Stand-Alone Containment Analysis of the Phébus FPT Tests with the ASTEC and the MELCOR Codes: The FPT-0 Test

Abstract

The integral Phébus tests were probably one of the most important experimental campaigns performed to investigate the progression of severe accidents in light water reactors. In these tests, the degradation of a PWR fuel bundle was investigated employing different control rod materials and burn-up levels in strongly or weakly oxidizing conditions. From the results of such tests, numerical codes such as ASTEC and MELCOR have been developed to describe the evolution of a severe accident. After the termination of the experimental Phébus campaign, these two codes were furthermore expanded. Therefore, the aim of the present work is to reanalyze the first Phébus test (FPT-0) employing the updated ASTEC and MELCOR versions to ensure that the new improvements introduced in such codes allow also a better prediction of these Phébus tests. The analysis focuses on the stand-alone containment aspects of this test, and the paper summarizes the main thermal-hydraulic results and presents different sensitivity analyses carried out on the aerosols and fission products behavior. This paper is part of a series of publications covering the four executed Phébus tests employing a solid PWR fuel bundle: FPT-0, FPT-1, FPT-2, and FPT-3.

Stand-alone containment analysis of Phébus FPT tests with ASTEC and MELCOR codes: the FPT-2 test

“…Because of this, the heat transfer coefficient calculated by MELCOR will increase as the employed CL value decreases. Similar conclusions were also found for the Phébus FPT-0 test [19] . The important influence of the CL was also stressed in [33] , where a study on the influence of the CL value on the heat transfer and condensation rates for vertically-oriented plate HSs was performed.…”

“…On the contrary, such analyses were not carried out for ASTEC because acceptable values were obtained employing the standard input decks. Similar issues were also found in the analysis of the Phébus FPT-0 test [19] . As for the FPT-0 test, the CL values of the CV outer surfaces were found to be the most influencing parameter.…”

“…The present paper is a part of a series of publications, covering the 4 Phébus FP tests carried out using a PWR fuel bundle: FPT-0 [19] , FPT-1 [20] , FPT-2, and FPT-3. Observations made during these analyses led to a thorough understanding of the in-containment source term and its coupling with thermal hydraulics under unsaturated but condensing atmospheres.…”

Implementation and validation of a resuspension model in MELCOR 1.8.6 for fusion applications

“…In ECART a similar behavior is shown varying the collision shape factor. As stated in different works, the collision shape factor is always a gamechanging parameter, thus its modification from the default value (1.0) should be always performed with caution [33] [34]. Overestimated values are generally showed by ASTEC, no matter of the differences among the different cases considered.…”

Standalone Containment Analysis of Four Phébus Tests with the ASTEC and the MELCOR Codes

“…These analyses were performed with recent ASTEC and MELCOR code's versions to evaluate the effects of the improvements and modifications implemented in both of them in the latest years to account for the new findings from international researches [13,14]. The present paper is the last of five publications covering the Phébus tests executed with a solid PWR fuel bundle (FPT-0 [15], FPT-1 [16], FPT-2 [17], and FPT-3 [18] tests).…”