Patent Number: 
Section: claims

1. A basket comprising:a square pipe assembly having a plurality of square pipes assembled in a staggered arrangement, wherein each of the plurality of square pipes comprises:four walls and four corners arranged so as to form a square cross section, the four walls including neutron-absorbing material and having a thickness capable of preventing spent fuel inserted therein from reaching criticality and capable of ensuring a predetermined strength at a time of falling down, wherein a cell for housing a spent fuel aggregate is formed in a space defined by walls of the square pipes;a connecting section formed on each of the four corners, at which diagonally adjacent square pipes are contacted with each other, wherein the connecting section is formed into a terrace shape having a plurality of steps, and the steps of the terrace shape are formed to butt against the steps of adjacent square pipes when the square pipes are assembled in a staggered arrangement; anda square pipe receiver placed between adjacent square pipes located on the outermost circumference of the square pipe assembly. 2. The basket according to claim 1, further comprising:a fastener which fastens the outermost square pipes of the square pipe assembly; anda spacer block formed to fit to the inner shape of the spent fuel container. 3. A spent fuel housing container comprising:a basket according to claim 1 formed into a lattice shape as a whole by combining a plurality of square pipes with each other in a staggered arrangement and inserted to the spent fuel housing container to be fitted to cavity inner shape of the spent fuel housing container so that a spent fuel aggregate is housed inside the lattice. 4. A basket comprising:a square pipe assembly having a plurality of square pipes assembled in a staggered arrangement, wherein each of the plurality of square pipes comprises:four walls and four corners arranged so as to form a square cross section, the four walls including neutron-absorbing material and having a thickness capable of preventing spent fuel inserted therein from reaching criticality and capable of ensuring a predetermined strength at a time of falling down, wherein a cell for housing a spent fuel aggregate is formed in a space defined by walls of the square pipes;a connecting section formed on each of the four corners, at which diagonally adjacent square pipes are contacted with each other, wherein the connecting section is formed into a terrace shape having at least one step, and the step of the terrace shape is formed to butt against the step of adjacent square pipes when the square pipes are assembled in a staggered arrangement; anda square pipe receiver placed between adjacent square pipes located on the outermost circumference of the square pipe assembly. 5. A spent fuel housing container comprising:a basket according to claim 4 formed into a lattice shape as a whole by combining a plurality of square pipes with each other in a staggered arrangement and inserted to the spent fuel housing container to be fitted to cavity inner shape of the spent fuel housing container so that a spent fuel aggregate is housed inside the lattice. 6. The spent fuel housing container according to claim 5, including portions where no side faces are present along the outer circumference of the basket, wherein said square pipe receiver is provided at the portions where there are no side faces along the outer circumference of the basket. 7. The spent fuel housing container according to claim 6, wherein said square pipe receiver is comprised by a convex portion of the spent fuel housing container.