Chemical characteristics of helium coolant of HTTR (High Temperature engineering Test Reactor)

HTTRのヘリウム冷却材の化学特性

濱本 真平  ; 島崎 洋祐 ; 古澤 孝之 ; 根本 隆弘; 猪井 宏幸; 高田 昌二

Hamamoto, Shimpei; Shimazaki, Yosuke; Furusawa, Takayuki; Nemoto, Takahiro; Inoi, Hiroyuki; Takada, Shoji

The technical basis of helium gas purification control for HTGRs was established by verifying the design of the PHPS of the HTTR by showing that the measured concentrations of impurities of the primary helium coolant were restricted below the criteria of control to protect the graphite oxidation, and that the carburization atmosphere was maintained to keep intact of metallic high temperature components, in the 30-day continuous operation and the 50-day long term high temperature operation. The analytical model, which was newly established by improving the conventional method that predicted the impurity concentrations conservatively higher than the measured values, predicted the composition of the impurities such as H, CO, HO and CO, which is determined by the temperature dependency of release of impurities during the rated power operation adequately. However, the measured concentration of HO remarkably decreased while the concentration of CO increased in the primary helium coolant in the long term high temperature operation. It is presumed that the chemical reactions in gas phase made the concentration of HO remarkably decrease while made the concentration of CO increase, which does not affect the intactness of core graphite components and high temperature metallic components significantly.