As one of the significant equipment in CEFR operation system, cold trap plays an important role in purifying the coolant sodium and ensuring the safe and steady operation of the reactor. After several years’ of operation, the cold trap of CEFR can’t work very well as it has been designed previously, which results in the low impurity aggradation efficiency, being easily blocked and frequent replacement. Analyzing the structure of the current cold trap, there are two possible reasons causing the problems mentioned above. The first one is that the sodium flow path is improper in the cold trap resulting in the blockage in specific area. The second one is that the density and layout of wire mesh didn’t take the zoning scheme, which would make the precipitation of impurities become easier in exterior area and the flow path is thus blocked.

Based on the two reasons, a modified scheme is proposed from the view of structure and hydraulics to improve the impurities precipitation mode so that the lifetime of the cold trap can be prolonged. The modified scheme is to block about 1/3 orifices on interior cylinder wall in wire mesh zone and to open two rows of diversion holes on the upper support plate of wire mesh so that the velocity distribution can be improved. Meanwhile, in order to make impurities precipitate from the bottom of the cold trap, the wire mesh is arranged to be in upper, middle and lower areas using different wire mesh density. By 3-D modeling and numerical analysis and then comparing the results to that of current cold trap of CEFR, it can be concluded that the velocity distribution in modified scheme is more reasonable and the new layout of the wire mesh can meet the impurities precipitation requirements better. Further comparative analysis with the results under the actual operational condition will be carried on after the completion of the manufacture for modified cold trap.

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