Accelerator Driven sub-critical System (ADS), which employs the high-energy proton beam generated by accelerator to bombard the target nucleus and generate spallation neutrons as external neutrons to drive and maintain the operation of its sub-critical reactor, is of great significance in nuclear waste treatment and disposal. As the instability of proton beam would affect the power level of the reactor and threaten the safety of ADS, Beam Trip (BT) and Beam OverPower (BOP) are commonly considered to be its two typical transient accidents. As for the sub-critical reactor, the Transient OverPower (TOP) is also one of typical transient accidents that should be considered, which is mainly caused by reactivity insertion under certain cases, such as SGTR (Steam Generator Tube Rupture) accident. For the subcritical reactors, the transient evolution behaviors are strongly affected by the subcriticality value. On the one hand, the subcriticality values of ADS design should take safety margin and power gain into consideration. On the other hand, the subcriticality value is variable with the burnup of reactors. So it is necessary to study the safety characteristics of the subcritical reactors under different subcriticality values, in this paper, the transient safety characteristics of a single channel for XADS under BT, BOP and TOP accidents of different subcriticality values were investigated by using MPC-LBE code.
As one of the Generation IV reactors, Lead-based Fast Reactor (LFR) has been considered to be great promising owing to its advantages in nuclear safety, sustainable development of nuclear energy and nuclear waste disposal. Owing to the excellent thermal expansion characteristics of Lead-based coolant materials, the primary cooling system of LFR can operate in natural circulation driven mode. The CFD (Computational Fluid Dynamics)-based thermal-hydraulics and safety analyses of nuclear reactors, especially liquid metal pool-type reactors have attracted great attentions in recent years. In this paper, the entire 3-D geometric model of a 10 MWth natural circulation driven LFR primary cooling system was established and simulated by ANSYS Fluent, in which the mesh was partitioned by utilizing structured meshing technology, and the porous medium model was utilized to fine the reactor core simulation. The results showed that the above LFR can operate safely in natural circulation mode, and has excellent natural circulation characteristics for the primary cooling system.
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