Features of a control blade degradation observed in situ during severe accident conditions in boiling water reactors. Issue 5 (4th May 2019)

• Record Type: Journal Article
• Authors: Pshenichnikov, Anton; Yamazaki, Saishun; Bottomley, David; Nagae, Yuji; Kurata, Masaki
• Is Part Of: Journal of nuclear science and technology. Volume 56:Issue 5(2019)
• Page Start: 440
• Page End: 453
• Publication Date: 2019-05-04
• Subjects: Boiling water reactor -- severe accident -- Fukushima Dai-Ichi decommissioning -- control blade degradation -- boron carbide -- steam starvation; Nuclear engineering -- Periodicals; Nuclear physics -- Periodicals; Nuclear energy -- Periodicals; 621.4805
• DOI: 10.1080/00223131.2019.1592724
• Languages: English
• ISSNs: 0022-3131

Abstract

ABSTRACT: In the present paper, new results using in situ video are presented regarding boiling water reactor (BWR) control blade degradation up to 1750 K at the beginning of a nuclear severe accident. Energy-dispersive X-ray spectrometry (EDS) mapping indicated stratification of the absorber blade melt with formation of a chromium and boride-enriched layer. High-content-B- and C-containing material with increased melting temperature acted like a shielding and was found to prevent further relocation of control blade claddings. The interacted layers around the B4 C-granules prevented direct steam attack of residual B4 C. The results provide new insights for understanding of the absorber blade degradation mechanism under reducing conditions specific to Fukushima Dai-Ichi Unit 2 resulting from prolonged steam starvation.