At the same time, HSK performed the function of supervising radiation protection for all the nuclear plants, as well as tasks in connection with the interim and final storage of radioactive waste.
These tasks mentioned above have been performed by the Swiss Federal Nuclear Safety Inspectorate ENSI since 1 January 2009.
This step satisfied the requirement for the independence of the regulatory body as stipulated in the Convention on Nuclear Safety, a legal text adopted at the International Atomic Energy Agency (IAEA) in 1994 and setting the bases for nuclear safety worldwide and ratified by Switzerland subsequently.
[3] ENSI verifies whether the operator fulfils this responsibility, and organises its own analyses, inspections and supervisory discussions in order to obtain its own bases for this assessment.
For example, the periodic safety reviews (PSRs) undertaken by all the nuclear power plants are assessed by ENSI, and the results are recorded in an expert report together with any conditions that may be imposed.
ENSI processes applications for changes to nuclear plants which are covered by existing operating licences and issues permits if the decisions are positive.
In case of an incident, this data enables ENSI to issue forecasts regarding the potential dispersion of radioactivity in the surrounding area.
ENSI is integrated into a nationwide organisation to deal with serious incidents, which includes the National Emergency Operation Centre (among other bodies).
[7] ENSI collates all the data acquired during the course of a year into a Systematic Safety Evaluation, from which it derives any measures that may be required as well as the plans for its future supervisory activities.
ENSI also provides information to the public in its annual reports on the safety of nuclear plants, radiation protection and the experience accumulated from operation and research.
Eleven of these events took place in the two reactors of the Beznau nuclear power plant, four at Mühleberg, three at Gösgen and four at Leibstadt.
To put the events at Mühleberg into context, ENSI states that the disturbances occurred "essentially" during the commissioning of new equipment.
ENSI did not register any events at the two research reactors of the Swiss Federal Institute of Technology, Lausanne and the University of Basel.
ENSI assigned one event to INES level 2: this occurred during the planned maintenance outage at the Leibstadt nuclear power plant on 31 August 2010.
ENSI did not register any events at the Swiss national central interim storage facility for radioactive waste (ZWILAG) or in the research reactor at the University of Basel.
The INES-1 event was reported as the consequence of a potential blockage of the water intake for the special emergency system during an extreme flood at the Mühleberg nuclear power plant.
This involved a disturbance in unit 2 of the Beznau nuclear power plant: the special emergency diesel generator (SEDG) failed to start during a periodic function test.
The plant's specialist staff were summoned to vent the fuel feed line, after which the unit started when another attempt was made.
On the INES scale, ranging from 0–7, ENSI rated all reportable events in nuclear power plants in 2013 as Level 0.
No incidents were reported by the ZWILAG central interim storage facility and the research reactor at the University of Basel.
A limited availability of emergency cooling systems at Leibstadt NPP led to an INES-1 assessment on the "International Nuclear Event Scale" of the IAEA.