Magnox nuclear sites: strategic review of timing and sequence of reactor dismantling
Review of benefits of dismantling reactors at one or more Magnox nuclear sites on a shorter timescale than currently assumed.
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This document outlines the progress on our work to review the current baseline strategy for the timing of reactor dismantling.
Currently Magnox reactor dismantling is assumed to occur 85 years after the reactors have ceased generation; the work proposed in this strategy will determine whether there are any benefits from dismantling the reactors at one or more sites on a shorter timescale.
The current deferred dismantling strategy involves preparing each reactor for many decades of quiescence known as Care and Maintenance. As well as ensuring that the reactor is physically safe, preparations for quiescence must also put in place appropriate management arrangements including those required for site security, monitoring, maintenance and records management.
There are a number of drivers that support deferred reactor dismantling, which include:
- benefitting from radioactive decay, which could result in less complex dismantling techniques being used and changes in the categorisation of radioactive wastes
- avoiding the need for interim storage of reactor waste whilst a geological disposal facility is developed
- the substantial reduction with increasing deferral time of lifecycle costs on a discounted or Net Present Value (NPV) basis
There are however risks associated with such a lengthy deferral period:
- loss of skills, knowledge and capability to carry out final site clearance
- increased costs from the complexity of dismantling assets that have deteriorated over the years
- taking up land that could be used for other purposes
- uncertainty over future economic circumstances and regulatory standards
- even unpredictable developments arising from events such as financial crises, pandemics or wars
Whilst Magnox Ltd is making good progress in considering how to mitigate these risks, our strategic work in this area will take a fresh look at these drivers and risks associated with the deferred strategy. Our knowledge and understanding of nuclear decommissioning has moved on since the deferred decommissioning strategy was put in place, and changes in the decommissioning landscape make a review timely, such as:
- advances in remote decommissioning and waste handling techniques and international experience of reactor dismantling
- government policies on the long-term management of higher activity waste (HAW) aim to investigate alternative disposal options
- new waste routes have become available for the management of low level waste (LLW) to permitted landfill, for the recycling of metals, and for the interim storage of HAW
- increasingly, international bodies such as the International Atomic Energy Agency (IAEA) and the Nuclear Energy Agency (NEA) hold the view that reactor dismantling should be carried out as soon as possible, and have questioned the high weighting given to cost calculations on a discounted cost basis.
Prompted by these developments, the NDA has worked with Magnox Ltd to research the implications of alternative decommissioning strategies. The findings of this research support a review of the decommissioning strategy. Notably, an improved understanding of the radioactive inventory has shown us that, due to high inventories of long-lived radionuclides, the long period of quiescence will not result in a large scale re-categorisation of waste from intermediate level waste (ILW) to LLW.
Secondly, a preliminary high level cost model suggests that as the deferral time increases, the reduction in decommissioning costs (resulting from increased worker access) is largely offset by the increased cost of preparing for and managing quiescence. Furthermore, even after a significant period of deferral, it is likely that remote dismantling techniques would be applied to Magnox reactor dismantling as a matter of best practice to help minimise conventional safety risks and doses to workers.
On behalf of the NDA, over the next few years, Magnox Ltd will develop and evaluate credible options for the alternative timing of reactor dismantling. This will focus first on those sites for which the benefits of early reactor dismantling are particularly evident, for example sites with a high land value or sites likely to yield the greatest learning for other sites. There are a number of potential socio-economic benefits from earlier decommissioning and significant advantages associated with maintaining a strong knowledge base and skilled decommissioning workforce that will be considered within this review.