Nuclear powered ships must be safe from collisions at sea but, in event of a collision, the dangerous uncontrolled release of radioactive or toxic materials must be guarded against and prevented. For this purpose, we carried out a series of experiments with models of bow and side construction, and investigated the results. The following is a summary of the experimental studies carried out on the collision barrier and the important part it plays in protecting the reactor plant on board. 1. It is sufficient to compare the strength of the bow construction, when it strikes a solid wall, with that of the side construction, when it is struck by a solid bow, in order to compare the strength of a bow construction with that of a side construction at the point of collision. 2. A vessel with a raked bow is not so dangerous compared as a vessel with a vertical bow. 3. The deck plate will absorb a certain amount of energy ever after the shell has been penetrated. This amount can not be considered negligible. 4. About the impact loading effect, it is only necessary to correct the yielding point of the matelials by the strain rate. We must derive the more complete formulas for calculation of the energy absorbed by collision barriers by farther studing the effect of the entrance angle of striking vessels.