Experimental determination of the emissivity of nuclear graphite at high temperature conditions

Mechanical Engineering Letters Pub Date : 1900-01-01 DOI:10.1299/mel.20-00204

Peng Chai, Yang Wu, K. Okamoto

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Abstract

increase and Lozier, 1958). Specifically, Seo (2009a; 2009b; 2011) measured the emissivity of several types of nuclear graphite in the temperature range from 100 ℃ to 500℃ and indicating a positive relationship between graphite emissivity and oxidation degree. Abstract In a High-Temperature Gas-cooled Reactor (HTGR), radiation is the dominant form of heat transfer due to the high temperature environment. Therefore, the emissivity of the core materials (mainly nuclear grade graphite) is important for reactor safety assessment. In this paper, the emissivity of nuclear grade graphite IG-110 was measured in the temperature range from 500 ˚C to 1000 ˚C by using an infrared thermometer. Besides, the impact of the graphite oxidation, which may take place in a postulated air ingress accident, was also evaluated. As a result, it was found that the emissivity of IG-110 grade graphite decreases slightly as the temperature increase. Moreover, a relatively high emissivity was detected in the pre-oxidized specimen. Based on the measurement data, two experimental correlations were suggested for the engineering applications. It could also be concluded that the commonly used value of the graphite emissivity (0.8), is conservative for engineering judgment.

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高温条件下核石墨发射率的实验测定

increase and Lozier, 1958)。具体来说，Seo (2009a;2009 b;2011)测量了几种核石墨在100 ~ 500℃温度范围内的发射率，表明石墨的发射率与氧化程度呈正相关。在高温气冷堆(HTGR)中，由于高温环境，辐射是主要的传热形式。因此，堆芯材料(主要是核级石墨)的发射率对反应堆安全评价具有重要意义。本文用红外测温仪测量了核级石墨IG-110在500 ~ 1000℃温度范围内的发射率。此外，还评估了在假定的空气进入事故中可能发生的石墨氧化的影响。结果表明，随着温度的升高，IG-110级石墨的发射率略有下降。此外，在预氧化样品中检测到相对较高的发射率。根据实测数据，提出了两种适合工程应用的实验关系式。也可以得出，常用的石墨发射率值(0.8)对于工程判断是保守的。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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Mechanical Engineering Letters

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