In next century, a great deal of energy is used for pablic life in this coutry. This paper describes two new very small reactors for thermal heat supply to pulic use, such as air-conditioning and hot water. These reactor are characterized by the high safety, the long life fuel and the excellent cost performance. The reactor is an integrated and natural circulated PWR with passive safety systems. The reactor is designed with simple structure and enough isolation efficiency to be installed in the deep underground or settled on the base floor of a office building in a large city.