A marked reduction in the pressure drop of cooling liquid through a grid spacer of a nuclear fuel assembly is attained by convexly contouring the upstream (usually the lower) edges of the grid members. Preferably, they are made streamlined or semicylindrical. This can be done by first beveling and then etching them, by directing a stream of mixture of abrasive and an organic polymer against them, or by traversing an electron or laser beam along them at a power and velocity such as to cause local melting. A lesser improvement is secured by beveling alone. A still further improvement can be obtained by also tapering the downstream (usually upper) edges.