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[Supplementary explanation] Outline of control rod withdrawal test The reactor core of the HTTR is composed of the fuel elements, the replaceable reflector blocks and the permanent reflector blocks. Sixteen pairs of control rods are located to control the reactor power. The control rod withdrawal tests were performed so as to insert a positive reactivity by withdrawing a pair of control rod located in the center of the reactor core among sixteen pairs of control rods as shown in Fig. 1. The tests were systematically performed so as to change the control rod withdrawal speed (two different speeds) and withdrawal length (three different withdrawal lengths) in each four initial conditions of the reactor power in the region from 30% (9MW) to 80% (24MW).   Figure 3 shows the reactor behavior during the control rod withdrawal test with the control rod withdrawal speed of 5mm/s and the withdrawal length of 40mm at the initial reactor power of 80% (24MW). The reactor power increases just after the control rod withdrawal. Then the reactor power decreases slowly due to the excellent and inherent safety characteristics of the HTGR and becomes to the stable state. The pre-analysis result shows the good agreement with the experiment result.  (BACK) |
