In order to satisfy the IAEA safety requirement, the conservative design of Nuclear Power Plant’s (NPP) cooling chain is applied by consideration of maximum heat load and high ultimate heat sink temperature. However, for the freezing site, combined with the low heat load in cooling chain, the low service water temperature in winter may possibly causes the unavailability of cooling chain.
This paper is mainly focused on the once-through cooling chain design at freezing site. By analyzing the thoughts and applicability of different kinds of cooling chain design for anti-freezing consideration, one solution called “SEC thermal discharge reflux” is proposed. The solution has already been approved by National Nuclear Safety Administration (NNSA) in China, and applied in one of the northern China NPP.
Comparing with the traditional anti-freezing designs, the solution has its feature as “Reactor low power operation”, “Reactor first time start-up” and “Change-over of RRI/SEC trains in winter”. Besides, it is also able to prevent the heat exchanger of RRI side from icing and SEC side from sediment deposition and mussel growth. The solution is applicable for once-through cooling type NPP, and is not restricted by the reactor type.
