[en] This report covers work in the first phase of a two phase program aimed at extending the capability of in-process acoustic emission monitoring of nuclear fabrication welds from flaw detection and location to flaw characterization in terms of type and size. During this first phase, previously acquired AE data from laboratory and shop nuclear fabrication welds were analyzed and computer subroutines were developed that would automatically determine flaw type and size. After optimization on this large bank of recorded AE data the best models were tested on both live laboratory welding and actual shop welds. The results of these tests were very encouraging and indicate that in-process acoustic emission monitoring can provide useful information as to flaw size and type. This reported work was accomplished using a GARD-developed microprocessor-based AE analyzer