Nuclear facility decommissioning

Decommissioning a nuclear facility is a complicated and long-term project, sometimes taking decades. Just as with the commissioning process, most jurisdictions have strict rules governing nuclear power plant decommissioning. These not only cover safe disposal of radioactive fuel but also involves clean-up and removal of contaminated plant systems, structures and components. The aim of nuclear facility decommissioning regulations is to always protect the public and environment during the entire process.

Be prepared well in advance of decommissioning

Operators should start decommissioning preparations long before a nuclear power plant has generated its final KWh of electricity. In some countries, decommissioning processes are already laid down in the operating licence but in others, regulators need to see decommissioning plans years in advance.

The approach to a decommissioning plan usually depends on regulatory requirements, the results of any public consultation undertaken and decommissioning costs. It is therefore important for operators to ensure they not only have the plans but also the funding to cover the costs of decommission.

Identifying best practice in decommissioning and dismantling is a challenge for both operators and contractors. Rules and regulations in the sector are often much stricter than conventional demolition as protection from radiation is of upmost importance. TÜV SÜD supports companies in following best practice for decommissioning and dismantling, drawing on more than 50 years’ experience in the nuclear field and nuclear decommissioning.

The decommissioning process: choices and recommendations

The decommissioning process beings with removing the used nuclear fuel elements from the reactor. This usually represents over 99% of the radioactive material of each site.  Each element is placed into a spent fuel pool, allowed to cool for at least 90 days, and then transferred into dry storage containers (which can be stored on-site or transported to another facility).

Decommissioning strategies then fall into two main areas: Immediate dismantling (sometimes referred to as DECON (Decontamination)) or deferred dismantling (also known as SAFSTOR (Safe Storage)).

As the name suggests, immediate dismantling sees the operator removing any radioactive material and waste remaining before demolishing the plant’s building, facilities, and structures. This usually takes just under a decade. If a safe storage plan is pursued, the active elements of the plant (the reactor pressure vessel containing the reactor core and other key reactor internals together with the surrounding area) remain in place. All other parts which can be decontaminated are removed, including the turbines and turbine hall. The residual radioactive elements are allowed to decay in-situ over a period of 40 – 60 years. After long-term storage is complete and radioactive levels have fallen, the site is demolished and cleared.

Ending operations: Decommissioning reporting and documentation

Planning and implementing a decommissioning project is a complex operation. A fundamental element is the protection of workers, the wider public and the environment from residual radiation – both during the decommissioning work itself and into the future.

TÜV SÜD support nuclear regulators with drawing up continuous monitoring, testing, and reporting regimes to show that operators are complying with their responsibilities as laid down in their decommissioning licence.

Operators wanting to shut down a nuclear power plant usually need to apply for a decommissioning licence from the authorities. TÜV SÜD supports operators with decommissioning reports and documentation covering, among other things, end-state definitions, feasibility studies, waste assessments, and safety cases. This helps with getting regulatory approval and provides a timetable within which work can be undertaken.

During the decommissioning phase, there are numerous technical and non-technical processes to complete as well radiological hazards to be managed and removed. Again, TÜV SÜD’s experts help with such cases to ensure the decommissioning plan is totally compliant and documented in full.

Once these steps have all been completed, the site can be handed back and used for other purposes.