• Journal of the Korean Crystal Growth and Crystal Technology
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• v.13 no.1
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• pp.15-18
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• 2003

High purity single crystalline calcium fluoride ($CaF_2$) has excellent optical transmission characteristics down to deep UV and is therefore selected as the main optical material for the next generation of lithography apparatus operating at wavelength of 157 nm. The growth of large sized $CaF_2$ single crystals with the required properties for this optical application can be achieved only by optimizing the crystal growth process by the aid of numerical simulation. This needs especially a precise calculation of the heat transport and temperature distribution in the solid and liquid $CaF_2$ under crystal growth conditions. As $CaF_2$ is considered to be semitransparent, the internal radiative heat transfer in $CaF_2$ plays an decisive role in the simulation of the heat transport. On the other hand it is very difficult to obtain quantitative experimental data for evaluating numerical models as $CaF_2$ is extremely corrosive at high temperatures. In this work we present a newly developed experimental technique to perform temperature measurements in $CaF_2$-crystal as well as in the melt under conditions of crystal growth process. These experimental results are compared to calculated temperature data, which were obtained by using different numerical models concerning the internal heat transfer in semitransparent $CaF_2$. It will be shown, that an advanced model, which was developed by the authors, gives a much better agreement with experimental data as a standard model, which was taken from the literature.

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2005.06a
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• pp.137-144
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• 2005

Silica in primary system combines with an alkali grammatical particle metal and forms the zeolite layer which is hindering the heat transfer on the surface of the cladding. Zeolite layer becomes the cause of the damage in this way. The problems of the NPP's primary system have been issued steadily by EPRI. Through a series of experiments of the laboratory scale, we confirmed the applicability of NF membrane for silica removal, as silica rejection rate of NF membrane is about $60\;{\sim}\;70\%$ and boron rejection rate is about $10\;{\sim}\;20\%$. We accomplished a site experiment about four NF membranes manufactured by FilmTec and Osmonics Inc. In experiment using 400L of SFP water, when operation pressure is $10kg_{f}/cm^2$, we confirmed that the silica rejection rate of NF90-2540 manufactured by FilmTec Inc. is about $98\%$, boron rejection rate is about $43\%$. The silica rejection rate of NF270-2540 is about $38\%$, boron rejection rate is about $3.5\%$. Afterward, through additional experiments, such as long term characteristic experiments, we are going to design a optimum NF membrane system for silica removal.