Workshop proceedings of ISAMM 2009 - Code analysis for supporting SAMGs

Nine papers were presented in Sessions 4 and 5, on the general subject of 'Code Analysis for Supporting SAMGs'. The papers addressed a wide spectrum of topics and described deterministic analysis of a several different reactor designs. The papers stimulated several useful and interesting comments and discussions. Discussion on the various topics can be summarized in three broad areas: (1) Deterministic consequence analysis, (2) Use of deterministic analysis to identify and verify SAM measures, and (3) Investigations of particular severe accident phenomena. General conclusions are as follows: (i) Technical progress was reported in modelling severe accident and consequence analysis, permitting realistic updates or revisions to past analysis of quantitative estimates of offsite radiological accident consequences. However, applications of these models to representative severe accident sequences led to very different conclusions regarding the extent to which quantitative health objectives (QHOs) have been achieved after severe accident measure implementation. (ii) Differences of opinion remain in the confidence with which SAM guidance can recommend the reintroduction of water to molten core debris, during either the in-vessel or the ex-vessel phase of the accident. Concerns regarding the detrimental side effects of the interaction between water and core debris (especially at coolant low flow rates), have not been fully resolved. (iii) Severe accident sequences involving induced steam generator tube rupture (SGTR) remain an important contributor to risk for some PWRs and a significant challenge for developing SAM measures. The relationship between the time of this event and the time at which creep rupture occurs at other locations in the RCS (e.g., hot leg) has a first-order impact on the radiological source term to the environment. If hot leg creep rupture occurs soon after tube rupture, a substantial fraction of fission products are discharged into containment, reducing the activity available for release to the environment through the ruptured SG tube(s). (author)