[en] Supercritical pressure natural circulation experiments were carried out with CO₂ in a uniform diameter rectangular loop. Experimental data were generated on, steady state flow, heat transfer and stability under natural circulation conditions. The steady state flow rate data obtained were compared with the predictions of 1-D code NOLSTA which showed good agreement. The supercritical heat transfer coefficient data showed a peak around the pseudocritical point. The heat transfer coefficient data were compared with different correlations reported in the literature. Good agreement was obtained with the prediction of McAdams, Bishop, Jackson and Jackson Fewester correlations. Instability was observed in the loop in a narrow window around the pseudo critical region with low cooling water flow rate for the HHHC orientation. All other orientations of heater and cooler were found to be stable. The stability data were compared with the predictions of the nonlinear stability analysis code NOLSTA. The details of the experimental set-up, experiments carried out and the results of the analysis are presented in this report. (author)