Mock-up test of the modified STACY (Accuracy verification of water-feed- stop switch detector)

Seki, Masakazu; Izawa, Kazuhiko ; Sono, Hiroki 

The Japan Atomic Energy Agency is conducting a reactor modification project of the Static Experiment Critical Facility (STACY). In the modification, STACY is to be converted from a thermal reactor using solution fuel into that using fuel rods and light water moderator. Reactivity of the modified STACY is controlled by the water level fed in the core tank as well as the present STACY. Regarding water level detection, however, a float-type water-feed-stop switch is adopted in the modified STACY because the electro-conductivity-type switch of the present STACY for uranyl nitrate solution cannot detect demineralized water used in the modified STACY. For safety operation of the modified STACY, the float-type switch needs accurate and reliable detection of water level at any temperature. This report describes a mock-up test on accuracy verification of the float-type water-feed-stop switch in whole range of water temperature (room temperature 70C) in the modified STACY operation.