Critical power experiments were carried out, and the critical power correlation for axially uniformly heated tight bundles has been derived based on the present experimental data and data sets measured by the Bettis Atomic Power Laboratory. The shape of the test section simulates the fuel assembly of the reduced-moderation water reactor (RMWR), which is a water-cooled breeder reactor with a core of the tight triangular fuel rod arrangement. The obtained correlation covers the following conditions: channel geometry (triangular arrangement bundle of 7 to 20 rods, 6.6 to 12.3 mm in rod diameter, 1.0- to 2.3-mm gap between rods, 1.37 to 1.8 m in heated length), mass velocity of 100 to 2500 kg/(m2s), inlet quality of -0.2 to 0, pressure of 2 to 8.5 MPa, and radial peaking factor of 0.98 to 1.5, which include uniform, center-peak, and liner transverse heat flux distribution data. An excellent agreement was obtained between the developed correlation and data (371 points) within an error of ±4.6%.