Zuber (1980), Heisler (1982) and Ishii-Kataoka (1984) provide scaling laws for single-phase natural circulation. All the three scaling laws are derived from the governing differential equations. One of the problems associated with these scaling laws is that the number of similarity groups are too many and they do not provide steady state or stability solutions in terms of the proposed similarity groups. Therefore, testing of these scaling laws with the available experimental data is rather difficult without the use of system codes. This arises due to the fact that more than one scaling parameter is a function of the flow rate, which for a natural circulation loop is not known apriori. To overcome this problem, Vijayan et al. (1992) proposed a scaling procedure by which the steady state flow rate can be obtained as a function of just one similarity group. This procedure has been extended recently to nonuniform diameter loops (Vijayan (1999), see also section 3). They have also obtained the stability solution in terms of the similarity groups.