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Journal Articles

A ROSA-V experimental study on PWR accident management actions and role of reactor instrumentation

Suzuki, Mitsuhiro; Takeda, Takeshi; Asaka, Hideaki; Nakamura, Hideo

Nihon Kikai Gakkai 2005-Nendo Nenji Taikai Koen Rombunshu, Vol.3, p.223 - 224, 2005/09

Shown below are experimental results on characteristics of reactor instrumentations including a coolant mass tracking method and core exit thermocouples (CETs) which are necessary to precise operator actions for accident management (AM) during a loss-of-coolant accident (LOCA) at a pressurized water reactor (PWR). The experiments at the ROSA-V/LSTF facility of the Japan Atomic Energy Research Institute simulated small break LOCAs at the PWR vessel bottom and clarified effects of secondary depressurization as one of the AM measures in case of high pressure injection system failure and non-condensable gas inflow from the accumulator injection system. It was shown that the coolant mass tracking method based on three types of water level instruments could detect most of the primary coolant mass change between the initial state and core-heatup starting condition. The CET characteristics to detect the core heatup conditions were significantly degraded by the condensed water fall-back during the secondary depressurization action.

Journal Articles

Local temperature and phase measurement in water-melt multiphase flow with bifunctional probe and electrical signal processing

Shibamoto, Yasuteru; Sagawa, Jun*; Kukita, Yutaka*; Nakamura, Hideo

Konsoryu, 17(2), p.171 - 179, 2003/06

A bifunctional probe was developed for simultaneous, high-speed measurement of local temperature and phase of fluid at the same place. It was designed for application to water/melt multi-phase experiments involving transient boiling of water on the surface of molten metal. An unsheathed thermocouple (TC) of a small wire diameter was used for phase detection, that is distinction of melt/water/vapor phase, as well as for temperature measurement of each phase. The phase was detected by measuring the electric impedance between the TC and the ground. A 100-kHz AC signal was imposed on the TC wire for this purpose. The AC signal was filtered out from the temperature signal before it was amplified. With the first design of low-pass filter (LPF), however, a large noise was induced in the temperature signal every time the TC was grounded electrically by contact with molten metal. This problem was overcome by redesigning the LPF. The final design succeeded in measuring the quick movements of interface and the temperature changes in the individual phases in a water-melt-vapor multiphase flow.

Journal Articles