Boundary element analysis of the geometric buckling of the solution fuel with a slant surface in a rectangular tank

The geometric buckling of the solution fuel with a slant surface in a rectangular tank has been investigated using the three-dimensional Boundary Element Method. In the case such that the surface with a level H is slanting in the direction of a side with length l of the bottom surface, the geometric buckling increases with the increase in the surface slant angle if the ratio H/l is larger than a threshold value, ∼0.5, and vice versa. If H/L>0.5, where L is the length of the longer side of the bottom surface, the geometric buckling increases with the increase in the surface slant angle, and this is valid independent of the length of the shorter side and the direction of the surface slant. For the tank with square bottom, the surface slant effect is independent from the direction of the slant. When the 280T slab tank having the bottom surface of 70cm x 28cm is used, the Static Experimental Critical Facility, STACY, is operated to be critical only for the solution level of more than 40cm. For this core shape, if the level H is higher than about 35cm, the value of the reactivity decreases in keeping with the surface slant. (author)