Study of Effective Isolation Technology of Main Feedwater

Abstract This paper presents an effective isolation technology of main feed water including three sets of main feed water isolation devices for some nuclear power plant, and then model and calculate the whole feed water system using the commercial software “PIPENET”, including feed water hammer simulation, calculating the possible conditions of different isolation valves closing including one valve closing, two valves closing and three valves closing. Besides the special design for hydropneumatic type isolation valve having two sets of actuators is to ensure the availability of hydropneumatic type isolation valve during losing of power. However, the closing time of the valve is within a range, including the normal closing time and the unusual closing time during losing of power, which should be considered and designed by water hammer simulating and accident analysis. The final closing time of hydropneumatic type isolation valve is 6–12s. The effective isolation technology resolves the effective isolation of main feed water, reduces the risk of temperature and pressure exceeding of containment, ensures the tightness of containment, prevents the releasing of the radioactive substance during the occurring of main steam pipe break (MSLB) plus safety shutdown earthquake (SSE). Besides, when the steam generator rupture occurring, it can prevent the overflow of steam generator, the isolated accidental steam generator will not release a large amount of radioactive substance to environment. In addition, when the feed water rupture occurring, the accidental steam generator can be isolated; when there is accident in the feed water control, the relevant feed water can be isolated and the steam generator will not be overflowed. The effective isolation technology has great significance for reliability operation and safe operation of nuclear power plant.