| 摘要 |
In a high rate pulling with a cooler 10 surrounding a single crystal 8, steam explosion by leakage from the cooler 10 is prevented. Flow rates La, Lb of cooling water are measured by flowmeters 14a, 14b on a cooling water inflow side and cooling water outflow side of the cooler 10. When flow rate difference DeltaL (La-Lb) determined from the flow rates La, Lb exceeds 20 cc/minute, open/close valves 15a, 15b, 15c are operated to stop water supply to the cooler 10 and drain outward the cooing water in the cooler 10.
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