Recent Improvement of Athas Code for SCWR

Abstract

ATHAS code has been successfully applied in SCWR subchannel analysis. The present paper gives the recent achievements of the code: (1) Subchannel analysis of CANDU-SCWR sliding pressure startup procedure: The subchannel analysis was performed for startup procedure, which covers the pressure range from 8MPa to 25MPa, flow pattern covers two phase flow and supercritical condition. The results show that proposed startup procedures can meet thermal-hydraulics criteria; the high sheath temperature should be carefully analyzed with PDO heat transfer model at pressure near critical point; (2) Subchannel analysis of CANDU-SCWR reheat bundle: The inlet condition for reheat bundle is different from that for normal bundle, such as superheated steam, subcritical pressure condition. The results show that the bundle can meet thermal-hydraulics criteria, and the pressure drop is much higher than normal bundle, which should be carefully designed; (3) Subchannel analysis of bundle with wire wrap: Wire wrap model was developed and added in the ATHAS code.