Primary Cooling System
The primary cooling system is mainly composed of two heat exchangers, a helium-helium intermediate heat exchanger (IHX) and a primary pressurized water cooler (PPWC), four primary gas circulators (PGCs) and a concentric hot gas duct.
The HTTR has two operation modes. One is parallel loaded operation, in which the IHX and the PPWC are used. The amount of heat removal at full power operation is 10 and 20MW for the IHX and the PPWC, respectively. The other is single loaded operation, in which the reactor is cooled only by the PPWC of 30MW.
The IHX is operated at the highest temperature in the world. The heat transfer tubes of the IHX are made of Hastelloy XR, newly developed by JAERI. The cutaway view and the specification of the IHX are shown below.