Determination of hydrogen concentration in Zircaloy cladding using hot vacuum extraction method with two-step heating

Obata, Hiroki; Toyokawa, Takuya ; Tomita, Takeshi; Kimura, Yasuhiko

The amount of hydrogen absorbed to the fuel cladding increases by extended burnup fuel. The absorbed hydrogen that exceed solid solubility limit precipitates as the hydride phase. The high concentration of hydride causes the fuel cladding embrittlement which might become the origination of fractures of the cladding. Therefore, it is important to measure the hydrogen content in the cladding to estimate the safety margin of the irradiated cladding. Hydrogen is absorbed not only in the cladding metal phase, but in the oxide layer. To evaluate the embrittlement of the cladding, it is necessary to measure the hydrogen content in the cladding metal phase and oxide layer separately. Therefore, the two-step heating method can measure the amount of hydrogen in the metal phase and the oxide layer separately. This paper shows the technical review of measuring method including the technique for the determination of extraction temperature.