Application of measuring apparatus for non-condensable gas concentration to LSTF experiment

Kamiwaki, Tadayoshi; Owada, Akihiko; Takeda, Takeshi; Nakamura, Hideo

JAEA-Testing 2008-006, 77 Pages, 2008/07

JAEA-Testing-2008-006.pdf:6.32MB

Non-condensable gas for the pressurization of accumulator (ACC) tanks of emergency core cooling system may flow into the primary system during loss-of-coolant accidents (LOCAs) in a pressurized water reactor (PWR) after the ACC coolant injection is completed. Since the non-condensable gas may travel to and accumulates in steam generators (SGs) U-tubes, primary cooling and depressurization via SG secondary-side depressurization would become ineffective because of the degradation of condensation heat transfer in SG U-tubes. Since quantitative measurement of gas concentration is necessary to clarify the influences of non-condensable gas on the depressurization in ROSA/LSTF experiments that simulate PWR LOCAs and transients, an apparatus using a Zirconia oxygen sensor has been developed to directly measure the gas concentration in steam by introducing air as the non-condensable gas for the ACC pressurization. This apparatus is improved and applied to LSTF experiments where the gas concentration is measured directly in vessel upper head where gas may pass through with steam and in SG outlet plenum where gas accumulates. This report describes the improvement of the apparatus and the results of oxygen gas measurement characterization tests and the LSTF secondary-side depressurization experiments.