Updated analysis of Fukushima Unit 3 with MELCOR 2.1. Part 2: Fission product release and transport analysis. (August 2019)

• Record Type: Journal Article
• Authors: Fernandez-Moguel, L.; Rydl, A.; Lind, T.
• Is Part Of: Annals of nuclear energy. Volume 130(2019)
• Page Start: 93
• Page End: 106
• Publication Date: 2019-08
• Subjects: ADS automatic reactor depressurization system -- BSAF Benchmark Study of the Accident at the Fukushima Daiichi Nuclear Power Station -- Cs caesium -- DW drywell -- FP fission product -- I iodine -- NG noble gases -- PCV Primary Containment Vessel -- RPV reactor pressure vessel -- SRV Safety Relief Valves -- S/C suppression chamber -- Te tellurium -- U3 Unit 3; Nuclear energy -- Periodicals; Nuclear engineering -- Periodicals; 621.4805
• DOI: 10.1016/j.anucene.2019.02.017
• Languages: English
• ISSNs: 0306-4549

Abstract

Highlights: The FP release and transport of Fukushima Unit 3 was analyzed with MELCOR 2.1. Three plausible scenarios were selected as the most representatives. The estimated dose rate in S/C and DW were compared against CAMS data. The atmospheric releases were compared against reverse calculations. The best estimation case sequence was in agreement with the first part of the study. Abstract: The fission product release and transport during the accident of Fukushima Daiichi Unit 3 was analysed in the present paper as a complement to the thermal-hydraulic analysis presented in the first part of the present study, where three sequences obtained with MELCOR 2.1. were evaluated. The calculation results were compared against the available data for fission products: i) dose rate measurements in the containment drywell and suppression chamber, ii) the environmental release data by reverse calculations performed with WSPEEDI-II, and iii) estimations of water releases to the turbine and reactor buildings. From the fission product analysis perspective, the best results were obtained with case 2 sequence, further confirming the results obtained in the first part of the analysis. However, the comparison of the analysis results with the dose rate measurements in the drywell indicates that the reactor pressure vessel failure took place 2 h earlier than predicted in the case 2, i.e., at ca. 62 h after scram.