Thermal-hydraulic Research Of Accelerator Driven System (ADS) Principle Verification Facility

Based on the China Advanced Research Reactor (CARR), this article firstly use the spent fuels of CARR to form the core of ADS principle verification facility, whose center space(four fuel assemblies) is reserved to put spallation target. Besides it puts forward the whole primary loop system design and main parameters of ADS principle verification facility. Due to being operated under sub-critical level, ADS principle verification facility need the external source neutrons from target reaction to maintain steady-state, so it is a must to modify the point reactor model of RELAP5 procedure, to add to the external source and to form the relationship between it and the accelerator power. Then to meet the requirement between the modified procedure and the ADS sub-critical reactor, it is a necessary to verify the procedure.Secondly, the article completes the entire system modeling and sub-channel modeling of ADS principle verification facility. The system modeling includes the following sub-components model: the reactor core, reactor pool, the decay tank system, plate heat exchanger and the main pump, etc; for the sub-channel modeling, it first determines the radial power distribution of principle verification facility, then the fuel assembly of the relatively largest power becomes the object of sub-channel modeling (the fuel assembly most near to the target). Finally, the article finishes the systemic and sub-channel safety analysis of ADS principle verification facility. To debug steady state is carried out using the RELAP5 procedure for the system modeling. Then safety analysis is completed in the transient and accident conditions which ADs principle verification facility may involve, including spurious proton beam trip, unprotected double external source transient, unprotected transient over-power, the loss of flow transient, the loss of heat sink transient and small-break transient in cold leg. The results show that, the temperature of fuel and cladding is well below the melting temperature; the coolant is under-heating without heat transfer deterioration; the natural circulation is enough to take away reactor core decay heat. In addition, ADS itself is operating under the sub-critical level, so there is adequate safety. And the accelerator proton beam is cut off quickly in serious transient accidents, the reactor is run in a sufficient subcritical level (-3000pcm). This article also shows sensitivity analysis of ADS principle verification facility on different keff, and the conclusion is arrived at that keff=0.97 is more reasonable from both safety and economic considerations. COBRA procedure is used to debug steady state of sub-channel model. Because of without transverse mixing between the sub-channels, the RELAP5 procedure can be used to verify steady-state results. In the end, some transient accidents are analyzed in terms of the sub-channel model, which include spurious proton beam trip, double external source transient and the loss of coolant accident. Among all the transients, the maximum temperature of fuel and cladding is less than the melting temperature, and the coolant temperature is unsaturated. The entire system is safe. The design of principle verification facility could provide the platform of solving ADS key issue and engineering design.