Transient Analyses of Main Steam Line Break Accident for High-Power Passive Reactor

Abstract

Passive reactor is quite different from traditional “two generation” nuclear power plants in the world at present. The primary system of passive nuclear power plant is modeled using RELAP5/MOD 3.3 code, and the transient thermal hydraulic characteristics are analyzed under the accident sequence of main steam line break (MSLB). DNBR of core is calculated by VIPRE code. Break spectrum is summarized as: When the break size is less than 0.058 m2, the reactor will not shut down; when the break size is between 0.059 and 0.105 m2, the reactor will shut down by overpower Δ T reactor trip; and when the break size is between 0.106 and 0.15 m2, the reactor will shut down by the steam pipe low-pressure injection signal. And the limited condition is 0.105 m2. The results of the limited condition show that the core heat flux, reactor coolant system (RCS) pressure and temperature fluctuate by time. The minimum value of the DNBR is 1.914, greater than limited value 1.45. The DNB design basis is met for the steam system piping failure event. DNB of a MSLB is not precluded by the criteria. The preceding result shows that no DNB exists for the main steam line rupture.