The Nuclear Decommissioning Authority

Last Updated: 22 March 2011

The NDA estate includes:

• reactors
• chemical plants
• research and development facilities
• waste processing and
• fuel fabrication plants

many of which are redundant and all of which will require decommissioning.  Some plants date from the 1940s and 1950s, such as the Legacy Ponds and Silos at Sellafield. These are deteriorating and contain significant quantities of corroding radioactive waste, presenting our highest risk and our greatest decommissioning challenge.

Objective

To deliver site end states as soon as reasonably practicable with a progressive reduction of risk and hazard.

Scope and Boundaries

The Decommissioning strategy relates to the period from Post Operational Clean Out to the delivery of the site end state. It will establish:

• a set of principles for decommissioning and clean-up reflecting approaches used to develop Lifetime Plans (LTP)
• the priority of activities across the NDA's estate
• the NDA's preferred strategy for D&CU of generic facility types, e.g. Magnox reactors and chemical plants

When selecting a D&CU strategy for a site or facility, a range of general and site specific factors need to be considered on a case-by-case basis.

We will provide guidance, direction and the transparency necessary to ensure consistent and reasoned application across the NDA estate which takes government policy and regulatory aspects into account. This means developing principles and strategic preferences based on a range of information from various sources, e.g. Health and Safety Executive (HSE), Environment Agency, Scottish Environmental Protection Agency (SEPA). We also engage with our Site Licence Companies (SLCs) and the nuclear supply chain to ensure our strategy has a sound basis.

SLCs will develop their own local D&CU strategies to achieve our mission. Current SLC Lifetime Plans embed many of the principles of decommissioning good practice.

Interfaces

The Decommissioning strategy interfaces with the majority of driving and enabling strategies. The key interfaces are discussed below:

• Land Quality Management strategy is related because Strategies for land quality management and decommissioning must be consistent.  For example, decommissioning may impact requirements for controlling and monitoring land contamination, and may risk (re)contaminating land.  Decommissioning may be required to access land that requires remediation.
• Site End States strategy is related because the character of facilities to be decommissioned will influence the selection of a practical and achievable site end state and date.  Conversely, the Site End State Strategy has implications for the extent of decommissioning required.
• All waste strategies are relevant because the approach to decommissioning is influenced strongly by the Waste Hierarchy and the products of decommissioning will be managed in accordance with our Integrated Waste Management Strategy. Conversely, the timing and method of decommissioning will influence our waste management requirements.  There are similar interfaces with the Nuclear Materials Topic Strategy for those decommissioning projects (plant clean out) that generate quantities of nuclear materials.
• Asset management strategy is related because it is essential to ensuring that the long-term net level of risk posed by our estate does not increase. 

Credible Options

At the highest level, credible options for decommissioning are:

• continuous decommissioning - decommissioning commences at the end of operations and continues until final demolition of the plant/facility/installation
• deferred decommissioning - decommissioning comprises one or more periods when the plant/ facility/ installation is purposely kept in a state of Care and Maintenance as part of the programme for achieving the Site End State.

There are two strategic sub-options for decommissioning: leaving parts of a facility in place and regarding them as disposed (in-situ) or removing them for disposal elsewhere (ex-situ).

Current Position

Both continuous and deferred decommissioning have been shown by the Strategic Environmental Assessment to offer long-term environmental benefits with continuous decommissioning potentially providing the greatest benefit. Where risk is the dominant relevant factor our priority will be to decommission continuously until the risk is at least tolerable. This risk management approach applies to Legacy Ponds and Silos at Sellafield which represent an intolerable risk for the estate and are therefore our top decommissioning priority.

We will manage the condition of our plants and facilities to ensure that currently tolerable risks do not increase to become intolerable and that all risks are kept As Low As Reasonably Practicable.

To reduce risk and hazard we will define and use Interim States. These are natural milestones and decision points in the site restoration programme that lead us towards achieving a Site End State. Decommissioning may give rise to Interim States where risk or hazard has been reduced to achieve a more stable condition.

The two strategic sub-options of in-situ or ex-situ decommissioning are both credible options.  The preferred option is case-specific, for example depending on the nature of the facility and the Site End State.