalous behavior, and must, over everything, take great lengths to accurately model the plant controls which will in fact ultimately govern the transient