1. National Research and Development Institute for Cryogenics and Isotopic Technologies – ICSI Ramnicu Valcea, 4 Uzinei Street, P.O. Box Raureni 7, Ramnicu Valcea 240050, Romania
2. University Politehnica of Bucharest, Faculty of Power Engineering, 313 Splaiul Independentei, Bucharest 060042, Romania