Uncertainty of specific heat of uranium dioxide fuel pellets by differential scanning calorimetry


K. Faêda1, L. Carneiro1, C. Vicente1, F. Lameiras1, D. Camarano1 and L. de Faria1

1CDTN/CNEN Centro de Desenvolvimento da Tecnologia Nuclear/ Comissão Nacional de Energia Nuclear, Brazil

Keywords: differential scanning calorimetry, uncertainty
property: specific heat
material: uranium dioxide

In manufacturing the nuclear fuel, characterizations are performed in order to assure the minimization of harmful effects. The uranium dioxide is the most used substance as nuclear reactor fuel because of many advantages, such as: high stability even when it is in contact with water at high temperatures, high fusion point, and high capacity to retain fission products. One of the import thermophysical properties to be determined of uranium dioxide (UO2) is the specific heat. The determination of specific heat is one of the applications of differential scanning calorimeter (DSC). The accuracy of measurement and level of uncertainty of the resulting data are important. In general, typical uncertainties of 1% a 5% [1] are reported for the DSC. However, in the ASTM E 1269-95 [2] estimations such as 6,2% for the precision (repeatability) and 8,4% for the reproducibility were obtained from an interlaboratory study in which seven laboratories test three materials. This paper describes a general metrological characterization of a specific heat measurement instrument, using differential scanning calorimetry technique. The estimate of uncertainty is determined according to ISO / BIPM Guide to the Expression of Uncertainty in Measurement [3] and by Monte Carlo Method [4]. The results obtained for the specific heat of three uranium dioxide pellets at 26,85 °C, are discussed and compared with literature data. The 95% coverage interval for the heat specific determined using the two approaches is about 8%.

References
  1. Rudtsch, S., Thermochimica Acta., 382, 17 (2002)

  2. ASTM - American Society for Testing and materials. ASTM-E-1269-05: Standard test method for Determing Specific Heat Capacity by Differential Scanning Calorimetry, Philadelphia: ASTM (2005)

  3. JCGM, Evaluation of measurement data - Guide to the Expression of Uncertainty in Measurement, JCGM 100 (2008)

  4. JCGM, Evaluation of measurement data - Supplement 1 to the Guide to the Expression of Uncertainty in Measurement - Propagation of distributions using a Monte Carlo method, JCGM 101(2008)

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