[en] The purpose of this paper is to describe the regulatory activities carried out in Spain as a result of the design problem occurring in the steam generators during operation of Unit I of the Almaraz nuclear power station. First, a brief introduction is given to the operating history and characteristics of Unit I of Almaraz. Particular attention is paid to the specific licences issued subsequent to commercial operation which place limitations on the operation of the station and to the operational incidents of which the Nuclear Safety Council (CSN) has been notified. Next, a description is provided of the safety evaluation carried out by the CSN. Three aspects merit particular attention: methodology, evaluation and conclusions. The methodology applied by an importing country is normally based on that of the country of origin of the design, so that the overall evaluation by the NRC has been considered sufficiently representative of aspects specific to the Almaraz power station. In this regard the importance of international collaboration is clearly seen as a principal instrument for performing the evaluation. In the evaluation a distinction is made between general and specific aspects and between inspection programmes and quality assurance requirements. In addition, the conclusions leading to the requirement of the imposition of additional limitations on the operating licence are stated. Apart from the safety evaluation carried out by the CSN, other regulatory activities have been performed over this two-year period. These activities, which include site inspections, audits of the principal supplier company, other independent calculations and so on, are described. Lastly, the paper refers to the lessons learned from the operation of the above-mentioned unit, which are immediately applicable to other Spanish nuclear power stations. (author)