| AP1000 is an advanced pressurized water reactor developed by Westinghouse based on AP600. The main feature of AP1000 is enhanced passive safety concept. China made the decision of the introduction of AP1000 in 2006. There are two kinds of loading patterns of AP1000: one is the traditional loading pattern, the other is the advanced loading pattern. The advanced loading pattern improves the economy of neutron and the reactivity of the core by using "low leakage loading" method, and extends the core life. AP1000 is recommended to use the advanced loading mode.Rod ejection accident (short for "REA") is one of the severe accidents which may result in the most serious consequences during nuclear reactor operation. It is helpful to understand the physical characteristics of the core and to verify the safety of the core, and provide the relevant methods for the follow-up safety review by studying REA. AP1000 advanced first core was taken as the research object in this paper, and a proper three-dimensional coupled neutronic and thermal-hydraulic model was established in which the REA tests and analysis was taken.Firstly, the thermal-hydraulic model of the core was established using the transient simulation of light water reactor coolant systems code RELAP5, in which the active area was established into two hydraulic models. The cross-sections of advanced loading assemblies were calculated one by one by SCALE , preparing for transporting into the neutronic model later. Secondly, three-dimensional neutronic model of the active area was established by PARCS which is a three-dimensional reactor core simulator developed by Purdue University.The coupling of RELAP5 and PARCS was done in the parallel virtual machine environment,thus the coupling model was established.The REA tests were taken both in hot full power (HFP) and hot zero power (HZP)conditions based on the coupling model. Control rod bank ejection test of chosen four locations was taken and the results of two different hydraulic models were compared, and two banks ejection test was taken too. The results showed that the AO bank ejection in the center was the most severe one and the peak nuclear power caused by it was the maximum in four locations,but both the fuel center temperature and the cladding temperature did not exceed the specified value. The temperature of single-channel model was lower than the multi-channel model, thus the Doppler effect was weaker. The integral rod worth of lower normalize temperature was bigger than the worth of higher normalize temperature in the same location. The inserted reactivity of two banks ejection was very great, and the primary loop could be impacted due to drastic changes of pressure, but peak temperature and peak pressure was still acceptable due to the outer-ring ejected location. The consequence of AO rod ejection in the center location was the most serious in the four locations in HZP without shutdown, but the temperature and the pressure results were still acceptable. The same two rods in HZP were chosen to take the double-rods ejection test as in HFP. Although the integral worth of the test was great, the consequence was still under control because of the reactor trip of high power, and the temperature and the pressure was still acceptable. |
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