CLADS test facilities on BWR core material degradation

廃炉国際共同研究センターにおけるBWR溶融挙動に係る試験装置

永江 勇二 ; 柴田 裕樹 ; Pshenichnikov, A. ; 山崎 宰春; 倉田 正輝 

Nagae, Yuji; Shibata, Hiroki; Pshenichnikov, A.; Yamazaki, Saishun; Kurata, Masaki

Two control blade degradation test facilities which were designed for the investigation of high temperature degradation of the nuclear reactor elements, have been set up in Tomioka-site. One was a test facility for small-scale samples and another one was test facility for large-scale samples. In situ video of the experiment and mass-spectrometric analysis of the output gases can be carried out during tests, and heating rate can be controlled up to 1 K/s. The working area of the large-scale facility consists of the isolated heating area 1.2 m height with the water cooled lower part to achieve the natural temperature gradient conditions as during severe accident. Steam rate in large-scale facilities can be controlled in the range of 15-100 g/min, and a test piece for the control blade degradation tests can be used to simulate a part of the control blade and fuel assembly. Chemical reaction between stainless steel/BC and Zry is affected by the oxide layer on Zry. The oxidation behavior depends on steel flow rate and tendency of control blade degradation possibly has threshold condition. According to pretest, critical condition for reaction between molten control rod and channel box can be recognized. Further analysis and tests in various steam rate will be conducted to evaluate the critical condition.