The nuclear testing facilities all around the world which perform irradiation experiment sometime use sodium inside the experiment itself to enhance thermal heat transfer. Nowadays, the development of sodium technologies for the Sodium Fast Reactor (SFR) requires new easiest methodologies to be able to characterise all aspects related to the use of sodium. Usually, the level of sodium inside a sealed metallic sample holder is checked with X-ray but sometime, especially if the sodium to detect is not so much, there could be some troubles finding its exact level. The problems, checking the level of the sodium with X-ray, are due to the fact that the opacity of thin layer of sodium cannot be easily recognised. Moreover, a check on the volume of sodium inserted cannot always be sufficient to establish the exact level of the sodium inserted due to the geometrical complexity of the devices contained in the metallic sample holder and generally it is used as double check when the exact level of the sodium is recognised with the use of X-ray. The needed to establish the exact level of sodium inserted in a metallic sample holder came from an experiment which has been recently performed at the High Flux Reactor (HFR) in Petten. The name of the experiment was HELIOS and it was dealing with the irradiation of U-free fuels containing americium. The X-ray performed on the sample holder containing HELIOS shows immediately the difficulty to see, among the other things contained in the sample holder, the exact level of the sodium inserted. Hence, it started an investigation to find out other easy and cheap methods that, together with X-ray, can help the detection of the level of sodium. In fact the availability of other easy and cheap methods based on different physical phenomena, although can be affected by the same problems encountered with the X-ray, can be useful to confirm the exact level of the sodium inside a metallic sample holder. A round Robin test has been prepared with a dummy metallic sample holder filled with an unknown amount of sodium. The paper will contain the background of the methodology that could be employed as well as the description of the experiments performed in order to establish the level of the sodium inside a dummy sealed stainless steel sample holder filled with an unknown amount of sodium. An original, easy and cheap methodology will be described. It should be mentioned that a deep investigation using ultrasonic device has not been performed because it was considered obviously useful and the natural alternative to the X-ray methods. Other methodologies have been investigated because it was considered much easier and less expensive.