The China Institute of Atomic Energy (CIAE) has recently conducted the simulation of a passive heat removal system for fast nuclear reactors. Residual heat removal systems are designed to dissipate the decay heat produced by a reactor even after the nuclear chain reaction is stopped. The systems are necessary to prevent fuel from overheating and causing a meltdown.
“This is the first proof-of-principle test in China for a new passive residual heat removal technology for integral fast reactors,” the institute said. Integral fast reactors use liquid metal as a coolant, typically sodium as part of a closed-loop fuel cycle in which the used fuel is reprocessed within the same facility as the reactor.
The nuclear reactor core waste heat removal capability is essential for the basic reactor safety, said CIAE. “The passive removal of core waste heat by the natural cyclic flow of coolant is an important manifestation of the inherent safety performance of fast reactors. How to effectively implement and validate natural cycles in fast reactors is currently a hot and difficult issue internationally.”
Recently, the integrated waste heat removal principal verification test was successfully completed for the Integrated Closed Cycle Fast Reactor Nuclear Energy System (Integral Fast Reactor) project undertaken by the Institute of Reactor Engineering Technology of the Atomic Energy Agency (AEA). The test results were reviewed by experts from Tsinghua University, Xi’an Jiaotong University, North China Electric Power University, Chongqing University and others.
“This is the first domestic proof-of-principle test of a new type of passive waste heat removal technology for fast reactors, marking an important breakthrough in the research on key technologies of integrated fast reactors and providing a strong guarantee for promoting the design and development of integrated fast reactors,” said CIAE.
In order to solve the problem of natural circulation, the AEA uses a new type of passive waste heat derivation technology in the design of integrated fast reactors, which can effectively and reliably carry away core waste heat without relying on the action of any active equipment.
However, due to the large amount of equipment and complex structure in the reactor, it was difficult to determine the working mechanism of the new core waste heat export system, leading to uncertainty about the reactor design.
In order to more effectively support reactor design, improve technology maturity, and ensure reactor safety, the reactor thermal and hydraulic research team at the AEA developed test simulation technology for the fast reactor natural cycle and new passive waste heat export system.
The integrated fast reactor simulation test device is the first monolithic transient test device for an integrated fast reactor. It can simulate multiple key physical parameters in the process of removing waste heat from normal operation of the reactor to shutdown. It is an important platform for examining the new type of inactive waste heat removal for integrated fast reactors. It is expected to play a key role in the design and development of other fast reactors.
CIAE said that by fully understanding the coolant behaviour, key phenomena and natural cycle establishment mechanisms of the integrated fast reactor from normal operation to passive waste heat removal, the AEA has fully grasped the technical principles of the new passive waste heat derivation system, and the key data obtained can provide important support for reactor engineering design.
