TRITIUM RETENTION IN GRAPHITE INNER WALL OF JT-60U

In JT-60U, D-D experiments have been performed since July 1991. Althou gh tritium, which is produced by the D-D reaction, is programmed to be exhausted through pumping systems, a part of the tritium is trapped i n the graphite inner wall. To evaluate the tritium retention in the gr aphite wall of JT-60U, several sample tiles were removed from JT-60U i n November 1993. The retained tritium distribution in the graphite til es was measured by means of burning sample pieces, converting the trit ium into HTO and scintillation counting the resultant water. The resul t of?his measurement showed that tritium of 1.6 x 10(10) Bq still rema ined in the graphite first wall. This value corresponds to approximate ly 50% of the tritium generated from July 1991 to October 1993 in JT-6 0U. The tritium remaining in the divertor tiles was in higher concentr ation than that in the first wall. In particular, the tritium concentr ation peaked in the tiles between the strike points. Tritium at the st rike points, where an electron or ion strikes directly, was in low con centration.