A BWR control blade degradation observed in situ during a CLADS-MADE-02 test under Fukushima Dai-Ichi Unit 3 postulated conditions

ABSTRACT

The paper summarizes the results of the control blade degradation test CLADS-MADE-02 performed in the Japan Atomic Energy Agency . The test focused on the beginning phase of the accident at Fukushima Dai-Ichi Nuclear Power Plant (1F) Unit 3. The investigation provided important data, especially on the temperature history, exhaust gas measurement, and in situ video of metallic debris formation and relocation to the colder elevations under the test scenario, which reproduced oxidizing conditions during the initial phase of the 1F Unit 3 reactor heat-up. Complementary post-test analysis by metallography, Raman spectroscopy, elemental scanning electron microscope/energy-dispersive X-ray spectrometry spectroscopy, and exhaust gas analysis provided additional data on the local materials interactions that gave insights on the melt progression scenarios. Based on the test results, some decommissioning-related conclusions concerning the formation of new B-rich phases containing Cr and Fe were made.

KEYWORDS:

• Boiling water reactor
• severe accident
• Fukushima Dai-Ichi decommissioning
• control blade degradation
• boron carbide
• fuel debris

Acknowledgments

A part of this study was performed in the framework of ‘Advanced Multi-Scale Modelling and Experimental Tests on Fuel Degradation in Severe Accident Conditions’ supported by the Ministry of Economy, Trade and Industry, Japan. The authors wish to express their appreciation to Mr. T. Sato, Ms. A. Sudo, and Dr. S. Yamazaki for the help during the test.

Disclosure statement

No potential conflict of interest was reported by the authors.