In a tritium handling facility it is important to know the volume of the parts of the system for accurate accountancy. The usual methods to determine volumes have several disadvantages concerning contamination issues and accuracy.

In this work a novel method is used to determine volumes. The method does not require any liquid or precisely known reference volume. It is simple and the uncertainty of the measurement is lower than 1% for volumes from 10 cm3 to 10 dm3.

In this paper the principle of the volume determination device (VDD) designed and built at the Tritium Laboratory Karlsruhe (TLK) is presented, together with a detailed uncertainty calculation. Also the first measurements with the VDD are discussed in detail.