Abstract: 5 MW Experimental low temperature nuclear heating reactor developed by theInstitute of Nuclear Energy Technology, Tsinghua University, has been put intooperation. This paper describes briefly the main design characteristics,including the integrated arrangement, dual pressure-containing vessel structure,hydraulic control rod drive system used in reactor structures first timein the world, natural circulation and the design provisions for protecting heatinggrid from radioactive contamination. These design measures greatly enhancethe inherent safety features, which are also presented in the paper.