Accidents of primary coolant loss, steam generator tube rupture, steam line break, feed water line break and total loss of electricity have been analyzed for safety evaluation of the MRX. Figure 3 shows typical results during LOCA obtained RELAP5/Mod2 calculation assuming the double ended guillotine break of 50mm dia. pipe occurred in the CV. Cooling by the EDRS, the CV water and the CffCS is taken into account, but the function of the RHRS is neglected. The maximum design values of pressure and water temperature in the CV are 4MPa and 200’C as mentioned in Table 1, and the allowable minimum water level in the RPV is 0.5m above the upper edge of the core, which is determined to keep core flooding taking into account of ship inclination and oscillation. Figure 3 shows that the maximum values of pressure and water temperature in the CV and the minimum water level in the RPV are І. ЗМРа, 140’C and 0.8m, respectively. These satisfy the design conditions sufficiently. Through these analyses, it has been proved that the passive safety features applied to the MRX have sufficient functions in the safety point of view.