Accuracy assessment of the in-bed calorimetry employed in ITER SDS

Accuracy of the ITER SDS in-bed calorimetry is examined numerically at various tritium inventories for two different He loop configurations taking into account the error sources of the mass flow meter, the temperature gauge, the decay heat of tritium, the deviation of measurement condition from the steady-state condition, and the heat loss by thermal radiation. Although the radiative heat loss occupies a significant fraction of 12–25% of total decay heat depending on the configurations of the He loop and tritium inventories, its nearly linear behavior enables to produce a linear calibration curve which shows a deviation of up to 0.5 g of tritium at the given measurement points. The M-shaped configuration of the He loop having larger heat transfer area shows preferable performances over the U-shaped configuration in terms of the rapid measurement and accuracy.