Fuel element for high temperature reactors

DETAILED DESCRIPTION We claim: 1.
A finished fuel element for high temperature reactors consisting of a block of structural graphite having bores therein filled with molded fuel compacts consisting of coated fuel particles embedded in the graphite matrix, said fuel element having good heat transfer compared to block graphite from the fuel compact and graphite matrix to the structural graphite, wherein the graphite molding powder for fabrication of the graphite matrix consists of a member of the group consisting of (1) natural graphite and up to 15% binder by weight and (2) a mixture of graphite powders consisting of natural graphite, electrographite being present and in an amount of not over 25% by weight and binder being present up to 25% by weight, and wherein relative to their initial ratio of sizes the ratio of the size of the graphite matrix to structural graphite increases with increasing irradiation, the fuel compacts being seated in the bores of the structural graphite without gap, and whereby due to the change in ratio of the size of the graphite matrix to structural graphite with increasing irradiation there is no gap in the bores when the reactor is in operation.
2.
A finished fuel element according to claim 1 wherein the graphite matrix swells more during irradiation than the structural graphite.
3.
A fuel element according to claim 2 wherein the binder is (1) and is present in an amount of 2 to 15% by weight.
4.
A fuel element according to claim 2 wherein the binder is (2) and is present in an amount of 2 to 25% by weight.
5.
A process comprising filling the bores of a prismatic graphite block with the molded fuel compacts of claim 2 wherein the compacts are fabricated from a graphite molding powder consisting of natural graphite and binder, the binder being not over 15%, and wherein the molded compacts are heat treated to a maximum temperature of the heat treatment ranging between 1500 and 2000.
degree.
C and these treated compacts are exactly filled into the bores of the graphite block, said filled graphite block being inserted into the high temperature reactor without further heat treatment before insertion whereby there is no space between the fuel compact and the graphite of the block