Design report for a reloadable annular fuel element NY709 und NY710

Ring-shaped carrier fuel elements had been inserted already in the second core of the KNK II reactor in positions 100 and 201. This report describes a reloadable oxide annular fuel element with Mark II pins for accommodating oxide 19-pin test bundles in the test zone position 205 in the third core of KNK II and justifies its design concept. The annular element comprises 102 fuel pins of 7.6 mm diameter arranged in three pin rows in a driver wrapper and skirts for fixing the spark-eroded spacers. In order to lower the pin power the fuel stacks have been reduced from 600 to 500 mm for a standby element envisaged for possible future loading. The report deals with the ring element with its components such as the fuel pin, the bundle, the wrappers, the head and the foot, and it describes methods, criteria and results of design. The test bundles housed in the annular carrier element are treated in a separate report. By enveloping proofs the compliance of the design goals is evidenced for the envisaged service life of 720 full power days. The report is based on the INTERATOM design report for the test zone fuel elements of the third KNK II core