[en] Basic operating characteristics are shown of nuclear power plants classified according to reactor type (PWR, BWR, PHWR) and to output (lower than 600 MW and higher than 600 MW). For each nuclear power plant the month and the year of commissioning is listed. The following operating characteristics were used for the assessment of the respective plant types: installed output coefficient of availability Ksub(iv), total temporarily reduced output in proportion of obtainable output, temporarily reduced output within projected maintenance and refuelling, and temporarily reduced output due to failure or accidents. The mean Ksub(iv) value in the individual years is shown for the PHWR, PWR and WWER power plants to be 64%, 62% and 58%, respectively. Operating reliability is analyzed from the aspect of available and failed output. In the given period the average available output for PHWR, PWR and BWR power plants was 71%, 61% and 60%, respectively. The total temporarily reduced average output was 29%, 39% and 40%, respectively, while the average temporarily reduced output for projected shutdowns was 10%, 19% and 20%, respectively. With regard to the utility system, currently the average available output of PHWR, PWR and BWR power plants may be considered to be 63%, the average total temporarily reduced output 37%, the average total temporarily reduced output due to projected outings 17%, and the same parameter due to failures amounts to 20%. Operating performance of PHWR power plants are significantly more favourable compared with PWR and BWR plants. The analysis is presented of causes of projected and nonprojected shutdowns of nuclear power plants in 1974. Major failures and circumstances affecting the total temporarily reduced output are described. (J.P.)